TECHNICAL NOTE
ORP/TAD-76-3
PUBLIC HEALTH CONSIDERATIONS OF CARBON-14
DISCHARGES FROM THE LIGHT-WATER-COOLED NUCLEAR
POWER REACTOR INDUSTRY
THE UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RADIATION PROGRAMS
JULY 1976
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Technical Note
ORP/TAD-76- 3
PUBLIC HEALTH CONSIDERATIONS OF CARBON-14
DISCHARGES FROM THE LIGHT-WATER-COOLED NUCLEAR
POWER REACTOR INDUSTRY
by
T. W. Fowler
R. L. Clark
J. M. Gruhlke
J. L. Russell
July 1976
Technology Assessment Division
U.S. Environmental Protection Agency
Office of Radiation Programs
Washington, D.C. 20460
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PREFACE
The Office of Radiation Programs of the Environmental Protection
Agency carries out a national program designed to evaluate public
health impact from ionizing and nonionizing radiation, and to promote
development of control necessary to protect the public health and the
environment. This report of current findings on public health consid-
erations of carbon-14 discharges from the light-water-cooled nuclear
§ower reactor industry was prepared to provide information to Federal,
tate, and local agencies as well as the public. Readers of this
report are encouraged to inform the Offtce of Radiation Programs of
omissions or errors.
David S. Smith
Director
Technology Assessment Division (AW-459)
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ACKNOWLEDGEMENT
The authors gratefully acknowledge the contribution of
C. B. Nelson who developed the modified Machta world-wide
carbon-14 code and assisted in the preparation of the
description of this code presented in this report.
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TABLE OF CONTENTS
PAGE
1. INTRODUCTION 1
2. CARBON-14 PRODUCTION IN LWR'S 2
2.1 Carbon-14 Production in the Fuel 3
2.2 Carbon-14 Production in the BWR Coolant 4
2.3 Carbon-14 Production in the PWR Coolant 4
2.4 Total Carbon-14 Production in a LWR 5
3. SOURCES AND TREATMENT OF CARBON-14 IN LWR'S 7
3.1 Gaseous Source Terms for BWR's 7
3.2 Liquid Source Terms for BWR's 8
3.3 Gaseous Source Terms for PWR's 8
3.4 Liquid Source Terms for PWR's 12
3.5 Source Term Summary 14
3.6 Carbon-14 Control for BWR's and PWR's 14
4. CARBON-14 AT LWR FUEL REPROCESSING PLANTS 17
4.1 Behavior of Carbon in the Fuel Reprocessing Plant 17
4.2 Control Systems at LWR Fuel Reprocessing Plants 19
5. ENVIRONMENTAL TRANSPORT OF CARBON-14 22
5.1 Local Transport 22
5.2 World-wide Transport 22
6. DOSIMETRY FOR CARBON-14 DIOXIDE 24
6.1 Critical Organ Method to Estimate Local Short-
Term Dose Equivalent Rates 24
6.2 Specific Activity Method to Estimate World-wide
Long-Term Dose Equivalent Rates 28
7. CARBON-14 DOSE EQUIVALENT RATES AND HEALTH IMPACT 32
8. SUMMARY 36
9. REFERENCES 38
APPENDIX 1. WORLD-WIDE CARBON-14 TRANSPORT MODEL 44
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LIST OF TABLES
TABLE 1. PRODUCTION OF CARBON-14 IN LIGHT-
WATER-COOLED REACTORS
TABLE 2. BOILING WATER REACTOR CARBON-14
SOURCE TERMS
TABLE 3. PRESSURIZED WATER REACTOR CARBON-14
SOURCE TERMS
TABLE 4. AIR AND CARBON DIOXIDE FLOW RATES
IN THE OFF-GAS SYSTEM AT BARNWELL
TABLE 5. CARBON-14 ADULT DOSE EQUIVALENT CONVERSION
FACTORS PER UNIT INTAKE
TABLE 6. CARBON-14 ADULT DOSE EQUIVALENT RATE CONVERSION
FACTORS PER UNIT AIR CONCENTRATION
TABLE 7. CARBON-14 SPECIFIC ACTIVITY DOSE EQUIVALENT
RATE CONVERSION FACTORS
TABLE 8. MAXIMUM ANNUAL CARBON-14 DOSE EQUIVALENT
RATES TO INDIVIDUALS AT LWR FACILITIES
TABLE 9. LISTING OF MODIFIED MACHTA WORLD-WIDE
CARBON-14 TRANSPORT COMPUTER CODE
TABLE 10 DEFINITION OF SYMBOLS USED IN THE WORLD-WIDE
CARBON-14 TRANSPORT COMPUTER CODE
TABLE 11 SAMPLE INPUT DATA FOR THE WORLD-WIDE CARBON-14
TRANSPORT COMPUTER CODE
TABLE 12 CASE 1. WORLD-WIDE COMMITTED POTENTIAL HEALTH
EFFECTS FROM CARBON-14 FOR THE U.S. LWR NUCLEAR
POWER INDUSTRY
TABLE 13 CASE 2. WORLD-WIDE COMMITTED POTENTIAL HEALTH
EFFECTS FROM CARBON-14 FOR THE U.S. LWR NUCLEAR
POWER INDUSTRY
PAGE
6
9
13
21
26
27
31
33
45
50
54
56
57
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1. INTRODUCTION
Carbon-14 (C-14) is produced in nuclear power reactors by
a variety of nuclear Interactions. Any discharges of carbon-14
to the atmosphere can be considered as contributions of a
permanent contaminant to the world-wide environment because of
the long life of this radionuclide. Magno ejt al_., (1) and other
authors (2,3,4,5,6,7) have recently published papers estimating
the discharges of carbon-14 from the light-water-cooled reactor
(LWR) power industry and the impact of these discharges on the
environment and public health. It has been estimated that the
100 year population dose commitment per gigawatt-year is a
factor of 30 greater than for krypton-85 (1).
The potential environmental impact of carbon-14 was not
considered during the early development of the LWR. Some of the
influencing factors include:
a. Carbon-14 is not a fission product of significance
nor is it a significant activation product in structural and
shielding materials.
b. The capture cross-section of carbon-13 is low (0.9 mb)
and the radioactive half-life of carbon-14 is relatively long
(5,730 years (8)). Thus carbon-14 activity in nuclear reactors
is produced in small quantities.
c. The major production of carbon-14 in the fuel results
from the (n, p) reaction with nitrogen-14 which is present as
an impurity in the fuel.
d. The major production of carbon-14 in the coolant
results from the (n, alpha) reaction with oxygen-17 which is
only present in its natural abundance of 0.037%.
For these reasons it appears likely that no comprehensive analysis
was undertaken to determine the impact of carbon-14 from the nuclear
power industry; however, environmental measurements had been made by
Federal agencies in connection with atmospheric nuclear weapons
testing (9).
This paper includes estimates of carbon-14 production in reactors
and analyses of carbon-14 behavior in various waste treatment systems
at both reactors and spent fuel reprocessing plants. Environmental
transport models and carbon-14 dosimetric models are briefly reviewed
to ascertain some probable errors in estimating the impact of carbon-14
on man and the environment. To the extent possible, this report pro-
vides an analysis of current findings and projects what work must be
performed to provide answers to questions concerning the need for the
control of nuclear power sources of this environmental contaminant.
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2. CARBON-14 PRODUCTION IN LWR'S
Essentially all of the carbon-14 produced in LWR's results
from the following two neutron Induced reactions:
Thermal Neutron Cross Natural Abundance
Reaction Section (2200 m/sec) of Target Element
nitrogen-14 (n, p) carbon-14 1.81 barns (1) 99.635% (10)
oxygen-17 (n, a) carbon-14 0.24 barns (1) 0.037% (10)
Other neutron induced reactions which produce carbon-14 in LWR's
but at levels that are insignificant compared to the two above
because of abundance and/or cross sections are:
Thermal Neutron Cross Natural Abundance
Reaction Section (2200 m/sec) of Target Element
carbon-13 (n, y) carbon-14 9E-4 barns*(l) 1.108%
nitrogen-15 (n, d) carbon-14 2.4E-7 barns (11) 0.365%
oxygen-16 (n, He-3) carbon-14 99.759%
The production of carbon-14 by fission is negligible (U-235 fission
yield is 1.7E-6 (12)) by comparison to that produced by the two
major neutron induced reactions. The reactions of neutrons with
nitrogen-14 and oxygen-17 will be taken in this report as giving
adequate estimates of the total production of carbon-14 in the fuel
and 1n the coolant at both BWR's and PWR's.
The activation equation used to calculate the production of
carbon-14 1n LWR's is as follows:
A = N+o (l-e"xt) x (1 C1/3.7E+10 dis/sec)
where A = produced C-14 activity in curies
N = target atoms
$ = thermal neutron flux
a = thermal neutron cross section ,
A = decay constant for C-14 in years"
t = Irradiation time in years
For \ = 1.2E-4 year"^ and t = 3 years, the activation equation is
A = (9.81E-15) N
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2.1 Carbon-14 Production in the Fuel
The activation calculation 1s based on the target atoms in a
fuel loading of 33.5 MTHM and a three year exposure period. The
33.5 MTHM fuel loading produces a nominal electric power output
of 1 GWe-yr for a burnup of 33,000 MWfdays/MTHM and a thermal
efficiency of 33%. Carbon-14 is calculated to be produced at the
rate of 4 Ci/GWe-yr in the fuel by the (n, a) reaction on 0-17
and 18 Ci/GWe-yr by the (n, p) reaction on N-14. The data base
used to calculate these production rates in the fuel are discussed
1n the following paragraphs.
N (target atoms)
For 33.5 MT of uranium, there is 38 MT U02 containing 4.5E+6
grams of oxygen. Using a natural abundance of Q£37% for 0-17, there
is 1.6E+3 grams or 5.9E+25 atoms of O17 in the fuel loading
[N(0-17) = 5.9E+25].
Nitrogen is present in the fuel interstices as an impurity and
thus can vary significantly. For the purposes of this estimate,
twenty ppm (by weight) is the assumed amount of nitrogen present as
an impurity in the fuel (7). Therefore in a 33.5 MTHM fuel loading,
there is 7.6E+2 grams nitrogen and 3.26E+25 atoms of N-14 in the fuel
[N(N-14) = 3.26E+25].
4 (average thermal neutron flux)
o
An average thermal neutron flux of 5E+13 n/cm -sec for the fuel
is assumed in this report (13,14).
a (thermal neutron cross section)
For estimates of the production rate of carbon-14 in the fuel,
consideration of the thermal neutron cross section at 2200 m/sec
alone would result in high production rates since the cross sections
for both reactions of interest varies as 1/v. Therefore, the
'previously presented cross sections at 2200 m/sec were multiplied by
0.6 to correct for the energy dependence of the thermal neutron cross
section and the spectrum or thermal neutrons (13,14) [a (N-14) =
1.1E-24 cm2 and a (0-17) = 1.4E-25 air].
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2.2 Carbon-14 Production In the BWR Coolant
The volume of coolant in the BWR/6 1s 1,872 cubic feet at
1062 psia and 540°F (15). The specific volume of water at these
temperature and pressure conditions is 0.0215 cubic feet per
pound (16). Therefore, there is 39.5 MT of water in the BWR/6
core. The thermal power level for the BWR/6 is 3579 MWt which is
equivalent to a nominal electric power output of 1.18 GWe for a
thermal efficiency of 33%. A one year exposure period is used
to calculate 8.9 Ci/GWe-yr in the BWR coolant by the (n, a)
reaction on 0-17 and 0.26 Ci/GWe-yr by the (n, p) reaction on
N-14. The data base used to calculate these production rates in
the BWR coolant are discussed in the following paragraphs.
