ML103480005

Non-Concurrence Form Sections a, B, & C for TSTF-513

ML103480005
Person / Time
Site:	Technical Specifications Task Force
Issue date:	05/17/2010
From:	Peck M NRC/RGN-IV/DRP/RPB-B
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References
Download: ML103480005 (10)

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Use ADAMS Template NRC-006 Summary IncorporationofTSTF5131intoplantspecificTechnicalSpecificationswouldresultinasignificantreductioninthemarginof safetyatsomereactorfacilities.Theproposedchangewouldpermitlicenseestooperateforperiodsuptosevendays withouttheminimumreactorcoolantsystem(RCS)leakdetectioncapabilityassumedintheLeakBeforeBreak(LBB)safety analysis.

ApprovalofTSTF513wouldalsoestablishanewagencyprecedentbyallowinglicenseestocreditTechnicalSpecification requiredRCSleakdetectionequipmentasoperablewhenthatequipmentisnotcapableofperformingtheintended safetyfunctionasdescribedintheplantsafetyanalysis.

CurrentRequirements RegulatoryGuide1.452establishesthetypicallicensingbasiscommitmentforRCSleakdetectiontomeetGeneralDesign Criteria(GDC)30,QualityofReactorCoolantPressureBoundary.RegulatoryGuide1.45,PositionC.5,establishedthe requirementthatcontainmentatmosphericgaseousradiationmonitorshavethecapabilityofdetectingaonegallonper minute(gpm)leakwhenusedforRCSleakagedetection.RegulatoryGuide1.45specifiesthatrealisticprimarycoolant radioactivitysourcetermbeusedwhendemonstratinggaseousmonitorleakdetectioncapability.Thegaseousmonitoris typicallyoneofthreeRCSleakdetectionsystemsrequiredbyTechnicalSpecification3.4.15,RCSLeakageDetection Instrumentation.3AtWestinghousePWRs,thespecifiedsafetyfunctionofthesesystemsistoprovideplantoperatorswith anearlyindicationofpotentialpressureboundaryleakagebetweenthe72hourRCSinventorybalanceintervalrequiredby TechnicalSpecificationSurveillance3.4.13,RCSOperationalLeakage.

ThemajorityofUSWestinghousePWRshavealsoincorporatedtheLBBpipefracturemechanicstechnologyintotheplant specificdesignbases.4TheLBBtechnologyprovidedthebasisforreducingthenumberofRCSpipingsupports,resolutionof UnresolvedSafetyIssueA2,AsymmetricBlowdownLoadsonPWRPrimarySystems,andGDC4,Environmentaland DynamicEffectsDesignBases.5TheLBBNRCreviewcriterionspecifiesthatlicenseesarerequiredtomaintainRCSleakage detectionsystemsequivalenttoRegulatoryGuide1.45tousetheLBBtechnology.6TheLBBsafetyanalysisrequires licenseestomaintainatleastoneRCSleakdetectionsystemwiththecapabilityofdetectingaonegpmleakinfourhours availableatalltimes.7TheintegrityofthiskeysafetyrequirementhasbeentypicallypreservedbyTechnicalSpecification 3.4.15,RCSLeakageDetectionInstrumentation.8TechnicalSpecification3.4.15currentlyprohibitscontinuedreactor operationwithoutatleastoneoperableRCSleakagedetectionsystem.

