BVY-91-113, Requests Approval of Proposed Procedures to Dispose,By Leaving in place,82 Mci of Total Activity,Principally Tritium,Contained in Fill Matl Located Under Existing Plant Structures & Bldgs,Per 10CFR20.302(a)
| ML20086D045 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee  |
| Issue date: | 11/18/1991 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-91-113, NUDOCS 9111250222 | |
| Download: ML20086D045 (23) | |
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.- VERMONT YANKEE NUCLEAR POWER CORPORATION
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BVY 91-113 Ferry Road, Brattleboro, VT 0$301-7002 ENGtNE ING OFFICE
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[04104 t/A 0174D I t'iB; 779 (J11 November 18, 1991 i
United States Nuclear Regulatory Commission l ATTH: Document Control Desk 1ashington, DC 20555 References _ 1,1 cense Number DPR-28 (Docket No. 50-271)
Det r Sir Fubject: Request to Dispose of Slightly Contaminated Soil in Accordance with 10CFR20.302(a)
The Code of Federal Regulations, Title 10, Section 20.302(a), allows Ifor i
applications to the Commission for approval of proposed alternate disposal methods of licensed materials not otherwise - authorized in the regulations.
Vermont Yankee Nuclear Power Corporation (Vermont Yankee) hereby requests NRC ,
approval of proposed procedures to dispose,-by leaving in place, radioactively contaminated soil and fill' material. j This application specifically requests approval to dispose of approximately 82 mC1 of total activity,_ principally Tritium, contained in fill material located under existing plant structures ard buildings.
A radiological ' evaluation, has been. completed and is included herein as Attachaent l'. Several pathways have been analyzed in accordance with guidance in Regulatory Guide 1.109. The predominant exposure pathway has been determined to be ground plane exposure. This assumes the material vill be exhumed 20 years 1
- in the future and spread to a 15'em. plov layer depth. l The total exposure to any individual, using a set of conservative ar.sumptions, .
including agricultural activities, is 1.1 millirem, whole body and 1.6 millirem, ,
organ.
The alternative to this exemption request is to excavate this material and either l treat it as radioactive vaste'and dispose of it in a licensed facility or request approval ~of another application of this type.- Excavation under existing 9111250222 911118
- DR ADOCK 0500 1
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. , VERMONT YANKEE NUCLE AR POWER CORPOR ATION 1
1 U.S. Nuclear Regulatory Cormission
-October 22, 1991 l Page 2 structures-and buildings is not possible during the term of plant operation.
Should you have any questions regarding this application, please contact this i office.
Very truly yours, Verrnont Yankee Nuclear Power Corporation d' ,
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Al' Varren P. Hurphy Senior Vice President. Operations cc t - USNRC Region 1 Administrator USNRC Resident Inspector - VYNPS USNRC Project Manager - VYHPS t
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u ATTACHMEliT 1 VERMONT YANKEE NUCLEAR POVER CORPORATION i
APPLICATION TO DISPOSE IN PLACE CONTAMINATED SOIL I
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l TABLE OF CONTENTS TOPIC PAGE NUMBER l Table of Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . i 1.0 Introduction . . . . . . .. . . . . . . . . . . . . . . . . . . . 1 i 2.0 Vaste Stream Description . . . . . . . . . . . . . . . . . . . .. 1
~2.1 Physical Properties . . . . . . . . . . . . . . . . . . . . . 1 2.2 Sampling Procedures .. . . . . . . . . . . . . . . . . . . . 2 2.3 Chem
- cal Properties .. . . . . . . . . . . . . . . . . . . . 2 2.4 Radiological Properties . . . . . . . . . . . . . . . . . . 3 2.5 Estimate of Total Activity . . . . . . . . . . . . . . . . . . 5 3.0 Description of Proposed Disposal Hethod . . . . . . . . . . . .. 9 4.0 Geology and Hydrology Considerations . . . . . . . . . . . . . . . 9 5.0 Radiological Considerations . . . . . . . . . . . . . . . . . . . . 10 5.1 Potential Off Site Exposure Pathways . . . . . . . . . . . . . 11 1 5.1.1 Approach to Analysis . . . . . . . . . . . . . . . . . 11 ,
5.1.2 Description of Scenario . . . . . . . . . . . . . . . 12 5.2 Potential On Site Exposure Pathvays . . . . . . . . . . . . . 12 5.2.1 Approach to Analysis . . . . . . . . . . . . . . . . . 13 6.0 Radiological-Impacts . . . . . . . . . . . . . . . . . . . . . . . . 14 6.1 Potential Off-Site Exposures . . . . . . . . . . . . . . . . . 14 .
