L
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EPA-520/5-76-005
RADIONUCLIDE ACCUMULATION
IN A REACTOR COOLING LAKE
R. L. Shearin
R. J. Lyon
Eastern Environmental Radiation Facility
P. 0. Box 3009
Montgomery, Alabama 36109
July 1976
** v *. j. .» j
— "- THmMnf* --
U. S. ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
Waterside Mall East
401 M Street, S.W.
Washington, DC 20460
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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.
Technical reports allow comprehensive and rapid
publishing of the results of Office of Radiation
Programs' intramural and contract projects. The reports
are distributed to State and local radiological health
offices. Office of Radiation Programs' technical and ad-
visory committees, universities, laboratories, schools,
the press, and other interested groups and individuals.
These reports are also included in the collections of the
Library of Congress and the National Technical
Information Service.
I encourage readers of these reports to inform the
Office of Radiation Programs of any omissions or errors.
Your additional comments or requests for further infor-
mation are also solicited.
W. D. Rows, Ph.b.
Deputy Assistant Administrator
for Radiation Programs
iii
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PREFACE
The Eastern Environmental Radiation Facility (EERF)
participates in the identification of solutions to prob-
blem areas as defined by the Office of Radiation
Programs. The Facility provides analytical capability
for evaluation and assessment of radiation sources
through environmental studies and surveillance and anal-
ysis. The EERF provides technical assistance to the
State and local health departments, in their radiological
health programs and provides special analytical support
for Environmental Protection Agency Regional Offices and
other federal government agencies as requested.
This study is one of several current projects which
the EERF is conducting to assess environmental radiation
contributions from fixed nuclear facilities
Charles' R. Porter
Director
Eastern Environmental Radiation Facilitv
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ACKNOWLEDGMENT
The authors acknowledge the invaluable assistance
and notable cooperation provided by the South Carolina
Department of Health and Environmental Control, Bureau of
Radiological Health. The Bureau provided relative infor-
mation, consultation, and liaison services and, contrib-
uted a significant amount of manpower and field equip-
ment .
The cooperation and assistance of the Carolina Power
and Light Company employees, especially those at the
H. B. Robinson Plant, is also acknowledged. Their supply
of data resources, pertinent information and friendly co-
operative spirit helped to accomplish this work. . ••
The authors also recognize this report as a product
of the entire staff of the Eastern Environmental
Radiation Facility (EERP). Significant individual co-
operation and team'efforts contributed directly to make
this work possible. .
The EERP acknowledges the capable consultative sup-
port and field assistance provided by the• headquarters
staff of the Environmental Protection Agency, Office of
Radiation Programs, Washington, DC.
v
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CONTENTS
Page
FOREWORD., ................................ ,iii
PREFACE. , iv
ACKNOWLEDGMENT v
ABSTRACT ix
SECTION I. INTRODUCTION AND OBJECTIVES................. 1
SECTION II. STUDY SITE.....,..,....,......,...,...»..,.. 4
Power Plant 4
Sources of Radioactivity Releases.......«.,, 6
Lake Robinson 7
SECTION III. STUDY METHODOLOGY. . U
Study Design................................ 11
Lake Survey 12
Sampling 12
SECTION IV. WATER. 17
Lake Model 17
Evaluation of the Model for Tritium.... 19
Downstream Dilution of Tritium,........ 26
Tritium in Well Water., 28
Gamma Emitting Radionuclides 29
Cobalt. 29
Cesium................................. 32
Chromium. ,». 35
Manganese.............................. 35
• Iodine 35
Observations and Summary.................... 37
Additional Radionuclide Measurements,.».,,,. 37
Strontium~9 0 3J
Gross Alpha and Beta Counting,, 38
Physical Measurements in Water 41
vi
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Page
SECTION V. AQUATIC VEGETATION. 44
SECTION VI. 1ENTHIC ........................... 51
SECTION VII, FISH 56
SECTION VIII. SUMMARY AND CONCLUSION...................... 58
Behavior of Lake Components................. 58
Surveillance Techniques*..*.....*......*.*.* 62
Conclusion. 64
REFERENCES. ..........................65
APPENDIX I A-l
TABLES
1. The distribution of tritium concentration within
Lake Robinson. .......... 21
2. Paired *t" test of tritium concentrations in surface
and bottom lake water ............................23
3. Observed concentrations of tritium downstream......... 26
4. Tritium concentrations in wells,...................... 29
5. Statistical comparison of observed and predicted
concentrations of cobalt-58 in Lake Robinson water.,., 31
6. Statistical comparison of observed and predicted
concentrations of cobalt-60 in Lake Robinson water,,.. 33
7. Observed and predicted concentrations of radioisotopes
of cesium in Lake Robinson. 34
8. Average chromium-Si, manganese-54, and iodine-131
concentrations observed in Lake Robinson water........ 36
9. Gross alpha and beta activity concentrations in Lake
Robinson water.«.«.,...,* , , ......39
10. Correlation of gross beta determinations with total
specific analyses .,.40
11. Average pH and solids content of Lake Robinson water.. 42
12. Average stable element concentration in Lake Robinson
water ...,.,.43
13. Aquatic weeds observed in Lake Robinson 45
14. Environmental confirmation of radionuclides released
in liquid wastes, .,....,,...«,,,».»..,,,.,, 46.
15. Radioactive cobalt in Lake Robinson aquatic vegetation 47
16. Radioactive cesium in Lake Robinson aquatic vegetation 48
17. Radioactive iodine and strontium in Lake Robinson
aquatic vegetation. •• .49
via.
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Page
18» Radioactive chromium and manganese in Lake Robinson
aquatic vegetation...,«...»...»,,...».,., 50
19. Radioactivity in Lake Robinson sediments,»......«..,.» 52
20. Radioactivity in Lake Robinson fish 57
21. Projected range of equilibrium concentrations at
various lake flows.«.»*..»*.*.....»..»,*,**...*.*..... 60
22. Projected range of doses to an adult swimming 50 hours
in expected concentrations.,...........»........*....» 61
FIGURES
1» Schematic of H, B, Robinson Unit 2 Power Plant, 5
2. H. B. Robinson Unit 2 liquid waste disposal system..,. ?
3, Geographical location of Lake Robinson 9
4. H. B, Robinson site,..»»,,.........,....»....«,.. 10
5. Important radionuciide pathways to man via surface
water. 11
6, Components of reactor-lake system.........,.,.......,, 11
7. Environmental sampling sites in Lake Robinson 14
8. Principle dynamic factors reacting within the Lake
System 17
9. Predicted and observed tritium concentrations in
Lake Robinson. ........,,,....,.. 20
10. Observed and predicted concentrations of cobalt-58 in
Lake Robinson.»,..,.. 30
11, Dredge sampling locations in Lake Robinson,.....,,.,.. 53
12. Radioactive cobalt in sediment (position a),.,..,....» 54
13. Radioactive cobalt in sediment (position b)........... 54
14, Radioactive cobalt in sediment (position c)........... 54
15. Radioactive cobalt in sediment (position d)........,., 55
16. Radioactive cobalt in sediment (position e).»...*,...* 55
17. Radioactive cobalt in sediment (position f)........... 55
A-l. Gross power generated (7) A-2
A-2. Liquid radioactive waste releases of tritium (7).,.,,.A-2
A-3. Liquid radioactive waste releases - non-tritium (7),.,Ji-3
A-4. Lake Robinson discharge rates (6)... .A-3
vxn
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ABSTRACT
In the utilization of a cooling lake for a commer-
cial power reactor, low-level quantities of liquid waste
are released to the lake water. Due to the retention and
recycling of water for condenser cooling purposes,
concentrations of radionuclides can increase to levels
which are directly measurable in the water. Such a site
design is represented by the H. B. Robinson Unit 2
operated by the Carolina Power and Light Company at
Hartsville, SC.
For a 4-year period lake water and other lake com-
ponents such as fish, aquatic vegetation, and benthic
sediments were sampled and analyzed to determine if any
long-terra buildup occurred. Results indicated that the
lake water concentrations followed general mixing
equations and that turnover rates in the individual com-
ponents of the lake were too short to quantitate with
this study design. This indicates that concentrations of
radionuclides in the lake would be primarily a function
of parameters such as radioactivity released and lake
flow for the previous year and essentially independent of
earlier parameters. An estimate of annual external doses
to an individual utilizing the lake for recreation (i.e.,
swimming, boating, and fishing) would be about 5
microrem.
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SECTION I
INTRODUCTION AND OBJECTIVES
Nuclear power plants generate large quantities of
radioactive wastes. These wastes are primarily fission
products of the fuel ands secondarily activation products.
The majority of the fission products are retained within
the fuel elements until removed during fuel reprocessing,
A relatively small quantity of fission products and acti-
vation products accumulate in the primary coolant. Most
of this radioactive waste is concentrated and removed for
off-site shipment and controlled disposal. Small quan-
tities of low-level radioactive wastes which cannot be
efficiently processed or contained are released to the
environment, in liquid and gaseous forms.
Quantities of radioactive wastes released to the
environment have generally been much below the 10CPR20
limits established by the U. S. Atomic Energy Commission,
currently the Nuclear Regulatory Commission (NEC). More
recently, stricter dose and release design objectives
have been imposed in the form of Appendix I to 10CFR50
(1), In general, these design objectives are about a
factor of 100 below 10CFR20 (2) limitations and represent
a greater compatibility with actual reactor operating
experience. With the proliferation of nuclear power, a
point of major concern is the long-term buildup in the
environment of long-lived radioactive wastes. This
buildup will occur when the rate of accumulation exceeds
rate of disappearance for a particular radionuclide.
Such action increases the concentrations of radioactive
waste in one or more compartments or locations of the
environment.
Many nuclear power plants- utilize large volumes of
water to disperse low quality waste heat from their power
system. These volumes of water are also conveniently
available for dilution of small amounts of radioactive
wastes which are considered of such low hazard potential
as to be impractical for holding in radioactive waste
storage. Dilution further reduces the environmental
hazard. A common reactor site design has been to use a
river or estuary for water source and disposal. Such a
system releases radioactive materials to the environs in
such dilute concentrations that positive environmental
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measurements are extremely difficult with current
analytical techniques.
A second type of siting design is the impoundment of
a stream to create a large reservoir. The reservoir acts
as "both the cooling water source and the receiving water
body for the'liquid radioactive waste discharges, water
is circulated through the power plant's main condenser
and the lake several times before it continues down-
stream. For this design, concentrations begin to
approach the detectable limits of the best analytical
methods available. This siting design was chosen in this
study to provide data yielding a more definitive deter-
mination of radionuclide behavior. - The determination can
produce a reasonable basis for projecting environmental
cost in terms of radiological contamination of the envi-
ronment .
The particular site chosen for the study is the
H. B. Robinson Plant near Hartsville, SC» operated by the
Carolina Power and Light Company, The plant consists of
a- 185 MWe coal-fired- unit and a 739 Mw"e (gross)
pressurized light-water reactor unit. The plant uses
cooling water from a reservoir formed by a dam on Black
Creek. The resultant reservoir interfaces with the
larger aquatic system of Black creek through the creek
inflows and the dam overflows. Such limited connections
facilitate a demarkation of the system under inves-
tigation.
