ML20126A619
| ML20126A619 | |
| Person / Time | |
|---|---|
| Site: | 05000054, 07000687 |
| Issue date: | 12/15/1992 |
| From: | Mcgovern J CINTICHEM, INC. |
| To: | Dennise Orlando NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20126A622 | List: |
| References | |
| NUDOCS 9212210148 | |
| Download: ML20126A619 (31) | |
Text
{{#Wiki_filter:._ _._ m 3 CINTICHEM, INC. P.O DOX 01G TUXEDO, NEW YORK 10907 (9141) 351 2131 December 15, 1992 : Mr. Dominick Orlando U. S . Nuclear Regulatory Commission Division of Low Level Waste Management > and Decommissioning, NMSS Decommissioning and Regulatory Issues Branch t Washington, D.C. 20555
Dear Mr. Orlando:
References (a) USNRC Letter, D. Orlando (Docket 50-54, 70-687) , dated December 4, 1992 The referenced letter requested additional information in support of the Cintichem, Inc. proposed residual soil contamination acceptance criteria that were included in our initial submission dated July 15, 1992 and recently modified in our submission dated October 22, 1992. This information is enclosed and it is presented in the same order as the questions posed in the referenced letter. Very truly yours, , fy,!k m D. ./McGove rn President / Plant Manager JJMcG/bjc Enclosures cc: A. Dorozynski T. Dragoun A. Gartner G. Kasik P. . Merges T. Michaels B. Youngberg Director, Technical Development Programs, State of NY Energy Office 17 }) 9212210148 921215 180001 ' PDR P-ADOCK 05000054
-JJM/203.92B PDR 3
)ls
)) g.
b
i t ! el Excavation soil on the Cintichem site is sampled and analyzed as follows. Sampling frequency in dependent on the anticipated probability of positive contamination in the soil- for the HUT excavation and similar areas where clean. That is, soils that are being excavated to uncover expected contaminated soil has and will be sampled by collecting two aliquots of soil f rom each dump truck load (approximately 7 cu. yds) of soil dumped into a l i holding area. These aliquots may be composited with up to 9 other dump truck loads for that day or part of a day. This has : been the procedure for the 5,400 cu yds excavated above the roof of the pump room and of the HUT. 90 separ ate assays for - gamma emitting isotopes and 13 composites for the 26 feet of excavation below grade were accumulated for this material. Surface or subsurface soil in proximity of known or expected contamination such as the hot cell exhaust duct area, gamma pit / canal area and subsurface HUT area have been or will be placed into 55 gallon drums or steel boxes. An aliquot from the container being filled from each 7 - 8 cf is composited with up to 11 other samples to get a composite cample representing approximately 90 - 100 cu yds (84 cu ft = 1 box) from one area. This sample is submitted for on site _ gamma analysis for minimum of 2 hour counts according to procedure HP-M-55 (attached). Composites for beta and alpha emitting isotopes will be taken from these samples. To date, 39 gamma assays have been run for the approximately 121.68 cu yds of soil excavated next to the HUT. Each composite sample consists of about _ 6 - 8 pounds of soil. Samples are logged in in the environmental monitoting department through a chain of custody format. Approximately 4 - 5 pounds of soil is prepared for drying in our soil prep. lab. Large hits of rocks and vegetation are removed and the remainder is placed into a drying pan. After the soil has been stirred and air dried or. incubator-dried (60'C) until it appears dry, it is heated at 100*C for a minimum of 2 hours. While this procedure slightly differs from NUREG/CR 5849, the results are equivalent. The-vast majority of the soil sampled requires only this amount of time t-dry since it is sandy backfill or subsurface, non-loamy material. Soils are then sieved and prepped into a 250 ml geometry (approximately 400 g) for gamma analysis at Cintichem. Assay. results are reviewed by senior staff and concentrations- are compared to proposed criteria concentrations to determine the i total sum of fractions of criteria. l- An aliquot. of -the composite original sampl e ' representing a container (or composites representing more than one container of clean overburden material or any material f rom the same general , source with similar gamma spectrographic characteristics (in this case similar is defined as all samples f rom' a source having the same mix and that-the amounts of radionuclides among samples are within a factor of two of each other)) will be used for alpha.and JJM/193.92B Page_1
i beta emitter isotope assay. These are sent to an outside vendor (e.g. Teledyne or Core Labc). Pe55, N163, Sr90 concentrations are determined by radiation chemistry assay, tritium by liquid scintillation assay and Pu238, Pu239, Pu240, Pu241, Cm242, Cm244 and uranium according to LA-1721 Radiochemical Procedures of Los Alamos Scientific Laboratory, September 1967. Other generic procedures that are currently being used by Teledyne are being requested and will be sent under separate cover. Records of each analysis, both for gamma emitters and alpha and beta emitters are ffled together with location and volume of sampled material. Thess will be summed to create a total site inventory for each category of soil for each locations surface and subst.rf ace. Further details on soil disposition are in - answer Fa. Quality assurance of on site liPGe samples are governed by. procedures ll P-M- 3 7, Routine Source Check for llPGe Counting Systems, IIP-M-43, Manual Control Charting for Standard and Blank Counts in Environmental Lab liPGe Detectors and ilP-M-51 Routine QA Blanks for ilPGe Counting Systems (all attached). These initiate the frequency and procedure for counting standards and blanks, the plotting of this data on control charts and procedures to follow when data is out of control. JJM/193.92B Page 2 1
