ML16347A325
| ML16347A325 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 12/06/2016 |
| From: | Christopher Hunter Office of Nuclear Regulatory Research |
| To: | |
| David Aird 301-415-0634 | |
| References | |
| Download: ML16347A325 (11) | |
Text
Final ASP Program Analysis - Reject Accident Sequence Precursor Program - Office of Nuclear Regulatory Research South Texas Project, Unit 1 Manual Reactor Trip and Valid Auxiliary Feedwater System Actuation Event Date: 12/21/2015 LER: 498-2015-001 IR(s): 05000498/2015004 and 05000498/2016002 CCDP = 1x10-6 Plant Type: Westinghouse 4-Loop PWR with a Large Dry Containment Plant Operating Mode (Reactor Power Level): Mode 1 (48 Percent Reactor Power)
Analyst:
David Aird Reviewer:
Chris Hunter Contributors:
N/A BC Approved Date:
12/6/2016 EVENT DETAILS Event Description. On December 21, 2015, South Texas Project (STP) Unit 1 was at 48 percent power and power ascension was in progress following a refueling outage. At approximately 2:50 p.m., the main turbine governor valve 2 began to oscillate open and closed, resulting in large load swings and steam dump actuation. Operators began to reduce turbine load in order to stabilize main turbine governor valve 2, but the oscillations continued. In response to the oscillations, the group 1 steam dumps modulated open to divert the main steam to the condenser. At 3:08 p.m. and 3:10 p.m., the group 2 steam dumps modulated open and closed because the group 1 steam dumps did not open due to a failure of the valve positioners.
The group 1 steam dumps had lost the ability to modulate.
At 3:19 p.m., the shift manager directed a manual trip of the main turbine. With reactor power less than 50 percent, as expected, the reactor did not automatically trip when the turbine tripped. When the main turbine trip signal was received, the steam dump valve positioners were bypassed as designed and the group 1, 2, and 3 steam dumps momentarily opened. Following the turbine trip, the steam dumps returned to a modulation mode of operation. The main turbine governor valve 2 continued to oscillate and the group 1 steam dumps again failed to operate to divert the main steam to the condenser following the turbine load reject.
Main feedwater continued to fill the steam generators to the main feedwater isolation setpoint of 87.5 percent. This level increase was due to the failure of the group 1 steam dumps to modulate in response to the main turbine load changes, which resulted in a significant difference between steam flow and feedwater flow. Operators attempted to manually reduce feedwater flow but were not able to prevent the main feedwater isolation signal.
At 3:29 p.m., all four steam generator (SG) power-operated relief valves lifted, as designed, in response to the rise in steam pressure. SG levels lowered, and with no ability to feed the SGs to maintain levels, the shift manager ordered a manual reactor trip at 3:33 p.m. All control rods fully inserted into the reactor and all safety-related systems functioned as designed, with the exception of SG A blowdown containment isolation valve that failed to isolate on the main feedwater isolation. Approximately 6 seconds following the reactor trip, an auxiliary feedwater (AFW) system actuation occurred due to a SG low-level signal; all four AFW pumps actuated.
LER 498-2015-001 2
Additional information regarding the event is available in licensee event report (LER) 498-2015-001 (Ref. 1).
Cause. The total steam dump load reduction capability is 40 percent of full power. Along with 10 percent load reduction capability provided by control rods, this allows a 50 percent load reduction to occur without a reactor trip. The group 1 steam dumps make up one-fourth of the steam dumps for Unit 1, so the inability of the group 1 steam dumps to modulate translates to a loss of approximately 10 percent load reduction capability. This condition, combined with concerns regarding SG level, resulted in operators manually tripping the reactor.
The cause of the main turbine governor valve 2 oscillations was an intermittent ground on the signal wire to the linear variable differential transmitter. The aggressive fluctuations in steam flow due to the main turbine governor valve 2 oscillations caused the spring clips in the group 1 steam dumps to become dislodged, causing the valves to be unresponsive to modulation demands. The function of the spring clips is to provide air balance in the positioner required to modulate the valve to a controlled position. With the spring clips dislodged, the steam dumps could not modulate open. However, the steam dumps did maintain the ability to fully open, which they successfully did following the turbine trip.
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 In inspection report (IR) 05000498/2015004 (Ref. 2), inspectors reviewed the event as part of the baseline inspection process. The resident inspector observed all major evolutions and the operating crews performance, reviewed the licensees initial investigation and equipment repair prior to starting up the reactor. No findings were identified; however, the LER is not closed.