N (target atoms)
For 39.5 MT of water, there is 4.6E+26 atoms of 0-17
[N(0-17) = 4.6E+26]. No data could be found on the concentration
of nitrogen dissolved in the coolant. However, since nitrogen
impurities in the fuel proved to be the greatest source of
carbon-14 production there, it is concluded that the production of
carbon-14 by the reactions of neutrons on nitrogen-14 should be
examined. One ppm (by weight) of nitrogen as an impurity in the
water is assumed (17). One ppm of nitrogen in the coolant equates
to 39.5 grams of nitrogen and 1.69E+24 atoms of nitrogen-14 in the
BWR coolant [N(N-14) = 1.69E+24].
4> (average thermal neutron flux)
The simplifying assumption is made that the average thermal
neutron flux in the fuel and coolant are equal. Therefore, an average
thermal neutron flux of 5E+13 n/cmz-sec in the coolant is assumed in
this report.
a (thermal neutron cross section)
The cross sections used to calculate the carbon-14 production
rate in the fuel are used [a (N-14) = 1.1E-24 cm2 and a (0-17) =
1.4E-25 cm2].
2.3 Carbon-14 Production in the PWR Coolant
The volume of coolant in the core of the PWR is calculated to
be 685 cubic feet using the effective cross section flow area, of
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the core (54.8 ft2) and the core height of active fuel (12.5 ft) (18).
The average temperature in the core coolant is 588°F and the
operating pressure is 2235 psig. The specific volume of water
at these conditions is 0.0226 cubic feet per pound (16). Therefore,
there is 13.7 MT of water in the PWR core. The thermal power level
for the chosen PWR (18) is 3473 MWt which is equivalent to a
nominal electric power output of 1.146 GWe for a thermal efficiency
of 33%. A one year exposure period is used to calculate 3.2 Ci/GWe-yr
in the PWR coolant by the (n, a) reaction on 0-17 and 0.09 Ci/GWe-yr
by the (n, p) reaction on N-14. The data base for the average thermal
neutron flux in the PWR coolant and the thermal neutron cross sections
are identical to those used for the BWR coolant calculation. The
data base for the target atoms in the coolant is discussed in the
following paragraph.
N (target atoms)
For 13.7 MT of water in the PWR coolant, there is 1.6E+26 atoms
of oxygen-17 [N(0-17) = 1.6E+26]. One ppm (by weight) of nitrogen
as an impurity in the PWR core coolant is assumed (19). One ppm
of nitrogen in the PWR coolant equates to 13.7 grams of nitrogen and
5.87E+23 atoms of nitrogen in the coolant [N(N-14) = 5.87E+23].
2.4 Total Carbon-14 Production in a LWR
The production rates of carbon-14 are summarized in Table 1
where it can be seen that they agree within a factor of two of those
reported by Bonka e_t al_. (3), Hayes et^ al. (12), ERDA (20), and
Kelly et^ al_. (7). Nitrogen impurities Tn" the fuel is shown to be
the greatest source of production of carbon-14 in the fuel. Reactions
on oxygen-17 is shown to be the greatest source of production of
carbon-14 in the coolant. Production rates for the BWR and PWR
coolant as presented by ERDA (20) and Kelly e_^ al_. (7) are derived
from measured discharges (21,2) and are about two times higher than
the theoretical estimates presented in this report. It is also
noted that the BWR coolant production rate is about a factor of 3
higher than that for the PWR coolant. The higher production rate for
the BWR is probably due to the higher volume of water in the core
where the (n, a) reaction on 0-17 can take place.
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TABLE 1
PRODUCTION OF CARBON-14 IN LIGHT WATER REACTORS
BUR
Fuel
BWR
Coolant
BWR 5
(Fuel Plu«
PWR
Fuel
PWR
Coolant
PWR !
(Fuel Plu«
0-17
N-14
Total
0-17
N-14
Total
>um
> Coolant)
0-17
N-14
Total
0-17
N-14
Total
sum
> Coolant)
This
Report
4
18
22
8.9
.26
9.2
31
4
18
22
3.2
.09
3.3
25
Carbon -V
Bonka
.fitAL (3)
8.4
12.9
21.3
9.9
1.3
11.2
32.5
7.1
12.2
19.3
9.8
1.3
11.1
30.4
\ Production Rat<
Hayes
JitJLL (.12)*
10.9
21.2
32.1
11.5
11.5
43.6
4.0
7.6
11.6
3.3
0.1
3.4
15
; (Ci/GWe-yr)
ERDA-1535
(20)
20**
16
36
17**
6
23
Kelly
-ei-aJ. (7)*
v
2.7
10.9
13.6
16
29.6
2.7
10.9
13.6
6
19.6
* The production rates presented by Hayes et al_. (12) and Kelly et al_. (7)
for 1000 MWt were multiplied by 3.03 (33% therm?! efficiency to roughly present
the values on a per GWe-yr basis for comparison purposes.
i
** Fuel and cladding production rates from ERDA-1535 (20) were added and
identified as a fuel production rate in this table.
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3. SOURCES AND TREATMENT OF CARBON-14 IN LWR'S
3.1 Gaseous Source Terms for BWR's
Carbon-14 may be discharged from all of the following gaseous
release pathways:
1. Main Condenser Air Ejector Off-Gas
2. Turbine Gland Seal
3. Containment Building (Including Drywell) Purge
4. Turbine Building Ventilation
5. Radwaste Building Ventilation
Where possible, measured concentrations of C-14 in exhaust streams have
been used to calculate the annual discharge of C-14 from a nominal 1250
MWe BWR. Where measured concentrations are lacking, the C-14 average
reactor coolant concentration determined at Oyster Creek is used in
conjunction with standard assumptions (22,23,24).
Preliminary data from the Oyster Creek study (22) have indicated
an average C-14 release rate of 0.182 yCi/sec from the air ejector.
When extrapolated on an annual basis (80% capacity factor) for a 1250
MWe BWR, a total of 9.0 Ci/yr of C-14 is estimated to be released. A
measurement of the turbine gland seal condenser exhaust showed the
release rate to be <3E-4 yCi/sec (22). This is equivalent to an annual
release of <0.015 Ci/yr for a 1250 MWe BWR at 80% capacity factor.
For the remaining gaseous release pathways, the average C-14
reactor coolant concentration measured at Oyster Creek 4.0E-6 yCi/ml (22),
is used in conjunction with standard reactor coolant leak rate assumptions
of 500 Ib/hr, 1700 Ib/hr, and 1000 gpd for the containment, turbine
building, and radwaste facility, respectively (23). The leakage to the
radwaste facility is at 1% reactor coolant activity while the others are
at reactor coolant activity. All of the C-14 in these leakages are
assumed to escape to the building atmosphere with subsequent release to
the environment. A sample calculation for the containment purge is as
follows: The assumed leak rate into the drywell and containment building
is 500 Ib/hr which equates to 2000 gallons per day using the approximate
specific volume of 6 Ib/gallon for water. The containment purge source
term is therefore 2000 gal/day x 3785 ml/da/ x 4.0E-6 yCi/ml x 365 day/
year * 1E-6 Ct/nCiJ^0.0088 Ci/yr for a 1250 MWe plant at 80% capacity
(1000 MWe) or .0.0088 Ci/GWe-yr. Table 2 lists the gaseous discharge
pathways and estimated annual discharge rate.
The Oyster Creek data (22) indicates that C-14 is released both as
COg and as other chemical species. At both the air ejector and turbine
gland seal condenser, there was about twice the release rate of ^C as
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C02 as compared to other chemical species. The data of Kunz et al. (21)
for BWR's showed that 95% of the C-14 activity was in the C02 fraction.
3.2 Liquid Source Terms for BWR's
Liquid discharge pathways for C-14 may include:
1. Clean (High Purity) Wastes
2. Dirty (Low Purity) Wastes
3. Chemical Wastes
4. Detergent (Laundry) Wastes
Except for detergent wastes, the average measured C-14 reactor
coolant concentration at Oyster Creek (22) was used in conjunction with
standard assumptions for flow rates and fractions of reactor coolant
activity (23,24) to estimate annual releases of C-14 from a nominal
1250 MWe reactor at 80% capacity. Actual data for the concentration of
C-14 in laundry waste at Oyster Creek (0.150 pCi/ml) (22) and a flow rate
of 450 gallons per day (23) was used to obtain the detergent waste
estimate. Table 2 illustrates the magnitude of each of these release
pathways. The total liquid C-14 source term, 0.044 Ci/yr, is <1% of the
gaseous source term at BWR's.
3.3 Gaseous Source Terms for PWR's
A nominal 1250 MWe PWR of Westinghouse design with a 80% capacity
factor is considered. Gaseous discharge pathways may be broken down
as follows:
1. Gaseous Waste Disposal System
2. Condenser Air Ejector Off-Gas
3. Turbine Gland Seal Exhaust
4. Fuel Handling Building Ventilation
5. Containment Purge
6. Auxiliary Building
7. Turbine Building
Gaseous waste disposal system gases evolve chiefly from the gas stripper-
evaporator package in the boron recycle system. Measurements of C-14
in the gas decay tanks at Haddam Neck (Connecticut Yankee), Yankee
Rowe, and Ginna (2,25,26) have shown an average concentration of about
5E-4 yCi/cc. Estimates of the flow of these gases have ranged from
0.1 to 1.0 scfm (23,27). Operating data at San Onofre 1, a 430 MWe
PWR, showed about 30,000 ft3 treated in a three month period (October 11,
8
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TABLE 2
BOILING WATER REACTOR CARBON-14 SOURCE TERMS
(Nominal 1250 MWe at 80% Capacity Factor)
GASEOUS SOURCE TERMS
Main Condenser Air Ejector Off-gas
Turbine Gland Seal
Containment Purge
Turbine Building Ventilation
Radwaste Facility Ventilation
LIQUID SOURCE TERMS
Clean Wastes
Dirty (Low Purity) Wastes
Chemical Wastes
Detergent Wastes
Annual C-14 Discharge Rate
(Ci/yr) or (Ci/GWe-yr)
9.0
< .015
0.0088
0.030
0.000044
9.0
0.029
0.013
0.0023
0.000075
0.044
Grand Total: 9
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1972 to January 109 1973), which would correspond to about 350,000
ft3/yr (0,66 scfm) for a 1250 We plant. A flow of 0.66 scfm along
with the measured concentration of 5E-4 yCi/cc is used to calculate a
release rate of 3.8 Ci/yr from the gaseous waste disposal system for
1250 We PWR with an 80% capacity factor. Measurements at Haddam
Neck revealed that virtually all of the C-14 was in a non-C02 form (26).
At Ginnas almost 90% was in the CH4 or C2Hg form and only about 5% in
the C02 form (2).
Condenser air ejector effluent was measured for C-14 content at
Haddam Neck and Yankee Rowe and found to contain an average of 3.6E-7
yCi/cc. Over 85% of the C-14 was in a species other than the C02
form (26). Assuming an air ejector flow of 25 scfm for a 1250 MWe PWR at
3.6E-7 yCi/cc and an 80% capacity factors a source term of 0.11 Ci/yr
is estimated.
To calculate the release from the steam generator blowdown vents the
measured C-14 concentration in steam generator water at Haddam Neck
(1.6E-7 yCi/ml) was used along with the other conditions associated
with this PWR: 5 gpm total blowdown flow rate with 35% flashing to
steam (23,26). Also, 35% of the C-14 in the blowdown was assumed to
exit via the blowdown tank vent. A release of 4.5E-4 Ci/yr of C-14 is
estimated for a 1250 MWe PWR with an 80% capacity factor.
