ML16237A427

ASP Analysis - Reject - Peach Bottom HPCI System Inoperable for 17 Hours Due to Flow Controller Failure - LER 278-2015-001

ML16237A427
Person / Time
Site:	Peach Bottom
Issue date:	08/23/2016
From:	David Aird NRC/RES/DRA/PRAB
To:
David Aird 301-415-0634
References
IR 2016001, LER: 278-2015-001
Download: ML16237A427 (10)

Text

1 ASP Program Analysis - Reject Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Peach Bottom Atomic Power Station, Unit 3 HPCI system inoperable for 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> due to flow controller failure Event Date: 12/31/2015 LER: 278-2015-001 IR: 05000278/2016001 CCDP = 4x10-8 Plant Type: General Electric BWR/4 with a Mark I Containment Plant Operating Mode (Reactor Power Level): Mode 1 (100% Reactor Power)

Analyst:

Erulappa Chelliah Reviewer:

David Aird Contributors:

N/A BC Approved Date:

8/23/2016 EVENT DETAILS Event Description. On December 31, 2015, at approximately 6:30 a.m., during shift turnover panel walk-downs, an operator identified that flow-controller output indication of the high pressure coolant injection (HPCI) system was showing zero percent. The controller was in automatic mode with the set-point at 5000-gallons per minute, which would typically result in a controller output value of 100%. This discovered condition would have prevented the HPCI system from performing its design safety function in the event of an accident. The operators declared the HPCI system to be inoperable per Technical Specifications (TS) and entered the appropriate action statements of the TS.

The operators observed the controller at 100% at 4:00 a.m. on December 31. It was during the 6:30 a.m. walk-down when the controller was observed showing zero percent. After 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of undetected inoperability of the HPCI flow controller, troubleshooting of the HPCI system by the operators determined that a signal converter in the HPCI control circuitry had failed, resulting in the HPCI system not being capable of providing a sufficient flow rate if it had been demanded to mitigate a design basis event.

Then, the licensee took a period of next 14.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at power to replace the failed signal converter of the HPCI flow controller. After a successful replacement of the flow controller, the operators satisfactorily tested the HPCI system and returned the HPCI system to an operable status at approximately 9:10 p.m. The elapsed time from discovery to the time when the system was returned to service was approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> and 40 minutes. The maximum period of inoperability is 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> and 10 minutes if the controller failed immediately after the 4:00 a.m.

walk down.

In summary, the operators were operating the Peach Bottom Unit 3 at power with an inoperable HPCI system for a condition period of approximately 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />.

The licensee reported this condition to the USNRC, on December 31, at approximately 1:15 p.m., pursuant to the requirements of 10CFR 50.72(b)(3)(v)(D). The licensee also reported this inoperable condition of the HPCI system, in a licensee event report (LER), in accordance with 10 CFR Part 50.73(a)(2)(v)(D), as an event or condition that could have prevented the fulfillment of the safety function of a system at power to mitigate a design basis hazard event (Reference-1).

LER 278-2015-001 2

Cause. The operators found the inoperability cause of the HPCI system to be a prior failure of a signal converter in the HPCI control circuitry. Based on a failure analysis of the failed flow-controller, the operators determined that a transistor inside the signal converter failed. The failure of the signal converter was determined to be a latent manufacturing issue resulting in an infant mortality of the converter.

MODELING Basis for ASP Analysis/SDP Results. The ASP Program uses Significance Determination Process (SDP) results for degraded conditions when available and applicable. The ASP Program performs independent analyses for initiating events. ASP analyses of initiating events account for all failures/degraded conditions and unavailabilities (e.g., equipment out for test/maintenance) that occurred during the event, regardless of licensee performance.1 Region I inspectors reviewed the LER and other related information and determined no findings or violations of NRC requirements existed. Region I closed the LER in Inspection Report (IR) 05000278/2016001 (Reference-2).

An independent ASP analysis is required because no SDP analysis was performed for the event. Given that it was a failure/unavailability of a safety system, the risk impact (if any) should be analyzed and documented.

