ML21258A249
| ML21258A249 | |
| Person / Time | |
|---|---|
| Site: | 07000925 |
| Issue date: | 11/13/1995 |
| From: | Jim Larsen Cimarron Corp |
| To: | Weber M Document Control Desk, Office of Nuclear Material Safety and Safeguards |
| References | |
| Download: ML21258A249 (10) | |
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CIMARRONP.O, BOx25861 ORPORMION OKLAHbA CITYOKLAHOMA 73125 S JESSLARSEN VICE NT PRESIDE November 13,1995 Mr.Michael F.Weber Chief, Low-Level WasteManagement j andDecommissioning Projects Branch !
Division ofWaste Management l Office ofNuclear MaterialSafety andSafeguardp U.S. Nuclear Commission Regulatory Washington, DC 20555-0001 1
Ref: Docket No.790925, License No SNM-928 NRCcomments (dated Septem er5,1995)on Cimarron Corporation's July, 1995"FinalStatus Survey Reprt, Phase IAreas at theCimarron Facility"
Dear Mr.Weber:
l Thepurpose ofthis lettertorespond is tothe NR comments pertainingtoCimarron Corporation's
.)uly, 1995 "Final Status SurveyReport, Phase I easatthe Cimarron Facility". For clarification, we have includedtheNRC's comments followe bythe Cimarron Corporation response.
Based uponthe results ofthe original report andthe additional investigation andreassessment as requested byNRCandcontained herewith, Cim on Corporation requeststhat theNRCissue a license amendment torelease thePhaseSub-Ar I as(Sub-Areas CandE asamended herein) from License SNM-928.
Please contact me if thereareanyadditional queptions orconcems, orifwe canbeofanyfurther assistance.
Sincerely, Jess Larsen l Vice President l I11395.le ji I OFKERR-MCGEE A SUBSIDJARY CORPORATION
NRCCOMMENT #1:
Thereport doesnotindicate which samplescontain uranium orthorium inconcentrations thatare above statistically background. Please provide alist ofthe resultsthat arestatistically above background.
CIMARRON RESPONSE:
TheFinal StatusSurvey Report for Phase IAreas did notprovide a list ofsample results which contained uranium orthorium inconcentrationswhich were statistically above background because theNRCapproved FinalStatus Survey Unaffected Areas Plan for (i.e. Phase ISub-Areas) statedthatsample resultswould becompared to25% of the guideline value plus background (i.e.
11.5pCi/g for totaluranium andj4pCi/gfor total thorium). As stated onpage 10ofthe FinalStatusSurvey Report for Phase I eas, "Foran unaffected area, NUREG-5849 recommends reclassifyinganunaffected areaif y individual sample result exceeds 75%ofthe guidelinevalue (i.e.
22.5 pCi/g totaluranium ab vebackground for BTP Option #1material)",
Inthe NRC's May1,1995 response toCimarron Corporation's Final Status Survey Plan for Unaffected Areas,theNRCrecommended thefolowing: "In lieu ofreclassifying theentire area ifa sample exceeds75%ofthe limit, the staffw uld accept a commitment toinvestigate any individualsample resultexceeding 25%ofthe liit". Inaccordance with this recommendation, Cimarron Corporation committed tofurther investigate anysample location with concentrations exceeding 25%ofthe guideline value plusbackground (i.e. 7.5 pCi/g + 4.0 pCi/g = 11.5pCi/g totaluranium) bylettertoNRCdated March 24,'1995. This approach wasapproved bytheNRC bylettertoCimarron Corporation dated May1,li995. Therefore, anysample results which indicateduranium orthorium concentrations above 25%oftheguideline value plus background wereinvestigatedfurther.
Asdiscussed onpage 22ofthe Final Status Survey Report for Phase IAreas, only onesample obtainedfrom the fiveUnaffected Sub-Areas conltained a total uranium concentration inexcess of25%ofthe guidelinevalue (12.4 pCi/g uljanium total atgrid location 700N-400E). As also discussedinthe Report, thissample location wasjfurther characterized through the collection of samples additional atonemeter distances from this sample location. All ofthese additional sampleswereanalyzed andnoneofthese samples contained total uranium concentrations in excessof25%ofthe guideline value plus backgr und.
