ML17003A033

Palo Verde, Enclosure 2 - APS Meeting Slides

ML17003A033
Person / Time
Site:	Palo Verde
Issue date:	12/29/2016
From:	Arizona Public Service Co
To:	Office of Nuclear Reactor Regulation
Watford M
References
CAC MF9019
Download: ML17003A033 (23)

Text

Second License Amendment Request for the Unit 3 Train B Diesel GeneratorPalo Verde Nuclear Generating StationDecember 29, 2016 Agenda*Background*Regulatory Commitments*Event Investigation*Risk Assessment*Second License Amendment Request*Conclusions2 First License Amendment Request (LAR)*One-time Technical Specification (TS) Change to Allow a 21 day Completion Time In Response to Failure of Unit 3 B Train DG on December 15, 2016-Extension of 11 days needed to collect/analyze data and continue repair -Deterministic justification based upon BTP 8 Risk insights provided to support change -NRC commitments made in LAR-NRC Amendment 199 issued on December 23, 20163 Regulatory Commitments*Commitments documented in NRC Amendment #199 include but are not limited to:-Three, 2 MW portable DGs staged, tested and hooked-up to Unit 3 FLEX 4.16KV connections-Diesel driven FLEX Steam Generator make-up pump staged in Unit 3-Suspension of discretionary maintenance on SBOGs, Switchyard, Safety Systems-Establish protected equipment controls for Train A equipment, SBOGs, portable equipment-Commitments monitored and tracked by OPS-Dedicated personnel4 Palo Verde AC Power System5 Palo Verde AC Power System6 Event Investigation*Partnerships established with MPR, Goltens, Structural Integrity, EPRI, and the Cooper-Bessemer Owners Group*Evidence of high cycle fatigue on master connecting rod*Second major failure of 3B DG (9R)*1986 event created localized misalignment7 Operating Experience (OE)*Cooper-Bessemer KSV-20 OE -1986 -Palo Verde 3B DG connecting rod (9R) failure during unit startup testing program-1989 -South Texas Project DG 22 connecting rod failure during a surveillance test -2003 -South Texas Project DG 22 connecting rod failure during a surveillance test (one-time LAR using a two-phased approach to extend allowable outage time to 113 days)-2016 -Palo Verde 3B DG connecting rod (9R) failure during a surveillance test8 DIRECT CAUSE OF FAILURE*High cycle fatigue failure of the master connecting rod ligament which surrounds the lower part of the articulating rod pin. 9 Event Investigation10Master Rod Fracture Surface ROOT CAUSE OF FAILUREFLAW + STRESS = FATIGUE POTENTIAL FLAWSSTRESS1. Residualtensile within master connecting rod bore due to machining process changeMis-Alignment2. Fretting 3. "Undersized" OversizedBearing following 1987 repair. 11 12 3A/3B COMPARITIVE EVALUATION*Evaluating Wide Array of Data*Relevant Data-Vibration -Engine Analysis-Line Bore Data-Work History-Event History13 3A/3B COMPARITIVE EVALUATION*Unit 3 "B" Emergency Diesel Generator experienced a catastrophic failure that induced crankshaft mis-alignment which increased the stress profile within the engine*Unit 3 "A" engine has not had a catastrophic failure*Unit 3 "A" engine vibration displacement data is consistently less and has significantly less variability*Unit 3 "A" Master connecting rods are original equipment (i.e. Pre machining change)14 Engineering ConclusionThere is no common cause mode of failure to Unit 3 "A" Emergency Diesel Generator due to the unique aspects of the Unit 3 "B" Diesel Generator root cause.15 Risk Assessment*PRA models for-Internal Events-Internal Flood-Internal Fire-Seismic*Other hazards screened out16 PRA Model and Risk-Informed Application Model History Pre-2010201020112012201320142015201617Internal Events CEOG peer review & numerous risk-informed TS changesTSTF-425 Surveillance Frequency Control Program approved2ndfire PRA peer reviewTSTF-505 submittedInternal Flood peer reviewRisk-informed 7-day inverter TS approvedSeismic PRA peer review1stfire PRA peer reviewInternal Events self-assessment per RG 1.200 App BAll Unit 3Mods Comp

& all ASME PRA Std SRs Met to CC IIExternal Hazards Screening peer review Risk Assessment*Palo Verde PRA Aspects-Six 100% capacity SG makeup pumps all supplied by onsite power sources-Only one of these powered by B DG if loss of offsite power-RCP seal LOCAs negligible -ECCS significance minimal in loss of offsite power events-No Pressurizer power-operated relief valves-Very low internal events CDF and LERF -consistent with STP and Millstone 3-Only shared systems in PRA are SBOGs and firewater-Dedicated fire department staff and equipment-Risk significant FLEX connections outside of unit-Did not need to implement NFPA-805 to address multiple spurious operations18 PRA Model Credited Changes *Revised emergency operating procedures and night order to direct timely use of firewater to auxiliary feedwatercross-tie in total loss of feedwaterevent -validated in simulator-Additional dedicated auxiliary operator added to each shift to implement cross-tie*Post continuous fire watch in fire zone FCCOR2 (120' Corridor Building)*Establish new transient combustible and hot work exclusion zones and conduct shiftlyinspections-Fire zones FCCOR2 (120' Corridor Building) and FCCOR2A (120' Corridor Riser Shaft)-Fire zones FCTB04 (upper level only, non-class DC Equipment, [FCTB04-TRAN1])-Fire zone FC86A (train A Seismic Gap, make part of train A Electrical Protected Equipment)-Fire zone FCTB100 zone ZT1G (SW corner, south half of 100' Turbine between columns TA and TC)19 Risk Assessment*Defense-in-Depth Evaluation-Unavailability does not reduce the amount of available equipment to a level below that necessary to mitigate a design basis accident*Safety Margin Evaluation-No significant reduction in margin of safety*Regulatory Guide 1.200, Revision 2 compliant*Regulatory Guide 1.177, Revision 1 compliant*Regulatory Guide 1.174, Revision 2 compliant20 Second License Amendment Request*Requesting a extension of TS 3.8.1 Condition B.4 Completion Time to complete the DG Repairs*Request on Emergency Basis*Risk-informed LAR*Carrying forward the Commitments made in Deterministic LAR*To be submitted Friday, December 30*Request approval by early Thursday morning 21 Conclusions*Direct cause of the 3B DG failure has been determined*No common mode failure applicability to 3A DG*Continue to have diverse and redundant sources of AC power and steam generator makeup*PRA risk acceptable in accordance with Regulatory Guides 1.174 and 1.177*No significant hazards consideration criteria satisfied22 Questions?