ML20101S126
| ML20101S126 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee  |
| Issue date: | 05/15/1992 |
| From: | VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | |
| Shared Package | |
| ML20101S119 | List: |
| References | |
| NUDOCS 9207160380 | |
| Download: ML20101S126 (34) | |
Text
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[h ~,.b L-05/15/92 ATTACllMENT 1 VERMONT YANKEE NUCLEAR POWER CORPORATION APPLICATION TO DISPOSE IN PIACE CONTAMINATED SOIL L
, 9207160380 920710 N PDR ADOCK 05000271 p ppg l
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...t =.0-TABir Or CONTENTS 1
TOPIC PAGE NUMBER f Table of Concents. . . . . . . . . . . . . . . . . . . . . . . . . . . i 4
1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.0 Waste Stream Description . . . . . . . . . . . . . . . . . . . . . 2 2.1 Physical Properties . . . . . . . . . . . . . . . . . . . . . 2 2.2 Stapling Procedures . .. . . . . . . . . . . . . . . . . . . 3 7.3 Chemical Properties . . . . . . . . . . . . . . . . . . . . . 3 2.4 Radiolonical Properties . . . . . . . . . . , . . . . . . . . 4 2.5 Ertimate of Total Act ivity . . . . . . . . . . . . . . , . . . 6 3.0 Description of -Proposed' Disposal Method . . . . . . . . . . . . . . 13 4.0 Coology and liydrology Considerations . . . . . . . . . . . . . . . . 13 ,
5.0 Environmental Sampling Program . . . . . . . . . . . . . . . . . . 16 5.1 Water Samplin Description . . . . . . . . . . . . . . . . . . 16 5.2 Sempling P: rgram Results . . . . . . . . . . . . . . . . . . . 17 6.0 Radiological. Considerations . . . . . . . . . . . . . . . . . . . . 17 6.1 Potential Off Site Exposure Pathways . . . . . . . . . . . . . 18 6.1.1 Approect to Analysis . . . . . . . . . . . . . . . . . 19 6.1.2 Descripi.on of Scenario . . . . . . . . . . . . . . . 20 6.2 Potentini On Site Exposure Pathways . . . . . . . . . . . . . 20 6.2.1 Approach to Analysis . . . . . . . . . . . . . . . . . 21 l
7.0 Radiological Impacts . . . . . . . . . . . . . . . . . . . . . . . . 24 7.1 Potential Off Site Exposures . . . . . . . . . . . . . . . . . 24 7 1.1 Drinking Water Ingestion . . . . . . . .. ... . . . . 25 7.1.2 Fish Ingestion Pathway . . . . . . . . ., . . . . . 25 7.1.3 Irrigation Exposure Pathway . . . . . . . . . . . . . 25
'7.1.4 Shoreline Direct Exposure . . . . .. . . . . . . . . 25
< 7.2. On Sito Exposuro Pathways '. . . . . . . . . . . . . . . . . . . 26 7.2.1 On Site Potchie Well . . . . . . . . . . . . . . . . . 26 -
7.2.2 Direct Ground Plano Exposure . . . . . . . . . . , . . 26 7.2.3 Intruder Surface Related Exposure . . . . . . . . . . 26 l
L 8.0 . Conclusions . . . . .- . . . . . . . . . . . . . . . . . . . . . . . 27-u L
9.0 References . . . . .. . . '. . . . . . , . . . . . . . . . . . . . . . 30 l
Appendix 1 Veruont Yankee Site Plan . . . . . . . . . . . . . . . . . . 31 li i
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1.0 Introduction 1
Vermont Yankee Nuc1 car power Corporation (Vermont Yankee) requests approvci, pursuant to 10CFR20.302(a) to dispose of radioactively contaminated soil located beneath the plant Chemistry Laboratory floor, by leaving that material in place.
A leak in a Chemistry Laboratory sink drain inside the Radiation Control Area (RCA), was discovered early in 1991. It hao led to contamination of soil beneath the laboratory floor. It was found at the time of discovery that a portion of the drain line between the rink and the floor had developed a leak. Upon l detailed investigation it was determined that portions of the iuried drain lino had failed. This included an elbow connecting the vertical drain 4tne to horizontal piping, approximately 15 inches below the concrete floor, allowing ;
liquids poured down the sink to go inty the soil below the laboratory floor rather - than the intended 4.000_ gallon ca,mcity Chemical Drain Tank (TK-19A:
Wastes from this drain tank are processed for chemical as well as radionuclide content along with other plant liquid wastes.
As soon as it was determined that the pipe had failed, the pipeline was isolated from the laboratory sink such that no further contamination could be released via this pathway. The end of the pipe has been capped and the arcs of excavation has been backfilled with concrete to the original floor line so that the line is now inaccessible. Appropriate notations will be placed on building prints warning of - the materint beneath the floor and referencing the file number where !
documentat' .1 of these activities are kept.
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. New piping for the- sink has been run above the floor to the collection tank.
This new piping is accessible over its full length for periodic inspection to preclude a repeat of this event.
The length .of time this condition has existed is - not known and cannot be determined exactly, however, for purpose of this _ submittal, - an extended time period ot-ten years is _ assumed in ordet to bound the potential impacts associated with the drain line lookage. It-is estimated that 10 liters per week of reactor water have been routinely discharged to this sink as a result of chemistry 1
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.., .e sampling activit les. Other non radioactive liquids and cheinicals were also di:, posed of utilizing this sink. The results of radiological analyses of reactor !
water sampics wert reviewed for recent years to calculate an estimato ci the concentration and total activity that may have been discharged to this sink over i
timo. Sampina e# soil fet.in grade to bedrock vare obtained from a split spoon
, boring through tna Chemistry Laboratory floor. Samples were subsequently analyzed for chemical and radionuclido distribution and concentration.
1 The Chernistry Laboratory is located in the -lower level of the office building at
' the north end of the turbine building complex. During plant construction, this area- was - excavated- to bedrock at a depth of approximately 15 foot below the Choulstry Laboratory floor (El. 233' ) . The area under the laboratory was then filled to its current grade and the concrete laboratory floor poured. Removal of this contaminated snatorial is impractical due to the fact that it is located 4 -_
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underneath existing building structures. -Furthermore, concentrationa of l contaminants are very low and pose no significant risk to the health and safei e
, of plant workers or_ the general public.
