EPA 520/4-77-013
mmm
ASSESSMENT OF CARBON-14
CONTROL TECHNOLOGY AND COSTS
FOR THE LWR FUEL CYCLE
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
-------
This report was prepared as an account of work sponsored by the
Environmental Protection Agency of the United States Government under
Contract No. 68-01-1954. Neither the United States nor the United
States Environmental Protection Agency makes any warranty, express or
implied, or assumes any legal liability or responsibility for the accuracy,
completeness or usefulness of any information, apparatus, product or
process disclosed, or represents that its use would not infringe privately
owned rights.
-------
ASSESSMENT OF CARBON-14
CONTROL TECHNOLOGY AND
COSTS FOR THE LWR
FUEL CYCLE
Gary R. Bray
Charles L. Miller
Tien D. Nguyen
John W. Rieke
September 7, 1977
Final Report for Contract 68-01-1954
Prepared For
Environmental Protection Agency
Office of Radiation Programs
401 M Street, S.W.
Washington, D.C. 20460
-------
FOREWORD
The Office of Radiation Programs carries out a national program
designed to evaluate the exposure of man to ionizing and nonionizing
radiation, and to promote the development of controls necessary to
protect the public health and safety and assure environmental quality.
Office of Radiation Programs technical reports allow comprehensive
and rapid publishing of the results of intramural and contract projects.
The reports are distributed to groups who have known interests in this
type of information such as the Nuclear Regulatory Commission, the
Department of Energy, and State radiation control agencies. These reports
are also provided to the National Technical Information Service in order
that they may be readily available to the scientific community and to
the public.
Comments on this analysis as well as any new information would be
welcomed; they may be sent to the Director, Criteria and Standards
Division (AW-460), Office of Radiation Programs, U.S. Environmental
Protection Agency, Washington, D.C. 20460.
W. D. Rowe, Ph.D.
Deputy Assistant Administrator
for Radiation Programs
-------
TABLE OF CONTENTS
Section
1. INTRODUCTION
Chapter 1 References
2. PROJECTED CARBON-14 CONCENTRATIONS AND BEHAVIOR
IN THE VARIOUS LWR EFFLUENT TREATMENT SYSTEMS.... 2-1
2,1 Sources of carbon-14 in light water reactors 2-2
2.1.1 Annual production of carbon-14 in the
fuel of LWR's 2-4
2.1,2 Carbon-14 produced in BWR coolant.... 2-7
2.1.3 Carbon-14 produced in PWR coolant.... 2-7
2.2 Distribution of carbon-14 in the gaseous
release pathways of a light water reactor... 2-8
2.2.1 Concentration of carbon-14 and poten-
tial magnitude of releases from BWR
gaseous release pathways ............. 2-10
2.2,2 Concentration of carbon-14 and poten-
tial magnitude of releases from PWR
gaseous release pathways ............. 2-14
Chapter 2 References ............. ................ 2-20
3 . POSSIBLE C-14 CONTROL TECHNIQUES ................. 3-1
3 . 1 Scrubbing techniques ........................ 3-2
3.1.1 Gas absorption by wet scrubbing ...... 3-2
3.1.2 Caustic scrubbing by gas absorption.. 3-2
3.1.3 Ethanolamine scrubbing ............... 3-9
3 . 2 Other absorption techniques ................. 3-9
3.2.1 Lime bed absorption of CO- ........... 3-9
3.2.2 Absorption of carbon-14 dioxide in a
fluorocarbon solvent, dichlorodi-
f luoromethane ........................ 3-10
3 . 3 Adsorption techniques ....................... 3-15
3.3.1 Fixed bed adsorption of carbon dioxide
with molecular sieves ................ 3-16
-------
TABLE OF CONTENTS
Section Paqe
3.4 Control of carbon-14 using an integrated
cryogenic distillation technique 3-19
3.5 Summary 3-22
Chapter 3 References 3-24
4. MODIFIED LWR EFFLUENT TREATMENT SYSTEMS FOR THE
CAPTURE OF THE MAJORITY OF C-14 4-1
4.1 BWR off-gas C-14 treatment system 4-1
4.1.1 Caustic scrubber system 4-2
4.1.2 Fixed bed adsorption for C-14 contro!4-19
4.1.3 Fixed bed adsorption with caustic
scrubbing for C,. control 4-21
4.2 PWR off-gas C-14 treatment system 4-22
Chapter 4 References 4-34
5. DESIGN MODIFICATION TO NEW LWR FACILITIES FOR THE
CONTROL OF C-14 5-1
5.1 BWR design modifications 5-1
5 . 2 PWR design modifications 5-2
5.3 Reduction of carbon-14 by control of parent
elements 5-4
Chapter 5 References 5-6
6. CURRENT SPENT NUCLEAR FUEL REPROCESSING EFFLUENT
TREATMENT SYSTEMS 6-1
6.1 Process off-gas treatment..... 6-3
6.1.1 Process off-gas condensation 6-6
6.1.2 Removal of radioiodine from off-gas..6-6
6.1.2.1 Wet chemical scrubbing 6-7
6.1.2.2 Dry fixed-bed adsorption .... 6-7
6.1.2.3 lodox process 6-8
6.1.3 Removal of nitrogen oxides by wet
scrubbing 6-9
6.1.4 Cryogenic distillation for noble off-
gas treatment 6-10
6.1.4.1 Removal of noble gases by
cryogenic distillation 6-10
6.1.4.2 Application of cryogenic dis-
tillation to carbon dioxide
removal 6-12
11.
-------
TABLE OF CONTENTS
Section
6.1.5 Selective absorption of gaseous rad-
wastes into liquid dichlorodifluoro-
methane 6-13
6.2 Process liquid waste and liquid effluent 6-14
Chapter 6 References 6-16
7. PROJECTED CARBON-14 CONCENTRATIONS AND BEHAVIOR
IN NUCLEAR FUEL REPROCESSING EFFLUENT TREATMENT
SYSTEMS 7-1
7.1 Carbon-14 in arriving spent fuel 7-2
7.2 Carbon-14 and stable carbon in the process
pathways 7-2
Chapter 7 References 7-5
8. MODIFIED REPROCESSING PLANT EFFLUENT TREATMENT
SYSTEMS 8-1
8.1 Cost estimates for separation facility off-
gas treatment possibilities 8-1
8.2 Effect of integrated control technologies.... 8-10
Chapter 8 References 8-11
9 WASTE MANAGEMENT OPTIONS FOR CARBON-14 PRODUCT
FORMS 9-1
9.1 Introduction 9-1
9.2 Disposal 9-1
9. 3 C-14 product form and package 9-1
9. 4 BWR waste management 9-3
9.4.1 Waste volumes and cost calculations
for BWR's 9-3
9.4.2 Waste management cost summary for BWR
systems 9-8
9.5 PWR waste management 9-9
9.6 Spent LWR fuel reprocessing plant waste
management 9-10
Chapter 9 References 9-14
111.
-------
TABLE OF CONTENTS
Section Page
10. ECONOMIC COMPARISONS AND SUMMARY 10-1
APPENDICES : Nomenclature A-l
A. LWR SCRUBBER SYSTEM DESIGN B-l
B. REPROCESSING DISSOLVER OFF-GAS SYSTEM DESIGN
(CATEGORY I) B-l
C. REPROCESSING DISSOLVER OFF-GAS SYSTEM DESIGN
(CATEGORY II) C-l
IV.
-------
LIST OF TABLES
2-1 Production Sources of C in a Nominal 1000
MWe Light Water Reactor 2-9
2-2 Summary of Gaseous Carbon-14 Releases from BWR
Pathways 2-12
2-3 Summary of Gaseous Carbon-14 Releases from PWR
Pathways 2-18
4-1 Fabricated Equipment Costs for BWR C-14 Scrubbing
System 4-11
4-2 Personnel Requirements for Alternative Reactor
Staffing Plan (Figure 4-3) 4-17
4-3 Equipment List of Fixed Bed Adsorption of C02 4-20
4-4 Descriptions of Representative Retrofit Items 4-27
4-5 Cost Factors Directly Related to Retrofit 4-32
8-1 Fabricated Equipment Costs for Reprocessing Dissolver
Off-gas Scrubbing System (740 cfm) 8-4
8-2 Direct Equipment Costs for Reprocessing Dissolver
Off-gas Scrubbing System (100 cfm) 8-8
10-1 Summary and Comparison of Costs 10-3
LIST OF FIGURES
2-1 Gaseous Effluent Pathways with Flowrates and
Estimated Carbon-14 Releases for the Representative
BWR 2-13
2-2 Gaseous Effluent Pathways with Flowrates and
Estimated Carbon-14 Releases for the Representative
PWR 2-19
3-1 Flowsheet for a Caustic Scrubber to Remove C-14....3-4
3-2 Henry's Law Constant as a Function of Temperature
for Dichlorodifluoromethane (Freon-12) 3-13
v.
-------
LIST OF FIGURES (CONT.)
Page
3-3 C02 Removal Subsystem Piping and Instrumentation...3-17
4-1 Capital Cost Estimating Module Concept 4-9
4-2 Example of a Typical Reactor Staffing Plan 4-15
4-3 Example of Alternative Reactor Staffing Plan 4-16
4-4 An Example of Operator Costs 4-18
4-5 Davis Besse Nuclear Power Station Elevation 545....4-28
4-6 Davis Besse Nuclear Power Station Elevation 585....4-29
4-7 Typical Retrofit Schedule for a C-14 Control
System 4-33
6-1 Nuclear Fuel Reprocessing Flow Diagram 6-2
6-2 Reprocessing Facility Off-Gas Treatment Flow
Diagram 6-5
A-l Generalized PressureDrop Correlation for Sizing
Packed Towers A-3
VI.
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CHAPTER 1. INTRODUCTION
Under the President's Reorganization Plan No. 3 of 1970,
the Environmental Protection Agency was vested with respon-
sibility .for establishing environmental radiation standards.
In so doing, the Agency must address public health and
environmental concerns associated with the nuclear fuel cycle
as a whole. In order to establish the standards on a sound
basis, the following assessments must be made: comprehensive
determination of the releases of radioactive materials during
routine operation (planned releases) from all facilities
associated with nuclear power generation, potential effects
on the public and environment, minimization of these effects
through the issuance of standards, and the costs and tradeoffs
involved.
The impact of radioactive effluents have been considered from
three points of view:
the traditional measure of maximum radiation dose to
individuals
summation of individual annual doses to obtain a total
population dose (this is equivalent to summing indi-
vidual potential health effects under the assumption
of a zero threshold linear relationship between dose
and potential health effect)
"the environmental dose commitment"
The latter point of view came about as a result of the obser-
vation that certain nuclides have very long half lives and
so may deliver doses to populations for periods ranging from
decades to millenia as they migrate through the biosphere. (1)
The potential public health hazard of carbon-14 was highlighted
when accounts of environmental dose commitment were made.
1-1
-------
In response to the need for information relevant to quantitation
and mitigation of the hazard, preliminary and in-depth studies
have been made on the extent of carbon-14 production, environ-
mental release and dose commitment (2, 3). Remaining was a
need to review current waste processing in the nuclear fuel
cycle, propose treatment options and estimate costs for available
designs. The present report is an effort to incorporate current
knowledge of carbon-14 behavior in light water reactors and
fuel reprocessing plants into designs compatible with present
technology. This information is reflected in the economic
analyses presented in the final part of this study.
In summary, the purpose of this technical assessment is:
to provide a data base for analysis for control of
carbon-14 from LWR fuel cycle facilities
to provide the basic information needed to perform
a cost-effectiveness analysis for control of carbon-14
in the LWR fuel cycle
to be an aid to the Environmental Protection Agency
in establishing effluent discharge limits for carbon-
14 and in reviewing environmental impact statements
Available literature on quantities and pathways of carbon-14
in fuel cycle facilities has been reviewed to analyze the
behavior of this nuclide. In general, it was shown that
very little carbon-14 probably remained in liquid effluent
systems, so this report is much more specific to gaseous
behavior and treatment; liquid cases are considered if they
represent an appreciable contribution to environmental con-
tamination. Treatment principles and devices have been re-
viewed and reasonable alternatives chosen. These choices
have been analyzed according to conclusions regarding
behavior of the nuclide and any stable carrier substances.
Designs are proposed for treatment systems and waste
1-2
-------
management options considered. Finally, an economic
analysis is provided and system reliability commented
upon. Judgements regarding integration of various
treatment and waste management alternatives are provided
throughout the report. The latter task is subject to
great variations as conditions of licensing, power
generation and technology change, so these judgements
are not to be construed as final.
1-3
-------
Chapter 1 References
1. Environmental Radiation Dose Commitment; An Application
to the Nuclear Power Industry, EPA-520/4-73-002f~~
U.S. Environmental Protection Agency, February 1974.
2. Magno, P.J., C.B. Nelson and W.H. Ellett. "A
consideration of the significance of carbon-14 discharges
from the nuclear power industry". Proceedings of the
Thirteenth AEC Air Cleaning Conference, 1975.
3. Fowler, T.W., R.L. Clark. J.M. Gruhlke and J.L. Russell.
Public Health Considerations of Carbon-14 Discharges
from the Light-Water-Cooled Nuclear Power Reactor Industry,
Technology Assessment Division, Office of Radiation
Programs, United States Environmental Protection Agency,
ORP/TAD-76-3, July, 1976.
1-4
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CHAPTER 2. PROJECTED CARBON-14 CONCENTRATIONS
AND BEHAVIOR IN THE VARIOUS LWR
EFFLUENT TREATMENT SYSTEMS
An analysis has been undertaken to estimate carbon-14 con-
centrations and chemical forms expected in the boiling and
pressurized water varieties of light water reactor. This
information will be used in design of effluent control
systems. Knowledge of distribution and quantity of re-
leases from the several pathways which carry carbon-14 to
the environment allows the designer to choose cost-effective
treatment principles and devices.
Deferring to design criteria established prior to and in-
dependently of this discussion, all carbon-14 produced in
the reactor and released at the site will be assumed to
exist in only physical and chemically bound state at the time
it is removed. The chemical form of C-14 in release path-
ways varies, but minimum cost and technical ease dictate
that most bound carbon, regardless of the state or states
it passes through prior to treatment, shall be oxidized to
CO- for extraction. Therefore, the prior forms of bound
carbon-14 are important only as they would yield to ready or
awkward conversion to CO-. Conceivable forms of bound car-
bon in the coolant of a light water reactor are CO (gas),
CO- (gas), and light hydrocarbons such as methane, ethane,
(47)
propane and possibly butane. Kunz ' ' reports the former
two bound forms predominate in BWR's, while the latter are
most significant in the PWR. The hydrocarbons are easily
converted to an oxidized form.
The magnitudes of radioactive carbon source terms and their
distribution among release pathways are the primary objects
2-1
-------
of this analysis. Literature pertaining to C-14 production
in and release from reactors and spent fuel reprocessing
plants, such as the paper by Magno, et al, of the Environ-
mental Protection Agency,(9)was reviewed. It acknowledges
that specific data and analyses are scarce. Therefore,
sources for this discussion are quite recent analyses of-
fered by researchers and regulatory agencies.^1~8^ Some of
the data were taken from operating experience and experi-
ments at reactor facilities, though many of the results have
been deduced from design conditions and indirect measure-
ments. In addition, a standardized reactor size was- used in
this analysis, so all final values must be considered
estimates of the radioactive carbon source terms. These
estimates have been found very adequate as design data used
in later stages of this study where approximate ranges and
costs of control are established.
2.1 Sources of carbon-14 in light water reactors
This section discusses radioactive carbon sources common to
both types of light water reactor. A common element of the
two is the fuel rod, where the processes of nuclear fission
and decay initiate production of carbon-14 in excess of its
natural concentration. Direct observation of C-14 pro-
duction rates in the fuel and fuel rod gap is experi-
mentally impracticable, so reasonably accurate calculations
are used to estimate the source terms. This analysis of the
source terms relies upon, and follows quite closely, the
work of Fowler, et al. provided in an Environmental
(8)
Protection Agency (EPA) technical note. Every effort
has been made to use the results of the EPA study so this
Technical Assessment r.ight play a sequential role in any
discussion of the extent, ramifications and mitigation of
carbon-14 releases to the environment.
2-2
-------
Neutron activation of other light elements is the principal
mechanism by which natural and man-made carbon-14 come to
exist. The contribution of carbon-14 from fission of reactor
235 6
fuel is negligible ( U fission yield is 1.7x10 ). The
type of absorption and subsequent decay are factors, along
with the nature of reactants and reaction medium, determin-
ing the chemical form newly created carbon-14 assumes.
Following are nuclear reactions which can form the isotope
in a LWR, listed with their respective thermal neutron re-
action cross sections (a.):
Reaction Importance a. (barns)
14N(n, p)14C Primary 1.81
170(n, a)14C Primary 0.24
13C(n, Y)14C Secondary 0.0009
15N(n, d)14C Secondary 2.4xlO~7
14 17
Only the N and 0 reactions occur with great enough fre-
quency to warrant consideration as sources.
There are two types of light water reactor and numerous
individual units of each category. Each unit differs in
size, control mechanism, and cooling subsystems, so some
"average" is required for a generic discussion. There are
several common features with respect to fuel. After the
original core loading, assumed to be approximately 100 metric
tons heavy metal (MTHM), it is assumed that one third of the
fuel is removed and replaced each year in the manner custom-
ary during the equilibrium cycle. Therefore, the activation
equation assumes 33.5 MTHM of fuel is irradiated for three
years at a burnup of 33,000 MWt-days per MTHM and 33 percent
thermal efficiency. This combination of burnup, fuel mass
2-3
-------
and efficiency result in one GWe produced in a year, the
amount of electrical energy produced by our "average"
unit of 1,250 MWe operating at an 80 percent capacity
factor. These assumptions are believed to conservatively
account for fuel conditions experienced in reactor designs.
The neutron flux in both reactor types is assumed to be
TO -2 -1
5x10 neutrons-cm -sec in the fuel and coolant. All
thermal neutron reaction cross sections are multiplied by
the factor 0.6 to account for 1/v variation of the two
cross sections of interest. It provides a conservative
bounding factor which prevents high values if the neutron
energy distribution is not exactly thermal.
2.1.1 Annual production of carbon-14 in the fuel of LWR's
Now the activity of carbon-14 produced in the fuel elements
of the "average" reactor may be calculated. Two reactions,
N(n, p) C and 0(n, a) C, are to be considered. In
general, the activity produced due to neutron activation is:
A =
(2)
where the first term on the right side of equation (1) de
scribes growth of the product element, the second term de
scribes the product's decay and
A = activity produced, disintegrations sec"1
f = fractional isotopic abundance of target element
L = Avogadro's number, 6.025 x 10 mole"1
2-4
-------
a = reaction thermal neutron cross section, barns
-24 2
(10 cm )
-2 -1
= local neutron flux, neutrons "cm «sec
X^ = decay constant of product nuclide
tj_rr = irradiation time
N = number of target element atoms
m = mass of target element, grams
M = atomic weight of target element, g*gram-mole
For the reaction 0(n, a) C the following data apply:
f = 3.7 x 10~4
m = 4.5 x 10 grams of oxygen (all isotopes)
[Note: in 33.5 MTHM of fuel, approximately 4.5 MT
are oxygen]
M = 17 grams»- -mole
a = 0.24 x 10 ~24 cm2
13 -2 -1
<|> = 5 x 10 neutrons-cm -sec
, 0.693 , _, .. -4 -1
Xd - 5,730 years = 1«21 x 10
tirr = 3 years
Therefore,
A (3.7x!0"4)H.5xl06 g/GWe yr)(6.025xlQ23 mole"1)(5xlQ13cm"2-sec"1)
=
(17 g-mole )
O/l ^
x C0.24xlO~ cm ) CO. 6) (1 - exp.f^(a.>21xlQ4"> (3) 1
(3.7 x 1010 ''
A = 4.1 Ci/GWe-yr for the oxygen-17 reaction.
2-5
-------
The activity produced in the activation of N-14 can be cal-
culated in a similar fashion. The mass of nitrogen present
is variable as it is a fuel impurity, and may be as high as
220 ppm. Rarely is the fraction greater than 20 ppm, which
has been used for this calculation, and 20 ppm corresponds
to about 756 g of nitrogen. Again, the data are listed:
f = 0.99635
m = 7.56. grams of nitrogen
M = 14 grams mole
a = 1.81 x 10~24 cm2
13 -2 -1
4> = 5 x 10 neutrons -cm -sec
6 '
d 5,730years '
tirr = 3 years
Therefore,
,_ CO. 99635X7. 56xlQ2g/GWe- yr) (6.025xlQ23 mole"1) (5xlQ13cm"2 -sec"1)
A~ -1
(14 g-mole )
x (l.Slxlo"24 cm2) CO. 6) (1 - expl-(.1.21xlo"4yr"1) C3 yr)])
(3.7 x 1010 "
A = 17.3 Ci/GWe-yr for the nitrogen-14 reaction.
To summarize, carbon-14 is produced in the fuel by the two
pathways at the approximate rate of 4.1 Ci/GWe-yr by the
17 14
0 reaction and 17.3 Ci/GWe-yr by the N reaction.
2-6
-------
2.1.2 Carbon-14 produced in BWR coolant
The coolant of a light water reactor is exposed to neutron
irradiation from the fuel elements. Water used for coolant
is highly purified, though some residues remain dissolved
or suspended which are subject to activation. Neutron ab-
sorption by 0-17 bound as water should still predominate,
however, because of the high target element concentration.
A representative General Electric BWR/6 contains 1,872 ft
of water pressurized to 1,062 psia and maintained at a tem-
perature of 540°F. At these conditions, the water mass is
39.5 MT. The BWR/6 operates at a power level of 3,579 MWt,
or an annual electric power output of 1.18 GWe. For this
power level and water mass, carbon-14 is produced via the
17 14
0(n, a) C reaction at the rate of 9.2 Ci/GWe-yr in
the coolant.
