ML16103A573

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Final ASP Analysis (LER 364-14-002)
ML16103A573
Person / Time
Site: Farley Southern Nuclear icon.png
Issue date: 04/21/2016
From: Dejesus J
NRC/RES/DRA/HFRB
To:
Aird D
Shared Package
ML16103A566 List:
References
LER 364-14-002 IR 2014005
Download: ML16103A573 (9)
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Text

Final Precursor Analysis Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Joseph M. Farley Nuclear Manual Reactor Trip due to Loss of 2B Startup Plant, Unit 2 Auxiliary Transformer LER: 364-2014-002 Event Date: 10/14/2014 CCDP = 6x10-6 IR: 50-364/14-005 Plant Type: Pressurized-Water Reactor (PWR)

Westinghouse 3-Loop with Dry, Ambient Pressure Containment Plant Operating Mode (Reactor Power Level): Mode 1 (82% Reactor Power)

Analyst: Reviewer: Contributors: BC Review Date:

Jonathan DeJesus David Aird N/A 3/31/2016 EXECUTIVE

SUMMARY

On October 14, 2014, while conducting planned maintenance on emergency diesel generator (EDG) 2B, a lighting strike in the Unit 2 switchyard caused the 2B startup auxiliary transformer (SAT) to de-energize. The 2B SAT and 2B EDG provide the normal and backup power, respectively, to the 2G 4160 V bus that supplies power to the B train component cooling water (CCW) pumps and other loads. Since the loss of the 2B SAT and the 2B EDG unavailability affected the on-service train (i.e., the B train) of CCW, operators followed procedures and manually tripped the reactor. The reactor trip resulted in a valid actuation of the auxiliary feedwater system (AFW).

According to the modeling assumptions used in this Accident Sequence Precursor (ASP) analysis, the most likely core damage sequence is a transient initiating event (IE-TRANS) followed by the failure of AFW, failure of main feedwater, and failure of feed and bleed cooling.

This accident sequence accounts for approximately 63% of the conditional core damage probability (CCDP) for the event. This event was determined to be a precursor with a CCDP of 5.5x10-6.

EVENT DETAILS Event Description. On October 14, 2014, a lighting strike in the Unit 2 switchyard caused the 2B startup auxiliary transformer (SAT) to de-energize. The 2B SAT was the normal power supply to the 2G 4160 V bus that supplied power to the B train component cooling water (CCW) pumps and other loads. When the 2B SAT de-energized, power was lost to the B train CCW pumps that were aligned as the on-service train supplying cooling water to the reactor coolant pump (RCP) oil coolers and thermal barrier heat exchangers. Normally, the 2B emergency diesel generator (EDG) would automatically start and provide power to the B train CCW pumps.

However, with the 2B EDG unavailable due to planned maintenance, there was no automatic power supply to the B train CCW pumps. Procedures directed the operators to manually trip the reactor and stop all RCPs if the on-service train of CCW was affected. Accordingly, the licensee manually tripped the reactor and stopped all RCPs. The reactor trip resulted in a valid actuation of the auxiliary feedwater system. All other safety systems responded as designed. Additional information is provided in Reference 1 (licensee event report) and Reference 2 (inspection report).

Enclosure 1

LER 364-2014-002 Causes. The direct cause of this event was a loose termination from a missing nut in the power circuit breaker (PCB) 944 current transformer circuit connection to the instantaneous overcurrent relay, which in addition to the continued fault on the 500 kV bus side of the PCB 112 led to the B train loss of site power. The root cause was inadequate verification practices during wiring installations that led to the nut not being installed on its terminal.

Inspection Report/Significance Determination Process Result. The inspectors reviewed the event and determined that the licensee failed to take actions to mitigate the increased risk of a reactor trip with the B train of CCW as the on-service train while the 2B EDG was unavailable due to planned maintenance. The result was a self-revealing, Green finding. This LER is closed.

MODELING ASSUMPTIONS Analysis Type. The staff used version 8.21 of Farleys Units 1 and 2 Standardized Plant Analysis Risk (SPAR) model, created in September 2013, to perform the analysis (i.e., initiating event assessment). Farleys SPAR model is based on Unit 1, but the event occurred in Unit 2.

Therefore, surrogate components in Unit 1 were adjusted to account for the equivalent equipment affected in Unit 2. This event was modeled as a general transient initiating event.

Analysis Rules. The ASP program uses Significance Determination Process results for degraded conditions when available and appropriate to meet ASP Program needs. In this case, while the inspection program classified this event as a Green finding, an ASP analysis was performed consistent with ASP Program practices and guidance to analyze all initiating events.

Key Modeling Assumptions. The analysis contains the following modeling assumptions and basic event probability changes:

  • The probability of IE-TRANS (General Transient Initiating Event) was set to 1.0; all other initiating event probabilities were set to zero.
  • Basic event ACP-TFM-FC-SUT1B (230 to 4.2 kV Startup Transformer 1B Fails) was set to TRUE.
  • Basic event EPS-DGN-TM-DG1B (Diesel Generator 1B Unavailable due to Test and Maintenance) was set to TRUE.
  • EDG 2C is designated as the station blackout (SBO) diesel and can supply power to Unit 1 or Unit 2 when the 1B or 2B EDG is not available. Basic event EPS-DG2C-UNIT2 (Diesel 2C Required for SBO on Unit 2) was set to FALSE because EDG 2C1 was not required for an SBO event on the other unit (i.e., Unit 1, but modeled as Unit 2 in this analysis).

1 The staff considered setting the test and maintenance basic event for EDG 2C (EPS-DGN-TM-DG2C) to FALSE.

However, Farleys Technical Specifications (Reference 3 - see Condition E of Limiting Condition for Operation 3.8.1) do not preclude the licensee from placing EDG 2C in test and maintenance while another EDG is also undergoing test and maintenance. A sensitivity analysis was performed and it had a minimal reduction in CCDP.