l f l l 42 Soil remediation is planned to occur at nine discrete work areas on the Cintichem site. Three of these areas have very low levels of surface soil contamination. These areas are the waste storage building (WSB) yard, retention pond area, and the stack area. The other six areas are generally subsurface soil contamination areas which are associated with structures or systems that comprise the reactor and hot lab facilities. These subsurface soil areas are, the soil adjacent to the hold up tank (HUT) area, the soil under the reactor water storage tank, the soil in the area of the gamma pit / canal, the soil surrounding the hot cell underground air exhaust system, the soil surrounding the 5000 gallon mall tanks (5K tanks) and soil surrounding yard piping - that provides connects between the SK tanks, reactor building, hot lab building and building 4. The following describes the currently planned (or executed) remediation that will occur at each of these areas. Waste Storage Building Yard The area with known soit contaminatien is located behind the waste storage building (NortL side). The bulk of the affected area, which requires enediation, has a surface area of about 300 to 400 ft2 a.d is about 0.5 feet deep. Soil contamination in tn- area is principally comI>o sed of Csl37, with traces if Csl34, Co60 and Sr90. Contamination levels thar nave been found range from 0.5 to 235 pCi/gm with an average level of 43 pCi/gm. Soil remediation in this area 1.111 consist of excavating the affected soil manually and/or by - inachine Generally the entire affected layer (about 200 ftb) will be removed until the surface soil concentration criteria is met, the gamma dose rate resulting from any residual contamination is less than 5 uR/hr at one meter and any residual soil contamination (which meets the concentration criteria) be no more than six inches thick. After termination of the facility's NRC/NYDOL licenses, the area may or may not be re-graded. Retention Pond Area The areas with known soil contamination are spotty, but are generally located at the S-5 discharge pipe outfall and at a drainage trench about 100 ft South-east of the outfall. Depth of soil contamination generally ranges between 0 and 12 inches. The contaminated outfall area that requires remediation has an area of about 450 ftZ. JJM/193.928 Page 3 _ - - - - - - - - - - - - - - - - - " - - - " - - - " ' - " - - - - " - - - ^ ' - " - - - - - - - ~ ~ - - ~ ^ - - ~ - --
_ ~ . - . _ . . . _ ._ . _ _ _ . _ _ _ . . _ - . - . . _ _ _ _ . . _ . _ _ _ _ _ _ _ . _ . . l l h The drainage trench has an area of about 100 ft2 that requires remediation. Contaminants are principally comprised of Cs137, Co60, Cel44, Sr90, Nb95, Cs134, Rul06 and Zr95. A hot spot contamination levels up to 60 pCi/gm have been found with average levels being less than 10 pCi/gm. Soil remediation in the retention pond area- will l consist of removing about 300 ft3 of soil. After completion r the soil removal, the areas will be allowed to revert back to nature, with the possible need for some slight regrading near the S-5 outfall to-prevent pooling of surface run-off near an adjacent electrical service pit. Exhaust Stack Area _ The exhaust stack is located approximately 400 feet West of the hot lab building atop the 170 foot high cliff behind the building. Soil remediation is currently not planned for this area as it meets the proposed surface contamination criteria. Only Cs137 has been detected at levels generally . less than 0.5 pCi/gm which is in the range that would be expected for-global fallout. It is possible that some soi1= remediation could be required at - the base of the exhaust stack after the stack has been removed. Hold Up Tank The- hold ' up tank- (HUT) is located outside at'the South-east corner of the reactor building, under approximately 35 feet of soil overburden.. The soil above this _ tank has- been excavated. Approximately 150,000 - f t3 of soil- overburden- had to be removed to expose the top? of the tank. . No residual radioactive material has been found in this overburden. Recently, 3 contaminated soil has been found and -is being removed f rom along the sides of the tank. This contaminated layer started about . 4 feet down f rom the top of the tank. This soil so- far has- been found to be-- contaminated with the following peak concentrations: Co60 480 pCi/gm Zr95 -3 pCi/gm Ag108m 28 pCi/gm Ag110m 2 pCi/gm S b125_- 10 pCi/gm Cs134 89 pCi/gm l , Cs137 240 pei/gm Cel44 5 pCi/gm Eu152: 7 pCi/gm
-JJM/193.92B. Page 4
- g. , Aeg
- e p - grPI' -y+39 w -pev--"- w7 +yyM,-r-t-yT--i-g'* '
r -f y t W ps - e="
-aef r- --
t l s t The following radionuclides are estimated by scaling (pending laboratory results): N163- 12 pC1/gm Fe55 480 pCi/gm ! Sr90 961 pCi/gm , i 2 The HUT area soil is being characterized on an ongoing oasis as the excavation process proceeds.- During this process soll will be sorted as requiring disposal or meeting subsurface / surface soil criteria and retained for future backfill. Direct gamma exposure rates above this soil is approximately 2 mrem /hr. It is currently estimated that 2000 - 3000 ft3 of i contaminated soil will require removal as radioactive l' waste. Af ter remediation is _ complete, and concurrence is received from NRC/NYDOL to do so, the excavation will be filled with clean building rubble and/or soil meeting the subsurface acceptance criteria and covered with a meter of clean soil, and graded and seeded. Storage Tank Soil The reactor water storage ' tank is located about 100 , feet South of the reactor building. The tank has a 600 ' ft2 base. The presence of soil contamination under this tank is unknown at this time. After the. tank has been removed soil under it-will be characterize _d. If found, it would be removed by manual or mechanized excavation methods. Depending upon the depth of contamination (if found) - the subsurf ace or the surf ace soil' criteria could apply to this area. Tne_ area may or may not require backfilling or regrading efter L remediation. L - Underground Exhaust System , i The underground air exhaust system consists of an underground ceramic and_ concrete duct system and a semi-subsurf ace ' filter bank that is ventilated to the " five hot cells. This system is- located in the hot _ laboratory _ building. Remediation will- consist' of removal of the exhaust duct and ' filter bank, and_ any soil .that may have become contaminated as a result of leaks from this system.
