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) | |
Text
,.
CIMARRON ORPORMION P.O,BOx25861OKLAHbA CITYOKLAHOMA 73125 S JESSLARSEN VICEPRESIDE NT November 13,1995 Mr.Michael F.Weber
- Chief, Low-Level Waste Management j
andDecommissioning Projects Branch Division ofWasteManagement l
Office ofNuclear Material Safety andSafeguardp U.S.Nuclear Regulatory Commission Washington, DC 20555-0001 1
Ref: Docket No.790925, License No SNM-928 NRCcomments(dated Septem er5,1995)on Cimarron Corporation's July, 1995"Final Status Survey Reprt,PhaseIAreas at theCimarron Facility"
DearMr.Weber:
l Thepurpose ofthis letter istorespond totheNR commentspertaining toCimarron Corporation's
.)uly, 1995"Final Status Survey
- Report, Phase I
easattheCimarron Facility".
For clarification, wehaveincluded theNRC'scommentsfollowe bytheCimarron Corporation response.
Based upontheresults oftheoriginal report andtheadditional investigation and reassessment as requested byNRCandcontained
- herewith, Cim onCorporation requests that theNRCissue a license amendment torelease thePhase ISub-Ar as(Sub-Areas CandEasamended herein) from License SNM-928.
Please contact meifthere areanyadditional queptions orconcems,orifwecanbeofanyfurther assistance.
Sincerely, Jess Larsen l
VicePresident l
jiI11395.le I
ASUBSIDJARY OFKERR-MCGEE CORPORATION
NRCCOMMENT #1:
Thereport doesnotindicate which samplescontain uranium orthorium inconcentrations that are statistically above background.
Please providealist oftheresults that arestatistically above background.
CIMARRONRESPONSE:
TheFinal Status Survey Report forPhase IAreas did notprovide alist ofsample results which contained uranium orthorium inconcentrationswhich were statistically above background because theNRCapproved Final Status Survey Planfor Unaffected Areas(i.e.
Phase ISub-Areas) stated that sample results would becompared to25% oftheguidelinevalue plus background (i.e.
11.5pCi/g fortotal uranium andj 4pCi/gfor total thorium). Asstated onpage 10oftheFinal Status Survey Report forPhase I
eas,"Foran unaffected area,NUREG-5849 recommends reclassifying anunaffected areaif yindividual sample result exceeds 75%ofthe guideline value(i.e.
22.5pCi/g total uranium ab vebackground forBTP Option #1material)",
IntheNRC'sMay1,1995response toCimarron Corporation's Final Status Survey Planfor Unaffected
- Areas, theNRCrecommended thefolowing:
"Inlieu ofreclassifying theentire area ifasample exceeds 75%ofthelimit, thestaff w uldaccept acommitment toinvestigate any individual sample result exceeding 25%oftheliit".
Inaccordance withthis recommendation, Cimarron Corporation committed tofurther investigate anysample location with concentrations exceeding 25%oftheguideline value plus background (i.e.
7.5pCi/g
+4.0pCi/g
= 11.5pCi/g total uranium) byletter toNRCdated March24,'1995.
This approach wasapproved bytheNRC byletter toCimarron Corporation dated May1,li995.
Therefore, anysample results which indicated uranium orthorium concentrations above 25%oftheguideline value plus background wereinvestigated further.
Asdiscussed onpage22oftheFinal Status Survey Report for PhaseIAreas,only onesample obtained fromthefive Unaffected Sub-Areas conltained atotal uranium concentration inexcess of25%oftheguideline value(12.4 pCi/g total uljanium atgridlocation 700N-400E).
Asalso discussed intheReport, this sample location wasjfurther characterized through thecollection of additional samples atonemeterdistances fromthis sample location.
Allofthese additional samples wereanalyzed andnoneofthese samples contained total uranium concentrations in excess of25%oftheguideline value plus backgr und.