Analysis Type. A condition analysis was performed using the Peach Bottom Unit 3 Standardized Plant Analysis Risk (SPAR) model Revision 8.21, created in May 2014.

Using the SAPHIRE8 code, the analyst conducted a condition risk analysis case (see Appendix A) to estimate the increase in core damage probability (CDP) due to an as-found inoperability of the HPCI system.

SPAR Model Modifications. None Key Modeling Assumptions. The following assumptions were determined to be significant to the modeling of this event:

A condition assessment was performed with a duration of 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />.

The probability of basic event HCI-TDP-FS-TRAIN (HPCI Pump Fails to Start) was set to 1.0. Setting this basic event to TRUE would have an impact on the common cause probability of other turbine driven pumps in the SPAR model. The analyst determined that other controllers were not susceptible to this failure mode.

There were no other structures, systems, or components out of service that contributed to this event.

ANALYSIS RESULTS CDP/Rejection Basis. The point estimate CDP for this event is 4.4x10-8. The ASP Program threshold is a CDP of greater than 1x10-6. Therefore, this event is not a precursor and is screened out of the ASP Program.

1 ASP analyses also account for any degraded condition(s) that were identified after the initiating event occurred if the failure/degradation exposure period(s) overlapped the initiating event date.

LER 278-2015-001 3

Dominant Sequence. The dominant accident sequence is LOACB E13 Sequence 62 (CDP =

9x10-9) that contributes approximately 20% of the total internal events CDP. The cut sets/sequences that contribute to the top 95% and/or at least 1% of the total internal events CDP are provided in Appendix A.

The events and important component/system failures in LOACB E13 Sequence 62 are:

Loss of 4160V AC Bus E13 occurs (initiating event), and Operators fail to perform a manual action associated with depressurizing the reactor.

REFERENCES

1. Peach Bottom Atomic Power Station Unit 3, Loss of High Pressure Coolant Injection System Function as a Result of Failed Flow Controller Signal Converter, LER 278-2015-001-00, dated February 26, 2016 (ML16057A011).

2. U. S. Nuclear Regulatory Commission, Peach Bottom Atomic Power Station, Unit 3 - NRC Integrated Inspection Report 05000278/2016001, dated May 4, 2016 (ML16125A073).

LER 278-2015-001 4

Appendix A: SAPHIRE 8 Worksheet Condition Assessment Summary Duration 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> CCDP 5.05E-8 CDP 6.55E-9 CDP 4.39E-8 Summary of Conditional Event Changes Event Description Cond Type Cond Value Nominal Type Nominal Value HCI-TDP-FS-TRAIN HPCI PUMP FAILS TO START 1

1.00E+0 1

6.49E-3 Implied Event Changes as per RASP Guidance Event Description Cond Value Nominal Value HCI-TDP-FR-TRAIN HPCI PUMP TRAIN FAILS TO RUN GIVEN IT STARTED 1.00E+0 3.95E-2 HCI-TDP-TM-TRAIN HPCI PUMP TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE True 1.13E-2 Event Tree Dominant Results Only items contributing at least 1.0% to the total CCDP are displayed.

E V E N T T R E E CCDP CDP CDP D E S C R I P T I O N LOCHS 1.75E-8 1.58E-9 1.59E-8 PEACH BOTTOM LOSS OF CONDENSER HEAT SINK LOACB-E13 1.30E-8 1.08E-9 1.19E-8 PEACH BOTTOM LOSS OF AC BUS E13 LOMFW 8.65E-9 7.55E-10 7.90E-9 PEACH BOTTOM LOSS OF MAIN FEEDWATER LOOPGR 2.31E-9 5.35E-10 1.78E-9 PEACH BOTTOM LOSS OF OFFSITE POWER (GRID-RELATED LOIAS 1.92E-9 1.96E-10 1.72E-9 PEACH BOTTOM LOSS INSTRUMENT AIR LOOPSC 1.84E-9 3.32E-10 1.51E-9 PEACH BOTTOM LOSS OF OFFSITE POWER (SWITCHYARD-CENTERED)