No data was available on nitrogen concentration in the
coolant of a BWR. The activity produced by a nominal
1 ppm of nitrogen is approximately 0.26 Ci/GWe-yr. It
was concluded that this term be used awaiting more concrete
data.
2.1.3 Carbon-14 produced in PWR coolant
The volume of coolant in a representative PWR 03,473 MWt,
or 1.146 GWe at 33 percent thermal efficiency) was esti-
mated from the core height of active fuel and cross section-
al flow area of the-core. A water mass of 13.7 MT was cal-
culated from the specific volume at saturation conditions,
588°F. and under 2,235 psia pressure. The coolant is not
saturated in the core, so the result may be somewhat low,
2-7
-------
though not greatly so. For these conditions, carbon-14
activity arising from the O(n, a) C reaction is pro-
duced at the rate of 3.3 Ci/GWe-yr.
Carbon-14 activity in the PWR coolant arising from N-14
neutron activation must be estimated as in Section 2.1.1.2.
Data are not available on concentrations of nitrogen from
air or control compounds, so a nominal value of 1 ppm was
used. What results is a production rate of 0.09 Ci/GWe-yr.
All the results accrued in Section 2.1.1 are tabulated in
Table 2-1.
2.2 Distribution of carbon-14 in the gaseous release
pathways of a light water reactor
Carbon-14 is produced in the fuel and coolant and distri-
buted wherever gas or fluid streams flow in the plant.
Leakage of plant systems allows for eventual release to
the environment, so the partitioning of original carbon-14
in various pathways is an important guide to the establish-
ment of control measures.
Radioactive carbon will always be carried by stable carbon
compounds. In boiling water reactors, much of the air
entrained in the coolant is ejected from the main conden-
ser overhead. This off-gas stream is fundamentally air
and therefore carbon, as carbon dioxide, exists in
approximately the same ratio to other constituents as it
does in air. A very small amount of the stable carbon
remains in the coolant; this level is probably regulated
by chemical control. In a PWR, some CO- remains in
solution as carbonic acid, while most leaks to an air space or
2-8
-------
Table 2-1
14
Production Sources of C
in a Nominal 1000 MWe Light Water Reactor
Source
Reaction
Production
Rate
(Ci/GWe-yr)
Total
(Ci/GWe-yr)
Fuel
170(n, ct)14C CO. 037% abundance)
14N(n, p)14C (20
4.1
17.3
21.4
BWR Coolant 170(n, ct)l4C C38.9 MT oxygen)
14N(n, p)14C Cl ppm)
9.2
.26
9.5
PWR Coolant 170(n, a)14C (11.5 MT oxygen)
14N(n, p)14c Cl ppm)
3.3
0.09
3.4
2-9
-------
to the chemical control system where it is diluted in
nitrogen. Dilution in the off-gas streams is great
enough to assure an air-like composition with respect
to CO-. Due to boric acid addition and buffering, a
minor amount of CO- is expected to remain in the primary
coolant. Corrosion control for the secondary system
probably maintains a low CO,, level, causing most to be
released as gas in the air-ejector. Most critical, of
course, are the stable carbon dioxide concentrations at
the treatment point. These are provided where required in
this chapter, Chapters 3 and 4 and the appendices.
2.2.1 Concentration of carbon-14 and potential magnitude
of releases from BWR gaseous release pathways
The following systems have been considered as release
pathways for gaseous carbon-14, and an effort has been
made to estimate the magnitude of releases:
condenser steam jet air ejector (SJAE)
turbine gland seal condenser exhaust
reactor building [including drywell) purge exhaust
turbine building ventilation system exhaust
radwaste building ventilation system exhaust
The concentration of stable carbon dioxide, compared on the
basis of dry portions of vapor passing through these routes,
is taken to be equivalent to that in air.
A cross-section of measured concentrations has been used when
available. When these are lacking, the average carbon-14
concentration in the reactor coolant at Oyster Creek was uti-
lized in conjunction with standard assumptions.^1~3^
Measurements at Oyster Creek indicate the gaseous releases
2-10
-------
of carbon-14 are a mixture of CO- and, presumably, organics. At
the major release points, CO dominates by at least two to
one. -The condenser steam-jet air ejector appears to be the
most significant release point. Preliminary data from the
Oyster Creek study ' indicate an average C-14 release
rate of 0.182 yCi/sec. On an annual basis, for a 1,250 MWe
BWR operating at an 80 percent capacity factor, 9.0 Ci/yr
is the estimated release. In a similar fashion, the re-
lease rate from the turbine gland seal condenser exhaust
is estimated to be less than 0.015 Ci/yr. The latter fig-
ure is based on a measured release rate at Oyster Creek of
<3xlO~4 yCi/sec.
The latter three pathways must be calculated using measured
coolant activities and leakage rates. The conservative
assumption is made that all this leakage vaporizes and es-
capes to the building atmospheres. It is further assumed
that the reactor and turbine building leakage is at 100
percent RCS activity, while that in the radwaste building
contains only 1 percent of the RCS activity. The coolant
concentration of carbon-14 at Oyster Creek is, on the
average, 4.0 pCi/ml. Leakage rates are 500 Ib/hr, 1,700
Ib/hr and 1,000 gpd for the reactor building, turbine
building and radwaste building, respectively. Resulting.
-2 -2 -5
values are 1.1x10 , 3.8x10 and 5.5x10 Ci/yr for the
reactor building purge exhaust, turbine building ventila-
tion system exhaust and radwaste building ventilation
system exhaust, respectively.
Results of Section 2.2.1 are tabulated in Table 2-2 and
shown schematically in Figure 2-1.
2-11
-------
Table 2-2
Summary of Gaseous Carbon-14 Releases from BWR Pathways
Pathway
Annual 14C
Release
CCi/yr)
Percent of
Total
Condenser Steam-Jet Air
Ejector -Off-gas
Turbine Gland Seal
Condenser Exhaust
9.0
0.015
99.3
0.2
Reactor Building Purge Exhaust
Turbine Building Ventilation
Radwaste Building Ventilation
0.011
0.038
5.5 x 10
9.1
-5
0.1
0.4
2-12
-------
to
SOURCE
GASEOUS DISCHARGE
FLOMRATE (SCFM)
ESTIMATED 14C
RELEASE RATE
(C1/YR)
RADUASTE BUILDING REACTOR BUILDING TURBINE BLDG.
VENT PURGE EXHAUST VENT it:'
50 000 l°6 Fl3> FOUR
' TIjMES ANNUALLY
5.5 X 10 5 0.011
t 1
1 1
1 1
|Je| |Jo|
RADUASTE
BUILDING
1
WASTE SYSTEMS
REACTOR
BUILDING
f V,
r ( REACTOR )
\. X
" /~|
DEMINERALIZER M
500,000
0.038
T
|J<=»|
TURBINE BUILDING
r
i
TURBINE
CONDENSER
-------
2.2.2 Concentration of carbon-14 and potential magnitude
of releases from PWR gaseous release pathways
The following systems have been considered as release path-
ways for gaseous carbon-14, and an effort has been made to
estimate the magnitude of releases:
primary off-gas treatment vents (in normal
and shutdown operations)
condenser steam-jet air ejector (SJAE)
steam generator blowdown tank vent exhaust
turbine gland seal condenser exhaust
fuel handling building ventilation exhaust
containment ventilation system exhaust
auxiliary building ventilation system exhaust
turbine building ventilation system exhaust.
The concentration of stable carbon dioxide, where it is
the dominant carbon compound in a pathway, compared on the
basis of dry portions of vapor, is taken to be equivalent
to that in air. Measurements of stable hydrocarbon concen-
trations, when hydrocarbon compounds dominate, are discussed
below; in present form these data do not, in conjunction
with standard assumptions, yield results having adequate
certainty.
Once again an attempt has been made to use measured concen-
trations. When they are lacking, the average reactor
coolant concentration of a representative PWR facility is
used in conjunction with standard assumptions.
The chemical form of carbon-14 is different in releases
from PWR's than one finds at BWR's. It was discovered
that primary system off-gases emanating from the gaseous
radwaste treatment system at Haddam Neck are virtually all
in non-C02 form. The C02 fraction of carbon releases
2-14
-------
from the condenser SJAE is similarly small, less than 15
percent at Haddam Neck. Analysis performed for the
Ginna PWR indicates nearly 90 percent of the gaseous rad-
waste system carbon-bearing off-gases are methane or
(4 \
ethane, whereas only 5 percent are CO--
The most significant element contributing to carbon-14
releases is the off-gas stream from the primary gaseous
radwaste treatment system. Flow and concentration data
were studied to arrive at representative values which
were in turn scaled to 1,250 MWe plant capacity if neces-
sary. An average of waste gas decay tank carbon-14 con-
centrations, taken from Ginna, Haddam Neck, and Yankee
Rowe and ~<4'5'6) was found to be 5x10~ yCi/cm . Flow esti-
mates range from 0.1 to 1.0 scfm in the off-gas system,
supported by operating data for San Onofre 1, among
others. That 430 MWe reactor processed 30,000 ft in
three months, which corresponds to 350,000 ft /yr for a
1,250 MWe plant. The scaled process rate from San Onofre,
0.66 scfm, generally supports an averaged flow of 0.5 scfm
for the source term calculation. Resulting is an annual
release rate of 3.0 Ci/yr from the gaseous radwaste system
exhaust. Recall that all values reflect an 80 percent
capacity factor.
Releases from the condenser steam-jet ejector exhaust are
computed in a similar way. An average effluent concen-
tration from Haddam Neck and Yankee Rowe was found to be
-7 3
3.7x10 uCi/cm . Assuming 80 percent capacity factor in
a 1,250 MWe PWR and a condenser SJAE flowrate of 25 scfm,
one arrives at 0.11 Ci/yr projected release rate.
An estimate of steam generator blowdown tank (SGBT) ef-
fluent release rate was calculated with steam generator
2-15
-------
carbon-14 concentration data from Haddam Neck, 1.6xlO~7
yCi/ml. Other conditions at that station include 5 gpm
total blowdown flowrate, liquid flashing in the SGBT of 35
percent, and a further assumption that carbon-14 partitions
in the same fraction as steam in the tank. ' A release
-4
rate of 4.5x10 Ci/yr is predicted.
A conservative estimate for turbine gland seal condenser
venting of carbon-14 must be made for want of operational
data. It is assumed that 100 percent of the carbon-14
dissolved in the 50 gpd primary-to-secondary leakage
partitions to the vapor phase and that 0.1 percent of the
vapor phase (i.e., the main steam flow) is routed to the
-gland seal. Again, the average primary coolant concen-
tration of C-14, observed at Haddam Neck and Yankee Rowe,
is 1.67xlO~ yCi/ml. When these values are used to cal-
culate the annual release rate of carbon-14 from the tur-
bine gland seal condenser off-gas vent is 9.2x10 Ci/yr.
Th i concentration of carbon-14 in the Connecticut Yankee
(Haddam Neck) plant's fuel handling building atmosphere
was measured at 9x10 yCi/cm of air. Using the operating
ventilation rate of 70m /min on a continuous basis, the
estimated release is 0.69 Ci/yr. Here again, the release
rate was scaled to 1,250 MWe and an 80 percent capacity
factor was assumed.
Measurements at the Ginna power station indicate a contain-
ment atmosphere carbon-14 concentration of 1.5xlO~
yCi/cm of air during operation. The containment volume,
assumed to be one million cubic feet, is purged four times
annually. Consequently, it is estimated that 0.52 Ci/yr
of carbon-14 is released from a 1,250 MWe PWR operating
at an 80 percent capacity factor.
2-16
-------
Calculations for the auxiliary building discharge rate
based on measurements such as those taken at Haddam Neck
are generally thought to be high for the reason that
measured C-14 atmospheric concentrations are below the
9 3
detection limit for C-14 in air, 6.0x10 yCi/cm . A
reasonable alternative is to use the "standard" leak rate
of primary coolant to the auxiliary building, equal to 20
gpd cold and 1 gpd hot, in concert with other system para-
meters to compute an estimate. Using the primary coolant
C-14 average concentration of 1.67x10 yCi/ml, auxiliary
building ventilation releases are estimated to be
8.0xlO~4 Ci/yr.
Considerable uncertainty exists in some methods of esti-
mating turbine building releases. The one utilizing a
measured atmospheric concentration is most suspect because
the value approaches the carbon-14-iri-air detection limit.
Other methods agree fairly well, so the one which yields
conservative and reasonable results was chosen.for this
estimate. Secondary coolant in the steam generator of
Connecticut Yankee has an average C-14 concentration of
1.6x10 yCi/ml. The secondary coolant is further assumed
to leak to the turbine building at a "standard" rate of
1,700 Ib/hr. At an 80 percent capacity factor in the
nominal 1,250 MWe plant, an annual discharge rate esti-
mate is 1.8x10 Ci/yr.
Results.of Section 2.2.2 are tabulated in Table 3-3 and
shown schematically in Figure 2-2.
2-17
-------
Table 2-3
Summary of Gaseous Carbon-14 Releases from PWR Pathways
Pathway
Annual C
Release
CCi/yr)
Percent
of Total
Gaseous Radwaste Treatment System
Condenser Steam-Jet Air Ejector
Off-gas Vent
Steam Generator Slowdown Tank
Vent
Turbine Gland Seal Condenser
Exhaust
Fuel Handling Building Ventilation
Containment Building Purge Exhaust
Auxiliary Building Ventilation
Turbine Building Ventilation
TOTAL
3.0
0.11
69
4.5 x 10
-4
9.2 x 10
-7
2.5
0.01
8.0
1.8
0
0
x
x
.69
.52
io-4
io-3
16
12
0.
0.
02
04
4.32
2-18
-------
SOURCE
ASEOVS DISCHARGE
FLOKRATE (SCFN)
ESTIMATED 14C
RELEASE RATE
(Ct/YR)
K)
1
I-1
SIfn!!nnuMET^NVR GASEOUS RADWASTE CONTAINMENT BLDG. AUXILIARY BLDG. FUEL HANDLING BLDG. TURBINE BLDG. CONDENSER AIR TURBINE GLAND SEAL
BUMUUHI^IMW TREATMENT SYSTEM PURGE EXHAUST VENT VENT VENT ' EJECTOR CONDENSER fXHAittT
1,200 0.5 TIMESTANNUALLY 121,000 2470 100.000 25 500
4.5 X 10"4 3.0 0,S2 8.0 X 10"4 0.69 1.8 X 10"3 0.11 3.Z X 10"'
( ( ,
cL,
1
/CONTAINMENT \
/ BUILDING '
PRESSUR-
IZER
I
REACTOR
" iENERATOR ,-,
J5GW
Ju,
1 ! * * *
\i
i
AUXILIARY p"^| |"~|
UUILUlrlli TURBINE BUILDING I
CASEOUS 8UUOING r TURBINE
I RAC'n'ASTE
"^"" 1 rniinruvD I _ _
n^ i j
L,
r
_ O _ _ _1
r
1 - ~ ~ bUBT*
SGBT - STEAM GENERATOR SLOWDOWN TANK
GASEOUS STREAM
PRIMARY COOLANT (LIQUID STREAM)
SECONDARY COOLANT (LIQUID STREAM)
Figure 2-2. Gaseous Effluent Pathways with Flowrates and Estimated
Carbon-14 Releases for the Representative PWR
-------
Chapter 2 References
Blanchard, R. L., W. L. Brinck, H. E. Kolde, et al.,
"Radiological Surveillance Studies at the Oyster
Creek BWR Nuclear Generating Station", U.S. Environ-
mental Protection Agency, Office of Radiation Programs,
EERF, RNEB, Cincinnati, Ohio 45268 (June 1976).
I1. AttachFent to Concluding Statement of Position of
the Regulatory Staff, Public Rulemaking Hearing on:
Numerial Guides for Design Objectives and Limiting
Conditions for Operation to Meet the Criterion "As
LovT As Practicable" for Radioactive Material in fZght
Water Cooled Nuclear Power Reactors, Draft Regulatory
Guides for Implementation, Docket No. RM-50-2,
February 20, 1974, U. S. Atomic Energy Commission,
Washington, D. C. 20545.
3. Head, R. A., Miller, C. W., Oesterle, J. E., "Releases
from BWR Radwaste Management Systems", Licensing
Topical Report, NEDO-10951, July 1973, General Electric
Company, San Jose, California 95114.
4. Kunz, C., Mahoney, W. E., and Miller, T. W., "C-14
Gaseous Effluent from Pressurized Water Reactors",
Proceedings of the 8th Midyear Topical Symposium of
the Health Physics Society, October 1974.
5. Kahn, B. , et al., "Radiological Surveillance Study at
the Haddam Neck PWR Nuclear Power Station", EPA-520/
2-74-007, U. S. Environmental Protection Agency, Office
of Radiation Programs, Radiochemistry and Nuclear
Engineering Facility, National Environmental Research
Center, Cincinnati, Ohio 45268 (Final draft:
December 1974).
6. Kahn, B., et al., "Radiological Surveillance Studies
at a Pressurized Water Nuclear Power Reactor", RD 71-1,
U. S. Environmental Protection Agency, Radiochemistry
and Nuclear Engineering Branch, National Environ-
mental Research Center, Cincinnati, Ohio 45268
(August 1971) .
7. Kunz, C. 0., Mahoney, W. E., and Miller, T. W., " C
Gaseous Effluent from Boiling Water Reactors". Pre-
sented to the Annual Meeting of the American Nuclear
Society, New Orleans, Louisiana, June 8-13, 1975.
2-20
-------
8. Fowler, T. W., R. L. Clark, J. M. Gruhlke and J. L.
Russell. Public Health Considerations of Carbon-14
Discharges from the Light-Water-Cooled Nuclear Power
Reactor Industry, Technology Assessment Division,
Office of Radiation Programs, United States Environ-
mental Protection Agency, ORP/TAD-76-3, July, 1976.
9. Magno, P. J., C. B. Nelson and W. H. Ellett. "A
consideration of the significance of carbon-14 dis-
charges from the nuclear power industry". Proceedings
of the Thirteenth AEC Air Cleaning Conference, 1975.
2-21
-------
CHAPTER 3. POSSIBLE C-14 CONTROL TECHNIQUES
Carbon dioxide is a gas that serves several commercial
purposes: refrigerant, fire-extinguishing material, and
intermediate for the manufacture of other chemicals. Be-
cause of the diverse industrial need for carbon dioxide,
there are several techniques available for its collection
and packaging. Selection of a specific process for the
capture and retention of CO- depends on the volume of gas
to be treated, the concentration in the gas stream, the
composition of the gas stream, and the desired final
packaged form.
Experience has shown that off-gas streams from nuclear power
and reprocessing operations which may require carbon-14
treatment have approximately the same C02 concentration as
that found in air. Re
the following composition:
that found in air. Reference (dry) air has approximately
% by Volume
Oxygen 20.95
Nitrogen 78.08
Carbon Dioxide 0.03
Argon, etc. 0.94
The average molecular weight of air is 28.97 Ibs/lb-mole.
Several processes which may have direct application to
removal of carbon-14 from various reactor off-gas streams
have been examined. Included in the examination were
processes that have been designed specifically for noble
gas removal. The nature and feasibility of each process
is discussed in the following sections.
3-1
-------
3.1 Scrubbing techniques
Scrubbing is a popular commercial method for the removal
of one or more constituents from a gaseous stream. It in-
volves absorbing the gaseous constituent that is desired
to be removed into a liquid stream by passing the gaseous
stream through the liquid.
Three scrubbing processes which allow for the removal of
CO,, from an air stream are scrubb
caustic solution or ethanolamine.
C02 from an air stream are scrubbing with water, aqueous
3.1.1 Gas absorption by wet scrubbing
Carbon dioxide can be removed from an air stream by con-
tacting the stream with water in a -counter-current flow
fashion using a packed absorption column. The process de-
pends on normal gas absorption principles.
By studying the solubility of CCU in water in conjunction
with the design procedure for packed towers, it was found
that a tower of several hundred feet was needed to attain
almost complete removal of the CC>2, which would be highly
impractical. Space limitations in nuclear power plants and
reprocessing facilities preclude this method. The attractive-
ness of such a system is further diminished because the
final product (i.e., carbonic acid solution) would be in
a liquid form which is unacceptable packaging for permanent
isolation. Therefore, this process is not technically
feasible for the desired application.
3.1.2 Caustic scrubbing by gas absorption
Absorption of CC>2 by scrubbing with a caustic aqueous solu-
tion is a familiar industrial process. Considerable atten-
tion is given in this section to caustic scrubbing as it
3-2
-------
represents the most probable candidate for actual application.
Figure 3-1 is a flowsheet for a possible caustic scrubbing
absorption system. The gas stream to be treated is passed
through a blower and then introduced into a packed caustic
absorption column. Carbon dioxide is stripped from the gas
stream by the following chemical reaction:
2 NaOH + C02Na2C03 + H20
The bulk of the gas feed stream exists through the top of the
column. It is filtered by at least one stage of roughing filters
and one stage of HEPA filters before being released to the
environment.
The scrubbing solution from the absorber column is batched in
small lots to the mix tank when the desired conversion of CO- to
Na-CO, has been reached. Calcium hydroxide is then added to the
mixture causing the carbonate to precipitate as calcium carbonate:
Na2 C03 + Ca(OH)22 NaOH + CaC03
The amount of Ca^OH)- used to precipitate -the CaCO, may have to
be metered very carefully to avoid any excess which would cause
saturation of the filtrate with Ca(OH)2 (solubility is 2g/l)
which in turn would react in the packed tower to form CaC03 which
could plug the packing. Therefore, a direct caustic scrubber
process using Ca(OH)2 as the scrubbing agent may not be feasible.