Asdiscussed intheresponse toNRCComment
- below, asmall section ofSub-Area C
(containing thesample result 12.4pCi/g atlocati n700N-400E) andoneother small section of l
1l
Sub-Area Ehavebeen removed fromthePhase ISub-Areas andwill beaddressed later under Phase II oftheFinal Status Survey.
Noneofthesamples taken fromthefive Unaffected Sub-Areas contained total thorium concentrationsin excess of25%oftheguideline value (i.e.,
2.5pCi/g
+ 1.2pCi/g
= 3.7pCi/g total thorium).
As no sample results contained total thorium concentrations inexcessof25%of theguideline value,no further evaluations orinvestigations wereperformed byCimarron Corporation inaccordance with theNRCapproved Phase IPlan.
- However, inresponse toNRC Comment
- 1,Cimarron personnel haveperformed "Critical Value" calculations todetermine both uranium add thorium statistical background values in accordance with relationships established byJack J.DonnandRobert L Wolkein"The Statistical Interpretation ofCounting Data from Measurements ofLow-Level Radioactivity" (Health
- Physics, Pergamon
- Press, 1977, Volume
$2, (January),pp.1-14.).
These calculations wereperformed inorder todetermine whichsample(s) containeduranium and/or thorium concentrations which werestatistically above bac ground asrequested byNRC.The"Critical Value",
ascalculated
- herein, represents the95%
ean probability ofdetection atthe99%
confidence interval forthecontaminant ofconcerp.
The"Critical Value" forboththorium anduraniu wasdetermined fortheCimarron site after modification ofDonnandWolke's worktoinclude theerror associated with average site background concentrations insoil.
Thefollowing equation wasused:
r 3 2 1f c,,
c, n, c<,j c, +
aA,
+
a /
where:
Cs3andC3arethesample gross count andthebackground (i.e.,
blank) count; tseandt3arethesample counting time andthebackground counting time; naistheWhpercentile Oftheunitormal distribution, where o isthe probability ofTypeIerror; j
as+e andceareequal tothestandard deviation ofthecountsforthesample and background
(,the square ofthestandard deviation isequal tothevariance).
FortheCimarron Phase Isoil
- samples, ts+h andteAre equal to30minutes.
Setting a toavalue of 0.01results inavalue fornaof2.326.
Inaccordance withDonnandWoIke, ifthenetsample count(i.e.,
theleft handside oftheaboveequation) isgreater thantheright handside ofthe above
- equation, onecanconclude that thenetsample countrateisgreater thanzero.
Simplification oftheabove equation ispossible dtte totheequality ofthesample andbackground counttimes.
Inaddition, thegross sample andbackground countsandtheir associated standard deviation termswereassumed tobeequivalent (i.
.,Cs3
= C3andas3
= as).
Thebackground term,C3,wasmoved totheright handside ofthequation toprovide arelationship based upon thegrosssample count.Theresulting "critical vajue" equation isprovided below.Ifthegross counts(the left handside oftheequation) exceeds!
thecritical value (the right handside ofthe l
2!
equation), itcanbesaid that thesample hasasmill probability (1percent) ofbeing within the sitebackground distribution.
C
,,3
> n, [2(C 3 + o-/))
+ C,
Total thorium andtotal uranium critical values in; soil werederived bysubstituting theequivalent number ofcounts andstandard deviation forthe(verage background concentrations.
Fortotal
- thorium, average background inCimarron soil hals previously beenestablished using theon-site soil counter as1.2j-0.25 pCi/g.
Thethirty samples usedforthis average ranged from0.7pCi/g to1.7pCi/g.
Utilizing theaboveequation, the critical value foj total thorium insoil wascalculated as2.0 pCi/g.
Similar calculations for total uranium, baedupontheaverage total uranium background (4.0
+ 1.3pCi/g, range:
2.3pCi/g to6.3 pCi/g),
r sultedinacritical value fortotal uranium of 8.3pCi/g.
Thesample results fromeachofthefive Sub-Areascontained inPhase Iwerethen compared to these critical values todetermine ifanysample resultsexceeded suchvalues.