MANSD 1.23E-9 1.60E-10 1.07E-9 PEACH BOTTOM MANUAL SHUTDOWN TRANS 9.20E-10 2.92E-10 6.28E-10 PEACH BOTTOM GENERAL TRANSIENT LOOPWR 8.02E-10 2.29E-10 5.73E-10 PEACH BOTTOM LOSS OF OFFSITE POWER (WEATHER-RELATED)

Total 5.05E-8 6.55E-9 4.39E-8 Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

E V E N T T R E E S E Q U E N C E CCDP CDP CDP D E S C R I P T I O N LOACB-E13 62 9.72E-9 7.57E-10 8.96E-9

/RPS, /SRV, PCS, HPI, DEP LOCHS 53 8.71E-9 7.40E-10 7.97E-9

/RPS, /SRV, HPI, DEP LOCHS 52 8.70E-9 7.38E-10 7.97E-9

/RPS, /SRV, HPI, /DEP, CDS, LPI, VA LOMFW 59 4.31E-9 3.66E-10 3.95E-9

/RPS, /SRV, HPI, /DEP, CDS, LPI, VA LOMFW 60 4.31E-9 3.66E-10 3.95E-9

/RPS, /SRV, HPI, DEP

LER 278-2015-001 5

E V E N T T R E E S E Q U E N C E CCDP CDP CDP D E S C R I P T I O N LOACB-E13 61 3.24E-9 2.52E-10 2.99E-9

/RPS, /SRV, PCS, HPI, /DEP, CDS, LPI, VA LOIAS 65 1.41E-9 1.16E-10 1.29E-9

/RPS, /SRV, HPI, DEP LOOPGR 34 1.14E-9 4.32E-10 7.09E-10

/RPS, /EPS, /SRV, HPI, /DEP, LPI, VA LOOPGR 35 7.68E-10 6.32E-11 7.05E-10

/RPS, /EPS, /SRV, HPI, DEP LOOPSC 34 8.49E-10 2.47E-10 6.02E-10

/RPS, /EPS, /SRV, HPI, /DEP, LPI, VA LOOPSC 35 6.55E-10 5.38E-11 6.01E-10

/RPS, /EPS, /SRV, HPI, DEP MANSD 62 5.93E-10 5.68E-11 5.36E-10

/RPS, PCS, HPI, DEP MANSD 61 5.86E-10 5.14E-11 5.35E-10

/RPS, PCS, HPI, /DEP, CDS, LPI, VA Total 5.05E-8 6.55E-9 4.39E-8 Referenced Fault Trees Fault Tree Description CDS CONDENSATE DEP MANUAL REACTOR DEPRESS HPI HIGH PRESSURE INJECTION LPI LOW PRESSURE INJECTION PCS POWER CONVERSION SYSTEM VA ALTERNATE LOW PRESS INJECTION Cut Set Report - LOACB-E13 62 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T Total 5.01E-6 100 Displaying 2 Cut Sets. (2 Original) 1 3.34E-6 66.69 IE-LOACB-E13,ADS-XHE-XM-ADSBT 2

1.67E-6 33.34 IE-LOACB-E13,ADS-XHE-XM-MDEPR Cut Set Report - LOCHS 53 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 4.49E-6 100 Displaying 32 Cut Sets. (32 Original) 1 2.75E-6 61.15 IE-LOCHS,ADS-XHE-XM-MDEPR,RCI-TDP-FR-TRAIN 2

7.61E-7 16.95 IE-LOCHS,ADS-XHE-XM-MDEPR,RCI-TDP-TM-TRAIN 3

4.51E-7 10.05 IE-LOCHS,ADS-XHE-XM-MDEPR,RCI-TDP-FS-TRAIN 4

2.09E-7 4.64 IE-LOCHS,ADS-XHE-XM-MDEPR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 5

1.38E-7 3.08 IE-LOCHS,ADS-XHE-XM-MDEPR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 6

