ML16352A000
| ML16352A000 | |
| Person / Time | |
|---|---|
| Site: | Texas A&M University |
| Issue date: | 12/16/2016 |
| From: | Mcdeavitt S Texas A&M Univ |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2016-0063 | |
| Download: ML16352A000 (37) | |
Text
Nuclear Science Center 1095 Nuclear Science Road, 3575 TAMU College Station, TX 77843-3575 Tel. (979) 845-7551 1
NUCLEAR SCIENCE CENTER Dr. Sean M. McDeavitt Director, TEES Nuclear Science Center Texas A&M University Texas A&M Engineering Experiment Station 1095 Nuclear Science Road, 3575 TAMU College Station, TX 77843-3575 December 16, 2016 2016-0063 Docket Number 50-59 / License No. R-23 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Ref: 10 CFR 50.90
SUBJECT:
Final Status Survey Report for the Zachry Engineering Center in support of the November 21, 2016 License Amendment Request for AGN-201M Facility License No.
R-23, Docket 50-59 Attn:
Mr. Alexander Adams Jr., Chief, Research and Test Reactors Branch Office of Nuclear Reactor Regulation Mr. Patrick M. Boyle, Project Manager, Research and Test Reactors Branch Office of Nuclear Reactor Regulation By letter dated November 21, 2016, Texas A&M University (TAMU) submitted a license amendment request (LAR) to Operating License No. R-23, Docket 50-59 seeking U.S. Nuclear Regulatory Commission (U.S. NRC) approval for the unrestricted release of the Zachry Engineering Center located on the TAMU Campus. The Zachry Engineering Center is a currently-licensed location for the AGN-201M reactor. The approval of this LAR will result in the removal of the Zachry site from the R-23 license.
In the LAR, TAMU committed to supplement the November 21, 2016 application with summary results of the radiological surveys conducted in the Zachry Engineering Center to justify the unrestricted release. Enclosure 1 presents a detailed summary of the final status survey results. The survey results demonstrate that radiological conditions in the Zachry Engineering Center satisfy TAMU policy and U.S. NRC criteria contained in 10 CFR 20, Subpart E, for future unrestricted uses of the facility.
Should you have any questions regarding the LAR, please contact me or Mr. Jerry Newhouse at (979) 845-7551 or via email at mcdeavitt@tamu.edu or newhouse@tamu.edu.
Nuclear Science Center 1095 Nuclear Science Road, 3575 TAMU College Station, TX 77843-3575 Tel. (979) 845-7551 2
NUCLEAR SCIENCE CENTER Oath of Affirmation I declare under penalty of perjury that the foregoing is true and correct to the best of my knowledge.
Sincerely, Sean M. McDeavitt, PhD Director, TEES Nuclear Science Center Submitted with Level 2 Delegate Authorization from Dr. Yassin Hassan in letter dated February 8, 2016 (ADAMS Accession No. ML16043A048)
- Final Status Survey Report for the Zachry Engineering Center CC: next page
Nuclear Science Center 1095 Nuclear Science Road, 3575 TAMU College Station, TX 77843-3575 Tel. (979) 845-7551 3
NUCLEAR SCIENCE CENTER cc:
William Dean, Office Director United States Nuclear Reactor Commission Office of Nuclear Reactor Regulation Michael Young, President Texas A&M University 1246 TAMU College Station, TX 77843-1246 Dr. M. Katherine Banks, Vice Chancellor and Dean Dwight Look College of Engineering 3126 TAMU College Station, TX 77843-3126 Dr. Yassin Hassan, Department Head, Nuclear Engineering Texas A&M University Nuclear Engineering Department 3133 TAMU College Station, TX 77843-3133 Dr. John Hardy Reactor Safety Board Chairman Texas A&M University 3255 TAMU College Station, TX 77843-3255 Dr. Latha Vasudevan Radiological Safety Officer, Texas A&M University Environmental Health and Safety 1111 Research Parkway College Station, TX 77843-4472 Jerry Newhouse NSC Assistant Director Texas A&M Engineering Experiment Station 3575 TAMU College Station, TX 77843-3575 Scott Miller NSC Manager of Reactor Operations Texas A&M Engineering Experiment Station 3575 TAMU College Station, TX 77843-3575 Jeremy Osborn AGN-201M Reactor Supervisor Texas A&M University Nuclear Engineering Department 3133 TAMU College Station, TX 77843-3133
Nuclear Science Center 1095 Nuclear Science Road, 3575 TAMU College Station, TX 77843-3575 Tel. (979) 845-7551 4
NUCLEAR SCIENCE CENTER ENCLOSURE 1 TEXAS A&M UNIVERSITY FACILITY LICENSE R-23, DOCKET NO. 50-59 OPERATING LICENSE AGN-201M REACTOR FINAL STATUS SURVEY RESULTS:
ZACHRY ENGINEERING CENTER
FINALSTATUSSURVEYREPORT:
ZACHRYENGINEERINGCENTER AGN201MREACTORAREAS TEXASA&MUNIVERSITY COLLEGESTATION,TEXAS
December15,2016
Preparedby:
ReNukeServices,Inc.
710S.IllinoisAve.,SuiteF104 OakRidge,Tennessee37830
PreparedBy
12152016
ReNukeServices Date
Contents 1.0 EXECUTIVE
SUMMARY
....................................................................................................2
2.0 INTRODUCTION
...............................................................................................................2 3.0 PURPOSEANDSCOPE......................................................................................................2 4.0 SITEDESCRIPTION...........................................................................................................3 5.0 RADIOLOGICALCONTAMINANTSANDCRITERIA..........................................................6 6.0 IMPACTEDAREASANDSURVEYUNITS..................................................................................10 7.0 SURVEYAPPROACH................................................................................................................11 7.1 General..................................................................................................................11 7.2 SitePreparation.......................................................................................................11 7.3 IntegratedSurveyStrategy.....................................................................................11 7.4 SurveyInstrumentation..........................................................................................11 7.5 SurfaceScans.........................................................................................................14 7.6 StaticSurfaceActivityMeasurements...................................................................14 7.7 RemovableContaminationMeasurements..........................................................15 7.8 SamplesandAnalyses...........................................................................................15 7.9 QualityAssurance/QualityControl.........................................................................15 7.10 DataEvaluation......................................................................................................15 8.0 SURVEYUNITS..............................................................................................................16 9.0 ISOLATIONANDCONTROL...22 10.0 REPORT....22
11.0 REFERENCES
................................................................................................................22
APPENDIXA-MEASUREMENT&DETECTIONSENSITIVITIES.................................................A1 APPENDIXB-GRIDLAYOUTS(FIELDDRAWINGS)..................................................................B1
1
ACRONYMSANDABBREVIATIONS
ALARA AsLowAsisReasonablyAchievable C
carbon cm centimeter cm2 squarecentimeter cpm countsperminute Cs cesium dpm disintegrationsperminute Eu europium 3H tritium hr hour keV kiloelectronvolt m
meter m2 squaremeter MARSSIM MultiAgencyRadiationSurveyandSiteInvestigationMDC
minimumdetectableconcentration MDCR minimumdetectablecountrate MeV millionelectronvolts pCi picocurie pCi/g picocuriepergram PuBe plutoniumberyllium(neutronsource)
RSSI RadiationSiteSurveyandInvestigation TAMU TexasA&MUniversity TDSHS TexasDepartmentofStateHealthServices U
uranium U.S.NRC UnitedStatesNuclearRegulatoryCommission Ci microcurie
2
FINALSTATUSSURVEYREPORT ZACHRYENGINEERINGCENTER AGN201MRESEARCHREACTORFACILITY TEXASA&MUNIVERSITY,COLLEGESTATION,TX
1.0 EXECUTIVE
SUMMARY
AspartoftheTAMUrenovationandexpansionoftheZachryEngineeringCenter,theAGN201M reactor(U.S.NRCFacilityLicenseR23)hasbeendefueled,packagedandplacedinsecureoffsite storage,andisawaitingreinstallationinanewfacility.ThePart50licenseofrecord(R23)isnotbeing terminatedbuthasbeenamendedtoreflectthecurrentstoragearrangements.Associatedmaterials andequipmentpreviouslyinthereactorfacilityhavebeensurveyed,removed,anddispositionedin accordancewiththeTAMUreleasecriteria.Extensiveradiologicalsurveyshavebeenconductedin accordancewithaFinalStatusSurveyPlan,revisedindocumentdatedNovember10,2016(ADAMs AccessionNumberML16316A002).Noradioactivesurfacecontaminationhasbeenidentifiedandno neutronactivationofthebuildingstructureshasbeendetected;asummaryofsurveyandsampling dataispresentedinsection5,RadiologicalContaminantsandCriteria.Baseduponthesurveyresults relativetothe60Coscreeningvaluesselectedfortheproject,TAMUconcludestheformerreactor areasoftheZachryEngineeringCentermeettheapplicablereleasecriteriapresentedinSubpartEto 10CFR20,CriteriaforLicenseTermination,andrequestsunrestrictedreleaseoftheseareasfrom LicenseR23controls.