Michael Peck May 17, 2010

PastContainmentGaseousRadiationMonitorOperabilityIssues In2003,theNRCidentifiedthatgaseousradiationmonitorsusedforRCSleakagedetectionattheByronandBraidwood plantswerenotcapableofperformingthespecifiedsafetyfunction.9TheAgencyconcludedthatbetween223and839 hourswouldbeneededbeforethesegasmonitorscoulddetectaonegpmRCSleakusingarealisticprimarycoolant radioactivitysourceterm.In2003,theNRCalsoconcludedthattheCallawaygaseousmonitorwasinoperablebecause greaterthan500hourswereneededbeforethedetectorcoulddetectaonegpmleakatcurrentRCSactivitylevels.10The NRCsubsequentlyidentifiedthatthegaseousmonitorsatWolfCreek,11DiabloCanyon,12andMcguire13werealso inoperable.Ineachofthesecases,theNRCconcludedthatthegaseousmonitorswereinoperableforTechnical Specification3.4.15compliancebecausetheleakdetectorswerenotcapableofdetectingaRCSleakinareasonableperiod oftime,consistentwitheithertheplantlicensingbasisorsafetyanalysis.Theinspectorsfoundthegaseousmonitor designresponseandsensitivitywasbasedonanassumedRCSsourcetermequivalenttoabout0.1percentfailednuclear fuel.ThisassumedRCSsourcetermwasseveralordersofmagnitudegreaterthanrealisticcoolantradioactivityspecified byRegulatoryGuide1.45.TheNRCinspectorsconcludedthatnoneofthesereactorshadeveroperatedwiththeRCS sourcetermassumedinthemonitordesignandthatcurrentperformancestandardswouldlikelyresultinareactor shutdownlongbefore0.1percentfuelfailurewouldoccur.ApplyingNRCoperabilityguidance,14agencyinspectors concludedthatmonitorswereinoperablybecausetheywerenotabletofunctionasacreditableleakdetectorsatcurrent RCSconditions.InspectorsalsoconcludedthatthehighRCSsourcetermsspecifiedinthedesignandFSARswerea conditionrequiredforoperabilitybecausetheseconditionswereexplicitlyrelieduponbylicenseestodemonstrateRCS leakdetectionfunction.

In2005,theNRCissuedInformationNotice20052415toalertlicenseesthattheRCSactivityassumedinthecontainment radiationatmosphericmonitordesigncalculationsmaybenonconservative.Theagencyconcludedthatindividualgaseous monitorresponseandsensitivityweredependantonplantspecificfactors,includingplacementofdetectorinletinrelation toRCSpiping,RCSsourceterm,ifargoninjectionwasused,containmentsize,containmentventilationflowand distribution(mixing).InformationNotice200524alsoreinforcedthefactthatatmosphericmonitoroperabilitywas dependantonthecapabilityofthemonitortoperformthespecifiedsafetyfunctiontodetectaRCSleak.

ChangesProvidedbyTSTF513 TSTF513providestwochangesthatwouldresultinasignificantreductioninthemarginofsafetyforsomereactor facilities.First,TSTF513includesaclarificationtotheBasisofTechnicalSpecification3.4.15 However,thegaseousorparticulatecontainmentatmosphereradioactivitymonitorisOPERABLEwhenitiscapableofdetectinga 1gpmincreaseinunidentifiedLEAKAGEwithin1hourgivenanRCSactivityequivalentofthatassumedinthedesigncalculations forthemonitors.

ThisstatementwouldallowlicenseestocreditatmosphericradiationmonitorsasoperableRCSleakdetectorsindependent ofthecapabilityofthesecomponentstodetectanactualRCSleak.TSTF513wouldallowsomePWRs(includingByron, Braidwood,Callaway,WolfCreek,DiabloCanyon,&McGuire)tooperatewithaTechnicalSpecificationoperableleak detectorthatwouldlikelyneverhavethenecessaryRCSsourcetermtobefunctional.

ProposedTSTF513wouldresultinasignificantreductioninthemarginofsafetyatsomereactorfacilitiesbecausethe changewouldreducetheminimumrequiredfunctionalRCSleakdetectioncapabilityfromonetonone.TSTF513provides anewlimitingconditionforoperation,ConditionD.Thisconditionallowsreactoroperationforuptosevendayswith onlythegaseousmonitor.GiventhattheBasisclarificationwouldnolongerrequirethegaseousmonitortobecapable ofdetectingaRCSleaktobeoperable,thisConditionwouldeffectivelypermitcontinuedreactoroperationforseven days(atsomefacilities)withoutanyRCSleakdetectioncapability.ReactoroperationwithoutatleastoneRCSleak detectionsystem(withaonegpmwithinfourhourcapability)wouldplacetheplantoutsidetheboundsoftheNRCLBB safetyanalysisassumstions.16 ApprovalofTSTF513wouldalsoestablishanewagencyprecedentbypermittinglicenseestocreditnonfunctional equipmentasoperable.Thispositioniscontrarytocurrentagencyoperabilityguidance.17Thisguidancespecifiesthat:

Asystem,subsystem,train,component,ordeviceshallbeOPERABLEorhaveOPERABILITYwhenitiscapableofperformingits specifiedsafetyfunction(s)andwhenallnecessaryattendantinstrumentation,controls,normaloremergencyelectricalpower, coolingandsealwater,lubrication,andotherauxiliaryequipmentthatarerequiredforthesystem,subsystem,train,component,or devicetoperformitsspecifiedsafetyfunction(s)arealsocapableofperformingtheirrelatedsupportfunction(s).