The specific objectives of this study were:
1. To identify and quantitate any long-lived
radionuclides released to the environment by
the nuclear plant;
2. To determine the concentration of such radio-
nuclides in representative environmental
samples of the lake system;
3. To determine the rate of radionuclide buildup
within the various components of the lake
system;
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4. To extend any observed buildup rates through
the expected life of the reactor in order to
evaluate the impact of the power plant on the
general public and the environment.
The study design was based on the approach which was
applied to man by the International Commission on Radia-
tion Protection (ICRP) (3), The ICRP described the
existing quantity of radioactivity in man as his body
burden and then expressed the content within particular
organs in terms of fractions of the total body burden.
These fractions were then accepted as equilibrium con-
stants and constituted a simple mathematical model which
became the basis for various Radiation Concentration
Guides. In a lake system it is recognized that these
fractions are not constants but dynamic variables which
change with time due to external forcing functions. This
study was designed to identify and describe the principle
forces that govern the transfer and storage of radio-
nuclides in the lake compartments of water, flora, fauna,
and benthos. Their actions are formulated in a mathe-
matical expression such that transfer coefficients can be
determined for a given set of forcing function parameters
such as waste release data and lake flow data. Using
time increments of at least a month, erratic day-to-day
variations were smoothed to a general trend curve. Thus,
a macroscopic analysis rather than a microscopic analysis
was chosen which would then supply information directly
applicable to a dose-to-man model.
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SECTION II
STUDY SITE
•jjower JPlant
The H= B. Robinson electric power generation
facility at Hartsville, South Carolina, is owned and
operated by the Carolina Power and Light Company. The
facility is composed of two units: Onit 1, a 185 MWe
fossil fuel plant and Unit 2r a 739 MWe pressurized water
reactor. Unit 2 constitutes the entire source term for
radioactive materials released in this study. A low
power operating license (<5MWt) was issued July 31 , 1970.
Initial criticality was achieved September 20, 1970, and
authorization to operate the unit at full power (2,200
MWt} was obtained from the AEC on September 23, 1970. H.
B. Robinson Unit 2 was declared to be in commercial oper-
ation on March lf 1971 (See figure A-1, appendix I)
Westinghouse Electric Corporation provided both the
Nuclear Steam Supply System (NSSS) and the turbine-
generator system. The NSSS includes a pressurized water
reactor, the reactor coolant system (RCS) , and associated
auxiliary fluid systems (figure 1}". Although designed to
initially produce 2r200 MWt (739 MWe gross), the power
train for H. B. Robinson Unit 2 is expected to be ulti-
mately capable of producing 2,300 MWt.
The reactor core features a typical three-region
cycled core. Fuel rods are cold-worked zircalloy tubes
containing slightly enriched (1,85 to 3.10 weight
percent) uranium dioxide fuel. A total of 79,561
kilograms of uranium dioxide fuel is loaded into the 157
fuel assemblies contained in the core (4) .
Three closed but interconnected reactor coolant
loops , each containing a reactor coolant pump and a steam
generator, comprise the bulk of the reactor coolant
system, A pressurizer, a pressurizer relief tank, con-
nective piping, and instrumentation are also provided.
Auxiliary coolant systems include the Residual Heat
Removal System (RHRS) , the spent fuel pit cooling system,
and the component cooling system. The RHRS cools the
reactor coolant system during shutdown procedures while
the component cooling system cools the reactor coolant
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system when shutdown is accomplished. During the power
operation the component cooling system cools the reactor
coolant system letdown flow to the Chemical and Volume
Control System (CVCS) as well as other primary plant com-
ponents. Other auxiliary fluid systems exist to provide
a safety function and plant performance information (sam-
pling systems) .
The turbine-generator system is the secondary cool-
ant system and is composed of the shell side of the
vertical 0-tube steam generators, the turbine generator
equipment, two condensers, feedwater apparatus, and asso-
ciated piping. Steam produced in the steam generators is
sent to the turbine-generator to produce electricity.
Steam from the turbine is condensed and deaerated at the
condenser, heated, and pressurized by 'the feedwater
system, and routed back to the steam generators.
The excess heat of condensation from the secondary
coolant loop is transferred to lake water' using a heat
exchanger as a steam condenser in the coolant loop fol-
lowing the last generating turfcine stage. This is accom-
plished by removing lake water from near the dam, cir~.
culating it through a heat exchanger at rates up to 29.7
m3/sec and returning it to the upstream portion of the
lake through a 6,7 kilometer cooling canal.
Nuclear Steam Supply
Station (NSSS) Turbine
Steam Generator
Reactor ^S^^~*N
Vey^ Iff
•
Core jta
\ ******
'„..
\ 1 Typical , i
^- — •/ Coolant i "*"b
Loop | /
(total = 3 loops) (F
|
Steam
1
Generator System
.. Turbine
r>CL^
" L
" ~ — | Generator
•J^ 1
J To Lake
I r
(
}! F i : 1
f Condenser
-r-r-z-^ L
7 1-3^
"eed'A'ater i
Pumps &, 1
Stater/
'——Primary Secondary
Coolcnt Coolant
! t
ler i :
f'
Lake Cooling1-? \V: ,
V¥ater . / Cooling \ i
I Water J i
\Pumps /
", ,
Wat
Cooiing
tr
Figure 1. Schematic of H. B. Robinson Unit 2 power plant
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Sources of Radioactivity Releases
As fuel burnup occurs fission products increase in
the uranium oxide matrix which serves as an initial con-
tainment barrier. The zircalloy cladding of the rod pro-
vides the next barrier to fission product waste trans-
port. A third barrier to its release is the enclosed
primary coolant loop which also provides neutron modera-
tion and heat transfer capability to the power generation
loop. The primary coolant loop scavenges much of the
fission product leakage and much of the radioactive
;neutron activation products that become transferrable.
The water in this loop also contains a chemical shim,
boric acid, to provide for control of the additional
reactivity within the core. The primary coolant circu-
lates through the core in three parallel distribution
systems, each driving its own steam generator. Decon-
tamination and chemical adjustment controls on the pri-
mary coolant are provided by the Chemical Volume Control
System (CVCS) which utilizes ion exchange techniques to
control and reuse the water as well as to provide-make-up
water for the primary coolant loops. A single CVCS sup-
plies and maintains the three primary loops. The primary
loops operate at about 154.1 bars and are driven by a
pump in each loop.
Sources of liquid waste occur as minor and major
leaks develop in seals, flanges, and other necessary and
'inadvertent openings. Shutdown, opening, and repair of
the system and its supportive equipment, also/ provide a
mechanism for release of liquid radioactive waste.
Equipment leakage is collected in the reactor coolant
^drain tank and is usually routed to the 'boron recovery
subsystem of the CVCS. Liquids from the CVCS holdup
tanks are pumped through • ion exchangers (for lithium,
cesium, molybdenum, and yttrium removal), a filter, and
the gas stripper. Degassed liquid,from the gas stripper
is then evaporated in the boric acid evaporator conden-
sate demineralizer and filter, and accumulated in the
CVCS monitor tanks. This liquid may then be sent to the
primary water storage tank for reuse, to the evaporator
condensate demineralizers for the CVCS holdup tanks for
further treatment, or it may be discharged. Miscellane-
ous leakages are collected in the containment sump and
usually routed- to the waste holdup tank in the liquid
waste disposal system (figure 2). These leakages amount
to only a few liters per minute
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to dfvmmlng facility
Figure 2. H, B. Robinson Unit 2 liquid waste disposal system
The secondary coolant loop which is a water-to-steam
loop contains lesser quantities of radioactivity than-the
primary loop. This radioactivity is the result of
inadvertent leakage across the barrier between the pri-
mary and secondary systems. The secondary loop contains
323,300 liters of water at 2200 MWt operation. Since the
water chemistry in the secondary loop is closely con-
trolled in a manner similar to that of the primary loop,
a continual amount is removed. Although the concentra-
tion of these radioactive wastes may be"less than that of
liquids from the primary coolant, the larger volumes may
make this release significant. There are other miscel-
laneous liquid radioactive waste sources. These are col-
lectively summarized in figure 2 and include additional
locations such as radioactive laboratory drains, fuel
handling building drains, and laundry and hot shower
drains, all of these sources can be fed into the liquid
waste .disposal system.
Lake Robinson
Lake Robinson is an impoundment of Black Creek com-
pleted fcy Carolina Power and Light Company in 1957 to
provide a source of cooling water for the H. B. Robinson
power production facilities. The impoundment is located
in the southern sand hills region of northern South
Carolina and detains water from a watershed of 443 square
kilometers,
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The lake has a north-south orientation with the dam
located' at the southern end of the impoundment. The 911
hectare lake contains about 3.8 x 107 m3 of water. This
volume is considered constant since its variations are
generally less than 20 percent, or well within the
experimental error of this study. Forced evaporation due
to the thermal loading on the lake effects loss of water
at rates of ,4 to .6 m3 per second. Water discharge
varies seasonally relative to rainfall. The average
discharge rate is 4.8 m* per second, but this varies
daily from low rates of .74 m3 per second to higher rates
of 31 m3 per second (ft). This varying discharge rate is
a major parameter in the racliomiclide budget of the lake
(See figure ft-4 of appendix I)» The discharge flows into
a smaller impoundment, Prestwood Lake, about 8 kilometers
downstream. Prestwood Lake supplies water to several
industrial users for manufacturing processes. Neither
Prestwood lake nor downstream Black Creek is used as a
supply of drinking water.
Lake Robinson was constructed on land which
contained primarily second growth pines, bottom lands,
swamp, and some hardwoods. The shoreline consists of
grasses, pine seedlings and granite fill used for erosion
control. The lake is approximately 12 kilometers long
from north to south with a mean width of .8 kilometers.
The lake has a basin 12 to 18 meters deep at the
southern end near the dam. The old creek 'bed forms a
twisting channel 6 to 8 meters deep near the basin but
only 3 to 4 meters deep near the bridge at the upper end
of the -lake. On either side of the channel lie extensive
"shallow" flats which cover significant areas with depths
of 1 to 2 meters. North of the bridge the area is
flooded hardwood land with a treacherous bottom littered
with'decaying debris such as stumps and dead trees. The
feedwater of Black Creek passes through several bogs or
marshland areas acquiring the "brown water" coloration
from the humic acids of these areas.
Lake Robinson, therefore, has attained the charac-
teristics of a "bog lake" or "trown water" lake as de-
scribed by Ruttner (5), Such characteristics include low
nutrients, low pH, and high discoloration. The biologi-
cal productivity of the lake could, therefore, be pre-
dicted as being relatively low.
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Lake Bobinson is available to the general public and
is used for recreational purposes such as boating, water
skiing, sport fishing, and swimming. Numerous private
residences have been built on the eastern shore of the
lake. Figure 3 and figure 4 present the location and the
arrangement of lake* creek flow, and reactor.