No measurement of the turbine gland seal was available. Howevers
by assuming that all of the C-14 in the 50 gpd primary to secondary
leakage was transferred to the steam phase and that 0.1% of the main
steam flow was routed to the turbine gland seal, a conservative C-14
annual release claculation can be made. The average of the primary
coolant C-14 concentrations observed at Haddam Neck and Yankee Rowe,
1.67xlO~5 yCi/mls, was used (25,26) in this calculation to arrive at the
estimate of 9.2E-7 Ci/yr of C-14 via the turbine gland seal.
Using the measured C-14 concentration of 9E-9 uCi/cc in the Haddam
Neck fuel handling building along with its ventilation rate of 70 nr/min
all year (26), a release of 0.69 Ci/yr is estimated via this pathway
for a nominal 1250 MWe PWR.
Two approaches were used to obtain estimates for the annual discharge
of C-14 from the containment. Using the average measured concentration
(during operation) of 1.5E-6 yCi/cc for C-14 in containment air at Ginna,
Haddam Neck and Yankee Rowe (2,25,26) and assuming a containment volume
of one million cubic feet with four purges annually, a discharge of
0.52 Ci/yr of C-14 is calculated for a 1250 MWe PWR. Alternatively, using
the "standard" leak rate of 40 gpd (23) of primary coolant into the
containment and the average primary coolant C-14 concentration observed
at Haddam Neck and Yankee Rowe (1.67E-15 yd/ml) (25,26) an annual C-14
10
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release of 7.4E-4 Ci/yr may be calculated. The former value of
0.52 Ci/yr will be used, however, as it is based on a direct
measurement of the containment air. Over 90% of the containment
C-14 at Ginna was in the C and 0 forms.
By assuming the "standard" leak rate of primary coolant to
the auxiliary building, 20 gpd cold and 1 gpd hot (23), and a
primary coolant C-14 concentration of 1.67E-5 uCi/ml (25,26), an
annual auxiliary building C-14 discharge of 8.0E-4 Ci/yr of C-14
is calculated for a nominal 1250 MWe PWR at 80% capacity. At
Haddam Neck, a concentration of <6.0E-9 yCi/cc was measured for the
auxiliary building (26). This direct measurement is not sensitive
enough to serve as a base for a second calculation of the auxiliary
building discharge rate, so the value estimated using leak rate
assumptions is employed in this report.
Using the standard assumption of 1700 Ib/hr leakage into the
turbine building (23) in conjunction with the estimated secondary
coolant concentration of ^1.6E-7 pCi/ml at Haddam Neck with 50 gpd
primary to secondary leakage (26) and a 80% capacity factor, this
second method yields an annual C-14 discharge estimate of 8.7E-6
Ci/yr for a 1250 MWe PWR. Another method for estimating the turbine
building C-14 discharge is to assume that of the total C-14 entering
the secondary system, only a fraction is escaping via turbine building
ventilation exhaust. This fraction is the ratio of the standard leak
rate of secondary coolant to the turbine building, 1700 Ib/hr (23),
to the total steam flow rate, 1.4E+7 Ib/hr. Using a 50 gpd primary
to secondary leak rate at a primary coolant concentration of 1.67E-5
uCi/ml (25,26), an annual C-14 discharge of 1.1E-7 Ci/yr is calculated
for the turbine building.
A third method of calculation is to use a measured concentration
and a ventilation rate to estimate the turbine building discharge rate.
At Haddam Neck, a concentration of <8E-9 yCi/cc was measured for the
turbine building (26). This direct measurement is not sensitive
enough to serve as a base for a comparison calculation of the turbine
building discharge rate, so the value estimated using leak rate
assumption is employed in this report.
As in the case with BWRs, C-14 may appear associated with
different chemical species. C-14 found in the gas decay tanks at
Ginna was in the CH^ and C2Hs forms (2). At Haddam Neck, virtually
all of the decay tank gas was in the non-C02 form, whereas 80% of the contain-
ment C-14 and over 85% of the air ejector C-14 at Haddam Neck was in the
11
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non-COo form (26). Over 90% of the containment C-14 at Ginna was
associated with Cfy and C2H6 (2). Table 3 illustrates the PWR
gaseous C-14 release pathways and the estimated magnitude of each.
3.4 Liquid Source Terms for PWR's
Four principal liquid waste streams may be identified at a
Westinghouse PWR:
1. Boron Recycle System
2. Liquid Waste Disposal System
3. Steam Generator Slowdown
4. Turbine Drains
Using a flow rate of 1 gpm (23) through the boron recycle system,
assumed to be at a primary coolant C-14 concentration of 1.67E-5
yCi/ml (25,26), and assuming that only 10% of the boron recycle liquids
are discharged, a release of 2.7E-3 Ci/yr of C-14 may be calculated
(at 80% capacity factor).
The release of C-14 from the liquid waste disposal system may be
estimated using the "standard" assumptions for liquid waste stream
flow rates and fractions of primary coolant activity (23), and the
measured average primary coolant C-14 concentration of 1.67E-5 yCi/ml
(25,26). A release of 1.9E-3 Ci/yr of C-14 is estimated from the liquid
waste disposal system.
A steam generator blowdown average concentration of 1.6E-7 yCi/ml
and a blowdown rate of 5 gpm (total) with a 50 gpd primary to secondary
leak was reported at Haddam Neck (26). If 65% of the blowdown liquid
remains as a liquid waste after flashing (23), a release rate of
8.3E-4 Ci/yr of C-14 is calculated for the steam generator blowdown
discharge pathway.
Data for the Haddam Neck plant showed a turbine drain (secondary
system leakage) flow of 7570 gpd at a C-14 concentration of about
1.6E-7 yCi/ml, resulting in an annual C-14 discharge estimate of about
1.3E-5 Ci/yr (26).
Table 3 illustrates each of these liquid discharge pathways and
the estimated C-14 source term for each. As was the case for BWRs,
virtually all of the C-14 is discharged by gaseous pathways.
12
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TABLE 3
PRESSURIZED WATER REACTOR CARBON-14 SOURCE TERMS
(Westlnghouse Design, Nominal 1250 MWe at 80% Capacity Factor)
Annual C-14 Discharge Rate
GASEOUS SOURCE TERMS (C1/yr) or (Ci/GWe-yr)
Gaseous Waste Disposal System 3.8
Condenser Air Ejector Off-gas 0.11
Steam Generator Slowdown Tank Vent 4.5E-4
Turbine Gland Seal 9.2E-7
Fuel Handling Building Ventilation 0.69
Containment Purge 0.52
Auxiliary Building Ventilation 8.0E-4
Turbine Building Ventilation 8.7E-6
5.1
LIQUID SOURCE TERMS
CVCS (Boron Recycle System) .0027
Liquid Waste Disposal System .0019
Steam Generator Slowdown 8.3E-4
Turbine Drains 1.3E-5
5.4E-3
Grand Total: 5.1
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3.5 Source Term Summary
It is evident that good direct measurements of C-14 in many of
the discharge pathways are lacking. What measurements exist were
obtained at light water reactors of early design. Therefore, great
reliance has been placed on "standard" source term assumptions (23)
as an aid in calculating C-14 source terms for reactors of the 1250
MWe power level. Furthermore, there is uncertainty as to the
chemical species in which C-14 may occur, which has tremendous
Implications relative to any proposed treatment technologies.
C-14 production in coolant in light water reactors has been
reported to be in the range of 9 to 16 Ci/GWe-yr for BWR's and
3 to 11 C1/GWe-yr for PWR's as previously shown in Table 1. Estimates
of C-14 in gaseous effluents have ranged from 6-11 Ci/GWe for PWRs and up
to 8 Ci/yr for a 600 MWe BWR, most of which is produced by the reaction
of neutrons with oxygen-17 in the coolant (1, 2, 21). These estimates
are in reasonable agreement with the gaseous source terms derived in
this report based on measurements: 9.0 Ci/GWe-yr for BWR's and 5.1
Ci/GWe-yr for PWR's. Also, the liquid C-14 source term is much
smaller (< 1%) than the gaseous source term for each reactor type,
based on the calculated source terms in this report.
3.6 Carbon-14 Control for BWR's and PWR's
At boiling water reactors, the condenser air ejector contributes
about 98% of the total BWR C-14 source term (Table 2). The great
majority of BWRs are proposing the use of recombiners and charcoal
(at various temperatures) to control the release of noble gases from
the air ejector. Under the operating conditions required to recombine
elemental hydrogen and oxygen in the off-gas stream, hydrocarbons will
be converted to carbon dioxide and water. Therefore, it is expected
that C-14 will be primarily in the form of carbon dioxide at BWRs.
Those BWRs that are not employing the recombiner-charcoal combination
have typically proposed cryogenic distillation, which has C02 removal
equipment incorporated as normal design practice. Potential processes
for removal of CO? from the recombiner effluent (total volume flow:
<30 scfm per 1,000 MWe) include caustic scrubbing, soda lime absorption,
molecular sieves, and low temperature adsorption on silica gel or carbon.
Considering only caustic scrubbing, with a nominal 90% C02 removal
efficiency, total BWR releases of C-14 would be reduced by almost a
factor of 10. BWR cryogenic distillation systems employ refrigerated
carbon beds and liquid nitrogen-cooled "freezeout coils" to remove C02.
14
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Approximately 75% of the C-14 from pressurized water reactor
results from the gaseous waste disposal system. Many PWRs of
Westinghouse design are planning to use the "cover gas recycle
system," which results in no release (except for leakage) of radio-
active waste system gases over the life of the plant. A few PWRs
have chosen cryogenic charcoal adsorption, in which C-14 in the
form of hydrocarbons will be converted to the CO? form. Again,
caustic scrubbing could be introduced to remove C-14 as C02 with a
nominal efficiency of 90%. Thus, PWR C-14 releases could be reduced
from 5.1 Ci/yr to about 1.6 Ci/yr, a reduction of almost 70% in total
C-14 release from a 1250 MWe PWR.
Cost estimates for C0£ scrubbers may vary because of materials of
construction and complexity of design and operation. Furthermore, the
size of scrubbers required for PWRs is much smaller than employed by
many non-nuclear industries. Indications are that a 100 cfm caustic
scrubber (for BWR condenser air ejector off -gas after recombiner
treatment) would result in an equipment cost of only a few thousand
dollars, approximately $4,000, in 1970 dollars (28). Capital cost
would therefore be in the $7,000-$8,000 range. Total annual costs
(capitalization plus operating and maintenance) are estimated at
about $4,000. Upgrading these estimates by the Marshall and Swift
Cost Index to, September 1974 (for chemical industries), the estimated
capital cost of a caustic scrubber would be about $11,000 (29). Total
annual costs in September 1974 dollars are estimated at about $6,000.
Scrubbers for use in a PWR off-gas stream would be even less expensive
as flow capacity would have to be only 10 scfm or less. However, costs
for a PWR C02 caustic scrubber are taken as half those for a BWR, i.e.,
capital cost as $5,500, and total annual operating cost as $3,000.
It is possible that a solid adsorber, such as charcoal, or a solid
absorber, such as an alkali metal alumino-silicate molecular sieve,
would be even less expensive and perhaps more desirable in terms of
handling and ultimate waste disposal. However, specific designs and
cost information were not readily available.
