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 Station December 29, 2016 Agenda*Background

• Regulatory Commitments

• Event Investigation

• Risk Assessment

• Second License Amendment Request

• Conclusions 2

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 8-8

-Risk insights provided to support change

-NRC commitments made in LAR

-NRC Amendment 199 issued on December 23, 2016 3

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 personnel 4

Palo Verde AC Power System 5

Palo Verde AC Power System 6

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 misalignment 7

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 test 8

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 Investigation 10 Master 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 History 13 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 Conclusion There 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 out 16 PRA Model and Risk-Informed Application Model History Pre-2010 2010 2011 2012 2013 2014 2015 2016 17Internal Events CEOG peer review & numerous risk-informed TS changesTSTF-425 Surveillance Frequency Control Program approved 2 ndfire PRA peer reviewTSTF-505 submittedInternal Flood peer reviewRisk-informed 7-day inverter TS approvedSeismic PRA peer review 1 stfire PRA peer reviewInternal Events self-assessment per RG 1.200 App B All Unit 3 Mods 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 operations 18 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 compliant 20 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 satisfied 22 Questions?