Atlantic Ocean
Figure 3. Geographical location of Lake Robinson
9
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H, B, Robinson
Units:
site boundary
Lake Robinson
dam
Black Creek
Figure 4, H« B. Robinson site
10
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SECTION III
STUDY METHODOLOGY
St.ud% Design
The approach to this study began with a generalized
model or grouping of the components of the lake system
and the dominant environmental factors interacting with
the system. Figure 5 represents the important
radionuclide pathways to man selected as the bases for
the design of this study. The model is applicable to
liquid releases to most, aquatic ecosystems. Figure 6
depicts the salient relations of this particular system.
From such a grouping the study design was developed to
either measure or infer through simulation, the signifi-
cance of each particular interaction or component stor-
age. The stepwise approach was to use observed data to
guide subsequent alterations in the study design so that
system characteristics would emerge as the research pro-
gressed. An example of this was the utilization of
tritium data to verify physical attributes of the lake
such as lake volume and mixing properties.
radioactive
material
i
surface
water
<•»!•*
sediment
aquatic
plants
U« , 1 1
~* 1
t 9,
•»• ihaestfon
aquatic
animals
\
j
Figure 5.
Important radionuclide pathways to man via surface
water
plant I
I plant
discharge
creek
water
1
lake
water
!
lake
efecharge
lake
flora
2
L
r
Iteke
benthos
lake I
fauna I
Figure 6. Components of reactor-lake system
11
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Lake-flow data from the United States Department of
Interior (6) , physical ' parameters used in the environ-
mental evaluations .by the Carolina Power and Light
Company (4) , effluent release data, and other operating
data as reported by the Company |7) were vised to develop
a dynamic picture of the system. This dynamic picture
was evaluated by a series of 10 surveys spaced over a 4-
-•year period. Thus, the effort was similar to taking a
series of 10 in-depth, still photographs over a 4-year
period to represent a complex, dynamic system in motion
on a macroscopic scale. The intent was to determine con-
tent of radioactive pollutants within the components
represented in figure 6 and observe the effect of flows
or transport between the components,
L_ake Survey
Lake Robinson represents the focal point of this
study. In order to acquire an adequate radiological
"portrait" of the lake, an in-depth field survey protocol
was developed. Each element of the survey was chosen to
provide data on the radionuclide content of an ecosystem
component and associated parameters which might monitor
physical and biological actions within the system. The
sampling strategy was to collect numerous small volume
samples for radionuclide analysis of readily detectable
nuclides and fewer but larger volume samples for radio-
nuclides which occurred in smaller concentrations and
were more difficult to detect. The analytical data was
correlated with analyses of reactor waste streams and
lake flows. The surveys were spaced from 3 to 6 months
apart to provide adequate time increments such that mea-
surable changes could occur.
The sampling protocol was directed towards determin-
ing the radionuclide content of the water, benthic soil
and sediments, aquatic flora, and aquatic fauna. The
primary effort was to sample for positive indications of
radioactivity. To implement the protocol, a team of at
least four EPA field survey members was required, along
with the assistance of Carolina Power and Light Company
personnel and two technicians from the • South Carolina
Department of Health and Environmental Control, Bureau of
Radiological Health, The surveys were conducted on 3
successive days and required the use of a specially
equipped 4.3 meter outboard motor boat and a varied quari-
12
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tity of sampling equipment arid operational gear. In the
course of each sampling trip, approximately 100 environ-
mental and in-plant samples were taken. The sampling
program required that not only the lake itself be
accurately represented, but also that effects downstream
be identified, transport to the underlying aquifer be
evaluated, and background radioactivity data be obtained
either from points upstream and unaffected by the reactor
or from a nearby lake of similar nature, also unaffected
by the reactor.
The major emphasis in the survey was the evaluation
of the lake water itself. To accomplish this, three sam-
pling systems were established to provide for varying re-
quired sensitivities for the different radionuclides and
for better determination of physical distribution about
the lake.
The first system was established for analyzing tri-
tium in the lake water. Since it was expected that tri-
tium concentrations would exceed the minimum detectable
limits of .2 nCi/liter after the reactor had operated for
about 9 months (8) a simplified analytical method could
be used. This permitted the analyses of a large number
of samples. The system for tritium samples consisted of
23 lake sampling locations. Nineteen of these locations
were on the center line of the lake beginning at the dam
and extending uplake with a separation of about ,5
kilometer. Four sites were located on a cross section
line of the lake at the sixth site north of the dam or
about 2.7 kilometers. This provided five locations
evenly spaced across the lake from shore to shore. At
each location two 1-liter samples were drawn, one near
the surface and one just above the bottom (approximately
.5 meter). In addition to determining tritium concentra-
tions, this system was designed to provide information
relative to lake mixing and lake volume. The 1-liter
sample size was chosen to provide adequate quantity of
samples for replicate analyses. The normal analytical
procedure required 100 milliliters of water per analysis.
The second water sampling system consisted of eight
sampling sites up the center of the lake. The sample
size for this set was 19 liters. The samples were drawn
from 1 to 2 meters deep. The sites began at the darn with
three in the lower lake area at .8 kilometer intervals
and five in the upper lake area at .8 kilometer inter-
vals, one centerlake opposite the mouth of the discharge
13
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canal, two north of that point, and two south of that
point. This sample set provided measurements at an
intermediate level of sensitivity for all gamma emitting
radionuclides as well as strontium-89, strontium-90, pB,
stable elements, and dissolved and undissolved solids.
A third sampling system was established to provide
maximum feasible sensitivity of measurement of gamma
emitting radionuelides in the water by using a sample
volume of 200 liters. These sampling sites were: two in
the lake center .8 kilometers above and below the mouth
of the discharge canal, two in the lower lake ,8 kilo-
meters and 2.^ kilometers north of the dam at the lake
center, one at the cooling water intake, one at the cool-
ing water discharge to the canal and one at the mouth of
the discharge canal. A background sample of this size
This was initially drawn from Black
1 highway bridge. Later it was
the background sampling point to
This small lake had chemical char-
to Lake Robinson, but received no
was also taken.
Creek at the U. S.
decided . to move
Beaverdam Millpond.
acteristics similar
surface drainage front the H. B.
figure 7 on sampling locations).
Robinson Unit 2 (See
scale
1 km,
I ;——«
D
visitors center
discharge canal
"bridge
legend
a = 200 liters of water for resin cartridge
0=1 liter of water for tritium analysis
A = 19 liters of water, sediment,
vegetation is collected where available in Sake
Figure 7. Environmental sampling sites in Lake Robinson
14
-------
Benthie soils or silt samples were collected with a
Peterson dredge at the eight locations selected for the
19-liter water sample system. The dredge "bite" repre-
sents .078 m*. A single sample represented two bites or
.156 m2. The sample was dried, weighed, and analyzed by
gamma spectroscopy (gamma scanned),
Aquatic vegetation was collected in the littoral
areas as near as possible to the eight locations selected
for 19-liter water samples 'and benthic soil samples. The
priority of choice of -vegetation was submerged weeds,
floating weeds, and emergent weeds, of the submerged
weeds, Myriophylum was one of the available species and
Najas flexilis was another. Of the floating weeds,
Braesnia was most commonly selected. Assistance in plant
identifications was provided by the Biological Services
Branch of the EPA Environmental Research laboratory,
Athens, Georgia, These were washed, drain-dried,
weighed, gamma scanned, ashed, weighed, and gamma scanned
for the second time."
Fish samples were supplied by the South Carolina
State wildlife Department and South Carolina Department
of Health and Environmental Control personnel who used
electrical shocking to collect fish. Because of'the
techniques employed and because of a low population of
fish, significant sample sizes were not available to
correspond with each field trip. When fish were
available, they were separated into sets of species, each
set being counted separately. Large individual fish and
large numbers of single species were separated into
viscera, bone, and flesh; then, analyzed,'
At the inception of the study, the power plant
reported liquid releases in curies of tritium and "non-
tritium" on a monthly basis. This hampered isotopic
evaluation; therefore, with the assistance" of Carolina
Power and Light, liquid wastes samples, proportioned to
the quantity released, were collected and analyzed to
estimate isotopic releases. By July 1972, Carolina Power
and Light Company began reporting specific radionuclide
releases. After an overlap of procedures demonstrated
close agreement between composite release estimates and
the power plant's reported releases, the composite system
was dropped in January 1973.
Other in-plant systems were sampled in order to pro-
vide a potential insight as to the sources of liquid
15
-------
wastes within the plant. This included samples from
available sampling points in the primary coolant, CVCS,
secondary system, and other miscellaneous systems such as
the component cooling water system. Information at these
points gave a more complete picture of the extent and
significance of these systems in total liquid releases.
All in-plant samples were taken by plant personnel in
accordance with their established procedures, with sample
size determined by expected concentrations and available
sample quantity.
In addition to these major sampling procedures,
several peripheral programs were implemented to provide
information connecting the lake system, the reactor, and
the surrounding environment. One such effort was the
sampling of 10 private drinking water wells at residences
bordering the lake. One-liter samples were taken for
tritium analyses to detect any significant transport from
the lake to the water supplying aquifer. 'Additional sam-
pling was initiated downstream on Black Creek to deter-
mine the dilution and dispersion as the flow travels
downstream'. Midway through the study, Carolina Power-and
Light Company suggested that a drainage ditch leading
from the reactor directly to a point below the dam should
be monitored. Subsequently, water and vegetation in this
ditch were sampled when available. The effects of flow
down the cooling canal and through two side pools on the
cooling canal were also monitored. Water, sediments, and
littoral vegetation were sampled at this location.
16
-------
SECTION IV
WATER
Lake Model
The simplest description of the turnover of radio-
activity in the lake is one derived from the major
physical aspects of the lake system. The model is
similar to a continued insertion of a radionuclide into a
tank with an inflow and a discharge rate. Figure 8
represents this in block diagram form.
evaporation
creek flow
lake discharge
reactor wastes
Figure 8. Principle dynamic factors reacting within the
Lake System
The mathematical expression for the change in radio-
activity in this lake would be as follows:
da
dt
Where:
dA
dt
A
P
Qflow
^evap
= P -
V
~ Fate of change of radioactivity in the lake
= Radioactivity in the lake
= Rate radioactivity is added to the lake
= Rate of water discharged from lake
= Bate of evaporation from the lake
= The radionuclide decay constant
= take volume
17
-------
In order to reduce the expression to a more manage-
able form the effective removal rate is defined as:
xeff = Qflow + Qevap + xi
~~~VV
Thus the differential equation is expressed as:
(Equation 1)
|f - -*.ff.tA
This equation integrated becomes:
&0 = Radioactivity in the lake at the beginning of
time period "t"
h± = Badioactivity of radiomielide "i" in the lake
at the end of the period
Expressing this in terms of concentration of an "i"
radiomielide, the equation becomes:
(Equation 2)
C± = Pj (l-e"xeff,it) + C0e~Aeff,it
i
It should be observed that the equation and its
application implies several assumptions:
1. The lake volume is assumed constant. This
assumption seems reasonably valid based on lake data (9)
which shows the lake level has a limited variation. The
value used was 3.8 x 107 m3.