2

LER 364-2014-002 ANALYSIS RESULTS CCDP. The point estimate CCDP for this event is 5.5x10-6. The ASP Program acceptance threshold is a CCDP of 1x10-6 or the CCDP equivalent of an uncomplicated reactor trip with a non-recoverable loss of main feedwater or loss of condenser heat sink, whichever is greater.

This CCDP equivalent is 1.7x10-6 for both cases. Therefore, this event resulted in a precursor for Farley, Unit 2.

Dominant Sequence. The dominant accident sequence is TRANS Sequence 20 (CCDP

= 3.5x10-6) that contributes approximately 63% of the total internal events CCDP. Figure 1 in Appendix B illustrates this sequence. The cut sets and sequences that contribute to the top 95%

and/or at least 1% of the total internal events CCDP are provided in Appendix A.

The events and component failures in TRANS Sequence 20 are:

  • Feed and bleed cooling fails.

REFERENCES

1. Southern Nuclear Operating Company, Inc., "Joseph M. Farley Nuclear Plant - Unit 2, Licensee Event Report 2014-002-00, Manual Reactor Trip due to Loss of 2B Startup Auxiliary Transformer and Loss of Offsite Power, dated December 12, 2014 (ML14346A391).
2. U.S. Nuclear Regulatory Commission, Joseph M. Farley Nuclear Plant - NRC Integrated Inspection Report 05000348/2014005; and 05000364/2014005 and Exercise of Enforcement Discretion, dated February 9, 2015 (ML15040A564).
3. Appendix A, Technical Specifications, to Joseph M. Farley Nuclear Plant, Unit 2 Renewed Facility Operating License No. NPF-8 (ML052780033 2).

2 Farley, Unit 2 uses the same Technical Specifications as Farley, Unit 1.

3

LER 364-2014-002 Appendix A: Analysis Results Summary of Conditional Event Changes Cond. Nominal Event Description Value Value ACP-TFM-FC-SUT1B 230 TO 4.2 KV STARTUP TRANSFORMER 1B FAILS TRUE 2.27E-5 EPS-DG2C-UNIT2 DIESEL 2C REQUIRED FOR SBO ON UNIT 2 FALSE 1.14E-2 DG 1B UNAVAILABLE DUE TO TEST AND EPS-DGN-TM-DG1B TRUE 1.43E-2 MAINTENANCE IE-TRANS TRANSIENT 1.00E+0a 6.90E-1

a. All other initiating event probabilities were set to zero.

Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

Event Tree Sequence CCDP  % Contribution Description TRANS 20 3.49E-6 63.2% /RPS, AFW, MFW, FAB TRANS 21-16 8.78E-7 15.9% RPS, RCSPRESS TRANS 21-15 7.22E-7 13.1% RPS, /RCSPRESS, MFW, AFW-A TRANS 19 2.86E-7 5.2% /RPS, AFW, MFW, /FAB, SSCR, HPR TRANS 21-14 1.15E-7 2.1% RPS, /RCSPRESS, MFW, /AFW-A, BORATION Total 5.52E-6 100.0%

Referenced Fault Trees Fault Tree Description AFW AUXILIARY FEEDWATER AFW-A AUXILIARY FEEDWATER SYSTEM BORATION EMERGENCY BORATION FAB FEED AND BLEED HPR HPR PRESSURE RECIRCULATION MFW MAIN FEEDWATER RCSPRESS RCS PRESSURE LIMITED RPS REACTOR TRIP SSCR SECONDARY SIDE COOLING RECOVERED Cut Set Report - TRANS 20 Only items contributing at least 1% to the total are displayed.

  1. CCDP TOTAL% CUT SET 3.49E-6 100 1 1.00E-6 28.71 IE-TRANS,ACP-BAC-LP-1F,EPS-DGN-FR-DG2C 2 6.66E-7 19.09 IE-TRANS,ACP-BAC-LP-1F,EPS-XHE-XM-STRT2C 3 4.78E-7 13.70 IE-TRANS,ACP-BAC-LP-1F,EPS-DGN-TM-DG2C 4 9.63E-8 2.76 IE-TRANS,ACP-BAC-LP-1F,EPS-DGN-FS-DG2C 5 9.45E-8 2.71 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-FB 6 7.51E-8 2.15 IE-TRANS,AFW-ACX-CF-MDPABR,AFW-TDP-FR-P02,HPI-XHE-XM-FB 7 6.28E-8 1.80 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-FB A-1

LER 364-2014-002

  1. CCDP TOTAL% CUT SET 8 6.15E-8 1.76 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-FB 9 4.51E-8 1.29 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-TM-DG2C,HPI-XHE-XM-FB 10 4.09E-8 1.17 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-FB 11 3.96E-8 1.13 IE-TRANS,ACP-BAC-LP-1K,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C 12 3.76E-8 1.08 IE-TRANS,AFW-MDP-CF-START,AFW-TDP-FR-P02,HPI-XHE-XM-FB Cut Set Report - TRANS 21-16 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 8.79E-7 100 1 1.18E-7 13.42 IE-TRANS,PPR-MOV-FC-8000A,RPS-BME-CF-RTBAB 2 1.18E-7 13.42 IE-TRANS,PPR-MOV-FC-8000B,RPS-BME-CF-RTBAB 3 9.83E-8 11.19 IE-TRANS,PPR-MOV-FC-8000B,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 4 9.83E-8 11.19 IE-TRANS,PPR-MOV-FC-8000A,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 5 8.86E-8 10.08 IE-TRANS,PPR-MOV-FC-8000A,RPS-ROD-CF-RCCAS 6 8.86E-8 10.08 IE-TRANS,PPR-MOV-FC-8000B,RPS-ROD-CF-RCCAS 7 6.66E-8 7.59 IE-TRANS,PPR-MOV-FC-8000B,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 8 6.66E-8 7.59 IE-TRANS,PPR-MOV-FC-8000A,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 9 2.03E-8 2.31 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,RPS-BME-CF-RTBAB 10 1.69E-8 1.93 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 11 1.52E-8 1.74 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,RPS-ROD-CF-RCCAS 12 1.15E-8 1.31 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL Cut Set Report - TRANS 21-15 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 7.22E-7 100 1 6.36E-8 8.81 IE-TRANS,AFW-TDP-FR-P02,RPS-BME-CF-RTBAB 2 5.31E-8 7.35 IE-TRANS,AFW-TDP-FR-P02,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 3 4.84E-8 6.71 IE-TRANS,EPS-DGN-FR-DG2C,RPS-BME-CF-RTBAB 4 4.78E-8 6.62 IE-TRANS,AFW-TDP-FR-P02,RPS-ROD-CF-RCCAS 5 4.04E-8 5.60 IE-TRANS,EPS-DGN-FR-DG2C,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 6 3.64E-8 5.04 IE-TRANS,EPS-DGN-FR-DG2C,RPS-ROD-CF-RCCAS 7 3.60E-8 4.98 IE-TRANS,AFW-TDP-FR-P02,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 8 3.22E-8 4.46 IE-TRANS,EPS-XHE-XM-STRT2C,RPS-BME-CF-RTBAB 9 2.74E-8 3.79 IE-TRANS,EPS-DGN-FR-DG2C,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL A-2