-Soil contamination has- been identifi ed where soil- -4 samples could be obtained. However, che majority of potentially _ contaminated soil ' cannot be accessed for ,
characterization - until the _ concrete floor, duct .or structures, have ' been removed. - Soil characterization-will be'- carried out on an "as you .go" . basis as excavation work progresses. During this-process soil .
.JJM/193.92B Page 5 i
excavated to facilitate removal of systems or structures will be sorted as requiring disposal as' . radioactive waste or as meeting subsurf ace or surface soil criteria. Excavated soil found to meet acceptance criteria will be retained for subsurface and/or surface t backf illing . Additional soil will be removed, as ' necessary, to meet applicable soil criteria. Portions of the underground exhaust duct are not deep-enough to allow application of subsurface excavation criteria, therefore, those areas will be subject to surf ace soil criteria. j Soil contaminants are expected to principally be Cs137, Sr90 and Cel44 in about equal proportions with peak contaminations possibly reaching- the 10,000 pCi/gm i level. It is currently estimated that about 17,000 ft3 of soil from this area will require remediation. After : soil remediation and building demolition, _and concurrence from NRC/NYDOL to do so, the excavated areas will be backfilled with clean building rubble -r and/or soil that meets the subsurface or surface criteria as appropriate for the depth. Gamma Pit / Canal Area The gamma pit and canal structure is located between the reactor pool and the hot cells. This structure was , constructed within a trench that was excavated into the bedrock and backfilled with sand / soil and/or concrete fill. Approximately 8000 ft3 of soil was estimated as requiring remediation. This estimate was based upon the pre-decommissioning plan characterization performed in 1990. At that time, the canal and gamma pit had_to be maintained in usable condition . so the number of available soil samples were limited. However, as part-of recent decommissioning activities in the canal / gamma '; pit, 12 additional _ core holes- were - drilled through the . walls to characterize the radiological conditior of the exterior concrete surfaces and-surrounding soil. The exterior concrete surfaces were found to be generally f ree of surf ace -contamination except1 near a construction joint / crack. Three of the core holes were-found _w ith soil- behind - them and soil samples were - rettieved. Traecs of Cs137, Co60,- Ag108m and Agl10m were detected in all .three samples. . Howeve r, the concentrations found meet both the proposed- subsurf ace : and surface soil- criteria, with the_ _ highest-concentration' being r _ Csl37 - -0.2 pCi/gm, .Co60 - 0.4 pCi/gm, Ag108m'- 0.08 pCi/gm and _ Agl10m : - 0.2 pCi/gm. This may. indicate' that soil contamination is- less extensive than originally estimated.- JJM/193.92B Page 6
-i .z .-- , . - g mn9'qw--M 'h w y u nd' t'- H e- 'w-- --#-gt--We e & T--f T
'+-'t--a p g1 py wevig + -pw v'+-'e e..,tyrW4 g slp w-"~'w--'--*vVMyg--1pri'-w'y'Ty' Gy 7 T 9}' ' -s-ar 19- y
As the canal / gamma pit structure- is removed, surrounding soil must be removed and will be characterized and sorted, as requiring disposal or to be retained for future use as backfill material. After the canal / gamma pit structures are completely removed, additional soil will' be removed as is required to meet - release criteria. After completion of remedial' activities, the subsurface portions of the excavation will be packfilled with concrete rubble and/or soil that meets the surface and/or subsurface soil criteria as rppropriate and covered wi'h at least a meter of clean soil, graded and seeded. SK Tanks The SK tanks are located about 50 feet: East of the reactor building tunnel, the administration and boilerhouse buildings. As part of the decommissioning. process,- the two SK tanks will be removed. To accomplish this, the soil burden above and around the tanks will be removed. The presence -of soil contamination around or under these tanks from leakage has not been confirmed. As such, soil will be characterized as the excavation . progresses and dispositioned for disposal or retaino6 as backfill mate rial , as appropriate. Excavation will continue-until soil is found to meet release criteria i appropriate for the depth encountered. Upon conclusion-of remedial activities' and concurrence f rom NRC/NYDOL, ! the excavation will be backfilled with soil that meets i surface soil contamination criteria, and graded - and seeded as appropriate.
- . Yard Piping Underground piping that could have potentially
_ contained radioactive material between the reactor building, hot lab building,' building 4 and the 5K tanks will be removed as part of the decommissioning process. It is.not evident that any of this piping--has leaked, however, excavated soil surrounding this piping will be - characterized during the removal process. This soil will be sorted as requiring- disposal _ or = as . backtill material based upon - surf ace soil criteria. Should contaminat_ed soil be encountered, - the- remaining roll ' would b$ char'acterized and remediated . as - necessary to appropriate release criteria for the depth encountered. Upon completion.of remedial activities and concurrence by.NRC/NYDOL these areas will be backf111ed. ,
~
' Page . 7-JJM/193.92B-s-rW---w -tF*e-t'--*'9+rs---*--
y d e'grw MwMWM-F e -*W---^---?=--7't--v-Mry?"=--*$W4 y T' m f WW^v' yv-p
1 i 13 Soil remediation activities will generate six categories of soils that can either be left in place, or used as backfill material or which must be disposed of as radioactive waste. The six categories of soil are as follows:
- 1. Surface soils which meet surface soil release criteria (which can be lef t in place) .
