ML14294A591
| ML14294A591 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 11/04/2014 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Chris Hunter | |
| Shared Package | |
| ML14294A557 | List: |
| References | |
| IR 2013005, LER 13-009-00 | |
| Download: ML14294A591 (11) | |
Text
Enclosure 1
Final Precursor Analysis Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Pilgrim Nuclear Power Station Loss of Offsite Power during Line Maintenance Event Date: 10/14/2013 LER: 293/13-009 IR: 50-293/13-05 CCDP = 3x10-5 Plant Type: Boiling-Water Reactor (BWR); General Electric-3 with a Mark I Containment Plant Operating Mode (Reactor Power Level): Mode 1 (100% Reactor Power)
EXECUTIVE
SUMMARY
On October 14, 2013 at 2121 hours0.0245 days <br />0.589 hours <br />0.00351 weeks <br />8.070405e-4 months <br />, with the reactor critical at 100% power and offsite power 345kV line 342 out of service for a scheduled upgrade, a loss of offsite power (LOOP) occurred due to the loss of the second 345kV line 355. This resulted in a generator full load reject and a reactor scram. The cause of line 355 loss was due to a failure of an offsite substation tower support. All control rods fully inserted, main steam isolation valves closed on the loss of power to the reactor protection system, and the emergency diesel generators (EDGs) automatically started supplying power to both 4160V safety buses.
A plant cool down commenced with reactor water level being maintained by the high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems. The offsite tower was repaired and line 355 was energized at 2023 hours0.0234 days <br />0.562 hours <br />0.00334 weeks <br />7.697515e-4 months <br /> on October 15th, approximately 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> after the LOOP initiated.
According to the risk analysis modeling assumptions used in this Accident Sequence Precursor (ASP) analysis, the most likely core damage sequence is a non-recoverable loss of offsite power and subsequent station blackout (SBO) due to postulated failures of all EDGs (including the SBO diesel generator) and the failure to restore power to a safety bus prior to battery depletion. This accident sequence accounts for approximately 44% of the conditional core damage probability (CCDP) for the event. In general, these results are consistent with at-power LOOP events previously analyzed by the ASP Program at other BWRs.
EVENT DETAILS Event Description. On October 14, 2013 at 2121 hours0.0245 days <br />0.589 hours <br />0.00351 weeks <br />8.070405e-4 months <br />, with the reactor critical at 100% power and offsite power 345kV line 342 out of service for a scheduled upgrade, a LOOP occurred due to the loss of the second 345kV line 355. The cause of line 355 loss was due to a failure of an offsite substation wooden tower support. All control rods fully inserted, main steam isolation valves closed on the loss of power to the reactor protection system, and the EDGs automatically started supplying power to both 4160V safety buses.
Following the scram, reactor water level lowered to +12 inches initiating the primary containment isolation system automatically per design. A plant cool down commenced with reactor water level being maintained in the normal post-scram band of +12 inches to +45 inches utilizing the HPCI and RCIC systems. The offsite tower was repaired and line 355 was
energized at 2023 hours0.0234 days <br />0.562 hours <br />0.00334 weeks <br />7.697515e-4 months <br /> on October 15, 2013. Additional information is provided in Reference 1 (licensee event report) and Reference 2 (inspection report).
MODELING ASSUMPTIONS Analysis Type. The Pilgrim Standardized Plant Analysis Risk (SPAR) Model Revision 8.24, created in May 2014, was used for this event analysis. This event was modeled as a switchyard-related LOOP initiating event.
Analysis Rules. The ASP program uses Significance Determination Process results for degraded conditions when available. However, the ASP Program performs independent analysis for initiating events.
Key Modeling Assumptions. The following modeling assumptions were determined to be significant to the modeling of this event analysis:
This analysis models the October 14, 2013 reactor trip at Pilgrim Nuclear Station as a switchyard-related LOOP initiating event.
The probability of switchyard-related LOOP (IE-LOOPSC) was set to 1.0; all other initiating event probabilities were set to zero.
Shutdown Transformer (SDT) Availability. The 23kV power source via the SDT was available throughout the event. Given a postulated failure of the SBO diesel generator, the SDT will automatically align to power safety buses A5 and/or A6.
To allow credit for the SDT availability, the house events HE-LOOP (House Event - Loss of Offsite Power IE Has Occurred) and HE-LOOPSC (House Event - Switchyard-Related Loss of Offsite Power IE Has Occurred) must be removed from the ACP-23KV (Shutdown Transformer Offsite Power Supply) fault tree.