6.1.1 Drinking Vater Ingestion . . . . . . . . . . . . . . . 14 6.1.2 Fish Ingestion Pathvay . . . . . . . . . . . . . . . . 15 6.1.4 Shoreline Direct Exposure . . . . . . . . . . . . . . 15 6.2 On Site Exposure Pathways . . . . . . . . . . . . . . . . . . 15 6.2.1 On Site Potable Vell . . . . . . . . . . . . . . . . . 15 6.2.2 Direct Ground Plane Exposure . . . . . . . . . . . . 15 6.2.3 Intruder Surface Related Exposure . . . . . . . . . . 16 7.0 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . ... 16 i ;
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1.0 Int roductinD Vermont Yankee Nuclear Power Corporation (Vermont Yankee) requests approval, 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), vas discovered early in 1991. It had led to contamination of soil beneatl.
the laboratory floor. It was found at the time of discovery that a portion of the - drain line between the sink and the floor had developed a leak. Upon detailed investigation it was determined that portiors of the buried drain line I had failed. This included an elbov connecting the vertical drain line to j horizontal piping, approximately 15 inches belov the concrete floor, allowing '
liquids poured dovn the sink to go into the soil below the laboratory floor rather than the intended 4,000 gallon- capacity Chemical Drain Tank (TK-19A).
- Vastes from this drain tank are processed for chemical as well as radionuclide content along with other plant liquid vastes, i
As soon as it was determined that the pipe had failed, the pipeline was isolated f rom the laboratory sink such that no further contamination could be released via this pathway.
The length of time this conditinn has existed is not known and cannot be determined exactly, however, for purpose of this submittal, an extended time ;
period of ten years is assun.ad in order to bound the potential impacts associated with the drain line leakage. It is estimated that 10 liters per week of reactor water have :been routinely discharged to this sink as a result of - chemistry sampling activities. Other non-radioactive liquids and chemicals vere also disposed of utilizing this sink. The results of radiological analyses of reactor vater samples vere revieved for recent years to calculate an estimate of the concentration and total activity that may have been discharged to this sink over time.- Samples of soil from grade to. bedrock vere obtained from a split-spoon boring through the Chemistry Laboratory floor. Samples were subsequently analyzed r for chemical and radionuclide distribttion and concentration.
The Chemistry Laboratory is located-in the lover level'of the of fice building at ,
the north end of the turbine building complex. During plant construction, tMr. .
- j. area vas excavated to bedrock at a depth of approximately 15 feet below the
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Chemistry Laboratory floor (El. 233' ). The area under the laboratory vas then L filled to its current grade and the concrete laboratory floor poured. Removal l of this contaminated material is impractical due to the fact that it is located underneath existing building structures. Furthermore, concentrations of .
l contaminants are very lov and pose no significant risk to the health and safety l of the public.
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- i. 2.0 Vaste Stream Description l .-
2.1 fhysical Properties I
- Discharge from the Chemistry Laboratory sink seeped directly into the structural
[ fill beneath the' building. floor slab. The contaminated material consists of
( - approximately a 15 foot thickness of structural fill placed during plant i
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a 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 existing foundations and on the bottorn by bedrock. If it is assumed the soil volume under the entire 150 foot length of buried pipe has become contaminated, the total volume as eltimated by projecting a cone shaped spread of activity downward and laterally away from the horizontal pipe, is about 58,500 cubic fact.
A compilation was made of the constituents used in the lab. In addition it was determined that a volume of distilled and tap water mixel with or separately disposed of in the same drain was on the order of 200 liters per day. A sample testing program, described belov, was then designed to assess the character of
, the chemicals added to the soil.
2.2 Sampling Procedures Samples of contaminated soil vere obtained through a hole cut into the laboratory j floor. Both-block samples from immediately beneath the floot, and split spoon soil boring samples at various depths vere taken. The boring vas done by ;
contract with Guild Drilling Co., Inc. Samples vere taken under controlled conditions, in conformance with vritten procedures and with iirect inspection by '
personnel familiar with such activities. Three samples andyzed for chernical contaminants included a sample (SS-2) frorn the most contamina.ed zone near the Cheroistry Laboratory floor surface, a sample (SS-3) f rom an intermediate depth and a sample (SS-5) f rom a vet zone, possibly the capillary fringe located at the ,
bedrock interface. Nine samples from the boring vere analyzed for radionuclide content and distribution as described in Section 2.4. .
2.3 Chemical ProDerties Samples of the soil vere analyzed for chemical constituents that vould be characterized as hazardous by the EPA. The results of the sample analysis did -
not indicate the presence of any hazardous chemical constituents.
4 Analysis were performed on soil sarnples f rom the bering (MV-1) for volatile -
organic compounds (VOC EPA Method 82_40), semi-volatile organic compounds (SVOC EPA Method 8270), 24 metals (EPA Method- 6010), 4 other metals, and ammonia, chloride, nitrate and pH. The sample.With tL- highest level of-radioactive ,
contamination, (SS-2), vas also analyzed -by tox1i.ity characterictic leaching procedure . (TCLP) including TCLP metals, TCLP semi-volatiles, and TCLP zero headspace extraction (ZHE) volatile organics. In addition an organic vapor meter .