Asdiscussed inthe response toNRCComment # below, a small section ofSub-Area C (containingthesample result 12.4pCi/glocati at n 700N-400E) andoneother small section of l
1l
Sub-Area E have been removed from the Phase ISub-Areas andwill beaddressed later under Phase II ofthe Final Status Survey.
Noneofthe samples taken from the five Unaffected Sub-Areas contained totalthorium concentrationsin excess of 25%ofthe guideline value 2.5 (i.e., pCi/g + 1.2 pCi/g = 3.7 pCi/g totalthorium). As no sample results contained total thorium concentrations inexcess of25%of the guideline value,no further evaluations orinvestigations wereperformed byCimarron Corporation inaccordance with the NRCapproved Phase IPlan.
However, inresponse toNRC Comment #1, Cimarron personnel have performed "Critical Value" calculations todetermine both uranium add thorium statistical background values in accordance with relationships established byJack J.DonnandRobert L Wolke in"The StatisticalInterpretationofCounting Data from Measurements ofLow-Level Radioactivity" (Health Physics,Pergamon 1977, Press, Volume $2, (January),pp. 1-14.). These calculations were performed inorder todetermine whichsample(s) contained uranium and/or thorium concentrations which werestatistically above bac ground asrequested byNRC.The"Critical Value", ascalculated herein, represents the 95% ean probability ofdetection atthe 99%
confidence intervalfor the contaminant ofconcerp.
The"Critical Value" forboth thorium and uraniu wasdetermined for the Cimarron site after modification ofDonnandWolke's work toinclude theerror associated with average site background concentrations insoil. Thefollowing equation wasused:
r 1f c,, -
c, > n, c<,j 32 c, + aA, + a /
where: Cs3 andC3 arethe sample gross count andthe background (i.e.,
blank) count; tse andt3 arethe sample counting time andthe background counting time; naistheWphercentile Oftheunit ormal distribution, where o isthe probability ofType Ierror;j as+ece and are equal to the standard deviation ofthe counts forthe sample and background (,the square ofthe standard deviation isequal tothe variance).
Forthe Cimarron Phase Isoil samples, ts+handte Are equal to30minutes. Setting a toa value of 0.01 results ina value for naof2.326. Inaccordance with DonnandWoIke, ifthenetsample count(i.e., theleft hand side ofthe above equation) isgreater than the r ight hand side ofthe above equation, onecanconclude that the netsample count rate isgreater than zero.
Simplification ofthe above equation ispossible dtte tothe equality ofthe sample andbackground count times. Inaddition, the gross sample andbackground counts andtheir associated standard deviation termswereassumed tobeequivalent (i.Cs3C3andas3 as).
= = Thebackground term, C3, wasmoved tothe righthand side ofthequation toprovide arelationship based upon thegross sample count. Theresulting vajue" "criticalequation isprovided below. Ifthegross counts (the lefthand sideofthe equation) exceeds! the criticalvalue (the righthand side ofthe l
2!
equation), itcanbesaid that the sample has asmill probability (1percent) ofbeing within the sitebackground distribution.
C ,,3 > n, [2 (C3 + o- / )) + C ,
Total thorium andtotal uranium critical values in;soilwerederived bysubstituting the equivalent number ofcounts and standard deviation for the(verage background concentrations. Fortotal thorium, average background inCimarron soil halspreviously been establishedusing theon-site soil counter as1.2 j- 0.25 pCi/g. Thethirty samples used for thisaverage ranged from 0.7pCi/g to1.7 pCi/g.
Utilizing the above equation, the critical value foj totalthorium insoil wascalculated as2.0 pCi/g. Similar calculations for total uranium, baedupon the averagetotaluranium background (4.0 + 1.3 pCi/g,range: 2.3 pCi/g to6.3 pCi/g), r sulted in acriticalvaluefor totaluranium of 8.3 pCi/g.