TSTF513FailedtoProvideAdequateTechnicalJustificationfortheUseofContainmentAtmosphereGrabSamplesfor RCSLeakDetection TSTF513justifiedthesevendayLimitingConditionforOperationD,inpart,byrequiringlicenseestoanalyzecontainment atmospheregrabsamplesonceevery12hours.UseofatmospheregrabsamplesisnotanNRCapprovedmethodforRCS leakdetection18andtheTSTFdidnotprovideanadequatetechnicaljustificationthatgrabsampleswereeffectiveforRCS leakagedetection.

Containmentgrabsamplesaretypicallytakenfromtheuppercontainmentdeck.ThecriticalpipingaffectedbytheLBB analysisisremotelylocatedinthelowercontainment,withintheconfinesofthebiologicalshieldandcranewalls.ForRCS grabsamplestobeeffectivetoidentifyRCSleakage,thecoolantsourcetermandleakratemustbesufficienttoraise gaseousorparticulateradiationlevelsaboveminimumdetectionlimitsatthelocationthegrabsampleistaken.

Forgaseousgrabsamples,licenseestypicallyfillafourlitersamplebottlebyamechanicalairpump.Xe133isatypical dominantRCSgaseousnuclide.RCSXe133concentrationsareoftenlessthan7x104µCi/ml.A60gallonleak(onegpmover anhour)wouldreleaseabout2.2x105ml(or160µCi)intocontainmentfromtheRCS.Givenalarge,dryPWRcontainment hasabout2.5x106Ft3(7.1x1010ml)freespace,theresultingincreaseinXe133inthecontainmentatmospherewouldbe about2.21x109µCi/ml,assuminginstantaneouscontainmentairmixing.ThisXe133valueislowerthanthe1x108µCi/ml levelofdetectionuseforanalyzinggrabsamples.19Actualexpectedradionuclideconcentrationsattheuppercontainment deckcouldbesignificantlylessduetomixingresidenttimeinthecontainment:

[Nsamplepoint]/dt=d[Nleak]/dt/[ContainmentVolume]*d[mixing]/dt WhereNisradionuclideconcentration,dtistimedifferentialandd[mixing]/dtcorrespondstothetimedepend diffusion/forcedconvectionoftheRCSleaklocationtosamplepoint.

Giventhatcontainmentcoolerscirculateabout110,000scfm,aboutathirdradionuclideconcentrationwouldbeseenat theuppercontainmentdeckafteronehourwhencomparedtotheinstantaneousmixingcase(dependingonplantspecific parameters).

Forparticulategrabsamples,licenseestypicallycountafilterafterpassingabout30ft3ofthecontainmentatmosphere.A majorcontributortoRCSparticulateconcentrationisCo58orCs138.AtypicalRCSconcentrationforCo58orCs138isabout 2x103µCi/ml.Applyingthesameapproachusedforthegaseousgrabsample,60gallonsofRCSwouldresultinabout 6.3x109µCi/mlincontainmentassuminginstantaneousmixing.ThisCo58valueisalsolowerthanthe1x108µCi/mllevelof detectionusedforgrabsamples.20Actualradionuclideparticulateconcentrationsattheuppercontainmentdeckwould alsobelessduetomixingresidenttimeinthecontainment:

d[Nsamplepoint]/dt=d[Nleak]/dt/[ContainmentVolume]*d[mixing]/dt-d[Nplateout]/dt Inadditiontothetransportterms,additionalcontainmentatmosphericparticulateswouldbelostduetoplateoutonthe coolersurfacesinthelowercontainmentsurfacesandinthecontainmentcoolingcoolercoils.