(OVM) vas used to test samples as they were withdrawn from sampling equipment.
OVM analysis used to screen samples during sampling operations detected no organic vapors from any of the samples taken. Laboratory analyses showed neither TCLP ZHE volatile organics nor TCLP semi-volatiles to be present above' detection limits. . TCLP metals vere.found to be belov EPA regulatory _ limits. Volatile, semi-volatile'and metal . test results for all three samples are belov regulatory L limits. The ammonia, chloride, nitrate and Ph parameters are also vell vithin normal ranges. These tests support the conclusion made by ENSR (Ref.1) that the l
soil beneath the Chemistry Laboratory is Dat;-a RCRA characteristic hazardous ;
vaste.
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I 2.4 IMdiolovical Propertin f
A continuous 3" diameter split-spoon boring, (HV-1), was taken f rom the Chemistry [
Laboratory floor elevation down approximately 15 feet to bedrock. It was not ;
possible to take this core sample dirvctly adjacent to the pipe at the location ;
of the f ailed elbov between the trans,ition f rom vertical to horizontal pipe runs. t This was due to the presence of a concrete electrical duct bank buried just belov the horizontal run of the drein pipe irom the Chemistry Laboratory to the l chemical drain tank. The boring was thus located approximately 4 feet from the '
i vertical portion of the drain line inside the Chemistry Laboratory. At approximate 1 vertical foot intervals, three inch sampics of the removed soil vere retained and analyzed for radionuclide distribution and concentration. The ;
environmental Technical Specification lover limits of detection (LLD), as ,
specified in Technical Specifications, Table 4.9.3 for sediments, vere applied to the analyses. Co-60 and MN-54 vere the only two radionuclides of plant origin ;
- detected. l TABLE 1 t
SOIL BORING SAMPl.E RESULTS (Boring MV-1)
DEPTH BELOV TOP OF FLOOR CO-60 MH-54 (inches) . _ ,
(pCI N g. Vet) 13.5 _ JOB 5 25.5 383 339 ;
37.5 1131 914 85.5 296 12 104.5 351 1 109.5 221 7 l 121.5 166-- <HDA _
148.5 90 5 172.5 879 <MDA i
AVERAGE 425 183 ICENTRATION !
Block samples taken at the point immediately belov where the pipe penetrates the floor'had a Co-60 concentration that peaked at 1.1E+05 picocurie /kg. It should be noted that several short lived plant related radionuclides vert. 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 able to.be taken in close proximity to the vertical pipe, the measured values vould reflect the higher values measured in the block samples. '
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If this vere to be the case, it would be indicative that the activity has not ,
moved laterally to any great extent and that any estimate of total activity based !
upon one boring may result in an ove1 estimation of. total activity. '
Results of radiological analysis of soil bering samples indicate the presence of materials in the soil which could only have come from plant operation.
Concentrations are highest beneath the pipe (1.12SE+05 pC1/kg for Co-60), but :
considerably lover with depth (90 pC1/kg Co-60 at 12 it below the iloor). The distribution of radionuclides suggests that the movement of these radionuclides is, as expected, greatly restricted in the soil. Cobal'-60 vas the principle ;
radionuclide detected, and the only plant nuclide found belov a depth of 3.5 feet !
belov the Chemistry Laboratory floor. j vhile radionuclide 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) vas obtr.ined f rom-the 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: 1
- a. Higration of radionuclides does appear to be retarded by surption of !
ions onto scil _ particles. There vas some doubt about the degree to chich ,
this vould occur due to the use of drains for disposal of chemicals. :
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- b. The concentration of radiomlides in the bottom sample of the boring could be the result of the introduction of a relatively large quantity of activity put into the sink drain at some tixe in the past, or more likely, could also result-from "ponding" of activity at a lov point at the top bedrock, as a result of lover vertical vater velocity and longer contact '
time for ion v.xchange to take place, i
- c. Cobalt-60 (and ve assume Tritium) may have approached or crossed into the l ground vater regime and may be subject to present or future movement r ;
through ground water. It should be understood although, that no water has been found in the screened veli placed in the chemistry laboratory floor l after the sampling program was completed. This screened vell extends to the bedrock. This vould indicate there is no groundwater above the bedrock, t
2.5 Estimate of DIALArlivity i
For ana}ysis purposes, it is felt that a conservative estimate of the total activity released co the soil zone immediately below the laboratory floor could ,
be made by assuming 10 liters per vaek of reactor water was disposed of through the sink drain over a_ exterded period of time. It is assumed that 100%_of the asrociated activity put down the drain is released to the soil. A review of i reactor water analysis results for the period from 1987 through 1990, indicated *
= that the fif teen month period from May, 1988 through July, 1989 represented conservatively high values for reactor vater activity. Table 2 lists the monthly I concentrations of co-60, Mn-54, Cs-134 and Cs-137 measured in reactor water.