Thiscomparison does notinclude thesample results fromthe twosmall sections ofSub-Areas CandEwhich havebeenremoved fromthePhase ISub-Areas as describedin the response toNRCComment
- 2below.
Theresults ofthis "Critical Value" evaluation aresummarized belowinTable 1:
T.gtb.1e 1
Sub-ArcaW 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 AsshowninTable
- 1above, eight samplelocatiorts contained total thorium concentrations which wereabove thecritical value.
Theeight sample locations inSub-Area A whichcontained total thorium concentrations above thecritical value (ije.
greater than 2.0pCi/g) areshownbelowin Table 2withthecorresponding sample locations.)
j l
31
--,+
Lab[lel Sub-Area GridLocation Thorium Concentration A
2.1pCi/g A
300S-0E l
2.2pCi/g A
300S-100E 2.1pCi/g A
400S-100E 2.3pCi/g A
400S-200E 2.2pCi/g j
A 500S-0E 2.1pCi/g A
500S-100E 2.1pCi/g A
600S-0E 2.4pCi/g AreaAhasbeenfarmed during theentiretime priod since thefacility wasestablished.
Fertilizer hasbeenspread upontheland andwill jhave hadsomeimpact onthorium concentrations.
Inaddition, soil typehasbeensliown tohavesomeinfluence withrespect to concentrations ofnaturally occurring thorium anduranium.
Cimarroncollected tenadditional soil samples toassist intheevaluation oftheeight samples exceeding thecritical value fortotal thorium.
These samples werecollected fromac$ltivated field approximately onemilesouth of thefacility.
Thesoils collected consisted ofredelay similar to those found within SubAreaA.
- However, theadditional samples appeared tohave aslightly higher loam contentthan those from SubAreaA whichexceeded thecritical value.
Theprevious soilbackground samples were collected fromareas around thesitewith varioussoil typesrangingfrom sandy loamtoclay.
- Thus, thebackground of1.2 i0.5pCi/g (2a) repesented anaverage for the several typesofsoil found attheCimarron facility.
Forthelatest background sampling
- event, theavrage thorium background insoil was calculated as1.4i0.2pCi/g (20),
withsample results rangig from1.3pCi/g to1.6pCi/g.
This average is higher than theaverage sitewide background of1.2pCi/g.
Theeight samples taken fromSub-Area A with ttalthorium concentrations slightly abovethe critical value werecompared toconcentrations o(total Threported inNCRPandNRC documents.
Table 4.3fromthereport "Exposurelof thePopulation intheUnited States and Canada fromNatural
Background
Radiation" (NCRP Report No.94,December, 1987) lists Th-232concentrations intheaverage continental crust (from Taylor andMcLennan,1985) andin soils (from
- Lowder, etal.,1964) as44Bq/kg(1.pCi/g) and37Bq/kg(1.0 pCi/g),
respectively.
Total thorium concentrations canbeinferred bas4d uponthepresumption ofequilibrium between Th-228 andTh-232.
Concentrations oftotal ThWould range from2.0pCi/g to2.4pCi/g based upontheNCRP94data andtheaboveassumption.
Thesamples inAreaA areallwithin this range.
Draft NUREG-1501, "Background asaResidual adioactivity Criterion forDecommissioning" also provides typical concentrations forTh-232 i soils.
Table 2.2ofthereportgives theaverage Th-232 concentration inU.S.soils as36Bq/kg(
, pCi/g) with arangeof4-141Bq/kg(0.1-3.4 i
I b
I
r pCi/g)
Assuming equilibrium between Th-232 andTh-228, theaverage U.S.
soil contains 2
pCi/g total Thandranges from0.2 to6.8pCi/g.
Theconcentrations oftotal thorium inthe Cimarron Phase Iareasfall within these ranges.
Sub-Area A is both upgradient andupwind(pre ominant winddirection isfromtheSouth and Southeast) fromthe Cimarron Facility.
These eihtsamples represent less than3.5%ofthe samples obtained from thePhaseISub-Areas (i.