! 2.0 Vaste Stream Descrintion l i s
[ 21 Physical Propertieg Discharge fr('i the Chemistry Laboratory sink seeped directly into the structural fill beneath the bailding floor sicb. The contaminated snatorial consists of approximately a 15 foot thickness of structural fill- placed during plant l construction, The fill itself is a uniform fine grained sand with some silt and minor-gravel. This is a well defined volume, confined on three sides by existine, j foundations and on the bottom by bedrock. If it is essumed the soil volume under -
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[ the entire 150 foot length of buried pipe has become contaminated, the total j volume as estimated by projecting a cone shaped spread of activity downward and ;
laterally-away from the horizontal pipe, is about 58,500 cubic feet. If it is assumed the leak was : local in nature, the zone of contamination may be 5-l represented by a 120* cone extending down 15 f t. , and would contain approximately
- f. 10,600 ft 8. The larger, more conservative value was selected for this cvaluation i
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to emphasize the litnit ed extent of the contamination. It la believed, because of uncertainty about the zone of contamination, the best estimate of the total activity cr.n best be inade from historical records of sink discharges.
A cornpilation was made of the constituents used in the lab. In addition it was determined that a volume of distilled and tap water mixed with or separately disposed of in the same drain was on the order of 200 liters per day. A snrnple testing program, described below, was then designed to assess the character of the chemicals added to the soil.
2.2 Sagpline. Procedures Saruples of contaminated soil were obtained through a hole cut into the laboratory floor. Both block samples from immediately beneath the floor, and t.plit spoon soil boring samples at various depths were talen. Samples were taken under controlled conditions, in conformance with written procedurrs and with direct inspection by personnel familiar with such activities. Three samples analyzed for chemical contaminants included a sample (SS-2) from the most contaminated zone near the Chernis try Laboratory floor surface, a sample (SS-3) from an intermediate depth and a sample (SS-5) from a wet zone, possibly the capillary fringe located at the bedrock interface. Nine saraples from the boring were analyzed for radionuclide content and distribution as described in Section 2.4. -
2.3 Chemical Propfr_t_ica Sampics of the soil were analyzed for chernical constituct,ts that would be characterized as hazardous by the EPA, The results of the sample analysis did not indicate the presence of any hazardous chemical constituents.
Analyses were performed on soil samples from the boring (MW-1) for volatile organic compounds (VOC EPA Method 8240), setni volatile organic compounds (SVOC EPA Method 82 /0), N metals (EPA Method 6010) , 4 other metals , and ammonia, chloride, nitrate and pH. The sample with the highest level of radioactive 3
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contarnination, (SS-2), was also analyzed by toxicity characteristic 1 caching procedure (TCLP) including TCLP metals , TCLP semi volatiles, and TCLP tero headspace extraction (EllE) volatile organics. In addition an organic vapor meter (OVM) was used to test satoples as they were withdrawn from scrupling equipraent.
OVM analysis used to screen samples during sampling operations detected no ,
organic vapors froin any of the sattples taken. Laboratory analyses showed neither TCLP ZHE volatile organics nor TCLP serni-volatiles to be present above detection limits. TCLP taetals were found to be below EPA regulatory limits. Volatile, setni. volatile and inctal test results for all three sampics are below regulatory li tni t s . The ananonia, chloride, nitrate and Ih parametern are also well within normal ranges. These tests support the conclusion inade by ENSR (Ref.1) that the soil beneath the Chemistry Laboratory is nqt a RCRA characteristic hazardous oaste.
2.4 Radiological Propert1es A continuous 3" diaineter split spoon boring, (MW 1), was taken from the Chemistry laboratory floor elevation down approxirnately 15 feet to bedroc... It was not possible to take this core sample directly adjacent to t' e pipe at the location l of the failed elbow between the transition from vertical to horizontal pipe rur.c.
I This was due to the presence of a concrete electrical duct bank buried just below the horizontal run of the drain pipe from the Chemistry Laboratory to the chemical drain tank. The boring was thus located approxitrately 4 feet from the vertical portion of the drain line inside the Chemistry laboratory. At l approxt:nate 1 vertical foot Intervals, three inch samples of the reinoved soil were retained and analyzed for radionuclide distribution and concentration. The l-environmental Technical Specification lower litni, of detection (LLD), as l
l- specifled in Technical Specifications, Table 4.9.3 for sedirnents, were applied to the ana' lyses. The samplec were analyzed in the "as found" inoist condition
( .vithout oven drying and are reported as " wet", which is the standard environmental laboratory practice for "in situ" sample reporting (for other than sediment samples). The moisture content of these satoples was estimated not to l- exceed 10-20%, by weight, thus density currection would not greatly affect the reported results, given other uncertainties in the collection and rneasurement 4
I program. Co 60 and Mn 54 were the only two radionuclides of plant origin i detected.
l TABLE 1 (Revised)
SOIL BORING SAMPLE RESULTS (Boring MV 1)
DEPTil BEIEW TOP OF FIDOR Co 60 Mn-54 (inches) (pCf/Kg, wet) 25.5 308 5 37.5 383 339 49.5 1131 914 73.5 296 12 104.5 351 1 109.5 221 7 133.5 166 <MDA 160.5 90 5
-184.5 879 <MDA AVERAGE 425 183 CONCENTRATION Block samples taken at the point immediately below where the pipe penetrates the floor had a Co 60 concentration that peaked at 1.1E+05 picoeurio/kg. It should be noted that several short lived plant related radionuclides were detected in this sample, indicating recent leakage, but were not detected in samples taken at depth. Table 1 presents the results of analysis of the core boring with respect to depth below the laboratory concrete floor. It might be expected, had the boring been abic to be taken in close proximity to the vertical pipe, the measured values would' reflect the higher values measured in the block samples.
Assuming this were to be the case, it would be indicative that the activity has not moved laterally to any great extent and that an estimate of total activity based upon one boring or the block sample, would result in an overestimation of total activity.
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Satopling in the boring was done using a split spoon st.mpler 3 f t long and 2" in diameter. The penetration depth used for each sample atterupt was only 2 ft. Duo to thn nature of the soil, a reintively dry, fine to medium-grained sand, recovery of samples averaged about 60% (of the 2 ft attempted for each split.
spoon satople) . The recovered portion of each sample represents about the top 601 of the soil depths penetrated in each attempt; the bottorn portion of sample sloughed out of the sampler.
Approximate 23 inch segments of each split spoon sample were selected and analyzed, une for radioactive and one for che rnical constituents. Samples to be analy::od were selected frotn the recovered material in each split. spoon based upon judgement of the representative nature of the sample as well as the spacing. For example, material such as loose gravel wash typically found at the top of ruch split-_ spoon samples was not selected for testing. As a result of the limited recovery and the ature of such a b ring operation, the accuracy of the sample depths may-vary as much as +/ 2 to 3 inches from the reported values.
Results of radiological analysis of soil boring samples indicate the presence of materials in_ the soil which could only have come from plant operation.