2.0 INTRODUCTION
Extensive alpha and beta surface contamination surveys were conducted using gas proportional detectors and swipes were collected and evaluated, all in accordance with the FSS Plan. No contamination over background was detected. Concrete samples from shield blocks previously positionedaroundthereactorsupportskirt,fromwallsinthereactorroom,andfromthefloordirectly underthereactorwerecollectedandsubmittedforanalysesbyanoffsitelaboratorytoconfirmno neutronactivationproductsarepresentatlevelsofconsequence.Noactivationproductshavebeen detected, with minimum detectable concentrations all less than 10% of the NUREG 1757 (Ref 1) screeningvaluesdevelopedforsoilcontamination.Thesoilscreeningvaluesweredirectlyapplicable, asdemolitionofablockwallwasnecessaryforremovalofthereactorshieldtank.
3.0 PURPOSEANDSCOPE
ThepurposeofthereleasesurveysistodemonstratethatareasoftheTexasA&MUniversityZachry Engineering Center that previously housed the AGN201M reactor and associated facilities satisfy criteriaoftheNuclearRegulatoryCommission,TexasDepartmentofStateHealthServices,andTexas A&M University Radiological Safety, Environmental Health and Safety for unrestricted release. By satisfyingthesecriteria,theremainingstructurecanbedemolishedorreusedwithoutradiological restrictions.
3
TAMUhasusedtheScreeningLimitsfor60Co,aspublishedinNUREG1757,Volume2,Consolidated DecommissioningGuidance,asupperlimitsfortheprojecttocomplywiththerequirementsof10CFR 20.1402, radiological criteria for the unrestricted release. In accordance with this rule, the site is consideredacceptable for unrestricted use if the residualradioactivity that is distinguishable from backgroundradiationresultsinatotaleffectivedoseequivalent(TEDE)toanaveragememberofthe publicthatdoesnotexceed25mrem(0.25mSv)peryear.Nocontaminationhasbeendetectedonany surfacesorcomponentsduringextensiveFinalStatusSurveys.Theseresultsareconsistentwithsurveys conductedinsupportofdefuelingandduringearlierscopingsurveys.
Site characteristics support the use of these values, as only superficial surface contamination was deemedtobepotentiallypresent.Inaddition,therearenoburiedpipesorpotentiallycontaminated structures,andnounusualradionuclideshavebeenidentifiedorconsideredlikely.Thescreeningvalues havebeendeterminedbytheU.S.NRCtobeALARA;nofurtherpathwaysevaluationsarerequired (AppendixNtoNUREG-1757,Volume2).TAMUsselfimposedreleasecriteriaaremorelimiting (contaminationisnottoexceedtwicebackground,usingappropriateinstrumentation),asexplained below.
4.0 SITEDESCRIPTION
Figure1isasitemapoftheTexasA&Mcampus,indicatingthelocationoftheZachryEngineeringCenter onBizzellStreetnearUniversityDrive.TheAGN201Mreactor(Fig.2)wasdesignedandinstalledasa fullyselfcontainedunit,withnoexternalcoolantorsampleirradiationsystems.ItwaslocatedinRoom 61Bonthegroundfloor,inthesouthwestportionofthebuilding(Fig.3).Themaximumauthorized steadystateoperatingpowerlevelforthereactoris5watts.Thereactordidnotoperateforseveral yearspriortodefuelingandremovalfromthebuilding.ThedesignoftheAGN201Mreactorprecluded thepossibilityofgroundwaterorsoilcontamination,astherearenoexternalcoolantpumps,heat exchangers,coolantmakeup/cleanupsystems,ornoexternalirradiationloops.Inaddition,thebasic designeliminatestheneedforradioactivewasteprocessingsystems(e.g.,nowastecompaction,liquid wastetreatment,orcontaminatedoffgastreatmentsystems).Accordingly,theFSSPlandidnotaddress soilorgroundwatersampling.
Room60Cwasprimarilyusedforofficespaceandaccesscontrol.Room61Awasusedinsupportof reactoroperations(e.g.,safeguardslaboratorywork,experimentpreparation).Room61Bcontained thereactorcontrolconsoleandasmallinnerroomwhereradioactivesourceswerestored.Accessto thetopofthereactorwasthroughRoom135(Fig.4)onthe1stfloorlevel,directlyabovethereactor room. Rooms 60C, 61A, 61B, and room 135 (which previously contained three ion accelerators) constitutetheprimarysitesecurityboundariesforthereactor.Figures3and4showthelayoutsofthe reactorfacility;boldedoutlinesindicatePrimaryReactorSiteboundaries.
Duringnormalpoweroperation,ventilationforthereactorareawasprovidedbyaventilationfanthat pulled air through a grated opening in the Room 61B ceiling and into Room 135. Portions of the ventilationsystemductexternaltothereactorfacilityweresurveyedinearly2016during laboratory facilitysurveys,andfoundtomeettheapplicablereleasecriteria.
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Figure1.MapofTexasA&MCampus,indicatinglocationofZachryEngineering
5
Figure2.CutawayView(left)andphoto(right)ofAGN201MReactor
Figure3 Reactor Facility Ground Floor; Bolded outline indicates SecurityBoundaryandareassubjecttoFinalStatusSurveys
Sampled exterior block wall
27 ------------
48 --------------------
High density interior block walls
6
Figure4.ReactorFacilityFirstFloor;BoldedoutlineindicatesprimarySecurityBoundaryandareas subjecttoFinalStatusSurveys
5.0 RADIONUCLIDECONTAMINANTSANDCRITERIA
AGN201MreactoroperationsintheZachryEngineeringCenterbeganin1972andconcludedin2014.
RecordsandanecdotalinformationfromtheformerSeniorReactorOperatorhavenotrevealedany reactorincidentsoroccurrenceswhichmayhaveresultedincontaminationofsurfacesexternalto thereactorshieldtank.SurveysperformedbytheTAMURadiologicalSafetystaffdidnotidentifyany detectable removable contamination on reactor components or reactor room surfaces. Recent scoping surveys did not detect any fixed or removable contamination on surfaces in potentially impactedrooms.Consideringthelowpowerlevelandlimitedoperatingtime,thelowneutronfluence rate,inherentshieldingprovidedbythereactorcomponentsandcontainmenttank,andthedecay time since last operation, the likelihood of detectable activity in facility structural media was considerednegligible.
Conservative bounding calculations estimate 152Eu (likely the predominant activation product in concrete)specificactivityintherangeof103pCi/ginconcreteshieldblocksthatwerelocatedaround thereactorsupportskirt.Samplingandanalyseswereconductedtovalidatethecalculationbased conclusionthatnoactivationproductsarepresentatdetectablelevels.Candidateradionuclidesfor concrete activation include 152Eu, 154Eu, 60Co, 134Cs, 3H, and 14C. Laboratory analyses (gamma spectrometryandliquidscintillationcounting)ofsamplesaresummarizedinTable1.Samplesincluded coresfromfourinnermostshieldblocksfromthereactorskirt,onecorefromthereactorroomwall acrossfromthenorthgloryhole(areactoropening),Threecoresfromthesouthblockwallinlinewith
48 ---------------------------
27 -------------
7
Table1.
VolumetricSampleData (SampleswereanalyzedbyGeneralEngineeringLaboratoriesofCharleston,S.C.)
134Cs,pCi/g 60Co,pCi/g 152Eu,pCi/g 154Eu,pCi/g 3H,pCi/g 14C,pCi/g
Result (uncertainty)
MDC Result (uncertainty)
MDC Result (uncertainty)
MDC Result (uncertainty)
MDC Result (uncertainty)
MDC Result (uncertainty)
MDC Wall:hallway(noneutronirrad.)