- 2. Surface soils which exceed surface soil release criteria (which will be disposed of as radioactive waste) .
- 3. Subsurface soils which exceed subsurf ace soil criteria (which will be disposed of as radioactive waste).
- 4. Overburden soils that are removed from subsurface remediation areas to gain ac ces s to subsurface contaminated soil / structures, which meets surface soil criteria. This soil will be retained for backfilling subsurface areas, capping backfilled areas or abandoned elsewhere on the Cintichem site.
- 5. Overburden soils that are removed from subsurface remediation areas to gain access to contaminated soil / structures, that exceeds surface soil criteria, but which meets subsurface soil criteria. This soil will be retained for backf illing in acceptable subsurface areas (see also response #9).
Subsurface soils which could be left in place but are in excavations not deep enough to meet overburden requirements will be removed, retained and used as subsurface backfill elsewhere on site.
- 6. Subsurface soils which meets subsurface soil criteria and overburden requirements (see response to 89). This soil will be left in place.
Contaminated soils (category numbers 2 and 3) will be disposed of as radioactive waste at licensed disposal facilities, such as CNSI at Barnwell, SC or Envirocare, Inc. at Cl ive , Utah. This soil will be packaged and transported in accordance with DOT 49 CPR requirements and disposed of in accordance with 10 CFR 20 and 61 requirements. Potential category 4 and 5 soils will be placed into strong-tight-leakproof containers (e.g. steel drums, bins or boxes) at the time of excavation. At that time, samples of the soil are taken (see number 1) for future laboratory analysis. Filled containers ate next screened by direct gamma dose rate and/or direct gamma spectral analysis with a portable IG-MCA set up (when high MORM content is suspected). If this screening indicates that the potenti ally category 4 or 5 soils are really category 3 soils, they will be disposed of as radioactive waste. Otherwise, potential category 4 and 5 soils will be transferrea to a locked holding area separate from the main RCA, which is controlled by Health Physics, pending laboratory result s and JJM/193.92B Page 8
i I final categorization. Soil that is category 4 will be l I transferred and deposited on an open spoils pile (s) located within the main radiologically controlled area. Category 5 soil will be retained, in its containers, within the separate holding area until final disposition can be made. t Category 4 soil will be used for backfilling or capping any areas ; on the Cintichem site without rectrictions. Category 5 soil will- . ' be used as backfill material in any subsurface area (under or adjacent to buildings 1 or 2) that meet depth and concrete rubble thickness requirements (see response to #9). i L l l i l i l l l l JJM/193.92B Page.9 {- _ _ _ _ . . - . - _ . _ . _ . _ . _ . _ - _ _ . _ , _ . . _ . _ . _ _ _ _ - -_ , _ - , . . , _ , . . _ . . m,_- , - - . - . . . . _ . . _ . -
---_.7____._________
84 l Cintichem will use the guidance given in NUREG/CR 5849 to defino allowable " hot spots". The following summarizes this approac,h: The upper limit for soil activity hot spots at any location will be three times the applicable soil criteria using sum-of-fractions of the criteria for all radionuclides detected. Residual activity exceeding this level will be remediated and f ollow-up survey performed. Areas of elevated activity between one and three times the criteria (i.e., sum-of-f ractions are >l and -< 3) for the radionuclides precent, will be tested to assure that the average concentration is less than (100/A)b times - the criteria, where A is the area of the elevated activity in m2 . Levels exceeding this limit will be remediated. If this condition is satisfied, the average activity in the 100 m2 contiguous area containing the elevated region will then be determined to demonstrate that the average level is less than or i equal to one times the criteria using sum-of-fractions. The following equation f rom NUREG/CR 5849 with variables modified to use sum-of-fractions will be used to calculate average levels: 1 x, = - { x, U s (*1 1-{A 3 + { y,A,
&1 13 where p= = weighted mean including elevated area (s)
' systematic and random measurements results (sum-of-N fractions) at point i 4 = number of systematic and random measurement locations Yt = of-fractions in area k > Ai = elevated fraction area sum of 100 m 2 occupied by elevated area k , n, = number of elevated areas. Scanning will be perf ormed with collimated NaI detectors- (gamma l emitters) and large area beta / gamma detectors (beta emitters) to ! identify locationa of elevated activity levels within grids known to have contained or potentially corf *.ud contaminated soil (i.e. biased area 100 m 2 survey grids). Areas of - - suspected elevated activity- identified in this manner, will be evaluated by _ sampling and i. ayses to determine- their activity level and arial extent.- Additional cleanup will be perforced, .if required, and scanning repeated. After scanning has indicated .the guidelines and conditions have been satisfied, systematic soil sampling of each affected area grid block is : performed at locations equidistant between the center and each of the four grid block corners (see Figure 4.4 from NUREG 5849). I JJM/193.92B Page 10
i If scanning is not capable of detecting surface areas with l activity levels j 75% of the criteria for the radionuclides of interest, additional sampling wi' 1 be required to provide an acceptable level of confidence that locations of elevated activity have been identified. An EPA procedure (EPA 1989) recommends (enclosedaarea triangular grid with a sampling)10.8 m2 interval of assurance 5 m on a side of approximately for a 95% that elevated areas in excess of 10 m2 surface area are identified. By beginning with the standard systematic pattern and including additional sampling points, located along the 10 m grid lines, at block corners and centers, and midway between grid block corners (cce Figure 4.5 from NUREG 5849), a triangular sampling pattern with spacing of 5 m or lessFrom (enclosed this sampling area of' approximately 6.3 m2) will be obtained. pattern, a total of 13 meacurement locations would be used to characterize hot spot area and levels. i