In IR 05000498/2016002 (Ref. 3), inspectors identified a Green finding for a violation of Technical Specifications (TS) that occurred during the power ascension prior to turbine governor valve oscillations and manual trip. The operators failed to control SG water levels at low power due to an inadequate procedure. The resulting transient caused the licensee to make two unplanned TS action statement entries: 3.1.1.4 for minimum temperature for criticality (561°F) and 3.2.5 for departure from nucleate boiling related to reactor coolant system pressure. The operators halted the power ascension and responded to the transient using approved procedures and stabilized reactor power at 14 percent. This finding is related to the event, but was not a contributing cause of the manual trip.
An independent ASP analysis is required because the manual reactor trip and AFW system actuation was an initiating event. Since no performance deficiencies related to the main turbine governor valve 2 oscillations or manual reactor trip have been identified, this event has not been analyzed under the SDP.
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 498-2015-001 3
Analysis Type. An initiating event analysis was performed using the STP Standardized Plant Analysis Risk (SPAR) model Revision 8.17, created in May 2014.
SPAR Model Modifications. No SPAR model modifications were required as part of this analysis.
Key Modeling Assumptions. The following assumptions were determined to be significant to the modeling of this event:
This analysis models the December 21, 2015, reactor trip at STP as a loss of main feedwater initiating event.
o The probability of loss of main feedwater (IE-LOMFW) was set to 1.0; all other initiating event probabilities were set to zero.2 All safety systems functioned as designed.
ANALYSIS RESULTS CCDP/Rejection Basis. The point estimate CCDP for this event is 1.5x10-6. 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 feedwater and the condenser heat sink, whichever is greater. This CCDP equivalent for STP is 1.5x10-6. Therefore, this event is not a precursor and is screened out of the ASP Program.
Dominant Sequence. The dominant accident sequence is LOMFW Sequence 02-02-09 (CCDP = 5.4x10-7) that contributes approximately 36% of the total internal events CCDP.
Figure 1, Figure 2, and Figure 3 in Appendix B illustrate this sequence. The cut sets/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 important component/system failures in LOMFW Sequence 02-02-09 are:
Loss of main feedwater initiating event occurs, Reactor trip is successful, Power-operated relief valves close, Reactor coolant pumps trip, Rapid secondary depressurization is successful, Reactor coolant pump stage 1 seal integrity is maintained, Reactor coolant pump stage 2 seals fail resulting in a small loss of coolant accident, and High-pressure injection fails resulting in a core damage state.
REFERENCES
- 1. STP Nuclear Operating Company, "South Texas Project - Unit 1, Licensee Event Report 2015-001, Manual Reactor Trip due to Lowering Steam Generator Levels and Valid Auxiliary Feedwater System Actuation Following a Manual Main Turbine Trip, dated February 18, 2016 (ML16067A086).
2 The use of this initiating event is potentially conservative because main feedwater is considered lost and unrecoverable. Therefore, the results of this analysis are bounding.
LER 498-2015-001 4
- 2. U.S. Nuclear Regulatory Commission, South Texas Project Electric Generating Station -
NRC Integrated Inspection Report 05000498/2015004; and 05000499/2015004, dated February 11, 2016 (ML16042A550).
- 3. U.S. Nuclear Regulatory Commission, South Texas Project Electric Generating Station -
NRC Integrated Inspection Report 05000498/2016002; and 05000499/2016002, dated August 11, 2016 (ML16224B123).