On February 5, 1976, the U.S. Environmental Protection Agency
awarded a contract to Science Applications, Inc. to assess carbon-14
control technology for LWR's. The contract which is expected to be
completed within eight months after awarding should provide needed
specific design and cost information, The contract report will address:
(1) the capabilities of current LWR off -gas systems for control of
C-14, (2) the cost of modifying current LWR off -gas cleanup systems,
if possible, to control C-14, (3) the availability and cost of
15
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specialized carbon-14 control systems for use at both LWR's and
LWR fuel reprocessing plants, and (4) the potential capability
for C-14 control and costs of off-gas treatment systems which
have been proposed for use at LWR fuel reprocessing plants for
control of other contaminants, such as krypton-85 and radioiodine.
The Information to be developed in these studies may point out
certain dual-control capabilities for some off-gas treatment
systems (I.e., such as control of both krypton-85 and carbon-14
by one system in a reprocessing plant) and thus alter other cost-
effectiveness analyses.
16
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4. CARBON-14 AT LWR FUEL REPROCESSING PLANTS
Spent fuel from LWR's can be reprocessed to recover valuable
uranium and plutonium and to process the radioactive waste Into
forms more suitable for disposal than the spent fuel form. Current
plans for reprocessing spent fuel Include a cooling period of about
150 days to permit decay of the short-lived radlonuclldes, especially
1-131. The control of radioactive iodine has proven to be most
difficult but must be accomplished due to the extremely long half-
life of 1-129. Because of its volatility most of the Iodine is
released into the process off-gas systems at reprocessing plants
where It constitutes one of the major contaminants, along with
partlculates, tritium, krypton-85 and NOx. Recently, Magno et^al. (1)
pointed out that there may be significant quantities of carbon-TT
in the spent fuel and assumed that all of the carbon-14 would be
discharged to the atmosphere. Thus, it appears that carbon-14
should be included as another major constituent, in terms of world-
wide environmental and public health Impact, of reprocessing plant
off-gas releases.
Chapter two of this report presents a C-14 fuel production rate of
22 Ci in 33.5 MTHM or 0.66 Ci/MTHM. This production rate is comparable
to the ORNL estimate of 0.464 Ci/MTHM as presented in reference (30)
and the ERDA estimate of 0.4 Ci/MTHM (31). Using the production rate
of 0.66 Ci/MTHM developed in this report, there would be 990 curies
per year available for release at a typical LWR fuel reprocessing
plant which has a throughput capacity of 1500 MTHM per year.
4.1 Behavior of Carbon in the Reprocessing Plant
The systems described here are those presented in the Barnwell
Nuclear Fuel Plant separations facility final safety analysis report (32).
The first process which would allow C-14 to escape is shearing. Here
the fuel elements are cut into two- to five-inch segments. The
segments fall by gravity into a dissolving basket and an 8 molar nitric
add dissolving solution. There 1s a slight air flow (250 scfm) from
the shear to the dissolving solution to direct gases and partlculates
to the dissolver. In the dlssolver the pieces are exposed to 90°C,
8 molar nitric acid (HNOj). In this environment it is currently
thought that 95-99% of the carbon present will escape to the off-gas
system as CO or C02« The formation of monoxide or dioxide is expected
because of the excess oxygen in solution from the U02 and HN03.
17
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The off-gas process system at Barnwell, as described, is designed
for the removal of participates, radioiodine, and NOx only. The
Initial treatment of the dissolver off-gases is in the No. 1
iodine scrubber where the gases are scrubbed with a 0.4 molar
solution of HgCNOote in 6=8 molar HN03 at 105°F. The gases then
pass through the NOx absorber where they are scrubbed with water.
The dissolver off-gases join the vessel off-gases and are scrubbed
in the No. 2 iodine scrubber with 0.01 molar Hg(NO 3)2 in 0.5 molar
HNOq at 100°F. Final iodine adsorption is done using several silver
zeolite beds and HEPA filters just prior to the gaseous stream being
discharged to the stack. It appears that the described waste treat-
ment system will have little effect on C-14 as C02 so a carbon-14
decontamination factor of 1 is assigned for a current LWR fuel
reprocessing plant.
Another parameter which can be important in the air cleaning
efficiency of various systems is the total quantity of contaminant
present in the off-gas stream. Trace quantities of contaminants
often prove difficult to collect or control. The quantity of carbon
in the off-gas system of a reprocessing plant of the Barnwell design
is developed as follows.
Assuming there are 990 Ci/yr released to the off-gas system,
we find the C-14 flow rate is 0.138 Ci/hr, or about 0.031 gm/hr;
assuming 7,200 operating hours per year. This rate must be compared
to the natural abundance of C02 in the air. Since the standard
atmosphere is 0.033% by volume carbon dioxide (33), 0.033% by volume
of the air flowing in the dissolver off-gas (DOG) system Is stable
carbon dioxide. For comparison, these flow rates are presented in
Table 4. Based on this estimate, it appears that sufficient carbon
dioxide is present in the off-gas stream to permit reasonable
assurance that it can be controlled. However, this factor should be
recognized in the design of systems for the collection of carbon dioxide,
Because of the high molarity of the dissolving solutions, the 1-5%
of the C-14 remaining in the dissolver solution is likely to be
incorporated into carbonic acid. From the dissolver it would proceed
through the dissolver exchanger and would eventually go to the feed
surge tank. From here it would pass through feed adjustment tanks,
the centrifuge, the high activity feed tank, and eventually to high-
level waste disposal. Since the behavior in the high activity process
stream is difficult to predict, the above-mentioned path is considered
the most likely but is certainly not the only potential path. However,
there appears to be no set of conditions in which the C-14 would be
released to the atmosphere following formation of carbonic acid.
18
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In summary, it is estimated that at least 95 to 99% of the
C-14 contained in the fuel will be released to the off-gas system
and subsequently to the atmosphere since currently employed off-gas
treatment systems will probably not remove C02 to any extent; while
1 to 5%, most likely closer to 1% than 5%, remaining in solution
should, remain in the high-level wastes. Therefore, a gaseous C-14
source term of nearly 990 Ci per year is estimated for a 1500 MT/yr
plant using the Barnwell off-gas system design.
4.2 Control Systems at LWR Fuel Reprocessing Plants
The off-gas treatment system at Barnwell (34) is expected to
remove essentially no C-14. In light of the Magno et al_. findings (1),
it would appear prudent to investigate the costs ancTremoval efficiencies
of carbon removal systems which could be installed at reprocessing plants.
Of particular interest here would be a system in which other contam-
inants, such as tritium and krypton, would also be collected. Two
widely used methods of carbon dioxide removal involve passing of the
gas through either a lime bed or a caustic scrubber. These methods
are known to be effective but produce large quantities of solid waste
compared to the amount of C-14 removed. Other methods of C0£ removal
which are used on a commercial scale include ethanolamine scrubbing,
hot and cold alkali carbonate scrubbing, water scrubbing, and molecular
sieve adsorption. Depending on the amount of CO evolved during
dissolution, catalytic conversion to C02 or separate systems for CO
removal may be necessary. The removal efficiencies of all gas treatment
systems are highly dependent on temperature, pressure, humidity, flow
rate, and the fraction of the gas stream which is to be treated.
Further study is necessary as to the system most applicable for utiliza-
tion at a reprocessing plant.
The cryogenic process,which takes advantage of the widely differing
boiling point of krypton (Kr), xenon (Xe), and C02 (actually the
"boiling" point for C02 is a triple point) at atmospheric pressure,
is a possibility for removing C02 from the gaseous effluent stream.
The carbon dioxide could be frozen out prior to the Kr-Xe removal
since its triple point is some 30°C higher than either the Xe or Kr
boiling points. Solid C02 could be removed, sublimed and bottled for
storage. This process has been proposed for collection of krypton in
the off-gas stream. To avoid explosive concentrations of oxygen in the
cryogenic systems, the proposals included a sophisticated pretreatment
of the off-gas stream in which all oxygen would be removed. The carbon
in this system would be converted entirely to C02 and could be removed
as discussed above.
19
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A second process, selective absorption, is under development
for control of krypton at reprocessing plants. In this process,
the off-gas is passed through a solvent (fluorocarbon solvents have
received the most attention for noble gas collection) where certain
gases are absorbed. In further steps, the dissolved gases are then
selectively stripped out of the solvent. This process should be
analyzed for the collection of C02-
In summary, the need for research on C-14 in reprocessing
facilities exists in the following areas: amounts of C-14 produced
in the fuel, chemical forms of the C-14 as it is evolved from the
dissolver, unexpected chemical behavior elsewhere in any system,
partitioning between the off-gas and liquid process systems,
possible process pathways and reactions in those systems, probable
decontamination factors for various systems, and costs of collection
systems. Carbon-14 control technology and costs for LWR fuel
reprocessing facilities is currently being evaluated by Science
Applications, Inc. under a contract awarded by the U.S. Environmental
Protection Agency. This contract is briefly discussed in section 3.6
of this report.
20
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TABLE 4
AIR AND CARBON DIOXIDE FLOW RATES IN
THE OFF-GAS SYSTEM AT BARNWELL (34)
Design Flow C02 Flow % of C02 Flow Rate
Scrubber Rate (gm/hr) Rate (gm/hr) which is 14COg*
No. 1 Iodine 1.18E+6 592 1.72E-2
NOx 1.22E+6 615 1.66E-2
No. 2 Iodine 8.62E+6 4330 2.35E-3
* On a mass basis where the 'C02 flow rate is 0.1 gm/hr.
21
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5. ENVIRONMENTAL TRANSPORT OF CARBON-14
5.1 Local Transport
Carbon-14 is injected into the troposphere from LWR fuel cycle
facilities and resulting local air concentrations around the points
of release can be estimated using a diffusion model which estimates
downwind concentrations for given site meteorological conditions.
The EPA AIREM computer code (35) can be used to estimate local air
concentrations based on estimated source terms and measured
meteorological conditions at sites of interest. Local transport
and resulting carbon-14 concentrations in local media other than
atr have not as yet been examined in detail in the literature for
LWR carbon-14 discharges. Local media such as food should be invest-
igated to assess whether potential concentrations of C-14 provide
significant pathways. The concentration of carbon-14 in vegetation
can be obtained by using the U.S. Nuclear Regulatory Commission
model (42) which assumes that the ratio of carbon-14 to the natural
carbon In the vegetation is the same as the ratio of carbon-14 to
natural carbon in the atmosphere surrounding the vegetation. The
concentration of natural carbon in the atmosphere is taken to be
0.16 gm/m^ and the fraction of the total plant mass that is natural
carbon is assumed to be 0.11.
5.2 World-Wide Transport
Carbon-14 injected in the troposphere becomes part of the carbon
cycle and is constantly moving from inorganic reservoirs (CO? in the
atmosphere and dissolved in water) to living systems and back again.
Man is also affecting the carbon cycle by increasing the concentration
of carbon-12 in the active carbon cycle by burning fossil fuels. The
effect of these injections can only be estimated since specific
carbon-14 concentrations and C02 concentrations are not known to a
high degree of precision and carbon undergoes environmental trans-
port processes which are not yet quantitatively defined. Predictions
of world-wide future and past carbon dioxide concentrations have been
derived from many different box models. The following quote from
Minze Stuiver (36) gives insight into the validity of these models.