)
l JJM/193.92B Page 11-
u-- - . .-.__.-_....w.m -,....--,.,..--#,-#_,--.w,y...y .,,-,,,.,,-% ,,,m,.m'..y py,,.--,vg ..,r -- ~., ,rw %w. y , y w&g---e Tv.. e r g r'-- e
#5 Cintichem intends to use the following background values and methodologies for differentiating Cintichem's - radioactive material and its associated external exposure rate from that caused by Naturally Occurring Radioactive Material (NORM):
Background Radioactive Material Concentration (pCi/gm) Radionuclide Surface Soil Sub-surface Soil
~
Bedrock 0 0 Cs-137 (a) 1.25 0 Sr-90 (a) 0 0 K-40 (a) 19.4 19.4- 19.4 U-234/235/238 (b) -- All at natural enrichment -- Other NORM (i.e. Th-232 & D, Ra-226 & D) -- Any amount found -- l -(a) Determined by soil sampling off and on site. The background- - l values are calculated at the 90th percentile using the methodology given in NUREG/CR 2082 Monitoring for Compliance with Decommissioning Termination Survey criteria", pp 64 - 66. (b) Due to Cintichem's location within the Reading Prong, uranium concentrations can significantly vary by location and be quite high. Background uranium concentrations will therefore be considered to be present when the ratio between each of the uranium isotopes are found to be consistent with ! natural enrichment. Cintichem's uranium is high enriched at-93 wt. % U-235. Natural uranium has 0.72 wt. % U-235. As such, Cintichem's uranium can be readily differentiated from the varying background levels by comparison of the ratio of the individual uranium isoto pe s . Any uranium found not to have the correct- ration f or natural uranium enrichment will be considered to be above background. The fractional make i up of radioactivity by isotope for typical natural uranium [ and Cintichem's HEU are as follows: Isotope Natural (Background) U 93% HEU U-234 0.489 0.9647 U-235 0.022 0.0350 U-238 0.489 0.0003 Total- 1.000 1.000 f The ratio between the individual isotopesEfor each mixture is as follows: Mixture U-234:U-238 U-234:U-235 - U-235:U-238 HEU 3216 27.6 117' Nat-U 1 22 0.45 JJM/193.92B Page 12
*"y 3 m yy3 #N wm'--e'er-a w7 vem-*r m-- -p-e d-w- e** -
ee's -te+-' 7* 't ---'8pJ'- *N'-m -'a-.a -
- ' - ' - - *- --a' -^---TA--*-*A-'-'a--- '
^^ "'*^^ - '
- m. _ _._ . _ _ _ _ __.._ ___.__.___ ___._._ ___ __.~_._ _ _.
f
, . .- i 4
Background Radiation Exposure Rates Background radiation IcVels within cintichem's geographic region vary considerably f rom one location to the next due ' to natural deposits of uranium and thorium. Exposure rates on and surrounding the cintichem facility have been found to .
- vary from 6 uR/h r up t0 160 uR/hr at one meter from the e ground or bedrock surfaces. A contact exposure rate of 1000 uR/hr on bedrock has been found on the Cintichem site. Upon investigation, it was determined to be a natural deposit of Thorium-232 and daughters.
Therefore, it is not possible to directly measure for the 5 , uR/hr criteria from Cintichem originated radioactive material in the presence. of variable and high natural background radiation levels. Cintichem therefore proposes to indirectly determine radiation levels f rom Cintichem RAM' , in soil or bedrock and exclude the- contribution f rom NORM.- To accomplish this, Cintichem will determine the gamma ray- , flux for at least one gamma ray from each non-NORM gamma emitting radionuclide present at each location of interest. Gamma rays from background radioactive material will be excluded. The gamma ray fluxes will be determined by direct in-situ i measurement with a portable intrinsic-germanium detector . (EG&G ORTEC model Gamma-X HPGe 10200-P) and multi-channel analyzer (EG&G ORTEC model 7500B). At each location of interest, a gamma ray spectrum will be obtained and the resulting photopeaks identified. Photopeaks f rom naturally occurring radioactive material will be excluded, and the , remaining ones attributed to Cintichem RAM. The-count rate f rom each photopeak will then be converted to a gamma ray flux and attributed to a particular radionuclide. In some ' instances, some photopeaks from -Cintichem RAM may be obscured by interferences from gamma rays from natur ally - occurring RAM or other Cintichem RAM. When this-happens, corrections will be made to account for obscured gamma rays by inferring the gamma ray flux of those that cannot-be seen to.those that are present based upon the decay scheme of the gamma emitters found. As an example, Cobalt-60 has two gamma rays at 1.173 and 1.332 MEV at 100% abundance. If the ' 1.173 MEV gamma was detected, but the 1.332 MEV gamma was obscured, t'e a 1.332 MEV gamma. ray flux could be inferred to have an equal gamma ray flux as the 1.173 MEV-gamma ray. At each measurement ' location, the total gamma--ray flux would be tabulated by energy grouping for the gamma rays produced by Cintichem RAM. The gamma ray, flux profile would then be-converted to a corresponding exposure rate. ~ This exposure rate would then represent the exposure rate above a variable background. JJM/193.928 Page-13 t _\
i The 5 uR/hr at one meter criteria will be applied to surface-soil areas and bedrock surf aces to . be -lef t exposed. It is ; proposed that subsurface soil and bedrock surfaces not be ;
-held to the exposure rate criteria until backfilling and capping has taken place. ,
r t F i t
'JJM/193.92B- Page-14 ;
bL _ , _ ;_. .. _ . _ _ . . _ , . . - _ , , . . - - . . _ .....-. -_. .,_ _. ._.-,...__,._--_..___._-,.._-_.____.,._.-__..--__i_
1 a '
. l i