2.17E02 (3.05E02) 5.82E02 9.05E03 (4.07E02) 7.23E02 8.93E04 (6.84E02) 1.12E01 5.03E02 (8.19E02) 1.73E01 4.54E01 (3.08) 5.43E+00 3.5E01 (8.15E01) 1.41E+00 Wall:Nside,oppgloryhole 1.58E02 (4.87E02) 8.97E02 5.32E03 (5.28E02) 9.91E02 8.47E02 (1.28E01) 1.90E01 7.42E02 (1.54E01) 2.97E01 2.24 (3.01) 5.44E+00 4.78E01 (7.88E01) 1.37E+00 S.Wall1:IW1(wallremoved) 5.74E04 (2.75E02) 4.77E02 6.36E03 (2.22E02) 4.30E02 1.44E02 (5.56E02) 1.09E01 1.65E02 (5.1E02 1.01E01 2.11 (4.23) 7.63E+00 3.68E01 (3.73E01) 6.26E01 S.Wall2:IW2(wallremoved) 2.84E03 (2.03E02) 4.52E02 1.24E03 (1.62E02) 4.11E02 1.2E02 (7.1E02) 1.40E01 5.85E02 (7.39E02) 1.30E01 1.58 (4.38) 7.85E+00 1.33E01 (3.54E01) 6.01E02 S.Wall3:IW3(wallremoved) 3.0E02 (3.15E02) 7.01E02 1.83E03 (3.19E02) 6.72E02 4.68E02 (7.23E02) 1.29E01 7.18E02 (9.79E02) 2.26E01 3.10E01 4.61 8.08E+00 4.62E01 (3.72E1) 6.21E01 Reactorshieldblock:E1 2.91E02 (3.84E02) 7.87E02 3.16E03 (3.94E02) 7.69E02 4.82E02 (7.42E02) 1.31E01 2.03E03 (1.09E01) 2.17E01 2.26E01 (4.52) 7.96E+00 1.38E01 (3.53E01) 5.98E01 Reactorshieldblock:S1 2.98E03 (4.15E02) 8.06E02 9.55E04 (3.54E02) 7.64E02 2.08E02 (9.69E02) 1.70E01 2.81E02 (8.95E02) 1.86E01 8.24E01 (4.63) 8.07E+00 4.06E01 (3.67E01) 6.14E01 Reactorshieldblock:N1 7.06E03 (2.54E02) 5.54E02 3.98E04 (4.03E02) 7.87E02 1.16E01 (1.17E1) 1.64E01 2.8E02 (1.09E01) 1.99E01 2.78 (4.34) 7.88E+00 3.01E01 (3.61E01) 6.07E01 Reactorshieldblock:W1 2.13E03 (3.17E02) 6.01E02 2.61E02 (3.35E02) 5.80E02 4.69E03 (6.45E02) 1.30E01 1.65E02 (9.46E02) 1.84E01 9.02E01 (4.54) 8.06E+00 5.79E02 (3.53E01) 6.01E01 Reactorpadconcrete1 1.01E02 (2.76E02) 5.89E02 4.68E03 (2.55E02) 5.19E02 5.15E03 (6.32E02) 1.26E01 2.28E02 (6.52E02) 1.55E01 5.41E01 (3.47) 6.85E+00 3.06E01 (3.77E01) 6.34E01 Reactorpadconcrete2 1.65E02 (2.48E02) 5.59E02 1.91E02 (3.00E02 5.20E02 4.01E03 (5.66E02) 1.14E01 4.81E04 (6.63E02) 1.41E01 4.83E01 (2.99) 6.30E+00 2.25E01 (3.76E01) 6.35E01 Floorunderreactorpad,1 3.35E02 (6.00E02) 9.17E02 1.59E02 (3.61E02) 6.72E02 8.95E02 (8.77E02) 1.77E01 4.36E2 (8.98E2) 2.07E01 1.70 (3.45) 6.27E+00 2.35E01 (3.77E01) 6.51E01 Floorunderreactorpad,2 4.98E03 (3.45E02) 6.87E02 2.55E03 (2.21E02) 5.17E02 5.05E03 (9.56E02) 1.69E01 2.99E02 (1.06E01) 1.98E01 1.13 (3.48) 6.58E+00 3.33E01 (3.75E01) 6.30E01 Ceilingplug (ThermalColumn) 1.36E02 (1.95E02) 4.95E02 1.34E02 (1.89E02) 5.28E02 2.11E02 (5.93E02) 1.16E01 2.57E03 (5.57E02) 1.30E01 7.42E01 (3.46) 6.71E+00 3.26E01 (3.81E01) 6.40E01
Table1Notes:
ValuesarepresentedinunitsofpCi/gforeachradionuclide,foreachsample,andarethelowestvaluesdistinguishablefrombackgroundwitha95%
certaintyofdetection.
Minimumdetectableconcentrationsforeachoftheradionuclidesofinterestarelessthan10%oftheNUREG1757soilscreeningvalues.EuropiumMDCs werealso<10%oftheEPAlimitingvaluesforresidentialsoils.
Thesoilscreeningvaluesaredirectlyapplicabletotheproject,asthesouthwallofroom61Bwasdemolishedtoremovethereactortank.
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thegloryhole(thiswaswaslaterdemolished),twocoresfromtheconcretereactorpad,twocores fromtheconcretefloordirectlyunderthereactorpad,onecorefromtheoverheadconcreteshield plug,andonecorefromthewallintheaccesshallway,anareawithnosignificantneutronexposure.
Noneofthesampleswerefoundtocontaindetectableactivationproducts.
Coveringshavenotbeenappliedoveranyknownlocationofcontamination.Basedupondocumented neutron dose rates (as incorporated in facility Safety Analysis Report), the location in the facility considered mostlikely tohavebeenimpacted byreactor operationsistheconcretefloor directly beneaththereactorshieldtank.Radionuclidesintheabovetabledominatethepotentialsourceterm, andthereisnohistoryofcontaminationbyotherradionuclidesonsurfacesexternaltothereactor.
Section17.1.4ofNUREG1537establishesthefollowingcriteriatoreleasenonpowerreactorfacilities forunrestricteduse
- 1. a)nomorethan5microremperhourabovebackgroundat1mfromthesurface measured forindoorgammaradiationfieldsfromconcrete,components,and structures,or
b)nomorethan10milliremperyearforgammaemittersabovebackgroundabsorbed dosetoanyperson,consideringreasonableoccupancyandproximity(U.S. NRCletters dated March17,1981andApril21,1982).
- 2. ResidualsurfacecontaminationconsistentwithRegulatoryGuide1.86.
RegulatoryGuide1.86waswithdrawnbyU.S.NRC,effectiveAugust12,2016,howeverthe tableofacceptablesurfacecontaminationvalueshasbeenretained(seeTable2)forthe projectasthesevaluesarealsoinTexasRegulation25TAC§289.202(ggg)(6),Acceptable surface contamination levels (Ref 2), and are applicable to Statelicensed activities at TAMU.
Table2.
AcceptableSurfaceContaminationLevels Nuclidea Total Removable Unat,U235,U238,andassociateddecay products 5000 dpm/100 cm2 1000dpm/100 cm2 Transuranics,Ra226,Ra228,Th230,Pa231,Ac 227, I125,I129 100dpm/100cm2 20dpm/100cm2 Thnat,Th232,Sr90,Ra223,Ra224,U232,I126, I 131,I133 1000dpm/100cm2 200dpm/100cm2 Betagamma emitters (nuclides with decay modesotherthanalphaemissionorspontaneous fission) exceptSr90andothersnotedabove 5000dpm/100cm2 1000dpm/100cm2
- a. Wheresurfacecontaminationbybothalphaandbetagammaemittingradionuclidesexist,thelimits establishedforalphaandbetagammaemittingradionuclidesapplyindependently.
9
TheTAMUradiationsafetyprogramhasapolicyofnodetectableactivityforunrestricteduseand release.NodetectableactivityisinterpretedbyTAMUasnotexceedingtwicethebackgroundlevel (Ref3).
Nomaterialsspecificbackgroundcountratesweresubtractedduringscanningsurveysoffacilitysurfaces; ambient background counting rates were used. Note that 2step surveys were used for static measurements,asdescribedinsection7.3,IntegratedSurveyStrategy.