LER 498-2015-001 A-1 Appendix A: SAPHIRE 8 Worksheet Summary of Conditional Event Changes Event Description Cond Value Nominal Value IE-LOMFW LOSS OF MAIN FEEDWATER 1.00E+0a 6.89E-2
- 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 LOMFW 02-02-09 5.39E-7 36.0%
/RPS, /AFW, /PORV, LOSC, /RCPT, /RSD, /BP1, BP2, /SG-PORVS, HPI LOMFW 27 4.61E-7 30.7%
/RPS, AFW, MFW, FAB LOMFW 28-22 2.75E-7 18.3%
RPS, RCSPRESS LOMFW 28-20 1.04E-7 7.0%
RPS, /RCSPRESS, MFW, /AFW-ATWS, BORATION LOMFW 02-02-05 7.05E-8 4.7%
/RPS, /AFW, /PORV, LOSC, /RCPT, /RSD, /BP1, BP2, /SG-PORVS, /HPI, /SSC, RHR, LPR, CFC LOMFW 02-03-09 2.22E-8 1.5%
/RPS, /AFW, /PORV, LOSC, /RCPT, /RSD, BP1,
/BP2, /SG-PORVS, HPI Total 1.50E-6 100.0%
Referenced Fault Trees Fault Tree Description AFW AUXILIARY FEEDWATER BORATION EMERGENCY BORATION BP1 RCP SEAL STAGE 1 INTEGRITY BP2 RCP SEAL STAGE 2 INTEGRITY CFC CONTAINMENT FAN COOLERS FAB FEED AND BLEED HPI HIGH PRESSURE INJECTION LOSC RCP SEAL COOLING MAINTAINED LPR LOW PRESSURE RECIRC MFW MAIN FEEDWATER RCSPRESS RCS PRESSURE LIMITED RHR RESIDUAL HEAT REMOVAL RPS REACTOR TRIP Cut Set Report - LOMFW 02-02-09 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 5.39E-7 100 Displaying 2207 Cut Sets. (2207 Original) 1 8.24E-8 15.27 IE-LOMFW,EPS-DGN-CF-RUN,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 2
1.84E-8 3.42 IE-LOMFW,EPS-FAN-CF-FRFNS,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 3
1.60E-8 2.96 IE-LOMFW,EPS-DGN-FR-DG11,EPS-DGN-FR-DG12,EPS-DGN-FR-DG13,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 4
1.05E-8 1.95 IE-LOMFW,EPS-CRB-CF-E1ABC1,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 5
7.73E-9 1.43 IE-LOMFW,CVC-XHE-XM-SEALS,NHV-FAN-CF-FRRET,RCS-MDP-LK-BP2 6
7.73E-9 1.43 IE-LOMFW,CVC-XHE-XM-SEALS,NHV-FAN-CF-FRSUP,RCS-MDP-LK-BP2 7
7.59E-9 1.41 IE-LOMFW,EPS-DGN-FR-DG12,EPS-DGN-FR-DG13,EPS-DGN-TM-DG11,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 8
7.59E-9 1.41 IE-LOMFW,EPS-DGN-FR-DG11,EPS-DGN-FR-DG12,EPS-DGN-TM-DG13,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 9
7.59E-9 1.41 IE-LOMFW,EPS-DGN-FR-DG11,EPS-DGN-FR-DG13,EPS-DGN-TM-DG12,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2
LER 498-2015-001 A-2 CCDP Total%
Cut Set 10 6.60E-9 1.22 IE-LOMFW,EPS-DGN-CF-START,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 Cut Set Report - LOMFW 27 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 4.61E-7 100 Displaying 763 Cut Sets. (763 Original) 1 7.66E-8 16.63 IE-LOMFW,AFW-TDP-FR-P14,NHV-FAN-CF-FRSUP 2
7.66E-8 16.63 IE-LOMFW,AFW-TDP-FR-P14,NHV-FAN-CF-FRRET 3
5.00E-8 10.86 IE-LOMFW,AFW-TDP-FR-P14,NHV-ACX-CF-ALL 4