The solution and precipitate are then pumped from the mix tank
and filtered. The sodium hydroxide filtrate is cycled back to
the absorber column, while the calcium carbonate cake is re-
moved by the filter and packaged for final disposal as solid
radwaste by incorporation into concrete.
The most important design aspect of caustic scrubbing
systems is the sizing of the absorption column that will
3-3
-------
WATER
L
TO ENVIRONMENT
ABSORBER
COLUFN
FROM
OF-GAS'
SYSTEM BLOWER
FILTERS
LO
I
.£>
>
SODIUM HYDROXIDE
-NADH
FILTER
PERIODIC
SAf'PLER
CIRCULATING
PUMP
FILTER
TO LIQUID
RAD-WASTE SYS1
CALCIUM
HYDROXIDE
CA (OH)2
CEMTf-
CAC03
CAKE
i i
l^ATER (OR LIQUID RAD-WASTE)
CONCRETE
INCORPORATION
Figure .3-1 . Flowsheet for a caustic
scrubber to remove C-14
-------
scrub the gas with sodium hydroxide. Design parameters
for a gas absorption column include:
1) Gas flow rate and composition
2) Operating pressure and pressure drop across
the absorber
3) Desired degree of recovery
4) Liquid flow rate
5) Operating temperature
6) Type of packing
The aqueous sodium hydroxide flow rate depends in each
individual case on the desired air flow rate. The
operating pressure of the absorber column will be main-
tained as close to atmospheric pressure as possible. The
pressure drop across a packed column 'is a function of both
liquid and air mass velocities. The limiting through-put
factor of a caustic absorption tower is usually a flow
condition that results in either foaming or flooding.
Reference 1 provides empirical relationships between a
scrubber solution that can be expected to cause foaming
and ranges of both liquid and gas flow rates. A refernece
design point obtained from these relationships is that an
2
air mass velocity of 300 Ibs/hour-ft of column cross
section can be passed through a packed column with a pres-
sure drop of 0.5 inches of water per foot of packing height
without causing major foaming problems. Flooding will
occur in an absorber column containing a given packing and
being irrigated with a definite flow of liquid if the gas
flow rate exceeds some upper limit. The gas velocity
corresponding to this limit is called the flooding velocity,
The upper limit can be found from an inspection of the
relation between the pressure drop through the bed of
packing and the gas flow rate, from observation of the
3-5
-------
holdup of liquid, and by the visual appearance of the
packing. The flooding velocity varies somewhat with the
method of determination and appears more as a range of
flow rates than as a sharply-defined constant. Reference
1 also provides empirical relationships between flow rates
and pressure drops that indicate flooding conditions. Ex-
perience has shown that the most economical designs for
caustic scrubbers utilize gas flow rates that are about
(4)
50-75 percent of flooding rates, and pressure drops
between .25 and .5 in. fO per foot of packing.
Selection of the proper type of packing for the desired
gas absorption operation is very important. The prin-
cipal requirements of a column packing are:
1) The packing should be chemically inert to
the fluids in the column.
2) It must be strong and durable but without
excessive weight.
3) The packing should contain adequate passages
for both streams without excessive liquid
holdup or pressure drop.
4) It must provide good contact between liquid
and gas.
5) The cost of the packing must be reasonable.
Ceramic saddles or rings of about an inch in size provide
the requirements for packing in a caustic scrubbing ab-
sorber column.
Another requirement of economical absorber column design
is that adequate distribution of liquid and gas be main-
tained throughout the packed section of the column. The
3-6
-------
first objective is to distribute the liquid as evenly as
possible at the top of the column. Experience has indi-
cated that, in smaller diameter columns (2 feet or less),
even when distribution is almost perfect initially,
coalescence of the liquid into streams will occur causing
channeling. To control the channeling effect, the liquid
should be redistributed periodically as it flows through
the packing. This is achieved by inserting porous re-
distribution plates at vertical intervals, in the packed
section, of 5 to 10 column diameters. The redistribution
plates are designed to act as a coarse sieve, provide
packing support, and yet not to inhibit the counter-
current flow of the gas. They are commonly referred to
as gas injection support plates.
The recovery efficiency for an absorption tower can be
predicted using a parameter known as the overall gas
mass-transfer coefficient, K0a, whose units are Ib. moles/
3 (1)
hr-ft -atm. ' The overall gas mass-transfer coefficient
for the column is analogous to the overall coefficient in
heat transfer. It is determined by combining the effects
of the .local coefficients in much the same way as the
overall heat transfer coefficient is derived from the
individual heat transfer coefficients of the system.
Thus, KGa is an overall measure of the resistance to mass
transfer. K a is based on a calculated overall driving
(3)
force and can be represented by the following equation;
N
KGa h A APTM
LM
3-7
-------
where,
N = Ib. moles solute material (CO-) trans-
ferred per hour
h = height of packing, ft.
A = cross sectional area of the column, ft.
APT = log mean partial pressure drive of the
solute, C02
It is seen that K.,a depends on the amount of gas to be
(j
absorbed, time required for passage, volume of the ab-
sorption column, and the operating pressure of the column.
The mass-transfer coefficient for the absorption of car-
bon dioxide from a carrier gas using sodium hydroxide is
approximately 2.25. This is a conservatively low
figure because there is some evidence that the value of
K.,a approaches infinity with small driving forces (e.g.,
less than 50 PPM soluble gas in the total). However, so
little is known about the vapor pressure and therefore
back-pressure in this region of small driving forces,
that this is more or less speculative.
The removal of CO? by caustic scrubbing involves absorp-
tion accompanied by a chemical reaction. Experience
indicates that use of a solution 2 N in sodium hydroxide
and maintenance of a carbon dioxide to carbonate con-
version of 15-25 percent will generally yield optimum
absorption of CO-. ' Detailed cost estimates are provided
in subsequent chapters.
3-8
-------
3.1.3 Ethanolamine scrubbing
Gas scrubbing with ethane-lamina (HOCH2CH2NH2) was considered
for the removal of carbon dioxide. This technology involves
absorbing the C02 into an ethanolamine solution at ambient
temperatures in a scrubbing tower. The solute is then steam
stripped back out of the scrub solution in a second contactor.
Such a process removes CO- from one gas stream and produces
another somewhat richer gas stream in C0_.
Past applications of this technology have been to streams
where C02 has been at combustion product levels (>5
volume percent). In the present situation it exists at
air concentration levels (.03 volume percent).
The particular operating problem of ethanolamine is its oxidiza-
tion to corrosive oxalic acid and glycine, which has been
experienced with such a process in the gas industry. This
would probably be amplified in a radiochemical application.
The benefit of possible increased concentration of CO- in
the gas is judged to be outweighed by the complexity and
size of this system, and by the unknowns inherent in such
a demanding application of relatively unsophisticated
technology. A product solidification technique would be
required in addition to the ethanolamine scrubber, resulting
in the need for a caustic scrubbing column, although this column
may be smaller. For all these reasons ethanolamine scrubbing
was rated unfavorable with regard to the present needs.
3.2 Other absorption techniques
3.2.1 Lime bed absorption of C02
Lime is a widely-used compound in many industrial processes,
including gas absorption and desiccation. Lime has been
3-9
-------
considered as a method to remove CO- from an air-like off-gas
stream. The process is a gas absorption process accompanied by
a chemical reaction. First, quicklime (CaO) is slaked by adding
water, to form calcium hydroxide. Slaked lime prepared in this
way i-s a white powder that can be mixed with more water and sand
to form mortar. The mortar hardens by slowly taking up carbon
(8)
dioxide and forming calcium carbonate. Gas absorption in a
lime bed is a limited application of this process. To avoid hard-
ening of the bed, the lime absorber must be replaced fairly often,
with only moderate buildup. This system does not represent an
efficient use of materials. Large volumes of waste and the slow-
ness of the chemical reaction make this method appear technically
less feasible than caustic scrubbing for the required application
of continuous or semi-continuous operation.
3.2.2 Absorption of carbon-14 dioxide in a fluorocarbon
solvent, dichlorodifluoromethane
Considerable discussion has been devoted to this method of removal
of hazardous radioactive off-gas constituents in recent years.
f 9)
Tentative preliminary designs have been proposed for reactor
and nuclear fuel reprocessing facility off-gas systems. How-
ever, experience to date has centered on an experimental unit at
the Oak Ridge Gaseous Diffusion Plant. Discussions of this system
have been presented with respect to Xe-Kr removal experiments by
Stephenson, et al., with respect to commercial reprocessing
applications by Murbach, et al. ' and most recently with respect
to Kr-Xe and C02 removal by Stephenson and Eby. ' Considerable
evidence has accumulated using the Oak Ridge system; the follow-
ing discussion is based primarily on that data.
3-10
-------
Many gaseous products of reactor operation, among them
carbon-14 as C02, are quite soluble in liquid refrigerant-
12, dichlorodifluoromethane. Krypton, xenon and carbon
dioxide are considerably more soluble than other volatile
gases which might be in the effluent stream, and favorably
temperature sensitive relative to the others. Differences
in relative solubility make separation possible. Because
lower temperatures increase the extraction efficiency,
systems are designed to operate at cryogenic levels. In
one system conceptualized for PWR application, a tempera-
ture of -27°F is chosen.(9)
One design has found pilot experience at Oak Ridge Gaseous
Diffusion Plant.(9) when scaled down to a size compatible
with a 1,000 MWe PWR, the design flowrate is 1 scfm. Feed
gas is dried, compressed to the absorber column operating
pressure, and passed through a molecular sieve to remove
trace water, oil and other fouling agents (for this appli-
cation C02 is considered a fouling agent). Then the gas
is chilled to appropriate temperatures and passed to the
absorption column for countercurrent extraction. The
solvent is drawn off and stripped of dissolved noble gases,
which can then be stored at 0.1 percent of the original
feed gas volume. Solvent refrigerant-12 is chilled and
recycled to the absorption column.
Tests at the pilot plant demonstrated a removal efficiency
of 99.90 percent for krypton and 99.99 percent for xenon.O)
Total vented gas in this case contained about 0.1 percent
of its input activity, or a decontamination factor of 1,000
No design or demonstration has been found for this system
on a BWR. The fundamental difference expected is the much
3-11
-------
higher flowrate experienced at the SJAE outlet. Any BWR
fluorocarbon absorption system must have a much higher in-
put capacity, though the principle is similar in all other
regards.
The relative solubilities of various off-gas constituents
are presented, in Figure 3-2,-as Henry's Law constant ver-
sus temperature.^, 14) j^ can be seen that carbon dioxide is
more soluble even than xenon, one of the two noble gas
fission products for which the fluorocarbon solvent tech-
nique was originally proposed. Carbon-14 is removed from
the off-gas stream by low temperature sorption just as
are krypton and xenon. A recent paper on the application
of the refrigerant-12 off-gas removal technique to a re-
(14)
processing plant indicates that CO- removals were
higher, in tests, than those for xenon, as Figure 4-2
predicts. This poses a complication for a system intended
to separate noble gases from the feed gas stream because
carbon dioxide would concentrate in the solvent and de-
crease its activity during recycle. It is for this reason
and others (fouling agents such as NO2 and water) that a
molecular sieve pre-treatment was suggested by Murbach, et
al. (1Q) with respect to a potential design for application
for the BNFP Separations Facility. In fact, carbon dioxide
removal using this method requires one extra step, either pre-
treatment with a molecular sieve or an additional solvent
stripping step. Nonetheless, this system merits consideration
as a potential part of an integrated process. Cost estimates
for the integrated process itself is outside the scope of this
report, but those for the molecular sieve adsorption system as
an independent C14 control method will be provided in Chapter 4,
3-12
-------
-120
-80
-40
40
TEMPERATURE, °F
Figure 3-2
Henry's law constant as a
function of temperature
for dichlorodifluoromethane
t Freon-12 )
3-13
-------
The most appealing aspect of a fluorocarbon solvent system
is the prospect of simultaneous removal of several off-gas
offenders. Flow rates at a current PWR would probably be
compatible with the size of system currently being tested,
while BWR's would require additional analysis due to much
greater flows. Fuel reprocessing plants would also re-
quire a flow rat£ capacity much larger than currently
under analysis.
A further consideration is the final waste product form.
If carbon dioxide is not removed prior to fluorocarbon
absorption, then it must be removed from the product stream
in a manner which provides a permanent storage form: a
compressed gas, which is not considered a suitable waste
storage medium for such a long-lived nuclide, or a solid
form such as calcium carbonate.(15) The latter alterna-
tive, discussed at length in this report, may be easily
accomplished with a caustic scrubbing device in common
use throughout the chemical industry- There is then the
matter of CC>2 which remains dissolved in the solvent after
normal stripping has occurred. Prior to solvent recycle,
further CC>2 removal might be accomplished by passing a
gaseous stream of solvent refrigerant-12 through a 13X
molecular sieve, following which the purified solvent
could be condensed and returned to the absorption column.
The use of 13X molecular sieves has been shown to be quite
effective in purifying R-12.d5) Experiments in that same
study indicated the 13X sieve could be regenerated with a
350°F, 6.85 cfm nitrogen purge flow supplied over 6 to 7
hours. Once again, l^CC^ contaminated purge gas must be
treated to create a solidified carbon-14 product form.
3-14
-------
It is concluded that absorption in a fluorocarbon solvent
is a potential carbon-14 removal technology. It presents
a possible method for simultaneous removal of several off-
gas constituents currently being reviewed as potential
health hazards. Such a system also has disadvantages in
this instance:
passage of off-gas containing carbon-14 dioxide
through this system results in multiple streams
requiring removal of lesser amounts of the
original C02 gas volume
achievement of a final solidified product form
will require further treatment of gaseous product
streams emanating from a fluorocarbon extractor
a carbon-14 dioxide contaminated fluorocarbon
solvent will be created requiring waste manage-
ment consideration.
These disadvantages must be weighed against the advantages
of such a system when a more specific design becomes
available. Perhaps it will be found to be more cost-
effective to remove CO- prior to fluorocarbon (or another
technique) noble gas removal by a system which provides a
one-step solidified product such as caustic scrubbing. In
any event, final judgment must await more specific data
than currently available and balancing of potential tech-
niques to accomplish cost optimization.
3.3 Adsorption techniques
Adsorption on a solid medium is another popular method for
the removal of one or more constituents from a gaseous
stream. The solid medium is usually arranged in a fixed
bed configuration with the gaseous stream passing through
the bed. The gaseous stream enters the bed, the constituent
which is to be removed is adsorbed on the solid medium and
the gaseous stream exits leaving the removed constituent
behind.
3-15
-------
3.3.1 Fixed bed adsorption of carbon dioxide with
molecular sieves
Another unit operation that can be used to remove carbon
dioxide from a gas stream is fixed bed adsorption. Fixed
bed adsorption is widely used to remove small quantities
of water, hydrogen sulfide, and carbon dioxide from other
gases. It is used primarily as a pre-treatment of feed
stock to cryogenic processes such as air liquefaction and
(2)
the manufacture of liquified natural gas.v '
The capture of carbon dioxide by fixed bed adsorption using
molecular sieves would require a pre-adsorption step to
dry the feed gas stream, removing essentially all of the
water. Two dessicant beds would be used so that one bed
could be on line removing water from a continuous flow of
gas while the second bed was being regenerated by a hot
air purge. Purge gas from the bed being regenerated would
be passed through a condenser and most of the captured
water would have to be routed to the liquid rad-waste system.
The dried feed gas stream is then routed through a mole-
cular sieve bed for the removal of carbon dioxide. As in
the case for the desiccating beds, two fixed beds would
be needed so that one could be receiving a continuous
gas supply while the other was being regenerated. A widely
used molecular sieve that effectively removes C02 is
sodium zeolite.
The bed being loaded would have to be held between -75°
and -78°C to achieve good adsorption. Bed temperature is
the most important parameter in loading considerations.
The regeneration of a loaded bed is accomplished by
heating it to a temperature between 150° and 350°C, then
3-16
-------
OFF GAS FROM
WATER REMOVAL
SUB SYSTEM
VACUUM PUMP
i
M
~J
TO
VALVES
§
O
LU
o:
CV.
o
MONITOR
FROM H20 REMOVAL SUBSECTION
,rTO PLANT
"i i *DFF GAS
C02 FIXATION TOWER
GAS/LIQUID
SEPARATOR
MICRO
PROCESSER
COOLER
AIR
DRYER
> DISPOSAL
COMPRESSOR
FIGURE 3-3 C02 REMOVAL SUBSYSTEM PIPING AND INSTRUMENTATION.
MOISTURE
MONITOR
-------
passing a gas purge through the bed at the elevated
temperature to remove the CO-, as show in Figure 3-3 .
Purge gas would have to be next passed through a caustic
scrubbing column or a slaked lime process in order to
isolate carbon-14 in a form that is currently acceptable
for permanent disposal. Again, the carbon dioxide is
precipitated as calcium carbonate. Following filtration,
the calcium carbonate cake would be incorporated into con-
crete and packaged for interim storage and/or ultimate dis-
posal.
There is concentration of CO- before it enters the caustic
scrubber or lime slaker. A cost estimate for this combina-
tion of molecular sieve-scrubber is provided in Chapter 4,
along with that of a molecular sieve-slaked lime combination,
The possibility of using molecular sieves in a throwaway
mode has also been examined. It would involve adsorbing
the C02 on the sodium zeolite medium and then removing and
packaging the medium rather than regenerating the bed.
This technique has been deemed technically infeasible for
the reason that a large fraction of the CO- trapped in
the sieves is desorbed as the temperature returns to
ambient from the cryogenic operating temperatures. Once
again, if this product could be physically isolated, it
is felt a gaseous form is unsatisfactory (the product must
be considered to be in a gaseous form even in an adsorbed
condition).
3-18
-------
3.4 Control of carbon-14 using an integrated cryogenic
distillation technique
One alternative to storage of gaseous reactor products is
cryogenic separation. This principle depends on differences
in boiling points of the several off-gas constituents. At
temperatures achieved with a liquid nitrogen coolant, the
various gases fractionate as follows:
Liquid, Solid or Slush Gas
Xe (B.P- = -107°C) N2 (B.P. = -196°C)
Kr (B.P. = -153°C) 02 (B.P. = -183°C)
C02(B.P- = -79°C) CO (B.P. = -190°C)
H2 (B.P. = -253°C)
(All boiling points are for one atmosphere
cover pressure)
Some constituents of the gas stream are liquified, frac-
tionally distilled and the distillates collected. Typical
purity limitation is encountered due to vapor pressures
of the liquid components,* impurities in the reactor off-
gases from which the liquor is composed and radiolytic
products formed in the distillation apparatus. Nonetheless,
product gases become separated to a high degree and they
can be stored at a greatly reduced volume and subsequently
released following decay holdup. They might also be
bottled and stored for long-term decay. The latter alter
native provides for nearly zero release of noble gas, while
both processes effectively remove iodine. In either case,
*Approximately 0.01 percent of the Kr and iodine and 0.025
percent of the Xe are vented with the carrier gases.
3-19
-------
decontamination factors measured from the SJAE off-gas
stream to the purified off-gas vent are taken to be 10,000
and 2,500 for Xe and Kr, respectively.^ ^ It is estimated
that the same DF is achieved by about 20-40 days of charcoal
holdup assuming the liquid effluent is held and released,
and not bottled. One vendor warrants its product for a
(18)
krypton DF of 10,000.
There has been little experience with cryogenic off-gas
systems on operating reactors, but designs have been tested
in many liquid air separation and other purification pro-
cesses. Appurtenances and feed/output possibilities vary
in different designs. In one choice, feed gas can come
directly from the SJAE line and pass through a hydrogen-
oxygen recombiner, holdup line and gas dryer prior to
entry in the distillation loop. However, to allow for
continuous operation during shutdown of the distillation
apparatus, a holdup tank or redundant distillation device
is provided, whichever is most economical. Some holdup
time in the egress line prior to venting provides decay
time for nitrogen and other activation products created
in the recovery and separation columns.
The distillation apparatus are similar in each system re-
viewed. Feed gas is deoxygenated to prevent excessive
ozone formation. It is then dried and chilled in a
regenerative pre-cooler to remove any high boiling compo-
nents which would clog the recovery column or reduce its
efficiency. The gas stream then passes, in a counter-
current fashion, in contact with liquified nitrogen (111.2)
coolant in which all products except nitrogen ozone, traces
of oxygen and hydrogen, and carbon monoxide are liquified.
The vent gases, which now contain very little Kr-85, are
3-20
-------
passed through a regenerative precooler and vented to the
atmosphere. The liquid fraction passes to a separation
column where it is fractionally distilled and the vaporized
constituents are removed and held separately- Alternatively,
the liquified products may be left as a mixture and stored
for decay in a holdup tank, then released after 45-90 days
(the time period is only for illustration). If bottling
is employed, on-site shielded remote handling facilities
must be available for the Kr-85 fraction until it is packed
in a transfer cask. A further design feature on some
separation columns is a recycle line to the feed gas holdup
tank for any occluded or entrained radioactive species.
The cryogenic apparatus is packaged in a positive pressure
inert atmosphere to prevent leakage hazards.
Several BWR's have proposed the use of cryogenic dis-
tillation systems for their SJAE off-gas treatment to
accomplish noble gas fission product decontamination.(19, 20)
Carbon dioxide has generally been regarded to be a fouling
agent in most systems reviewed because of its relatively
high freezing temperature. The freezing point of carbon
dioxide is also a triple point, so standard liquid to vapor
fractionation cannot normally be performed. Freezeout of
CC>2 in the liquid nitrogen absorber or the distillation
apparatus can impede heat exchange and flow streams.
For these reasons, it has generally been planned to provide
either a pre-cooling (initial freezeout) step as a cold-
trap for CC>2 or parallel molecular sieves with regeneration
14
capabilities. In either case, gaseous CC>2 must be
treated in a manner providing a stable, solid final form,
such as caustic scrubbing.