"Box models that describe reservoir properties are used to assess the
transfer of radiocarbon between the various reservoirs. Various
simplifying assumptions have to be made for a rigorous mathematical
treatment of the model. Such studies occasionally give the impression
that a precise calculation provides a screen for an imprecise assumption,
and the models should be considered a crude approximation only of the
gross features of carbon transfer in nature." Livingstone (37) elaborates
22
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on the current state of knowledge about the carbon cycle by stating
that the science of the biosphere is still primitive, despite its
importance. No pools in the carbon cycle seem to be known with
satisfactory accuracy and it would be highly desirable to have a much
wider net of stations measuring the atmospheric carbon dioxide and
many more data for the equilibrium carbon dioxide of surface ocean
water. (37)
The world transport model for carbon-14 that is currently used
by the U.S. Environmental Protection Agency is that developed by
Machta (38,39). This model is a relatively simple multireservoir
exchange model consisting of seven compartments: stratosphere,
troposphere, mixed layer of the ocean, deep ocean, short-term land
biosphere, long-term land biosphere, and marine biosphere. The
exchange rates between and within reservoirs are assigned by Machta
except for the troposphere-mixed ocean layer rates which are obtained
from a trial-and-error least squares fit procedure using atomic bomb
produced '^CO? as a tracer. The model also takes into consideration
the increase in the levels of tropospheric carbon dioxide due to the
combustion of fossil fuel containing no carbon-14 which reduces the
specific activity of C-14 in the carbon cycle (the "Suess Effect")
and thereby reduces the long-term environmental dose commitment from
carbon-14. Machta assumes that the characteristics of neither the
oceans nor the biosphere vary with time. Carbon-14 inputs to the
troposphere in the Machta model were due to nuclear weapon testing and
cosmic rays. Magno et al. (1) modified the Machta model to allow
Injections of carbon^T4~Tnto the troposphere from the nuclear power
industry. The modified Machta model in the form of a computer code
is listed and discussed in detail in Appendix 1.
Given injections of fossil fuel 12C02 since the beginning of the
industrial era (I860) and inputs of nuclear fuel cycle T4C02 to the
troposphere, the modified Machta model can be used to estimate the
C-12 content and the C-14 content (cosmic C-14 and nuclear fuel cycle
C-14) tn the stratosphere, troposphere, mixed layer of the ocean, deep
ocean, short-term land biosphere, long-term land biosphere, and the
marine biosphere. The Machta model basically computes net changes
of C-12 and C-14 concentrations in various reservoirs since 1860 and
the estimated reservoir concentration is computed by adding initial
reservoir concentrations to the net changes in the concentration due
to man-made injections of C-12 and C-14 and reservoir exchange rates
over time. This basic model is rather simple and consideration is
being given to investigating other world transport models for carbon-14
utilizing the work of Keeling et^ al_. (40,41) and others.
23
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6. DOSIMETRY FOR CARBON-14 DIOXIDE
6.1 Critical Organ Method to Estimate Local Short-Term Dose
Equivalent Rates
To estimate the potential short-term dose equivalent rate, local
intakes of carbon-14 from dosimetrically significant pathways must
be calculated and then multiplied by the appropriate dose equivalent
conversion factor. Dose equivalent conversion factors per picocurie
intake for the Inhalation and ingestion pathways were computed using
the equation:
DECFa(or w) I>rem/Pci 1nnaled (°r ingested)] = 7.38E-2-E/M • fa(or w) Tfiff
where, Teff = effective half -life in days
fa = fraction of the inhaled activity which deposits in the
critical organ
f s fraction of the ingested activity which deposits in the
critical organ
M = mass of the critical organ in grams
E * effective energy absorbed in the critical organ per
disintegration in MeV/dis
DECF = dose equivalent conversion factor for the inhalation
pathway
DECFW = dose equivalent conversion factor for the ingestion
pathway
The biological parameter data utilized in the computation as well as
the computed DECF's are presented in Table 5. The biological parameter
data was taken from ICRP Publication 2 (43) except for the value of E
(MeV/dis) which was taken from MIRD Supplement Number 5/Pamphlet No. 7
(44). The ICRP has updated values for organ mass in ICRP Publication
23 (45), but the values for the other biological parameters needed to
calculate the dose equivalent conversion factors have not been updated.
It ts additionally noted that these DECF's developed from existing
ICRP recommendations may be conservative based on more recent dose
models as discussed by Rohwer et^ al_. (46).
The dose equivalent rate per unit air concentration for the in-
halation pathway, DECFa, was computed using an adult breathing rate
of 8000 nr/yr and the previously computed dose equivalent conversion
factors per picocurie intake. The adult breathing rate was obtained by
averaging the adult man and adult woman breathing rates as presented
in ICRP Publication 23 (45). The resulting DECFa values are shown in
Table 6.
24
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The dose equivalent rate per unit air concentration for the
submersion pathway DtCFs was computed using the equation
DECFC (mrem/yr) = 7.2 x 109 x E (MeV
TV
s '""Ci'/cc) (dT?l
Using a value of 0.0493 MeV/dis for E, the resulting DECFS is shown
in Table 6. Because C-14 decays by beta emission, the estimated
annual dose equivalent rate from submersion will be the1 dose
equivalent rate at the clothing or outer skin surface of the body.
Thts dose equivalent rate will decrease with tissue depth and the
radiosensitive tissues underneath the normal inert layer of skin will
receive only a fraction of the skin surface dose equivalent.
Given an air concentration, the local dose equivalent rate via
inhalation and submersion from discharges of C-14 can be obtained
by simple multiplication with the conversion factors in Table 6. The
air concentration as a function of downwind distance from the podnt
of C-14 discharge is calculated by multiplying the C-14 discharge
rate "Q" in curies/second times the meteorological dilution factor
"x/QM in sec/m3 at the downwind distance where the dose equivalent
rate is computed. The annual average dilution factor for an elevated
release fs found by assuming a sector-averaged concentration in each
sector wfth the plume following a Gaussian distribution in the vertical
direction.
The local dose equivalent rate via ingestion can be calculated if
the C-14 activity in the vegetation is known. The yearly pCi intake
is calculated by multiplying the vegetation activity in pCi/gm by the
human vegetation intake rate in gm/yr. The ingestion dose equivalent
rate is then calculated by multiplying the C-14 activity intake rate
in pCi/yr by the DECFW factor in Table 5. If the C-14 activity in
vegetation is not known, then the activity can be estimated by
making the simplifying assumption that the C-14 specific activity in
local vegetation is equal to local atmospheric specific activity. The
local atmospheric C-14 specific activity is obtained by multiplying
tKe source tenm "Q" in pCi/sec by the meteorological dilution factor
"x/Q" in sec/m3 (at the distance where the specific activity is to be
calculated] and dividing by the concentration of carbon-12 in gm/m^.
The vegetation activity is then estimated by multiplying the vegetation
specific activity in pCi C-14/gm C-12 by the fraction of the plant mass
that is C-12. A fraction of O.ll C-12 in plant mass is employed by the
U.S. Nuclear Regulatory Commission (42).
25
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TABLE 5
CARBON-14 ADULT DOSE EQUIVALENT CONVERSION
FACTORS PER UNIT INTAKE
Critical Organ
Total Body
Fat
Bone
'eff
(days)
10
12
'40
fa
0.75
0.38
0.02
'w
1.0
0.5
0.025
m( grams)
7E + 4*
IE + 4
7E + 3
E(MeV/dis)
0.0493
0.0493
0.0493
DECFa
(mrem/pCi inhaled)
3.9E - 7
1.6E
4.2E
- 6
- 7
DECFW
(mrem/pCi i ngested )
5.2E - 7
2.2E
5.2E
- 6
- 7
t\J
* 7E + 4 equals 7 x
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TABLE 6
CARBON-14 ADULT DOSE EQUIVALENT RATE CONVERSION
FACTORS PER UNIT AIR CONCENTRATION
mrem/yr
Critical Organ Pathway DECF ( yCi/cc)
Total Body Inhalation 3.IE + 9
Fat Inhalation 1.4E + 10
Bone Inhalation 3.3E + 9
Total Body Submersion 3.6E + 8
27
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6.2 Specific Activity Method to Estimate World-Wide Long-Term
Dose Equivalent Rates'
An Intermediate result of the Machta model computation which
was previously described is the specific activity of C-14 (pCi C-14/gm
C-12) in the troposphere. Specific activities of C-14 are presented
separately for nuclear fuel cycle injections of C-14 and for cosmic
C-14. Therefore, the C-14 dose equivalent rates from the nuclear
fuel cycle can be compared with background dose equivalent rates from
cosmic C-14. In order to convert this specific activity to a dose
equivalent rate in man, the conservative assumption is made that the
specific activity of C-14 in the troposphere and in man are the same.
The specific activity method assumes instantaneous equilibrium which
is a conservative assumption thereby providing an upper limit to the
estimated dose equivalent rate. Specific activity dose equivalent
rate conversion factors were derived asing the following equation:
*
DECF (mrem/yr per pCi C-14/gm C-12) = 3.7E+10 dis/sec-Ci x
1 C1/1E+12 pCi x 0.0493 MeV/dis x 1.6E-6 ergs/MeV x
1 gm (tissue} rad/100 ergs x Mc gm C-12/MT gm tissue x
3.15E+7 sec/yr x 1 rem/rad x 103 mrem/rem
= 0.919 MC/MT
where MC and My is the mass of carbon and mass of tissue respectively
for the organ or tissue that the DECF is being calculated. Values
for M and Mj were obtained from ICRP Publication 23 (45) and
calculated carbon-14 specific activity dose equivalent rate conversion
factors for selected organs are presented in Table 7.
Carbon-14 specific activity dose equivalent rate conversion
factors for body organs can also be calculated using "5" factors
(average dose equivalent per unit accumulated activity) presented by
Snyder e£a1_. (47). The "S" factor is the dose equivalent to a target
organ per unit integrated activity in the source organ which can be
equated to the dose equivalent rate per equilibrium organ activity
burden for steady state conditions. The specific activity dose
equivalent rate conversion factors can be calculated using the
equation:
DECF (mrem/yr per pCi C-14/gm C-12) = S (rem/pd-day)x
Mc (gm C-12) x 1E-6 yCi/pCi x 365 day/yr x 103 mrem/rem
= 0.365 SMC
28
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Carbon-14 "S" factors for 22 source organs and 24 target organs
are presented in reference (47). When Mc values are obtained from
ICRP Publication 23 (45), calculated DECF values are similar to
those calculated using the previously described technique. The
dose equivalent rate to the totalendosteal cells per unit C-14
specific activity in cancellous bone, cortical bone, red marrow
and yellow was calculated using the "S" factor technique and the
DECF value is presented in Table 7. ICRP Publication 11 (48)
discusses the importance of the dose equivalent rate to endosteal
cells from low-energy beta-emitters such as C-14. The "S" factor
method was utilized by ERDA (20) and values were calculated similar
to those presented in Table 7 except for segments of the GI tract.
The 61 tract model in reference (20) includes the dose equivalent
rate by the migrating contents in the segments of the GI tract
whereas the factors in Table 7 do not include this contribution
to the dose equivalent rate. Considering ^C in tissue and in the
migrating contents, DECF values of 0.14 and 0.16 mrem/yr per pCi
C-14/gm C-12 for the stomach and lower large intestine respectively
can be inferred from reference (20). Reference (20) should be
reviewed for a discussion of the model employed to obtain the dose
equivalent rate contribution from the migrating contents in the
stomach and intestine of the GI tract.
The relative contributions of the ingestion and inhalation
pathways to specific activity dose equivalent rate can be determined
if the specific activity in the air and in the diet (food and water)
are assumed equal. Assuming air is 0.033% C02, an adult breathing
rate of 2.2 x 107 cc and that 75% of inhaled air is retained in the
total body (fa = .75), 2.92 gm/day of carbon is inhaled per day by
standard man. Standard man intakes 300 gm/day of carbon from food
and fluids (45). The relative contribution of the inhalation and
ingestion pathways to the total C-14 dose equivalent rate for
equilibrium conditions is assumed to be proportional to the intake
of carbon for each pathway. Therefore, the ingestion pathway
contributes 99% (300/302.9 x 100%) of the carbon-14 specific activity
dose equivalent rate.