Concentrations are highest beneath the pipe (1.125E405 pCi/kg for Co 60), but cons,iderably lower with depth (90 pCi/kg Co.60 at 12 ft below the floor). The -
distribution of rade.nuclides suggests that the movemer.t of these radionuclides is, as expected, greatly restricted in the soil. Cobalt-60 was the principle radionuclide detected, and the only plant nuclide found below a depth of 4.2 feet below the Cheinistry Laboratory floor.
While radionuclido measurements done on the soil boring samples indicate that the higher values near the top of the soil column (in close proximity to the leakage) and a decrease with depth, a-relatively high value (879 pCi/kg) was obtained from tho bottom sample of boring in comparison with the sample taken just above it (90 pCi/kg at 13 feet). The core boring data in total suggests the following:
- a. Migration of radionuclides does appear to be retarded by sorption of -
ions onto soil particles. - There was some doubt about the de gree to which this would occur due to the use of crains for disposal of chernicals.
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- b. The concentration of radionuclides in the bottom sample of the boring coald be the result of the introduction of a relatively large quantity of activity put into the sink drain at some time in the past, or more likely, could also result trom "ponding" of activity at a low point at the top bedrock, as a result of lower vertical water velocity and longer contact tiac for ion exchange to take place.
- c. Cobalt-60 (and we assume Trititun) may have approached or crossed into the grou..J water regime, and may be subj ect to present or future movement through ground water, although no sample of water was obtainable frorn
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the screened well placed in the chemistry laboratory floor.
f 2.5 Estimate of 'Lotal Activity Given the data from the soil boring, it is felt that a conservative estimate of the u tal activity present in both the soil zone immediately below the laboratory floor and above the ground water table , as well as any fraction which might have entered the ground water zone, could best be determined by asstuning a 10 liter per week quantity of reactor water, at a conservative concentration of radionuclides of concern, was disposed of through the sink drain over an extended period of time, This value is believed representative of the quantity of liquid released to the ground based upon the following: _
Vermont Yanke Technical Specification 4. 6. B.1.a. states "a sample of reactor coolant shall be taken at least every 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> and analyzed for radioactive iodines of I 131 through 1-135 during power operation".
Section 4.6.B.1.b, states "an isotopic analysis of reactor coolant sample shall be made at 1 cast once per month". ,
Conversation with plant chemistry personnel and review of completed plant chemistry procedures indicates 1 liter samples are collt rced and brought to the Laboratory for analysis on a daily basis.
The basic assumption is that these samples were disposed in the laboratory 8
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sink, under the assumption the contents was going to the Chernistry Drain Tank.
One sample per day equates to 7 liters per week. Thir value is rounded up to 10 liters per week, for purpose of this evaluation.
It is reasonabic to ascumo that the drain leak began as a small corrosion hole in the drain line near the cibow. This allowed small quantities of liquids to leak into the soil As tirne progressed, the corrosion continued and the leuk increased in magnitude and an increasing fraction of the material discharged to the drain sink leaked. It is unlikely that the entire volume of water ler.ked out g5 of the pipe. Undoubtedly : significant percentage of water followed the path of least resistance, down the open pipe. Neither the exact time, nor magnitude of leakage is precicely known, therefore it is assumed conservatively assumed that ,
all of the estimated liquid discharged to the sink for the previous 10 year period resulted in leakage. It is believed this approach has results in a co iservative estirnation of the total activity that may have been discharged to the sink and the calcu'.ated radiological impact represents the upper bound of exposure.
It is assumed that 100% of the associated activity put down the drai'i is released to the soil. A 100 ml aliquot of the rnonthly sample is analyzed for gamma etnit t e rs . A review of reactor water analpis results for the period from 1987 -
through 1990, indicated that the fifteen 1 month period from May, 1988 through July,1989 represented conservatively high values for reactor water activity.
These more recent results are used to estimate the radionuclide concentration of ,
gamma : mitters . Tabic 2 lists the monthly concentrations of Co-60, Mn-54, Cs-134 and Cs-137 measured in reactor water.
It is known from analyses of other waste streams that nuclides important to 10CFR61, which are not gamma emitters, are also present. In order to account for those radionuclides, whose half lives are of an order of 1 year or longer, a representative reactor water sample previously analyzed 4r Part 61 nuclides was reviewed for applicability to this situation.
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... .., l TABLE 2 REACTOR WATER ANALYSIS
SUMMARY
DATA DATE Co 60 Hn-54 Cs 134 Cs-137 i (uC1/ml) (uCi/inl) (uCi/in1) (uC1/inl) l 5/88 9.03E 05 5.23E-05 9.11E 06 1.49E 05 6/88 8.38E 05 5.45E 05 1.50E 05 8.08E-05 7/88 5.35E 05 3.96E-05 1.48E 05 1.50E 05
-8/88 4.49E-05 3.45E 05 No Data 7.32E-06 9/88 '5.47E 05 3.96E-05 4.19E 06 4.33E.06 10/88 .5.99E 05 3.85E 05 1.89E-06 4.08E 06 <
11/88 3.96E-05 5.88E-05 5.40E 06 7.35E 06 12/88' 8.38E 05 5.52E-05 5.25E 06 5.92E 05 1/89 1.88E 04 1.36E 04 1.65E-05 2.43E-05 ,
3/89 1.03E 03 4.71E 04 2.37E-04 2.11E 04 4/89 4.87E-05 5.04E-05 1.22E-05 2.48E 05 5/89 5.82E 05 4.44E-05 9.90E-06 9.31E-06 6/89 6.06E 05 4.34E 05 6.01E-06 5.35E-06 7/89 8.04E 05 4.?9E-05 2.77E 06 3.28E-06 AVERAGE. 1.42E 04 8.31E-05 2.62E 05 2.98E-05 f
Table 3 lists radionuclides and their relative concentrations with no decay and also the concentration with a decay period of 2.5 years. 2.5 years represents
- a very conservative travel time to the river and neglecting soil retardation
} effects. We have de te rmir.ed , for a conservative evaluation, that seven 1 l radionuclides, H-3, Mn 54 Fe-55, 0o 60, Cs-134, Cs-137, and Sr-90 should be-considered as present. These seven radionuclides represent 99.9% of ths total jT . reactor coolant _activi_ty present after 2.5 years.