ProposedAlternative

1. RecommendthattheAgencynotapproveTSTF513,Revision2.

2. Recommendadditionalrenegotiationwithindustryto:

RemovetheclarificationtoTechnicalSpecification3.4.15Basiswhichprovidesforcreditingnonfunctional equipmentasoperable.RemovalofthischangewouldstillpermittheuseofradiationmonitorsforRCSleak detectionatthoseplantswherethisequipmentremainsfunctionalgivenplantspecificdesignfeaturesandRCS sourceterms.

Specifythatatmosphericgrabsampleanalysisresultsarerequiredtobecompletedeveryfourhourswhile operatinginConditionD.ThischangewouldprovideconsistencywiththeLBBsafetyanalysis.

IncludedprovisionsintheTechnicalSpecificationBasistoensurelicenseescompleteaplantspecificanalysis, includingtheapplicablerangesofRCSsourcetermsandcontainmentdesignandequipmentalignmentsand transporttimes,demonstratingcontainmentatmosphericgrabsampleshavethecapabilitytodetectaonegpm RCSleakwithinfourhours.

EnsuretherevisedbasisforTechnicalSpecification3.4.15includesallapplicablesafetyanalysis(LBB).

3. CorrecterroronAttachment1,page1.Attachment1states:

Newcondition[D]RequiredActionrequireanalyzinggrabsamplesofthecontainmentatmosphereorperformingan RCSwaterinventorybalanceevery12hoursandrestoringanothermonitorwithin7days.

NewCondition[D]doesnotrequirewaterinventorybalanceevery12hours.

References

1.

Revised Models for Adoption of TSTF-513, Revision 2, Revise PWR Operability Requirements and Actions For RCS Leakage Instrumentation For Publication In The Federal Register (TAC Nos. ME0988)

2.

Regulatory Guide 1.45, Guidance on Monitoring and Responding to Reactor Coolant System Leakage, Revision 0

3.

NUREG-0800, U.S. Nuclear Regulatory Commission Standard Review Plan, Section 5.2.5, Reactor Coolant Pressure Boundary Leakage Detection, Revision 2

4.

IAEA-TECDOC-710, Applicability of the leak before break concept Report of the IAEA Extrabudgetary Programme on the Safety of WWER-440 Model 230 Nuclear Power Plants, Status report on a generic safety issue (www-pub.iaea.org/MTCD/publications/PDF/te_710_web.pdf)

5.

NUREG-1061, Volume 3, Report of the U.S. Nuclear Regulatory Commission Piping Review Committed, Evaluation of Potential for Pipe Breaks, November, 1984

6.

NUREG-0800, U.S. Nuclear Regulatory Commission Standard Review Plan, 3.6.3, Leak-Before Break Evaluation Procedures, Revision, 1

7.

Generic Letter 84-04, Safety Evaluation of Westinghouse Topical Reports Dealing with Elimination of Postulated Pipe Breaks In PWR Primary Main Loops

8.

NUREG 1430

9.

Letter to J.L. Skolds, Exelon Nuclear, February 20, 2003, from L. Raghavan, NRR, Resolution of Allegation NRR-2002-A0022

10. Callaway Plant - NRC Integrated Inspection Report 05000483/2003005,October 16, 2003 (ADAEMS ML032890770)

11. Wolf Creek Generating Station - NRC Integrated Inspection Report 05000482/2004004 November 9, 2004 (ADAMS ML0431402790)

12. Diablo Canyon Power Plant - NRC Integrated Inspection Report 05000275/2008004 AND 05000323/2008004 November 3, 2008, (ADAMS ML0830801130)

13. Mcguire Nuclear Station - NRC Integrated Inspection Report 05000369/2005002 And 05000370/2005002 And Independent Spent Fuel Storage Installation Inspection Report 0720038/20050001 (ADAMS ML051190140)

14. RIS 2005-20, Revision to NRC Inspection Manual Part 9900 Technical Guidance, Operability Determinations & Functionality Assessments for Resolution of Degraded or Nonconforming Conditions Adverse to Quality or Safety. Revision 1