By assuming that the C-14 specific activity in air is the same
in tissues of man, the dose equivalent rate to critical organs can be
obtained by multiplying the C-14 tropospheric specific activity by
the specific activity dose equivalent rate conversion factors presented
in Table 7. The computed dose equivalent rate represents a measure of
the annual potential impact of C-14 discharges on the average worldwide
individual. Since carbon-14 is long-lived (half-life of 5,730 years)
and therefore, represents a long-term potential source of exposure to
a large number of people, the long-term impact on the population at
large and on the individual must be assessed in addition to the annual
29
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impact. The potential environmental impact in subsequent years is
estimated by calculating the "environmental dose commitment" (49)
which is the sum of all doses to individuals over the entire time
period that the carbon-14 persists in the environment in a state
available for interaction with humans. The population dose commit-
ment in person-rems is usually expressed for a period of 100 years
since it is difficult to predict the world population growth much
beyond this time period. The total body individual and population
dose commitment can be computed by using the specific activity
method with the modified Machta Code as described in Appendix 1.
30
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TABLE 7
CARBON-14 SPECIFIC ACTIVITY DOSE EQUIVALENT
RATE CONVERSION FACTORS
Critical Organ
Body fat
Kidneys (2)
Liver
Lung? (2)
Cortical Bone
Trabecular Bone
Red Marrow
Yellow Marrow
Total Endosteal Cells
Lower Large Intestine
Stomach
Skim
Testes (2)
Thyroid
Total Body
MT
(Weight of organ
in grams)
13500
310
1800
1000
4000
1000
1500
1500
160
150
2600
35
20
70000
Mc
(Carbon in organ
in grams)
10000
40
260
100
550
130
620
950
19
18
590
3.1
2.1
16000
DECF
mrem/yr
pCi C-14/gm C-12
0.68
0.12
0.13
0.09
0.13
0.12
0.38
0.58
0.33*
0.11
0.11
0.21
0.08
0.10
0.21
*This conversion factor represents contributions from C-14 in
cancellous bone, cortical bone, red marrow and yellow marrow using
reference (47).
31
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7. CARBON-14 DOSE EQUIVALENT RATES AND HEALTH IMPACT
Estimated annual carbon-14 dose equivalent rates to individuals
at the offsite location where maximum air.concentrations occur at
light-water-cooled reactors and fuel reprocessing plants are given
in Table 8. The assumptions used for the calculation of the local
dose equivalent rates are as follows:
(a) carbon-14 source terms
LWR fuel reprocessing facility - 990 Ci/yr
PWR - 5 Ci/yr
BWR - 9 Ci/yr
(b) maximum offsite atmospheric dispersion factor - "x/Q"
fuel reprocessing facility - 5.0E-8
PWR - 2.5E-6
BWR with stack - 5.0E-8
BWR without stack - 2.5E-6
(c) concentration of carbon-12 in the troposphere = 0.174 gm C-12/m
(d) specific activity dose equivalent rate conversion factors
are 0.21 and 0.08 mrem/yr per pCi C-14/gm C-12 for the total
body and gonads respectively.
A specific activity model was employed for the local maximum
individual dose equivalent rate calculation. This method assumes
that the carbon-14 specific activity in the maximum individual is
equal to carbon-14 specific activity in the air at the maximum point
of offsite concentration. This methodology estimates a conservative
upper bound to the maximum individual carbon-14 dose equivalent rate
since the carbon-14 specific activity in man's diet will not be
instantaneously equal to the specific activity in the air at the
point of maximum offsite concentration. Any food or fluids that the
maximum individual ingests that is uncontaminated or at a lower C-14
specific activity than that at the point of maximum offsite concen-
tration will result in lower C-14 dose equivalent rates than those
presented in Table 8. However, even using the conservative specific
Activity model, the local C-14 dose equivalent rates to the maximum
individual presented in Table 8 are extremely low when compared to
natural background dose equivalent rates. Using the linear, non-
threshold dose effect relationships (50), less than one health effect
due to carbon-14 exposure to the population within 50 miles of any of
these facilities is expected during its entire operating life.
32
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TABLE 8
MAXIMUM ANNUAL CARBON-14 DOSE EQUIVALENT RATES
TO INDIVIDUALS AT LWR FACILITIES IN mrem/yr
Organ
Total Body
Gonads
Fuel
Reprocessing
Facility
1.9
0.72
PWR
0.48
0.18
BUR
(with stack)
-
1.7E-2
6.6E-3
BWR
(without stack)
0.86
0.33
33
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The health effects to the world's population from the U.S.
LWR nuclear Industry due to C-14 discharges present quite a
different story. The potential committed health effects depends
on the projected growth of both the world population and the U.S.
nuclear industry. The potential health effects committed to the
world's population for one year's LWR power production can be
calculated ustng the following equation:
H(t) - i Q(t) x D^tJ/Qft) x J1
where, -
H(t) = potential committed health effects for release of
carbon-14 in calendar year t
Q(t) = annual discharge of carbon-14 in curies
D|(t)/Q(t) = committed population dose in person-rem to organ i
per curie release of carbon-14 in calendar year t
J-{ = number of health effects per man-rem to organ i
The annual discharge of carbon-14 from the LWR nuclear power industry
is equal to the LWR produced electrical power in GWe-yr times 30 Ci/GWe-yr.
The production rate of C-14 of LWR's of about 30 Ci/GWe-yr is based on
a production rate of 22 Ci/GWe-yr in the fuel and about 8 Ci/GWe-yr in
the coolant of LWR's. For a LWR produced electrical power of 1 GWe-yr,
22 curies of C-14 would be discharged at a LWR fuel reprocessing plant
and about 8 curies of C-14 would be discharged at a LWR with no control
for carbon-14. Various scenarios have been presented for the growth of
nuclear power in the U.S. For example, the Energy Research and Develop-
ment Administration (ERDA) has presented a projection of nuclear capacity
for the year 2000 as between 625,000 and 1,250,000 MWe. The Federal
Energy Administration projects a range of 600,000 to 700,000 MWe for
the nuclear energy capacity for the year 2000 (51). For the purposes of
this report, two projections (cases 1 and 2) of power growth will be
utilized to estimate a range of potential committed health effects due
to C-14 discharges from the LWR power industry. Cases 1 and 2 are the
moderate/low growth and high growth cases respectively of U.S. installed
&WR capacity as presented in the ERDA update of WASH-1139(74) (52).
Ca.se 1 projections represent a slower growth rate of electricity with
the. need for new nuclear power plants being reduced. Case 2 projections
34
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"reflects the Presidential objectives for 200 new nuclear power
plants through 1985 and a continuation of a concerted nuclear
effort in the longer-term coupled with continued high rates of
growth in electric energy" (53). The installed LWR nuclear
capacities for cases 1 and 2 for the years 1975 to 2000 are pre-
sented in Tables 12 and 13 which are worksheets showing a
calculation of the world-wide potential health effects from carbon-14
for the two projected growth rates of the U.S. light-water-cooled
nuclear power industry.
The worksheets also present the 100-year world-wide population
dose commitment per curie of C-14 discharged by calendar year.
These conversion factors were obtained by utilizing the modified
Machta world-wide carbon-14 transport computer code which is
described earlier in this report. The 1970 world population was
estimated as 3.56E+9 with an annual growth rate of 1.9 percent (49).
The conversion from population dose to potential health effects
was performed using the following carbon-14 dose-risk conversion
factors:
400 cancers(200 fatal and 200 non-fatal) per 10" person-rem
to the whole body
200 genetic effects per 10° person-rem to the gonads
As is shown in the worksheets (Tables 12 and 13), it is estimated
that between about 3900 and 5500 potential health effects will be
committed to the world's population by year 2000 from carbon-14
discharges from the U.S. LWR nuclear industry. These health effects
estimates assume that all C-14 generated in LWR power production is
discharged to the atmosphere, that the 100-year population dose
commitment adequately reflects the Impact of carbon-14 in the
atmosphere and that the linear dose-effect relationship is valid at
these low dose rates.
35
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8. SUMMARY
This review has presented C-14 source term estimates and the
state of carbon-14 control technology as it is presently known.
Production rates of C-14 in light-water reactors were estimated as
22 Ci/GWe-yr in the fuel and 9.2 and 3.3 Ci/GWe-yr respectively in
the BWR and PWR coolant. Based on limited measurements- at LWR's,
gaseous C-14 emissions of 9.0 and 5.1 Ci/GWe-yr were estimated for
the BWR and PWR. Caustic scrubbers were discussed as a potential
C-14 control system for LWR's wtth estimated C-14 discharge reductions
of almost a factor of 10 for BWR's and about three for the PWR. Based
on production rates of C-14 in the fuel of light-water reactors and
assuming that all the C-14 in the spent fuel would be discharged to
the atmosphere, a gaseous C-14 source term of about 990 Ci per year
was estimated for a 1500 MT/yr LWR fuel reprocessing plant. Carbon-
14 undergoes environmental transport processes which are not yet
quantitatively well 'defined; however, preliminary estimates indicate
that the 100-year population total body dose commitment per gigawatt-
year of electric power is more than an order of magnitude greater for
carbon-14 than krypton-85.. The evaluation of the proper point of
application of the control technology for C-14 is not as evident as
it is for Kr-85, where essentially 99$ of the gaseous Kr-85 discharge
originates from the fuel reprocessing plant. Preliminary data
Indicates that C-14 source terms from LWR reactors are significant in
comparison to LWR fuel reprocessing C-14 source terms.
There are many areas in which more study is necessary to be able
to more precisely estimate the impact of C-14 on man and the environ-
ment. Investigations are urgently needed for the following areas:
1. measurements of C-14 production rate and chemical form and
mechanisms affecting production such as 0-17 and N-14 present in the
fuel and coolant,
2. further measurement of carbon-14 discharge rates at reactors
and fuel reprocessing plants,
3. studies to determine the capabilities of current reactor and
fuel reprocessing off-gas systems for the control of C-14 including
measurements on the partitioning between the off-gas and liquid
process systems, possible pathways and chemical reactions and probable
decontamination factors for various systems,
4. studies to assess the availability and cost of specialized
carbon-14 control systems for use at both reactors and fuel reprocessing
plants,
36
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5. an evaluation of currently used carbon-14 world-wide
environmental transport models with special emphasis on a
sensitivity analysis of model parameters, such as exchange rates,
and inputs such as C-12 from the combustion of fossil fuels on
calculated C-14 dose equivalent contributions from LWR fuel cycle
C-14 discharges,
6. an assessment of potential C-14 concentrations in local
pathways to determine the extent of the buildup of C-14 levels
above natural background as a function of distance from nuclear
facilities,
7. an evaluation of recent C-14 internal dose studies which
may yield data more appropriate to calculating C-14 internal dose
equivalent conversion factors than the data in existing ICRP
recommendations,
8. an evaluation of the biological significance of enhanced
C-14 specific activities in the biosphere.
37
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38
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11. Hughes, Donald J. and Robert B. Schwartz, "Neutron Cross
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39
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23. U.S. Atomic Energy Commission, "Attachment to Concluding
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40
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32. Allied-Gulf Nuclear Services, "Barnwell Nuclear Fuel Plant
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41. Bacastow, Robert and Charles D. Keeling "Atmospheric
Carbon Dioxide and Radiocarbon in the Natural Carbon Cycle: II.