66 Remediation of soil to the 10 mrem /yr level is estimated to require the removal and disposal of about 42,600 f t3 of packaged soil. Using a 1993 rate of S284/ft3 for removal, handling and disposal (see response to question number 1 from the October 22, 1992 submittal), a cost of $12,100,000 will be incurred. Remediation to the 20 mrem /yr level is estimated to require the ; renoval and disposal of 7,350 ft3 of packaged soil. Using the same rate as above, this would cost S2,100,000. Soil remediation to a level of 5 mrem /yr is estimated to require the additional removal and disposal of 173,100 ft3 of soil above the 42,600 ft3 needed to meet the 10 mnem/yr criteria, producing a total soil volume of 215,700 ft3 If the additional 173,100 ft3 is assumed to meet disposal requirements of the Envirocare facility in Clive, Utah, which has a lower disposal rate, the total cost of : remediating soil to the 5 mrem /yr level would be S22,600,000. If 1 the additional soil did not meet Envirocare facility criteria (which is currently the case) remediation to the 5 mrem /yr level would cost $61,260,000. The proposed criteria for residual soil contamination is deemed to be -reasonable from the ALARA standpoint because of the rollowing conservative assumptions that were made for calculating , the dose pathway analysis and also because of the conservative approach taken for choosing distribution coefficients for use in the RESRAD model. These are summarized as follows: Conservative Assumptions
+
The time of maximum exposure from the radionuclides that will be left in Poil af ter the decommissioning process is completed will not occur simultaneously. The proposed criteria assumes that it will. Therefore the actual maximum dose will only be ! a fraction of 10 mrem / year. No credit has been taken for shielding or distance from contaminated buried rubble in calculating the total dose. The estimate of the area of the affected zone (sub-surface) that was used in the model calculation is now known to be at least 61% of that postulated in the model and therefore - the sub-surface criteria could be 39% higher than that ps oposed.
- - The family-farmer scenario that was used as the basis.for the dose calculation is not very likely to happen within the foreseeable future. This I r.ao is more likely to be used either as an indust ri al si'.e or as a public park.
Porthermore, the projectv dose decreases significantly within 20 years following ccmpletion of decommissioning. Under any circumetance the most likely future water supply would be the reservoir as opposed to wells. It was assumed thit future water -supply would be from wells in the dose pathway analysis. JJM/193.92B- Page 15
*--,w , - - - , - 5- .,g. ,.w.,-- - .ei ...--..,,-.,,,.m.m..mm,,,e.me-.-w...,.w,..-__,..-,,--% . , . . . . . . - -.--r --._,,m -- -
l 3 Affected surface zones were assumed to be contiguous in the model calculation. *
- Without any remediation accomplished to date on soils under the hot laboratory building, Sr90 is the only radioisotope of .
Cintichem origin currently detectable in monitoring well water ' and it is below the EPA drinking water limit in all but two wells that are adjacent to or under the affected zone. After contaminated soils are removed from underneath the hot lab building this condition will improve significantly. The current EPA drinking water standards limit the dose'to any organ to less than 4 mrem as opposed to limiting the Committed Ef fective Dose Equivalent. The proposed acceptance criteria for soil and water will cause any ground water on site to be below EPA drinking water limits. Conservative Choice of Distribution Coefficients cintichem's choice of distribution coefficients (Kd 's) for use in the development of soil residual- radioactivity guidelines has been directed by site-specific sampling, a review of available published data, the potential impact upon the project, and , conservative engineering judgement. The following discusses items considered by Cintichem prior to the choice of the Sheppard and Thibault methodology, used to develop Kd's and subsequently employed in-the RESRAD determination of soil guidelines. Cintichem has previously stated that_ the determination of Kd for each potential radioisotope in (ach affected area of the site could potentially require- several- hundred measurements.- Cintichem has chosen to eliminate the. expense and _ time required by these determinations by the judicious choice of conservative, published values. The use of conservative Kd values will bound-the- RESRAD calculations, and will represent all- contaminated areas and hydrogeolgic~ units along the transport pathway. Appendix H in the documentation provided with the RESRAD manual describes three optional methods which may be used in lieu -- of site-specific values ~ for Kd. These methods are referred to as the groundwater concentration method,- the leach. rate method, and the plant / soil concentration ratio (Sheppard and Thibault) ,
. method. :Of these three optional methods, only the Sheppard and_. +
Thibault method may be -used successfully. - The . groundwater concentration __ method requires input of_ : the - elapsed _ time since radioactive material placement, which Cintichem'cannot reasonably determine -in some areas. The leach - rate- method requires the. determination of leach rates for each radioisotope .in each location _of interest (a task-as difficult,_if not more difficult than the determination of Kd's).- , JJM/193.92B Page116:
-i
%,+ *---~.-,.w.....m. - __,m..m. ~ . . . , ~ , . . . . . , - ,.--i.,,-.,,___,,,n,-
,,_,,,r,-- - - - - , --,,,,,o
Cintichem has chosen to derive Ka's using the most conservative form of the Sheppard and Thibault methodology, i e., for sandy soil. Previously, Cintichem submitted to the Staf f results of Kd . determinations for cesium, cerium and strontium to benchmark the calculated Kd values - used. Additional Kd determinations for cobalt, europium and silver and other radionuclides have been performed with contaminated soil and water found in the HUT excavation (see response 88). These Kd determinations were made on soil samples considered most likely to provide conservative Kd values (sandy-type soils). A comparison of results is provided below. Ed Used In Radionuclide Measured Kd RESRAD Calculation Strontium-90 14.7 9.2 Cesium-134 106 92 Cesium-137 270 92 Cerium-144 171 184 Cobalt-60 > 99,379* 135 Europium-152 > 309* 82 Silver-110m > 111* 11 (* See response #8) The above results benchmark, and validate, Cintichem's use of the Sheppard and Thibault algorithm for sandy soil. The isotope s l listed in the table above are anticipated to represent greater [ than 99% of the total activity to be found at the site. The Sheppard and Thibault methodology allows Cintichem to determine Kd's for elements which do not have def ault values in the RESRAD code.