15. NRC INFORMATION NOTICE 2005-24, Nonconservatism in Leakage Detection Sensitivity, August 3, 2005

16. Generic Letter 84-04, Safety Evaluation of Westinghouse Topical Reports Dealing with Elimination of Postulated Pipe Breaks In PWR Primary Main Loops

17. Ibid 13

18. Ibid 2, 3, & 5

19. Discussion with Diablo Canyon Chemistry Supervisor on May 13, 2010

20. Ibid 15

10 CFR 50.36 states that when a Limiting Condition for Operation of a nuclear reactor is not met, the licensee shall shut down to reactor or follow any remedial action permitted by the technical specifications until the condition can be met. In the case of TSTF-513, the agency is changing which remedial actions licensees are permitted to perform until the LCO can be met. This allows licensees time to repair equipment while preventing a thermal transient to the plant due to a required shut down. The TS revised by TSTF-513 do not change the requirement for all safety systems to be operable. Therefore, any licensee adopting TSTF-513 should still be able to mitigate any design basis accidents or transients even if the leakage detection equipment were to fail to detect a leak..

The staff believes that the TS should be revised because RG 1.45,,provides conflicting guidance on the operability requirements for the leak detection systems using airborne particulate or gaseous radiation. In addition to the requirement to be able to detect a one gpm within one hour, RG 1.45 also endorses the use of fuel failure estimates that are much higher than operating plants are experiencing today (i.e.,for use in determining the required instrument sensitivity). Specifically, the RG states that The expected values used in the plant environmental report would be acceptable. This forms part of the licensing basis for plants committed to RG 1.45. The RG recommended capability to detect a one gpm leak is contingent on this assumption, which is specifically endorsed by the staff.

The staff recognizes that LBB analyses assume at least one method of leakage detection can detect a RCS leakage rate of 1 GPM in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. TS, on the other hand, are structured to allow plants time to restore inoperable equipment when a licensing basis assumption is not met, provided that the level of risk associated with the inoperabilty is low. TSTF-513 provides time for the restoration of the inoperable instrumentation because the risk is low, and the licensee will be required to take additional actions to minimize the impact on the margin of safety while the instruments are restored.

The staff notes that the TS bases restate the licensing basis. The licensing basis only required using the RCS radioactivity concentration assumed in the design calculations. We understand that the actual RCS radioactivity concentration is now much lower than originally assumed and this adversely affects how quickly the containment gaseous activity monitor would detect small RCS leaks. This is why TSTF-513 would require operators to take extra actions to monitor for RCS leaks when only the containment gaseous activity monitor is operable. While the gaseous monitors may have difficulty detecting small leaks, they are capable of detecting larger leaks (e.g., on the order of 5 gpm). As a result, we consider that they are still appropriate instruments to be retained in TS since they may detect a larger leak that goes undetected by the other leakage detection instruments.

Please see the responses to the Proposed Alternatives in the following pages.

Response to Proposed Alternative #1:

Since receipt of Section A, a revised TSTF-513 has been proposed. TSTF-513, Revision 3 contains the main elements of Revision 2 and the staff believes that Revision 3 is acceptable. The ADAMS accession number for the Revised Models for Adoption of TSTF-513, Revision 3 is ML101870545.

The staff believes that it is the combination of all three diverse leakage detection sensors that provides the maximum potential for early detection of a leak. Some licensees in response to the gaseous radiation monitor concerns have obtained license amendments to remove the gaseous radiation monitors from their TS, reducing their leakage detection systems to two instruments. The staff does not believe this is the best way to address this problem as it reduces the licensee's capability to detect leaks. In addition, as previously stated, the changes require more frequent monitoring of other leakage detection methods when the containment atmosphere gaseous radioactivity monitor is the only operable RCS leakage detection instrument. The staff feels that the appropriate approach to address the issue is requiring operators to monitor other leakage detection methods more frequently to maximize the potential for early identification and detection of an RCS leak such that leak before break assumptions are maintained.