> 95%confidence level).
Inaddition, Total uranium concentrations in theeightsamples whihexceeded thetotal Thcritical value ranged from3.8pCi/g to6.6 pCi/g.
None oftheeight s ples contained uranium atconcentrations above thecritical value (8.3pCi/g).
Therefore, iisunlikely that thethorium activity intheeight samples wasduetoeither drainage orairborne dspersion.
Thethree sample locations which contained totauranium concentrations above thecritical value arealso showninTable 1 Specific information nthese three samples isprovided belowin Table 3.
Sub-Area GridLocation Uranium Concentration A
8.4pCi/g C
900N-500E 8.6 pCi/g D
550N-150E 9.8 pCi/g Asstated
- earlier, noPhase Isamples wereobse'edinexcess of25%ofthe guideline value(i.e.
> 11.5 pCi/g total uranium) after the twosmall sctions ofSub-Areas CandE were removed as described intheresponse toNRCComment
- 2. ub-Area A isboth upgradient and upwind (predominant winddirection isfromtheSouth a dSoutheast) fromtheCimarron Facility.
Sub-Areas CandEarebothdownwind fromtheCimrronFacility.
These three samples represent less than1.5%ofthe236samples obtained fromthe Phase ISub-Areas (i.e.
>98.5%
confidence level).
,i
NRC COMMENT
- 2:
Itappears that the areadefined approximately bylgrid locations 400E-700N to500E-700N, in Unaffected Sub-Area C,containslicensed material.
Thisisbased on1)thesample that contained 12.4 pCi/g total uranium, 2)thefour investigation samples collected around thearea containing the12.4pCi/g sample that averaged 9E4 pCi/g total
- uranium, and3)theindependent laboratory result fromthe same areathat indicated thepresence ofenriched uranium.
An investigation should beconducted todeterminethe source ofthelicensed material.
Page27ofthereport indicates that this areaisnear adrainage area.Iftheinvestigation confirms that licensed material ispresent inSub-Area Cduetodrainage fromcontaminated
- areas, the unaffected areaboundaries should bereassessed jo ensure that all site areas that could potentially receive contaminated runoff areclassified as affected.
CIMARRONRESPONSE:
Cimarron Corporation submitted thePhase IFindl Status Survey Plan for Unaffected Areas to theNRCforapproval inOctober, 1994.ThePlat wassubsequently approved bytheNRCon May1,1995.
ThePlanstated that sample resultsjwould becompared to25%oftheguideline value(i.e.
11.5 pCi/g total uranium),
andifgreater than 25%ofthe guideline
- value, further investigation wouldbeperformed.
Asdescribed intheFinal Status Survey Report forPhase
- IAreas, sample location 400E-700N hadauranium concentration of12.4pCi/g total uranium andwasfurther characterized.
Additional characterization wasperformed whicli involved sampling four locations atonemeter fromtheoriginal sample location.
Whenthefouj sample results wereaveraged with the original sample
- result, theaverage was9.4pCi/g total uraiumwith astandard deviation of2.1pCi/g.
As nosample results indicated atotal uranium concetration above 25%oftheguideline value (i.e.
11.5pCi/g total uranium),
nofurther investigatiot wasperformed.
(This istheareacontained within Sub-Area C which wasdescribed ascontajning licensed material intheNRCComment#2 listed above).
Cimarron Corporation continues toassertthat allsample results fromthePhase IUnaffected Sub-Areas meettheclean-up criteria asapproved jby theNRCintheFinal Status Survey Planfor Unaffected Areas.However, asrequested bytheNRCinComment#2above, Cimarron Corporation hasperformed additional investigations todetermine thepotential forlicensed material tobepresent inUnaffected
- Areas, withaj particular emphasis being placed on Unaffected Areaboundaries possibly impacted bjdrainage fromcontaminated areas.
These investigations, aswell astheresults ofthese invetigations, arediscussed below:
A detailed investigation
/review wasconducted vCimarron Corporation todetermine ifthere wereanypreviously unidentified drainage waysthpacting unaffected areaboundaries which could havepotentially received run-off from anaffected area.