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TABLE 3 TYPICAL REACTOR VATER RADIONUCLIDES
!welide llalf-life No Decay 2.5 Yr Decay
Years) (uCi/in1) (uci/ml) _
I 11 3 - 12.2 2.0E 02 1.8E 02 Co 60 5.272 1.4E-04 1.0E 04 Fe 55 2.70 2.4E 04 1.3E-04 Mn 54: 0.855 8.3E 05 1.1E 05 Zn 65 0.667 1.7E-04 1.3E 05
-Sb 125 2.77 2.3E 05 1.2E 05 Ce 144- !0.778 8.0E 06 8.6E-07 Cs-134 2.065 2.6E 05 1.1E-05 Cs-137 30.17 3.0E-05 2.8E 05 Sr-90 28.6 6.9L 08 6.5E 08 Zr-95 0 175 3.9E 04 2.0E 08 co 58 1.194 7.1E 05 9.4E 09 Fe-59 0.122 1.,6f 04 1.1E-10 Cr 0.076 1.7E 2.0E-14
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The_ concentrations of radionuclides not rneatured in tha monthly samples were based upon the relative abundance of radionuclides in the previously mentioned laboratory analysis of a reactor water sample.
For purposes of bounding the potential impact, it is assumed that 10 liters of reactor water per week, at the batch" values of Table 4, have been disposed in the sink over an arbitrarily long 10 year period, and that 100% of tnis water has l
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TAELE 4 RADIONUCLIDE DISTRIBUTION Radionuclide Concentration " Batch" Activity *
(uC1/ml) (uci) 11 - 3 2.0E-02 2.0E+02 Mn 54 8.3E 05 8.3E 01 Fo 55 2.4E 04 2.4E+00 Co 60 1.4E 04 1.4E+00 2.6E-05 2.6E-01 Cs-134 Cs-137 3.0E 05 3.0E-01 Sr 90 6.9E 08 6.9E-04
- Activity in a 10 liter " batch" s
TAT.LE 5 ACTIVITY BUILDUP BELOW Tile CHEM 1AB FIh0R VITil TIME Radionuclide llalf-life Qo Q*
(Y ars) (uC1/ Batch) (Total uC1) 11 - 3 12.2 2.0E+02 8,0E+04 _
Mn 54 0.85476 8.3E-01 5.4E+01 Fe-55 2.7 2. 4 E4 00 4.4 E4 02 -
Co 60 5.272 1.4E+00 4.1E4 02 __
Cs-134
- 065 . 2.6E 01 3.9E401 Cs 137 30.17 3.0E-01 1.4E+02 Sr-90 28.6 6.9E-04 3.2E-01 Total Activity 2.1E+02 S.1E+04 Total activity present after 10 yrs of weekly " batch" releases 12
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gono directly to the soil . underlying the chemistry laboratory. With a constant input and considering decay, it is mathematically possible to calet late a total inventory at any point in time. This analysis assumes a ten year period of ,
weekly Tabit 4 " batch" releases. Table 5 tabulates the postulated total inventory present at the end of an arbitrary 10 year period of weekly " batch" l 4
releases. j
- p, 3.0 Description'of Pronosed DiscosaLf.ethgd it is proposed to dispose of the activity by 1 caving it in place where it currently residas. By teratrsting the releast of liquids into the failed 6 rain ;
line, there is no significant drivin6 force to cause any further movement of the activity now in the soil below the Chemistry Laboratory floor any deepor toward i the ground water regime. The total quantity of activity is sufficiently small ,
that it does not ' currently present a - direct radf ation~ exposure hazard to the 3 Chemistry Laboratory. To remove the material would, however, require a major excavation effort under __ the laboratory floor and in proxienity to the reac.ar building foundation, and other critical structures, as well as exposure to the workers performing _the exenvation. The direct exposure as well as potential
- airborne exposure to current workers peritraing romediation would be far greater than:the potential-for exposure to a future population. In fact, there is no-practical way for this _ material to be_ removed from under the plant at this time.
c LO Ceolony and Hydrolorv Considerations Natural soils at the site' were removed at the time of plant construction so that major plant structures could be founded on bedrock. Structural fill replacing
, soils consists of fine uniform sand with some silt and minor gravel. Natural soils remain _around the periphery of the site. These natural soils consist of
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= at loose ' silty - fine-grained sand- 5 to -15 ft thick underlain by medium dense, glacio-fluvial, s11cy fine-brained sand 10 to 20 ft thics. Where bedrock surface elevation is below + 220 ft (ms1) there also exists deposits of varied fine sand
- and silt with a few thin clay layers. Thickness of these varied deposits ranges
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up to 12 fc. They are typically underlain by a few feet of sand and gravel.
Bedrock under these soils is hard, fresh nassive gneiss. The bedrock surf ace is undulatory, varying in elevation from about +190 ft to +730 ft (ms1), in the vicinity of the major plant structures. The bedrock surface rises to elevations of +250 ft to the west side of the plant site, and r'.rops well below 4 200 f t to the east beneath the Connecticut River. Grade in the vicinity of plant structures- is about +250 ft. The top of the Chemistry Laboratory floor (12" ccncreto) is +248'6".
Ground water depth an the vicinity of plant structures is about +230 ft. Avera6e elevation of the Connecticut River is +220 ft. The building housing the Chemistry Laboratory is about 300 f t fror the river. Ilydraulic gradient is thus rather high at 0.05 f t/f t. Ground water flow rates have been estimated at about 32 feet / year, through natural soils, and may be a factor of two or higher through the' fill materials. For this reason, oniv 2.5 years is assumed for travel tirae to the river.
! -. Bedrock was encountered in the soil boring !G 1 at an elevation of about +233 ft.
, . The bottom 1.5 to 2 feet of soil encountered in the boring just above the bedrock surface was damp -and a well screen was installed in the hole to attempt'to measure water levels upon cumpletion of sampling. Itowever, since the well installation no water has accumulated in the hole The damp soil encountered
. thus -may have been a capillary fringe, but more likely was the remnants of water j leaked from the subject pipe. Thus the natural ground water surface appears to be below the bedrock surface beneath the.Chemi,try Laboratory. Original site drawings show ground water elevation in natural soilr. to be at about elevation
+235 in' this area. .The present ground eater table may be lower than when original soils were present due to the somewhat lower permeability of those :; oils
, compared with the strucrural fill and the possible alteration of ground water h f1'ow- regime due the construction of building foundations.
The alteration-of ground water due to floods was considered and dismissed as l insignificant. -'Ihe 100-year flood on the Connecticut River reaches an elevation of only +2n just below the typical current level of ground water. The 500-year 14 l'
, . . . . . -.h,.m.. , %,..,_,l...,.%__m .w.~ , . , , , , , .
i flood reaches an elevation of only 4 feet higher at 4232, but has a very short duration ef only a few hours.
Ground water flow across the entire site is directly toward the Connec .it River (Vernon Pond) . Two possible paths to the river appear to exist for ground water in the vicinity of the Chemistry Laboratory. It either flows northeast following the path of a bedrock depression and fortne r gully (filled in during construction), or it flows cast, perhaps intercepting fill along the 126 inch diameter circulating water intake pipe trench.