6.95E-8 1.55 IE-LOCHS,ADS-XHE-XM-MDEPR,RCI-XHE-XO-ERROR 7

6.69E-8 1.49 IE-LOCHS,ADS-XHE-XM-MDEPR,RCI-MOV-CC-INJEC Cut Set Report - LOCHS 52 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 4.48E-6 100 Displaying 23 Cut Sets. (23 Original) 1 2.75E-6 61.22 IE-LOCHS,LPI-XHE-XM-ERROR,RCI-TDP-FR-TRAIN

LER 278-2015-001 6

P R O B/F R E Q T O T AL%

C U T S E T 2

7.61E-7 16.97 IE-LOCHS,LPI-XHE-XM-ERROR,RCI-TDP-TM-TRAIN 3

4.51E-7 10.06 IE-LOCHS,LPI-XHE-XM-ERROR,RCI-TDP-FS-TRAIN 4

2.09E-7 4.65 IE-LOCHS,LPI-XHE-XM-ERROR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 5

1.38E-7 3.09 IE-LOCHS,LPI-XHE-XM-ERROR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 6

6.95E-8 1.55 IE-LOCHS,LPI-XHE-XM-ERROR,RCI-XHE-XO-ERROR 7

6.69E-8 1.49 IE-LOCHS,LPI-XHE-XM-ERROR,RCI-MOV-CC-INJEC Cut Set Report - LOMFW 59 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 2.22E-6 100 Displaying 23 Cut Sets. (23 Original) 1 1.36E-6 61.22 IE-LOMFW,LPI-XHE-XM-ERROR,RCI-TDP-FR-TRAIN 2

3.77E-7 16.97 IE-LOMFW,LPI-XHE-XM-ERROR,RCI-TDP-TM-TRAIN 3

2.24E-7 10.06 IE-LOMFW,LPI-XHE-XM-ERROR,RCI-TDP-FS-TRAIN 4

1.03E-7 4.65 IE-LOMFW,LPI-XHE-XM-ERROR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 5

6.86E-8 3.09 IE-LOMFW,LPI-XHE-XM-ERROR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 6

3.45E-8 1.55 IE-LOMFW,LPI-XHE-XM-ERROR,RCI-XHE-XO-ERROR 7

3.32E-8 1.49 IE-LOMFW,LPI-XHE-XM-ERROR,RCI-MOV-CC-INJEC Cut Set Report - LOMFW 60 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 2.22E-6 100 Displaying 26 Cut Sets. (26 Original) 1 1.36E-6 61.22 IE-LOMFW,ADS-XHE-XM-MDEPR,RCI-TDP-FR-TRAIN 2

3.77E-7 16.97 IE-LOMFW,ADS-XHE-XM-MDEPR,RCI-TDP-TM-TRAIN 3

2.24E-7 10.06 IE-LOMFW,ADS-XHE-XM-MDEPR,RCI-TDP-FS-TRAIN 4

1.03E-7 4.65 IE-LOMFW,ADS-XHE-XM-MDEPR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 5

6.86E-8 3.09 IE-LOMFW,ADS-XHE-XM-MDEPR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 6

3.45E-8 1.55 IE-LOMFW,ADS-XHE-XM-MDEPR,RCI-XHE-XO-ERROR 7

3.32E-8 1.49 IE-LOMFW,ADS-XHE-XM-MDEPR,RCI-MOV-CC-INJEC Cut Set Report - LOACB-E13 61 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T Total 1.67E-6 100 Displaying 1 Cut Sets. (1 Original) 1 1.67E-6 100.00 IE-LOACB-E13,LPI-XHE-XM-ERROR Cut Set Report - LOIAS 65 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 7.25E-7 100 Displaying 32 Cut Sets. (32 Original) 1 2.96E-7 40.82 IE-LOIAS,ADS-XHE-XM-ADSBT,RCI-TDP-FR-TRAIN 2