Thenominalambientbackgroundvalueswereusedtocalculatethesensitivityofthescanningsurveysto ensuretheyareadequaterelativetothesurfacecontaminationScreeningValuespresentedNUREG1757, AppendixH.Becausenoresidualradioactivitywasidentifiedduringextensivesurveysofthereactor, associatedcomponents,andthefacility,nospecificradionuclidesofinterestcouldbeidentified.The NUREG 1757, Appendix H surface contamination screening value for 60Co (7,100 dpm/100 cm2) was conservativelychosenforevaluationofpotentialbuildingcontamination.Table3presentsasummaryof the minimum detectable surface contamination, the U.S. NRC screening value, and the surface contaminationlevelscorrespondingtotwicethebackgroundlevels(theTAMUconstraint).
Duringscanningsurveys,netcountratesexceeding450cpmbetawereusedasscanninglimitswhenusing the126cm2detectors,or800cpmbetaforthe580cm2detector(i.e.,contaminationexceedingthe screeningvaluefor60Co).Noinstancesofelevatedscanningcountrateswereobserved.
Grossactivitysurveyslimitswereapplied(i.e.,nottoexceedtwicebackground,alphaandbetagamma activityevaluatedindependently).Also,notethatnetcountratesexceeding3cpmalphaor250cpmbeta whenusingthe126cm2detectors,or9cpmalphaor300cpmbetaforthe580cm2detector,were establishedaslimitsindicativeofcontaminationexceedingtheTAMUcriteria(twicebackground).No individualFSSmeasurementsexceededthesethresholdvaluesandnoremedialactionwasrequired.
Table3-Summarydata Detector/Application MDA (dpm/100cm2)
U.S.NRCCo60 DefaultScreening Value (dpm/100cm2)
TAMUtwice background equivalent (netdpm/100cm2) 126cm2gas proportional/scan AlphaN/A*
1500beta AlphaN/A*
7100 N/A 3000 126cm2gas proportional/static 63alpha 470beta AlphaN/A*
7100 26alpha(<MDC) 2200beta 580cm2gas proportional/scan AlphaN/A*
2280beta (fora100cm2spot)
AlphaN/A*
7100 A>2xbackground readingwillbe investigatedwitha126 cm2detector Laboratory counter/removableactivity 19alpha 90beta AlphaN/A*
710 4alpha 500beta
- Nopotentialalphaemittingcontaminantshavebeenidentified
10
MeasuredbackgroundexposurerateswithintheZachryEngineeringCenterare5to8microR/hr.Surveys confirmedthatdoseratesfrombackgroundplusresiduallicensedmaterialarenomorethan10microR/h, measured at 1 m from building surfaces, confirm compliance with the TAMU less than twice backgroundcriterion.Theobserveddoseratesarealsoconsistentwiththepreviouslynoted guidance fromNUREG1537.
6.0 IMPACTEDAREASANDSURVEYUNITS
TheMARSSIM(Ref4)defines impactedareasasthosewithapossibilityofresidualradioactivityinexcess of background levels. Radiological surveys of impacted areas are required to demonstrate that established criteriahavebeensatisfied.Nonimpactedareasarethosewithnoreasonableexpectation ofresidualcontamination;nosurveysofnonimpactedareasare required.Impactedareasareclassified astocontaminationpotentialasfollows:
Class 1: Areas that have, or had prior to remediation, a potential for radioactive contamination (based on site operating history) or known contamination(basedon radiologicalsurveys)expectedtobeinexcessof establishedunrestrictedrelease criteria.
Class 2: Areas that have, or had prior to remediation, a potential for radioactive contaminationorknowncontamination,butarenotexpectedto exceedestablished criteria.
Class3:Areasthatarepotentiallyimpactedbutarenotexpectedtocontain any residualradioactivity,orareexpectedtocontainlevelsofresidualactivity atasmall fractionoftheestablishedcriteria,basedonsiteoperatinghistory andprevious radiologicalsurveys.
Table4presentstheAGN201Mreactorfacilityimpactedareasandsurvey units. Categorizationwas basedonusehistory,previousmonitoringrecords,andscreeningsurveysconductedduringremovalof furnishings,materials,andequipmentfromthefacility.
Table4 ImpactedAreasandSurveyUnits Class Level Room(s)
Surfaces Numberof SurveyUnits Class1 Ground 61A Floorandlowerwalls 1
Ground 61B Floorandlowerwalls 1
First 135 Floorandlowerwalls 2
Class2 Ground 61Aand61B Upperwallsandceiling 1
Class2 First 135 Upperwallsandceiling 1
Class3 Ground 60C All 1
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7.0 SURVEYAPPROACH 7.1 General
Asurveyplanwaspreparedinaccordancewithguidelinesandrecommendations,presented intheMulti AgencyRadiationSurveyandSiteInvestigationManual(Ref4). Theprocessdescribedin thisreference emphasizesandincorporatestheuseofDataQualityObjectivesandData QualityAssessment,alongwith aqualityassurance/qualitycontrolprogram. Agradedapproachwasimplementedtoassurethatsurvey effortsweremaximizedinthoseareashavingthegreatest potentialforresidualcontaminationorthe highestpotentialforadverseimpactsofresidual contamination.
Trained and qualified radiological technicians conducted field measurements, following standard proceduresandusingcalibratedinstruments appropriate for detecting and measuring thepotential contaminant.
7.2 SitePreparation
Furnishings, materials and equipment were removed from the facility in accordance with TAMU RadiationSafetyProgramprocedures. Following disassembly, defueling, removal and transfer of the reactorandassociatedcomponents,drains,ducts,grates,cabletrays, etc.,wereaccessedandsurveyed.
Nominal100cm2dualphosphordetectors(LudlumInstrumentsModel4393)havebeenusedwithdual channelscaler/ratemeters(LudlumInstrumentsModel2360)forhealthphysicssurveysconductedin supportofdefuelingandcleanupwork.Backgroundandefficienciesforthesescintillationdetectorsare identicaltothegasflowproportionaldetectorsselectedforfinalstatussurveys.Useofthemodel4393 scintillation detectors was augmented with thinwindow pancake GeigerMueller detectors with scaler/ratemeters(LudlumInstrumentsModel439detectorswithModel3scaler/ratemeters)toaccess smallerdiameterpenetrations(e.g.,usedforelectriccables,watersupplylines,naturalgaslines,etc.).
Nodetectableresidual activitywasidentifiedonbuildingsurfaces,withMDCswellbelowtheU.S.NRC andTAMUreleasecriteriaaspresentedinTable2andnoremediationwasrequired.Buildingsurfaces wereappropriately griddedat1m intervals,aspracticalfortheconditions. Gridoriginsarelocatedin thesouthwestcornerofeachsurveyunit.
7.3 IntegratedSurveyStrategy
Radiologicalsurveysconsistedof:
Surfacescansforelevatedlevelsofgrossalpha,beta,andgammaradiationlevels, Staticmeasurementsofgrossalphaandgrossbetaactivity, Smearsforremovablegrossalphaandgrossbetaactivity,and Samplingforlaboratoryanalysisofspecificradionuclidecontaminants.
Table5indicatesthesurveyrigorused.Facilityoperatinghistoryandsurveysperformedinsupportof reactordisassemblysupporttheselectedgradedapproach.
12
Table5.
SurveyRigorforEachSurveyUnit Contamination SurveyClass Alpha,Beta&
GammaScan StaticAlphaandBeta Removable Alpha&Beta 1
100% all structure surfaces Systematic static measurement at a minimum of 18 locationsandatadditionallocationsof highest potentialcontamination,basedon professional judgmentandscanresults Ateachstatic measurement location 2
50%floorand lowerwalls; 10%upperwalls andceiling surfaces Systematicstaticmeasurementataminimumof 18 locationsandatadditionallocationsof highest potentialcontamination,basedon professional judgmentandscanresults Ateachstatic measurement location 3
10%floorand 1m2around eachstatic measurement locationon lowerwalls Onefloormeasurementand1lowerwall measurementper10m2offloorareaineach room,andmeasurementsandatadditional locationsofpotentialcontamination,basedon professionaljudgmentandscanresults (minimumof18datapointspersurveyunit).
Ateachstatic measurement location
Because the TAMU acceptable release criterion of twice background is very low, Scenario B, as recommendedbyNUREG1505(Ref5),isthebasisforthesurveydesign. TheNullHypothesis forthat Scenariois:
Thesurveyunitmeetsthereleasecriterion.