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TABLE 2 REACTOR VATER ANALYSIS
SUMMARY
DATA ,
DATE Co-60 Hn-54 Cs-134 Cs-137 (uCi/ml) (uC1/ml) (uC1/ml) (uC1/ml) 5/88 9.05E-05 5.23E-05 9.11E-06 1.49E-05 L
6/88 8.38E-05 5.45E-05 1.50E-05 8.08E-05 t 7/88 5.35E-05 3.96E-05 1.48E-05 1.50E-05 8/88 4.49E-05 3.45E-05 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-06 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 L 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 5.15E-06 7/89' 8.04E-05 4.39E-05 2.77E-06 3.28E-06 AVERACE 1.42E-04 8.31E-05 2.62E-05 2.98E-05 l
It is known from analyses of other vaste streams that nuclides important to 10CFR61, which are not gamma emitters, are also present. In order to account f or those radionuclides, whose half lives are of an order of 1 year or longer, a f representative teactor vater sample previously analyzed for Part 61 nuclides was reviewed for applicability to this rituation.
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 determined, for a conservative evaluation, that seven radionuclides, H-3, Mn-54, Fe-55, Co-60, Cs-134, Cs-137, and St-90 should be considered as present. These seven radionuclides represent 99.9% of the total reactor coolant activity present after 2.5 years. .
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2 TABLE 3 TYPICAL REACTOR VATER RADIONUCLIDES Nuclide llalf-lif e No Decay 2.5 Yr Decay (Years) (uCi/ml) (uC1/ml)
H-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 Hn-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 ,
i Cs-134 2.065 2.6E-05 1.1E-05 Cs-137- 30.17 3.0E-05 2.8E-05 Sr-90 28.6 6.9E-08 6.5E-08 Zr-95 0.175 3.9E-04 2.0E-08 Co-58 0.194 7.1E-05 9.4E-09 Fe-59 0.122 1.6E-04 1.1E-10 ,
Cr-51 0.076 1.7E 2.0E-14 The concentrations of radionuclides not measured in the monthly samples were based upon the relative abundance of radionuclides in the previously centioned laboratory analysis of a. reactor vater sample.
For. purposes of bounding the potential impact, it is assumed that 10 liters of ,
reactor Vater per.veck, at the " batch" values of Table 4, have been disposed in
' the sink over an arbitrarily long 10 year period, and that 100% of this vater has gone directly to the soil underlying the Chemistry Laboratory. Vith a constant i input and considering decay, it is mathematically possible to calculate a total li.ventory at any point in time. This analysis assumes a ten year period of weekly Table 4 " batch" releases. -Table 5 tabulates the postulated- total r inventory present at the end of an arbitrary 10 year period of veekly " batch" releases.
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(uC1/ml) (uCi)
H-3 2.UE-02 ?.0E+02 I
Mn-54 8.3E-05 8.3E-01 Fe-55 2.4E-04 2.4E+00 Co-60 1.4E-04 1.4E+00 Cs-134 2.6E-05 2.6E-01 Cs-137 3.0E-05 3.0E-01
_ _ Sr-90 6.9E-08 6.9E-04 _
- Activity in a 10 liter " batch" t
TABLE 5 ACTIVITY BUILDUP BELOV THE CHEM LAB FLOOR VITH TIME Radionuclide Half-life Q, Q*
(Yearc) (uti/ Batch) (Total uC1)
H-3 12.2 2.0E+02 8.0E+04 Hn-54 0.85476 8.3E-01 5.4E+01
,Fe-55 2.7 2.4E+00 4.4E+02 4
Co-60 5.272 1.4E+00 4.1E+02 Cs-134 2.065 2.6E-01 3.9E+01 Cs-137 30.17 3.0E-01 1.4E+02 i Sr-90 28.6 6.9E 04 3.2E-01 l
l Total Activity 2.?E+02 8.1E+04 l
Total activity present after 10. yrs of veekly " batch" releases l
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3.0 pescription of Proposed Disposal Method ,
It is proposed to dispose of the activity by leaving it in place where it currently resides. By terminating the release of liquids into the failed drain ,
line, there is no significant driving force to cause any further movement of the }
activity nov in the soil below the Chemistry Laboratory floor any deeper toward the ground water regime. The total quantity of activity is sufficiently small
, that it does not currently present a direct radiation exposure hazard to the ,
l Chemistry Laboratory. To remove the material vould, however, require a major !
excavation effort under the laboratory floor and in proximity to the reactor building foundation, and other critical structures, as nell as exposure to the vorkers performing the excavation. The direct exposure as well as potential airborns exposure to current vorkers performing remediation vould be f ar greater than the potential for exposure to a future population. In fact, there is no practical vay for this material to be removed from under the plant at this time. ,
4.0 Geolony and Hydrology Considerations Natural soils at the site vere 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-vith some silt and minor gravel. Natural '
soils remain around the periphery of the site. These natural soils consist of i a loose silty fine-grained sand 5 to 15 f t thick underlain by medium dense, glacio-fluvial.. silty fine-grained sand 10 to 20 f t thick. Vhere bedrock surf ace elevation is below + 220 f t (ms1) there also exists deposits of varied fine sand and silt with a fev thin clay layers. Thickness of these varied deposits ranges up to-12 ft. They are typically underlain by a few feet of sand and gravel.