1.48E-7 20.41 IE-LOIAS,ADS-XHE-XM-MDEPR,RCI-TDP-FR-TRAIN

LER 278-2015-001 7

P R O B/F R E Q T O T AL%

C U T S E T 3

8.20E-8 11.31 IE-LOIAS,ADS-XHE-XM-ADSBT,RCI-TDP-TM-TRAIN 4

4.86E-8 6.71 IE-LOIAS,ADS-XHE-XM-ADSBT,RCI-TDP-FS-TRAIN 5

4.10E-8 5.66 IE-LOIAS,ADS-XHE-XM-MDEPR,RCI-TDP-TM-TRAIN 6

2.43E-8 3.35 IE-LOIAS,ADS-XHE-XM-MDEPR,RCI-TDP-FS-TRAIN 7

2.25E-8 3.10 IE-LOIAS,ADS-XHE-XM-ADSBT,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 8

1.49E-8 2.06 IE-LOIAS,ADS-XHE-XM-ADSBT,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 9

1.12E-8 1.55 IE-LOIAS,ADS-XHE-XM-MDEPR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 10 7.49E-9 1.03 IE-LOIAS,ADS-XHE-XM-ADSBT,RCI-XHE-XO-ERROR 11 7.46E-9 1.03 IE-LOIAS,ADS-XHE-XM-MDEPR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER Cut Set Report - LOOPGR 34 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 5.88E-7 100 Displaying 70 Cut Sets. (70 Original) 1 2.41E-7 40.99 IE-LOOPGR,LPI-XHE-XM-ERROR,RCI-TDP-FR-TRAIN 2

1.40E-7 23.82 IE-LOOPGR,CWG-XHE-XL-NR01H,EPS-XHE-XL-NR01H,EPS-XHE-XM-RCOOL,OEP-XHE-XL-NR01HGR 3

6.68E-8 11.36 IE-LOOPGR,LPI-XHE-XM-ERROR,RCI-TDP-TM-TRAIN 4

3.96E-8 6.74 IE-LOOPGR,LPI-XHE-XM-ERROR,RCI-TDP-FS-TRAIN 5

1.83E-8 3.11 IE-LOOPGR,LPI-XHE-XM-ERROR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 6

1.22E-8 2.07 IE-LOOPGR,LPI-XHE-XM-ERROR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 7

1.02E-8 1.73 IE-LOOPGR,CWG-XHE-XL-NR01H,EPS-DGN-FR-DGC,EPS-DGN-TM-DGD,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HGR,OEP-XHE-XX-NR01HGR1 8

1.02E-8 1.73 IE-LOOPGR,CWG-XHE-XL-NR01H,EPS-DGN-FR-DGD,EPS-DGN-TM-DGC,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HGR,OEP-XHE-XX-NR01HGR1 9

6.18E-9 1.05 IE-LOOPGR,CWG-XHE-XL-NR01H,EPS-DGN-FR-DGC,EPS-DGN-FR-DGD,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HGR,OEP-XHE-XX-NR01HGR2 10 6.10E-9 1.04 IE-LOOPGR,LPI-XHE-XM-ERROR,RCI-XHE-XO-ERROR Cut Set Report - LOOPGR 35 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 3.96E-7 100 Displaying 43 Cut Sets. (43 Original) 1 2.41E-7 60.85 IE-LOOPGR,ADS-XHE-XM-MDEPR,RCI-TDP-FR-TRAIN 2

6.68E-8 16.87 IE-LOOPGR,ADS-XHE-XM-MDEPR,RCI-TDP-TM-TRAIN 3

3.96E-8 10.00 IE-LOOPGR,ADS-XHE-XM-MDEPR,RCI-TDP-FS-TRAIN 4

1.83E-8 4.62 IE-LOOPGR,ADS-XHE-XM-MDEPR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 5

1.22E-8 3.07 IE-LOOPGR,ADS-XHE-XM-MDEPR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 6

6.10E-9 1.54 IE-LOOPGR,ADS-XHE-XM-MDEPR,RCI-XHE-XO-ERROR

LER 278-2015-001 8

P R O B/F R E Q T O T AL%

C U T S E T 7

5.87E-9 1.48 IE-LOOPGR,ADS-XHE-XM-MDEPR,RCI-MOV-CC-INJEC Cut Set Report - LOOPSC 34 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 4.38E-7 100 Displaying 64 Cut Sets. (64 Original) 1 2.05E-7 46.94 IE-LOOPSC,LPI-XHE-XM-ERROR,RCI-TDP-FR-TRAIN 2