2. The radionuclide release rate is constant
throughout the period of concern. This was a necessary
assumption due to the lack of records on times, dates,
and quantities of releases. The official records show
total releases for the month and do not detail when
specific releases occurred. In general these releases
were of sufficient number and quantity to be reasonably
approximated by the constant rate assumption.
18
-------
3, Rapid mixing occurs in the - lake to establish
uniform concentrations. This is not an unreasonable
assumption since the cooling water pumps move the lake
water at 29,7 m3/see through the main condensers and down
the discharge canal as compared to an average lake dis-
charge of ^.8 m3/sec.
tt. The loss or removal from the lake by evapo-
rative transport was applicable to tritium only. For
other radionuclides this did not constitute a significant
radionuclide transport mode and was, therefore,
neglected,
5, There is no other significant storage or escape
route from the lake water. This assumption is apparently-
valid for tritiums however, possible departures for other
radionuclides will be discussed later.
Evaluation of the Model for Tritium
Tritium appeared to be a natural tracer for the
evaluation of the water turnover model represented
by equation 2. The primary form of the tritium was
HTO and, therefore, the tracer behaved chemically
and physically like water. Additionally, liquid
releases would be expected to be in sufficient quan-
tities that the resultant concentration in the lake
could be easily measured by sufficiently simple ana-
lytical procedures so that numerous samples could be
processed to provide a solid broad data base and
increase power of the statistical tests.
The model is compared to the observed lake
values over the 4-year period to observe the corre-
lation between the predicted and observed values.
Figure 9 shows a comparison of observed and calcu-
lated values for the duration of the study.
The calculated values were determined using the
release rates reported by the company in their
operating reports (7) for the respective month and
an initial concentration as calculated for the end
of the previous month. The flow data was that pro-
vided by the United States Department of the
Interior, Geological Survey, in Columbia, SC, for
the gaging station 102130910 located 305 meters
below the Lake Robinson dam (6)« The mean monthly
flow observed for the specific month in question was
-------
used. The concentration was determined from the
selected month's data and plotted, as the concen-
tration in the lake existing on the first day of the
next month.
U 2
legend
predicted
* observed
1971
1972
1973
1974
Figure 9. Predicted and observed tritium concentrations
in Lake Robinson
20
-------
Table 1
The distribution of tritium concentration within Lake Robinson
nCi/1
Trip No. of
Date Samples Mean
Max Min
S.D.
Percent
Observations .
Analytical in Analytical
Range
I
12/01/70
II
03/09/71
III
09/21/71
IV
03/14/72
V
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
<
46
46
46
43
41
50
41
43
43
43
<.2 <.2 <,2 ± .2
•28 .4 <.2 .11 ± .2
•47 .6 .3 .08 ± ,2
1-69 1.9 1.1 .14 ± .2
2-18 2.5 1.1 .22 ± .2
3-05 3.4 1.6 .33 ± .2
1.15 1.4 .4 .28 ± .2
•61 -9 -4 .10 ± .2
3-70 4.8 2.9 .27 ± .3
2.65 2.9 2.2 .14 + .7
100
100
100
91
93
72
78
95
88
as
05/14/74
21
-------
Two sections of the figure show significant
disagreement between the observed and predicted
values. The period of May-to-September of 1971
shows observed concentrations from .5 -to .7
nCi/liter as compared "to predicted values of about
.2 nCi/liter. These observed values represent
duplicate analytical runs on separate dates. Unless
contamination of the sample occurred in the field,
there is strong indication that they are correct.
During the time period from May 29 to August 20,
1971, the reactor was shut down for extensive gener-
ator repairs as well as for other numerous mainte-
nance operations. It might be-reasonable to suspect
that recorded releases were in error. Another plau-
sible explanation is that extensive stratification
was occurring due to the reduced operation of the
circulating cooling water pumps during the shutdown,
Such reduction undoubtedly would affect the lake
mixing action and consequently reduce the effective
mixing volume of the lake. Consequently, the
observed concentration would appear higher than
expected. This effect, however, would show a faster
turnover rate which was not apparent.
A second significant discrepancy occurred in
February 1972 where predicted concentrations reached
3.4 nCi/liter and observed concentrations reached
about 1.8 nCi/liter. It is believed that this is a
question of timing of releases and the month-
grouping method of handling the data. Thus, the
peaking described by the model could have occurred
between or prior to the two 1.8 nanocurie samples.
Aside from the aforementioned sections of the
study, the predicted and observed concentration
values demonstrate excellent agreement. Such agree-
ment seems to recommend the acceptance of the model
and its parameters as a valid simulator of the water
behavior of the lake. This infers that the stated
assumptions are likely valid.
The assumption of adequate lake mixing seemed
to require further evaluation. Table 1 summarizes
the observed data for tritium showing -the number of
observations, the mean, maximum, and minimum values,
the standard deviation, and the percent of the
observations contained within the range of the mean
plus and minus the stated analytical error. From
22
-------
this table it should be noted that the data points
are well clustered about the mean within the range
of the analytical error.
In an effort to test the effect of stratifica-
tion of water, a paired "t" test was used to test
the hypothesis that surface water samples had values
from the same sample population as water samples
taken near the bottom of the same lake location,
•The test was a two-tailed test at ' the 95 percent
confidence level. Multiple "t" tests are summarized
in table 2. Nine trips had sufficient positive data
to analyze.
Table 2
Paired "t" test of tritium concentrations
in surface and bottom lake water
n = 179 pairs
D = 0.067 nCi/liter
SD = 0.284
a = .05 -
Degrees of Freedom = 178
Ho: Surface Cone. - Bottom Cone. = 0
Test Statistic
fc = 0-067 (17S)% = 3.15
0.284
t - t (.025) = 1.96 < 3.15 Ho: rejected
{a/2)
Alt Ho; Surface Cone. > Bottom Cone.
Alt Ho; Accepted
23
-------
The test, used 179 pairs of observations which
indicated that tritium concentration in surface
water exceeded that of deep water an average of .067
nCi/liter, The sample standard deviation (SD) =
,284, degrees of freedom = 178, and the test sta-
tistic "t" = 3.15. Since 3.15 is greater than 1.96,
the hypothesis that the difference was zero, was
rejected and the alternate hypothesis that the dif-
ference was greater than zero was accepted. Such a
hypothesis indicates that some physical stra-
tification does take place as the lake receives the
small amounts of radioactivity mixed with water
which is at a temperature elevated above ambient
lake temperatures. In general, it is important to
note the magnitude of this stratification. In this
particular test the average concentration was 1.75
nCi/literr and the average observed difference was
.067 nCi/liter or less than 4 percent of the average
observed concentration. The difference is about
one-third of the minimum detectable concentration
for tritium of ,2 nCi/liter, The treatment of the
lake by> the model as'a mixed lake should not intro-
duce an error greater than the errors introduced by
sampling and analysis and thus the mixed lake
assumption is realistic for the purposes for which
it was intended,
This comparison seems to verify the model as a
plausible description of dilution within the range
of analytical error. It is, therefore, concluded
from these comparisons that equation 2 adequately
describes the water mixing properties of the lake
within the overall measurement error of the study
and that the constant lake volume of 3.8 x 107 m3 is
a valid assumption. It is also concluded that the
mixing of the water is sufficiently effective to
support the uniform mixing assumption over time
periods of weeks or greater. A subsequent inference
is that long-term buildup of the tti" radionuclide in
the water based on the model would reach an equi-
librium or "steady state" value given by:
-------
(Equation 3)
equilibrium
The highest release rate of tritium reported
during this study was for December 1973 at 79.2^
Ci/mo. Such a release rate would result in concen-
trations from .8 nCi/liter to 4 .8 nCi/liter depend-
ing on the lake discharge rate. The highest concen-
tration observed from a single sample in the lake
was 4.8 nCi/liter on- November 6, 1973, This is
.16percent of 10CFR20 (2) , guideline for radioactive
"effluents to unrestricted areas." The highest
tritium concentration representative of the lake was
3.7 nCi/liter or .1 percent of Appendix B guideline
(2) , Thus the radioactive waste concentration
buildup is controlled by lake flow, radioactive
decay rate, and the discharge rate of the radio-
active pollutant. For long-lived radioisotopes with
half-lives of greater than a year, the lake flow
rate is the dominating factor which affects buildup
for a given radioactive discharge rate. Data from
October 1966 to September 1974 on the average
monthly lake flow shows that this parameter might
vary from 2.27 m3/sec to 13.65 m3/sec causing the
"half-life" time of a particle of water to vary from
23 days to 136 days. Thus the maximum buildup of a
long-lived radiontaclide could be determined by;
(Equation 4)
pi
__
Where:
Pj_ = Belease rate of nuclide "i"
Q = Lake flow rate
25
-------
Downstream Dilution of Tritium
Because the tritium concentrations were well
above detectable levels, it was decided that an
evaluation of the rate of dilution downstream on
Black Creek was desirable. On Trips ¥111, IX, and X
five points were sampled at 3,2r 6f 25, 32,7, and «44
kilometers downstream. These locations were at the
bridge of Highway 39 (3.2 kilometers), pier at the
end of Churchill Street in Hartsville? SC, (6
kilometers), the bridge of Highway 52 (25
kilometers), the bridge of Highway 133 (32.7
kilometers), and the bridge of Highway 35 (HH
kilometers). The last point is about one kilometer
above the confluence of Black Creek and the Pee Dee
River, The tritium concentration values are given
in table 3.
Table 3
Observed concentrations of tritium
downstream
nCi/1
Position
At
HW
the dan
39
Churchill St.
HW
HW
HW
52
133
35
Distance
{ km)
0
3.2
6
25
32,7
44
Trip
VIII
.6 ±
.6 ±
.5 ±
. .41
.5 i
.5 ±
.2
.2
.2
.2
.2
.2
3
4
2
1
1
1
Trip
IX
.7
.1
,9
,6
.8
.3
±
±
±
t
±
±
.2
.2
.2
.2
.2
.2
2.
2.
2.
1.
1,
1.