Bedrock under these soils is hard, f resh massive gneiss. The bedrock surface is undulatory, varying in elevation from about +190 f t to +230 f t (msl), in the vicinity of the major plant structures. The bedrock surface rises to elevations of +250 ft to the vest side of the plant site, and drops well belov +200 ft 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" concrete)-is +248'6".
Ground vater depth in the vicinity of plant structures is about +230 f t. Average elevation of the Connecticut River is +220 ft. The building housing the Chemistry Laboratory is about 300 f t from the river. Hydraulic gradient is.thus rather high at 0.05 ft/ft. Ground vater flov rates have been estimated at about i 32 feet / year, thrcmgh natural soils, and may be a factor of two or higher through the fill materials. For this reason, only 2.5 years is assumed for travel time to the river.
Bedrock vas encountered in the soil boring MV-1 at an elevation of about +233 f t. i
- The bottom 1.5 to 2 feet of soil encountered in the boring just above the bedrock surf ace -was damp and a vell screen vas- installed in the hole to attempt to measure water levels upon completion of sampling. However, since the vell installation no vater has accumulated in the hole. The damp soil encountered i thus may have been a capillary fringe, but more likely vas the remnants of water l; leaked from the subject pipe. Thus the natural ground water surface appears to l 9 l
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be belov the bedrock surface beneath the Chemistry Laboratory. Original site dravings show ground vater elevation in natural soils to be at about elevation
+235 in this area. The present ground water table may be lover than when original soils vere present due to the somewhat lover permeability of those soils compared with the structural fill and the possible alteration of ground vater flow regime due the construction of building foundations.
The alteration of ground vater due to floods was considered and dismissed as insignificant. The 100-year flood on the Connecticut River reaches an elevation of only4228, just belov the typical current level of ground water. The 500-year flood reaches an elevation of only 4 feet higher at +232, but has a very short duration of only a iev hours.
Ground water flov across the entire site is directly toward the Connecticut River (Vernon Pond). Two possible paths to the river appear to exist for ground water in the vicinity of the Chemistry Laboratory. It either flovs northeast following the path of a bedrock depression and former gully (filled in during "
cort truction), or it flows east, perhaps intercep ing fill along the 126 inch dic.eter circulating vater intake pipe trinch.
Fu tr potable water vells exist on site. All of these wells are either up-gradient or decidedly away Irom any potential ground vater path from the Chemistry Laboratory to the Connecticut River.
In general, bedrock permeability is very lov. Studies have identified photo-lineaments which appear to.be some long, narrov fracture zones on the site.
However, none of these zones are located where they might influence flow of ground vater 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.
5.0 Radiological Considerations Scenarios that have the potential for radiological impacts to mertbers of the -
public have been postulated for the purpose of determining- maximum possible doses. One scenario assumes the contamination migrates off site to Vernon Pond on the Connecticut River where it becomes the source term for subsequent direct
. uptake : as drinking vater, indirect uptake after concentration in fish and subsequent consumption hy man, use of the water for crop irrigation, and direct exposure from standing on the shoreline of the pond. A second scenario assumes the material remains in place until the plant is decommissioned and control over
.the site is no longer maintained. At that time an intruder arrives on site, drllls a vell-into the soil containing the activity, and/or exhumes the material and spreads the activity over the ground, grows crops, feeds a dairy cow,'and supports a f amily on the site. These scenarios are mutually exclusive, i.e. , one or the.other may occur, but both cannot occur. Neither can the intruder be exposed via the drinking vater pathvay with the crop production / ingestion pathway simultaneously. The radiological evaluation has considered all scenarios and--
assumes the higher radiologica" impact case takes place.
Another scenario considered is that the radioactivity reaches the on site potable vell used by'the plant, during the current period of plant operation. This 10 1
I potential exposure pathway does not include members of the public but is restricted to plant ceployees. The plant environmental monitoring program is designed to detect any increase in activity in environmental media due te plant '
operations. The principle on site potable drinking vater vell is included in this program. To date, no plant related radioactivity has been determined to be present in any well vater sample. Nonetheless, a potential exposure is i calculated for this pathvay.