3-21
-------
Molecular sieves could provide significant CO concentration,
so the use of molecular sieves with a cryogenic distillation
unit provides some advantage for an integrated control system.
On the other hand, if a cold-trap could be designed to remove
the CO- before entry into the cryogenic distillation system,
and the removal of the C02 from the cold trap could be done
in a way that would concentrate the C02, a gas feed richer in
C02 could be sent to the scrubber, thus reducing feed volumes
and consequently the size of the scrubbing column. This is
speculation, however, as such a method has not been developed
(21)
and demonstrated for the commercial use described here.
Research and development efforts, as well as demonstration,
would be needed before a technical and economic assessment
could be completed. For all these reasons, cryogenic distil-
lation is seen as a potential integrated removal technology
for several radionuclides and not considered as a C^4 removal
method.
3.5 Summary
Several possible carbon-14 control technologies have been
examined. Cost estimates will be provided for comparison purposes,
A cost effective system to be used for carbon-14 isolation will
be designed, produced and maintained according to quality
specifications. In actual practice, a reliability of 95% can
be expected and required, with quality assurance programs
providing documentation in support of activities controlled to
that end.
Probable reliability of a system is an implicit consideration
subsumed in statements regarding technical feasibility. A
young technology is less favored than a mature one because
operating information is lacking. The decision to use an
3-22
-------
untried system involves more risk, and that risk is one
consideration of several reflected in recommendations
favoring or disfavoring specific isolation technologies,
3-23
-------
Chapter 3 References
1. John S. Eckert, "How Tower Packings Behave",
Chemical Engineering, April 14, 1975.
2. LNG Information Book, 1973, American Gas Association.
3. John S. Eckert, "Design Techniques for Sizing Packed
Towers", Chemical Engineering Progress, Sept. 1961.
4. Max Leva, Tower Packings and Packed Tower Design,
1951, U.S. Stoneware Company, Akron, Ohio.
5. Barnett Dodge and Norman Spector, "Removal of Carbon
Dioxide From Atmospheric Air", 1946, Transactions of
the American Institute of Chemical Engineers,
Vol. XLII.
6. Warren McCabe and Julian Smith, Unit Operations of
Chemical Engineering, 1967, McGraw-Hill, Inc.
7. Shreve, R. Norris, Chemical Process Industries,
McGraw-Hill Book Company, New York, 1967.
8. Pauling, Linus, College Chemistry, W. H. Freeman and
Company, San Francisco, 1964."
9. Griffith, Gary, "99% Cleanup of Nuclear Gaseous
Wastes", Power Engineering: March, 1973.
10. Murbach, E. W., W. H. Carr and J. H. Gray, III,
Fission Product Gas Retention Process and Equipment
Design Study, Chemical Technology Division, Oak Ridge
National Laboratory. ORNL-TM-4560, May, 1974.
11. Stephenson, M. J., et al, "Experimental demonstration
of the'selective absorption process for Kr-Xe removal",
Proceedings of the Twelfth AEC Air Cleaning Conference,
1973.
12. Stephenson, M. J., et al, "Absorption process for re-
moving krypton from the off-gas of an LMFBR fuel
reprocessing plant", Proceedings of_ the Thirteenth
AEC Air Cleaning Conference, 1975.
13. Stephenson, M. J., et al, Fluorocarbon Absorption
Process for the Recovery o_f Krypton from the Off-Gas
of Fuel Reprocessing PlanEs, United States Energy
Research and Development Administration, K-GD-1390,
Oak Ridge, 1976.
3-24
-------
14. Stephenson, M. J. and R. S. Eby, "Development of the
FASTER Process for removing krypton-85, carbon-14 and
other contaminants from the off-gas of fuel reprocessing
plants", Proceedings of the Fourteenth ERDA Air Cleaning
Conference, August, 1976 (in publication).
15- Croff, Allen G., An Evaluation.of Options Relative to
the Fixation and Disposal of_ C-Contaminated C0_2 as
CaCO., Oak Ridge National Laboratory, ORNL-TM-5171,
April, 1976.
16. Brown, R. A., Reference Facility Description for Volatile
Radioisotopes, Idaho National Engineering Lab., 1977
(in publication).
17. Environmental Analysis of the Uranium Fuel Cycle, Part
II; Nuclear Power Reactors.U.S. Environmental Pro-
tection Agency, EPA-520/9-73-003-C, Office of Radiation
Programs, Technology Assessment Division, November 1973.
18. Cryogenic Gaseous Radwaste Separation Process for Nuclear
Waste Gas Decontamination. Airco Cryoplants, Document
GRASP-72-262. Airco, Inc., Murray Hill, New Providence,
New Jersey 07974. Received April 1974.
19. Draft Environmental Statement by the United States Atomic
Energy Commission Directorate of Licensing Related to the
Susquehahha Steam Electric Station Units 1 and 2 of the
Pennsylvania Power and Light Company, Docket Nos.50-387
and 50-288, issued January 1973,Public Document Room,
Washington, D.C.
20. Draft Environmental Statement by the Directorate of
Licensing United States Atomic Energy Commission Related
to the Limerick Generating Station Units 1 and 2, Phila-
delphia Electric Company, Docket Nos.50-352 and 50-353,
issued December 1972,Public Document Room, Washington, D.C,
21. Personal communications with nuclear reactor vendors and
nuclear power plant owner/operators.
3-25
-------
CHAPTER 4. MODIFIED LWR EFFLUENT TREATMENT SYSTEMS
FOR THE CAPTURE OF THE MAJORITY OF C-14
The following independent C-14 control alternatives will
be examined.
1. Caustic scrubbing
2. Molecular sieve
3. Molecular sieve/caustic scrubbing
In the integrated control cases which include cryogenic
distillation or fluorocarbon absorption, CO- must be removed
first by one of the above alternatives. Therefore no cost
analysis will be given. NO removal being necessary for both
X
C-14 removal and krypton removal, will be considered a sunk cost
for both, resulting in some savings for the C-14 removal system.
These savings will be addressed.
4.1 BWR off-gas C-14 treatment system
As indicated in Chapter 2 it is estimated that approximately
99 percent of the C-14 released from a boiling water reactor
is via the steam jet air ejector exhaust (SJAE). The SJAE
flow rate is approximately 200 cfm untreated and drops to
between 20 to 30 cfm after being passed through an off-gas
recombiner, condenser, and dryer system. The composition
of the processed stream is essentially the same as air.
Many existing BWR's have off-gas recombiners as part of the
basic reactor effluent treatment system. Those which do
not have them may be required to retro-fit them, because they
4-1
-------
reduce the volume of gases to be delayed in the off-gas
systems, thereby increasing decay time and reducing the
quantities of radioactive gases released to the environment.
For this reason, the capital and annual costs of a recombiner
system will not be included in this evaluation as part of a
C-14 control system.
A preliminary economic evaluation will be performed to
identify the most cost effective alternative.
4.1.1 Caustic scrubber system
As indicated in Chapter 3, caustic scrubbing is a plausible
means of removing carbon-14 from BWR off-gas systems since
almost all the C-14 is in the form of C0~ in an air stream.
Therefore a more detailed treatment is given to this method,
although a range of cost estimates will be provided for the other
alternatives which are technically feasible.
From Figure 3-1, it can be seen that the major equipment
components of the scrubber include:
off-gas feed blower
absorption column and internals
mix tank
filter pump
recirculation pump
CaCO, filter
4-2
-------
In addition to these major equipment items, supporting
equipment is required including:
piping
' valves
instrumentation
electrical supply and control systems.
Like the recombiner/condenser, the liquid radwaste solidi-
fication unit is considered to be part of the basic reactor
system and is not part of the cost estimate. Such a
solidification unit is a standard item and is required in
all nuclear plants. It is expected that the majority of
solidification units could handle the additional radwaste
created by a C-14 control system.
Off-gas feed blower
The operating range of the feed blower is between 20 and
60 CFM with a AP of 20 inches of water. For purposes of
this evaluation, it is assumed that the blower is operating
at 40 cfm. A 3/4 HP direct drive blower is adequate. It
/4)
will have a 230/460 - 3 phase motor. v '
Additional equipment includes a surge tank, measuring pot,
recirculation pump (1 HP, 40 feet of head), valves and
piping.
4-3
-------
Carbon dioxide absorption packed column
The design procedure for the absorption column is presented
in Appendix A. The overall length and diameter of the ab-
sorption column is dependent on the desired CO- removal.
Table- A-l summarizes the results of Appendix A. The over-
all length of the column is 13.12 feet for 90 percent re-
moval of CO-, and 21.22 feet for 99 percent C02 removal.
All column designs accept a gas feed flow of 40 cfm. This
requires a column diameter of 12 inches for 90 percent and
99 percent removal of C0_. The bottom two feet of the column
act as a reservoir for scrubber solution (2 N NaOH). The top
three feet of the column, which are above the packed section,
serve as a disengaging section. Within this disengaging
section is a deentrainment unit constructed of woven metal
mesh 10 inches thick. Above the deentrainment unit is
a full cone, narrow angle (30°), 304 stainless steel, water
(8)
wash-down nozzle which can be used to back wash the unit.
The column is fabricated with 1/4 inch 304 stainless steel.
For the purposes of this evaluation, the column is designed
with 1 inch ceramic Berl saddles as packing. Any other
reasonable packing could have been used. The packing is
supported and gas feed is accomplished with gas injection
support plates, and the liquid feed to the column is by
means of a distributor to assure a good flowpath.
The scrubber solution is recycled externally to the absorp-
tion column through a recirculation loop containing a re-
circulation pump. The pump is capable of pumping 30 feet
of head and has the following specifications:
1 HP, 230/460 motor (10)
1 1/2 inch suction
1 inch discharge
6 inch impeller
Mechanical Seal
4-4
-------
Mix tank
The mix tank has a 9 gallon receiving capacity. Nine gal-
lons represents 25 percent of the scrubber column holdup
plus 1 gallon of calcium hydroxide solution with a 20 per-
cent freeboard still available. Such a vessel could be
approximately 1 foot in diameter and 1.5 feet tall and
fabricated from 1/4 inch, 304 stainless steel. The mix
tank is also equipped with an agitator which is mounted on
top of the tank with the propeller shaft entering the tank
through a teflon lipped seal. The propeller and shaft are
304 stainless steel. ^
CaCO-, filter and filter pump
J ' _ _ ._ ------ - _ -
Two types of filter can be used to trap the CaCO_.
The first type is a 5-micron ethylene-propylene cartridge
filter. The loading capability is about 35 grams per car-
tridge. The filter casing is made of 304 stainless steel
(14)
and is capable of housing 18 cartridge filters. The
filters would have to be changed about once every 7 hours
(once a shift).
Until recently, cartridge filters have been found to give
the most efficient and economic service among radioactive
waste filtration alternatives. One drawback of the
cartridge filter is the volume of radioactive waste that is
added to the system when the cartridges are discarded.
A second type of filter that has recently been introduced
into the industry is an etched disk backflush filter. The
filter is made with 316 stainless steel and has a loading
capacity of 500-2,000 grams. It can be back washed with
about 3 gallons of water. Although this type of filter
4-5
-------
involves a much greater initial capital cost, the savings
in not having to replace cartridges and decreased volumes
of radwaste make it competitive in the long run.
The filter pump is similar to the recirculation pump dis-
cussed previously.
Other types of filters can also be used. The operating and
waste disposal costs will be similar to those for the above
reference cases. Therefore, they are not included in the
subsequent economic analysis.
Piping and valves
The valves are two inch, 316 stainless steel air-operated
and teflon sealed. They can be operated from the control
panel. (10) There are eight valves as indicated in Figure
3-1.
The off-gas enters and leaves the scrubber system through
1/2 inch, 304 stainless steel, schedule 40 pipe. All
system piping carrying liquid will be two inch, 304 stain-
less steel, schedule 40 pipe. All piping is of fully welded
construction.
Instrumentation and control systems
The instrumentation is basically pneumatic in nature with
electronic read-out. All of the recorders and indicators
read out on a local remote panel board. The following list
of instruments will be required for the caustic scrubber system:
Equipment Item Instrument
Off-gas feed blower On-off light indicator
Gas flow rate recorder
Absorption columns Scrubber solution level recorder
Temperature and pH recorder
Recycle loop flow indicator
4-6
-------
Equipment Item (continued) Instrument (continued)
Recirculating pump on-off light
indicator
Differential pressure indicator
for packed section
Differential pressure indicator
across the deentrainment unit
Mix tank
Filter pump
Filter
Deentrainment unit spray nozzle
rotometer
Liquid level recorder
Agitator on-off light indicator
Pump on-off light indicator
Differential pressure indicator
4-7
-------
Cost Evaluation
Fabricated cost of equipment was used as the basic building
block to estimate the total capital cost of the various
C-14 cleanup systems. The majority of the equipment cost
data was obtained by direct contact with vendors, fabricators,
and construction firms.
It is assumed that the fabricated equipment costs represent
13.3 percent of the total capital cost, including both direct,
indirect costs and contingency. A discussion on capital cost
estimation and various cost factors can be found on pages
25-12 through 25-22 of Chemical Engineering Handbook, Edition
Five by Perry and Chilton. Figure 4-1 outlines the capital
cost estimating module concept utilized for this study -
The indirect costs shown in Figure 4-1 include engineering,
normal contingency, contractor fees, construction overhead,
administration, QA/QC, licensing fees and interest on capital
during the construction phase. To the above direct and indirect
costs, a 50 percent nuclear contingency is added to cover the
more stringent "tightness" requirements for a nuclear facility.
The special facilities requirements such as thicker walls
encountered in a nuclear reprocessing plant will be added to
the capital costs where appropriate. For PWRs and BWRs, the
concrete and steel factors shown in the module are sufficient,
as no extra shielding is required for the C-14 control system.
4-8
-------
apital Cost Estimating
Module Concept
Fabricated
Equipment
Piping
Concrete
Steel
Instruments
Electrical
Direct
Material, M
(E+M)
100
43
10
5
18
9_
185
Direct
Labor, L
(L)
85
35
Direct
Costs
((E+M+L)
Direct and Indirect Cost Factor
Nuclear Contingency
Total Module Cost Factor
270
Indirect
Cost Factor
(XI.85)
I
500
250
750
Figure 4-1
4-9
-------
The annual carbon fixation costs for the various C-14 clean-
up systems are calculated as present worth values assuming a
30-year operating life for a reactor and an 8 percent compound
interest rate. The operating costs include labor, chemicals,
maintenance and replacements. Annual fixed charges are 20
percent of capital costs.
Fabricated equipment costs for a. BWR caustic scrubber
removal system for C-14
Table 4-1 summarizes the fabricated equipment costs for a BWR
off-gas C-14 removal system. Two system options are addressed:
Option A - The system contains disposable cartridge
filters.
Option B - The system contains a backflush filter.
Within each option are defined the following cases:
Case I - 90% removal of entering CO-
Case II - 99% removal of entering CO-
4-10
-------
Table 4-1
Fabricated Equipment Costs for BWR C-14 Scrubbing System
Item Cost
1. Off-Gas Blower $ 490
2. Absorption Column - Case I 2,400
- Case II 3,900
3. Column Internals
a. Packing - Case I 90
- Case II 180
b. Gas Injection Support Plates
- Case I (1) 210
- Case II (2) 420
c. Liquid Distributor
- Case I 220
- Case II 220
d. Wire Mesh 25
e. Wash Down Nozzle 36
4. Mixing Tank 360
5. Agitator 500
6. Chemical Charging Tanks
a. NaOH 350
b. Ca(OH)2 350
7- Recirculation Pump 1,200
8. Filter Pump 1,200
9. CaC03 Filter Unit
Option A - cartridge filter 1,300
Option B - backflush filter 10,000
4-11
-------
Table 4-1 (continued)
Item cost
Total fabricated equipment cost
- Option A
a. Case I $ 9,000
b. Case II 10,000
- Option B
a. Case I $17,000
b. Case II 19,000
4-12
-------
Based on the above discussion, the total capital cost of
these systems can be expected to be as follows:
Option A
Case I $ 67,500
Case II 75,000
Option B
Case I $128,000
Case II 143,000
Annual CO^ fixation costs for a BWR off-gas C-14 treatment
system by caustic scrubbing
The total labor costs associated with the operation and main-
tenance of a carbon-14 control system are spread across a
reactor facility's entire organizational structure. This
additional off-gas treatment unit requires support from the
maintenance, engineering, QA/QC, and administrative staff.
(18)
Figure 4.2 is a typical reactor staffing plan. This
diagram indicates the complex interactions of a reactor staff.
(19)
Figure 4.3 shows a second staffing plan. The personnel
requirements for Figure 4.3 are summarized in Table 4.2.
The operating staff of a reactor plus the supporting adminis-
trative staff number nearly 100 people. It is anticipated
that the additional work load for a reactor staff from a
retrofitted Carbon-14 control system would be approximately
one percent of the total facility work load. Depending on
how cost-effective the staffing plan is at a given site,
staff numbers may change. As an example, if the staffing
has some excess man power at most points within the organiza-
tion there may not be a staff increase. But if at a specific
reactor a shortage of staffing exists, more than one staff
member may be required.
4-13
-------
It is estimated that the general quality of staffing addition
required for the approximately one percent work load increase
would be at the operator qualification level. A new reactor
with a carbon-14 control system incorporated into the basic
design may have a slightly reduced additional work load, but
not reduced significantly- The annual operating costs for the
systems include labor, chemicals, utilities, maintenance, and
replacement. Maintenance and replacement costs include re-
pair and-replacement of equipment. For this study, 7 percent
of the original capital cost is assumed for the maintenance
and replacement costs. An average capital cost of
$100,000 is assumed for the above options. The labor cost
assumes one additional staff member at the qualification level
of an operator at $25,000 per man year. An illustration of
operator costs can be found in Figure 4-4. Chemical costs
are assumed to be $1,000 per year and utility costs are negligible,
The time requirements to operate the system with cartridge
filters is the same as for the system with back flushable
filters. In one case an operator is removing filter cartridges,
and on the other the operator is running a control panel. In
both cases attendance during operation is required, whatever
be the activity of an operator during that time. Therefore,
the operating costs are:
Labor
$25,000 x 1.0 = $25,000
Maintenance and Replacement
$100,000 x 0.07 = 7,000
Chemicals 1,000
An annual fixed charge (20% of the capital costs) results
from insurance, taxes and depreciation.
Fixed charges $20,000
Total annual costs of fixing
C02 as CaC03 $53,000
4-14
-------
PUNT
SUPERINTENDENT
3.
ASST. PLANT
SUPERINTENDENT
-
-
1
ADMINISTRATIVE
SUPERVISOR
ADMINISTRATIVE
STAFF
1
MAINTENANCE
SUPERVISOR
MAINTENANCE
ENGINEER
MAINTENANCE
STAFF
-
H
r-
1
1
1
1
1
I
1
1
1
1
l»
1
OPERATIONS
SUPERVISOR
SL
1
SHIFT
SUPERVISOR
SL
CONTROL
OPERATOR
L
ASST. CONTROL
OPERATOR
L
AUXILIARY
OPERATOR
UCI DCD
1.
-
-
MM
M
M
^
1
ENGINEERING.
SUPERVISOR
REACTOR
ENGINEER
NUCLEAR PLANT
ENGINEER
CHEM.&RAD.
PROT.SUPV.
CHEM.&RAD.
TECHNICIAN
INST.& CONTROL
SUPERVISOR
|
INST.& CONTROL
TECHNICIAN
-
-
-
-
b
1
PLANT QUALITY
ASSURANCE
SUPERVISOR
(
QA/QC
STAFF
LEGEND: SL- Senior Reactor
Operator Licens*
I o n
L Reactor Operator
License
Figure 4.2:-Example of a Typical Reaotor .Staffing Plan
-------
I
H1
a\
SECURITY FORCE (11)
OPERATIONS
SUPERVISION
. OPE RATING SHIFT
j CREW (8)
UL
EL n
(6) I
RADIATION
PROTECTION
ENGINEER
Li
(5)
ICJ
PLANT SUPERINTENDENT
TOTALSTAFF
77 PERSONS PLUS ADMINISTRATIVE STAFF
ASSISTANT PLANT
SUPERINTENDENT
ADMINISTRATIVE STAFF
CLERICAL, CUSTODIAL
TECHNICAL
SUPERVISION
PLANT CHEMIST
INSTRUMENTATION
AND CONTROLS
ENGINEER
PLANT
PERFORMANCE
ENGINEERS (3)
TECHNICIANS (9)
Augmonttd by 10 iptcltl craft loc*Ud off lit*
MAINTENANCE
SUPERVISION
MAINTENANCE
PERSONNEL (18)*
Figure 4.3: Example of Alternative Reactor Staffing Plan
-------
Singto and Dual Unit
Plant Staffing
Single Unit Oo«J Unit
Ration Station
Plant Management
Superintendent*
Assistant*
1
1
1
1
Operations
Operations Supervisors*
Shift Supervisors*
Lead Operators/Foremen*
Control Operators**
Auxiliary Operators
Lead Fuel Handlers/Foremen
Fuel Handlers
Technical
Technical Supervisor
Professionals
Technicians
Maintenance
Maintenance Supervisors
Craft and Repairmen
Security
Totals
1
6
-T
11
11
1
6
9
1
18
J1
77
Senior Llcamed Operator Qualification*
Licaraed Operator Qualification*
Special Senior LJcanaed Operator Qualif icatione
2
6
5
16
16
3
6
1
9
16
2
28
16
128
Table 4.2:Personnel Requirements for
Alternative Reactor Staffing Plan (Figure 4. 3)
4-17
-------
AN EXAMPLE OF
OPERATOR COSTS
Basic Salary
$8.00/hour x 2,080 hours/year = $16,640
Payroll Burden
Federal Old Age Survivors Insurance
Workmen's Compensation
Pensions
Life Insurance
Company Contribution to the
Thrift Plan
38% of $16,640 = 6,323
Replacement Costs for:
Two-week vacation
Eight-day sick leave
Nine-day holidays @1.5 rates
14% of $16,640 = 2,330
$25,293
Figure 4-4
4-18
-------
The 30-year present worth factor at 8 percent interest per
year is 11.26. Therefore, the present worth value of the
30 years of annual fixation costs would be 11.26 x $53,000 =
$597/000.