LER 364-2014-002

  1. CCDP TOTAL% CUT SET 10 2.69E-8 3.72 IE-TRANS,EPS-XHE-XM-STRT2C,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 11 2.42E-8 3.35 IE-TRANS,EPS-XHE-XM-STRT2C,RPS-ROD-CF-RCCAS 12 2.31E-8 3.20 IE-TRANS,EPS-DGN-TM-DG2C,RPS-BME-CF-RTBAB 13 1.93E-8 2.67 IE-TRANS,EPS-DGN-TM-DG2C,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 14 1.82E-8 2.52 IE-TRANS,EPS-XHE-XM-STRT2C,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 15 1.74E-8 2.40 IE-TRANS,EPS-DGN-TM-DG2C,RPS-ROD-CF-RCCAS 16 1.31E-8 1.81 IE-TRANS,EPS-DGN-TM-DG2C,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 17 1.05E-8 1.45 IE-TRANS,AFW-TDP-FS-P02,RPS-BME-CF-RTBAB 18 8.72E-9 1.21 IE-TRANS,AFW-TDP-FS-P02,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 19 8.68E-9 1.20 IE-TRANS,AFW-TDP-TM-P02,RPS-BME-CF-RTBAB 20 7.86E-9 1.09 IE-TRANS,AFW-TDP-FS-P02,RPS-ROD-CF-RCCAS 21 7.25E-9 1.00 IE-TRANS,AFW-TDP-TM-P02,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL Cut Set Report - TRANS 19 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 2.86E-7 100 1 9.99E-9 3.49 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FR-M002A,EPS-DGN-FR-DG2C 2 9.45E-9 3.31 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-RECIRC 3 7.51E-9 2.63 IE-TRANS,AFW-ACX-CF-MDPABR,AFW-TDP-FR-P02,HPI-XHE-XM-RECIRC 4 6.79E-9 2.37 IE-TRANS,DCP-BDC-LP-BUS1A,EPS-DGN-FR-DG2C,IAS-XHE-XM-EAS 5 6.70E-9 2.34 IE-TRANS,AFW-TDP-FR-P02,DCP-BDC-LP-BUS1A,EPS-DGN-FR-DG2C 6 6.64E-9 2.32 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FR-M002A,EPS-XHE-XM-STRT2C 7 6.28E-9 2.20 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-RECIRC 8 6.15E-9 2.15 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-RECIRC 9 4.76E-9 1.67 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FR-M002A,EPS-DGN-TM-DG2C 10 4.55E-9 1.59 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8812A 11 4.55E-9 1.59 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8811A 12 4.55E-9 1.59 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-MOV-CC-8706A 13 4.51E-9 1.58 IE-TRANS,DCP-BDC-LP-BUS1A,EPS-XHE-XM-STRT2C,IAS-XHE-XM-EAS 14 4.51E-9 1.58 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-TM-DG2C,HPI-XHE-XM-RECIRC A-3

LER 364-2014-002

  1. CCDP TOTAL% CUT SET 15 4.48E-9 1.57 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MDP-FS-P1A 16 4.46E-9 1.56 IE-TRANS,AFW-TDP-FR-P02,DCP-BDC-LP-BUS1A,EPS-XHE-XM-STRT2C 17 4.09E-9 1.43 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-RECIRC 18 3.76E-9 1.31 IE-TRANS,AFW-MDP-CF-START,AFW-TDP-FR-P02,HPI-XHE-XM-RECIRC 19 3.24E-9 1.13 IE-TRANS,DCP-BDC-LP-BUS1A,EPS-DGN-TM-DG2C,IAS-XHE-XM-EAS 20 3.20E-9 1.12 IE-TRANS,AFW-TDP-FR-P02,DCP-BDC-LP-BUS1A,EPS-DGN-TM-DG2C 21 3.03E-9 1.06 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,RHR-MOV-CC-8812A 22 3.03E-9 1.06 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,RHR-MOV-CC-8811A 23 3.03E-9 1.06 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-MOV-CC-8706A 24 2.98E-9 1.04 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,RHR-MDP-FS-P1A 25 2.96E-9 1.04 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-MOV-CC-8706A 26 2.96E-9 1.04 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8811A 27 2.96E-9 1.04 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8812A 28 2.94E-9 1.03 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-TM-DG2C,HPI-XHE-XM-RECIRC 29 2.91E-9 1.02 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MDP-FS-P1A 30 2.90E-9 1.01 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FS-M002A,EPS-DGN-FR-DG2C Cut Set Report - TRANS 21-14 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 1.15E-7 100 1 3.22E-8 28.01 IE-TRANS,CVC-XHE-XM-BOR,RPS-BME-CF-RTBAB 2 2.69E-8 23.37 IE-TRANS,CVC-XHE-XM-BOR,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 3 2.42E-8 21.05 IE-TRANS,CVC-XHE-XM-BOR,RPS-ROD-CF-RCCAS 4 1.82E-8 15.84 IE-TRANS,CVC-XHE-XM-BOR,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 5 3.22E-9 2.80 IE-TRANS,CVC-XHE-XM-RWSTXF,RPS-BME-CF-RTBAB 6 2.69E-9 2.34 IE-TRANS,CVC-XHE-XM-RWSTXF,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 7 2.42E-9 2.10 IE-TRANS,CVC-XHE-XM-RWSTXF,RPS-ROD-CF-RCCAS 8 2.08E-9 1.81 IE-TRANS,CVC-XHE-XM-BOR,RPS-UVL-CF-UVDAB,RPS-XHE-XE-SIGNL 9 1.82E-9 1.58 IE-TRANS,CVC-XHE-XM-RWSTXF,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL A-4