Trip
X
7 ±
7 ±
4 ±
7 ±
6 t
4 ±
,2
,2
.2
.2
.2
.2
26
-------
Since the Trip "VIII data seemed, to show no
trend due to its large fractional error, the trip
data for IX an<3 X were used to determine an exponen-
tial curve of the form;
y = jjg.uji
This yielded the constant values of:
Trip IX Trip X
a = 3.7 a = 2.7
b = -.025 b = -.016
It is significant to note that the coefficients
of determination for Trips IX and X are r = .91 and
,98, respectively. This indicates a relatively high
degree of correlation. The resultant implied model
for downstream dilution is;
{Equation 5)
C = C
L
C = concentration of nuclide downstream at «x"
kilometers below the dam
CT - average concentration of nuclide in the lake
x = kilometers downstream of dam (not to exceed 45
kilometers)
27
-------
Tritium in well Water
Tritium concentrations were also determined in
water samples from wells surrounding the lake to
monitor the significance of transport from the lake
to the underlying aquifers. The results of this
study summarized in table H are basically incon-
clusive. Even though an enrichment procedure was
used to increase the sensitivity of the analytical
procedure on a selected group of these samples there
seemed to be no significant correlation between the
average of the well water samples and the average
lake concentration; hence no quantitative estimate
could be made of any transport coefficient from the
lake to'the aquifers. Neither could one say conclu-
sively that such transfer does not occur,
(gamma' Emitting Radionuclides
Prom the liquid waste releases of the reactor there
are several radionuclides which are gamma emitters, a
characteristic which simplifies their detection and
analysis. Many of these radionuclides are isotopes of
elements useful to biological systems and are therefore
reconcentrated within the biological components of the
lake system. Others have chemical forms which react with
components of the environment so as to effect recon-
centration or dissolution through ion exchange, molecular
complexing, and other physical interactions. Many radio-
isotopes are subject to both physical and biological
forces. In order to assess the significance of these
forces the lake water concentration must be determined or
inferred. It is important in this study that not only
the concentration observed- during a field trip be
accurate but some estimate of concentrations with time
between trips be available.
cobalt
Radioisotopes of cobalt are of particular in-
terest. These are produced by neutron activation
within the hardware of the reactor core. During
Trip I the concentration of cofoalt-58 was readily
measurable in the lake water. On subsequent trips
cobalt-60 concentrations were measurable using the
large volume sample data. Figure 10 shows observed
concentrations of cobalt-58 as compared to concen-
trations predicted by equation 2 and using release
28
-------
Table 4
Tritium concentrations in wells
nCi/1
Well
23-A
39-A
39-B
595-A
7 3 7- A
737-B
674
Trailer
House on
E. Shore
Avg.
SD
Lake Avg.
Trip IV
03/14/72
.15*
.4
,24
.10
,10
.41
- <.2
.3
.3
.24
.12
1.69
Trip ¥11
02/06/73
.13*
.3
.2
.01
,13
.4
.04 •'
NS
NS
.17
.14
' 1.15
Trip VIII Trip IX
06/05/73 11/05/73
<,2 < .2
,2 .3
.2 .4
<.2 < .2
«,2 < .2
.2 .3
<.2 ,2
.4 .4
NS NS
<.2 . .24
_
.61 3.7
•Trip X
05/14/74
.10*
.3
.2
.10
.2
.2
.10
NS
NS
.17
.08
2.65
NS - Mo sample. - - .
* Data reported to the nearest hundredth was determined by a
tritium enrichment procedure.
29
-------
data as available from reactor operating records.
The triangles enclosed in a square indicate that the
value was less than detectable and is plotted at
.025 pci/liter or one-fourth • the normal minimum
detectable limits, in order to evaluate the com-
parison of observed versus expected values a paired
"t" test was run to determine if the means of the
two sample populations were significantly different,
This is represented in table 5. &s shown in the
table the means were not statistically different.
Thus the model is a reasonable estimate of the ob-
served lake concentration of cobalt even though its
correlation to observed data is not as close as for
tritium.
c_
0)
- t
u
a
O
1971
1972 1973
date
1974
Figure 10.
Observed and predicted concentrations of
cobalt-58 in Lake Robinson
30
-------
Table 5
Statistical comparison of observed and predicted concentrations of
cobalt-58 ia Lake Robinson water
pCi/1
Trip
I
II
III
IV
V
VI
VII
VIII
IX
X
Ho: observed -
Date
12/01/70
03/09/71
09/21/71
03/14/72
07/10/72
10/31/72
02/06/73
06/05/73
11/05/73
05/14/74
estimated = 0
t.025 = +- 2'262
Confidence Level = 1-a = 95%
-2.262 < .095 < 2.262
Observed
1.78
1.10
ND
.12
1.07
.96
.02
.14
ND
ND
D =
SD =
df =
Predicted
1.0
.56
.66
.36
.79
.10
.11
.56
.1
.85
.0175
.5818
.095
9
Ho: accepted
ND = Not•detected.
31
-------
From toth the model and the observed data we
see that measurable concentrations were likely in
two periods; November 1970 to July 1971 and June
1972 to November 1972. h third rise was predicted
'by the model from May 197a to July 197£|r but this
was not verified by the observations.
A similar comparison was made using observed
_and predicted values of cobalt-60, This is
presented in table 6. In this case the poor fit be-
comes more evident as the difference between the ob-
served and predicted is shown to be statistically
significant. Furthermoref the test indicates that
the mean of the estimated values is greater than
that of the observed values. This would support use
of the model as an upper limit estimator of lake
concentration trends.
Cesium
toother element having radioisotopes which oc-
curred in detectable concentrations in the water was
cesium. Cesium-137 and cesium-134 are generated in
the fission process as opposed to the activation
production of most of the other gamma emitting ra-
dionuclides. Thus, the appearance of these isotopes
occurs as a result of leaking fuel elements and
subsequent containment leakages unrelated to the
activation product releases in the liquid wastes.
Cesium-137 is a primary radionuelide in world-
wide fallout and is present in small quantities in
the general environment. The mean value for the
concentration of cesium-137 in the water prior to
any reactor influence is estimated as .11 pCi/liter,
This value was determined, based on the average of
all background water analyses performed from all the
trips. Table 7 summarizes the cesium data for both
cesium-137 and cesium-13W, The predicted value for
cesium-137 is calculated by adding the background
value to the value calculated by equation 2. The
standard deviation is not calculated when the number
of values averaged is less than four. The good
agreement between observed and predicted values is
due mainly to the small contribution from reactor
releases as compared to background values, Rs re-
leases became more significant, the divergence
between observed and predicted concentrations
occurs. Table 7 summarizes and compares observed
arid predicted values for cesium.
32
-------
Table 6
Statistical comparison of observed and predicted
concentrations of cobalt-60 in Lake Robinson water
pci/l
Trip Date Observed Predicted
I
II
III
IV
V
VI
¥11
VIII
IX
I
12/01/70
• 03/09/71
09/21/71
03/14/72
07/10/72
10/31/72
02/06/73
06/05/73
11/05/73
05/14/74
Ho : observed - estimated = 0
t.025 = *
Confidence
-3.80 <
2.262
level - 1-cc =95%
-2.262
.1
.2
ND
.1
.1
.09
.05
.06
ND
ND
D = -.68
SD = .57
t = -3.80
df = 9
.025
.25
.74
1.4
1.3
.8
.22
.55
.56
1.65
Ho; rejected
ND - Not detected.
33
-------
Table 7
Observed and predicted concentrations
of radioisotopes of cesium in Lake Robinson
pCi/1
Trip
Date
I
12/01/70
II
03/09/71
III
09/21/71
IV
03/14/72
\
v
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
X
05/14/74
Background
eesium-137
Observed Predicted
(Standard Deviation)
.2
(*)
.2
(*)
.22
(.11)
.13
(.03)
.18
(.06)
.16
(.03)
,15
(.06)
.24
(.04)
.19
(.04)
3.2
(.5)
,11
(.05)
.11
.11
,11
.11
.16
.16
.15
.75
.45
1.45
Cesium-134
Observed Predicted
(Standard Deviation)
ND
ND
ND
ND
ND
.02
(.05)
ND
.14
(.04)
.03
(.04)
2.4
(.7)
ND
ND
ND
ND
ND
.04
.04
.06
.24
.09
1.2
*Insufficient number of data points to estimate standard
deviations, (< 4)
ND - Not detected.
34
-------
Chromium
Chromium-51, an activation product:, was ob-
served in water at concentrations from 1 to 2
pCi/liter during three of the sampling periods. The
summary of this data is shown in table 8. Predicted
values using equation 2 never exceeded .16
pCi/liter.
Manganese
The detection of the activation product,
manganese-54, was inconclusive because of
complications in interpreting the interference of
manganese-54 with a .83 Me¥ gamma with the .81 MeV
gamma energy of cobalt-58. In most cases positive
analysis of these two could only be accomplished
following chemical separation prior to gamma spec-
tral analysis or utilization of a Ge(Li) counting
system. This factor reduced the sensitivity of the
detection and, consequently increased the minimum
detectable concentration to apparently .2 pCi/liter.
It is interesting that the predictive model shows
the concentration of manganese-54 to range consist-
ently between .1 and 1,0 pCi/liter. The concentra-
tions of manganese are summarized in table 8.
Iodine
Iodine-131, another fission product, was de-
tected in the final survey at an average concen-
tration of 4.5 pCi/liter. Prediction of iodine-131
concentrations were not attempted due to the short
half-life of 8.1 days. This would cause the lake
concentration to be highly responsive to tlie
specific time of release and the quantity released.
Averaging the total monthly release would introduce
an unreasonable error as compared to observed lake
concentrations. The May 14, 1974, samples averaged
4.5 pCi/liter with a standard deviation of 1.9
pCi/liter,
-------
Table 8
Average chromium-51, manganese-54
and iodine-131 concentrations
observed in Lake Robinson water
pCi/1
Trip
Date- 5 a Cr
I 2.2
12/01/70
II <.3
03/09/71
III <.3
09/21/71
IV 1.28
03/14/72
V 1.60
07/10/72
VI <.3
10/31/72
VII <.3
02/06/73
VIII <.3
06/05/73
IX <.3
11/05/73
X <.3
05/14/74
»Mn
<.05
<.05
<.05
<,05
.15
.03
<.05
.10
<.05
<.05
1 51 j
<,05
<.05
<,05
<.05
<.05
<.05
<.05
<.05
<.05
4.5
36
-------
Observations and summary
The non-tritium data demonstrates an increasing
divergence from the predictive model of equation 2. This
is likely due to the origin and nature of this waste as
compared to tritium. The tritium is not concentrated in
the waste evaporators, and each release of liquid waste
will contain a quantity of tritium consistent with the
tritium inventory which has leaked from the primary cool-
ant loop. Hence, the mathematical treatment of tritium
as a continuous rate release is usually quite valid. The
non-tritium radionuelides originate from many varied
points within the reactor core. This is particularly
true of activation products. The physical and. chemical
forms of these products regulate the effectiveness of the
waste evaporator in removing these contaminants from the
system. Iks a result, effective modeling of these con-
taminants should treat their releases as discreet events
as opposed to a continuous steady rate occurrence. The
same may be said for fission products which enter various
liquid wastes The reactor operators who have a record of
liquid release data could easily maintain a running esti-
mate of radionuclide concentrations in the lake,
Additional Ra dionuc11de Me a surements
Strontium-90
Strontium-90 is a fission product which has
been released to the earth's biosphere from past
nuclear weapons tests and is found in many environ-
mental samples. Due to the radiotoxicity of
strontium-90 and its presence in reactor wastes,
water samples were analyzed for this radionuclide.
Jk specific chemical separation for strontium was
performed on 1-liter aliquots of lake water drawn
from the 19-liter sample sets. For survey Trips I-
IX no strontium-90 or strontium-89 was detected. Of
the eight water samples analyzed, for survey Trip X,
four indicated less than the detectable limits of
.25 pCi/liter. The other four indicated an average
of «27 pCi/liter of strontium-90 and a standard
deviation of .017 pCi/liter. Since the% minimum
detectable limit was determined to be .25 pCi/liter,
it was concluded that the lake concentration was
likely less than the .25 pCi/liter detection limit
for strontium-90. Ho strontium-89 was detected in
any lake water samples.