4.1.2 Fixed bed adsorption for C-14 control
This alternative has been proposed as a potential C02 removal
system which removes all but 3 ppm of the CO- in the gas
stream.(20)
CO- is removed by passing the gas from the H_0 removal sieves
through two 13-x sodium zeolite beds at approximately 5 atmosphere
at 95°F.
Regeneration is accomplished with a smaller gas flow to main-
tain high C0_ concentration in the stream. The gas is then
diverted to the bottom of the CO- fixation tower where the
gas bubbles through a saturated solution of Ca(OH)- which
reacts with the CO- to form CaCO.,. The gas is next vented to
the hood over the vacuum drum filter. The liquid and gas pass
through the filter media to a gas-liquid separator.
The fabricated costs for the subsystem comprising H-O regenera-
tive beds and CO- regenerative beds are $70,000 from vendor
estimates. This compares with the costs given in reference 5.
The capital costs, based on the module factor of 7.5, are
$525,000 for the fixed bed adsorption process, including
instrumentation, piping and valves.
4-19
-------
Table 4-3
Equipment List for Fixed Bed Adsorption of CO-
1. H20 Sieves (3)
2. CO- Sieves (3)
3. Air Dryer
4. Air Compressor
5. CO- Fixation Tower
6. Vacuum Filter
7. Screw Conveyor
8. Dryer
9. Blower
10. Heater
11. Gas Liquid Separator
12. Lime Slaking Tank
The tanks, tower, filter housing, pump, piping and valves
are made of 304 stainless steel.
4-20
-------
The capital costs for the slaked lime subsystem can be ob-
tained by scaling down the costs given in reference 15 of
Chapter 3, to a lower limit of $60,000. Thus, a lower limit
for the total capital costs is $585,000.
The annual fixation charges include.:
Labor
$25,000 x 1.0 = $ 25,000
Maintenance and Replacement
$585,000 x 0.07 = $ 37,000
Chemicals = $ 1,000
Fixed charges: 585,000 x 0.2 117,000
Total annual costs $180,000
The 30-year present worth is: 11.26 x 180,000 = $2,027,000
4.1.3 Fixed bed adsorption with caustic scrubbing for C,. Control
From vendor estimates,^ ' the CO- can be concentrated by the
fixed bed adsorption and regeneration process so that a gas
stream of 10 cfm, one quarter of the original stream, is di-
verted to the caustic scrubber system.
As in the previous cost analysis, the capital cost for the
fixed bed adsorption process is $585,000.
The 10 cfm caustic scrubbing capital costs are scaled down
from those for the 40 scfm case.
,10. °'6 x $100,000 = $43,500
W
The total capital costs are: $629,000. The annual fixation
charges include:
Labor
$25,000 x 1 = $25,000
4-21
-------
Maintenance and replacement
$629,000 x 0.07 = $ 44,000
Chemicals 1,000
Fixed charges
$629,000 x 0.2 $126,000
Total annual costs $196,000
30 year present worth $196,000 x 11.26 = $2,207,000
We can see that caustic scrubbing is the most cost-effective
C-14 control system.
In the following sections, only the caustic scrubber alternative
will be considered for the PWR and LWR fuel reprocessing plant.
4.2 PWR off-gas C-14 treatment system
In pressurized water reactors, with the present limited
data, it is estimated approximately 76 percent of the
carbon-14 comes from the gas collection header and is held
up in the waste gas decay tanks before being vented to the
atmosphere. Since C-14 at the header may be predominantly
in the form of hydrocarbons, it must be converted to CO-
before it can be removed by scrubbing. This can be achieved
by installing a recombiner upstream of the waste gas decay tanks.
Once decay of short-lived isotopes has taken place, the waste-
gases must be processed. The same type of scrubber system
4-22
-------
that is described in the previous section for BWR off-gases
provides adequate operational conditions for treating gas
from the waste gas decay tanks. Note that control system
operation for a PWR is intermittent, due to the fact that
short-lived isotopes must decay in the waste gas decay tank
before its contents are treated, so the scrubbing system will
not operate continuously.
Capital and annual costs for a PWR off-gas removal system
for C-14
The difference in cost between the BWR C-14 removal system
and the PWR C-14 removal system is in the inclusion of the
PWR recombiner. The recombiner is sized to accept the maximum
flow from the PWR primary off-gas stream. This is approximately
one cubic foot per minute. The purpose of the recombiner is
to oxidize hydrogen to water. The carbon-14 control system
takes advantage of this system to oxidize hydrocarbons to CO-
and water. There is no other commercially available process
unit that can perform this oxidization step in a manner that
satisfies regulatory constraints.
A PWR recombiner system costs $160,000 and includes a preheater,
recombiner, post recombiner condenser and dryer,- valves and
(14)
control panels. Without valves, piping and instruments,
the fabricated cost is $100,000 based on the cost module.
4-23
-------
As indicated, the equipment design for the PWR system is
essentially the same as for the BWR. The major differences
are the intermittent operation of the PWR scrubbing system,
an off-gas flow rate 40 times smaller,- and inclusion of a
recombiner.
A total of four cases were estimated for the BWR system
(40cfm off-gas). The fabricated equipment costs for the four
cases ranged from $9,000 to $19,000, with an average of $14,000.
The addition of a $114,000 recombiner for the PWR system over-
shadows these fabricated equipment costs.
Therefore, one cost of $114,000 has been selected to represent
the PWR case. This is the sum of $100,000 for the recombiner
and $14,000 for the other fabricated equipment costs.
As indicated for the BWR, the fabricated equipment cost repre-
sents 13.3 percent of the total capital cost. Therefore, the
total capital cost of the PWR is estimated at $855,000.
Annual costs for the system are estimated by the same method
used for the BWR system. The labor costs assume one additional
staff member at the qualification level of an operator at
$25,000 per man year.
Labor
$25,000 x 1.0 $ 25,000
Maintenance and Replacement
$855,000 x 0.07 $ 60,000
Chemicals 1,000
Fixed charges $171,000
Total annual costs of fixing CO-
as CaC03 $257,000
4-24
-------
The 30-year present worth factor at 8 percent interest per
year is 11.26. Therefore, the present worth value of the
30 years of operating costs would be 11.26 x $257,000 ="
= $2,894,000.
Retro-fit costs and schedules
It is impossible to provide an accurate estimate of either
a generic cost or generic schedule of system retro-fits.
All retro-fits are site and facility specific and will surely
vary considerably- The important factors that affect cost
and schedules include:
Facility operating schedules
Available space envelopes for the installation
of new equipment
Accessibility of required tie-in points for both
process functions and utility support systems.
Availability of space envelopes for control and
support functions
Extent of licensing activities.
As an example of what would be involved in retrofitting a
caustic scrubbing unit for the removal of C-14, a sample
case is provided. The sample case chosen is the Davis-Besse
Nuclear Power Station, Unit I, which is a PWR.
Figure 4.5 shows the location of the waste gas decay tanks.
They are housed at elevation 545" of the auxiliary building,
elevation 585' being ground level. The room which houses the
waste gas decay tanks does not have sufficient room to house
a scrubbing system since the tanks occupy most of the space
in the room.
Figure 4-6 shows the waste solidification and drumming room.
Note that it is diagonally opposite the waste gas decay tank
4-25
-------
room and at an elevation of 585'. This room also does not
have sufficient space to house the C-14 scrubbing system.
Since the waste gas decay tank room is below ground level,
it would be extremely difficult to build a room adjacent to
it. The other alternative is to construct a room alongside
the auxiliary building adjoining the waste solidification and
drumming area. This would require new construction and knock-
ing out a portion of the auxiliary building wall to allow
entrance to the scrubber room. The arrangement is shown in
Figure 4-6.
A gas line would be connected to each waste gas decay tank,
brought to a common junction and run vertically upward from
the waste gas decay tank room to the auxiliary building ceil-
ing, then down the side of the building to the drumming area
and finally into the scrubber room. This path represents the
least number of problems for retrofitting as far as knocking
holes in walls, and avoiding existing equipment. Holes would
have to be cut in floors to run the lines vertically- The top
of the auxiliary building is open and presents no barriers.
Table 4-4 serves to illustrate the major items that must be
included in the retrofit of the C-14 cleanup system and an
estimate, where applicable, of the features and requirements
of each item.
It is seen that each reactor layout has its own specific
problems. The unusual construction problems are those en-
countered in working in an actual or potentially contaminated
area. In addition special security procedures come into place
when working in controlled access areas.
Preliminary estimates associated with the Davis-Besse reactor
would suggest the additional structure and other modifications
4-26
-------
TABLE' -4
Retrofit Items
Size
Amount
Materials
Special Requirements
Alterations to structures
1. Addition of room to house
caustic scrubbing system
2. Penetrations
Utilities Support
1. Water
2. Chemicals
3. Electrical
20'x20'x30'
(21 wall thickness)
35-100
4. Steam
5. HVAC
6. Decontamination System
(including Floor drains)
Control and Instrumentation
1. Instrument Leads
2. Motor Control Centers
Flow Devices
1. Piping 2"
2. Valves (with controls) 2"
3. Connectors (elbows, tees, etc.) 2"
Supports
1. Hangera
500'
10
50
50
concrete rebar
insulation paint
Seismic Category
I
IEEE Std. 279
(protection system)
IEEE 300
(criteria for class IE)
IEEE 323
(Qual. of class I eqpt.)
IEEE 336 (N45.2.4)
\Q. A. req'ts)
IEEE 344
(seismic Qual.)
(see above IEEE Criteria)
Stainless Steel ASME class 1
Stainless Steel ASME class 3
Stainless Steel ASME class 3
Descriptions of Representative Retrofit Items
-------
waste gas decay tank
gas line
Figure 4.5: Davis Besse Nuclear Power Station Elevation 545
4-28
-------
gas line
solidification
and drumming
room
auxiliary building ,
penetration and doorway /
Figure 4.6:
new room to house caustic
scrubbing system
Davis Besse Nuclear Power Station Elevation 505
4-29
-------
might approach $500,000 while the time requirement may be
about six-months.
It should be emphasized that each retrofit is site-specific
and the particular retrofit analyzed here only serves to
illustrate some of the considerations in retrofitting the C-14
cleanup system. Extensive engineering work, well beyond the
actual or intended scope of work, would be required to complete
the engineering and cost estimate on even one reactor.
The largest cost item associated with the retro-fit of a C-14
control system for any LWR will be the production revenue lost
during the final phase of construction, tie-in, and commission-
ing. The lost revenue from an outage of a reactor can range
from $300,000 to $500,000 per day. If the system is constructed
independently and tied-in to the off-gas system at a scheduled
outage, the costs in lost revenue would be moderate. Depend-
ing on how the construction of a C-14 control system interferes
with the operation of a reactor the outage might range from
one week to one month.
Licensing activities include preparation of documents and
participation in hearings. These may require extensive outlays
of time and money.
The retro-fit of a system into a radioactive facility entails
unusual, and additional, construction problems. Workers must
be trained in radiation protection and control procedures.
Construction barriers must be established to control loose
contamination. Finally, special security systems and procedures
are needed to prevent industrial sabotage of a radioactive
facility.
4-30
-------
Table 4-5 summarizes the cost factors directly related to
retrofit. The costs are presented as ranges.
The schedule for the installation of a retrofit carbon-14
control system could range from 3 to 5 years. The major
activities required for retrofitting include:
Initial analysis in support of system choices
Engineering
Procurement of equipment
Construction of the system
Checkout and startup
Licensing
A possible schedule is shown in Figure 4.7.
As indicated on page 5-4, for a newly designed LWR there are
no engineering, procurement, or construction problems that
would represent a change in the basic facility schedule. All
of the equipment required for this system is commercially
available.
4-31
-------
Table 4-5
COST FACTORS DIRECTLY
RELATED TO RETROFIT
Range $ x 10
Lost production revenue
ranging from 1 week
to 1 month 2 to 15
Licensing activity costs 0.1 to 1.0
Unusual construction
problems 0.05'to 0.5
4-32
-------
10
u>
Typical Retrofit Schedule
For a C-14 Control System
Scoping studies
Engineering
Procurement
Construction
Checkout and Startup
Licensing
Year 0
Figure 4-7
-------
Chapter 4 References
1. Private communication between SAI and the Nuclear
Regulatory Commission.
2. "Environmental Radiation Protection for Nuclear Power
Operations", Proposed Standards (40 CFR 190),
Supplementary Information, January 5, 1976.
3. Private telephone communication between SAI and Bechtel
Power Corporation, Gaithersburg, Maryland and San
Francisco, California.
4. Private telephone communication between SAI and Elwood
Nuclear Safety Inc., Buffalo, New York.
5. E. D. North and R. L. Booth, Fission Product Gas Reten-
tion Study. Final Report, ORNL-TM-4409. 1973, pp. 51-52
6. Private telephone communication between SAI and Norton Co.,
Akron, Ohio.
7. Private telephone communication between SAI and ACS
Industries, Inc., Woonsocket, Rhode Island.
8. Private telephone communication between SAI and Spray
Engineering Co., Burlington, Massachusetts.
9. Private telephone communication between SAI and Chemineer
Agitators, Inc., Dayton, Ohio.
10. Private telephone communication between SAI and Duriron
Co., Inc. Dayton, Ohio.
11. Private telephone communication between SAI and Armco
Steel Corp., Baltimore, Maryland.
12. J. Happel and D. G. Jordan, Chemical Process Economics,
Marcel Dekker, Inc., New York, 1975, p. 235.
13. Private telephone communication between SAI and Vacco
Industries, El Marte, California.
14. Private telephone communication between SAI and WACO
Associates, Inc., Lafayette Hill, Pennsylvania.
4-34
-------
15. Private telephone communication between SAI and a
chemical supply warehouse.
16. Private telephone communication between SAI and
Cosmodyne, Inc., Torrance, California.
17. I. Leibson and C. A. Trischman, "Spotlight on Operating
Cost", Chemical Engineering, May 31, 1971, pages 69-74.
18. Portland General Electric Company, Docket No-50-344,
Operating License and Appendices
19. WASH-1130 Revised, Utility Staffing and Training for
Nuclear Power. June 1973.
20. R. A. Brown, Reference Facility Description for Volatile
Radioisotopes, Idaho National Engineering Lab., 1977
(in publication).
4-35
-------
CHAPTER 5. DESIGN MODIFICATION TO NEW LWR FACILITIES
FOR THE CONTROL OF C-14
Design changes to new light water reactors that might be
implemented in order to remove carbon-14 from the facility
effluents may be significantly different from the retro-
fit designs of Chapter 4. Following sections discuss
design changes for boiling water and' pressurized water
reactors based on criteria this study has identified or
assumed in Chapter 2 (Tables 2-2 and 2-3) regarding the
major carbon-14 release pathways.
It should be pointed out that definitions of these pathways
are preliminary in nature and based on a limited number of
carbon-14 measurements in reactors of earlier design. A
review of Chapter 2 indicates that greater than 99 percent of
the C-14 discharged from a BWR is reported to be from the main
condenser air ejector exhaust. But in the case of a PWR,
approximately 16 percent of the C-14 is reported to be dis-
charged from the fuel handling building ventilation and approxi-
mately 12 percent is said to be discharged in containment purges.
The calculated value for the containment purge discharge using
standard leak rates is less than about 0.01 percent. In con-
trast, reported values of C-14 discharges from both the PWR
fuel handling building and the containment are based on laboratory
data which approach the lower detection limit of the analytical
methods utilized.
5.1 BWR design modifications
The only source for carbon-14 in a BWR plant considered
by this study, because it contains 99 percent of the
5-1
-------
off-gas carbon-14, is the exhaust from the SJAE condenser
vent. Following the condenser, a recombiner can be
installed which would eliminate radiolytic H? and 0~ and
cool the gas stream to about 140°F. Gas flowrate at this
point-should be no more than 40 cfm. This stream could be
treated quite readily in a caustic scrubber following the
design principles of Chapter 4. It is emphasized that the
effluent gas from the recombiner need not be dried if its
immediate destination is a caustic scrubbing column. New
plants incorporating both systems may wish, therefore, to
leave out a drying step after the recombiner. It is
currently thought that a recombiner system will be required
in new BWR facilities. The resultant cost of such treat-
ment would be essentially the same as reported in Chapter 4.
5.2 PWR Design Modifications
Carbon-14 isolation from PWR off-gas streams will be more
involved than in the BWR, especially if the reported
pathway proportions are confirmed by future reactor sampling
programs. Sources subject to potential design modification
would include the gaseous radwaste treatment system, second-
ary system condenser air ejector, fuel handling building
ventilation, and containment building purge exhaust.
Present projections of C-14 discharges rates would suggest
that the treatment of these four streams may result in the
capture of greater than 99 percent of the C-14 presently being
released.
The condenser air ejector flow of 25 cfm could be treated
by a scrubber system similar to the one discussed in
Chapter 4. It may join tasks with the system proposed
5-2
-------
for the primary gaseous radwaste stream.
The fuel handling building ventilation flow of 2470 cfm
presents a different type of engineering problem. It
is a relatively large flow with a very low concentration
of C-14. Instead of treating the large flow of air,
internal recycle of 95 percent of the ventilation air would
reduce the amount of gas to be treated to 120 cfm. This volume
of gas could more easily be treated by a caustic scrubber system.
The containment building purge represents the most chal-
lenging problem because the flow is both large and inter-
mittent. The volume to be treated is approximately
10 cubic feet four times a year. The treatment of a very
large flow of air for recovery low Concentrations of carbon
dioxide is presently not a commercial practice. A great
deal of work is required in both engineering and develop-
ment aspects to resolve this problem. One potential solution
would be to store the purge gas and treat it on a con-
tinuous, but diminished, rate prior to the next purge.
5-3
-------
5.3 Reduction of carbon-14 by control of parent elements
Table 2-1 indicates the amount of carbon-14 produced from
various parent elements. It has been suggested recently
that some carbon-14 control may be effected prior to its
creation by limiting the amount of parent substances
subject to irradiation.(1) Such control would reduce
releases from LWRs and separations facilities.
Two neutron activation reactions were shown to dominate the
production of carbon-14:
17 14 14 14
170 ( n, a )^C and ift N ( n, p ) C. In fuel,
the amount of oxygen present is completely dependent on
the mass of fuel required and is therefore somewhat in-
flexible to adjustment. The oxygen reaction accounts for
approximately 20% of the fuel source term, as long as assump-
14 1^
tions about the N reaction are realistic. The amount of *C
14
resulting from N is dependent on an educated assumption
as to the extent of nitrogen impurities in fresh fuel. A
decision regarding nitrogen control depends on the source of
N in the fuel. If nitrogen is present in raw materials,
control may be impossible. If the greatest portion is in-
troduced during fuel manufacture, control may be achieved,
though the final level of prevention depends on a quantitative
knowledge of nitrogen impurities in the fuel. According to
the data in Table 2-1, about 80% of the fuel source term
would be subject to reduction by control of nitrogen im-
purities. The greatest effect of a diminished fuel source
term would be felt at the separations stage, though reactor
effluent levels might also be reduced.
The amount of coolant oxygen is fixed, and the amount of
coolant nitrogen is known with, little confidence. As stated in
5-4
-------
Section 2.1.2, the source term for coolant carbon-14
14
resulting from neutron activation of N is assigned a
nominal value awaiting measured levels. In no case at
present could carbon-14 be considered to be subject to
control by elimination of parent elements in the coolant.
5-5
-------
Chapter 5 References
1. Proceedings of the International Symposium on the
Management of Wastes from the LWR Fuel Cycle. CONF-
76-0701, July 11-16, 1976, Denver, Colorado, (page 381)
5-6
-------
CHAPTER 6. CURRENT SPENT NUCLEAR FUEL
REPROCESSING EFFLUENT
TREATMENT SYSTEMS
Spent nuclear fuel contains significant quantities of
fissile materials. This fissile material includes both
U-235 from the original enriched uranium fuel and plu-
tonium generated by reactor operations. It represents
a potentially large source of energy if the fissile
material is recycled back to reactors as recycled fuel.
The first step in the recycle of this fissile material
is the chemical reprocessing of spent nuclear fuel.
Figure 6-1 is a block flow diagram showing the major
process unit£ of such a reprocessing facility. These
operations generate process off-gases, process liquid
waste, and liquid effluents.
Some difficulty arises at this time in treating re-
processing facility off-gas systems in a generic fashion.
There is only one such facility of the modern type where
designs have been finalized and constructed. That
facility is the Barnwell Nuclear Fuel Plant (BNFP) and
it is here used to exemplify current concepts in process
design. Newer plants, such as that proposed by Exxon
Nuclear Company, may be forthcoming. An analysis such
as this one, however, requires concrete information
available only from current experience and criteria.
Specific data in this analysis come from the BNFP Final
Safety Analysis Report for the Separations Facility.
Other sources discuss details of the Separations
Facility as well.(3'4)
6-1
-------
NUCLEAR FUEL REPROCESSING FLOW DIAGRAM
Cask
Receiving
i
Fuel Storage
Pool
t
Shear
li i \
JT Stack ^
rnT^
j
Dlssolver
Off-Gas .'>'
' Treating
,
Dissolution
&
Feed Prep
1
PlJwlrte1?!^
v Disposal ^
Acid
./Recovery :
Recovered
^ Nitric Acid
Recycle '
Fission
Product
Removal
i
r
-------
The nuclear fuel reprocessing flow diagram of BNFP is
shown in Figure 6-1. Treatment systems are in various
stages of development. The cask receiving and fuel
storage pool areas are primarily subject to contamina-
tion via leaking fuel rods which spill gaseous contents
into the cooling water. Some of these gases partition
into the building atmosphere, though measurements are
not available for BNFP. Presently, this atmosphere is
purged on a continuous basis through a filtration system.