TheCharacterization
- Report, 6!
I
l USGS maps, aerial photographs, andother historlcal documents werereviewed.
Additional site investigations wereperformed toevaluate anydrainage areas impacting unaffected
- areas, aswell asanypotential affected areas located upgradient jfrom such drainage areas.
A review ofthe Cimarron site topography indicat sthat thepredominant drainage wayshave been identified and designated aspotential affect dareas.
These areas wereidentified inthe Cimarron Decommissioning Plan andtheCimarr nRadiological Characterization
- Report, and arescheduled tobeaddressed duringthePhase IIFinal Status Survey.
A bermed areawhich is located along the southern boundaries ofSub-Ar asC,D,andEwasbuilt manyyears agoforthe prevention ofsoil erosion and moisture control frthecultivated fields located north ofthe Cimarron Facility.
Surface water runoff from hiherelevations wasdiverted eastalong the southern boundary ofSub-Areas C, D, andEbytayofthis berm.
Notall ofthis bermed area wasoriginally included with the drainage areas dscussed intheDecommissioning
- Plan, Characterization
- Report, and/or other submittals uetothefact that this wasconsidered tobean unaffected area.
j l
Uponfurther investigation andreview ofthis berped area, itwasdetermined that Sub-Area C
contained asmall section north ofthepredominapt drainage way,butsouth oftheberm.This section ofSub-Area Ccontains thesample locati$n 400E-700N.
Itwasdetermined that under extremerainfall
- events, this section could haverdceived run-off from thepredominantdrainage arearunning eastalong thebaseoftheoutcroppijgs.
Aninitial attempt wasmadebyCimarron Corpor tion toperform additional characterization in thegeneral areaofgrid location 400E-700N.
- Hovever, this portion ofSub-Area Cisfrequently muddyandcontains significant undergrowth.
T spresented significantoperational obstacles with respect toperforming additional characteri tion efforts inthis area l
Oneother location wasidentified inSub-Area E thich could potentially have received runoff from anaffected arealocated upgradient tothis 1.cation.
Thissection ofSub-Area E is located just westofBurial Area#2.
Asaresult ofthis investigation, Cimarron Corporation hasdecided toremove asmall section (which includes sample locations 400E-700N and500E-700N) fromSub-Area Candanother small section fromSub-Area E.Cimarron Corpotation continues toassert that these areas are unaffected
- areas, butwill defer addressing these areas until further characterization canbe completed.
Cimarron Corporation will address tljese twosmall sections under thePhase IIFinal Survey.
Cimarron Corporation hasconfirmed that allother drainage wayshavebeenpreviously identified andaddressed inother license submis.Drawing No.95MOST-RF3 (Rev2)is attached andshows thetwosmall sections which havebeenremoved fromSub-Areas CandE.
Asdiscussed above intheresponse toNRCCom ent#1,Cimarron Corporation performed a
"Critical Value" evaluation todetermine which smple(s) contained uranium concentrations which werestatistically above background.
Thevaluation wasperformed using thesoil sample datacollected forthefinal release ofthefive SubAreaswiththetwosmall sections fromSub Areas CandEremoved.
The"Critical Value" fototal uranium wasdetermined tobe8.3pCi/g
for average Cimarronsite soils.
Three sample locations contained total uranium concentrations above the "Critical Value".
Oneofthesample lqcations wasinSub-Area A,another wasinSub-Area C, and theother wasinSub:Area D.These three samples arelisted inTable
- 3above, along with theirrespective grid locations.
Nosample lpcations wereobserved withtotal uranium concentrations above the"CriticalValue" inSub[Areas B andE.
l Cimarron Corporation also reassessed eachofthsethree sample locations todetermine ifa potential existed for licensed material tobeprestduetoairborne emissions during facility operations orifthe sample analysis resultsappeak tobeduetostatistical variability.