LER 364-2014-002 Referenced Events Event Description Probability ACP-BAC-LP-1F 4160 VAC BUS 1F IS UNAVAILABLE 3.33E-5 ACP-BAC-LP-1K 4160 VAC BUS 1K IS UNAVAILABLE 3.33E-5 AFW-ACX-CF- MDAFW PUMP A & B ROOM COOLER FTR DUE TO COMMON 9.50E-5 MDPABR CAUSE AFW-ACX-FR-MDPA MDAFW PUMP A ROOM COOLER FTR DUE TO RANDOM FAULTS 2.59E-3 AFW-MDP-CF-START CCF OF AFW MDPS TO START 4.76E-5 AFW-MDP-TM-P1A AFW MDP UNAVAILABLE DUE TO TEST AND MAINTENANCE 3.98E-3 AFW-TDP-FR-P02 TURBINE DRIVEN FEED PUMP P02 FAILS TO RUN 3.95E-2 AFW-TDP-FS-P02 TURBINE DRIVEN FEED PUMP P02 FAILS TO START 6.49E-3 AFW-TDP-TM-P02 FEED PUMP P02 IS IN TEST OR MAINTENANCE 5.39E-3 CVC-XHE-XM-BOR OPERATOR FAILS TO INITIATE EMERGENCY BORATION 2.00E-2 CVC-XHE-XM- OPERATOR FAILS TO TRANSFER CHG SUCTN TO RWST ON 2.00E-3 RWSTXF LOCCW DCP-BDC-LP-BUS1A 125 VDC BUS 1A FAILS 5.64E-6 EAS-MDC-FR-M002A EMERGENCY AIR COMPRESSOR Q1P18C002A FAILS TO RUN 5.89E-2 EAS-MDC-FS-M002A EMERGENCY AIR COMPRESSOR Q1P18C002A FAILS TO START 1.71E-2 EPS-DGN-FR-DG2C DIESEL GENERATOR 2C FAILS TO RUN 3.01E-2 EPS-DGN-FS-DG2C DIESEL GENERATOR 2C FAILS TO START 2.89E-3 EPS-DGN-TM-DG2C DG 2C UNAVAILABLE DUE TO TEST AND MAINTENANCE 1.43E-2 EPS-XHE-XM-STRT2C OPERATOR FAILS TO START/ALIGN DG 2C 2.00E-2 HPI-MOV-CC-8706A HPR/RHR RECIRC SUCTN VLV 8706A FAILS TO OPEN 9.63E-4 HPI-XHE-XM-FB OPERATOR FAILS TO INITIATE FEED AND BLEED COOLING 2.00E-2 HPI-XHE-XM-RECIRC OPERATOR FAILS TO START HIGH PRESSURE RECIRC 2.00E-3 IAS-XHE-XM-EAS OPERATOR FAILS TO ALIGN EMERGENCY AIR SYSTEM 4.00E-2 IE-TRANS TRANSIENT 1.00E+0 PPR-MOV-FC-8000A PORV 445A BLOCK VALVE IS CLOSED DURING FULL POWER 7.32E-2 PPR-MOV-FC-8000B PORV 444B BLOCK VALVE IS CLOSED DURING FULL POWER 7.32E-2 RCS-PHN-MODPOOR MODERATOR TEMP COEFFICIENT NOT ENOUGH NEGATIVE 1.40E-2 RCS-PHN-PL POWER AT HIGH LEVEL 9.00E-1 RHR-MDP-FS-P1A RHR PUMP 1A FAILS TO START 9.47E-4 RHR-MOV-CC-8811A PUMP 1A SUMP INBOARD SUCTN VLV 8811A FAILS TO OPEN 9.63E-4 RHR-MOV-CC-8812A PUMP 1A SUMP OUTBOARD SUCTN VLV 8812A FAILS TO OPEN 9.63E-4 RPS-BME-CF-RTBAB CCF OF RTB-A AND RTB-B (MECHANICAL) 1.61E-6 RPS-CCX-CF-6OF8 CCF 6 ANALOG PROCESS LOGIC MODULES IN 3 OF 4 1.83E-6 CHANNELS RPS-ROD-CF-RCCAS CCF 10 OR MORE RCCAS FAIL TO DROP 1.21E-6 RPS-TXX-CF-6OF8 CCF 6 BISTABLES IN 3 OF 4 CHANNELS 2.70E-6 RPS-UVL-CF-UVDAB CCF UV DRIVERS TRAINS A AND B (2 0F 2) 1.04E-5 RPS-XHE-XE-NSGNL OPERATOR FAILS TO RESPOND WITH NO RPS SIGNAL 5.00E-1 PRESENT RPS-XHE-XE-SIGNL OPERATOR FAILS TO RESPOND WITH RPS SIGNAL PRESENT 1.00E-2 A-5

LER 364-2014-002 Appendix B: Dominant Sequence Figure 1: Dominant Sequence TRANS-20 B-1