TheobjectiveofthereleasesurveyistoacceptthisNullHypotheses,bydemonstratingata TypeI()
decisionerrorlevelof0.05andaTypeII()decisionerrorlevelof0.025thatresidual contaminationis lessthantwicebackground. Multiplebuildingsurfacetypes (e.g.,concrete,metal,glass)arepresentin mostsurveyunitsandbackgroundlevels,particularlyradondaughters,exhibitedvariabilitybyinstrument, material, time of day, and location within the facility. To facilitate adjusting measurements for appropriatelocalizedbackgroundcontributions,apairedmeasurementapproach wasusedfor static measurements. Toperformpairedmeasurements,ameasurementwasfirstperformedbyplacinga pieceofnominal1/4inmetalshieldmaterialbetweenthesurfaceandtheLudlum4368detectorface.The staticmeasurementwasrepeatedwithouttheinterveningshieldmaterial,andthe differencebetween thesecondandfirstmeasurementisthenetcontaminationmeasurement.
Noindividualstaticmeasurementidentifieddetectableactivityinexcessoftheprojectlimits(e.g.,allnet measurementsmustbelessthanthe3alphaand250 betacpmnominalcountrates,asmeasuredwith the4368detectorsthemorerestrictiveTAMUlimits). Nostatisticaltestsarerequiredtodemonstrate compliance withreleasecriteria.
Toestablishthenumberofmeasurementsneededtodemonstratethatresidualcontamination criteria have been satisfied, a parameter known as the relative shift, which effectively describes the
13
distributionoffinalsampledata,iscalculated,asfollows:
/=(DCGLLBGR)/,
[1]
/
=relativeshift DCGLCriteria =cleanupcriteria LBGR
=lowerboundofthegrayregionandisdefinedintheDQOsas50 percent oftheDCGL. Wherefinalsampledataarenotyetavailable, MARSSIM guidance(Section5.5.2.2)assignsavalueofonehalfof theDCGLfortheLBGR.
= standarddeviationofthesampleconcentrationsinthesurveyunit.
Wherefinalsampledataarenotyetavailable,MARSSIMguidance (Section5.5.2.2)recommendsavalueof30percentoftheDCGL.
UsingtheequationforrelativeshiftandMARSSIMguidanceforsituationswherefinalsample dataare notyetavailable,therelativeshiftfordesignpurposesis(1-0.5)/0.3foravalueof1.67. Basedonthe relativeshiftof1.67andTypeIandTypeIIdecisionerrorsof0.05and 0.025,respectively,thenumber ofrequireddatapointsfromeachsurveyunittoperformthe evaluation,asobtainedfromMARSSIM guidance(Table5.5)is18.
ForstaticmeasurementlocationsonClass1andClass2 roomsurfaces,arandomstartpoint was identified on the floor and additional measurement locations were systematically selected on a triangularspacingfromthatstartpoint.Spacingdistance,L,wasdeterminedby:
L=[(SurveyUnitArea)/0.866xnumberofdatapoints]0.5
[2]
Ductwork and piping was removed, or internals were accessed, scanned, and static measurements performedattheopenendsandadditionalpointsatafrequencyof1 measurement/4m2ofinternal surfacearea.
Static measurement locations in Room 60C, the only Class 3 unit, were at locations of highest contaminationpotential,baseduponareausesandasselectedbyprofessionaljudgment.
AppendixBpresentsthegridlayoutfielddrawingsforeachsurveyunit,derivedasdescribedabove.
7.4 FSSSurveyInstrumentation
Table6isalistofradiologicalsurveyinstrumentationusedfortheAGN201Mreactorfacilitysurveys.
Theseinstrumentsaremaintained,calibrated,andoperated inaccordancewithwrittenprocedures.For applicationtounrestrictedrelease,instrument response(efficiency)isbasedonNIST-traceablesources of 99Tc(betaEMAX =292keV)and230Th(alphaE=4.68MeV). Theenergiesoftheseradionuclidesare
14
representativeofthe dominantpotentialcontaminants.Notethatthe126cm24368gasflowproportional detectorshaveefficienciesandambientbackgroundcountratesthatareidenticaltothe100cm24393dual phosphorscintillationdetectorsusedforhealthphysicssurveysduringfacilitypreparationsforrelease;survey dataaredirectlycomparable.
Table6.
InstrumentationforFinalStatusSurveys Detector Display Application Ludlum4337 Ludlum2360 Alpha/betascans Ludlum4368 Ludlum2360 Alpha/betascans Ludlum4368 Ludlum2360 Alpha/betastaticmeasurements Ludlum4310 Ludlum2929 Removablealpha/betameasurements(scaler)
Ludlum19 N/A Gammascans/directgammameasurements
Forfieldmeasurementapplications,calibrationrepresents2response.Effectsofsurface conditionson measurementsareintegratedintotheoverallinstrumentresponsethroughuse ofasourceefficiency factor,inaccordancewiththeguidanceinISO75031(Ref6)and NUREG/CR1507(Ref7). Default surfaceefficienciesof0.25foralphaemittersand0.25forbeta emitterswillbeused.
Detection sensitivities are estimated using the guidance in MARSSIM and NUREG/CR1507.
Instrumentationandsurveytechniquesarechosenwiththeobjectiveofachievingdetection sensitivities of<50%ofthecriteriaforstructuresurfaces,forbothscanninganddirect measurement.Thesedetection sensitivities assure identification of areas potentially exceeding the established project criteria.
Minimumdetectableactivitylevelsareadequatefortheproject.RefertoAppendixAforderivationof applicableMDAs 7.5 SurfaceScans HandheldLudlumModel4368gasproportionaldetectors(126cm2) usedwithLudlumModel2360 scaler/ratemeters were used for alpha and beta surface scanning to identify locations of potential residualsurface.AlargeareacartmountedLudlumModel4337gasproportionaldetector(580cm2)was usedwitha LudlumModel2360scaler/ratemetertoscanthefloorsurfaces. Thesmallerhandheld detectorwasalsousedtosurveyfloorareasnotaccessiblewiththelargerdetector.Alpha/betascanning wasperformedby maintainingthedetectorwithin1/4inofthesurfaceandmovingthedetectoroverthe surface atarateofapproximatelyhalfofthedetectorwidthpersecond,whilemonitoringtheaudible outputof thescaler/ratemeterforimmediateidentificationofincreasesincountrate. When2alpha countsaredetectedwithinapproximately2s,thedetectormovementwashaltedatthelocationfor approximately10 secondstodetectapossibleelevatedcountrate.ThisisconsistentwithAppendixJ guidanceintheMARSSIMdocument(NUREG1575).
Ambientbackgroundlevelswereusedduringscanningsurveysofthefloorsandtheremainderofthe facilitysurfaces(primarilypouredconcretewalls,steelandglass).Nomaterialsspecificbackground countratesweresubtractedfromscanningsurveysoffacilitysurfaces.
15
ALudlumModel19MicroRgammasurveyinstrumentwasusedforgammascans. Generalareagamma monitoringwasperformedwiththeinstrumentapproximately1mabovethefloor.
7.6 StaticSurfaceActivityMeasurements
StaticmeasurementsofalphaandbetasurfaceactivitywereperformedusingtheLudlumModel 4368 gasproportionaldetectorswithLudlumModel2360scaler/ratemeters.Measurementswereconducted byholdingthedetectorinpositionwithin1/4inofthe surfaceandintegratingthecountovera2min period. Two measurements, one shielded and one unshielded, were performed at each static measurementlocation,withthenetcountratebeingthedifferencebetweenthetwomeasurements, foralphaandbetadetection.
7.7 RemovableContaminationSurveys
Asmearforremovableactivitywasperformedateachstaticsurfaceactivitymeasurement location. A 100cm²surfaceareawaswipedwithanominal2indiameterclothsmear,usingmoderatepressure.
7.8 SwipeSampleAnalyses
Smearswereanalyzedonsiteforgrossalphaandgrossbetaactivitybyperforming2minuteintegrated countsusingaLudlumModel 2929scalerwithaModel43101dualscintillationdetector(orequivalent instrumentation).