- cintichem has employed " bedrock" Kd's as suggested by . Leggette, Brashears and Graham for the saturated zone beneath the subsurface contaminated zone in the RESRAD analyses. _These Kd's are far more conservative than those contained in the RESRAD manual or developed using the Sheppard and Thibault algorithm, and -will result in higher dose rates - f rom- the water-dependent pachways which dominate the dose rates due to the subsurface contaminated zone. However, considering the geology of the site, Cintichem deemed their use to be an appropriate conservatism.
Cintichem gave' consideration to " bounding" th'e soil: guidelines by considering artificially high and artificially low distribution coefficients. The. uses. of _ ar tif ici ally high values retards radionuclide transport into the_' aquifer below. This would tend to increase the . dose rates f rom the water-independent pathways. Cintichem discovered through RESRAD analyses that dose rates from water-independent pathways for the dominant - isotopes- (the strong 3
- gamma emitters, e.g. cobalt) were a maximum at t = 0 years.
- Thus, Kd.has no ef fect upon the resultant dose rates for .these i s ot ope s.-
--JJM/193.92B Page'l7
-_. = * - *
- 1 Cintichem was unable to justify the use of artificially low distribution coefficients. Setting Kd to 0 would appear at first to be a logical conservatism. However, if this were true, there would no longer be any radionuclides detectable-in the soil.
The conservatively low distribution coefficients published in the ROSRAD manual (those listed for sandy soils in Table E.3) do not have strong analytical support. As noted in a footnote to the table, these values are simply taken to be 10% of - the Kd values for soils and clays (except for cesium). Cintichem does not-believe these values represent as valid set of Kd's as those derived using the Sheppard and Thibault methodology. Additionally, as stated earlier, Cintichem has measured Kd values for those radionuclides expected to most significantly contribute i to radiation doses. These measurements indicate Kd is not zero 1 and that the use of the Sheppard and Thibault methodology most closely represents reality.
-The following graphs present RESRAD calculations for the _most significant radionuclides that have been found in the subsurf ace contaminated zone. As may be noted, all of these isotopes-will I reach their peak dose rate contributions at different times. The most significant contributors to doce are Sr90 and Cs137 and they
! peak at approximately 3 months and 1 year respectively af ter disposition in the soils. The other radionuclides of Ag110m, Co60, Cel44 and Eu152 also peak at dif ferent times but they are r all at least an order of magnitude icos than Sr90 and Cs137 at their respective peaks. ! It may also be noted that all of these radionuclides will be a ~ _ l l f raction of their peak ten or more years into the f uture. ! l 1 l i i l l
?
JJK/193.92B Page 18
.- - . - . . . -- .- . . . - , --. - = . - . . ,.- .:. : . . . - -,
8 2832725218 AHL ANALYTICAL 12/02/92 998IS P.et DOSE ,, 0.0000 Water Independent & Dependent Subtotals, As-110m
,,-y,,, , , , . , , , , ,
/%
/ \ .
0.0050 \
/ \ .
/ \
i u 0,0040 _/ \ .
'-( \
\
b'
$0.0030 - \
o .
- L h
, E \ l 0.0020 - l \ O - Independent -
\ a - Dependent 0,0010 _
\g
\
\
0.0000 C -- a m - a -_ Nsy . r g- =. . 0.1 1 10 100 Years CINT141.DAT 12/01/92 21:12-1
'4rr-=mP+g -*N'-
~
l DOSE Water Independent & Dependent Subtotals, Cs-137 0.04 , ,
/' w s
~
s N 0.03 _
2
/ -
/ s'N -
L
/ \
N / \
/ % -
E 0.02 _ N _ o /
\
L / E \ f \ '
/ 0 - Independent \
/ t - Dependent O.01 -
/ ( -
/
,/
/
0.00 6 3 s. 6 a me t e c < 0.1 1 10 100 Years CINT110.DAT 12/01/02 21:01 1
O 2 32F252tl AHL-ANALYTICAL 12/02/92 89816 P.04 A DOSE ~ 0.08 Water Independent & Dependent Subtotals,'Sr-90 0.06 _ -* -- D - Independent
- s 'Nw
/
/T A - Dependent L -
j % N '
\ .
N / N
$ 0.04 _ / \
e \ _ u /
\
g / N-1 N ' 0.02 _
\'\ _ _
\
-\
\- .
N s 0.00 e c = 6 .e , ga . . .g g g.... 0,1 1 10 100 Years CINTIS.DAT 12/01/92 20:58
.q
DOSE , 0000a Water Independent & Dependent Subtotals, Co-60.-
. , , , 7- , , , , , , ,
n - 0.0006
/g s l N
\ -
/ \ 0 - Independent g / \_ ^ - Dependent x / \ -
N j \
$ 0.0004 _
j \ c % ~ u /
\
I - /
\
/
/ \
0.0002 ._ / \ n -g - %. -
/
/ "% \
\
n.