Final Precursor Analysis Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Joseph M. Farley Nuclear Manual Reactor Trip due to Loss of 2B Startup Plant, Unit 2 Auxiliary Transformer LER: 364-2014-002 Event Date: 10/14/2014 CCDP = 6x10-6 IR: 50-364/14-005 Plant Type: Pressurized-Water Reactor (PWR)

Westinghouse 3-Loop with Dry, Ambient Pressure Containment Plant Operating Mode (Reactor Power Level): Mode 1 (82% Reactor Power)

Analyst: Reviewer: Contributors: BC Review Date:

Jonathan DeJesus David Aird N/A 3/31/2016 EXECUTIVE

SUMMARY

On October 14, 2014, while conducting planned maintenance on emergency diesel generator (EDG) 2B, a lighting strike in the Unit 2 switchyard caused the 2B startup auxiliary transformer (SAT) to de-energize. The 2B SAT and 2B EDG provide the normal and backup power, respectively, to the 2G 4160 V bus that supplies power to the B train component cooling water (CCW) pumps and other loads. Since the loss of the 2B SAT and the 2B EDG unavailability affected the on-service train (i.e., the B train) of CCW, operators followed procedures and manually tripped the reactor. The reactor trip resulted in a valid actuation of the auxiliary feedwater system (AFW).

According to the modeling assumptions used in this Accident Sequence Precursor (ASP) analysis, the most likely core damage sequence is a transient initiating event (IE-TRANS) followed by the failure of AFW, failure of main feedwater, and failure of feed and bleed cooling.

This accident sequence accounts for approximately 63% of the conditional core damage probability (CCDP) for the event. This event was determined to be a precursor with a CCDP of 5.5x10-6.

EVENT DETAILS Event Description. On October 14, 2014, a lighting strike in the Unit 2 switchyard caused the 2B startup auxiliary transformer (SAT) to de-energize. The 2B SAT was the normal power supply to the 2G 4160 V bus that supplied power to the B train component cooling water (CCW) pumps and other loads. When the 2B SAT de-energized, power was lost to the B train CCW pumps that were aligned as the on-service train supplying cooling water to the reactor coolant pump (RCP) oil coolers and thermal barrier heat exchangers. Normally, the 2B emergency diesel generator (EDG) would automatically start and provide power to the B train CCW pumps.

However, with the 2B EDG unavailable due to planned maintenance, there was no automatic power supply to the B train CCW pumps. Procedures directed the operators to manually trip the reactor and stop all RCPs if the on-service train of CCW was affected. Accordingly, the licensee manually tripped the reactor and stopped all RCPs. The reactor trip resulted in a valid actuation of the auxiliary feedwater system. All other safety systems responded as designed. Additional information is provided in Reference 1 (licensee event report) and Reference 2 (inspection report).

Enclosure 1

LER 364-2014-002 Causes. The direct cause of this event was a loose termination from a missing nut in the power circuit breaker (PCB) 944 current transformer circuit connection to the instantaneous overcurrent relay, which in addition to the continued fault on the 500 kV bus side of the PCB 112 led to the B train loss of site power. The root cause was inadequate verification practices during wiring installations that led to the nut not being installed on its terminal.

Inspection Report/Significance Determination Process Result. The inspectors reviewed the event and determined that the licensee failed to take actions to mitigate the increased risk of a reactor trip with the B train of CCW as the on-service train while the 2B EDG was unavailable due to planned maintenance. The result was a self-revealing, Green finding. This LER is closed.

MODELING ASSUMPTIONS Analysis Type. The staff used version 8.21 of Farleys Units 1 and 2 Standardized Plant Analysis Risk (SPAR) model, created in September 2013, to perform the analysis (i.e., initiating event assessment). Farleys SPAR model is based on Unit 1, but the event occurred in Unit 2.

Therefore, surrogate components in Unit 1 were adjusted to account for the equivalent equipment affected in Unit 2. This event was modeled as a general transient initiating event.

Analysis Rules. The ASP program uses Significance Determination Process results for degraded conditions when available and appropriate to meet ASP Program needs. In this case, while the inspection program classified this event as a Green finding, an ASP analysis was performed consistent with ASP Program practices and guidance to analyze all initiating events.

Key Modeling Assumptions. The analysis contains the following modeling assumptions and basic event probability changes:

  • The probability of IE-TRANS (General Transient Initiating Event) was set to 1.0; all other initiating event probabilities were set to zero.
  • Basic event ACP-TFM-FC-SUT1B (230 to 4.2 kV Startup Transformer 1B Fails) was set to TRUE.
  • Basic event EPS-DGN-TM-DG1B (Diesel Generator 1B Unavailable due to Test and Maintenance) was set to TRUE.
  • EDG 2C is designated as the station blackout (SBO) diesel and can supply power to Unit 1 or Unit 2 when the 1B or 2B EDG is not available. Basic event EPS-DG2C-UNIT2 (Diesel 2C Required for SBO on Unit 2) was set to FALSE because EDG 2C1 was not required for an SBO event on the other unit (i.e., Unit 1, but modeled as Unit 2 in this analysis).

1 The staff considered setting the test and maintenance basic event for EDG 2C (EPS-DGN-TM-DG2C) to FALSE.

However, Farleys Technical Specifications (Reference 3 - see Condition E of Limiting Condition for Operation 3.8.1) do not preclude the licensee from placing EDG 2C in test and maintenance while another EDG is also undergoing test and maintenance. A sensitivity analysis was performed and it had a minimal reduction in CCDP.

2

LER 364-2014-002 ANALYSIS RESULTS CCDP. The point estimate CCDP for this event is 5.5x10-6. The ASP Program acceptance threshold is a CCDP of 1x10-6 or the CCDP equivalent of an uncomplicated reactor trip with a non-recoverable loss of main feedwater or loss of condenser heat sink, whichever is greater.

This CCDP equivalent is 1.7x10-6 for both cases. Therefore, this event resulted in a precursor for Farley, Unit 2.