7.28E-8 16.62 IE-LOOPSC,CWG-XHE-XL-NR01H,EPS-XHE-XL-NR01H,EPS-XHE-XM-RCOOL,OEP-XHE-XL-NR01HSC 3

5.69E-8 13.01 IE-LOOPSC,LPI-XHE-XM-ERROR,RCI-TDP-TM-TRAIN 4

3.38E-8 7.72 IE-LOOPSC,LPI-XHE-XM-ERROR,RCI-TDP-FS-TRAIN 5

1.56E-8 3.56 IE-LOOPSC,LPI-XHE-XM-ERROR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 6

1.04E-8 2.37 IE-LOOPSC,LPI-XHE-XM-ERROR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 7

5.41E-9 1.24 IE-LOOPSC,CWG-XHE-XL-NR01H,EPS-DGN-FR-DGC,EPS-DGN-TM-DGD,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HSC,OEP-XHE-XX-NR01HSC1 8

5.41E-9 1.24 IE-LOOPSC,CWG-XHE-XL-NR01H,EPS-DGN-FR-DGD,EPS-DGN-TM-DGC,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HSC,OEP-XHE-XX-NR01HSC1 9

5.20E-9 1.19 IE-LOOPSC,LPI-XHE-XM-ERROR,RCI-XHE-XO-ERROR 10 5.01E-9 1.14 IE-LOOPSC,LPI-XHE-XM-ERROR,RCI-MOV-CC-INJEC Cut Set Report - LOOPSC 35 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 3.37E-7 100 Displaying 39 Cut Sets. (39 Original) 1 2.05E-7 60.89 IE-LOOPSC,ADS-XHE-XM-MDEPR,RCI-TDP-FR-TRAIN 2

5.69E-8 16.88 IE-LOOPSC,ADS-XHE-XM-MDEPR,RCI-TDP-TM-TRAIN 3

3.38E-8 10.01 IE-LOOPSC,ADS-XHE-XM-MDEPR,RCI-TDP-FS-TRAIN 4

1.56E-8 4.62 IE-LOOPSC,ADS-XHE-XM-MDEPR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 5

1.04E-8 3.07 IE-LOOPSC,ADS-XHE-XM-MDEPR,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 6

5.20E-9 1.54 IE-LOOPSC,ADS-XHE-XM-MDEPR,RCI-XHE-XO-ERROR 7

5.01E-9 1.48 IE-LOOPSC,ADS-XHE-XM-MDEPR,RCI-MOV-CC-INJEC Cut Set Report - MANSD 62 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 3.06E-7 100 Displaying 112 Cut Sets. (112 Original) 1 1.08E-7 35.30 IE-MANSD,ADS-XHE-XM-MDEPR,MSS-TBV-CC-BYPAS,RCI-TDP-FR-TRAIN 2

2.99E-8 9.78 IE-MANSD,ADS-XHE-XM-MDEPR,MSS-TBV-CC-BYPAS,RCI-TDP-TM-TRAIN 3

2.57E-8 8.40 IE-MANSD,ADS-XHE-XM-MDEPR,PCS-XHE-XO-ERROR,RCI-TDP-FR-TRAIN 4

2.44E-8 7.99 IE-MANSD,ADS-XHE-XM-MDEPR,CDS-AOV-CC-MKUP1,RCI-TDP-FR-TRAIN

LER 278-2015-001 9

P R O B/F R E Q T O T AL%

C U T S E T 5

2.44E-8 7.99 IE-MANSD,ADS-XHE-XM-MDEPR,CDS-AOV-CC-MKUP2,RCI-TDP-FR-TRAIN 6

1.77E-8 5.80 IE-MANSD,ADS-XHE-XM-MDEPR,MSS-TBV-CC-BYPAS,RCI-TDP-FS-TRAIN 7

8.19E-9 2.68 IE-MANSD,ADS-XHE-XM-MDEPR,MSS-TBV-CC-BYPAS,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 8