5.1 Potential Off Site Extiosure Pathvavs .
In this scenario it is assumed the activity moves at the rate of ground water and arrives at Vernon Pond. Vith a distance of approximately 300 f t and an estimated groundvater velocity of 32 ft/yr, it is expected to take 9+ years to arrive at ,
the pond. Because of the uncertainty over the possible start time of any migration, it is assumed that 100% of the estimated activity in each veekly
" batch" arrives at the river 2.5 years after its release. It is assumed a ,
continuous release exists and the annual release consists of the sum of 52 veekly -
" batch" releases. Ef fects of retardation by the soil are neglected. Table 6 presents the activity assumed to reach the river on an annual basis. It is ;
assumed this release rate continues for 10 years. '
'5.1.1 Approach to Analysis i The methods described in Regulatory Guide 1.109 (Ref. 2) are generally applicable .
to analysis of the radiological impact of of f site releases. The dose model used for estimation of_ total exposure is IDLE (Ref. 5) and is based upon Regulatory Guide 1.109. The entire inventory of activity is assumed to be continuously released via a liquid effluent pathway to the river. The release flow rate is assumed to be small and the activity remains undiluted as it moves to the river.
Credit for 2.5. years decay is taken.
=
f I
l 11 h- v-~
r v e, yAn,,we,,-,--,<m w----q-w-ww ,we-,wn -
w- -,n.w g-- a e .- .m-a e-,e-,,v_ .,.-psu,e , , m e -, as a vo w -..mmm,-m,,r-,+ww.m- w w , m n.w w n,,,m-,w,, +
- - - .- . . -- . - - . - . - - . . . - ~ . _ . - - - - - ~ .. . . . - -
TABLE 6 ANNUAL ACTIVITY RELEASE ASSUMING 2.5 YEARS OF DECAY )
]
Radionuclide Half-life Q, Qa
- Annual Release i (Years) (uCi/ Batch)- (Total uC1) (Total uCi) -
H-3 12.2 2.OE402 1.8E402 9.1E403 Mn-54 0.85476 8.3E-01 1.1E-01 5.7E+00 Fe-55 2.7 2.4E+00 1.2E+00 6.5E+01 Co-oO 5.272 1.4 WOO 1.0E+00_ 5. 3 E,+ 0 i Cs-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 ) i
) i Sr 28.6 6.9E-04 6.5E-04 3.4E-02 j
. Veckly batch activity released to river, after 2.5 year decay.
' Annual-release, 52 times the weekly batch release.
i 5.1.2 .Descrirtion of Scenarin ,
The scenario asstunes 'an essentially constant release rate over a ten year period, such that the activities listed in Table 6 reach Vernon Pond annually. Dilution '
is asstuned in Connecticut River vater floving by the plant. The FSAR (Ref. 3), +
states the river flow is typically 10,000 cfs, with no less than 1,200 cis during the dry season. For purpose of this evaluation, a conservatively lov value of 100 cfs is assumed for the entire year, as the dilution flow. ,
Pathways considered in this evaluation include constaption of fish, use of the wate r .- to irrigate- leafy and stored vegetables, and- sediment irradiation to -i
- recreational. users of the shoreline. Regulatory Guide 1.109 (Ref. 2) '
bloaccumulation 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 f rom residual ,
activity from the previous nine years of releases.
$ ::- 5.2 Eplential On Site Exposure._Iathy.ays '
Another hypothetical ~ scenario is that activt :y reaches the on site potable velli -r with subsequent consumption of the water by plant employees. Monitoring of the vater supply vill ensure this vill not constitute an exposure pathway. .
12
.E k
w h ,w , , , , , - ~ ~ ,,-e,,,,,-w-~~,.-,%w...-.%,, ,jp-w., s-,- vm ,--,,g. v--,-y,- a 4 . - - ,,,,-.,.,_m ,%,...,-y.p. ., , ,,w,, ,%se,. -.,r,,,--.- , - . - _ , p , _, ,
.- - _ _ . _ - ..- -. - - _ - _ _ . _ . ~ _ - - ~ _ _ - _ - - . _ _ _ _ .
The Draf t Environmental Impact Statement for 10CFR61 (Ref.4) also considered several potential exposure pathways in its radiological analysis, among them was an intruder settling on a site once institutional control was lost.
The scenario considered for this application, to demonstrate the extreme case and the insignificsnce of the tutal exposure, consists of an intruder settling on the plant site after termination of the plant license and decommirsioning and dismantling of all buildings. It is assumed this intruder arrives 20 years from nov and either sinks a well into an aquifer containing the residual activity, or uneatths all of the activity present at that time, spreads it about, plants and harvests crops, and raises a milk cow on the land. (These two scenarios are mutually exclusive). !
5.2.I uproach to AnalyMA l l
In general, the dose model used for estimation the total expose;e is from j 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 suf ficiently large area to support the groving 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 ,
sq. meters.