2.52E-8 5.48 IE-LOMFW,AFW-TDP-FR-P14,HPI-XHE-XM-FB,HVC-FAN-CF-FRAFW,MFW-XHE-XL-REC 5
1.63E-8 3.54 IE-LOMFW,AFW-TDP-FR-P14,EPS-DGN-CF-RUN,MFW-XHE-XL-REC,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H 6
1.60E-8 3.46 IE-LOMFW,AFW-MDP-CF-START,AFW-TDP-FR-P14,HPI-XHE-XM-FB,MFW-XHE-XL-REC 7
1.25E-8 2.72 IE-LOMFW,AFW-TDP-FS-P14,NHV-FAN-CF-FRSUP 8
1.25E-8 2.72 IE-LOMFW,AFW-TDP-FS-P14,NHV-FAN-CF-FRRET 9
1.04E-8 2.26 IE-LOMFW,AFW-TDP-TM-P14,NHV-FAN-CF-FRSUP 10 1.04E-8 2.26 IE-LOMFW,AFW-TDP-TM-P14,NHV-FAN-CF-FRRET 11 8.74E-9 1.90 IE-LOMFW,AFW-TNK-FC-AFST,HPI-XHE-XM-FB,MFW-XHE-XL-REC 12 8.19E-9 1.78 IE-LOMFW,AFW-TDP-FS-P14,NHV-ACX-CF-ALL 13 6.80E-9 1.48 IE-LOMFW,AFW-TDP-TM-P14,NHV-ACX-CF-ALL 14 5.95E-9 1.29 IE-LOMFW,AFW-TDP-FR-P14,HPI-XHE-XM-FB,HVC-FAN-CF-FSAFW,MFW-XHE-XL-REC Cut Set Report - LOMFW 28-22 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 2.75E-7 100 Displaying 61 Cut Sets. (61 Original) 1 2.46E-8 8.97 IE-LOMFW,PPR-MOV-FC-RC001A,RPS-BME-CF-RTBAB 2
2.46E-8 8.97 IE-LOMFW,PPR-MOV-FC-RC001B,RPS-BME-CF-RTBAB 3
2.06E-8 7.48 IE-LOMFW,PPR-MOV-FC-RC001A,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 4
2.06E-8 7.48 IE-LOMFW,PPR-MOV-FC-RC001B,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 5
2.03E-8 7.38 IE-LOMFW,RCS-PHN-MODPOOR,RCS-PHN-PL,RPS-BME-CF-RTBAB 6
1.85E-8 6.74 IE-LOMFW,PPR-MOV-FC-RC001A,RPS-ROD-CF-RCCAS 7
1.85E-8 6.74 IE-LOMFW,PPR-MOV-FC-RC001B,RPS-ROD-CF-RCCAS 8
1.69E-8 6.16 IE-LOMFW,RCS-PHN-MODPOOR,RCS-PHN-PL,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 9
1.52E-8 5.55 IE-LOMFW,RCS-PHN-MODPOOR,RCS-PHN-PL,RPS-ROD-CF-RCCAS 10 1.39E-8 5.07 IE-LOMFW,PPR-MOV-FC-RC001A,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 11 1.39E-8 5.07 IE-LOMFW,PPR-MOV-FC-RC001B,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 12 1.15E-8 4.18 IE-LOMFW,RCS-PHN-MODPOOR,RCS-PHN-PL,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 13 5.70E-9 2.07 IE-LOMFW,PPR-SRV-CC-PCV656,RPS-BME-CF-RTBAB 14 5.70E-9 2.07 IE-LOMFW,PPR-SRV-CC-PCV655,RPS-BME-CF-RTBAB 15 4.76E-9 1.73 IE-LOMFW,PPR-SRV-CC-PCV655,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 16 4.76E-9 1.73 IE-LOMFW,PPR-SRV-CC-PCV656,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 17 4.28E-9 1.56 IE-LOMFW,PPR-SRV-CC-PCV656,RPS-ROD-CF-RCCAS 18 4.28E-9 1.56 IE-LOMFW,PPR-SRV-CC-PCV655,RPS-ROD-CF-RCCAS 19 3.22E-9 1.17 IE-LOMFW,PPR-SRV-CC-PCV655,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL
LER 498-2015-001 A-3 CCDP Total%
Cut Set 20 3.22E-9 1.17 IE-LOMFW,PPR-SRV-CC-PCV656,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL Cut Set Report - LOMFW 28-20 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 1.04E-7 100 Displaying 16 Cut Sets. (16 Original) 1 3.22E-8 30.83 IE-LOMFW,CVC-XHE-XM-BOR,RPS-BME-CF-RTBAB 2