The cooling water is continuously demineralized and a
certain fraction of leaked nuclides are removed, while
the rest presumably remain in the water. They do not,
however, escape to the environment in an uncontrolled
way. After the fuel storage pool, fuel travels to the
shear area for hull removal. Process effluents from
this point forth are separately treated and are dis-
cussed in the following chapter.
6.1 Process off-gas treatment
A process off-gas treatment system is part of the basic
flowsheet of all nuclear fuel reprocessing facilities.
Examination of Figure 6-1 reveals several different needs
for off-gas treatment, not all of which pertain to radio-
logical hazard directly. The general treatment processes
involve:
removal of process condensates derived from
off-gas condensers
129
iodine (predominantly longer-lived I) re-
moval by both wet chemical scrubbing and
fixed bed adsorption
6-3
-------
removal of nitric acid and nitric acid fumes
("N0x's") formed from thermal and radiolytic
decomposition of dissolved nitric acid and
nitrates
final high efficiency particulate filtration
A schematic diagram of the interrelations of these treat-
ment processes is provided in Figure 6-2. More will be
said of the specific processes at BNFP in Chapter 7.
However, the two major process sections are described
here for reference. The first section handles and treats
the off-gas from dissolvers and is referred to as the
dissolver off-gas system (DOGS). The off-gas from the
majority of the process vessels enters the treatment
system following the N02 Absorber Eductor." At this point,
the off-gas treatment system is referred to as the vessel
off-gas system (VOGS). The flow of gas in the dissolver
off-gas system can be expected to range from 300 to 500
scfm, while the flow in the vessel off-gas system can
range as high as 6,000 CFM. The combined DOG and VOG
streams are treated further, filtered and mixed with air
from the ventilation system for release through the Acid
Fractionator Overhead Vaporizer and the 100-meter main
stack.
Other harmful materials besides carbon-14 are under con-
sideration for removal from the waste gas stream such as
fission product tritium and krypton-85. Steps to remove
one off-gas constituent usually relate to others; such
relations will be indicated where observed.
6-4
-------
Reprocessing Facility Off-Gas
Treatment Flow Diagram
Off-gas from Dissolver off-gas Dissolver off-gas No. 1 Iodine
Dissolvers Condenser Knock-Out Pot Scrubber
Collected
Vessel off-gas flow
NO2 NO2 Absorber W Vessel off-gas Vessel off-gas
Absorber ^- Eductor ^ Condenser ^*- Knock-Out Pot
Column
No. 2 Iodine Heater Off-gas Iodine
Scrubber ^*" Adsorbers and ^~ Blowers
Filters
Figure 6-2
-------
6.1.1 Process off-gas condensation
Gas streams from both the dissolver and composite vessel
off-gas systems contain significant amounts of water
vapor. This is condensed in the DOG and VOG condensers,
allowing the dried gas stream to continue and condensate
to be removed in a knock-out pot. The condenser also
provides a decontamination factor. Particulates may be
trapped on the wet tube faces and be carried off in the
condensate. In normal conditions, a DF for particulates
of 100 or greater may be available from the condenser
alone, though this varies considerably with operating
conditions and type of activity; it is therefore not
claimed for regulatory purposes. Condensers are not seen
as a removal system for carbon-14, as most of it is gaseous
after exposure to the oxidizing environment of the dissolver.
6.1.2 Removal of radioiodine from off-gas
There are two systems specifically designed to remove
residual, fission product iodine from the off-gas stream
at the BNFP Separations Facility. A third method, called
the lodox process, has been studied at Oak Ridge National
Laboratory ' and considered for use at BNFP. It is
currently considered unsatisfactory for use at the reprocess-
ing plant, though it is a potential control technology.
Finally, after careful review of iodine pathways, a small
fraction of entering radioiodine is expected to volatilize
after off-gas treatment steps in the pre-stack water vaporizer,
a potential limitation to the overall decontamination factor
(4)
(DF). Solutions to ameliorate this condition are proposed
but generally are modifications of present techniques so will
not be separately considered.
6-6
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6.1.2.1 Wet chemical scrubbing
This method employs a scrubbing column and a scrubbing
agent called mercuric nitrate. Both elemental and
organic iodine are complexed by mercuric ion in this
solution approximately 8 M in nitric acid At BNFP, the
DOG stream and certain non-condensible compounds enter
the #1 Scrubber and pass upward through a solution 0.2 M
in mercuric nitrate and 6-8 M in nitric acid. The
exiting stream passes through the NG>2 Scrubber and the
N02 Absorber Eductor and to be combined with the very
high volume VOG stream. This stream passes through the #2
Scrubber where iodine is again removed by reaction with
mercuric nitrate in nitric acid. Each column is ex-
pected to have an iodine DF of 10. (4)
Scrubbing solution is initially charged via the #2
Scrubber. The bottoms from #1- Scrubber are drained to
the Intermediate Level Liquid Waste system periodically,
and it is charged from the bottoms of $2 Scrubber.
The second column is then freshly charged.
This system has only speculative value for carbon
dioxide removal (recall that most carbon will be oxidized
in the dissolver, if not subsequently). It is thought
that the scrubbing solution is so heavily acidic that it
will largely prevent dissolution of CO-/ and consequently
most of the gas will pass out of the system.
6.1.2.2 Dry fixed-bed adsorption
The out-flow of #2 Iodine Scrubber passes a roughing and
a fine filter, then a dry fixed-bed adsorber packed with
silver zeolite (AgZe). AgZe is formed by exchanging
6-7
-------
sodium on zeolite with silver using silver nitrate. It
will react with either elemental or organic iodine. A
fully exchanged AgZe filter will retain 0.09 grams of
iodine per cubic centimeter of bed up to 1 percent break-
(4)
through. The iodine DF is at least 100. Combined wit!
the scrubber, an overall DF for iodine in the Process
4
Off-Gas System of 10 is effected, surpassing the suggest*
factor of 103 (7) for 150 day cooled LWR fuel.
This filter is not seen as a carbon-14 removal system by
itself, though zeolite is known to act as a molecular
sieve for CO-. Physical hold-up may therefore occur, but
this system is used without a purge system when treating
14
iodine. Thus, it cannot of itself trap and retain CO.,.
6.1.2.3 lodox process
An advanced process under development at Oak Ridge
National Laboratories is called the lodox process. It
has not been accepted for use at BNFP or elsewhere, but
experimental results are available and indicate this is
a highly effective system for iodine removal. ' The
off-gas stream is placed in contact with 16-20 M nitric
acid in a bubble-cap scrubbing column, possibly similar
to the one used presently at BNFP for N0_ absorption.
Both organic and elemental iodine are precipitated as
6-8
-------
iodic acid which is collected in the bottom liquids. Ex-
periments in a 6-stage fractionating column indicate de-
contamination factors ranging from 30 in 17 M nitric acid
to 9x10 in 20 M nitric acid. Such high decontamination
factors may be required, especially if more highly burned
LWR fuel, mixed oxide fuel or LMFBR fuel are to be pro-
cessed in a separations facility, or possibly fuel which
has undergone a shorter cooling period.
It is difficult to predict the usefulness of this process
with respect to carbon-14 removal. Lacking more specific
information, this report merely indicates the system for
a potential off-gas treatment, to be considered at the
appropriate time, in keeping with our efforts to analyze
C-14 systems as one part of an integrated off-gas treat-
ment process.
6.1.3 Removal of nitrogen oxides by wet scrubbing
Nitrogen oxides, such as N20, NO, N02, N205 or, more
generally, NO , are released to the cover space of the
A
spent fuel dissolver due to thermal, chemical and radio-
lytic decomposition of nitric acid and nitrates.
6-9
-------
Nitrogen dioxide (N02) is scrubbed from the off-gas at
BNFP by passing the gas upwards through a multi-stage
bubble cap column with water as the scrubbing agent.
Cooling coils remove heat generated by the exothermic
absorption reactions. NO partially reacts with oxygen
to form NO-, which is absorbed with other NO- as nitric
acid. NO- is reduced by a factor of about 10 and NO by
a factor of 4; approximately 31 pounds per hour of NO-
plus NO and 21 pounds per hour of N-0 are discharged.
This process does not significantly reduce carbon-14,
14
assumed to be present as C02, by water dissolution,
probably because the water becomes rapidly acidic with
the H-0 - NO- decomposition reaction. Special considera-
tion will have to be given to removal of N_0, as well as
CO-, in the event cryogenic extraction of noble gases is
required.
6.1.4 Cryogenic distillation for noble off-gas treatment
This concept is discussed in a general manner here, for
it is only a proposed control technology for noble gas
separation at a commercial facility. It has been used
effectively at smaller facilities such as the Idaho
(2)
Chemical Process Plant; this experience is considered
in reports on applicability of cryogenic distillation at
(4)
BNFP- It presently appears that another method,
fluorocarbon absorption, is favored because it is less
sensitive to off-gas impurities that foul a cryogenic
system.
6.1.4.1 Removal of noble gases by cryogenic distillation
This technique capitalizes upon differences in boiling
point of the several off-gas constituents. At tempera-
tures achieved with a liquid nitrogen coolant, the
various gases fractionate as follows:
6-10
-------
Liquid, Solid or Slush Gas
Xe (B.P- = -107°C) N2 (B.P. = -196°C)
Kr (B.P. = -153°C) 02 (B.P- = -183°C)
C02(B.P. = - 79°C) CO (B.P. = -190°C)
H2 (B.P. = -253°C)
(All boiling points are for one atmosphere
cover pressure)
Some constituents of the gas stream are liquified, frac-
tionally distilled and the distillates collected. Typical
purity limitation is encountered due to vapor pressures
of the liquid components,* impurities in the reactor
off-gases from which the liquor is composed and radio-
lytic products formed in the distillation apparatus.
Nevertheless, product gases become separated to a high
degree and they can be stored at a greatly reduced
volume and subsequently released following decay holdup.
They might also be bottled and stored for long-term decay.
The latter alternative provides for nearly zero release
of noble gas, while both processes effectively remove
iodine.
The distillation apparatus are similar in each system re-
viewed. Feed gas is deoxygenated to prevent excessive
ozone formation. It is then dried and chilled in a re-
generative pre-cooler (cold-trap) to remove most high
boiling components which would clog the recovery column
or reduce its efficiency. Catalytic recombination
over rhodium or platinum-palladium surfaces can
* Approximately 0.01 percent of the Kr and iodine and
0.025 percent of the Xe are vented with the carrier
gases.
6-11
-------
reduce elements which foul the cryogenic system, but
a precooling stage is required prior to the distillation
equipment as well. The gas stream then passes, in a
countercurrent fashion, in contact with liquified nitrogen
(LN-) coolant in which all products except nitrogen, ozone,
traces of oxygen and hydrogen, and carbon monoxide are
condensed. The vent gases which now contain very little
Kr-85, are passed through a regenerative precooler and
vented to the atmosphere. The liquid fraction passes to
a separation column where it is fractionally distilled
and the vaporized constituents are removed and held
separately. Alternatively, the liquified products may
be left as a mixture and stored for decay in a holdup
tank, then released after 45-90 days (the time period is
only for illustration). If bottling is employed, on-site
shielded remote handling facilities must be-available for
the Kr-85 fraction until it is packed in a transfer cask.
A further design feature on some separation columns is
a recycle line to the feed gas holdup tank for any occluded
or entrained radioactive species.^) The cryogenic
apparatus is packaged in a positive pressure inert
atmosphere to prevent leakage hazards.
6.1.4.2 Application of cryogenic distillation to carbon
dioxide removal
The extent that such a system may remove carbon-14 from
the waste gas stream is undetermined, though it will
depend very much on the specific apparatus and process
conditions. Because the cryogenic system requires a
recombiner system for oxygen, it is assumed that most
carbon in the off-gas stream will be oxidized and thus in
a gaseous state. The precooling step should effectively
6-12
-------
remove C02 from the stream to prevent system fouling, but
the high-boiling compounds de-entrained at this step would
be .released. While cryogenic distillation is not itself
judged to be a satisfactory control technology for C-14
for the reasons described on page 3-20, an alternative control
system must be applied in advance of cryogenic noble gas equipment.
6.1.5 Selective absorption of gaseous radwastes into
liquid dichlorodifluoromethane
A general discussion of fluorocarbon absorption as a
gaseous radwaste treatment system and potential system
descriptions for BWR's and PWR's were provided in
Section 3.2.2. It was emphasized in Chapter 3 that this
system cannot currently be considered a complete carbon-14
removal technology providing a stable final form. A
general design for a process applicable to the BNFP
Separations Facility was provided by Murbach, et al.(^)
This design exemplifies a "current", feasible reprocessing
off-gas system without, of course, specifying the nature
of the final stable products.
A fluorocarbon absorption device would probably be placed
in the stream following NO- treatment. The smallest flow-
rate available, with the minimum level of fouling agents,
is at that point. Pre-treatment for residual N02 and
moisture, as well as C02/ is suggested in the BNFP design
to minimize system fouling. Pre-treatment is presently
done with molecular sieves, though more extravagant
systems may be required. As suggested in Chapter 3 ,
allowing any but a small amount of C02 into the fluoro-
carbon system might create more problems than it solves.
6-13
-------
However, firm understanding of these relationships is only
possible utilizing data from a prototypical system.
The process as presently outlined involves pre-treatment,
cooling, absorption, stripping and regeneration of the
solvent in liquid form. Product forms are invariably
gaseous, requiring physical or chemical stabilization, and
the final form is dependent on isolation requirements. A
system of this sort will most probably provide isolation
of radioactive noble gases from a reprocessing plant, '
while decisions regarding its efficacy for other nuclides
await further study. Fluorocarbon absorption is not
presently considered a carbon-14 isolation technology per
se, though its use in an integrated system should surely
be examined as design requirements and constraints become
more spec i fic.
6.2. Process liquid waste and liquid effluent
There are two radioactive liquid waste streams generated
by the operation and maintenance of a nuclear fuel re-
processing facility. These two streams are referred- to
as high-level liquid waste (HLLW) and intermediate-level
liquid waste (ILLW). They are collected, concentrated,
stored for an interim period of time, and then solidified.
High-level liquid waste is defined as the aqueous raf-
finate from the first decontamination cycle of a nuclear
fuel reprocessing facility- This waste stream contains
greater than 99 percent of all the non-volatile fission
products associated with incoming spent nuclear fuel.
The HLLW stream is generated at a rate of approximately
1,200 gallons per metric ton of uranium reprocessed. It
6-14
-------
is then concentrated to between 150 and 300 gallons per
MTU. Following some interim storage period, the HLLW is
solidified as a stable waste product form.
Intermediate-level liquid waste is composed of several
aqueous wastes. These aqueous wastes include solvent wash
wastes, laboratory wastes, floor drainage, and equipment
and facility decontamination wastes. These streams are
collected at one point and concentrated to a pre-deter-
mined concentration. After some period of interim storage
as liquid, this waste is also solidified as a stable solid.
Several of the process unit operations of a nuclear fuel
reprocessing facility generate process condensates. These
operations include both the waste and product concentrators
and the off-gas system condensers. After treatment, this
material is released to the environment as an effluent.
In the case of the Barnwell Nuclear Fuels Plant, treated
process condensates are released to the main process stack
as a vapor.
The treatment processes for liquids usually generate a
terminal storage material and medium. At BNFP, the two
liquid streams will be solidified, and the vaporized
liquid condensates treated as off-gas prior to release.
The latter treatment system was examined in Section 6.1.
These alternatives for liquid waste provide isolation of
nuclides, including carbon-14, from the environment. The
method of process condensate vaporization allows for gen-
eral decontamination, but nothing specific for carbon-14
as a gas. Application of the methods of Chapter 8 will
mitigate this release.
6-15
-------
Chapter 6 References
1. Allied-Gulf Nuclear Services. Barnwell Nuclear Fuel
Plant Separation Facility Final Safety Analysis Report,
Section 4, October, 1973.
2. Bendixsen, C. L. and G. F. Offutt. Rare Gas Recovery
Facility at_ the Idaho Chemical Processing Plant.
United States Atomic Energy Commission, IN-1221,
April, 1969.
3. Alternatives for Managing Wastes from Reactors and
Post-Fission Operations in_ the LWR Fuel Cycle.
Volume II, Section 13.0, United States Energy Research
and Development Administration, ERDA-76-43, May, 1976.
4. Murbach, E. W., W. H. Carr and J. H. Gray, III.
Fission Product Gas Retention Process and Equipment
Design 'Study, Chemical Technology Division, Oak Ridge
National Laboratory, ORNL-TM-4560, May, 1974.
5. Groenier, W". S. An Engineering Evaluation of the
lodex Process: Removal of Iodine from Air Using a
Nitric Acid Scrub in_ a Packed Column. Oak Ridge
National LaboratoryT ORNL-TM-4125, February, 1973.
6. Unger, W. E. et al. Aqueous Fuel Reprocessing
Quarterly Report for Period~Ending December 31, 1972.
Oak Ridge National Laboratory, ORNL-TM-4240.
7. Russell, J. L. and F. L. Galpin. "A Review of
Measured and Estimated Offsite Doses at Fuel Re-
processing Plants". Proceedings of the OECD/IAEA
Symposium on the Management of Radioactive Wastes
from Fuel Reprocessing. Paris, November, 1972.
8. Stephenson, M. J. and R. S. Eby. "Development of the
FASTER Process for removing krypton-85, carbon-14 and
other contaminants from the off-gas of fuel reproces-
sing plants". Proceedings of_ the Fourteenth ERDA Air
Cleaning Conference, August, 1976, (in publication]"!
6-16
-------
CHAPTER 7. PROJECTED CARBON-14 CONCENTRATIONS AND
BEHAVIOR IN NUCLEAR FUEL REPROCESSING
EFFLUENT TREATMENT SYSTEMS
This chapter will analyze the expected carbon-14 concen-
trations, chemical forms and behavior in the effluent
systems of a nuclear fuel separations facility. This in-
formation is needed to exhibit parameters used in design
of an effluent control system. Knowledge of the distribu-
tion and quantity of releases from the several pathways
which carry carbon-14 to the environment allows the de-
signer to choose cost-effective treatment principles and
devices.
As in Chapter 6, the Barnwell Nuclear Fuels Plant (BNFP)
Separations Facility is used to represent fuel reprocessing
plants because detailed information is available. This
facility is designed to recover uranium and plutonium from
spent LWR fuel. Refer to Figure 6-1 for the plant flow-
sheet. Dissolution of the chopped fuel is followed by sol-
vent extraction using tributyl phosphate CTBP) in a hydro-
carbon diluent. The resultant product streams contain
separated uranium and plutonium, and waste streams of high
level, intermediate level and low level liquid wastes.
Finally, there is considerable off-gas containing radio-
active substances to be removed. Many are controlled by
existing systems described in Chapter 6. This chapter
attempts to predict levels of carbon-14 in various stages
of the process so control mechanisms may be designed.
7-1
-------
7.1 Carbon-14 in arriving spent fuel
Used fuel arrives and is placed in the Fuel Receiving and
Storage Pool. The fuel arrives from many power stations,
so the physical storage methods are quite flexible, and
burnup of the fuel varies requiring adjustment of plant
processes for each batch. It is assumed here that fuel
has been utilized to an average burnup of 33,000 MWt-days
per MTHM. The amount of carbon-14 generated in reactor
fuel was computed according to methods and assumptions
presented in Chapter 2. Results, given in units of curies
per gigawatt Celectric)-year, are listed in Table 2-1.
The carbon-14 production rate from fuel irradiation is
estimated to be 21.4 Ci/GWe-yr and it was assumed that
the fuel turnaround is 33.5 MT per GWe-yr, so a rough
estimation of incoming fuel-borne carbon-14 activity is
0.64 Ci/MT of fuel. No reduction of this value is assumed
due to failed fuel losses, negative deviations in neutron
fluxes in the reactor or the 150 day storage delay at the
reactor sites prior to shipment to the reprocessor. No
significant amount of the carbon-14 arriving at the
Separations Facility is assumed to escape to the Fuel
Storage Pool, even with some failed fuel. Therefore, based
on 1,500 MT/year capacity at BNFP, approximately 960 curies
per year of carbon-14 are assumed to reach the shearing-
dissolving step, or head-end, of the plant.
7.2 Carbon-14 and stable carbon in the process pathways
The first step in nuclear fuel reprocessing is shearing.
Fuel elements are mechanically transferred from the spent
fuel pool to the remote process cell in which chopping
occurs. They are chopped into segments 2 to 5 inches
long, allowing hulls, oxide pellets and gases to be
7-2
-------
delivered to the dissolver. Hulls and pellets fall by
gravity, while a sweep-air flow down the shear outlet
chute passes off-gases to the dissolver.
In the dissolver, the oxide pellets are dissolved along
with their impurities. Hulls are lifted from the dis-
solver, scrubbed and the wash solution and off-gas re-
turned to the dissolver. It is assumed for this study
that carbon, in whatever form it resides in the fuel, will
be oxidized to carbon dioxide. Confirmation of this assump-
tion awaits necessary laboratory data and/or actual field
measurements at a reprocessing facility.
In Chapter 2, it was assumed that activation of oxygen-17
in the oxide fuel and of nitrogen-14 present as an im--
purity in the fuel (to the extent of 2d ppm) accounted for
all carbon-14 formed therein. In this report, complete
conversion to a gaseous state is assumed, releasing 0.64
Ci/MT of fuel processed to the dissolver off-gas system.
At BNFP, then, 960 Ci/year needs to be removed from the
off-gas system. Assuming a good dissolution and residence
time of solution in the dissolver, nearly all the C^-14 may
be expected to be released to the dissolver off-gas system.