3?
-------
Gross Alpha and Beta Counting
Environmental radioactivity monitoring programs
have historically reported gross alpha and beta
counts to serve as a trend indicator of radio-
activity in environmental samples. In order to pro-
vide comparison data in this format, table 9 sum-
marizes results of the current Lake Robinson survey.
The gross beta data were tested for correlation
with the total of the non-tritium activity in the
water. This comparison is summarized in table 10.
A linear regression fit was determined- using -the
dissolved solids gross beta average as the inde-
pendent variable (x) and the sum of the non-tritium
average activity data as the dependent variable (y).
The resultant equation was:
y = -1.43 + 1.8x
Miere:
y = Total non-tritium con-
centration (pci/liter)
x = Observed gross beta in dis-
solved solids (pci/liter)
The coefficient of determination (.59) demon-
strates that. the gross beta data were of limited
value for estimating concentrations of non-tritium
activity in the water.
38
-------
Table 9
Gross alpha and beta activity concentrations
in Lake Robinson water
pCi/1
Trip
Date
I
12/01/70
II
03/09/71
III
09/21/71
IV
03/14/72
V
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
X
Undissolved i
< 1 -
< 1 '
< 1
< 1
' 1.3 ± 1.9
< 1
< 1
< 1
< 1
1.5 ± 1.1
Solxds
Alpha
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
Dil
Beta
2.4 ±
3.4 ±
2.7 ±
1.1 ±-
1.75 ±
1.3 ±
1.44 ±
.9 ±
.89 ±
4.9 ±
3 solved
1.8*
.64
.39
.70
.53
.62
.69
1.1
.98
1.8
Solids
Alpha
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
05/14/74
* Observed standard deviation.
39
-------
Table 10
Correlation of gross beta determinations with
total specific analyses
pCi/1
Trip •
I
II
III
IV
V
VI
VII
VIII
IX
X
Equation Form:
Date
12/01/70
03/09/71
09/21/71
03/14/72
07/10/72
10/31/72
02/06/73
06/05/73
11/05/73
05/14/74
y = a0 +
Total
specific
activity
y
4.3
1.5
.2
1.6
.3.1
1.3
.2
.7
.2
10.1
1
Gross beta
(dissolved
solids)
X
2.4
3.4
2.7
1.1
1.75
1.3
1.44
.9
.89
4.9
a0 = -1.43
= +1. 8
Coefficient of determination = .59
40
-------
Physical Measurements in Water
In order to characterize the lake water, numerous
physical measurements and analyses were performed. The
primary intent was to scan these physical parameters for
any indications of unusual changes which would indicate
significant shifts in the dynamic forces which distribu-
ted the radionuclides throughout the lake system. Table
11 summarizes the pH and solids found in the water.
Table 12 summarizes the dissolved stable element concen-
trations.
The data in table 11 seem to indicate relatively
consistent values of dissolved and undissolved solids.
No unusual variations are apparent. The pH was observed
to vary from a low of 4.7 to a high of 6.1. The data did
suggest a seasonal dependency with low pH occurring in
the months of February and March and higher pH occurring
in July and August, The seasonal variation, approximated
with a sine function, showed no difference in predicted
versus observed values for nine trips using a paired "t"
test and a confidence level of 90 percent. Such modeling
serves only to demonstrate the cyclic nature of the pH
within a year.
Table 12 demonstrates relatively constant and
consistent stable element concentrations. Iron varied
sufficiently to bear some comment. Comparison of the
iron data to several parameters indicates that the most
significant correlation was with the lake discharge
rates.
The relationship is expressed as;
concentration of Iron * (Lake Discharge) -3
This may indicate that the iron was introduced at a
constant rate and was diluted fcy the rainfall. The other
elements were more likely brought into the drainage
system of the watershed with similar elemental makeup
such that rainfall or flow rates did not affect the
concentration.
41
-------
Table 11
Average pH and solids content
of Lake Robinson water
Trip
Date
I
12/01/70
II
03/09/71
III
09/21/71
IV
03/14/72
V
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
X
05/14/74
PH
5.
4.
5,
5.
6.
5.
4.
5.
5.
5.
2
7
6
8
1
7
9
5
8
2
Undissolved
Solids
mg/1
17
9
7
6
3
10
9
6
9
5
.3
.7
,9
.6
.7
.2
.8
.9
.1
.8
Dissolved
Solids
mg/1
22
18
29
13
7
19
17
19
29
22
,2
.3
.5
.3
.9
.8
.2
.0
,2
.5
Average
5.5
8.7
19.9
42
-------
Table 12
Average stable element concentration
in Lake Robinson water
mg/1
Standard
Element
Sodium
Magnesium
Potassium
Calcium
Manganese
Iron
Cobalt
Zinc
Strontium
Cadmium
Cesium
Concentration
1.54
.42
.46
.80
.0056
.56
.008
.020
<.005
.004
<1.0
Deviation
.15
.068
.077
.17
.0064
.22
.006
.009
.003
MDL
2
3
5
2
5
1
3
5
5
2
1
X
X
X
X
X
X
X
X
X
X
10" 3
10-"
io-»
10~a
<** 8
io-a
1Q-3
10- 3
10- a
10" 3
MDL ~ Minimum detectable level.
43
-------
SECTION ¥
AQUATIC VEGETATION
In observing a lake ecosystem, one important com-
ponent is vegetation. It is within this component -that
mineral content of the water and lake bottom interact
with sunlight to form the first trophic level of the sys-
tem, The lake vegetation se.rves a wide variety of func-
tions such as food sources 'for aquatic life, habitats for
aquatic fauna, benthic stabilizers frow the scouring
forces of currents, and a source of dissolved oxygen,
Inherent in the nature of plant life is its ability
to selectively take minerals from the environment and
include them within its organic structure. Such action
causes the lake flora to concentrate many of the radio-
active elements discharged into the lake as wastes. Such
storage action is only temporary since the radionuclides
following the patterns of cycling elements transfer from
one component to another until they have decayed to a
stable elemental form and become a respectable member of
the natural nutrient pool .
The vegetation found in lake Bobinson is typical of
dark water lakes of that region. Table 13 lists the
major aquatic weeds that were observed indigenous to the
lake. Of the many species found there Mygyphae odorata
(white water lily) » gap as flexilis (naiad) , and
(water milfoil) were most often chosen for
field sampling, sampling instructions were to find about
1 kilogram of vegetation in the vicinity of a 200-liter
water sampling site. The* preferred vegetation type was a
submersed weed. The second preference was given to
emersed weeds which had only floating leaves above the
water surface, Emergent weeds were taken only as a last
resort.
The agtiatic vegetation appeared to be a sensitive
monitor of the presence of some radioactive wastes.
Table 1t compares the confirmation of radioactive waste
nuclides in the water and vegetation of the lake. These
data suggests that vegetation might be particularly
effective for detecting cobalt, manganese, and iodine,
Chromium and cesium seemed to be more readily detected by
water sampling,
44
-------
Table 13
Genus
Aquatic weeds observed
in Lake Robinson
Common Name
Character
Nymphae
Najas
Myriophyllum
Graminea (family)
Brasenia
Vallisneria
Juneus
Eleocharis
Typha
Potomogeton
Pontederia
White Waterlily
Naiad
Watermilfoil
Grass
Watershield
Valisneria
Creeping Rush
Spike Rush
Cattail
Pondweed
Pickeral Weed
emersed
submersed
submersed
emersed
emersed
submersed
submersed
emersed
eutersed
emersed and
submersed
emersed
45
-------
Table 14
Environmental confirmation of radionuclides
released in liquid wastes*
Times
Observed in
Radionuclide Liquid Waste
seCo 10
60Co ' 10
5 "*Mn 8
stCr 5
I311 6
1 3 7Cs ** 6 **
13 £i
v ~ iTi « jr
Tiroes
Observed
in Water
7
7
4
4
1
5 **
4
Times
Observed
in Vegetation
10
10
7
1
3
2 **
1
* Confirmation over 10 trips,
** Occurs - in-detectable quantities in the environment independent
of reactor releases, ,
Tables 15, 16»• 17, and 18 show the average radio-
nuclide contents of aquatic vegetation. The data demon-
strate that radionuclide content increases and decreases
with releases • of 'radionuclides. (See figure A~3»
Appendix I.) The rates of decrease appear to exceed the
decay rates of the longer-lived radionuclides. Such
behavior implies the presence of a removal action from
•the vegetation ether than that of radioactive decay.
Apparently the radionuclide content of vegetation is more
a function 'of the recent history of liquid releases
(releases in the last 1 to 6 months) than it is of prior
releases, . . The vegetation•does appear to be an effective
integrator of- some radionuclide releases and, as such, an
effective biological monitor of certain radionuclides in
water.
46
-------
Table 15
Radioactive cobalt in Lake Robinson
aquatic vegetation
pCi/kg
Trip
Date
I
12/01/70
II
03/09/71
III
09/21/71
IV
03/14/72
v
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
X
05/14/74
Dry Wt
5,000
44,000
2,500
5,200
74,000
6,200
1,900
4,500
470
260
Cobalt-58
Wet Wt.
570
3,200
250
770
14,000
900
350
380
30
40
Dry Wt
290
9,200
1,400
1,200
12,000
3,100
1,400
4,900
2,100
1,500
Cobalt- 60
Wet Wt.
40
640
100
200
2,100
400
250
420
150
220
47
-------
Table 16
Radioactive cesium in Lake Robinson
aquatic vegetation
pCi/kg
Trip
Date
I
12/01/70
II
03/09/71
III
09/21/71
IV
03/14/72
V
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
X
05/14/74
Cesium-137
Dry Wt. • Wet Wt.
2,160
3,500
1,000
580
3,200
1,400
, 510
1,200
9,400
7,800
240
240
90
50
550
100
100
110
800
1,100
Cesium-134
Dry Wt. Wet Wt.
< 50
< 40
< 50
< 50
< 50
<100
< 60
< 20
6,700
3,500
< 10
< 3
< 3
< 5
< 6
< 5
< 13
< 5
570
760
48
-------
Table 17
Radioactive iodine and strontium
in Lake Robinson aquatic vegetation
pCi/kg
Trip
Date
I
12/01/70
II
03/09/71
III
09/21/71
IV
03/14/72
V
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
X
05/14/74
Strontium- 8 9
Dry Wt, Wet Wt.
< 50
<400
<100
<100
<100
<200
100
<100
160
280
< 5
< 30
< 5
< 10
< 10
< 20
< 10
< 10
20
40
Strontium-90
Dry Wt. Wet Wt,
< 10
620
850
210
870
1,700
780
1,000
3,700
280
< 1
40
50
30
150
130
140
90
70
40
Iodine-131
Dry Wt. Wet Wt.