2.69E-8 25.72 IE-LOMFW,CVC-XHE-XM-BOR,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 3
2.42E-8 23.17 IE-LOMFW,CVC-XHE-XM-BOR,RPS-ROD-CF-RCCAS 4
1.82E-8 17.43 IE-LOMFW,CVC-XHE-XM-BOR,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 5
2.08E-9 1.99 IE-LOMFW,CVC-XHE-XM-BOR,RPS-UVL-CF-UVDAB,RPS-XHE-XE-SIGNL Cut Set Report - LOMFW 02-02-05 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 7.05E-8 100 Displaying 327 Cut Sets. (327 Original) 1 2.17E-8 30.80 IE-LOMFW,CVC-XHE-XM-SEALS,ECW-FAN-CF-FRFNS,RCS-MDP-LK-BP2 2
1.13E-8 16.05 IE-LOMFW,CVC-XHE-XM-SEALS,ECW-PND-CF-989456,RCS-MDP-LK-BP2 3
4.21E-9 5.97 IE-LOMFW,CVC-MDP-TM-PDP,ECW-FAN-CF-FRFNS,RCS-MDP-LK-BP2 4
2.21E-9 3.14 IE-LOMFW,CVC-XHE-XM-SEALS,ECW-FAN-CF-FSFNS,RCS-MDP-LK-BP2 5
2.19E-9 3.11 IE-LOMFW,CVC-MDP-TM-PDP,ECW-PND-CF-989456,RCS-MDP-LK-BP2 6
1.75E-9 2.48 IE-LOMFW,CCW-TNK-FC-SURGE,CVC-XHE-XM-SEALS,RCS-MDP-LK-BP2 7
1.09E-9 1.54 IE-LOMFW,CVC-XHE-XR-PDP,ECW-FAN-CF-FRFNS,RCS-MDP-LK-BP2 8
1.03E-9 1.46 IE-LOMFW,CVC-MDP-FS-PDP,ECW-FAN-CF-FRFNS,RCS-MDP-LK-BP2 9
8.94E-10 1.27 IE-LOMFW,CCW-1A1CRUN-1BSTBY,CCW-MDP-CF-RUN,CVC-XHE-XM-SEALS,RCS-MDP-LK-BP2 10 8.94E-10 1.27 IE-LOMFW,CCW-1B1CRUN-1ASTBY,CCW-MDP-CF-RUN,CVC-XHE-XM-SEALS,RCS-MDP-LK-BP2 11 8.94E-10 1.27 IE-LOMFW,CCW-1A1BRUN-1CSTBY,CCW-MDP-CF-RUN,CVC-XHE-XM-SEALS,RCS-MDP-LK-BP2 12 8.94E-10 1.27 IE-LOMFW,CVC-XHE-XM-SEALS,ECW-1B1CRUN-1ASTBY,ECW-MDP-CF-RUN,RCS-MDP-LK-BP2 13 8.94E-10 1.27 IE-LOMFW,CVC-XHE-XM-SEALS,ECW-1A1CRUN-1BSTBY,ECW-MDP-CF-RUN,RCS-MDP-LK-BP2 14 8.94E-10 1.27 IE-LOMFW,CVC-XHE-XM-SEALS,ECW-1A1BRUN-1CSTBY,ECW-MDP-CF-RUN,RCS-MDP-LK-BP2 15 8.44E-10 1.20 IE-LOMFW,CCW-1B1CRUN-1ASTBY,CCW-MDP-TM-P1A,EPS-DGN-FR-DG12,EPS-DGN-FR-DG13,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 16 8.44E-10 1.20 IE-LOMFW,CCW-1A1BRUN-1CSTBY,CCW-MDP-TM-P1C,EPS-DGN-FR-DG11,EPS-DGN-FR-DG12,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 17 8.44E-10 1.20 IE-LOMFW,CCW-1A1CRUN-1BSTBY,CCW-MDP-TM-P1B,EPS-DGN-FR-DG11,EPS-DGN-FR-DG13,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP2 Cut Set Report - LOMFW 02-03-09 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 2.22E-8 100 Displaying 215 Cut Sets. (215 Original) 1 4.12E-9 18.52 IE-LOMFW,EPS-DGN-CF-RUN,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 2
9.21E-10 4.15 IE-LOMFW,EPS-FAN-CF-FRFNS,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 3
7.99E-10 3.60 IE-LOMFW,EPS-DGN-FR-DG11,EPS-DGN-FR-DG12,EPS-DGN-FR-DG13,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 4