7.9 QualityAssurance/QualityControl
Measurementswereperformedinaccordancewiththesurveyplanbyqualifiedpersonnel following writteninstrumentoperatingprocedures.InstrumentcalibrationpracticesmeetANSIstandardsanddaily backgroundandsourceresponsechecksofinstrumentswereperformedtoverifyconsistentacceptable operation. Forqualitycontrolpurposes,replicate staticandremovableactivitymeasurementswere obtainedat2locationsineachsurveyunit.
ARadiochemistryTechnicalCaseNarrativewasprovidedbythelaboratoryforeachsampleset,and includedaDataSummaryandQualityControlInformationrelatedtoanalyticalworkperformed.The analyticaldatareportswerereviewedandaccepted.
7.10 DataEvaluation
Surfacecontaminationmeasurementdatawasadjustedforambientbackgroundand convertedtounits ofnetcountsperminute. Datawasassessed during collection and during survey reviewstoverify consistencywiththesurveyplananddesignassumptions. Individual datapointshavebeencompared withthecountratelimitderivedfromNUREG1757surfacecontaminationscreeningvaluesfor60Coand theTAMUcriteriaoftwicebackground-nosurveypointsfailed.Becauseeachsurveypointindividually passedtheacceptancecriteria,nostatisticalevaluationofthedatasetisrequired.
16
EvaluationofvolumetricsampledatahasbeenpresentedinSection4,RadionuclideContaminantsand Criteria.Noactivationproductsweredetectedinthebuildingstructure.
Becausealloftheindividualsurveypointsmeettheconservativelyselected60Cosurfacecontamination screeningvalues,andwithnoactivationproductsdetected,TAMUfindsthatRooms60C,61A,61B,and 135meetconditionsnecessaryforunrestrictedreleasefromlicensecontrols.TheanticipatedTEDEtoan averagememberofthecriticalgroupdoesnotexceed25mremperyear,asdeterminedinthederivation oftheNUREG1757screeningvalues,andconsistentwith10CFR20,SubpartEcriteriafortermination oflicensecontrols.Inaddition,withMDCsforprincipalconcreteactivationproductall<10%ofthe screeningvalues,the10mrem/yearlimitinNUREG1537isalsometwithnofurtheranalysesneeded (theresultantdosewillnotexceed3mrem/y,witha95%confidence).
8.0 SURVEYUNITS
Asummarydescriptionandreviewofeachsurveyunitfollows.
8.1 Room61B,ReactorRoom Room61B(Fig.5)isaClass1surveyunitthatpreviouslyhousedtheAGN201Mreactor,theassociated controlconsole,andasmallsourcestorageroom.Thisisanominal66m2Class1surveyunitcomprised ofthefloorandwallsupto8feetabovethefloor.Aminimumof18staticmeasurementandswipes wererequired,asderivedusingthemethodologydescribedinsection7.3,IntegratedSurveyStrategy; 23staticmeasurementandswipelocationswereused.Allfloorandwallscanswerelessthantwice backgroundandwithinthe 60Coscreeningvalues,asweretheassociatedstaticmeasurementsand swipes.Measuredradiationlevelswerewithinbackgroundlevelsof3to5microR/h.
Figure5. Room61B,reactorroomaftereverythingwasremoved,cleanuedupandthewallresealed.
17
Noreactorprocesspipingorductworkwaspresentinthearea,astheAGN201Misaselfcontained devicewithnoexternalsampleirradiationorcoolingpipingsystems.
Twoelectricalconduits(4inand6inID)arepresentinthefloorandterminatedinsealedconnection boxesandruntotheadjacentroom(61A).Thesewereusedforreactorcontrolwiringwhenthereactor control console was located outside room 61B, but have not been used in the recent past. The terminationboxeswereopenedandsurveyed,withnodetectablesurfacecontaminationinexcessof backgroundidentified.Eachendoftheconduitwasdirectlymonitoredforsurfacecontamination,with nodetectablesurfacecontaminationinexcessofbackgroundidentified.Largeareaswipeswerepulled throughthelengthofeachofthetwoconduitsandtheclothwassurveyed;nodetectablecontamination inexcessofbackgroundwasidentified.
Afloordraininthereactorroomislocatedadjacenttothereactorpadandwaspipedtoadedicated polyethylenecollectiontank.Thiswasacontingencyforcollectionofthechromatedwaterusedfor shielding in the AGN201M outer shield tank. The system was never used. As part of the facility disassemblywork,thenominal4inPVCdrainlinewascutintoshortsectionsandtheplastictankwas sectionedtofacilitateconfirmationcontaminationsurveys.Nocontaminationoverbackgroundlevels wasdetectedonthepipesectionsorthetank.Thefloordraingrillwasremovedandthedrainbowl surveyedinplace.Aswiththeassociatedpipingandcollectiontank,nocontaminationoverbackground wasidentified.
Theformersourcestorageareaincludedthreesourcestoragewells(Fig.6),constructedusingnominal 9insidediameterironsleevesembeddedapproximately4ftintheconcretefloor.Thediameterwas sufficientlylargetopermitsurveyswiththehandheldgasproportionaldetectors.Directmeasurements ofsidesandbottomweremadeandswipeswereobtained;nodetectablecontaminationinexcessof backgroundwasidentified.
Figure6.
Sourcestoragewells.
Agrateintheceilingoverthereactorshieldtankprovidedtheonlyairflowpathwayfromtheroom.This wasnotaductedexhaust,butdischargedintoroom135(theformeracceleratorroom)throughagrate in the room 135 floor. The walls of this penetration were thoroughly surveyed; no detectable contaminationinexcessofbackgroundwasidentified.
Amultisegmentsteppedshieldplugispartoftheceilingofroom61B,andwasthoroughlysurveyed whenopenedforreactordisassembly.Itisaddressedfurtherintheroom135surveysummary.
18
Asnotedabove,allfloorandwallscanswerelessthantwicebackgroundandwithinthe60Coscreening values,asweretheassociatedstaticmeasurementsandswipes.Measuredradiationlevelswerewithin backgroundlevelsof3to5microR/h.
8.2 Room61A,safeguardslaboratory
Room61AisaClass1surveyunitthatwaspreviouslyusedforpreparationofreactorexperiments.This isanominal60m2(includingtheaccesshallway)Class1surveyunitcomprisedofthefloorandwallsup to8feetabovethefloor;theaccesshallwaywasincludedinthesurveyunit.Aminimumof18static measurementandswipeswererequired,asderivedusingthemethodologydescribedinsection7.3, IntegratedSurveyStrategy;20staticmeasurementandswipelocationswereused.Allfloorandwall scanswerelessthantwicebackgroundandwithinthe60Coscreeningvalues,asweretheassociated staticmeasurementsandswipes.
Noreactorassociatedprocesspipingorductworkwaspresentinthearea.Twoelectricalconduits(4in and6inID)areinstalledinthefloorandterminatedinsealedconnectionboxesandruntotheadjacent room(61B).Thesewereusedforreactorcontrolwiringpriortothereactorcontrolconsolebeingmoved intoroom61B.Theyhavenotbeenusedintherecentpast.Theterminationboxeswereopenedand surveyed,withnodetectablesurfacecontaminationinexcessofbackgroundidentified.Eachendofthe conduitwasdirectlymonitoredforsurfacecontamination,withnodetectablesurfacecontaminationin excessofbackgroundidentified.Largeareaswipeswerepulledthroughthelengthofeachofthetwo conduits and the cloth was surveyed; no detectable contamination in excess of background was identified.Ashortelectricalconduitpenetrationalsorunsthroughthewestwallintoroom60C,the original location of the reactor console. Each end of this conduit was surveyed with handheld instrumentation and swipes were obtained from the interior surfaces, include wiring that remains present.Nocontaminationoverbackgroundlevelswasdetected.
Radiologically unimpacted sealed cooling lines and wiring associated with former ionimplant acceleratoroperationsranfromtheoverheadroom135throughalargediameterpenetrationinthe room61Aceilingandexitedroom61Athroughawallpenetration.Thecoolinglineswereremoved, surveyedandconfirmedtobefreeofdetectablesurfacecontamination.Penetrationswereaccessible andsurveyedduringtheFSSworkinroom135.
Achemistrybenchwaslocatedinthenorthwestcornerofroom61A(Fig.7);itwasthoroughlysurveyed during scoping and characterization work, and was removed/disposed as nonradiological waste.