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Nuclear Gas Stimulation: Population Doses Estimated in the Environ-
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42
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50. Office of Radiation Programs, "Policy Statement: Relation-
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43
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APPENDIX 1
WORLD-WIDE CARBON-14 TRANSPORT MODEL
The basic Machta model described in references (38) and (39)
was modified by Magno et^al. (1) to allow estimates of tbe dose
equivalents from nuclear fuel cycle carbon-14 discharges to be
assessed. The modified Machta computer code is listed in Table 9
and a definition of symbols used in the code is presented in
Table 10. The computer program listed in Table 9 requires input
data for the annual release of fossil fuel C02 to the troposphere
expressed in 10'6 grams carbon-12 for the years 1860 to 1968. Nuclear
power fuel cycle power production data are input into the code along
with the year that the power was produced. A conversion factor is
utilized to convert the yearly power production in GWe to a monthly
discharge of carbon-14 in KCi to the troposphere. Fossil fuel
injections are projected for 1969 to 1979 using an assumed annual
growth rate of four percent and are projected for 1980 to 2080 using
an assumed annual growth rate of 3-1/2 percent. The carbon-12 and
carbon-14 input data are utilized in the Machta equations described
in reference C39) to compute net changes in world-wide compartments
since 1860 for cosmic C-14, C-12 due to fossil fuel discharges, and
nuclear power fuel cycle C-14. The seven world-wide compartments
described by the Machta equations are the stratosphere, troposphere,
tntxed layer of the ocean, deep ocean, short-term S>and biosphere, long-
term land biosphere, and marine biosphere.
Net changes of cosmic and nuclear power fuel cycle C-14 in the
tropospheric compartment are added to the initial amounts present in
1860 to calculate the total amount of C-14 present as a function of
time. These total amounts of C-14 are divided by the total amount
of C-12 present to compute C-14 specific activities in the troposphere
as a function of ttme. The specific activity (pCi C-14/gram C-12)
ta man is assumed to be the same as that calculated to be present in
the troposphere at equilibrium.conditions. Total body dose equivalent
rates due to C-14 discharges from the nuclear power fuel cycle are
then estimated for the world-wide individual and the population using
a specific activity dose equivalent model.
Magno el^ al_. (1) utilized the computer program listed in Table 9
to estimate troposphertc inventories of earbon-14 for the period
1980 to 2020 resulting from projected discharges from the nuclear industry.
Table 11 is a listing of the input data that was utilized to calculate
a carbon-14 100-year population dose commitment of 38 person-rem/Ci
from releases in 1980.
44
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TABLE 9
LISTING OF MODIFIED MACHTA WORLD-WIDE
CARBON-14 TRANSPORT COMPUTER CODE
i
DIMENSION YI (2652) * f (2652) »T 14 (2652) ,S(26b2) ,BS(26b2) ,BS14(2bb2> , 2
iriLt 265-2) ,< »UCTCI (2652) ,IYR<2652) » 4
3CF14(2652) «OCT(265*;) 5
01 ME MS I ON BBS ( 2652 > »H8L (2652) ,aMb(c:b52) ,BM(26S2) »BMl4(2652) »TB4(26 6
Ib2) »THH (2bb2) »^Mfl4 i52-;HJ./»T/2b1D2»0./»Tl4/26bc»0./»W2652»0./»BS/2652»0./» 10
^114/2652*0. /»sl*/26«>c.2*0./» TB^/26b2*U./»ZMB4/26b2*0./» 17
Ocl/2652*0./ 18
rui/2652*0./» Jrt/2652*0./,LYH/0/ 19
502 FOWf-'Af (HOA1) 20
b03 FOR'-'Af (lhl.*3UA,80--.l) 21
1SM=0 22
BCC=10. 23
IT=11 24
WEAfJ b02» (Tl FLLd) « 1 = 1,80) 2b
HRINT 503«(TITLE(I» »I=l»rtn) 26
^EAf) 100* (YI (I) ,1 = 1^,1080,12) 27
HEAD 105» (YI (J) ,J=i092,12Qb,12) 28
DO 2 I=12,1060»12 29
2 Yl (1)=YI ( l)»0.b 30
00 3 J=1306, 14b2,le 31
3 Yl ( J) =YI ( J-12) *1.0"> 32
00 4 1 = 1464, 2bt>2» U 33
4 YI (I) =YI ( I-id)*1.0 ->b 34
uO ^ J=12,2^b2»12 3b
YI(J)=YI(J)/12. 3b
K=J-11 37
.'0 H I = K,J 3d
YI (I ) =Y1 ( J) 39
tt CONT iivjUE 40
UO 7 1=1,2652 41
7 YI ( \ ) =YI (I)»l.l 42
KEAl) NUCLEAR Ow(E^ CAPACTfY, AND CONVERT TO ^KLEASE rtATE OF C-14 43
REAO(5»1210) NYK,C-':
-------
IF (LYHI.E'UO) LYR = '>YR-1
U,» 1^15 1 = 11. U 50
1215 IDI (I ) =GweM«CONV/U^.«1000«) 51
LYRrMY'H 52
IF(MYn(.Ll .NYH) GO !U 1200 53
*»* Cl & C. 57
I0=5u.,68 58
sET TU14 TO BE EQUiVftLENT TO 6.13 PLI/GM HWIOk TO I860 5^>
roi^=^94.4 . 60
XLDM=1./<1600.»1.2.) . 61
FsO.25 6i?
HL=2.4/12. 63
HS=3.1/12. 64
H*l=2./12. 65
ALIfdV = 1.016 66
ALPHl=0.9h43 67
ALPH2-U.984 68
'1.5/12. 69
CK1 )=C1«/I (1) 71
CT(1 )=CI (1) 72
998 1YR(1)=1860 73
XLLLi=0. 22/12. 74
X|_LL2 = 0. 10/12. 75
ZMO=TO*XLLL1/XLLL2 76
ZMOl4 = 0.95*T014*XLi..Ll/XLLL2 77
00=61. *TO-ZMO 78
XLMU=XLOM*DO/ZMO 79
00 30 1=2.2652 80
610 ZM2=0. 81
620 TB44l=0. 82
TB43=0. 83
AOSl^=u. 84
/M82=0. 85
T41=0. 86
Tl44i.= 0. 87
T3=0. 88
ZM143=0. 89
T143=0. 90
ZM14^=0. 91
IFd.LE .^4) GO TO --55 92
I-24) 93
4) 94
(I-24) 95
55b IF(l.Lf..36) bO TO ->66 96
T3=T(I-3o) 97
ZM14j=ZMl4(I-3b) 98
Tl43=Tl4(I-36) 99
TB43=Tb4(I-36) 10
46
-------
600 IK(I.LE.LG) GO TO I'll 101
TB441=1B4(I-LG) 102
T1441 = I !<*( 1-LG) 103
T41=T(1-LG) 104
f EQUATION 1» T(1)=C-12 IN TROPOSPHERE (10*»16 GRAMS) lOb
7/7 T(I)=TT»S14(I-1) 120
T14(Il=Tl4(l)*BCC ALLL2 »ZM(!-!)»(ZMU14*ZM14(1-1))/(ZMO*ZM(1-1)) 121
I 14(I)=114(1)-ALPHi*PL*(Tl4(I-l)/(TO»T(I-1))-T1441/(TO>T41)) 122
114(J)=T14lI)-ALPHiwPS»(Tl4(I-l)/(lO*r(I-l))-T14j/(TO+T3)J 123
oS( I )=bS(I-D *K»H'S>> ((T(I-i)-T3)/ro) 124
ciL(I)=bL(I-D ^^L- ( (T (I-l)-T4l)/TU) 12b
HS14(I)=BS14(1-1)+ALMHl*PSMT14(I-l)/(TO*f(I-l))-Tl43/(TO+T3)) 126
bL14( I) =BL14( 1-1) +.-.LPHl»PLHl»PM*( (ZM014 + ZM14 ( 1-1 ) ) /(ZMO + ZM(I-1) ) -(ZM014 128
1+ZM142)/(ZMQ*ZH2)) 129
dM(T)=0. 130
CT(I)=Cl»r(I) ' 131
DCT(l)=CT(I)-Cf(I-i) 132
UCTCI(1)=OCT(I)/ClU-l) 133
CT1MI)=C1»T14(I) 134
CI (I) =C1 +AL^H1*PL»(TH4(I-1)/(Tn*T(I-l))-F8441/(TO*T41)) 149
bMB ( 1 ) =dMH ( 1-1 ) +AL* H1»PM* (ZMB4(I-l)/(ZMO + /'/i(l-l) ) -ZMb2/ (ZMO + ZM2)) 150
CONTINUE 151
'• 47
-------
47
I2
•»
«
«
«
o
•«•
•»
•»
0
V.JOS£ = D
TTl)l = u.
CL)OSt = i)
Uo 12^0
b r i j i = o .
bh-TB = Tr
CALCULA
SPT14=(
PDOSE=|'
DU 1225
K= 1-12*
bT!)I=Sl
POP =4. 3
DOSE=TD
SOOSE=b
PD05E=P
TT!)I = 1 T
UObE=L't
COOSE=C
PHIMT 1
*
CALL EA
= 12*265c:,12
i5,lYR(J) ,Yi (J) ,CI 6 HEM /)
.
.
I=l452»265c,12
4 ( I ) / ( T ( I ) * 1 0 ) /10.
TE SPECIFIC ACTIVITY lig PCI/oM.
T14(I)*I014)/(T(I) * i(l)/. 9638
.
J=l , 12
J
01 + TO I (M
0«pxp( (i^-14S^)/(12.tt53.) )
4 (K) / (T (K) «• 1 0} /732.
OOSE+DO^E
UOSE + POP^OO-st
Ol*bTOI
bE*12.
DOSE*PD^bE
240, IYH (I ) ,brul,l TO I ,T8<*( I) , SPTB, SPT 14 ,DOSE ,
bOOSE,t"Oi-J,POOSi_,COOSti
IT
153
154
155
156
157
15H
159
160
f61
162
163
164
165
166
167
168
169
170
171
172
173
174
175
H6
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
48
-------
1240 FORMAT (IX, I4»<*A» 10 UPG10.3«2X) ) 203
100 FORMAT (IFb.O) 204
lob FORMAT 110F7.0) 205
21b FORMAT (1H ,Ib«5X,i1F9.3) 20°
Itb f-ORMAl (1H »I5»b"X»oF9.3) 207
2bO FORMAT (5HlYEAH,(HA,9H YI »9H CI »9H T »9H CT 208
i ,9H F14 «yH I^CTCI ,9H ZM ,9H M14 »9H S »9H 209
d S14 9H DCf //) 21°
2b5 FORMAT (bHl YEAr<, o7A,yn (J »9H 014 ,9H BL »9H BL14 211
1 ,9H BS »^H dSlf ,9H BM ,9H BM14 //) 212
2bb FORMAT (5HlYEA«»07Af9H Tb »9H TBR »9H ZMB4 .9H OB 213
1 ,9H BBS »^H bBL ,9H BM3 »9H SB ) 2l4
27b FORMAT (1H , I5*5X«e>F9.3) 2J5
708 bTOH 2f°
tNO 217
49
-------
TABLE 10
DEFINITION OF SYMBOLS USED IN THE
WORLD-WIDE CARBON-14 COMPUTER CODE
I = time in number of months since 1860
YI(I) = monthly release of fossil fuel C0£ in the troposphere
in 10'° grams carbon-12
NYR = end year for nuclear power discharges of carbon-14 to
the troposphere
CONV = conversion factor used to convert nuclear power
production in GW(e) to curies per year of carbon-14
discharges to the troposphere (units of Ci/GW(e)-yr.)