Dominant Sequence. The dominant accident sequence is TRANS Sequence 20 (CCDP

= 3.5x10-6) that contributes approximately 63% of the total internal events CCDP. Figure 1 in Appendix B illustrates this sequence. The cut sets and sequences that contribute to the top 95%

and/or at least 1% of the total internal events CCDP are provided in Appendix A.

The events and component failures in TRANS Sequence 20 are:

  • Feed and bleed cooling fails.

REFERENCES

1. Southern Nuclear Operating Company, Inc., "Joseph M. Farley Nuclear Plant - Unit 2, Licensee Event Report 2014-002-00, Manual Reactor Trip due to Loss of 2B Startup Auxiliary Transformer and Loss of Offsite Power, dated December 12, 2014 (ML14346A391).
2. U.S. Nuclear Regulatory Commission, Joseph M. Farley Nuclear Plant - NRC Integrated Inspection Report 05000348/2014005; and 05000364/2014005 and Exercise of Enforcement Discretion, dated February 9, 2015 (ML15040A564).
3. Appendix A, Technical Specifications, to Joseph M. Farley Nuclear Plant, Unit 2 Renewed Facility Operating License No. NPF-8 (ML052780033 2).

2 Farley, Unit 2 uses the same Technical Specifications as Farley, Unit 1.

3

LER 364-2014-002 Appendix A: Analysis Results Summary of Conditional Event Changes Cond. Nominal Event Description Value Value ACP-TFM-FC-SUT1B 230 TO 4.2 KV STARTUP TRANSFORMER 1B FAILS TRUE 2.27E-5 EPS-DG2C-UNIT2 DIESEL 2C REQUIRED FOR SBO ON UNIT 2 FALSE 1.14E-2 DG 1B UNAVAILABLE DUE TO TEST AND EPS-DGN-TM-DG1B TRUE 1.43E-2 MAINTENANCE IE-TRANS TRANSIENT 1.00E+0a 6.90E-1

a. All other initiating event probabilities were set to zero.

Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

Event Tree Sequence CCDP  % Contribution Description TRANS 20 3.49E-6 63.2% /RPS, AFW, MFW, FAB TRANS 21-16 8.78E-7 15.9% RPS, RCSPRESS TRANS 21-15 7.22E-7 13.1% RPS, /RCSPRESS, MFW, AFW-A TRANS 19 2.86E-7 5.2% /RPS, AFW, MFW, /FAB, SSCR, HPR TRANS 21-14 1.15E-7 2.1% RPS, /RCSPRESS, MFW, /AFW-A, BORATION Total 5.52E-6 100.0%

Referenced Fault Trees Fault Tree Description AFW AUXILIARY FEEDWATER AFW-A AUXILIARY FEEDWATER SYSTEM BORATION EMERGENCY BORATION FAB FEED AND BLEED HPR HPR PRESSURE RECIRCULATION MFW MAIN FEEDWATER RCSPRESS RCS PRESSURE LIMITED RPS REACTOR TRIP SSCR SECONDARY SIDE COOLING RECOVERED Cut Set Report - TRANS 20 Only items contributing at least 1% to the total are displayed.

  1. CCDP TOTAL% CUT SET 3.49E-6 100 1 1.00E-6 28.71 IE-TRANS,ACP-BAC-LP-1F,EPS-DGN-FR-DG2C 2 6.66E-7 19.09 IE-TRANS,ACP-BAC-LP-1F,EPS-XHE-XM-STRT2C 3 4.78E-7 13.70 IE-TRANS,ACP-BAC-LP-1F,EPS-DGN-TM-DG2C 4 9.63E-8 2.76 IE-TRANS,ACP-BAC-LP-1F,EPS-DGN-FS-DG2C 5 9.45E-8 2.71 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-FB 6 7.51E-8 2.15 IE-TRANS,AFW-ACX-CF-MDPABR,AFW-TDP-FR-P02,HPI-XHE-XM-FB 7 6.28E-8 1.80 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-FB A-1

LER 364-2014-002

  1. CCDP TOTAL% CUT SET 8 6.15E-8 1.76 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-FB 9 4.51E-8 1.29 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-TM-DG2C,HPI-XHE-XM-FB 10 4.09E-8 1.17 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-FB 11 3.96E-8 1.13 IE-TRANS,ACP-BAC-LP-1K,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C 12 3.76E-8 1.08 IE-TRANS,AFW-MDP-CF-START,AFW-TDP-FR-P02,HPI-XHE-XM-FB Cut Set Report - TRANS 21-16 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 8.79E-7 100 1 1.18E-7 13.42 IE-TRANS,PPR-MOV-FC-8000A,RPS-BME-CF-RTBAB 2 1.18E-7 13.42 IE-TRANS,PPR-MOV-FC-8000B,RPS-BME-CF-RTBAB 3 9.83E-8 11.19 IE-TRANS,PPR-MOV-FC-8000B,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 4 9.83E-8 11.19 IE-TRANS,PPR-MOV-FC-8000A,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 5 8.86E-8 10.08 IE-TRANS,PPR-MOV-FC-8000A,RPS-ROD-CF-RCCAS 6 8.86E-8 10.08 IE-TRANS,PPR-MOV-FC-8000B,RPS-ROD-CF-RCCAS 7 6.66E-8 7.59 IE-TRANS,PPR-MOV-FC-8000B,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 8 6.66E-8 7.59 IE-TRANS,PPR-MOV-FC-8000A,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 9 2.03E-8 2.31 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,RPS-BME-CF-RTBAB 10 1.69E-8 1.93 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 11 1.52E-8 1.74 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,RPS-ROD-CF-RCCAS 12 1.15E-8 1.31 IE-TRANS,RCS-PHN-MODPOOR,RCS-PHN-PL,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL Cut Set Report - TRANS 21-15 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 7.22E-7 100 1 6.36E-8 8.81 IE-TRANS,AFW-TDP-FR-P02,RPS-BME-CF-RTBAB 2 5.31E-8 7.35 IE-TRANS,AFW-TDP-FR-P02,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 3 4.84E-8 6.71 IE-TRANS,EPS-DGN-FR-DG2C,RPS-BME-CF-RTBAB 4 4.78E-8 6.62 IE-TRANS,AFW-TDP-FR-P02,RPS-ROD-CF-RCCAS 5 4.04E-8 5.60 IE-TRANS,EPS-DGN-FR-DG2C,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 6 3.64E-8 5.04 IE-TRANS,EPS-DGN-FR-DG2C,RPS-ROD-CF-RCCAS 7 3.60E-8 4.98 IE-TRANS,AFW-TDP-FR-P02,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 8 3.22E-8 4.46 IE-TRANS,EPS-XHE-XM-STRT2C,RPS-BME-CF-RTBAB 9 2.74E-8 3.79 IE-TRANS,EPS-DGN-FR-DG2C,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL A-2