7.12E-9 2.33 IE-MANSD,ADS-XHE-XM-MDEPR,PCS-XHE-XO-ERROR,RCI-TDP-TM-TRAIN 9

6.77E-9 2.22 IE-MANSD,ADS-XHE-XM-MDEPR,CDS-AOV-CC-MKUP2,RCI-TDP-TM-TRAIN 10 6.77E-9 2.22 IE-MANSD,ADS-XHE-XM-MDEPR,CDS-AOV-CC-MKUP1,RCI-TDP-TM-TRAIN 11 5.44E-9 1.78 IE-MANSD,ADS-XHE-XM-MDEPR,MSS-TBV-CC-BYPAS,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 12 4.22E-9 1.38 IE-MANSD,ADS-XHE-XM-MDEPR,PCS-XHE-XO-ERROR,RCI-TDP-FS-TRAIN 13 4.01E-9 1.31 IE-MANSD,ADS-XHE-XM-MDEPR,CDS-AOV-CC-MKUP1,RCI-TDP-FS-TRAIN 14 4.01E-9 1.31 IE-MANSD,ADS-XHE-XM-MDEPR,CDS-AOV-CC-MKUP2,RCI-TDP-FS-TRAIN Cut Set Report - MANSD 61 Only items contributing at least 1% to the total are displayed.

P R O B/F R E Q T O T AL%

C U T S E T 3.02E-7 100 Displaying 88 Cut Sets. (88 Original) 1 1.08E-7 35.70 IE-MANSD,LPI-XHE-XM-ERROR,MSS-TBV-CC-BYPAS,RCI-TDP-FR-TRAIN 2

2.99E-8 9.90 IE-MANSD,LPI-XHE-XM-ERROR,MSS-TBV-CC-BYPAS,RCI-TDP-TM-TRAIN 3

2.57E-8 8.50 IE-MANSD,LPI-XHE-XM-ERROR,PCS-XHE-XO-ERROR,RCI-TDP-FR-TRAIN 4

2.44E-8 8.08 IE-MANSD,CDS-AOV-CC-MKUP2,LPI-XHE-XM-ERROR,RCI-TDP-FR-TRAIN 5

2.44E-8 8.08 IE-MANSD,CDS-AOV-CC-MKUP1,LPI-XHE-XM-ERROR,RCI-TDP-FR-TRAIN 6

1.77E-8 5.87 IE-MANSD,LPI-XHE-XM-ERROR,MSS-TBV-CC-BYPAS,RCI-TDP-FS-TRAIN 7

8.19E-9 2.71 IE-MANSD,LPI-XHE-XM-ERROR,MSS-TBV-CC-BYPAS,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 8

7.12E-9 2.36 IE-MANSD,LPI-XHE-XM-ERROR,PCS-XHE-XO-ERROR,RCI-TDP-TM-TRAIN 9

6.77E-9 2.24 IE-MANSD,CDS-AOV-CC-MKUP2,LPI-XHE-XM-ERROR,RCI-TDP-TM-TRAIN 10 6.77E-9 2.24 IE-MANSD,CDS-AOV-CC-MKUP1,LPI-XHE-XM-ERROR,RCI-TDP-TM-TRAIN 11 5.44E-9 1.80 IE-MANSD,LPI-XHE-XM-ERROR,MSS-TBV-CC-BYPAS,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 12 4.22E-9 1.40 IE-MANSD,LPI-XHE-XM-ERROR,PCS-XHE-XO-ERROR,RCI-TDP-FS-TRAIN 13 4.01E-9 1.33 IE-MANSD,CDS-AOV-CC-MKUP2,LPI-XHE-XM-ERROR,RCI-TDP-FS-TRAIN