MYR = year of interest for nuclear power production
GWEM = electrical capacity for year of interest
TDI (I) = carbon-14 discharged per month in KCi from the nuclear
power fuel cycle to the troposphere
BCC = buffering factor which accounts for the changes in
partial pressure of C02 in the mixed layer resulting
from changes in the carbon content of the mixed layer;
taken as 10
LG = lag time in months for return of material from the
long-term biosphere to the troposphere
TO = total quantity of carbon as iCOg in the troposphere
In 1860; taken as 50.68 x 1016 grams carbon-12
T014 = total quantity of cosmic C-14 atoms as ^COg in t.he
troposphere in 1860; taken as 299.9 x 1026 atoms of
carbon-14 based on a tropospheric specific activity
of 6.13 pCi C-14/gram C-12
XLDM = fractional transfer from the deep oceans to the mixed
oceans per month
50
-------
F = fraction of land biosphere whose growth is assumed
to be C02 limited, taken as 0.25
PL = net primary production into the long-term land
biosphere on a monthly basis in 10'6 grams carbon
PS = net primary production into the short-term land
biosphere on a monthly basis in 10'6 grams carbon
PM = net primary production into the marine biosphere on
a monthly basis in 10'6 grams carbon
ALINV = 1/ALPH2
ALPH1 = fractionation factor for carbon transferring from
air or water to the biosphere
ALPH2 = fractionation factor for carbon transferring from
air to water
XLST = fractional transfer from the stratosphere to the
troposphere per month
XLTS = fractional transfer from the troposphere to the
stratosphere per month
XLLU = fractional transfer from the troposphere to the
mixed oceans in one month
XLLL2 = fractional transfer from the mixed oceans to the
troposphere in one month
ZMO = carbon content in the mixed oceans in 1860 in
grams of carbon-12
ZM014 = cosmic C-14 content in the mixed oceans in 1860 in
10^6 atoms of carbon-14
XLMD = fractional transfer from the mixed oceans to the deep
oceans per month
T(I) = net change since 1860 of the carbon content of the
troposphere due to the carbon dioxide from the man-made
combustion of fossil fuels in 1016 grams of carbon-12
ZM(I) = same for mixed oceans
51
-------
S(I) = same for stratosphere
D(I) = same for deep oceans
BS(I) = same for short-term land biosphere
BL(I) = same for long-term land biosphere
BM(I) = same for marine biosphere x
T14(I) = net change since I860 of the cosmic carbon-14 content
of the troposphere in Ifr6 atoms of carbon-14
ZM14(I) = same for mixed oceans
S14(I) = same for stratosphere
D14(I) = same for deep oceans
BS14(I) = same for short-term land biosphere
BL14(I) = same for long-term land biosphere
BM14(I) = same for marine biosphere
CT(I) = net change since 1860 of the ppmv of carbon-12 in the
troposphere due to injections of carbon dioxide from
the man-made combustion of fossil fuels
DCT(I) - monthly change of CT (carbon-12 in ppmy) in the
troposphere due to injections of carbon dioxide
from the man-made combustion of fossil fuels
CI(I) = monthly discharge of carbon-12 in ppmv to the
troposphere from the man-made combustion of fossil
fuels
DCTCI(I)= DCT(I)/CT(I-I) = ratio of monthly change of C-12 in
the troposphere to C-12 discharged on a monthly basis
as COp
TBR(I) = net change per month of carbon-14 in the troposphere in KCi of
carbon-14 resulting from injections of carbon-14 to the
troposphere from the nuclear power plant fuel cycle
TB4(I) = cumulative total nuclear power plant fuel cycle carbon-14
content of the troposphere in KCi of carbon-14
52
-------
SB(I) = same for stratosphere
ZMB4(I) = same for mixed oceans
DB(I) = same for deep oceans
BBS(I) = same for short-term land biosphere
BBL(I) = same for long-term land biosphere
BMB(I) = same for marine biosphere
SPTB = nuclear power plant fuel cycle carbon-14 specific
activity in the troposphere in pCi C-14 per gram
C-12
SPT14 = cosmic carbon-14 specific activity in the troposphere
in pCi C-14 per gram C-12
STDI = carbon-14 discharged annually in KCi from the nuclear
power fuel cycle to the troposphere
POP = world population in billions
DOSE = average world-wide individual total body dose
equivalent rate in mrem per year due to carbon-14
discharges from the nuclear power fuel cycle
SDOSE = integrated world-wide individual total body dose equivalent
in mrem due to carbon-14 discharges from the nuclear power
fuel cycle
PDOSE = annual world-wide population total body dose equivalent
rate in million person-rems per year due to carbon-14
discharges from the nuclear power fuel cycle
TTDI = cumulative carbon-14 injection to the troposphere in KCi
from the nuclear power fuel cycle
CDOSE = cumulative world-wide population total body dose
equivalent in million person-rems due to carbon-14
discharges from the nuclear power fuel cycle
53
-------
TABLE 11
SAMPLE INPUT DATA FOR THE WORLD-WIDE
CARBON-14 TRANSPORT COMPUTER CODE
KJN'*ITH iboo YEAR OCEAN 218
o.olo _ • _____ _ ..... ______________ __________________________ ______ 219
o.Ulu " "" " ' '" 220
O.oll 221
O.ull 222
o.Olc 223
0.012 224
0.013 225
0.014 226
O.ol4 227
u.'ilD 228
0.016 229
O.nlo 230
o.t.l/ 231
o.Oltf 232
O.U19 233
U.U20 234
U.021 235
• 1.022 236
u . ( i '€. 6 237
238
239
240
0.030 243
0.031 244
0.032 245
U.033 246
0.034 24J
0.036 24*8
u.035 249
0.037 250
0.036 231
M.040 252
U.04
-------
260
261
263
0.0 /b
u.J/o
G.JJfal
U.UVU
267
268
269
27U
271
272
273
!"1
o.i ou
U.IU1
276
277
A,
284
287
288
292
293
*
1
«
'•
• i
..
"
298
299
3UO
301
302
303
304
305
307
.23*
19BU
. 157
.233
1000
.0
• IbO
.243
.1
. <-
b2
60
•
•
IbB
278
.183
,28o
.195
.300
•
•
202
307
.213
.325
.225
309
310
55
-------
CASE 1.
TABLE 12
WORLD-WIDE COWITTED POTENTIAL HEALTH EFFECTS FROM CARBON-14
FOR THE U.S. LWR NUCLEAR POWER INDUSTRY
Year
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Total
LWK nibtd i tea
Nuclear Capacity
Cumulative Total
(GWe)
37.1
43.5
50.5
57.5
65.5
75.6
92.4
112.7
133.8
157.3
179.3
202.0
225.6
254.0
283.9
315.5
348.7
382.7
416.6
450.7
483.8
516.2
547.6
579.1
609.7
638.6
LWK
Produced
PowerU )
(GWe-yr)
25.6
30.0
34.8
39.7
45.2
52.2
63.8
77.8
92.3
108.5
123.7
139.4
155.7
175.3
195.9
217.7
240.6
264.1
287.5
311.0
333.8
356.2
377.8
399.6
420.7
440.6
5009.5
i.- it
Annual
Injection
(KCi/yr)
.768
_J!00
(TTo?)
T~T9
1.36
1.57
1.91
2.33
2.77
3.25
3.71
4.18
4.67
5.26
5.88
6.53
7.22
7.92
8.63
9.33
10.0
10.7
11.3
12.0
12.6
13.2
150.2
Commitment Conversion Factors
Total
45.6
46.1
N46.6
47.1
47.6
48.0
48.5
49.0
49.5
50.0
50.4
50.9
51.4
51.9
52.4
52.8
53.3
53.7
54.2
54.7
55.1
55.6
56.0
56.4
56.8
57.1
BodyU; Gonads W
(person-rem/Ci)
17.4
17.6
17.7
17.9
18.1
18.3
18.5
18.7
18.9
19.1
19.2
19.4
19.6
19.8
20.0
20.1
20.3
20.5
20.7
20.8
21.0
21.2
21.3
21.5
21.6
21.8
i.- IH
Dose
Total
.035
.041
v.049
.056
.065
.075
.093
.11
.14
.16
.19
.21
.24
.27
.31
.34
.38
.43
.47
.51
.55
.59
.63
.68
.72
.75
8.1
luu ir. rupuidtion
Commi tment
Body Gonads
(1Q6 person-rem)
.013
.016
.018
.021
.025
.029
.035
.044
.052
.062
.071
.081
.092
.10
.12
.13
.15
.16
.18
.19
.21
.23
.24
.26
.27
.29
3.1
Committed Potential Health Effects = 8.1 E+6 (total body person-rem) x 400E-6 (cancers/total body person-rein) +
3.1 E+6 (gonadal person-rem) x 200E-6 (genetic effects/gonadal person-rem)
(1) assumed capacity factor is 69%
(2) 0.21 mrem/yr per pCi C-14/gm C-12 in the total body
(3) 0.08 mrem/yr per pCi C-14/gm C-12 in the gonads
3860
-------
TABLE 13
CASE 2. WORLD-WIDE COMMITTED POTENTIAL HEALTH EFFECTS FROM CARBON-14
FOR THE U.S. LWR NUCLEAR POWER INDUSTRY
Year
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Total
LWR Installed
Nuclear Capcity
Cumulative Total
(GWe)
41.8
50.7
57.7
66.7
76.1
91.9
117.6
146.0
172.2
203.3
234.3
267.9
304.4
344.0
386.4
430.7
478.3
529.3
582.5
638.2
694.0
751.3
809.9
869.5
929.8
988.4
LWR
Produced
PowerO )
(GWe-yr)
28.8
35.0
39.8
46.0
52.5
63.4
81.1
100.7
118.8
140.3
161.7
184.9
210.0
237.4
266.6
292.2
330.0
365.2
401.9
440.4
478.9
518.4
558.8
600.0
641 .6
682.0
7081.4
C-14
Annual
Injection
(KCi/yr)
.864
1.05
1.19
1.38
1.57
1.90
2.43
3.02
3.56
4.21
4.85
5.55
6.30
7.12
8.00
8.92
9.90
11.0
12.1
13.2
14.4
15.6
16.8
18.0
19.2
20.5
C-14
Cumulative
Injection
(KCi)
.864
1.91
3.11
4.49
6.06
7.96
10.4
13.4
17.0
21.2
26.0
31.6
37.9
45.0
53.0
61.9
71.8
82.8
94.8
108.
122.
138.
155.
173.
192.
212.
C-14 100 Yr. Population
Dose Commitment
Total BodyU) GonadsU)
(1Q6 person-rem)
.039
.048
.056
.065
.075
.091
.118
.148
.176
.211
.244
.282
.324
.370
.419
.471
.528
.591
.656
.722
.793
.867
.941
1.02
1.09
1.17
11.52 4
.015
.018
.021
.025
.028
.035
.045
.056
.067
.080
.093
.108
.123
.141
.160
.179
.201
.226
.250
.275
.302
.331
.358
.387
.415
.447
.39
Committed Potential Health Effects = 11.5E+6 (total body person-rem) x 400E-6 (cancers/total body
person-rem) +
4.4E-6 (gonadal person-rem) x 200E-6 (genetic effects/gonadal
person-rem)
= 5481
1) assumed capacity factor is 69%
2) 0.21 mrem/yr per pCi C-14/gm C-12 in the total body
3) 0.08 mrem/yr per pCi C-14/gm C-12 in the gonads
------- |