A review ofthehistorical windrose datafortheimarron facility (1945 through 1990) reveals a
prevailing winddirection from theSouth andSo5theast(Wind Rose
- Oklahoma
- City, Oklahoma Climatological survey
- data, WSFO).The wind tpicallyoriginates outofthesouth and southeast for tenmonths outofthe year.Thus, ahy elevatedsample locations totheNorth and Northwest oftheUranium Building couldhave heenaffectedbyairborne stack emissions from theUranium Facility during operations from196$through 1976.
Thesample location 600S-100E (8.4 pCi/g total (tranium) inSub-Area A isslightly above the critical value (i.e.
8.3pCi/g total uranium).
Thislsample location isnearthesouthwest corner of thesite property andcould nothavebeenaffected bydrainage from contaminated areassince this areaisupgradient tothefacility.
This sample location isalsopredominantly upwind (i.e.
south) oftheUranium Process Building andisapproxinkately 0.5 milesfrom thenearestaffected area.
Sample results on100mx100mgrid points surrdunding this sample location areall less than6.6 pCi/g total uranium.
Based uponthis investigation, indications arethat this sample result isdue tostatistical variability.
Thesample location 900N-500E (8.6 pCi/g total pranium) inSub-Area Cisalso slightly above thecritical value (i.e.
8.3pCi/g total uranium).
This sample location islocated inthe middle of thewesternportion ofSub-Area C.Thissample location isNortheast oftheUraniumProcess Building andisnotinthepath ofthepredominadt winddirection described aboveThissample location isalso notlocated nearanydrainage are.Sample results on100mx100mgrid points surrounding this sample location arealllessthanl6.7 pCi/g total uranium.
Baseduponthis investigation, indications arethat this sample restilt isduetostatistical variability.
Thesample location 550N-150E (9.8 pCi/g total uranium) inSub-Area D isabovethecritical value(i.e.
8.3pCi/g total uranium).
Thissample!location isnorth ofthebermed areawhichis located along thesouthern boundaries ofSub-Aras C,D,andE.This sample location isdirectly North oftheUranium Process Building whichispn thepathofthepredominant winddirection described above.
Thissample location isalsoapproximately 50metersnorth ofthebermed drainage areadiscussed above.
Additional soil simples weretaken intheimmediate vicinity of this elevated sample location.
ll Additional soil samples werecollected atfourlo$ations around theoriginal sample location and again attheoriginal sample location.
A Global Itositioning System wasutilized toensurethe i
g I
accurate location ofthese sample locations.
Thedverage forthefive surface samples was7.8 pCi/g total uranium.
Theresults ofthis sampling bffort aresummarized belowinTable 4:
Tabl4 S.angp.Le.Lo.ta.tigj1 b
550N-150E 7.9pCi/g 550N-148E 8.7pCi/g 552N-150E 6.9pCi/g 550N-152E
/
6.9pCi/g 548N-150E 8.5pCi/g Overall Average j
7.8pCi/g Aslisted inTable
- 4above, theaverage concentrationfor the samples taken inandaround sample location 550N-150E isbelow the"Critical Value"l(i.e.
8.3 pCi/g totaluranium).Theresampling ofsample location 550N-150E resulted inaconce tration of 7.9 pCi/g total uranium.
- Also, it should benoted that noneofthesamples exceede 25%oftheguideline value plus background (i.e.,
11.5pCi/g) fortotal uranium.
Sample analy sresults fromthe two closest sample locations approximately 100meters north ofsampelocation 550N-150E were 4.8and'3.2 pCi/g total uranium respectively.
Based uponthis additinal characterizationdata, Cimarron Corporation believes that this location contains low-levels oftotal uraniumat the upper activity range forthesite background distribution.
Intheventthat this sample contains total uranium duetosite operations, thecontamination would mpst likely havebeen aresult ofairborne deposition andnotdrainage fromcontaminated
- arjas, asthedrainage arealocated approximately 50meterssouth ofthis sample location isdiverted eastbywayoftheberm.
j 1
,m 9
i