Four potabic water wells exist on site. All of these wells are either up-gradient or decidedly away frota any potential ground water path from the Chemistry Laboratory to the Connecticut River.
In general, bedrock permeability is very low. Studies have identified photo lineaments whi h appear to be some long, narrow fracture tones on the site.
Ilowever, none these zones are located where they might influence flow of ground water from the Chemistry Laboratory area to the river. Thus, the bedrock is considered an aquiclude and infiltration of the radioactivity into the bedrock is not considered probable.
Major plant structures as well as adjoining residential properties are depicted ,
on FSAR figure 2.2.4, Station Plan. This figure is included as Appendix 1 to this submittal. In general, the residences located on the west of the site or.
Cov. Hunt road have individual shallow wells as potable water supplies. As mentioned previously, the ground water flow in from west to cast to tue Conaccticut River, and away frun the residences. The Chemistry Laboratory, the source of the leakage is located in the lower level of the "Of f .t.i Bldg",
adj ac ent the " Turbine Bldg" . The grid scale of the plan is 500'. The main potable water supply for the site is provided by the " West Well", whose location '
is shown near the 345 KV switchyard.
15
~
I' l l
.j o: .,c l I
-5.0 Environtsental Samoling Pronrarn v
5.1 Vater Samoline Descriotinn In accordance with Technical Specification 3.9.C.1 (and Table 3.9.3), river water -j is sarrpled at two locations on a inonthly basis. The samplo locations and descriptions are presented in Table 4.1 of the Off Site Dose Calculation Manuni (ODCH).- At the upstreaa control location (WR 21), a grab sample is collected !
inonthly. At-the downstreara location (WR-11), aliquots of water are collectcd autornatically, approximately every two hours, by a cotapositing sampler. The composited sample is, picked up monthly. Each sample is aralyzed for gamma-e.nitting radionuclides. On a quarterly basis, the three taonthly samples are ;
composited by sampling location and are then analyzed for Tritium.(ll-3).
Also in accordance with Technical Specification 3.9.C.1, sediment samples are collected seini-annually frorn two_ (2) shoreline locations. A single grab sample is collected from the first location (SE 11), dwnstream of the plant discharge on the west shore of the Connecticut River. Multiple grab sarnples arn collected ,
froin the cecond location (SE 12), upstream of the dischargo' point where the North
-Storm Drain einpties _into 'the west side _ of the Connecticut River. Grab samples collected at these two locations are analyzed by ganea spectroscopy.
Crab samples-of ground water are co11ceted quarterly froin three well locations.
These are WG 11 on the plant site, G-12 in the SSE sector at 2.0 kra, and UG (the control) in the N sector at 14.3 km. (WG-22 replaced WG-21 as a euntrol during the first quarter cf 1991, when Station VG-21 became inaccessible,) Each sample is analyzed for garama emitting radionuclides and tritium -(H-3).
Technical Specification 4.9 C.1 (and Table 4.9.3) provides the minimum detection capabilities (Lower Limits of Detection; or LLDs) for each required sample analysis. The LLDs for C 60 and 113_ in ' river or ground water are 15 and 3000 pCi/1, respectively. -There is no LLD specified for Co 60 in sediment, although it is specified for Cs-134_and Cs 137.-- LLDs are typically achieved at levels ,
one-half or better than the values noted above.
16
. ~. - - - . - - - . . - . .....-... _ .- _ . - . - . - - - . . . . - . . - , . - . - , . . - . -
e .
1 Technical Specification Tabic 3.9.4 provides the Reporting Levelv for river water and sediment samples. The Reporting Levels f or Co-60 and 11-3 in river water (i.e. non drinking water pathway) are 300 and 30,000 pCi/1, respectively. For ground water (the drinking water pathway), the Reporting Levels are 300 and 20,000 pC1/1, respectively. For Co-60 in sediment (only applicable to individual grab sampics at the North Storm Drain Outfall), the Reporting Level is 3000 pCi/kg(dry).
5.2 Sampling Program Results The presence of Co 60 or 11-3 in river water and of co-60 in sediment were investigated for a 13-year period (3rd Quarter 1977 through 1st Quarter 1991 -
J.e. dating back to the time the Yankee Environmental Laboratory began operation). Over that period, co 60 was detected in many samples from Station SE-12 (North Storm Drain Outfall), with a maximum concentration of 490 pC1/kg (dry). No Co-60 was detected in sediment from the downstream sampling location. D SE-11. Likewise, no Co-60 was detected in river water during that period, either at the upstream location or at the downstream composit.ing location. The presence of Co 60 in sediment near the North Storm Drain outfall has been attributed in the past to rain water runoff from the Turbine Building roof carrying lov levels of deposited Co-60 from Turbine Building roof vent releases.
Tritium (H-3) has been detected during tne above period on several occasions at Station VR-11. The occurrence of tritium in river water there during 1977 and 1978 may have been due to nuclear weapons testing fallout, as the same levels d were detected in Station VR 21 (the control) as at VR-11. Tritium was also detected in river water at VR-11 on one occasion in 1982 and on one occasion in 1984.
6.0 Radiological Conside rations Scenarios that have the potential for radiological impacts to members of the ,
public have been postulated for the purpose of determining maximum possible 17
i f
,-',' , _' , I doses, . One scenario assumes the contarnination inigrates off site to Vernon Pond on the Connecticut River where it becornes the source term for subsequent direct uptake as drinking water, indirect uptake af ter concentration in fish and subsequent consumption by inan, use of the water for crop irrigation, and direct exposure frorn standing on the shoreline of the pond. A second scenario assumes the material rernains in place until the plant is decommissioned and control over the site is no longer maintained. At that time an intruder arrives on site, drills a well into the soil containing the activity, and/or exhumes the material I and spreads the activity over -the ground, grows crops, feeds a dairy cow, and supports a family on the site, These scenarios are mutually exclusive, i.e. , one or the other rnay occur, but both cannot occur. Neither can the intruder be exposed via the drinking water pathway with the crop production / ingestion pathway simultaneously. The radiological evaluation has considered all scenarios and assurnes the higher. radiological irnpact case takes place.
Another scenario considered is that the radioactivity reaches the on site potabic well used by the plant, during the - current period of plant operation. This potential exposure pathway does not include acmbers of - the public but is restricted to plant ernployees. The previously described environmental monitoring prograrn (Section 5.1) is designed to detect sny increase in activity in ,
environmental media due to plant operations. The principle -on Zito potable drinking water well is also included in this program. To date, no plant related -
radioactivity has been deterrnined to be present in any well water sample. None the less, a potential exposure is calculated for this pathway.