The C0_ concentration of the DOGS gas stream is assumed to be
essentially that of air. The stream is not dry, however.
In this design, the carbon dioxide concentration is taken to
be 0.0315 percent by volume and the carbon-14 concentration
is 3.6x10 Ci/scf based on a 300 day per year operating
schedule. Other headend designs are possible which would
produce a more concentrated carbon-14 off-gas stream, though
details have not been finalized.
The assumptions used here are based on considerations
lacking C-14 direct measurements. If carbon-14 were carried
7-3
-------
off in the liquid process streams, a small fraction of
that in the dissolver might later volatilize in vessel
overheads. It would be added to the off-gas stream called
the composite VOGS and be entrained in a gas flow of
nearly 3,200 scfm. Also, overheads.from the HLLW off-gas
condenser might also contain a small amount of activity,
which would be added to the composite VOGS to create a
flowrate of 4,400 scfm. The concentration of carbon-14
in this stream would equal the total 960 Ci/year assumed
to reside in the DOGS system; recall that the DOGS and
VOGS combine to form a single stream for final iodine
treatment and release. The CO- concentration is slightly
higher than air in the final stream, however, because sugar
is added in the high level liquid waste concentrator for
denitration and ruthenium suppression, resulting in a con-
siderable (non-radioactive) carbon dioxide contribution
to the off-gas.
For this report, -significant removal of carbon-14 is ex-
pected by treating the flow of the DOGS. It can be seen
at BNFP that in the case of iodine, for example, treat-
ment is applied once to the concentrated DOGS stream and
once to the dilute but possibly contaminated VOGS stream.
While absolute knowledge of carbon-14 contamination levels
in the VOGS awaits measurement, it is felt that decontam-
ination factors of 100 to 1,000 can be achieved by treating
the DOGS stream. It is virtually assured that a last
possible source of carbon-14 volatilization, the HLLW cal-
ciner, will provide a miniscule contribution to the total
off-gas levels of this nuclide.
7-4
-------
Chapter 7 References
1. Allied Gulf Nuclear SErvices. Barnwell Nuclear Fuel
Plant Separation Facility Final Safety Analysis Report,
Section 4, October, 1973.
Stephenson, M.J. and R.S. Eby. "Development of the
FASTER Process for removing Krypton-85, carbon-14 and
other contaminants from the off-gas of fuel reproces-
sing plants". Proceedings of the Fourteenth ERDA Air
Cleaning Conference, August, 1976, (in publication).
7-5
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CHAPTER 8. MODIFIED REPROCESSING PLANT
EFFLUENT TREATMENT SYSTEMS
8.1 Cost estimates for separations facility off-gas
treatment possibilities
In the following analysis, iodine removal is assumed to
come first, followed by NO removal. Next comes C,. removal
X J- *4
and Kr-85 removal. Iodine is removed first so as not to
contaminate the CaCO., while NO removal is a necessary pre-
O X
treatment for C,. and Krypton control
Due to the presence of other radionuclides, notably the high
dose rate from Kr85, the process equipment is enclosed in
process cells. At least two-foot thick concrete walls.
additional Class I structure requirements, and radiation
shielding constitute additional costs not included in the
cost module that has been used throughout the report. Appro-
priate inclusions will be made.
Hot cell costs are sunk to the other radionuclide control
systems which are much more expensive than the one for C,..
They are thus not included in the economic analysis.
As shown in Chapter 7, essentially all of the C-14 that is
released from the fuel reprocessing operation passes through
the dissolver off-gas system. By passing the dissolver off-
gas stream through a caustic scrubbing system similar to those
developed in previous chapters for LWR off-gas treatment, the
desired removal of C-14 can be achieved. The dissolver off-
gas stream at BNFP has a composition essentially the same as
air. It has been estimated that an upper bound flow-rate, at
operating temperature and pressure, of 740 cfm can be en-
countered in the Barnwell DOG stream. This flow-rate is con-
siderably larger than those encountered in LWR systems;
8-1
-------
therefore, a larger scrubbing system is needed. The system
design is outlined in Appendix B.
From Appendix B, it can be seen that by cascading equal size
absorption columns in series, desired removal of C-14 can be
achieved. Due to the amount of CaCO_ generated cartridge
filters will not prove economical. Therefore, it is
assumed that the system contains a backflush filter. As in
Chapter 4, the following cases are defined:
Case I - 90% removal of CO- (1 column)
Case II - 99% removal of CO- (2 columns)
In case II, where more than 1 column is used, additional
pumps are needed. Also, because of the design flowrates of
the liquid and gas entering the scrubber, the system will con-
tain 2 inch, 304 stainless steel piping throughout.
Capital costs for a 740 cfm dissolver off-gas removal
system for C-14
Table 8-1 summarizes the equipment costs for the dissolver
off-gas C-14 removal system. Cost data for this larger
system were obtained from the sources referenced in Chapter 4.
As indicated in Chapter 4, the fabricated equipment costs are
assumed to represent 13.3 percent of the capital cost of the
installed system. Therefore, capital costs of each case are
as follows:
Case I $600,000
Case II 728,000
These estimates do not include:
a) - shielding and other Class I structure requirements
b) - loss of production during installation
8-2
-------
c) - major retro-fit costs which involve changes
to space envelopes
d) - licensing activities and delays.
Item a will be estimated and added to the above capital costs.
These cost items will be in approximately the same cost range
as indicated for reactors in Chapter 4. The cost of NO re-
X
moval is assumed to be borne by the Krypton removal system
because the latter is required by EPA and also needs NO pre-
Ji
treatment. Therefore no costs for NO removal are included in
Jt
the economic evaluation of C,. control in reprocessing plants.
For C02 removal by caustic scrubbing, a generic process cell of
dimensions 12" x 12' x 20' is considered for costing purposes.
Due to the presence of Krypton-85 and other radionuclides, two-
foot thick concrete walls, steel linings and reinforced Class I
structures are required.
The additional unit volume cost, after escalation to 1977, is
$114/ft3 (1)
is $328,000.
$114/ft . The capital costs of the process cell facilities
It is felt that the retrofit costs should be charged off to
the control of Krypton and other radionuclides, because the C,.
subsystem is only a minor process component in the integrated
radionuclide control case. Therefore, the total capital costs
for the two cases are:
Case I - $600,000 + $328,000 = $ 928,000
Case II - $728,000 + $328,000 = $1,056,000
Annual CO^ fixation
The annual operating costs for the 740 cfm system include
labor, chemicals, utilities, maintenance, and replacement.
Maintenance and replacement costs included repair and re-
placement of equipment. For this study, 7 percent of the
8-3
-------
Table 8-1
Fabricated Equipment Costs for Reprocessing Dissolver
Off-Gas Scrubbing System (740 cfm)
Item Cost
1. Off-Gas Blower $ 2,800
2. Absorption Column(s) - Case I 12,000
- Case II 24,000
3. Column Internals
a. Packing - Case I 1,700
- Case II 3,400
b. Gas Injection Support Plates
- Case I (-2) 800
- Case 11(4) 1,600
c. Liquid Distributor
- Case I 400
- Case II 800
d. Wire Mesh 50
e. Wash Down Nozzle 70
4. Mixing Tank 720
5. Agitator 750
6. Chemical Charging Tanks
a. NaOH 350
b. Ca(OH)2 350
7. Recirculation Pump - Case I 1,200
- Case II 2,400
8. Filter Pump 1,200
8-4
-------
Table 8-1 (Continued)
Item Cost
9. CaC03 Backflush Filter Unit $58,000
Total fabricated equipment cost
a. Case I $80,000
b. Case II 97,000
8-5
-------
original capital cost is assumed for these costs. An average
capital cost of $992,000 is assumed for the preceding two
cases. The labor cost assumes one additional staff member at
the qualification level of an operator at $25,000 per man-year.
Chemical costs are assumed to be $2,000 per year with negligible
utility costs.
"Labor
$25,000 x 1.0 = $ 25,000
Maintenance and Replacement
$992,000 x 0.07 69,000
Chemicals 2,006
Fixed Charges 198,000
Annual Costs $294,000
The 20-year present worth factor at 8 percent interest per
year is 9.82. Therefore, the present worth value of the
20 years of annual costs would be 9.82 x $294,000 =
$2,887,000.
Since Barnwell is an older design the radiation protection
standards and guides were much less restrictive at its
inception than those currently required. It is evident
that in future reprocessing plants the DOG flow rates will
be drastically reduced. For this reason a lower flow of
100 cfm for the DOG is also considered, to reflect future
designs and provide an associated range of costs.
Capital costs for a 100 cfm dissolver off-gas removal
System for C-14
Appendix C reflects the design for a caustic scrubbing unit
to treat a 100 cfm DOG flow rate. Once again the following
Cases are defined:
Case I - 90% removal of CO-
Case II - 99% removal of C02
8-6
-------
The system will contain 2 inch, 304 stainless steel piping
throughout, and due to waste volumes generated, only the
backflushable option will be considered. Table 8-2
summarizes the fabricated equipment costs for this system, as
obtained from the sources referenced in Chapter 4. Using
the same procedure as that for the 740 cfm system with a
process cell cost equal to 2/3 of the 740 cfm case, the total
capital costs for each case are as follows:
Case I - $399,000
Case II - 421,000
Annual fixation costs
Using an average installed cost of $410,000 for the above two
cases the annual costs are:
Labor
$25,000 x 1.0 = $25,000
Maintenance and Replacement
$410,000 x .07 $29,000
Chemicals $1,500
Fixed charges $82,000
Annual Costs $137,000
The 20 year present worth factor is
9.82 x 137,000 = $1,345,000
8-7
-------
Table 8-2
Direct Equipment Costs for Reprocessing Dissolver
Off-Gas Scrubbing System (100 cfm)
Item Cost
1. Off-Gas Blower $850
2. Absorption Column(s) - Case I $3,900
- Case II $6,300
3. Column Internals
a. Packing - Case I $240
- Case II $480
b. Gas Injection Support Plates
- Case I (1) $280
- Case II (2) $560
c. Liquid Distributor
- Case I $290
- Case II $290
d. Wire Mesh $30
e. Wash Down Nozzle $50
4. Mixing Tank $500
5. Agitator $650
6. Chemical Charging Tanks
a. NaOH $350
b. Ca(OH)2 $350
7. Recirculation Pump $1,200
8. Filter Pump $1,200
8-8
-------
Table 8-2 (Continued)
Item Cost
9. CaC03 Backflush Filter Unit $17,000
Total fabricated equipment cost
a. Case I $24,000
b. Case II $27,000
8-9
-------
8.2 Effect of integrated control technologies
Other off-gas control systems may be applied at nuclear
fuel reprocessing plants which will have a bearing on
Carbon-14 control. Specifically, control of noble gas fission
products has been proposed using a fluorocarbon absorbent
or a cryogenic distillation device. It was shown in Chapter
3 that these systems presently require pre-treatment to
remove fouling agents such as carbon dioxide. The devices
to accomplish this task are an integral part of the noble
gas control system.
No reliable evidence is available on which to base an
assessment of the cold-trap as a means of CO.., transfer to
another device which yields a solid product form.
It is felt that such a system could be created given the
demand, though none has been designed to date. On the other
hand, it has been shown that another -likely interceptor,
molecular sieves, may be applicable as a C02 pre-treatment
system. Speculation regarding impacts to the combined cost
for carbon-14 and noble gas isolation are therefore summarized:
The total cost of carbon-14 treatment is somewhat
insensitive to scrubber size, and greatly dependent
on the mass of CO^ treated, so eventual costs will
not deviate significantly from estimates for this
reason alone.
Due to the immature nature of these technologies,
with respect to demonstration at commercial facilities,
conservation is appropriate and suggests that computed
credits due to system cost coupling may have limited
demonstrable significance. Conceptually, savings can
be achieved by the use of common hot cell space and
associated equipment as well as sunk costs due to the
sharing a NO removal system.
8-10
-------
Chapter 8 References
1. J. T. Long, Engineering For Nuclear Fuel Reprocessing,
Gordon and Breach Science Publishers, New York, 1967.
p. 933.
8-11
-------
CHAPTER 9. WASTE MANAGEMENT OPTIONS
FOR CARBON-14 PRODUCT FORMS
91 Introduction
The preceding chapters have addressed technologies and
costs associated with the control and capture of carbon-
14. The next logical question is the disposition of the
final carbon-14 waste product form.
The criteria and regulations relative to waste management
of light water reactor fuel cycle wastes have yet to be
formulated. Nonetheless, some projections as to the
nature of the operations and costs can be made based on
present waste management trends.
9.2 Disposal
There appear to be two major options for the disposal of
captured C-14. These options are shallow-land burial and
deep geological emplacement. There is a marked difference
in cost between these two methods. Future regulations
based on health, safety, and environmental evaluations will
dictate which disposal method must be utilized.
9-3 c-14 product form and package
Carbon-14 is captured as calcium carbonate by filtration.
Two filtration options have been examined. The first
option is to collect the calcium carbonate cake on dis-
posable filter cartridges. The second option is to collect
it on an etched disc filter which can be backflushed.
9-1
-------
In the first option, the loaded filter cartridges are
handled as solid waste and are disposed of by being con-
creted in 55-gallon drums. In the second option, the disc
filters are backflushed and the resultant slurry is incor--
porated into concrete by a radwaste solidification unit.
The concrete matrix for the calcium carbonate is then
packaged in 55-gallon drums.
No acute radiological hazard will result from exposure to
carbon-14 in the packaged product, though it is assumed
handling will be done remotely prior to concrete fixation.
Estimates of stable carbon to carbon-14 ratios (expressed
as ratios of stable carbon atoms (Ng) to radioactive carbon
atoms (N^) in the product material) are summarized below:
K
BWR (9.0 Ci/year, 7968 g-mole/year stable carbon)
--= 5.5 x 104
R 14 -5
mole fraction C=1.8xlO
PWR (3.0 Ci/year, 398 g-mole/year stable carbon)
Nc 3
s.= 8.2 x 10
NR .. _4
mole fraction C = 1-2 x 10
Separations Facility - 740 cfm process rate
(960 Ci/year, 1.48 x 10 g-mole/year stable carbon)
NS -3
= 9.6 x 10J
NR
14 -4
mole fraction C = 1.0 x 10
Separations Facility - 100 cfm process rate
(960 Ci/year,- 1.99 x 104 g-mole/year stable carbon)
NS 3
= 1.29 x 10
NR
14 -4
mole fraction C = 8.0 x 10
9-2
-------
9 . 4 BWR waste management
9.4.1 Waste volumes and cost calculations for BWR's
Option A - Disposable cartridge filters
Case 1. Surface dose <200mR/hr.
Assumes :
- $0.40/gal concretion cost
eighteen cartridge filters per drum
300 operating days per year
1,016 drums of concreted filters per year
a final radwaste product density of 100 Ibs/ft
1600 Ibs shielding/42000 Ibs payload per truck
in shipment to disposal sited)
- $2.13 per 100 Ibs load
500 miles to disposal site
disposal costs of $1.30 per cubic foot for shallow-
land burial (1)
disposal costs of $24.50 per -rectilinear cubic foot
for deep geological emplacement (D
new 55-gal drum are $15
concretion waste containers (drums) , transportation,
and disposal are the significant costs
no other radionuclide present
The calculations are as follows :
concretion cost: $0.40/gal x 1016 drums /yr x 55 gal/drum
$24,000 per year
cost of drums -
1,016 drums/yr x $15/drum = $15,200 per year
cost of transportation -
(1600 Ibs shielding + 1,016 drums/yr x 750 Ibs/drum)
x $2.13/100 Ibs = $16,300 per year
9-3
-------
cost of disposal (shallow land burial) -
1,016 drums/yr x 7.5 ft3/drum x $1.30/ft3 = $9,900 per year
total annual waste management charges -
concretion - $22,400
drums - 15,200
transportation - 16,300
disposal - 9,900
$64,000 per year
Assuming a 30-year life at 8 percent interest, the present
worth value equals
11.26 x $64,000 = $720,000
If it is determined that shallow land burial is not an
acceptable means of disposal for long-lived isotopes such
as C-14, the cost of disposal becomes:
cost of disposal (deep geological emplacement) -
1,016 drums/yr x 12 ft3/drum* x $24.50 = $299,000
As can be seen in the case of deep geological emplacement,
the disposal costs greatly exceed all other operational
costs and the total waste management charges become:-
concretion - $ 22,400
drums - 15,200
transportation - 16,300
disposal - 299,000
$353,000 per year
Again, assuming a 30-year life at 8 percent interest, the
present worth value equals
11.26 x $353,000 = $3,975,000
* Note; The volume of a 55-gal drum is 7.5 ft but the
rectilinear space required to store it is 12 ft
9-4
-------
Case 2. Surface dose rate >200 mR/hr
concretion cost of $0.60/gal
- disposal costs of $3.20/ft3 for shallow land burial
- shielding weight of 39,500 lb/42,000 Ib of waste
other assumptions as in Case 1
cost of concretion: $0.60/gal x 1,016 drums/year
x 55 gal/drum = $33,500
cost of transportation = cost of transportation of wastes
+ cost of transportation of shielding
Waste weight
1016 drums/yr x 750 Ibs/drum = 762,000 Ibs/yr
Shielding weight -
762,000 Ibs waste ° = 717,000 Ibs
Transportation Cost:
(762,000 + 717,000)lbs. x $2.13/1001bs = $31,500 per year
Cost of disposal:
1016 drums/yr x 7.5ft3/drum x $3.20/ft3 = $24,400/year
Total annual waste management charges
concretion $33,500
drums 15,200
transportation 31,500
disposal 24,400
$105,000 per year
Present worth value
11.26 x $105,000 = $1,182,000
Cost of disposal (deep geological emplacement) : $299,000
(as in Case 1)
concretion $ 33,500
drums 15,200
transportation 31,500
disposal 299,000
$379,000
Present worth value:
11.26 x $379,000 = $4,268,000
9-5
-------
Option B - Backf lushable etched disc filters
Case 1. Surface dose rate <200mR/hr
Assumes :
Solidification at $0.40/gal (increase in utilities
and labor at radwaste solidifier)
300 operating days per year
a final radwaste product density of 100 Ibs/ft
42,000 Ibs payload per truck shipment to disposal
site
- $2.13 per 100 Ibs load
500 miles to disposal site
disposal costs of $1.30 per cubic foot for shallow-
land burial
disposal costs of $24.50 per rectilinear cubic foot
for deep geological emplacement
new 55-gal drums are $15 each
waste containers (drums), transportation, and dis-
posal are the significant costs
at a 99 percent recovery of the incoming CO- ,
1,410 Ibs of CaCO, are filtered per year
,}
the filters must be backflushed with 3 gallons of
water each time 2.2 Ibs of filtrate is collected
on the filter
the backflush slurry is incorporated into concrete
at a ratio of 30 percent by weight to obtain a
final radwaste product
1600 Ib of shielding required for 42,000 Ib waste
The calculations are as follows:
pounds per year of radwaste slurry -
(1°) (3) (8'3) lbs of flush solution + 1,410 Ibs
of CaC03 = 17,400 lbs per year
pounds per year of final concrete product -
17'4QQ = 58,000 lbs per year'
-J
9-6
-------
shielding weight required ;( QQQ (58/000) = 220° lbs Per year
number of 55-gallon drums per year -
_ 58 , OOP lbs /year _ = 77 drums
(100 lbs/ft3) (7.5 ft3/drum)
concretion cost: $0.40/gal x 77 drums/yr x 55 gal/drum =
$1700 per year
cost of drums -
77 x $15 = $1,200 per year
cost of transportation -
$2.13/100 Ib x (58,000 lbs + 2,200 lbs) = $1300/year
cost of disposal (shallow-land burial) -
77 x 7.5 x $1.30 = $750 per year
total waste management charges -
solidification and concretion - $1,700
drums - 1,200
transportation - 1,300
disposal - 750
$5,000 per year
Assuming a 30-year life at 8 percent interest, the present
worth value equals
11.26 x $5,000 = $56,000
If deep geological emplacement is used to dispose of the
waste, the disposal costs become
77 drums/year x 12 ft3/drums x $24.50/ft3 = $22,600 per year
The total waste management charges are:
solidification and concretion - $ 1,700
drums - 1,200
transportation - 1,300
disposal - 22,600
$27,000 per year
Again, assuming a 30-year life at 8 percent interest, the
present worth value equals
$27,000 x 11.26 = $304,000
9-7
-------
Case 2: Surface dose rate >200mR/hr
Assume:
- $0.60/gal for solidification and concretion
- disposal costs of $3.25/ft for shallow land burial
- 39,500 Ib of shielding/42000 Ibs of waste
. solidification and concretion $0.60/gal X 77 drums/year
x 55 gal/drum = $2,500
Total transportation costs :
58000 Ibs + ('nn) 58,000 Ibs $2.13 = $2,400
42'000 100 Ibs
cost of disposal:
$3.25/ft3 x 7.5 ft3/drum x 77 drums/year = $l,900/year
Total waste management charges :
solidification and concretion $2,500
drums 1,200
transportation 2,400
disposal 1,900
$8,000
Present worth value:
11.20 x $8000 = $90,000
Deep geological emplacement costs: $22,600 per year
Total waste management charges: $29,000
Present worth value:
$29,000 x 11.26 = $327,000
9.4.2 Waste management cost summary for BWR systems
There are two options for filtration and two disposal cases
for each option. The following tabulated values are the
30-year present worth values.
Option A (Disposable Cartridge Filters)
Case 1 Case 2
(low dose rate) (high dose rate)
Shallow Land Burial $ 720,000 $1,182,000
Deep Geological
Emplacement $3,975,000 $4,268,000
9-8
-------
Option B (Backflushable Filters)
Case 1 Case 2
(low dose rate) (high dose rate)
Shallow Land Burial $ 56,000 $ 90,000
Deep Geological
Emplacement $304,000 $327,000
As can be seen, the cost of waste management can range over
two orders of magnitude depending on which option is chosen.