LER 364-2014-002

  1. CCDP TOTAL% CUT SET 10 2.69E-8 3.72 IE-TRANS,EPS-XHE-XM-STRT2C,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 11 2.42E-8 3.35 IE-TRANS,EPS-XHE-XM-STRT2C,RPS-ROD-CF-RCCAS 12 2.31E-8 3.20 IE-TRANS,EPS-DGN-TM-DG2C,RPS-BME-CF-RTBAB 13 1.93E-8 2.67 IE-TRANS,EPS-DGN-TM-DG2C,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 14 1.82E-8 2.52 IE-TRANS,EPS-XHE-XM-STRT2C,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 15 1.74E-8 2.40 IE-TRANS,EPS-DGN-TM-DG2C,RPS-ROD-CF-RCCAS 16 1.31E-8 1.81 IE-TRANS,EPS-DGN-TM-DG2C,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 17 1.05E-8 1.45 IE-TRANS,AFW-TDP-FS-P02,RPS-BME-CF-RTBAB 18 8.72E-9 1.21 IE-TRANS,AFW-TDP-FS-P02,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 19 8.68E-9 1.20 IE-TRANS,AFW-TDP-TM-P02,RPS-BME-CF-RTBAB 20 7.86E-9 1.09 IE-TRANS,AFW-TDP-FS-P02,RPS-ROD-CF-RCCAS 21 7.25E-9 1.00 IE-TRANS,AFW-TDP-TM-P02,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL Cut Set Report - TRANS 19 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 2.86E-7 100 1 9.99E-9 3.49 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FR-M002A,EPS-DGN-FR-DG2C 2 9.45E-9 3.31 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-RECIRC 3 7.51E-9 2.63 IE-TRANS,AFW-ACX-CF-MDPABR,AFW-TDP-FR-P02,HPI-XHE-XM-RECIRC 4 6.79E-9 2.37 IE-TRANS,DCP-BDC-LP-BUS1A,EPS-DGN-FR-DG2C,IAS-XHE-XM-EAS 5 6.70E-9 2.34 IE-TRANS,AFW-TDP-FR-P02,DCP-BDC-LP-BUS1A,EPS-DGN-FR-DG2C 6 6.64E-9 2.32 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FR-M002A,EPS-XHE-XM-STRT2C 7 6.28E-9 2.20 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-RECIRC 8 6.15E-9 2.15 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-XHE-XM-RECIRC 9 4.76E-9 1.67 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FR-M002A,EPS-DGN-TM-DG2C 10 4.55E-9 1.59 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8812A 11 4.55E-9 1.59 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8811A 12 4.55E-9 1.59 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-MOV-CC-8706A 13 4.51E-9 1.58 IE-TRANS,DCP-BDC-LP-BUS1A,EPS-XHE-XM-STRT2C,IAS-XHE-XM-EAS 14 4.51E-9 1.58 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-TM-DG2C,HPI-XHE-XM-RECIRC A-3

LER 364-2014-002

  1. CCDP TOTAL% CUT SET 15 4.48E-9 1.57 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MDP-FS-P1A 16 4.46E-9 1.56 IE-TRANS,AFW-TDP-FR-P02,DCP-BDC-LP-BUS1A,EPS-XHE-XM-STRT2C 17 4.09E-9 1.43 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-XHE-XM-RECIRC 18 3.76E-9 1.31 IE-TRANS,AFW-MDP-CF-START,AFW-TDP-FR-P02,HPI-XHE-XM-RECIRC 19 3.24E-9 1.13 IE-TRANS,DCP-BDC-LP-BUS1A,EPS-DGN-TM-DG2C,IAS-XHE-XM-EAS 20 3.20E-9 1.12 IE-TRANS,AFW-TDP-FR-P02,DCP-BDC-LP-BUS1A,EPS-DGN-TM-DG2C 21 3.03E-9 1.06 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,RHR-MOV-CC-8812A 22 3.03E-9 1.06 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,RHR-MOV-CC-8811A 23 3.03E-9 1.06 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,HPI-MOV-CC-8706A 24 2.98E-9 1.04 IE-TRANS,AFW-MDP-TM-P1A,AFW-TDP-FR-P02,EPS-XHE-XM-STRT2C,RHR-MDP-FS-P1A 25 2.96E-9 1.04 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,HPI-MOV-CC-8706A 26 2.96E-9 1.04 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8811A 27 2.96E-9 1.04 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MOV-CC-8812A 28 2.94E-9 1.03 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-TM-DG2C,HPI-XHE-XM-RECIRC 29 2.91E-9 1.02 IE-TRANS,AFW-ACX-FR-MDPA,AFW-TDP-FR-P02,EPS-DGN-FR-DG2C,RHR-MDP-FS-P1A 30 2.90E-9 1.01 IE-TRANS,DCP-BDC-LP-BUS1A,EAS-MDC-FS-M002A,EPS-DGN-FR-DG2C Cut Set Report - TRANS 21-14 Only items contributing at least 1% to the total are displayed.
  1. CCDP TOTAL% CUT SET 1.15E-7 100 1 3.22E-8 28.01 IE-TRANS,CVC-XHE-XM-BOR,RPS-BME-CF-RTBAB 2 2.69E-8 23.37 IE-TRANS,CVC-XHE-XM-BOR,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 3 2.42E-8 21.05 IE-TRANS,CVC-XHE-XM-BOR,RPS-ROD-CF-RCCAS 4 1.82E-8 15.84 IE-TRANS,CVC-XHE-XM-BOR,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 5 3.22E-9 2.80 IE-TRANS,CVC-XHE-XM-RWSTXF,RPS-BME-CF-RTBAB 6 2.69E-9 2.34 IE-TRANS,CVC-XHE-XM-RWSTXF,/RPS-CCP-TM-CHA,RPS-TXX-CF-6OF8,RPS-XHE-XE-NSGNL 7 2.42E-9 2.10 IE-TRANS,CVC-XHE-XM-RWSTXF,RPS-ROD-CF-RCCAS 8 2.08E-9 1.81 IE-TRANS,CVC-XHE-XM-BOR,RPS-UVL-CF-UVDAB,RPS-XHE-XE-SIGNL 9 1.82E-9 1.58 IE-TRANS,CVC-XHE-XM-RWSTXF,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL A-4