Furthermore, the staff believes that the safety function of this instrument is clarified by this TSTF. Specifically, the safety function of leakage detection is to provide operators with an early warning of potential degradation of the Reactor Coolant Pressure Boundary with sufficient time for the operators to take action and place the plant in a safe condition before a catastrophic failure occurs. The function of leakage detection is to provide defense in depth by allowing to operators to take action before an accident occurs, not to mitigate the accident. The TSTF clarifies the level of sensitivity required for the gaseous monitor. This approach is consistent with the way operability is currently evaluated.

Because many factors can affect leakage detection capabilities, the TS are configured to require multiple diverse means of leakage detection. This allows the capabilities of the sensors to be combined to provide the best detection capability and the greatest defense in depth. The staff notes that the specified safety function of these monitors is not based on the detection of a specific leak size. Rather it is to warn the operators of RCPB degradation. The specific requirement to detect a one gpm leak within one or four hours has no mechanistic tie to safety. There is no accident or transient scenario that requires a one gpm leak be detected within four hours in order to achieve successful mitigation of the accident. The situation in which the gas monitor is the only operable monitor is a very rare occurrence. And, leakage detection is a defense in depth capability which does not mitigate any accident or transient. All safety systems will still be required to be operable, and will still be able to mitigate any design basis accidents or transients. In addition, heightened awareness and additional Required Actions in the TS combined with the reduced CT minimize any reduction in the margin of safety while operating with only the gaseous monitor operable.

The staff notes that the current STS would allow 30 days of operation with only the gaseous monitor operable.

TSTF-513 revises the CT to 7 days, and requires additional actions. Essentially, this change recognizes the reduction in detection capability when the other two instruments used for RCS leakage detection are inoperable, and would account for this by modifying the Required Actions to provide additional actions and a reduced CT when the Gas Monitor is the only Required instrument operable. The gas monitor is not being credited towards any relaxation of requirements.

Response to Proposed Alternative #2:

The staff believes that the proposed changes to the TS Bases should be retained because they are necessary to prevent continued confusion. The changes revise the language regarding equipment operability. These revisions clarify when the equipment can be considered operable and are acceptable because they define, consistent with the design basis of the facility, the minimum set of diverse instruments that must be operable, the plant parameters monitored by the instrumentation, the design sensitivity of the leakage detection instruments, and factors that affect the operational sensitivity of the instrument. In addition, the TS are modified to provide Required Actions and a reduced CT which the staff believes are acceptable when the gaseous monitor is the only operable leakage detection instrument.

Increasing grab sample frequency would add no value to the Required Actions and may distract operators.

Requiring the grab samples is done specifically because it is recognized that a 1 GPM leak may not be recognized in 1hour.

Containment grab samples have long been identified as an acceptable measure to compensate for inoperable containment atmosphere radioactivity monitors. The measure has been identified in the associated improved standard technical specification since its inception in 1993. As noted above, 10 CFR 50.36 states that when an LCO is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met. Revision 3 to Section 16.0, Technical Specifications, of the Standard Review Plan (NUREG-0800), states that plant specific Technical Specifications satisfy 10 CFR 50.36 and are acceptable if the specifications are consistent with the regulatory guidance of the improved standard technical specifications and present plant -specific values for parameters at the indicated level of detail.

Therefore, the periodic monitoring of containment grab samples is an NRC approved remedial action to compensate for short-term inoperability of a permanent containment atmosphere radioactivity monitor.

From a technical perspective, both the permanent containment atmosphere radioactivity monitors and the periodic monitoring of containment atmosphere grab samples are subject to factors that degrade their sensitivity to reactor coolant system leakage. As discussed in RG 1.45, reactor coolant system activity, detector sensitivity, detector response time, transport time, and other factors (e.g., containment atmospheric dilution, holdup, and decay) affect the overall sensitivity to leakage. The physical processes used to measure containment atmosphere radioactivity are similar for both the permanent detectors and the grab samples. The particulate monitors draw a sample volume of the containment atmosphere through a filter medium and measure the collected particulate radioactivity. The gaseous monitors measure radioactivity in a defined volume of the containment atmosphere. The principal difference between detectors is the continuous monitoring capability of the permanently installed monitors as opposed to the periodic nature of the grab sample monitoring. Therefore, with appropriate controls, the grab samples constitute an effective remedial measure to detect reactor coolant leakage.

Response to Proposed Alternative #3:

The editorial error has been corrected.