'6.1 Potential Off Site Exnosure Pathways In this scenario it is assumed the activity moves at the rate of ground water and arrives at Vernon Pond. With a distance of approximately 300 f t and an estimated
+
groundwater velocity of 32 ft/yr, it is enpected to take 9+ years to arrive at the pond.- Because of _ the _ uncertainty over the possible start time of any rnigration, - it is assumed that 100% of _ the ' estimated activity in each weekly
' batch" arrives at the river 2.5 years - af ter its release. It is assumed a continuour release exists and the annual release consists of the sum of 52 weekly - ,
18
_ - . _ . _ ._ _._ _-m_._ _ _ - . __- _ _ _ _-_--__ _ _ _ -. _ _ _ -_ _ , _ _ , _ ~ - _ - -
I
/l.* : -
, .l$l
- batch" releases. Effects of retardation by the soil are neglected. Table 6 l
- presents the activity assumed to reach the river on an annual basis, it is ]
assumed this release. rate continues for 10 years.
TABII 6 ANNUAL ACTIVITY RELEASE ASSUMING 2.5 YEAkS OF DECAY Ra'dionuclide llalf .Je- Q, Q4 Annual Release " l i ? .';
.. (Years) (uC1/ Batch) (Total uCi) (Total uC1) l 11 - 3 12.2 2.0E+02 1.8E+02 9.1E+03 Mn-54 0.85476 8.3E-01 1.1E 01 5.7E+00 ,
Fe $5 ~ 2. 7- -2.4E+00 1.2E+00 6.5E+01 !
C, 60 5.272 1.4E+00 1.0E400 5.3E401 ;
Cc-134 :2.065 2.6E 01 1.1E 01 5.9E+00 Cs-137 30.17 3 0E-01
. 2.8E 01 1.5E+01 Sr 90 28.6 6.9E 04 6.5E 06 3.4E-02 _
t kfeckly batch activity .rel ase d to river, af ter 2.5 year decay.
Annual, release,_52 times the weekly batch release, i
t r
6 ' 1.1'
. Approagh to-Analysis I
- 1. g The inethods described in Regulatory Guide 1.109 (Ref. 2) are generally applicable to analysis of the radiological impact of off site releases. The dose model used l: for estimation of total exposure is IDLE (Ref. 5) and is based upon Regulatory Paida 1.109. ~ The entire inventory of activity is assumed to be continuously 1n l- released via a liquid effluent pathway to the river. The release flow rate is l' assumed to be small and- the activity renains undiluted as it 'noves to the river.
.i credit for 2.5_yects decay is taken. ,
t 19 4
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%.+w,. ,-,-.--=-.wm.- w.., ew -r-#,-=... -s-,- e- #---,,-,-..---n-,. ,+,,e -, -cw er , ., r
m.____.._____ _ . _ . _ _ . _ _ _ . _ . -
'i ~. l 6.1.2 Desgriotion of Scenario 1 The scenario assumes an essentially constant release rate over a ten year period, such that the activities listed in Table 6 reach Vernon Pond annually. Dilution is assumed in Connecticut River water flowing by the plant. The FSAR (Ref. 3),
. states the river flow is typically 10,000 efs, with no less than 1,200 cfs during -l the dry season. For purpose of this evaluation, a conservatively low value of )
100 cfs 'is assumed for the entire year, as the dilution flow.
Pathways considered in this evaluation include consumption of fish, use of the water - to irrigate leafy and stored vegetables, and sediment irradiation to recreational users - of the shoreline. Regulatory Guide 1.109 (Ref. 2) ,
bioaccuinulation factors, consumption rates, and shoreline activity times are used in the calculation of the radiological impact to man over a one year period. The time period selected is the tenth year, which calculates the annual dose in the tenth year, from releases that year as well as dose resulting from residual activity from the previous nine years of releases.
6.2 Potential On Site Exposure Pathways 4 l
Another hypothetical scenario is that activity reaches the on site potchlo well; with subsequent consumptien of the water by plant employees. Monitoring of the water supply will ensure this will not constitute an exposure pathway.
The Draft Environmental Impact Statement for 10CFR61 (Ref. 4) also considered
^
several potential exposura pathways in its radiological analysis, among them was an intruder settling on a site once institutional control was lost.
i l- ~ The scenario considered for this application, to demonstrate the extreme case and the~ insignificance of the total exposure,' consists of an intruder settling on the
+
planc site = af ter = termination of the plant license and decommissioning and dismantling of all-buildings -- It is assumed this intruder arrives 20 years from
- now and either sinks a well into an aquifer containing the residual activity, or l
unearths all of the activity present at that time, ~ spreads it about, plants and 20 l--
- - ..a.,. .- _ . - - , , _ , - - - - _ . . . _ - _ . ~ . . . - . . -
. _ . - . _ . _ -. _ _ _ ... __. _ _ _ _ .. _ _ .___.- _ __._ .. . _ ._.m._
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,J.*j. I harvests - crops, and raises a milk cow on the land. (These two scenarios are mutually exclusive).
l 6.2.1 Anoroach to Analysis l In general, the dose model used for estimation the total exposure is from Regulatory guide 1.109. For the ingestion pathway resulting from the intruder ;
settling on the. site 20 years in the future, it is assumed that the decayed' !
activity is spread over a sufficiently large area to support the growing of crops as well as the grazing requirements of one cow,-in accordance with the values ,
suggested in Regulatory Guide 1.109. This total area is calculated to be 4,086 t
sq. meters, i Doses were calculated for the intruder scenario in which food crops, grazing requirements for .a milk - cow, and inhalation of resuspended material were considered, for the whole body and seven organs to each of four age groups; infants, children, teens, and adults, using the consumption rates , or usage factors as listed in Reg. Guide 1.109.
The following two scenarios use analysis techniques that differ from a strict :
Regulatory Guide 1.109 type of analysis. Differences in the scenarios are such that they: do not lend themselves to a direct application of R,0.1.109. One is the direct ground plane from a finite size source and the' other is a well mater ingestica pathway in which the activity is assumed to be below the ground level, c The direct. ground plane exposure component is determined by the DIDOS computer program (Ref. 6) which' calculates. doses from a cylindrical source of stated
. density, and is applicable to this assumed scenario consisting of a ground plane source. The whole body ground plane direct exposure fraction, af ter exhumation is calculated assuming the decayed activity is exhumed and spread in a layer equivalent to the plow depth (15 cm.) used in Reg. Guide 1.109.- This equates to la circular area _ of 59 meters radius, based upon the previously estimated 58,500 cubic feet of contaminated soil. It is assumed the receptor stands at the center of this circle for 8760 hours0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br /> per year 21 p v .~m --w',
r --g mwpy-- w,+ ,,en.s e 4. ~..e v. ..,_.,,mn,-,w- ,_o..,av, .-s - sw-r., ,,mn.x. ,N .,,...,a--,-n -
.vae.--e m e- -, -,.mp
. ._ . _ . - . , . . _ _ _ . _ _ _ _ . . _ - _ _ _ _ . . . _ _ . _ _ _ _ . ._.m___-_ _ . _ _ . .