9.5 PWR Waste management
The total volume of off-gas treated by a PWR carbon-14 col-
lection system is approximately 5 percent of that treated
by a BWR carbon-14 system. This directly affects the volume
of calcium carbonate generated and the amount of waste re-
quiring both transport and disposal. Calculations for a PWR
are based on the same methods and assumptions used in the BWR
case. The number of filters used and amount of backwashed
solution is 5 percent of that found in a BWR. The waste
management cost summary for DWR systems is:
Option A (Disposable Cartridge Filters)
Case 1 Case 2
(low dose rate) (higli dose rate)
Shallow Land Burial $ 36,000 $ 59,000
Deep Geological
Emplacement $199,000 $213,000
Option B (Backflushable Filters)
Shallow Land Burial 3,000 4,500
Deep Geological
Emplacement $15,000 $16,000
9-9
-------
9.6 Spent LWR fuel reprocessing plant waste management
The design and design parameters for a carbon-14 off-gas
cleanup system for nuclear fuel reprocessing facilities
are discussed in Chapter 8. Because of the relatively
large volume of calcium carbonate generated by the
reference system only the backflushed filter system is
viewed as an option. The assumptions for the volume
and cost calculations are essentially the same as listed
for the BWR carbon-14 cleanup system.
For a 740 cfm dissolver off-gas cleanup system 25,900
pounds of calcium carbonate are generated per year. This
requires approximately 35,000 gallons of backflush solution.
The resultant calcium carbonate slurry weighs approximately
319,000 pounds.
Assuming a matrix for the calcium carbonate slurry of 30
percent slurry and 70 percent concrete a final radwaste
product of 1,060,000 pounds per year is generated. At
750 pounds per drum of radwaste, 1,410 drums of concreted
calcium carbonate would be generated each year.
Case 1: Dose rate <200mR/hr
The cost calculations are as follows:
Solidification and concretion costs -
$0.40/gal x 1410 drums/yr x 55 gal/drum = $31,000 per year
drum costs -
1,410 x $15 = $21,200 per year
shielding required -
1,060,000 Ibs x igM.'Siiff = 40,400 Ibs per year
transportation costs -
(40,400 + 1,060,000)Ibs x $2.13 = $23,500 per year
year lOOlbs
9-10
-------
cost of disposal (shallow-land burial) -
L.30/ft3 =
per year
1,410 drums/year x 7.5 ft3/drums x $1.30/ft3 = $13,700
total waste management charges -
solidification and concretion - $31,000
drums - 21,200
transportation - 23,500
disposal - 13,700
$89,000 per year
Assuming a 20-year operating life for a reprocessing
facility at 8 percent interest, the present worth of these
operating costs would be
9.82 x $89,000 = $874,000
If deep geological emplacement is required for the dis-
posal of this waste form, the disposal costs become:
1,410 drums/year x 12 ft3/drums x $24.50/ft3 = $415,OOC
The total waste costs become:
solidification and concretion - $ 31,000
drums 21,200
transportation 23,500
disposal 415,000
$491,000 per year
Again, assuming a 20-year life at 8 percent interest, the
present worth value equals
9.82 x $491,000 = $4,822,000
-------
Case 2: Dose rate >200mR/hr
The cost calculations are as follows:
solidification and concretion costs -
$0.60/gal x 1410 drums /yr x 55 gal/drum = $46,500 per year
shielding required -
1,060,000 Ibs x 42*000 = 997,000 Ibs. per year
transportation cost -
(997,000 x 1,060,000) Ibs x $3 = $43,800 per year
cost of disposal -
1,410 drums/year x 7.5 ft3/drum x $3.25/ft3 = $34,400
per year
Total waste management charges :
solidification and concretion - $46,500
drums - 21,200
transportation - 43,800
disposal - 34,400
$146,000 per year
Present worth value:
9.82 x $146,000 = $1,434,000
Deep geological emplacement costs: $415,000 as in Case 1
Total waste management costs: $527,000 per year
x 9.82 = Present worth value: $5,175,000
In summary, the present worth values of the above cases are:
Case 1 (<200mR/hr) Case 2 (>200mR/hr)
Shallow land burial $ 874,000 $1,434,000
Deep geological
Emplacement $4,822,000 $5,175,000
9-12
-------
For a 100 cfm dissolver off-gas cleanup system, all costs
are a direct ratio of 100 cfm to 740 cfm. These are:
Shallow land burial
Total waste manage-
ment charges
Present worth
Case 1
Surface dose rate
<200mR/hr
- $ 12,000/year
- $118,000
Case 2
Surface dose rate
>200mR/hr
$ 20,000/year
$194,000
Deep geological emplacement
Total waste manage-
ment charges
Present worth
$ 66,000/year
$650,000
71,000/year
$697,000
9-13
-------
Chapter 9 References
1. Croff, A.G., An Evaluation of Options Relative to
the Fixation and Disposal of C-14 Contaminated C0g
and CaC03, April 1976, ORNL TM-5171.
9-14
-------
CHAPTER 10. ECONOMIC COMPARISONS AND SUMMARY
In the preceding chapters of this report, the sources
of carbon-14 in LWR's and fuel reprocessing facilities
have been identified. Also, systems for the removal of
carbon-14 in existing plants and future plants have been
addressed from both a technological and an economic stand-
point. Within existing technology, it is shown that
caustic scrubbing is the most cost-effective alternative for
concurrently removing C-14 from waste-gas streams and leaving
it in a form compatible with permanent disposal conditions
Table 10-1 gives a summary and comparison of costs for a
carbon-14 removal system for BWR's, PWR's and fuel re-
processing facilities. In BWR's the total installation
cost for a scrubbing system with backflushable filters
is greater than one with disposable cartridge filters.
However, upon examination of the waste management costs,
it can be seen that the back-flushable filter scrubbing
system more than pays for itself over a thirty-year plant
lifetime, since these costs are a factor of ten lower than
using cartridge filters. The same can be said for PWR
waste management costs.
Because of the possibility that a recombiner will have to
be installed in a PWR off-gas system, the total capital
costs for a PWR scrubbing system for C-14 removal are on the
order of a factor of four greater than a BWR system and
approaching that of an existing reprocessing facility system.
10-1
-------
It can be seen from Table 10-1 that should both shallow land
burial and deep geological emplacement be deemed acceptable
methods of permanent disposal, shallow land burial is a
factor of ten less expensive than deep geological emplacement.
The relative differences between high and low activity waste
disposal costs become small for deep geological placement when
compared with the magnitude of the costs involved.
In conclusion, it should be reemphasized that the preceding
cost evaluation did not include items like loss of production
during installation, retro-fitting costs when modifications
must be made to the physical plant, and costs incurred from
licensing actions. These factors are deemed to be so
variable, and so often defy prediction, that a fair comparison
of costs could not be made. Nonetheless, modifications and
licensing will require time, labor and materials, and surely
cause some loss of production. The range of costs is presented:
Cost Factors Directly Related to Retrofit
Range $ x 10
Lost Production Revenue 2 to 15
ranging from 1 week to
1 month
Licensing activity costs 0.1 to 1.0
Unusual construction problems 0.05 to 0.5
10-2
-------
BWR
PUR (Note 1)
Reprocessing Plant
Total Capital Costs
90% removal of C-14
99% removal of C-14
Annual CO2 Fixed Costs
Present Worth of Annual
Fixed Costs
Annual Haste
Management costs
- shallow land burial
low activity
high activity
- deep geological
emplacement
low activity
high activity
Present North of Haste
Management Costs
- shallow land burial
low activity
high activity
- deep geological
emplacement
low activity
high activity
Cartridge Filter
5 67,500
5 75.000
5 53,000
5 597,000
? 64,000
J 105,000
$ 353,000
$ 379,000
$ 720,000 (30 yr)
$1,182,000 (30 yr)
$3,975,000 (30 yr)
$4,268,000 (30 yr)
Backflush Filter
$ 128,000
$ 143,000
$ 53,000
$ 597,000
$ 5,000
$ 8,000
$ 27,000
$ 29,000
$ 56,000 (30 yr)
$ 90,000 (30 yr)
$ 304,000 (30 yr)
$ 327,000 (30 yr)
Cartridge Filter
$ 855,000
$ 855,000
$ 257,000
$ 2,894,000
$ 3,200
$ 5,200
$ 18,000
$ 19,000
$ 36,000 (30 yr)
$ 59,000 (30 yr)
$ 199,000 (30 yr)
$ 213,000 (30 yr)
Backflush Filter
$ 855,000
$ 855,000
$ 257,000
$2,894,000
$ 300
$ 400
$ 1,400
$ 1,500
$ 3,000 (30 yr)
$ 4,500 (30 yr)
$ 15,000 (30 yr)
$ 16,000 (30 yr)
Backflush Filter
740cfm
$ 928,000
$ 1,056,000
$ 294,000
$ 2,887,000
$ 89,000
$ 146,000
$ 491,000
$ 527,000
$ 874,000 (20 yr)
$ 1,434,000 (20 yr)
$ 4,822,000 (20 yr)
$ 5,175,000 (20 yr)
lOOcfm
399,000
421,000
137,000
1,345,000
12,000
20,000
66,000
71,000
118,000 (20 yr)
194,000 (20 yr)
650,000 (20 yr)
697,000 (20 yr)
NOTE 1.
TABLE 10.1 SUMMARY AND COMPARISON OF COSTS
The C-14 recovery efficiency expressed here is limited to C-14 recovery from the primary rad-waste gas system.
-------
APPENDICES
-------
Nomenclature
A Cross sectional area of column, ft2-
a Specific Packing Surface, ft2/ft3.
G Gas rate, Ib/ft2-sec.
G' Gas mass flow rate, Ib/hr.
GF Gas flooding velocity, Ib/ft2-sec.
gc Gravatational Constant, 32.2 ft/sec2.
h Height of column, ft.
KGa Mass transfer coefficient, Ib-mole/hr-ft3-atm.
L Liquid rate, Ib/ft2-sec.
L' Liquid Mass flow rate, Ib/hr.
N Ib-moles of desired gas transferred per hour.
^PLM kog mean partial pressure drive, dimensionless
e Porosity (bed voidage), dimensionless
M Viscosity of liquid, centipoise.
PG Density of Gas, lb/ft3.
PL Density of liquid, lb/ft3.
*l> Ratio of water density to that of liquid in column,
dimensionless
-------
APPENDIX A - LWR SCRUBBER SYSTEM DESIGN
It is desired to remove C02 from an LWR off-gas system.
The off-gas essentially has the composition of air and
contains .0315% C02 by volume. It is flowing at 40 cfm.
A packed column is to be designed for the absorption
process, operating at atmospheric pressure and 20°C.
The following definitions, assumptions, and parameters
will be used in the column design:
1. 1-inch Berl saddles will be used as packing.
2. The packing factor F (p) = a/e = 110 for 1-inch Berl
saddles (see reference 2, page 56), where "a" is the
specific packing surface (ft /ft ), and"en is the porosity-
3. A 2 N(8wt%) aqueous sodium hydroxide solution will be
used. From reference 1, p. 3-78, the specific gravity
of a 2 N NaOH solution at 20°C is 1.0869. The density,
P., of the solution is:
LI
PT = 1.0869 x 62.3 ^r = 67-7 ~r.
L ft-5 ftj
4. The average molecular weight of dry air is 28.97 ,, , .
At 20°C (63°F), the density, PQ, of the off-gas will be
= 28'97 ldjJ5l5 x (460 + 32)° R = >Q752 ^
359Ibiol₯ (460+ 68)' R "
5. Let $ = ratio of the density of water to that of the liquid
in the column, so,
* = 170169 = -92'
A-l
-------
6. From reference 4, p. C-26, the viscosity of an 8% NaOH
solution at 20° C is 1.6 centipoise.
System Design
The off -gas flow rate is 40 ft /min. So, the mass flow rate,
G' , is:
G- - 40 i x. 0752 x2in= 180.48 .
Try a liquid mass flow rate, I/ , that is 81 times the gas
flow rate. So,
81 x 180.48 = 14,618.9 i| = 14,618.9 ~ x g^f^ x 7.48
1 hr _^ ..
x - = 26'9
Figure A-l shows the generalized pressure drop correlation for
packed tower design. The abscissa value is
I/
(T ^L,
Now referring to Figure A-l,. for a pressure drop of .25 inches
of water/ft, of packing which is sound column design, the
ordinate value is
so,
G - = .0638 - = 229.68
2
ft-sec ft-hr
The diameter of the column will be:
180.48 x 1^ = i o f t
2-29.68 X *) lt0 ft-
From Reference 3, p. 74, KQa s 2.25 Ib-mole/hr-f t3-atm
A-2
-------
CM
>
u>
o
en
'4.2T1
-------
From Reference 2, p. 55,
N
V " h A AP~
LM
where'N = Ib-moles CO- transferred/hr
A = cross sectional area of the column
AP = log mean partial pressure drive.
Liri
The amount of CO- entering the absorber/hr.is
180.48 ^ (.000315) ., -oc
hr Ib-moles
(.0752 1* ) (359 ||L\(||0 + 68\
\ f 3/ \ mole/ \460 + 32/
hour
\ /ocq ££ \ |^t>u -r ba\
)/ l-3-3^ m^l^l 1 /I cn J. -50 I
ft'
For 90% removal of CO- at 1 atm operating pressure
AP = .000315 - .0000315
LM ln/.000315 4
.0000315J
CO- transferred
For 90% removal *$> N = .9(.00196) = .001766 Ib-moles
hour
The cross-sectional area of the column is
A = \ (I)2 = .7854 ft2.
The height of the column is
, _ _ .001766 _ = 8 12 ft
n (2.25) (.7854) (.000123)
The residence time of the liquid in the column packed with
1 inch Berl saddles (e = .78) is
(.7854 ft2 x 8.12 ft x .78)7/26.9 2|i x ?>4gfgal)° 1.38 minutes.
Next the result is checked for flooding velocity. From Figure A-l,
at flooding F(G2)= .0062. So,
.0062 = G2 x .68 =$>G^ = .095
A . U O -^ \J - . v s ^ ^
ft -sec
A-4
-------
Now,
.0638
x 100 = 67.2
.095
So, operation is at 67-2% of flooding, which is sound column
design-.
Now, if 99% removal of CO- is desired
_ .000315 -.00000315 _ nnnnfi77
-- .000315 " -- -0000677
N = . 99(. 00196) = .00194
.00194 _ _
2.25(.7854) (.0000677) ~ 16'22 ft'
The residence time of the liquid in the column is about
twice that for 90% removal since the column is about
twice as tall.
The column is operating at 67.2% of flooding.
A-5
-------
Table A-l
2
Desired CO Liquid Gas Column Column Residence Operational
Removal Flow Rate Flow Rate Diameter Height Time % of Flooding
90% 26.9 gpm 40 ft3/min 1 ft 8>.12 ft 1.38 min 67.2%
(12 inches)
99% 26.9 gpm 40 ft3/min 1 ft .16.22 ft 1.38 min 67.2%
(12 inches)
>
-------
References
(1) Perry, R. H., Chilton, C. H., ed., Chemical Engineer's
Handbook, Fifth Edition, McGraw-Hill Book Co., N. Y.,
1973.
(2) Eckert, J. S., "Design Techniques for Sizing Packed
-Towers," Chemical Engineering Progress, Vol. 57, No. 9,
September 1961.
(3) Eckert, J. S., "How Tower Packings Behave," Chemical
Engineering, April 14, 1975.
(4) Fleming, R., A Compilation of Physical and Chemical
Properties of Materials and Streams Encountered in the
Chemical Process Department, Manual HW-57386, General
Electric Company-Hanford Atomic Products Operation, 1958,
A-7
-------
APPENDIX B - REPROCESSING DISSOLVER OFF-GAS
SYSTEM DESIGN (CATEGORY I)
It is desired to remove C0_ from a fuel reprocessing plant
dissolver off-gas system. The off-gas has the composition
of air and contains .0315% CO- by volume. It is flowing
at 740 cfm. As in Appendix A, a packed column is to be
designed for the absorption process, operating at atmos-
pheric pressure and 20aC.
The same definitions, assumptions, parameters, and refer-
ences outlined in Appendix A will be used.
System Design
The flow rate of the off -gas (air) is 740 cfm. So,
G' =740 x .0752 x = 3339 .
mm r. j nr nr
As in the smaller column design in Appendix A, try an L'
that is 81 times G7.
81, 3339=270,459 g ^270,459 if x ^-^ x l
As before,
% (3J1 -2-7
and
Ib
G = 229.68
ft2-hr
B-l
-------
The column diameter is:
D =
i229.68 A IT,
Again,
K^a = 2.25.
3339 1]'- 4.3 ft.
The amount of CO- that enters the column/hr is:
3339 (.000315) = >036 Ib-moles
(.0752)(359)
For 90% removal of C02:
= .000123.
N = .9 (.036) = .0324 lb"m°les
nr
A = J x (4.3)2 = 14.52 ft2
. _ -0324 _
n ~ (2.25) (14.52) (.000123)
The height to diameter ratio of the column is less than 2.
It should be considerably larger for sound column design.
This can be achieved by design alterations to the column.
Now, by cutting the cross sectional area in half and
doubling the height, the same results (90% removal of C02)
can be obtained.
So,
A = 14252 = 7.26 ft2
h = 16.12 ft.
B-2
-------
Working backwards, the other parameters can be obtained.
= 3.04 ft.
3339 _ Acn n lb _ 100 lb
/7.26 x 4\
\ * /
_
G *55-7- . x .
7'26 ft -hr ft -sec
F(G2) = (.128)2 x .68 = .0111.
From Figure A-l,
L' PGV*~ *-> - L/ /.0752\Js
Q-T ItrrJ = .62 -
L' = 18.6 x 3339 =62,114.
or
62'114-6Hlx 6T^IFX 7'48 X= 114'38
The residence time of the liquid in the column packed with
1 inch Berl saddles (e = .78) is:
7.26 ft2 x 16.28 ft x .78/ (114.38 gjL x 7^4fgaJ = 6.03 mi
Checking for flooding velocity, from Figure A-l at flooding
F(G2) = .033 = G2 x .68 =^> G., = .22 i^ .
F F ft2-sec
So,
.128 _ ,
7220 ~ -581'
B-3
-------
The column is operating at 58.1% of flooding, which is sound
column design.
As can be seen in Appendix A, 99 percent removal of CO-
can be obtained by increasing the height of the column, or
increasing the diameter and liquid-gas flowrate ratio. A
height of 16 feet is about the maximum^ desired for this
application due to room size constraints at the reprocessing
facility. Also, a column of 3 feet in diameter is about
the largest desired for a column height of 16 feet. An
alternative to adding height to the column would be to
cascade additional columns in series. By adding an identical
column in series with the first, 99 percent removal could be
obtained. In summary, the design yields:
Size of column
Air flowrate
Liquid flowrate
Number of columns
3 ft. in diameter
16.12 ft. high
740 cfm
114.38 gpm
90% CO- removal - 1 column
99% CO- removal - 2 columns
B-4
-------
APPENDIX C - REPROCESSING DISSOLVER OFF-GAS
SYSTEM DESIGN ( CATEGORY II)
It is desired to remove CO- from a fuel reprocessing plant
dissolver off-gas system. The off-gas has the composition
of air and contains .0315% CO- by volume. It is flowing
at 100 cfm. As in Appendix A, a packed column is to be
designed for the absorption process, operating at atmos-
pheric pressure and 20° C.
The same definitions, assumptions, parameters, and refer-
ences outlined in Appendix A will be used.
System Design
The flow rate of the off-gas (air) is 100 cfm. So,
G' - 100 x .0752 j x . 451
As in the column design in Appendix A, try an L '
that is 81 times G'.-
01 >,ci ic c-ai lb _^ >* COT- lb ! ft 7
81 x 451 = 36,531 ^ ^> 36,531 ^ x 67>? lb x
As shown in Appendix A,
L'
PL/ - 2-7
and
lb
G = 229.68 iii = .0638
ft2-hr ft^-sec.
C-l
-------
The column diameter is:
n - f 451 1
D ~ \229.68 X tr\
Again,
K-, O OC
,-id ^ « ^ 3 «
The amount of C02 that enters the column/hr is:
451. (.000315) _ nn,Q Ib-moles
(.0752)(359)(||4) hr
For 90% removal of C02:
AP = .000123.
N = .9C.0049) = .0044 ^-moles Co? transferred
A = x (1.58)2 = 1.96 ft2
h = .0044 _ = R
n (2.25) (1.96) (.000123) *'
The residence time of the liquid in the column packed with
1 inch Berl saddles (e = .78) is:
1.96 ft2 x 8.11 ft x .78/ ( 67.3 Jji x l ^ ) = i.38 min.
Checking for flooding velocity, from Figure A-l at flooding
F(G ) .0062 = Gp x .68 =^> G .095 i^
* ft -sec
So,
.0638 _ c_,
.095 ~ b/"1
C-2
-------
So, operation is at 67.2% of flooding, which is sound column
design.
Now, -if 99% removal of C0_ is desired
.00000315
N = . 99 (.0049) = .00485
_ .00485 _ ,..
2.25 (1.96) (.0000677) = ^
-
*"
The residence time of the liquid in the column is about
twice that for 90% removal since the column is about
twice as tall.
The column is operating at 67.2% of flooding.
03
-------
Table C-l
*\
Desired CO Liquid Gas Column Column Residence Operational
Removal Flow Rate Flow Rate Diameter Height Time % of Flooding
90% 67.3 gpm 100 ft3/min l-58 ft 8.11ft 1.38 min 67.2%
(19 inches)
99% 67.3 gpm 100 ft3/min 1.58 ft 16.24 ft 1.38 min 67.2%
(19 inches)
o
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