< 50
1,000
< 50
< 50
< 50
<100
< 50
< 50
3,400
4,200
< 10
70
< 5
< 5
< 5
< 6
< 20
< 5
280
590
49
-------
Table 18
Radioactive chromium and manganese
in Lake Robinson aquatic vegetation
pCi/kg
Trip
Date '
I
12/01/70
11 • -
03/09/71
III
09/21/71
IV
03/14/72
V
07/10/72
VI
10/31/72
VII
02/06/73
VIII
06/05/73
IX
11/05/73
X
05/14/74
Chromium- 51
Dry Wt. Wet Wt.
< 500
< 500
2,000
< 500
4,100
<1,000
<2,OQO
1,200
< 500
< 500
< 50
< 50
130
< 50
710
< 60
<200
100
< 50
< 50
Manganese-54
Dry Wt. Wet Wt.
< 50
2rOOO
< 50
< 50
2,100
410
490
2,100
910
520
< 10
140
< 5
5
360
130
90
180
60
70
50
-------
SECTIOW ¥1
BENTHIC S1DIMENTS
The lake benthos comprises a component of the lake
system which could receive and store significant quanti-
ties of radioactive material through sedimentation and
through direct chemical transfer from the water such as
chemical reaction, ion exchange, and other adhesion
actions, sedimentation is considered to be the primary
action contributing to the accumulation that takes place.
It consists of suspended solids which have grown through
agglomeration to a density sufficient to cause settling,
Agglomeration is a scavenging process by which ions, some
molecules, and smaller particles are attracted by elec-
trostatic , magnetic, and gravitational forces. Such ac-
tions are not unique to radio!sotopes, but do effect an
accumulation of them and thereby remove some radioactive
material from the liquid medium. In addition„ dead or-
ganic material, detritus, falls to the bottom carrying
with it the radioactive material it accumulated in its
growth and other active biological processes.
As there is transport into this compartment, there
is also removal or disappearance from it. The ever
changing parameters of the water such as pH and ionic and
elemental concentrations cause varying dissolution inter-
actions between the lake water and the material at the
lake floor (10), As radioactive decay takes place the
quantity of radioactive material within the compartment
further reduces.
This study did not attempt to quantify the inflow
and outflow rates of the compartment, but it did attempt
to capture pictures of the existing radioactive - content
of the lake benthos and thereby to infer something of the
nature and significance of the lake benthos as a storage
compartment. Table 19 summarizes the radionuclide analy-
for the dredge sampling locations (figure 11). This
table presents only those radionuclides which are obvi-
ously originating in the reactor. The only exception is
cesium-137 which is present in the general environment .as
well as produced as a fission product within the reactor.
The results of the surveys as given in table 19 indicate
that measurable concentrations of these radionuclides not
only rise but fall. Figures 12 through 17 show a se-
quence of data on cobalt that suggests this action.
51
-------
Kilometers
Upstream
of Dam
Position A
.2
Table IS
Radioactivity in Lake Robinson sediments
pCi/kg (dry weight)
Position B Position C Position D
Position E Position F
2.4
5,7
7.5
9.1
9.8
Trip I
12/01/70
7Cs: 543 1>7Cs: 352 1!7Cs; <20 1>7Cs:' 193 l"Cs: 78 No Sample
Trip II
03/09/71
'Css 939 I3'Cs: 528 l"Cs; 822 137Cs: 4222 137Cs: 714 13'cs: 1578
Trip III
09/21/71
'"CS! 266 I37Cs: 442 '3'Cs: 2657 1J7Cs: 1430 vs?Cs: 3S5 ls'Csi 620
Trip IV
03/14/72
"Co:
88 15'Cs: 311 1}'Ca: 168 l"Cs: 144 1J7Cs: 1159- l"Cs: 1538
68 !J1I: 202
Trip V
07/10/72
Trip VI
10/31/72
Trip VII
02/06/73
Trip VIII
06/05/73
7Cs:
'Css
"Co:
"Cs:
iBCo:
"CO!
292 "7Cs: 1584 l"cs: 139 ' "Cs: 730 ls?Cs: 1697 >3'cs: 770
'"Cos 120
5BCo: 1140
5*Mn: 110
332 "JCS! 794 157Cs: 2380 '37Css 1970 ii7Cs: 1016 '"Css 1879
124 "Co: 110 "Co: 568 "Cos 340 68Co: 56 60Co: 104
58Co; 550 s"Cos 900
4682 137Cs: 1071 137Cs: 1246 I>7Cs: 889 '"ess 3002 JS7Cs: 583
332 '"Co; 1165
102 S8CO! 755
3457 ls'Css 1034 'l37Cs: 3626 117Cs: 1183 137Cs: 1388 ls?Css 2544
**Cos 213 68Co: 550
Trip IX
11/05/73
Trip X
05/14/74
'CB:
'Cs:
"Co:
2246 137CS! 1051 l"Css 401 l37Cs: 1735 »"C»» 2686 "7Csi 1048
"Cos 241 e°Co: 1140
S«CO! 190
1438 137Cs: 1051 '"Css 601 137Cs: 403 "'Css 2246 ll7Cs: 192
75 60Co: 200 68CO! 243 £8Co: 238' "Co: 107
52
-------
Based on these results it is believed that buildup of ra-
dioactive materials in the benthos sediments of the lake
is reduced by an additional removal action other than
radioactive decay.
scale
1 km.
D
visitors center
legend
&s Dredge sampling locations (a-f)
in Lake Robinson
Figure 11. Dredge sampling locations in Lake Robinson
. 53
-------
100CH
U t 500-
°- Q
legend
0-58Co
1971
1972
year
1973
1974
Figure 12. Radioactive cobalt in sediment (position a)
1000'
o»
£? 500-
o
legend
0--58Co
1971
1972 year -1973
1974
Figure 13. Radioactive cobalt in sediment (position b)
1000'
_JL
i >A»
f\
1971
1972
O
year
1973
legend
o . o
1974
Figure 14. Radioactive cobalt in sediment (position c)
54
-------
legend
0-~58Co
1OOCH
500'
1971
19*72
year
1973
1974
Figure 15. Radioactive cobalt in sediment (position d)
100CH
en
u •
a Q 5QO
egena
0-58Co
-A
_Q
1971
year
1974
Figure 16. Radioactive cobalt in sediment (position e)
1000
50O-
legend
A 60_
A— Co
0-58Co
1971
1972 1973
year
1974
Figure 17. Radioactive cobalt in sediment (position f)
55
-------
SECTION VII
FISH •
In spite of the dark water nature of Lake Robinson,
the productivity in the lake appeared to be relatively
low. Nutrient levels as recorded in STORET (11) and
other qualitative observations seemed to predict this.
Conversations with the area game warden suggested that
sport catches from the lake were relatively low. There
was considerable difficulty in obtaining fish samples
from the lake with any consistency. The method of col-
lection was by electrical shocking. The conductivity of
the lake water was sufficiently high to restrict the ef-
fectiveness "of this procedure. As a result of these
problems, the available data were limited. Table 20
shows the cesium-137, cobalt-58, cobalt-60, chromium-Si,
and manganese-5*J observed in the samples.
The samples were prepared by grouping the fish ac-
cording to species. The fish were then dissected into
meat,; bone, viscera. In the case of larger speci-
mens J hearts and livers were separated from the other
entrails for analyses. Cobalt-58 was identified in
specimens of catfish, bream, suckers, largemouth bass,
crappie, and drum in the second survey trip. The appar-
ent absence of this radionuclide in Trip I may indicate
that accumulation of cobalt in the fish of the lake is at
a relatively slow rate; thus, fish are a slow integrating
storage component for this radionuclide in this lake.
-------
Table 20
Radioactivity in lake Bobinson fish,
pCi/kg Wry weight)
Shiners
»"Ca
Catfish
a'
Co
Carp
Trip I Trip II Trip III trip IV Trip V Trip VI Trip VII Trip VIII Trip IX Trip X
2430
T"C« 442
Breara
l*'Cs 431
»»CO
Pike
1>TC» 965
Suckers
>"C« 503
5*Co '
"CO
Sicr
Large Bass
»»*C» 776
*«CO
"CCS
Baby Bats
C* 51«
Crappie
^Cs
"Co
Dram
***C»
**CO
453
127
610
419
64
211 •
897
103
722
5»
301
103
320
186
620
(5)
m
436
278
274
382
435
152
S
m
309
1S3
Shad
Jack
"'C» 411 361
f - Trace detected but !«•• than quantitative Mneitivity,
263
188
57
-------
S1CTIQN VIII
AND CONCLUSION
'BjsjmyjLoi: of Lake Components
In the review of data collected from the system
tinder study, it is clear that measurable quantities of
radioactivity accumulate in the lake and its various com-
partments. Frequently the concentrations are so small
that exceptional techniques are required to determine the
concentration of radioactivity. This is especially true
in the measurement of radioactivity in water. It is im-
portant to note that although many samples yielded no de-
tectable content of radioactive waste from the reactor,
there did occur some occasions when measurable quantities
of such radioactivity were present in each of the lake
system compartments; lake water, aquatic vegetation,
fish, and benthic sediments. It wasf therefore* evident
that accumulation did take place.
The lake volume, the rate of cooling water flow from
the lake through the reactor and return, and the lake
discharge rates all cause the lake water to perform ac-
cording to a simple mathematical equation. Several
unique features of the lake probably aided in effecting
the predictable behavior. The low pH of the dark water
lake tends to increase the solubility of many waste ele-
ments and compounds. The apparent low productivity of
the lake limits the storage capacity of the fauna and
flora components. The sandy nature of much of the ben-
thic soils limits its ion exchange capacity, thereby
reducing the capacity of the benthos to store radioactive
wastes. As a result, the mathematical model should pro-
vide good predictive values of concentrations. The
deviation of the model values from observed concentration
values may be attributed to the errors in the liquid
waste release data and lake flow data. Therefore, it is
believed that the equation 2 is a good model for this
system.
it
fl-e
58
-------
Further downstream dilution can be simulated by;
c = CT e-
Due to the variability of lake flows and liquid waste re-
lease rates, it is difficult to define a maximum concen-
tration value expected for any radionuclide. Table 21
summarizes expected ranges of concentration in water,
using the release parameters presented in the
Environmental Impact Statement (9), The upper range
limit is calculated on a lake flow of 2.8 m3/sec a typi-
cal "dry" month flow; the average on a flow of H.l m3/sec
an average flow; and the lower value for flows of
11.3 in3/sec typical of a "wet" month flow. This table is
not designed to express maximum concentrations which
might occur but is to demonstrate a set of typical values
which might reasonably be expected.
Table 22 expresses the dose to a swimmer swimming 50
hours in the water at the concentrations of table 21.
Fifty hours was chosen as a realistic and convenient sea-
sonal exposure for an individual. The dose expressed in
table 22 also represents that of 100 hours of fishing,
boating, and/or water skiing on the lake since these
activities represent a 2 ir geometrical exposure as com-
pared to a 4 w exposure from swimming.
The concentrating effects of vegetation appeared to
be quite significant for many of the radionuclides occur-
ring in the liquid wastes. On several survey trips the
radionuclides were easily detectable in vegetation but
not detectable in the water directly.