4 Doses vere calculated for the intruder scenario in which food crops, grazing ,
requirements for a milk cow, and inhalation of recuspended material were -
considered, for the whole body and seven organs to each of four age groupsi
, infants, children, teens, and aduits, 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 i 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.G.1.109. One is i the direct ground plane from a finite size source and the other is a well vater ingestion pathvay in which the uctivity is assumed to be below the ground level.-
The direct ground olane ex;osure component is determined by the DIDOS computer program (Rcf. 6), which calculates doses from a cylindrical source of stated density, and is apphable to this assumed scenario consisting of a ground plane
- source. The vMie body ground plane direct exposure fraction, af ter exhumation ,
is calcukted assuming the decayed . activity is exhumed and spread in a layer equivalent to the plov' depth (15 ca.) used in Reg. Guide 1.109. This equates to a circular area of 59 meters radius, based upon the previously estimted $8,500 ,
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 '
For the on . site drinking vell vater scenarios, the model and assumptions described in NUREC/CRJS12 (Ref.7) are used, with the activity at the time of the i asstuned scenario residing in the soil material. The model described in Reference
- 7 uses conservative values for nuclide partition coef ficients, the infiltration rate, the assumed thickness of the soil layer, and the soil porosity to develop act.tvity to dose factors fo> the nuclides of concern. The model assumes a 13 k
f t + + .v w ww e c enn. --o, em-.-.m#,.r.-...,--.m +-,e.-- -w,-,--
- .. . . ~ . . -._ ..
dilution volume of 91,250' liters, the voluae of vater used by man in one year.
The model vater consummation rate is 730 1/yr, which is consistent with Reg.
Guide 1.109.-
The activity in Table 7 is that activity remaining r f ter 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.
TABLE 7 ACTIVITY AFTER 10 YEARE OF VEEKLY RELEASES, FOLLOVLD BY 20 YEARS OF DECAY hadionuclide Half-life Q, Q,
- Qa "
__ , (Years) (uCi/ Batch) (Total uC1) (Total uCi)
H-3 12.2 2.0E+02 8.0E+04 2.6E+04 Mn-54 0.85476 8.3E-01 5.4E+01 4.9E-06 Fe-55 2.7 2.4E+00 4.4E+02 2.6E+00 Co-ob 5.272 1.4E+03 4.lE+02 3.0E+01 Cs-134 2.065 2.6E-01 3.9E+01 4.8E-02
_ _Cs-137 30. 3.0E-01 1.4E+02 8.7E+01 Sr.10 28. _
6.9E-04 3,2E-01 2.0E-01 Total activity prest Ler 10 yrs of weekly " batch" releases
' That activity af ter a "O year decay period 6.0 Radio.lgnical Impacts 6.1 Potential Off-Site Exnosures The maximum radiological impact due to the smn of of f site pathways is 9.8E-04
-MhEM to an adult whole body, and 1.5E-03 MREM child organ dose (liver). These exposures are subdivided into the following individual pathways.
6.1.1 Drinking Vater Ingestion Consumption of drinking vater from contamination that has traveled undiminished though the soil, except for a 2.5 year decay during travel, diluted in the minimum flow of the Connecticut River, and consumed at the rates specified in Reg. Guide 1.109 (Ref.2) for the four age groups (infant, child, teen, and adult), results in a maximum whole body dose to an adult f rom drinking water 14
- n v .
\ .
Ingestion of 2.5E-05 MREM. The maximum organ dose is to an inf ant liver of 6.3E-05 MREM. The methodology used for analysis is that described in Regulatory Guide 1.109 (Ref.2).
6.1.2 Fish Ingestion Pathvay Bioaccumulation f actors and consumption rates f rom Reg. Guide 1.109 (Ref.2) are applied to fish ingestion. The maximum whole body dose 1: an adult and is estimated to be 8.3E-04 MREM. The maximum organ dose is to a teen liver and is 1.2E-03 MREM.
6.1.3 Irrigation Exposure Pathvar The diluted vater 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 maximum whole body annual dose is to a child and is estimated to be 1.2E-04 MREM. The maximum organ dose is to a child liver and is 4.0E-04 MREM.
6.1.4 Shnr111RR_.
t Direct h n.osure 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 fram standing on the shoreline.
6.2 On Site Exposure Pathvavs 6.2.1 Qn Site Potable Well For the on site well during plant operation (next 2s years) it is assumed that -
the inventory remaining after 10 years of releares, remains in the soil and is transferred, using the model described in Reference 7, to that volume of water
-used by man in one year for all domestic purposes (91,250 liters; and is constmed at a rate of 730 liters / year.
Using the data from Table 5 (converted to pico-curies) and tha Total Effective Dose Equivalents (TEDE) from Ref. 7, the total Whole Body Jo r to an individual f rom the on site vell is calculated to be 1.6E-01 MREM, esser,t ially all due to Tritium. An intruder arriving 20 years in tr. future will find a lesser inventory due to decay. The resulting doce vill t herefore, not exceed the g 1.6E-01 MEEM calculated with no decay.