Thesample results from each ofthe five Sub-Areascontained in Phase Iwerethen compared to these criticalvalues todetermine if anysample resultsexceeded such values. This comparison does notinclude the sample results from the twosmall sections ofSub-Areas C and E which have been removed from the Phase ISub-Areas asdescribedin the response toNRCComment
- 2below. Theresults ofthis "Critical Value" evaluation aresummarized below inTable 1:
T.gtb.1e1 Sub-Arca W Samples.> 83.pCi/g.U l
A 62 !8 1 B 43 0 0 C 36 0 1 D 32 '
0 1 E 63 0 0 Asshown inTable 1above, eight sample locatiortscontained totalthorium concentrations which wereabove thecritical value. Theeight sample locations inSub-Area A which contained total thorium concentrations above thecritical value (ije.
greater than2.0 pCi/g) areshown below in Table 2with thecorresponding sample locations.)
j l
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--,+ --.- . --- -- --
Lab[lel Sub-Area Grid Location Thorium Concentration A 200S-100E l 2.1 pCi/g A 300S-0E l 2.2 pCi/g A 300S-100E 2.1 pCi/g A 400S-100E 2.3 pCi/g A 400S-200E j 2.2 pCi/g A 500S-0E 2.1 pCi/g A 500S-100E . 2.1 pCi/g A 600S-0E 2.4 pCi/g AreaA has been farmed during the entire time priod since the facility wasestablished.
Fertilizer has been spread upon the land andwill jhave had someimpact onthorium concentrations. In addition, soil type has b eensliown tohave some influence with respect to concentrations ofnaturally occurring thorium anduranium. Cimarron collected tenadditional soilsamples toassist inthe evaluation ofthe eight samples exceeding the critical value for total thorium. These samples were collected from ac$ltivated field approximately onemile south of the facility. Thesoils collected consisted ofred elay similar to those found within SubArea A.
However, the additional samples appeared tohave aslightly higher loam content than those from SubArea A which exceeded the critical value. Theprevious soilbackground samples were collected from areas around the sitewith varioussoil types ranging from sandy loam t oclay.
Thus, the background of1.2 i 0.5 pCi/g (2a) repesented anaverage for the several types ofsoil found atthe Cimarron facility.
For thelatest background sampling event, the avrage thorium background insoil was calculated as1.4 i 0.2 pCi/g (20), with sample results rangig from 1.3 pCi/g to1.6 pCi/g. This average is higherthan the average sitewide background of1.2 pCi/g.
Theeight samples taken from Sub-Area A with t tal thorium concentrations slightly abovethe critical value documents.
werecompared Table 4.3 from toconcentrations the report "Exposurelof o(total the Threported Population inNCRPandNRC inthe United States and Canada from Natural Background Radiation" (NCRP Report No. 94, D ecember, 1987) lists Th-232concentrations inthe average continental crust (from Taylor andMcLennan, 1985) andin soils(from Lowder, etal., 1964) as44Bq/kg (1. pCi/g) and37Bq/kg (1.0 pCi/g), respectively.
Totalthorium concentrations canbeinferred bas4d upon presumption t he of equilibrium between Th-228 andTh-232. Concentrations oftotal ThWould range from 2.0 pCi/g to2.4 pCi/g based upon theNCRP94data andthe above assumption. Thesamples inArea A are allwithin this range.
Draft NUREG-1501, "Background asaResidual adioactivity Criterion for Decommissioning" also provides typical concentrations for Th-232 i soils. Table thereport 2.2 o f gives the average Th-232 concentration inU.S. soils as36Bq/kgpCi/g) ( ,
with a range of4-141 Bq/kg (0.1-3.4 I
i b
I
r .-
pCi/g) Assuming equilibrium between Th-232 and Th-228, the average U.S. soil contains 2 pCi/g total Thand ranges from 0.2to6.8 pCi/g. Theconcentrations oftotal thorium inthe Cimarron Phase Iareas fall within these ranges.