The apparent concentration factors of the vegetation
demonstrated a high degree of variability which was dif-
ficult to interpret. The obvious behavior demonstrated
by the vegetation was an apparent transfer of radioactiv-
ity back to the water as the water concentration of ab-
sorbed radionuclides decreases, such action modifies the
extent of a long-term buildup over the years,
Fish data, like vegetation, indicate a responsive
rise and fall of radionuclide concentrations with those
of water. Again such behavior suppresses a gradual long-
term rise in radionuclide concentrations independent of
lake water concentrations.
S§
-------
Table 21
Projected range of equilibrium concentrations
at various lake flows
pci/1
2.8 m3/sec
4.8 m3/sec
11.3 m3/sec
Highest Lake
Average
Nuclide
3e
sicr
"Mn
58Co
60Co "
89Sr
90Sr
I 3 1 j
13 kCS .
137Cs
(dry month)
1.1 x 103
.10
.12
1.9
.47
.05
.005
7.38
9.89
10.1
(avg. month)
.55 x 103
.08
.07
1.36
.24
.04
.0024
6.91
5.62
5.06
{wet month)
.25 x 10s
.06
.04
,87
.12
.03
.0012
6.12
2.73
2.54
Observed .. .
3.7 x 103
2.2
.15
1.8
.2
.27*
< 5*
4.5
2.4
3.2
*This concentration is found in the general environment and cannot
be wholly attributed to releases from this facility.
60
-------
Table 22
Projected range of doses to an adult
*
swimming 50 hours in expected concentrations
(mrem to whole body)
Highest Lake
Concentrations
Nuclide
Dry Month
Avg. Month
3H -0-
5lCr
slfMn
58Co
60Co
"Sr
90Sr
1 3 1 T
13*CS
137Cs
2.
9.
1.
1.
1.
1.
2.
1.
5.
6 x
0 x
7 x
,1 x
2 x
4 x
5 x
4 x
1 x
1Q-7
1Q~6
10-4
„ . am, tl
io-8
io-l°
lo-"
1Q_3
10-*
2.
5,
1.
5.
9.
6.
2.
8.
2.
-0-
1 x 1Q~7
3 x 10~6
2 x 10~*t
5 x 1G~S
2 x ID"9
5 X ID"11
3 x 10-1*
1 x 10"""*
5 x 10~%
Wet Month
1
3
7
2
6
3
2
4
1
.6
.0
.8
.8
.9
.2
.1
.0
.3
-0-
x ID"7
x IO"6
x 10~5
x 10~5
x 1Q-9
x IO-11
x 10"1*
x 10-*
_ _ „_ u.
x 10
Observed
-0-
5.
1.
1.
4.
6.
1.
1.
3.
1.
7
1
6
6
2
4
5
5
6
x IO""6
x 10~s
x 10"**
x ID'5
x 10~8
x IO""7
x 10""**
x ID"1*
x io-*
Total 2.4 x 10"3
1.5 x 10
-3
8.5 x 10"
'.8 x 10*
* The dose expressed also represents that of 100 hours of fishing,
boating or water skiing.
61
-------
Benthic sediments demonstrate an ability to release
their stored radionuclid.es. Such action again reduces
any extended storage in this component of the system.
This particular lake system stores the bulk of the
liquid radioactive waste in the same manner that it would
any solute. As such, it tends to make maximum use of
downstream .transport and dilution. If one assumes that
dispersion and dilution are desirable qualities of such a
system, this particular system offers many advantages.
1. The low pH probably increases the
solubility of many of these waste
products and thereby insures a longer
retention in the soluble state.
2. The low productivity of the lake
limits the fish available for sports-
men and human intake.
3. The water is not of a quality
desirable- for potable uses. Since it
is not used in this manner another
potential pathway of human exposure
is avoided.
ft. The region does not generally require
this water for agricultural irriga-
tion and thus avoids another radionu-
clide pathway to man,
Suryei1Iance Techniques
From experiences in the conduct of this study sever-
al surveillance techniques were found effective in eval-
uating the aquatic environment. It was demonstrated that
in-plant source monitoring was of great value in guiding
the analytical techniques to achieve a maximum sensitiv-
ity for the radlonuclides released. It was invaluable to
know the relative probability of the presence of volatile
nuclides like iodine in advance of sample preparation to
preclude any loss of activity by the sample preparation
procedures. The procedure of proportional compositing
liquid wastes as an independent monitor of waste release
rates was of similar value. Such procedures validated
the operatorfs waste release data.
62
-------
In the analysis of lake water the advantage of ion
exchange columns to improve sensitivity was demonstrated.
This technique was reported by Hasuike and Windham (12).
This technique increased analytical sensitivity by a
factor of eight or more compared to usual techniques.
Such increased sensitivity provided crucial positive mea-
surements which otherwise would have been missed using
former techniques.
The analysis of vegetation tended to indicate that
qualitative monitoring of a body of water might be accom-
plished from this data. It was observed that aquatic
vegetation should be surveyed, mapped, and identified
prior to establishing the sampling protocol. In the ac-
complishment of this, divers should be used to acquaint
surveyors with the location, prevalence, and identity of
submerged vegetation. The latter is probably the most
desirable sample source and is often ignored otherwise.
Representative sampling of the aquatic fauna proved.
to be the most difficult task to achieve. Due to the
mobility of the fish, the wide variety of species and
habitat preferences, and apparent paucity of population,
this task was not accomplished to the degree desired.
The conductivity of the water in this lake limited the
effectiveness of electrical shocking. Rotenone poisoning
appeared too drastic a procedure. Netting or other trap-
ping techniques would have provided an insufficient sam-
ple size and a highly biased species distribution.
Sampling of benthic sediments offered significant
problems in portions of the lake where submerged sticks,
limbs, and debris lined the bottom. This material caught
in the jaws of the Peterson dredge and prevented its con-
tainment of a sediment sample. In many cases numerous
dredging attempts were performed to collect the sample.
Operationally, a wench system to operate the dredge was a
necessity. It is felt that use of a diver to locate an
underwater marked location and perform a stringently con-
trolled sample collection procedure might have reduced
some sample variability,
An underwater gamma probe was used to survey regions
where elevated concentrations of sediments might be
found. In this particular lake this procedure was not
sufficiently productive to warrant discussion of any
positive results. Such procedures in other studies (13)
have been extremely helpful and should be evaluated in
any similar surveillance activity.
63
-------
Conclusion
The buildup concentrations of long-lived
radionuclides observed in Lake Robinson are detailed in
the appropriate tables. The rate of radionuclide
turnover in the components other than the water was too
rapid to quantitatively determine in this study.
Since the buildup rates appeared to be highly re-
sponsive to waste discharge rates, lake flow, and ex-
change rates between the component and the system, no
"life-of-the-reaetor" effect could reasonably be
evaluated. At any given point in time concentrations of
radionuclides from the reactor as they occur in the lake
water and other lake components are primarily a function
of the history of the parameters for the previous year
and are essentially independent of any older history.
Table 22 summarizes reasonably expected annual ex-
ternal radiation doses to individuals engaging in swim-
ming, boating, or fishing, These data are calculated on
release rates presented in the EIS (9). A reasonable
estimate of dose to an individual who -swam, fished,'
and/or water skied in the lake would be about 5 microrem
per year, an imperceptable quantity when compared to
background and other potential exposures.
64
-------
REFERENCES
1. UNITED STATES NUCLEAR REGULATORY COMMISSION. Title
10, Code of Federal .Regulations, Part 50, Licensing
of Production and Utilization Facilities, Appendix
I. United States .printing Office, Washington, DC
20402 (April 1975).
2. UNITED STATES ATOMIC ENERGY COMMISSION. Title 10,
Code of Federal Regulations, Part 20, Standards for
Protection Against Radiation, par. 20.105 (a).
Division of Radiation Protection Standards. U. S.
Atomic Energy Commission, Washington, DC 205*15
(August 1969).
3. INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION.
Report of Committee II on Permissible Dose for
Internal Radiation (1959) . ICRPf Publication 2, pp.
27-34. International Commission on Radiological
Protection. Pergamon Press, Oxford (1967).
<*. CAROLINA POWER AND LIGHT COMPANY. Final Facility
Description and Safety Analysis Report, Volumes 1
and 3, USAIC Docket No. 50-261. Carolina Power and
Light company (November 1968).
5. RUTTP1R, FRANZ. Fundamentals of Limnology, pp. ISO-
IS?. University of Toronto Press. Toronto (1953).
6, U, S, DEPARTMENT OF INTERIOR. Daily Discharge
Tables of Gage- Station 02130910 at Black Creek near
Hartsville, SC, October 1966 to September 197ft.
Geological Survey, Water Resources Division, U. S.
Department of the Interior, Columbia, SC,
7. CAROLINA POWER AND LIGHT COMPANY. H. B. Robinson,
Unit No. 2g Operating Reports 1-9. Carolina Power
and Light Company (1970 - 1974),
8. U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE,
Public Health Service, National Center for
Radiological Health. Public Health Evaluation of H,
B. Robinson Unit No. 2, NF-67-2. National Center
for Radiological Health, Rockville, Maryland 20852
(January 1967).
65
-------
9. ONITED STATES NUCLEAR REGULATORY COMMISSION, Office
of Nuclear Regulation. Final Environmental
Statement related to the operation of H, B. Robinson
Nuclear Steam-Electric Plant Unit 2f NOREG-75/024
(April 1975).
10. SALQ, ANNELI, and RITVA SAXEN. On the Role of Humic
Substances in the Transport of Radionuclides, Report
SFL-A20. .Institute of Radiation Physics, Helsinki,
Finland (December 1974).
11, ENVIRONMENTAL PROTECTION AGENCY, Preliminary Report
on Lake Robinson, Darlington, and Chesterfield
Counties, South Carolina, (Draft) STORET No. 4508.
. National Eutrophication Survey, National
Environmental Research Center, Las ¥egas, NV
(November 1974) ,
12. HASUIKE, J. K. and, S. T. WIWDHAM. Construction and
Operation of an Ion Exchange Cartridge for
Monitoring Radionuclides in the Environment,
ORP/EERF 73-2. Eastern Environmental Radiation
Facility, Environmental Protection Agency,
Montgomery, AL (June 1973).
13, WINDHAM, SAM T, and C. R. • PHILLIPS. Radiological
Survey of New London Harbor, Thames River, Ccnn. and
Environs, Radiation Data and Reports, 14:659-666
(November 1973).
66
-------
Appendix I
-------
soopoo1
ft
1
en
300.000'
m
-------
1,2'
1,0
f ,6'
.2'
9/70 1/71
RF- Refueling Period
RF
1/72 1/73
month/year
1/74
Figure A-3.
Liquid radioactive waste releases
non-tritium (7)
14-
12'
10"
4)
E1
£
rt
-i 4,
9/70 1/71
1/72 . 1/73~
month /year
1/74 6/74
Figure A-4. Lake Robinson discharge rates {6}
*U.S. SOVEBBBW MtOTBB WWCi! »»-449-161/WlZ legion Ho, 4 &— 3
-------
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