,0' p -.
TABLE 7 ACTIVITY Al'IER 10 YEARS OF WEEKLY RELEASES, i FOLIhWED BY 20 YEARS OF DECAY Radionuclide llalf-life Q. Q.
- Q4 .
(Years) (uC1/ Batch) (Total uC1) (Total uC1) 11- 3 12.2 2.0E+02 8.0E+04 2.6E+04 ;
Mn 54 0.85476 , 8.3E 01 5.4E401 4.9E 06 Fe-55 2.7 2.4E400 4.4E+02 2.6E+00 ,
Co 60 5.272- 1.4 E+00 4.1E+02 3.0E+01 Cs 134 2.065 2.6Ee01 3.9E+01 4.8E-02 Cs-137 30.17 3.0E 01 1.4E+02 8.7E401 Sr 90 28.6 6.9E 04 .3.2E-01 2.0E 01 Total activity present af ter if yrs of weekly
- batch" releases
- That activity af ter a 20 year decay period
.The: radiological impact of the on site drinking water scenario has been evaluated ;
using three approaches. It is postulated that a small family settles on the site 20 years in the future after plant closure and digs a shallow well to obtain its drinkin6 water needs.
The activity in Table 7 is that activity remaining after 10 years of continuous releases followed by a 20 year decay period and is that which serves as the source term for the calculating of'the intruder scenario exposures.
Approach 1
'~
The-total activity in th. right hand column of Table-7,-- Q4, forms the activity source term. It is assumed-that; migration away from the area has not occurred, nor is any activity retarded it its movement to an
- underground pool", which is the source of drinking water. Applying the assumptions presented in Ref. 4, for 22 L 4 p
H
a % ' .p '.
natural percolation of precipitrtion a into groundwater systein, the measured l precipitation for the site, and asstuning a sina11 area of recharge, a conservative value of total dilution water volume (and hence specific activity) can be postulated for the scenario. The methodology presented in Ref. 2 can then be applied to calculate radiological impacts.- -
The average precipitation for Vermont Yankee for the period 1961 1990 was 40" per year. Ref. _4 lists an annual precipitation rate of 41" and a percolation rate of 2.9", for a PE site. A recharSe area consistin6 of a circle of 500 ft radius (7.85E+05 sq. ft.), representing a sina11 fraction of the site area upgradient of the Chernistry Laboratory, is assumed. The volume of water percolating to the "undorground pool" at a rate of 2.9" per year for 20 years is equivalent to +
1.075E+11 ml. Using this volume and the activity from Tabic 7 results in the specific activitios'in the drinking vater " pool: as listed in Table 8, below.
Tabic 8- ,.
Radionuclide Activity and Concentration in Drinking Water Nuclide- Total Concentration Activity.
-pci -
poi /ml H3 - 2.6E+04-2.4E-07 Mn 54 4.9E-06 4.6E-17 Fe-55 2.6E+00- 2.4E 11 cco 60 3.0E+01 2.8E 10 l
l Ca-134 4.8E-02 4.5E 13 Cs-137 .b_, 7 E+ 01 8.1E 10 l
-. S r - 90 2R-1 ,
1.8E-12 L
23
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y g, , , , , ,g .p, , ,.,,, .
I, Approach 2 An evaluation using the RESRAD code (Ref. 7) with the following assumptions:
Zone of contamination consisting of a cube with sides equal to the depth to bedrock, 4.7 meters.
Source term consisting of the activity present after 10 years of weekly discharges, Table 5, Q,, time since spill,10 years llydraulic conductivity, 1.42E 02 cm/sec.
Groundwater velocity, 2.6E-02 meters / day Effective soil porosity, 0.33 (dimensionless)
ADEIoach 3 NUREG/CR-3332 (Ref 8), provides a relatively simple appranch to ground water transport of radionuclides. The same nasumptions as were used in the above approach were used. The results are expressed as a radionuclide concentration in the aquifer at the well location. The well is assumed to be located next to the failed elbow in order to get the maximum aquifer concentration and resultant radiological impact. The methodology of Ref. 2 is then applied to determine the dose.
7.0 __ Radiological Imoacts 7.1 Potential Off-Site Exposures The maximum radiological impact due to the sum of off site pathways is 9.8E-04 MREM to an cdult whole body, and 1.5E-03 MREM child organ dose (liver) . These exposures are subdivided into the following individual pathways.
24
- . s
,*,4 , .s 7.1.1 Drinkine Weter Itwerd1ED Consumption of drinking water frorn containination that has traveled undirninished though the soil, except for a 2.5 year decay during travel, diluted in the minitmuta flow of the Connecticut River, and consurned at the rates specified in Reg. Guide 1.109 (Ref. 2) for the four age groups (infant, child, teen, and adult), results in a rnaxitoum whole body dose to an adult frora drinking water ingestion of 2.5E-05 MREM. The rnaximurn organ dose is to an infant liver of 6.3E-051 GEM. The tacthodology used for analysin is that described in Regulatory Guide 1.109 (Ref. 2).
7.1.2 Fish Ingestion Pathway Bioaccumulation factors and consumption rates frorn Reg. Guide 1.109 (Ref. 2) are applied to fish ingestion. The inaximum whole body dose is to an adult and is estirnated to be 8.3E 04 MREM. The maxirntun organ dose in to a teen liver and is 1.2E 03 MREM.
7 .1. 3 Irrigation Exposure Pathway The diluted water in Vernon Pond is used as crop irrigation water in accordance with Reg. Guide 1.109 (Ref, 2) for a 8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br /> period. The inaximurn whole body annual dose is to a child and is estimated to be 1.2E-04 MREM. The taaximum organ dose is to a child liver and is 4.0E-04 MREM.
7.1.4 Shoreline Direct Exposurn As above, using Reg. Guide 1.109 guidance (Ref. 2) results in a maximum whole body dose of a teen of 2.2E 05 MREM frotn standing en the shoreline.
25
), . .- l /t, 7.2 On Site Exnosure Pathways 7.2.1 On Site Potable Well For the on site.well during plant operation (next 20 years) it is asstuned that the sampling program will detect any significant increase in activity and that i corrective actions will be implemented before any individual receives a significant dose.