5.25E-10 2.36 IE-LOMFW,EPS-CRB-CF-E1ABC1,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2
LER 498-2015-001 A-4 CCDP Total%
Cut Set 5
3.86E-10 1.74 IE-LOMFW,CVC-XHE-XM-SEALS,NHV-FAN-CF-FRRET,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 6
3.86E-10 1.74 IE-LOMFW,CVC-XHE-XM-SEALS,NHV-FAN-CF-FRSUP,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 7
3.79E-10 1.71 IE-LOMFW,EPS-DGN-FR-DG11,EPS-DGN-FR-DG12,EPS-DGN-TM-DG13,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 8
3.79E-10 1.71 IE-LOMFW,EPS-DGN-FR-DG11,EPS-DGN-FR-DG13,EPS-DGN-TM-DG12,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 9
3.79E-10 1.71 IE-LOMFW,EPS-DGN-FR-DG12,EPS-DGN-FR-DG13,EPS-DGN-TM-DG11,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 10 3.30E-10 1.48 IE-LOMFW,EPS-DGN-CF-START,OEP-VCF-LP-CLOOP,OEP-XHE-XL-NR01H,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 11 2.52E-10 1.13 IE-LOMFW,CVC-XHE-XM-SEALS,NHV-ACX-CF-ALL,RCS-MDP-LK-BP1,/RCS-MDP-LK-BP2 Referenced Events Event Description Probability
/RPS-CCP-TM-CHA CH-A IN T&M 1.00E+0 AFW-MDP-CF-START CCF OF AFW MDPS TO START 2.01E-5 AFW-TDP-FR-P14 TURBINE DRIVEN FEED PUMP P14 FAILS TO RUN 3.97E-2 AFW-TDP-FS-P14 TURBINE DRIVEN FEED PUMP P14 FAILS TO START 6.49E-3 AFW-TDP-TM-P14 FEED PUMP P14 IS IN TEST OR MAINTENANCE 5.39E-3 AFW-TNK-FC-AFST AFST OR PUMP SUCTION PATH IS UNAVAILABLE 4.37E-7 CCW-1A1BRUN-1CSTBY CCW MDP 1A RUNNING CCW MDP 1B RUNNING CCW MDP 1C STANDBY 3.33E-1 CCW-1A1CRUN-1BSTBY CCW MDP 1A RUNNING CCW MDP 1C RUNNING CCW MDP 1B STANDBY 3.33E-1 CCW-1B1CRUN-1ASTBY CCW MDP 1B RUNNING CCW MDP 1C RUNNING CCW MDP 1A STANDBY 3.33E-1 CCW-MDP-CF-RUN CCW PUMPS FAIL FROM COMMON CAUSE TO RUN 6.71E-7 CCW-MDP-TM-P1A CCW MDP P1A UNAVAILABLE DUE TO TEST OR MAINTENANCE 4.79E-3 CCW-MDP-TM-P1B CCW MDP P1B UNAVAILABLE DUE TO TEST OR MAINTENANCE 4.79E-3 CCW-MDP-TM-P1C CCW MDP P1C UNAVAILABLE DUE TO TEST OR MAINTENANCE 4.79E-3 CCW-TNK-FC-SURGE CCW SURGE TANK IS UNAVAILABLE 4.37E-7 CVC-MDP-FS-PDP PDP FAILS TO START 9.47E-4 CVC-MDP-TM-PDP PDP IS IN TEST OR MAINTENANCE 3.88E-3 CVC-XHE-XM-BOR OPERATOR FAILS TO INITIATE EMERGENCY BORATION 2.00E-2 CVC-XHE-XM-SEALS OPERATOR FAILS TO RESTORE RCP SEAL COOLING USING THE PDP 2.00E-2 CVC-XHE-XR-PDP OPERATOR FAILS TO RESTORE PDP AFTER TEST OR MAINT 1.00E-3 ECW-1A1BRUN-1CSTBY ECW MDP 1A RUNNING ECW MDP 1B RUNNING ECW MDP 1C STANDBY 3.33E-1 ECW-1A1CRUN-1BSTBY ECW MDP 1A RUNNING ECW MDP 1C RUNNING ECW MDP 1B STANDBY 3.33E-1 ECW-1B1CRUN-1ASTBY ECW MDP 1B RUNNING ECW MDP 1C RUNNING ECW MDP 1A STANDBY 3.33E-1 ECW-FAN-CF-FRFNS CCF OF ECW VENT FANS 01 - 06 TO RUN 5.43E-6 ECW-FAN-CF-FSFNS CCF OF ECW VENT FANS 01 - 06 TO START 5.54E-7 ECW-MDP-CF-RUN PUMPS