Utilities(naturalgas,potablewater,compressedair)andaglassdrainlinewerepreviouslyconnected tothebench.Followingconfirmatorysurfacecontaminationsurveys,theutilitylineswereterminated andremoved.Theglassdrainlinewasremovedinsectionsalongwiththetrapunderthebench.No contaminationoverbackgroundwasdetectedinthesink,thesinktrap,orconnectionjoints.Surveys includedconfirmatoryliquidscintillationcountingofsamplesbyTAMU,withnoactivity(includinglow energybetaemitters)detected.Theassociateddrainsumphadbeenpreviouslyreleasedaspartof decommissioningactivitiesassociatedwithStatelicensedadjacentlaboratories.
19
Allfloorandwallscanswerelessthantwicebackgroundandwithinthe60Coscreeningvalues,aswere theassociatedstaticmeasurementsandswipes.Measuredradiationlevelswerewithinbackground levelsof3to5microR/h.
Figure7. Room61A,safeguardslaboratory(panoramainducedcurvature).
8.3 Room60C,accesscontrolandofficearea Room60CisaClass3 surveyunitthatwasprimarilyusedforcontrollingaccesstothesafeguards laboratoryandreactorroom.Itwasalsotheinitiallocationforthereactorcontrolpanelpriortomoving itinsidethereactorarea.AsmallofficefortheSeniorReactorOperatorwasaddedwithin60Cinthe late1990s.Aminimumof18staticmeasurementsandswipeswererequired,asderivedusingthe methodologydescribedinsection7.3,IntegratedSurveyStrategy;21staticmeasurementsandswipe locationswereused.Inadditiontoprescribedstaticmeasurementsonthelowerwallsandfloor,100%
ofthefloorwasscanned.Wiringpenetrationsinthewallfromroom61Aweresurveyedprimarilyfrom room61A,withconfirmatorysurveysperformedin60C.
Aglassdrainlinefromroom135(theformeracceleratorlaboratory)ranthroughasectionofroom60C, butwasnotutilizedinanywaywithin60C.Thedrainlinewasremovedinitsentiretyaspartofthe scopingworkforroom135;noactivitywasdetectedontheinsideoroutsidesurfaces.
Allfloorandwallscanswereatbackgroundlevels,asweretheassociatedstaticmeasurementsand swipes.Measuredradiationlevelswerewithinbackgroundlevelsof3to5microR/h.
8.4 Room135,acceleratorlaboratory Room135(Figs.8and9)consistsoftwoindividualClass1surveyunitsforfloorandlowerwallsurveys, andasingleClass2surveyunitfortheceilingandupperwalls.Itwaslastusedprimarilyforionimplant acceleratorexperimentation.Italsoprovidedaccess,viaheavy,steppedconcretefloorplugs,tothe thermalcolumnatthetopoftheAGN201Mreactor.DiscussionswithTAMUstaffindicatethatthis accesspointhasnotbeenutilizedsincethelate1990s.Inadditiontothethermalcolumnaccessplug, thereisalsoanominal24inx24inpenetrationthroughthefloor,gratedatbothends,toprovideair flowfromthereactorroom(61B)totheacceleratorroom.Asinglepointventilationintakehousingwas locatedatthesouthwestcornerinroom135.Itwasequippedwithahighefficiencyparticulateair
20
filtrationcabinetandservicedbyasingleblowerontheroof.Therewasnodirectconnectionprovided forreactoroperationsinroom61B.Thefilterhousingwasthoroughlysurveyedduringearlyfacility characterization work, but no activity was identified. The throughwall exhaust penetration in the southwestcornerandthemakeupairpenetrationinthenortheastcornerwerethoroughlysurveyed; noactivityinexcessofbackgroundwasidentified.
Figure8. Room135acceleratorroom,lookingnorth.
Figure9.Room135acceleratorroom,lookingsouth.
Achemistrybenchwaslocatedinthenorthwestcornerofroom135.Itwasthoroughlysurveyedduring scopingandcharacterizationwork,andremoved/disposedasnonradiologicalwaste.Utilities(natural gas,potablewater,compressedair)andaglassdrainlinewerepreviouslyconnectedtothebench.
21
Followingconfirmatorysurfacecontaminationsurveys,theutilitylineswereterminatedandremoved fromtheirrespectivethroughwallmetalsleeves.Theglassdrainlinewasremovedinsectionsalong withthetrapunderthebench.Thedrainpenetrationranthroughroom60C;thedrainlinewasalso removedfromtheceilingofroom60C.Nocontaminationoverbackgroundwasdetectedinthesink,the sinktrap,orconnectionjoints,orinthehorizontalsectionsremovedfrom60C.Additionalsurveywork includedconfirmatoryliquidscintillationcountingbyTAMUstaffofliquidsamplesobtainedfromthe draintrap;noactivity(includinglowenergybetaemitters)overbackgrounddetected.Theassociated drainsumphadbeenpreviouslyreleasedaspartofdecommissioningactivitiesassociatedwithState licensed adjacent laboratories. Adjacent floor penetrations allowed for routing of nonradiological acceleratorcoolinglinestothelowerelevations.Thecoolinglineswereremovedandsurveyed,along withtheinteriorofthelargefloorpenetration;noactivityinexcessofbackgroundwasdetectedonthe acceleratorcoolinglinesorinsidethepenetration.
Severalelectricalconduitboxesarelocatedinthesouthwestsectionofwall.Surveysinsidetheboxes, includingswipes,didnotidentifyactivityinexcessofbackgroundlevels.
Thebuildingdesignincludedstepped,4pieceremovableconcreteshieldplugsdirectlyoverthereactor topermitaccesstoreactorsthermalcolumn(Fig.10).Theshieldplugsectionsremainedundisturbed forthelast15years,butwereremovedinSeptemberaspartofthereactordisassemblyanddefueling work.Thoroughsurveyswereperformedduringtheremovalandpriortoreassemblyoftheshield,and includeddirectandremovablesurfacecontaminationmeasurementsontheindividualshieldsections andthesteppedlandsinthefloor.Noactivityinexcessofbackgroundwasidentified.Thebottomshield closesttothereactorwasalsosampledforactivationproducts(sampleceilingpluginTable1).No activationproductsweredetected.
Figure10. Shieldplugdetails:(left)Thethirdoffourshieldplugsbeingremovedand(right)theopen floorpenetrationabovetheAGN201Mshowingsteps.
22
Alarge,3toncapacityoverheadbridgecranewasinstalledintheroom.Surveyswereconductedonthe bridgeandtrolleysteel,exposedcableonthecabledrum,andonthecranehook.Noactivityinexcess ofbackgroundwasidentified.
Aminimumof18staticmeasurementsandswipeswererequiredineachClass1surveyunit,asderived usingthemethodologydescribedinsection7.3,IntegratedSurveyStrategystatic.18measurementand swipe locations were used in each of the 2 Class 1 survey units. All floor and wall scans were at backgroundlevels,asweretheassociatedstaticmeasurementsandswipes.
Obtainingrepresentativeceilingmeasurementswasinitiallycomplicatedbybuildupofradondaughters ontheplasticlightcovers(a35minuteapparenthalflifewasnotedwhenthelampswereextinguished).
Scanningandstaticmeasurementsontheceilingweresubsequentlyperformedwiththeassociated lightingbankdeenergizedforanextendedperiodpriortothestartofsurveywork.Asaconservative measure,thenumberofstaticmeasurementsontheceiling(asingleClass2surveyunit)wasdoubled from 18 to 36, effectively mimicking the floor grids (2 Class 1 survey units). Ceiling scans, static measurements,andswipesmettheacceptancecriteria.
In summary, all floor,wall, andceiling scanswere less than twice background and withinthe 60Co screeningvalues,asweretheassociatedstaticmeasurementsandswipes.Floorshieldplugsandlands were previously (October 2016) demonstrated the meet the same criteria and closed. Measured radiationlevelsinRoom135werewithinbackgroundlevelsof3to5microR/h.
9.0 ISOLATIONANDCONTROL
FollowingcompletionoftheFinalStatusSurveys,andtheU.S.NRCdirectedconfirmatorysurveys,the facilitywaslockedandaccesscontrolledbyTAMUpendingU.S.NRCapprovalforunrestrictedrelease.
TheseareaswillnotbeavailableforgeneralaccessorworkuntilU.S.NRCapprovalforunrestricted releaseisobtained.