For the on site well intruder scenario, the 3 approaches result in similar results. - Approach I calculates a maximum whole body dose of 6.4E 02 Mrem /yr to -l an adult and a maximum organ dose 'of 1.9E 01 maem/yr to the infant liver. I Approach 2 calculates a whole body dose of 4.6E 02 mrem /yr. (OrCan dose not calculated.) Approach 3 calculates in a whole body dose of 3.8E-01 mrem /yr and serves to provide an upper bound to the radiological impact.
I 7.2.2 Direct Ground I-lane Exposure At year 20 in . the future (Table 7. activity), exhumation of the 58,500 ft8 (1.657E403 Ma) of material and spreading in a layer equivalent to the plow depth (15 cm), results in an continuous annual expoaure of 2.7E-01 MREM, as calculated by DIDOS, a small fraction of exposure due to natural background.
]_.2.3 -Intruder Surface Related Exonsure Using'the methodology of Re6. Guide 1.109 (Ref. 2), and the activities from Table 7, results in the maxistun calculated pathway exposures as listed in Table 9. The assumptiona used include intruders consisting of a couple with an infant, child, and teen all getting 100% of their food from crops grown on contaminated ground and allk from a cow wh6se entire food supply was also grown on this land. This represents an extreme case that while not necessarily credible, does represent
.an upper bound on what the potential ran o ogical impact might be.
ll 26 1
l
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39
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, TABLE 9
.f INTRUDER EXPOSURES, BY PATHWAYS
&lk ' ' ,b_
"ty ,
D' Max Vhole Body Dose Max Organ = Dose Pathway c h:1d-Lung
- (MREM) (MREM) f' . Inh'alation 1.1E-01 6. W - 01 y 'resuspension)-
fj -ored Vegccables-- 4.9E 01 4.8E-01 y, afy vegetables 2.5E-02 2.4E-02 i - Cev Milk 1.6E 91 1.5E-01 y . ,
^ ., Jrinking Watcr'
, 3.8E 01
')irect Grouc'd plane 2.7E-01 2.7E-01
-t l(from6.12above)
Totals 1.5E+00 1.6E+00 5
A Q Cenclusions The tor' t% .:y calculated to have been released over a ten year period and
,emaining .ow,- is-of the ordet of 81.3 mil 11 curies,.80 mil 11 curies of which is
. calculated 1 to 've Tritium, based upon its concentration in reactor water.
Dilution with the estimated 200 liters per day of. otiner. non-radioactive liquids
' dirr.harged through this - sink over the same titro period, result;s in a tritium
-l concentration, ' discounting ady d ' ecay or further dilution, of the ordar of 1.0E-03 uCi/m1, =Tho.10CFR20 Appendtx B,- Table II ellowable release concentration for Tritium is 3E-03 uCi/ml. , thus, the current estimated inventory, at its present estimated concentration, could be released under current regulation. No other radionuclide under consideration approaches the limits speci.ied in 10CFR20.
( ,
. The alternative to in-place disposal is exhumation of this materis.1 a d possible N
disposal as radioactive vnste, or the subject of an additional application for
' disposal by - alternate means, at a great increase in cost with no associated significant increase in benefit. The material, being located under plant 1:. 27 c
m o
t J
l, . f, f TABLE 10 SUMMAP.Y OF EXPOSURES OFF-SITE PATHWAYS WB-(MREM) ORGAN (MREM) _
Drinking Water Ingestion 2.5E-05 6.3E 05
-Fish Ingestion- 8.3E 04 ,
1,2E-03 Irrigation Exposure Pathway 1.2E-04 4.0E-04 Shoreline Direct Exposure 2.2E 05 -
I~
ON-SITE PATHWAYS
[ a, fWellWater' Ingestion- 3.8E 31 1.9E-01 Dircct Ground Plane 2.7E-01 -
Inhalation (Resuspension) 1.lE-01 6.5E-01 Stored Vegetables 4.9E-01 4.8E 01 Leafy Vegetables 2.5E-02 2.4E-02 Cow Milk 1.6E-01 1.5E-01 structures, it = impossible to safely remove without essentially decommissioning a large portion of the plant.
4 In the past the NRC staff has considered'the potential effects on the environment of licensed material from operation _ of nuclear power plants , and in the evaluation _of radiological impacts, generally conclude that operation of plants will contribuLa only a small- increment of the radiation dose that . arsons living !
in the area normally receive from background radiation, and fluctuations of the i natural background dose -may be expected > exceed the small dose increment 1
contributed by the operation of the power plant.
Since the disposal herein proposed involves licensed material containing a small f- fraction of the radioact!vity already considered acceptable under the Radiological Effluent Technic $1 Specifications (RETS), and involves pathways much lesa _ significant, and in a -radiochemical form much less mobile than those 1
l 28 L
i
ud g^ ? p.
. .. 4*j considered in the RETS, it is concluded that this applih tien has an insignificant radiological impact.
In reality it is not- expected that loss of control over the Vermont Yankee site will occur in the near teru time frame, however, even should an intruder settle atop the disposed material, the radiological consequences would remain minimal.
Vermont Yankee, therefore requests approval from the commission to dispose of an ,
existing quantity of radioactively contaminatt aterial containing an estimated total of 82 aci, (80 mci of which is tritium), by leaving the material in pince in its current location under the floor of the plant Chemistry 1.aboratory.
i:
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- .s 9.0 References
.1. ENSR Consulting and Engineering, Environmental Site Assessment of Chemical Laboratory Subsurfaco, Vermont Yankee Nuclear Power Corp., Vernon, VT.,
April 1991,
- 2. USNRC Regulatory Guide 1.109, Calculation of Annual Dose to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10CFR50, Appendix I, rev.1, October, 1977,
- 3. Vermont Yankee Final Safety Analysis Report, Section 2.4.3 and Tabic 2.4.3.
- 4. NUREG-0782 Draft Environmental Impact Statement on 10CFR Part61 " licensing Requirements for Land Disposal of Radioactive Waste", USNRC, September, 1981.
- 5. IDLE, A computer program used to calculate receptor doses from routine liquid effluent-releases in accordance with Regulatory Guide 1.109, Rev 8, Yankee Atomic Electric Company, August, 1987.
6.. DIDOS-IV A computer program that calculates direct gamma doso rates from cylindrical sources, Yankee Atomic Electric Company, November, 1988.
.- 7 . RESRAD, ver. 4.3, USDOE, Methodology Description for Compliance with DOE Order 54005, Chapter IV, in press.
- 8. NUREG/CR-3332, Radiological Assessment, Chapter 4, U.S. Nuclear Regulatory j- _ Commission, September, 1983.
f l
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s Appendix 1 Vermont Yankee Site Plan 31
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- 6 3 YERMONT YANKEE HUCLEAR POWER STATION 1
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