6.2.2 Diragt Ground Plane E2P9fdRS At yt c r 20 in the future (Table 7 activity), exhumation of the 58,500 ft 3 (1.657E+03 M ) of material and spraading in a layer equivalent to the plov depth 3
(15 cm), results in an continuous annual exposure of 2.7E-01 HREM, as calculated 15 l
> __ _ .._m ._ _ _ _ . _ _ _ _ . . _ _ - _ _ _ _ _ . _ _ . . _ _ _ _ _ _ . .
. j by DIDOS, a small fraction of exposure due to natural background.
6.2.3 Intruder Surface Related Exposure Using the methodology of Reg. Guide 1.109 (Ref.2), and the activities from Table
' 7,~ results. in the maximum calculated pathway exposures as listed in Table 8. The assumptions 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 milk from a cow whose 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 radiological impact might be, 1ABLE 8 INTRUDER EXPOSURES, BY PATHVAYS Max Uhole Body Dose Max Organ Dose .
Pathway Child-Lung (MREM) (HREM)
Inhalation 1.1E-01 6.5E-01
-(resuspension)
Stored Vegetables 4.9E-01 4.8E-01 Leafy Vegetables 2.5E-02 2.4E-02 Cow Milk 1.6E-01 1.5E-01 Direct Ground plane 2.7E-01 2.7E-01 (from 6.2.2 above)
Totals 1.1E+00 1.6E+00 7.0 Conclusions The total activity calculated to have been released over a ten year period and remaining nov, is of the order of 81.3 millicuries, 80 millicuries of which is calculated to be -Tritium, based upon its concentration in reactor water.
Dilution with the estimated 200 liters-per day of other non-radioactive liquids discharged through this ' sink over the same. time period, results Lin a - tritium concentration, discounting any decay or further dilution, of the order of 1.0E-03 uCi/ml.. The 10CFR20 Appendix B, Table II-allovatle 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 specified in 10CFR20.
16
TABLE 9
SUMMARY
OF EXPOSURES OFF-SITE PATHVAYS VB (HREM) ORGAN [HREH L Drinking Vater Ingestion 2.5E-05 6.3E-05 Fish Ingestion 8.3E-04 1.2E-03 '
Irrigation Exposure Pathvay 1.2E-04 4.0E-04 Shoreline Direct Exposure 2.2E-05 -
ON-SITE PATHVAYS _
Vell Vater Ingestion 1.6E-01 -
Dirs:t Ground Plane 2.7E-01 -
Inhalation (Resuspension) 1.1E-01 6.5E-01 _
Stored Vegetables 4.9E-01 4.8E-01 Leafy Vegetables 2.5E-02 2.4E-02 Cov Milk 1.6E-01 1.5E-01 The alternative to in-place disposal is exhumation of this material and possible j disposal as radioactive vaste, or the srbject of an additional application for disposal by alterr. ate means, at a great increase in cost with no associated significant increase in benefit. The material, being located under plant structures, vould be extremely difficult to safely remove without major disruptions to a large portion of the plant.
1 l In the past the NRC staff has considered the potential effects on the environment i of licensed material from operation of nuclear power plants, and in the l evaluation of radiological impacts, generally conclude that operation of plants l vill contribute only a small increment of the radiation dose that persons living l .in the area normally receive from background radiation, and fluctuations of the natural background dose may be expected to exceed the small dose increment contributed by the operation of the power plant.
l l Since the disposal herein proposed involves licensed material containing a small l fraction of the radioactivity already considered acceptable under the Radiological Ef fluent 'lechnical Specifications (RETS), and involves pathvays much j less - significant, and in a radiochemical form much less mobile than those considered in the RETS, it is concluded that this application has an
- _ insignificant radiological impact.
17
In reality it is not expected that loss of control over the Vermont Yankee site vill occur in the near term time frame, however, even should an intruder settle atop the disposed material, the radiological consequences vould remain minimal.
Vermont Yankee, therefore requests approval from the commission to dispose of an existing quantity of radioactively cont aminated material containing an estimated total of 82 mci, (80 mci of which is tritium), by leaving the material in place in its current location under the f1r.or of the pl. ant Chemistry Laboratory, M
18
... ---_ . -- . _ - _, - . ~ . - - .
8.0 References l 1
- 1. DISR Consulting and Engineering, Environmental Site Assessment of Chemical Laboratory Subsurface, Vermont Yankee Nuclear Power Corp., Vernon, VT.
(Draft), April 1991.
- 2. USNRC Regulatory Guide 1.109, Calculation of Annual Dose to Han 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 Table 2.4.3.
- 4. NUREG-0782 Draf t Environmental Impact Statement on 10CFR Part61 " Licensing Requirements for Land Disposal of Radioactive Vaste", 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 dose rates from
-cylindrical-sources, Yankee Atomic Electric Company, November, 1988.
- 7. NUREG/CR-5512 (PNL-7212) Residual Radioactive Contamination from
~ Decommissioning, V.E. Kennedy, Jr. & R.A. Peloquin, Pacific NU Lab.,
January, 1990 (Draft),
p 19 l
l-
-