Sub-Area A is both upgradient andupwind (preominantwind direction isfrom theSouth and Southeast) fromthe Cimarron Facility. These eihtsamples represent less than 3.5% ofthe samples obtained from the PhaseISub-Areas (i.95%confidence
> level). Inaddition, Total uranium concentrations in the eightsamples whi h the exceeded t otal Thcritical value ranged from 3.8pCi/g to6.6 pCi/g. None of theeight s ples contained uranium atconcentrations above thecriticalvalue (8.3pCi/g). Therefore, i isunlikely that the thorium activity inthe eight samples wasdue toeither drainage orairborne dspersion.
Thethree sample locations which contained tota uraniumconcentrations above the critical value arealso shown inTable 1 Specific information n these threesamples isprovided n below i Table 3.
Sub-Area Grid Location Uranium Concentration A 600S-100E l 8.4pCi/g C 900N-500E : 8.6 pCi/g D 550N-150E 9.8 pCi/g Asstated earlier,noPhase Isamples wereobse'ed inexcessof25%ofthe guideline value (i.e.
> 11.5 pCi/gtotal uranium) afterthe t wosmall s ctionsofSub-Areas C and E were removed as described inthe response toNRCComment #2. ub-Area A is both upgradient and upwind (predominant wind direction isfrom the South from a d Southeast) the Cimarron Facility. Sub-Areas C andE areboth downwind from the Cimrron Facility.
These three samples represent less than 1.5% ofthe236samples obtained fromthe ISub-Areas Phase (i.e.> 98.5% confidence level). !
i
NRC COMMENT #2:
It appears that the area defined approximately bylgrid locations 400E-700N to500E-700N, in Unaffected Sub-Area C,contains licensed material. This isbased on1) the sample that contained 12.4pCi/g total uranium, 2) the fourinvestigation samples collected around thearea containing the 12.4pCi/g sample that averaged 9E4 pCi/g total uranium, and3) the independent laboratory resultfromthe same area thatindicated the presence of enriched uranium. An investigationshould beconducted todeterminethe source ofthe licensed material.
Page 27ofthe reportindicates that this area isnear adrainage area. Ifthe investigation confirms thatlicensed material ispresent inSub-Area C due todrainage from contaminated areas, the unaffected area boundaries should bereassessed jo ensure that allsite areas that could potentially receivecontaminated runoff areclassified as affected.
CIMARRON RESPONSE:
Cimarron Corporation submitted the Phase IFindl Status Survey Plan forUnaffected Areas to theNRCfor approval inOctober, 1994. ThePlat wassubsequently approved bytheNRCon May 1, 1995. The Plan that statedsample resultsjwould becompared to25%ofthe guideline value(i.e.11.5 pCi/g total uranium), andif greater than 25%ofthe guideline value, further investigation would beperformed. '
Asdescribed inthe Final Status Survey Report for Phase IAreas, sample location 400E-700N hadauranium concentration of12.4 pCi/g total uranium andwasfurther characterized.
Additional characterization wasperformed whicli involved sampling four locations at onemeter fromthe sample original result, the sample average location.
was9.4 pCi/g total fouj Whenthe sample uraiumwith results wereaveraged a standard deviation with the original of2.1 pCi/g. As nosample results indicated a totaluranium concetration above 25%ofthe guideline value (i.e.
11.5pCi/g totaluranium), nofurther investigatiot wasperformed. (This is the a reac ontained withinSub-Area C which wasdescribed ascontajning licensed material inthe NRCComment#2 listed above). '
CimarronCorporation continues toassert that all sample results from thePhase IUnaffected Sub-Areas meetthe clean-up criteria asapproved jby theNRCinthe Final Status Survey Plan for Unaffected Areas. However, asrequested bythe NRCinComment #2above, Cimarron Corporation hasperformed additional investigations todetermine the potential forlicensed material tobepresent inUnaffected Areas, with aj particular emphasis being placed on Unaffected Area boundaries possibly impacted bjdrainage from contaminated areas. These investigations,aswell asthe resultsofthese inve tigations, are discussed below:
A detailed investigation /review wasconducted v Cimarron Corporation todetermine ifthere wereanypreviously unidentified drainage ways thpacting unaffected area boundaries which have could potentiallyreceived run-off from anaffected area. The Characterization Report, 6!
