ML15274A599

10-01-15 Public Phone Call

ML15274A599
Person / Time
Site:	South Texas
Issue date:	10/01/2015
From:	Lisa Regner Plant Licensing Branch IV
To:
Regner L
References
GL-04-002, GSI-191
Download: ML15274A599 (12)

Text

Description of Supplement 2 to STPNOC Risk-Informed Licensing Application to Address GSI-191 and Respond to GL-2004-02Public Phone Call Meeting with NRCOctober 1, 2015 Introduction and AgendaIntroduction of STP participantsDesired Outcomes:NRC staff understand the STPNOC licensing application and the changes from the previous supplement Resolve NRC questions and establish follow-up to resolve questions that remain openIdentify steps remaining for going forward with the application2 Introduction and AgendaAgendaOverview of changes from November 13, 2013 letter (ML13323A183)Effect on reported resultsConservatism and acceptability of revised approachRoverD In-Vessel Cooling AnalysisSpecific Focus AreasDebris Test MarginFollow-up and Going Forward Actions3 Overview of Changes from November 13, 2013 LetterChanged methodology to explicitly incorporate certain deterministically-RoverD) that was described in March 25, 2015 letter (ML15091A440)Added the plant-specific testing deterministic basis (Letter Attachment 1-2)Addressed all the NRC content guide questions and responded to earlier RAIs (Letter Attachment 1-5)Added the RoverDrisk-informed description (Letter Attachment 1-3)Expanded Defense-in-Depth and Safety Margin discussion (Letter Attachment 1-4)Clarification on exemptions))Clarified that a specific exemption to single failure is not being requestedAdded proposed Technical Specification change for debris-specific effects (Letter Attachment 3)4 Overview of Changes from November 13, 2013 LetterWhat is no longer in the scope of the application and should not be part of the review, including RAI responses:CASA Grande calculation of conditional failure probabilitiesUse of correlations for head -Uncertainty quantification of pipe break probability distributions; replaced with conservative estimatesTime dependent debris transportUse of STP PRA for calculation of delta CDF; used only for delta LERFApplications of CASA Grande that are still usedDebris generationDebris arrival to the containment pool (non-time dependent)5 Results with Revised Methodology Remain in RG 1.174 Region IIIConclusions are unchanged with revised methodology2015 RoverD: -07/yr, -10/yr2013 CASA Grande/PRA: -08/yr, -11/yr6 Conservatism and Acceptability of Revised Approach7 Conservatism and Acceptability of Revised ApproachDeterministically tested debrisQualitative margin evaluation of July 2008 test determined that low density fiberglass is the only debris source term not bounded by the testUsed weld/break characteristics from NUREG 1829Considers various break types and locationsConservatisms used in transport calculation8 RoverD In-Vessel Cooling Analysis T-H and Debris Analyses Show Adequate Long-Term CoolingAnalysis assuming total blockage of core and core bypass shows that there is sufficient cooling for all HLB and all SLOCA (CLB and HLB)FA tests show that there is insignificant pressure drop for bounding HLB conditions (DEGB, no credit for decay heat at time of recirculation) with 15 gm/FA including chemical effectsSTP strainer penetration testing shows that for all CLB, << 15gm/FA accumulates on the coreShows there is no CLB with potential for in-core debris effects, independent of T-H analysisConfirms that all risk-informed debris effects scope is due to blockage at the strainer9 Specific Focus ItemsBreaks that have bounding debris transport fractions do not have direct spill paths to the containment floorTransport evaluation included 1, 2, and 3 trains operatingTransport metrics from NUREG/CR 6772, NUREG/CR 6808, and Law were applied.Evaluation of transport of unqualified epoxy, particulate, and chips shows sufficient marginErosion MethodologySTP conditions are bounded by 30-day erosion testing showing factors below 10%Methodology shown in Table 10 of Att. 1-2 of 8/20/15 letterEarly or late arrival is based on initial blow-down to pool or wash down by spraySmall and large percentage are the eroded fractions from small and large debrisEarly and late arrival of fines based on initial blow-down to pool or wash down by sprayMargin evaluation of July 2008 test shows that low density fiberglass is the only debris source term not bounded by the test10 Debris Test Margin11LDFG fines accounted for in the risk-informed portionMicrothermand Epoxy offset by:MariniteZinc Follow-up and Going Forward ActionsNovember public meeting to resolve outstanding questions12