LER 364-2014-002 Referenced Events Event Description Probability ACP-BAC-LP-1F 4160 VAC BUS 1F IS UNAVAILABLE 3.33E-5 ACP-BAC-LP-1K 4160 VAC BUS 1K IS UNAVAILABLE 3.33E-5 AFW-ACX-CF- MDAFW PUMP A & B ROOM COOLER FTR DUE TO COMMON 9.50E-5 MDPABR CAUSE AFW-ACX-FR-MDPA MDAFW PUMP A ROOM COOLER FTR DUE TO RANDOM FAULTS 2.59E-3 AFW-MDP-CF-START CCF OF AFW MDPS TO START 4.76E-5 AFW-MDP-TM-P1A AFW MDP UNAVAILABLE DUE TO TEST AND MAINTENANCE 3.98E-3 AFW-TDP-FR-P02 TURBINE DRIVEN FEED PUMP P02 FAILS TO RUN 3.95E-2 AFW-TDP-FS-P02 TURBINE DRIVEN FEED PUMP P02 FAILS TO START 6.49E-3 AFW-TDP-TM-P02 FEED PUMP P02 IS IN TEST OR MAINTENANCE 5.39E-3 CVC-XHE-XM-BOR OPERATOR FAILS TO INITIATE EMERGENCY BORATION 2.00E-2 CVC-XHE-XM- OPERATOR FAILS TO TRANSFER CHG SUCTN TO RWST ON 2.00E-3 RWSTXF LOCCW DCP-BDC-LP-BUS1A 125 VDC BUS 1A FAILS 5.64E-6 EAS-MDC-FR-M002A EMERGENCY AIR COMPRESSOR Q1P18C002A FAILS TO RUN 5.89E-2 EAS-MDC-FS-M002A EMERGENCY AIR COMPRESSOR Q1P18C002A FAILS TO START 1.71E-2 EPS-DGN-FR-DG2C DIESEL GENERATOR 2C FAILS TO RUN 3.01E-2 EPS-DGN-FS-DG2C DIESEL GENERATOR 2C FAILS TO START 2.89E-3 EPS-DGN-TM-DG2C DG 2C UNAVAILABLE DUE TO TEST AND MAINTENANCE 1.43E-2 EPS-XHE-XM-STRT2C OPERATOR FAILS TO START/ALIGN DG 2C 2.00E-2 HPI-MOV-CC-8706A HPR/RHR RECIRC SUCTN VLV 8706A FAILS TO OPEN 9.63E-4 HPI-XHE-XM-FB OPERATOR FAILS TO INITIATE FEED AND BLEED COOLING 2.00E-2 HPI-XHE-XM-RECIRC OPERATOR FAILS TO START HIGH PRESSURE RECIRC 2.00E-3 IAS-XHE-XM-EAS OPERATOR FAILS TO ALIGN EMERGENCY AIR SYSTEM 4.00E-2 IE-TRANS TRANSIENT 1.00E+0 PPR-MOV-FC-8000A PORV 445A BLOCK VALVE IS CLOSED DURING FULL POWER 7.32E-2 PPR-MOV-FC-8000B PORV 444B BLOCK VALVE IS CLOSED DURING FULL POWER 7.32E-2 RCS-PHN-MODPOOR MODERATOR TEMP COEFFICIENT NOT ENOUGH NEGATIVE 1.40E-2 RCS-PHN-PL POWER AT HIGH LEVEL 9.00E-1 RHR-MDP-FS-P1A RHR PUMP 1A FAILS TO START 9.47E-4 RHR-MOV-CC-8811A PUMP 1A SUMP INBOARD SUCTN VLV 8811A FAILS TO OPEN 9.63E-4 RHR-MOV-CC-8812A PUMP 1A SUMP OUTBOARD SUCTN VLV 8812A FAILS TO OPEN 9.63E-4 RPS-BME-CF-RTBAB CCF OF RTB-A AND RTB-B (MECHANICAL) 1.61E-6 RPS-CCX-CF-6OF8 CCF 6 ANALOG PROCESS LOGIC MODULES IN 3 OF 4 1.83E-6 CHANNELS RPS-ROD-CF-RCCAS CCF 10 OR MORE RCCAS FAIL TO DROP 1.21E-6 RPS-TXX-CF-6OF8 CCF 6 BISTABLES IN 3 OF 4 CHANNELS 2.70E-6 RPS-UVL-CF-UVDAB CCF UV DRIVERS TRAINS A AND B (2 0F 2) 1.04E-5 RPS-XHE-XE-NSGNL OPERATOR FAILS TO RESPOND WITH NO RPS SIGNAL 5.00E-1 PRESENT RPS-XHE-XE-SIGNL OPERATOR FAILS TO RESPOND WITH RPS SIGNAL PRESENT 1.00E-2 A-5

LER 364-2014-002 Appendix B: Dominant Sequence Figure 1: Dominant Sequence TRANS-20 B-1

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