I
l USGS maps, aerial photographs, andother historlcal documents were reviewed.
unaffected Additional site investigations were performed toevaluate anydrainage areas impacting areas, aswell asany potential affected areas located upgradient jfrom such drainage areas.
A review ofthe Cimarron site topography indicat sthat the predominant drainage wayshave been identified and designated aspotential affect dareas. These areas were identified inthe Cimarron Decommissioning Plan and the Cimarr n Radiological Characterization Report, and are scheduled tobeaddressed duringthe Phase IIFinal Status Survey. A bermed area which is located along the southern boundaries of Sub-Ar as C,D, andE wasbuilt manyyears ago the for prevention ofsoil erosionand moisture control f rthe cultivated fields located north ofthe Cimarron Facility. Surface water runoff from hiher elevations wasdiverted east along the southern boundary ofSub-Areas C, D, and E bytay ofthis berm. Notall ofthis bermed area wasoriginally included with the d rainage areas d scussed in theD ecommissioning Plan, Characterization Report, and/or other submittals uetothe fact that this wasconsidered tobean unaffected area. j l
Uponfurther investigation andreview ofthis berped area, it wasdetermined that Sub-Area C contained asmall section north ofthe predominapt drainage way, but south ofthe berm. This section of Sub-Area C contains the sample locati$n 400E-700N. It was determined that under extreme rainfall events, this section couldhave rdceived run-off from the predominantdrainage area running east along the base ofthe outcroppijgs.
Aninitial attempt wasmadebyCimarron Corpor tion toperform additional characterization in the general area ofgrid location 400E-700N. Hovever, this portion ofSub-Area C isfrequently muddy andcontains significant undergrowth. T spresented significantoperational obstacles with respect toperforming additional characteri tion efforts inthis area Oneother location wasidentified inSub-Area l
E thich could potentially have received runoff from anaffected area located upgradient.cation.
tothis 1 This section ofSub-Area E is located just westofBurial Area#2.
Asa result ofthis investigation, Cimarron Corporation hasdecided toremove a small section (which includes sample locations 400E-700N and500E-700N) from Sub-Area C andanother small section from Sub-Area E.Cimarron Corpotation continues toassert these that areas are unaffected areas, but willdefer addressing these areas until further characterization canbe completed. Cimarron Corporation will address tljese twosmall sections under the Phase IIFinal Survey. Cimarron Corporation has confirmed that all other drainage ways have b een p reviously identified andaddressed inother license submis.Drawing No.95MOST-RF3 (Rev 2)is attached andshows thetwosmall sections which have been removed from Sub-Areas C andE.
Asdiscussed above intheresponse toNRCCom ent#1, Cimarron Corporation performed a "Critical Value" evaluation todetermine which s mple(s) contained uranium concentrations which werestatistically above background. The valuation wasperformed using the soil sample data collected for the finalrelease ofthe five SubAreas with thetwosmall sections from Sub Areas C andE removed. The"Critical Value" fototal uranium wasdetermined tobe8.3 pCi/g
for average Cimarron site soils. Three sample locations contained total uranium concentrations above the "Critical Value". Oneofthe sample lqcations wasinSub-Area A,another wasinSub-Area C, and the other wasinSub:Area D.These three samples are listed inTable 3above, along with theirrespective grid locations. Nosample lpcations wereobserved with total uranium concentrations above the "Critical Value" in Sub[Areas l
B andE.
Cimarron Corporation also reassessed each ofthsethree sample locations todetermine ifa potential existed for licensed material tobepres tdue toairborne emissions during facility operations orif the sample analysis results appeak tobe due to statisticalvariability.