10.0 REPORT
This report provides a survey data summary and technical justification to demonstrate acceptable conditions for unrestricted release in accordance with criteria presented in 10 CFR 20, Subpart E, Radiologicalcriteriaforunrestricteduse.
11.0 REFERENCES
- 1. Consolidated Decommissioning Guidance Characterization, Survey, and Determination of RadiologicalCriteria,NUREG1757,Vol.2,Rev.1,U.S.Nuclear RegulatoryCommission,2006.
- 2. TexasRegulationsforacceptablecontaminationlevelsforunrestricteduse,25TAC§289.202(ggg)(6).
- 3. Radiological Safety Program Manual, Radiological Safety Environmental Health and Safety Department,TexasA&MUniversity,July2004.
- 4. MultiAgencyRadiationSurveyandSiteInvestigationManual(MARSSIM),NUREG1575 (Rev.1),U.S.
23
NuclearRegulatoryCommission,2000.
- 5. A Nonparametric Statistical Methodology for the Design and Analysis of Final Status DecommissioningSurveys,NUREG1505(Rev1)U.S.NuclearRegulatoryCommission, 1998.
- 6. Evaluation of Surface Contamination - Part 1: Beta Emitters and Alpha Emitters, ISO 75031, InternationalOrganizationforStandardization,1988.
- 7. Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various ContaminantsandFieldConditions,NUREG/CR1507,U.S.NuclearRegulatory Commission,1997.
A1
AppendixA
Measurement/DetectionSensitivitiesofSurveyTechniques
ThemethodsforcalculatingsurveydetectionsensitivitiesarepresentedinMARSSIM(Ref4)andNUREG 1507 (Ref 7). Detector parameters used in these calculation are background count rate, efficiency (instrumentresponseandsurfacecorrectionfactors),anddetectorarea.TableA1presentstypicalvalues oftheseparametersfordetectorsusedforsurveysofconcretestructuresurfacesoftheAGN201Mreactor facility.Backgroundlevelsforconcretearethehighestforsurfacemediaremaininginthisfacility,and therefore direct measurements on other media will be more sensitive than those presented here for concrete.
TableA1. TypicalDetectorParametersforSiteSurveysofConcreteSurfances
etector/
strument obeArea(cckground(cpm) etectorefficiency rfacecorrection pha ta pha ta pha ta 37 0
0 50 46 25 25 68 6
0 36 36 25 25 29 A
25 20 A
A
AlphaScans
SurfacescansforalphaactivityareconductedusingLudlumModel4337andModel4368gasproportional detectors,coupledwithLudlumModel2360scaler/ratemeters.MARSSIMrecommendstheuseofPoisson summationstatisticstoestimatetheprobabilityofdetectingasmallnumberofcountsthatmayindicate thepossiblepresenceofalphacontaminationduringarelativelyshortobservationperiod.Theequation forestimatingtheprobabilityofdetecting1ormorecountsis:
P(n>1)=1-e[((GE+B)t))/60]
[A.1]
where:
P(n>1)=Probabilityofgetting1ormorecountsduringthetimeinterval G=Sourceactivity(disintegrationsperminute,dpm)
B=Backgroundcountrate(countsperminute,cpm)
E=Detectorefficiency(counts/disintegration) t=Dwelltimeoversource(sec)
Theprobabilityofdetecting2ormorecountsisgivenby:
P(n>2)=1-(e[((GE+B)t)]/60]-((GE+B)(t))/60).e[((GE+B)t)]/60]
[A.2]
A2
Usingtheseparameters,detectionprobabilitycalculationsforacontaminationlevelof100dpm/100cm2 wereperformedforascanrateofhalfofdetectorwidthpersecond(i.e.,dwelltimesof2seconds).The probabilitiesofdetectingasinglealphacountduringa2sdwelltimeareapproximately33%forthe4368 detectorand52%forthe4337detector.Becauseofthehigherbackgroundcountrateassociatedwiththe 4337floormonitordetector,MARSSIM(AppendixI)recommendsusing2countsasascreeningvaluewhen scanningforalphacontamination.Theprobabilityofdetecting2countswiththelargerdetectorincreases to approximately 82%. Whenever a count is detected, the detector is paused over the surface for 10 secondstodeterminewhetherthereisactuallyelevatedalphaactivitypresent,inwhichcase,astatic measurementisthenperformed.A10secondpauseresultsina90%orgreaterprobabilityofidentifying the presence of alpha activity exceeding 100 dpm/100 cm2. Although the calculated scan detection probabilities may appear relatively low, it should be noted that historic records and characterization surveyshavenotidentifiedanypotentialforalphacontaminationinthisfacility.
AlphaActivityStaticMeasurements
Static measurements of alpha surface activity are performed using 4368 detectors, with the same backgroundandresponsecharacteristicsasindicatedaboveforalphascanning.Astaticmeasurementis performedbyplacingthedetectoronthesurfacefora2minuteintegratedcount.Theminimumdetectable alphacontaminationlevel(MDC)iscalculatedasfollows:
MDC=[3+4.65(BKGD)1/2]/(efficiencyfactors)(detectorarea/100)(counttime) [A.3]
Theresultingvalueisapproximately63dpm/100cm2.
BetaScans
SurfacescansforbetaactivityareconductedusingLudlumModel4337andModel4368gasproportional detectors,coupledwithLudlumModel2360scaler/ratemeters.Thedetectorispassedoverthesurfaceat a rate of 0.5 detector width/sec, while maintaining the distance from the detector to the surface at approximately0.5cm.Theaudiblesignalfromtheinstrumentismonitoredbythesurveyor.Detectable changesinthecountratearenoted,andtheimmediatearearesurveyedatareducedspeedtoconfirmthe changeinaudiblesignaland,ifapplicable,toidentifytheboundaryoftheimpactedarea.Theminimum detectablecountrate(MDCR)isafunctionofthebackgroundcountrate(BKGD)incountsperminute(cpm) andthetime(i)insecondsthatthedetectoriswithincloseproximitytothesourceofradiation.Equation 66ofNUREG1507providesthefollowingrelationship:
MDCR=d[BKGD*i/60]1/2*60/i
[A.4]
A high probability (95%) of true detection is the objective, and the survey is willing to accept a high probabilityoffalsepositivedetections(60%)withresultinginvestigations.Thevalueofdisselectedfrom Table6.1inNUREG1507tobe1.38.
Toaccountforlessthanidealsurveyperformance,asurveyorefficiencyfactor(p)of(0.5)1/2wasalso incorporatedintothefinalcalculationofbetascansensitivityasfollows:
A3
.. / /
[A.5]
Theresultingvaluesareapproximately1500dpm/100cm2forthe4368detectorandanaverageof390 dpm/100cm2forthe4337detector.Ifonlyasingle100cm2areaispresent,thescansensitivityforthe43 37detectorwouldbeapproximately2280dpm.
BetaActivityStaticMeasurements
Staticmeasurementsofbetasurfaceactivityareperformedusing4368detectors.Astaticmeasurement is performed by placing the detector on the surface for a 2minute integrated count. The minimum detectablebetacontaminationlevel(MDC)iscalculatedasfollows:
MDC=[3+4.65(BKGD)1/2]/(efficiencyfactors)(detectorarea/100)(counttime)
Theresultingvalueisapproximately470dpm/100cm2.
RemovableAlphaandBetaActivityMeasurements
Smearsforremovableactivityarecountedfor2minutesinaLudlumModel2929alpha/betacounter.The backgroundsare1alphacpmand25betacpm;4detectionefficienciesare0.25alphaand0.20beta.Using thesameequation(withoutprobeareacorrection)asabovefordirectmeasurementsyieldsremovable activityMDCsofapproximately19alphadpm/100cm2and90betadpm/100cm2.
B1 AppendixB
LayoutsCETCHESofIndividualSurveyUnitGrids (FieldDrawingsBasedUponNUREG1757Guidance)
Room60C,AccessControlandOfficeArea,SurveyClass3
B2
Room61A,SafeguardsLaboratory,SurveyClass1
Room61B,ReactorRoom,SurveyClass1 (Refertopage8forinitialroomlayout)
B3
Rooms61Aand61B,CeilingGridReactor&LaboratoryAreas,SurveyClass2
B4
Room135,AcceleratorRoom(North),SurveyClass1
Room135,AcceleratorRoom(South),SurveyClass1
B5
Room135,CeilingGrid,SurveyClass2