FAIL FROM COMMON CAUSE TO RUN 6.71E-7 ECW-PND-CF-989456 CCF OF INTAKE DAMPERS (EWDAO9894/95/96) 2.83E-6 EPS-CRB-CF-E1ABC1 CCF OF 4160V CRBS (E1A1/E1B1/E1C1) TO OPEN 1.81E-5 EPS-DGN-CF-RUN COMMON CAUSE FAILURE OF DIESEL GENERATORS TO RUN 1.42E-4 EPS-DGN-CF-START COMMON CAUSE FAILURE OF DIESEL GENERATORS TO START 1.14E-5 EPS-DGN-FR-DG11 DIESEL GENERATOR 11 FAILS TO RUN 3.02E-2 EPS-DGN-FR-DG12 DIESEL GENERATOR 12 FAILS TO RUN 3.02E-2 EPS-DGN-FR-DG13 DIESEL GENERATOR 13 FAILS TO RUN 3.02E-2 EPS-DGN-TM-DG11 DG 11 UNAVAILABLE DUE TO TEST AND MAINTENANCE 1.43E-2 EPS-DGN-TM-DG12 DG 11 UNAVAILABLE DUE TO TEST AND MAINTENANCE 1.43E-2 EPS-DGN-TM-DG13 DG 13 UNAVAILABLE DUE TO TEST AND MAINTENANCE 1.43E-2
LER 498-2015-001 A-5 Event Description Probability EPS-FAN-CF-FRFNS CCF OF DG ROOM FANS F001/F002/F003 TO RUN 3.18E-5 HPI-XHE-XM-FB OPERATOR FAILS TO INITIATE FEED AND BLEED COOLING 2.00E-2 HVC-FAN-CF-FRAFW CCF OF AFW ROOM FANS 001/002/003 TO RUN 3.18E-5 HVC-FAN-CF-FSAFW CCF OF AFW ROOM FANS 001/002/003 TO START 7.50E-6 IE-LOMFW LOSS OF MAIN FEEDWATER 1.00E+0 MFW-XHE-XL-REC OPERATOR FAILS TO RECOVER MFW (LOMFW INITIATOR) 1.00E+0 NHV-ACX-CF-ALL AIR COOLING UNITS FAIL FROM COMMON CAUSE 1.26E-6 NHV-FAN-CF-FRRET CCF OF RETURN FANS 001/002/003 TO RUN 1.93E-6 NHV-FAN-CF-FRSUP CCF OF SUPPLY FANS 014/015/016 TO RUN 1.93E-6 OEP-VCF-LP-CLOOP CONSEQUENTIAL LOOP GIVEN REACTOR TRIP 5.30E-3 OEP-XHE-XL-NR01H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 5.46E-1 PPR-MOV-FC-RC001A PORV PCV-655 BLOCK VALVE DC-001A CLOSED DURING POWER 1.53E-2 PPR-MOV-FC-RC001B PORV PCV-656 BLOCK VALVE RC-001B CLOSED DURING POWER 1.53E-2 PPR-SRV-CC-PCV655 PORV PCV-655 FAILS TO OPEN ON DEMAND 3.54E-3 PPR-SRV-CC-PCV656 PORV PCV-656 FAILS TO OPEN ON DEMAND 3.54E-3 RCS-MDP-LK-BP1 RCP SEAL STAGE 1 INTEGRITY (BINDING/POPPING OPEN) FAILS 1.25E-2 RCS-MDP-LK-BP2 RCP SEAL STAGE 2 INTEGRITY (BINDING/POPPING OPEN) FAILS 2.00E-1 RCS-PHN-MODPOOR MODERATOR TEMP COEFFICIENT NOT ENOUGH NEGATIVE 1.40E-2 RCS-PHN-PL POWER AT HIGH LEVEL 9.00E-1 RPS-BME-CF-RTBAB CCF OF RTB-A AND RTB-B (MECHANICAL) 1.61E-6 RPS-CBI-CF-6OF8 CCF 6 BISTABLES IN 3 OF 4 CHANNELS 2.70E-6 RPS-CCX-CF-6OF8 CCF 6 ANALOG PROCESS LOGIC MODULES IN 3 OF 4 CHANNELS 1.83E-6 RPS-ROD-CF-RCCAS CCF 10 OR MORE RCCAS FAIL TO DROP 1.21E-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 PRESENT 5.00E-1 RPS-XHE-XE-SIGNL OPERATOR FAILS TO RESPOND WITH RPS SIGNAL PRESENT 1.00E-2
LER 498-2015-001 B-1 Appendix B: Key Event Trees Figure 1: Loss of Main Feedwater Event Tree
LER 498-2015-001 B-2 Figure 2: Loss of Seal Cooling Event Tree Figure 3: Small Loss of Coolant Accident Event Tree