\
0.0000 . . . .. . , ., \s. , ,, 0.1 1 10 100 Years CINTl3.DAT 12/01/92 20 56 1
- 1. I
~ , _I_ , ,
_ _ __ -m . - . _ ~ . _ . - _ _ - - O 2832725218- 4HL RHALVTICAL
. s e 12/02/92 Stale P.85 4
\
i i DOSE ' 2.510') Vater independent & Dependent Subtotals, Ce-144-i l 2.0 10" . 8 '\ $ I s
/ \ .
/
/ \
p \ 1.5 10" _ y / \ - b O - Independent N
/ \ ^ - Dependent
'/ 1 E / .
c 1.0 10" _
\ .
u ,/
\ -
E / \
/ \
5.0 10" / \ e \
\-
\ -
- 0.0 r' n - -- m 2
r . 0,1 61 : - - 1 10 - 100-Years ClNT111.DAT-12/01/92.21:04-g -:: T-
)
- y
? -:- 3= _
;__1_
,,A-,,,4.- ' '
t" w* -- , ,,.,-4,.+---
,. .,n_i ,-.,,-, H+-,-- .mm,--e- .-.. ._ , .,-e _.._...m. . . . vm c --+ 'c.s s
O 2012725211 AHL ANALYT!CEL 12/02/92 e9:10 e P.06 1 i l i DOSE g,g ,g.) Vater Independent & Dependent Subtotals, Eu-152
- - - - i ,
,,,,1.
- -- w ~. ,
i 1 5.0 10" ~~% %
'N N
4.0 10" D -- Dependent Independent l3
\\ t_ ^
k N 3.0 10" . N E g _ o - x L
\
g 2.010" _ \
~
\
1.0 10"a -c g. \ g , g _ 00
% \
l t a . _w N D, 0.1 1 10 100 Years CINTl19.DAT 12/01/92 21:06 l 1 i l 1
~
l i 4
#7 Cintichem does not believe that there are non-contiguous zones of subsurface soil contamination separated from the known or suspected contamination source areas.
All known and suspected soil contamination areas will be excavated or otherwise checked for contamination (as was described in. the responses to NRC requests for additional information related to the Decommissioning Plan). Non-contiguous zones of soil contamination are not possible for the following reasons, (1) there are 29 monitoring wells that surround the facility at varying distances from the facility. None of these wells indicates the presence of soil contamination except where a known source location exists; (2) water monitoring well data ' indicates decreasing radionuclide concentrations with increasing distance from the soil contamination sources,- (3) more , significantly, the mechanism or contaminant migration in soil - would not allow the front of a plume to become separated from the plume area near the source as long as the source is still present. That is, the concentration of a contaminant in a plume , decreases expotentially with distance as long as the source is still contributing radioactivity to the pl u,o e . 11oweve r , non-contiguous surface contamination is a possibility. These areas, if present, would be detected by the systematic and biased final survey direct measurements and soil sampling program (described in prior submittals). 4 1 JJM/193.92B Page 19'
. . - . - _ . . - - - . - . . - . _ - - .-.-.-.L-. .:. - - . - . . . - . . - . . _ -- . _ . . . - - - . .
..-. - .~_..- - - .- .- - . - . - - - . - - - - -
-~ - -.- . .-
#8 Cintichem has recently performed an additional benchmark of the calculated Kds that were used in the RESRAD calculations. Assays of excavated contaminated soil and the water were used to determine in-situ Kd's. At least two pounds of soil was taken from the excavation, prepared for assay, and assayed as described in answer 41. At least ont liter of water at the approximate location of the soil was taken and analyzed as per HP-M-55 (attached). The following chart tabulates the soil i concentrations, water concentrations and resultant Kd according !
to the formula Kd - (in ml/g) = (o of sorbed nuclides)/(q of solid) (g of nuclide remaining in solution)(m1 of solution) (as seen on page 220 of the unpublished RESRAD manual.) Conc. Conc. in soil in water Isotope (uci/qm) (uci/ml)_ Kd Mn54 2.79E-6 <1.18E-8 > 236.4 CoS7 6.51E-7 <7.80E-9 > 83.5 Co60 4.80E-4 <4.83E-9 >99378.9 Zn65 6.17E-6 <4.48E-8 > 137.7 Zr95 2.80E-6 <1.15E-8 > 243.5 Ag-108m 2.78E-5 <5.84E-9 > 4760.3 Ag-110m 1.47E-6 <1.32E-8 > 111.4 Sb125 9.48E-6 <7.80E-9 > 1215.4 . Cs134 8.93E-5 <2.88E-8 > 3100.7 C137 2.40E-4 <4.63E-9 >51835.9 > Cel44 5.11E-6 <4.77E-8 > 107.1 Eu152 7.10E-6 <2.30E-8 > 308.7 These Kd results are greater than values since the water had only , MDA values. While this determination was not performed in accordance with ASTM D4319,_ it does provide an indication that the Kds used are conservative. P 4 4 J JM/19 3 .'.9 2 B - Page-20
. . _ . . ._. . i _ _ _ - _ _ _ _ - - - _ _ _~ _ .~. _ _ _ _ . _ . _ _ _ _ . 1._ _._._ _ . _ ,
#9
'i r
- 1 c hem would '; refer to cover soil meeting subsurface limits a minimun. f 20 feet of clean concrete rubble and fill
-ith at least 3 feet of clean soil. Use of a 25 foot tyer of concrete rubble may not provide a sufficient
; unless the finished capped elevation was about five feet pg h1 :t s 'han the now cristing grade.
N 4 i i I s
~
JJM/193.4B Page 21 _}}