LER 278-2015-001 10 P R O B/F R E Q T O T AL%

C U T S E T 14 4.01E-9 1.33 IE-MANSD,CDS-AOV-CC-MKUP1,LPI-XHE-XM-ERROR,RCI-TDP-FS-TRAIN Referenced Events Event Description Probability ADS-XHE-XM-ADSBT OPERATOR FAILS TO VALVE IN ADS NITROGEN BOTTLE BANK 1.00E-3 ADS-XHE-XM-MDEPR OPERATOR FAILS TO DEPRESSURIZE THE REACTOR 5.00E-4 CDS-AOV-CC-MKUP1 MAKEUP PATH 1 FAILS 9.51E-4 CDS-AOV-CC-MKUP2 MAKEUP PATH 2 FAILS 9.51E-4 CWG-XHE-XL-NR01H OPERATOR FAILS TO ESTABLISH CONOWINGO TIE LINE SETUP IN 1 HOUR 2.00E-2 EPS-DGN-FR-DGC DIESEL GENERATOR C FAILS TO RUN 3.01E-2 EPS-DGN-FR-DGD DIESEL GENERATOR D FAILS TO RUN 3.01E-2 EPS-DGN-TM-DGC DG C IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 EPS-DGN-TM-DGD DG D IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 EPS-XHE-XL-NR01H OPERATOR FAILS TO RECOVER EMERGENCY DIESEL IN 1 HR 8.71E-1 EPS-XHE-XM-RCOOL OPERATOR FAILS TO ESTABLISH ROOM COOLING W/OUT EHV 1.00E-3 IE-LOACB-E13 LOSS OF 4160 VAC BUS E13 (30A15) 3.34E-3 IE-LOCHS LOSS OF CONDENSER HEAT SINK 1.39E-1 IE-LOIAS LOSS OF INSTRUMENT AIR 7.49E-3 IE-LOMFW LOSS OF FEEDWATER 6.89E-2 IE-LOOPGR LOSS OF OFFSITE POWER INITIATOR (GRID-RELATED) 1.22E-2 IE-LOOPSC LOOP INITIATOR (SWITCHYARD-CENTERED) 1.04E-2 IE-MANSD MANUAL SHUTDOWN 1.30E+0 LPI-XHE-XM-ERROR OPERATOR FAILS TO CONTROL LOW PRESSURE INJECTION 5.00E-4 MSS-TBV-CC-BYPAS TURBINE BYPASS VALVES FAIL TO OPEN 4.20E-3 OEP-XHE-XL-NR01HGR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR (GRID-RELATED) 6.59E-1 OEP-XHE-XL-NR01HSC OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR (SWITCHYARD) 4.01E-1 OEP-XHE-XX-NR01HGR1 CONVOLUTION FACTOR FOR 1FTR-OPR (1HR-GR AVAIL) 1.68E-1 OEP-XHE-XX-NR01HGR2 CONVOLUTION FACTOR FOR 2FTR-OPR (1HR-GR AVAIL) 4.88E-2 OEP-XHE-XX-NR01HSC1 CONVOLUTION FACTOR FOR 1FTR-OPR (1HR-SC AVAIL) 1.72E-1 PCS-XHE-XO-ERROR OPERATOR FAILS TO MAINTAIN FEEDWATER INJECTION 1.00E-3 RCI-MOV-CC-INJEC RCIC INJECTION VALVE CAUSES FAILURE TO START 9.63E-4 RCI-MOV-FC-XFER RCIC FAILS TO TRANSFER DURING RECIRCULATION 7.97E-3 RCI-RESTART RESTART OF RCIC IS REQUIRED 1.50E-1 RCI-TDP-FR-TRAIN RCIC PUMP FAILS TO RUN GIVEN THAT IT STARTED 3.95E-2 RCI-TDP-FS-RSTRT RCIC FAILS TO RESTART GIVEN START AND SHORT-TERM RUN 8.00E-2 RCI-TDP-FS-TRAIN RCIC PUMP FAILS TO START 6.49E-3 RCI-TDP-TM-TRAIN RCIC PUMP TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.09E-2 RCI-XHE-XL-RSTRT OPERATOR FAILS TO RECOVER RCIC FAILURE TO RESTART 2.50E-1 RCI-XHE-XL-XFER OPERATOR FAILS TO RECOVER SUCTN XFER FAILURE 2.50E-1 RCI-XHE-XO-ERROR OPERATOR FAILS TO START/CONTROL RCIC INJECTION 1.00E-3