A review ofthe historical windrose datafor theimarron facility(1945 through 1990) reveals a prevailing wind direction from the South and So5theast (Wind RoseOklahoma City, Oklahoma Climatological survey data, WSFO). The wind tpically originates out of thes outh and southeast fortenmonths outofthe year.Thus, ahy elevated sample locations tothe North and Northwest ofthe Uranium Building couldhave heenaffectedbyairborne stack emissions from the Uranium Facility during operations from 196$through 1976.
Thesample location 600S-100E (8.4 pCi/g total (tranium) in Sub-Area A is slightly above the critical value (i.e. 8.3 p Ci/g totaluranium). Thislsample location is n eart hes outhwest corner of the siteproperty andcould nothave been affected bydrainage from contaminated areas since this area isupgradient tothe facility.This sample location isalsopredominantly upwind south)
(i.e.
ofthe Uranium Process Building andisapproxinkatelyfrom thenearest 0.5 m iles affected area.
Sample results on100mx 100m grid points surrdunding this sample location are all less than 6.6 pCi/g total uranium. Based upon this investigation, indications arethat this sample result isdue tostatistical variability.
Thesample location 900N-500E (8.6pCi/g total pranium) inSub-Area C isalso slightly above the critical value (i.e. 8.3 pCi/g totaluranium). This sample location islocated inthe middle of the western portion ofSub-Area C.This sample location isNortheast ofthe UraniumProcess Building andisnotinthe path ofthe predominadt wind direction described aboveThissample location isalso notlocated nearanydrainage are.Sample results on100mx 100mgrid points surrounding thissample location areall lessthanl6.7 pCi/g total uranium. Based upon this investigation, indications are thatthissample restilt isduetostatistical variability.
Thesample location 550N-150E (9.8 pCi/g totaluranium) inSub-Area D isabove the critical value (i.e. 8.3pCi/g total uranium). This sample!location isnorth ofthe bermed area which is located along the southern boundaries ofSub-Aras C,D,andE.This sample location isdirectly North oftheUranium Process Building which ispn the path ofthe predominant winddirection described above. sample This location isalso approximately 50meters north ofthe bermed drainage area discussed above. Additional soil simples were taken inthe immediate vicinity of this elevated sample location. l l
Additional soilsamples werecollected atfour lo$ations around theoriginal sample location and again atthe original sample location. A Global Itositioning System wasutilized toensure the i
g I
accurate location ofthese sample locations. Thedverage for the five surface samples was7.8 pCi/g total uranium. Theresults ofthis samplingbffort are summarized Table below in 4:
Tabl4 S.angp.Le.Lo.ta.tigj1 b 550N-150E 7.9 pCi/g 550N-148E 8.7 pCi/g 552N-150E 6.9 pCi/g 550N-152E / 6.9 pCi/g 548N-150E 8.5 pCi/g Overall Average j 7.8 pCi/g Aslisted inTable 4above, the average concentrationfor the samples taken inandaround sample location 550N-150E isbelow the "Critical Value"l(i.e.
8.3 pCi/g total uranium). Theresampling ofsample location 550N-150E resulted inaconce trationof 7.9 pCi/g total uranium. Also, it should benoted that noneofthe samples exceede 25%oftheguideline value plus background (i.e.,11.5 pCi/g) for totaluranium. Sample analy sresultsfromthe two closest sample locations approximately 100meters north ofsampelocation 550N-150E were 4.8 and'3.2 pCi/g total uranium respectively. Based upon thisadditinal characterizationdata, Cimarron Corporation believes that thislocation containslow-levels oftotal uranium at the upper activity range for the sitebackground distribution. Intheventthat this sample contains total uranium duetosite operations, the contamination wouldmpst likelyhave been aresult ofairborne deposition 50meters and south notdrainage ofthis sample from contaminated location arjas, isdiverted asthe east drainage bywayofthe area berm.
located approximately j
1
,m 9
. i