Offsite Power Recovery. The key offsite power recovery times for Pilgrim that are modeled within the plant SPAR model are:
30 MinutesA LOOP and subsequent SBO combined with failures/unavailabilities to RCIC, HPCI, and reactor depressurization.
1 HourA LOOP and subsequent SBO with two or more stuck open safety relief valves (given successful RCIC or HPCI operation).
3 HoursA LOOP and subsequent SBO with operators failing to recover offsite power prior to the depletion of the switchyard batteries.
Offsite power was restored via line 335 at 2023 hours0.0234 days <br />0.562 hours <br />0.00334 weeks <br />7.697515e-4 months <br /> on October 15th (approximately 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> after the LOOP initiated). Based on the event information (line maintenance and tower damage), it was determined that offsite power could not have been restored prior to depletion of the switchyard batteries (3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />).
Therefore, basic events OEP-XHE-XL-NR30MSC (Operators Fail to Recover Offsite Power in 30 Minutes), OEP-XHE-XL-NR01HSC (Operators Fail to Recover Offsite Power in 1 Hour), and OEP-XHE-XL-NR03HSC (Operators Fail to Recover Offsite Power in 3 Hours) were set to TRUE.
Initiation of Firewater Injection. The current SPAR model has a generic screening valve of 0.3 for the human error probability (HEP) for basic event FWS-XHE-XM-ERRLT (Operators Fail to Align Firewater Injection). For this analysis, the screening value was determined to be conservative; therefore, the human failure event was reevaluated using SPAR-H (Reference 3 and Reference 4). Tables 1 and 2 provide the key qualitative information for this human failure event (HFE) and the performance shaping factor (PSF) adjustments required for the quantification of the HEP using SPAR-H.
Table 1. Qualitative evaluation of HFE for initiation of firewater injection.1 Definition The definition for this HFE is the operators failing to align a firewater pump to provide a source of low-pressure injection to the reactor given a LOOP/SBO.
Description and Event Context Given a LOOP/SBO, operators will depressurize the RCS if RCIC and HPCI fail or when the suppression pool reaches its heat capacity temperature limit. After RCS depressurization, if the other low pressure sources of injection are unavailable, operators will attempt to align the firewater system to inject via the residual heat removal (RHR) system injection loops (A or B). Only the diesel-driven firewater pump will be available during a SBO; the motor-driven pump will not have electrical power.
Operator Action Success Criteria Initiate firewater injection to the reactor pressure vessel (RPV) from one of the firewater pump via the RHR system injection loops prior to core uncovery.
Nominal Cues Decreasing RPV level (-125").
Procedural Guidance Emergency operating procedure (EOP) 1 directs the operators to restore and maintain RPV level above +12" using one or more preferred injection systems and, if necessary, alternate injection systems. When RPV level decreases to -125", EOP 1 instructs the operators to start pumps and maximize injection flow with the firewater crosstie to RHR or other alternate injection subsystems per procedure 5.3.26.
Section 2.1 of procedure 5.3.26 provides detailed instructions for aligning the firewater crosstie to RHR.
Diagnosis/Action This HFE contains sufficient diagnosis and action components.
Table 2. SPAR-H Evaluation of HFE for initiation of firewater injection.
PSF Diagnosis/
Action Multiplier Notes Time Available 1 / 1 The operators would need approximately 30 minutes to perform the action component of connecting the firewater-to-RHR spool pieces and initiate the pump. The time for diagnosis is approximately 30 minutes.2 Therefore, the available time for the diagnosis component for 30 minute recovery is assigned as Nominal Time (i.e., x1). Since sufficient time was available for the action component of the recovery, the available time for the action component for all recovery times is evaluated as Nominal (i.e., x1).
See Reference 4 for guidance on apportioning time between the diagnosis and action components of an HFE.
1 Given the failure or unavailability of the motor-driven firewater pump, the day tank for the diesel-driven firewater pump would need to be refilled during operation (approximately 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after initiation). It is believed that the HEP for basic event FWS-XHE-XM-ERRLT accounts for this action due to the additional time for operators to complete the refill of the day tank past the alignment/initiation of firewater injection.
2 The estimate of 30 minutes may be conservative for some scenarios. However, the time available PSF would likely not be changed from nominal in these cases. In addition, a further decrease in the HEP would have a negligible impact on the analysis results.
PSF Diagnosis/
Action Multiplier Notes Stress 2 / 2 The PSF for diagnosis and action stress is assigned a value of High Stress (i.e., x2) due to the postulated LOOP/SBO and failures of other systems.
Complexity 2 / 2 The PSF for diagnosis complexity is assigned a value of Moderately Complex (i.e., x2) because operators would have to deal with multiple equipment unavailabilities and the concurrent actions/multiple procedures during a postulated SBO. The PSF for action complexity is also assigned a value of Moderately Complex (i.e., x2) because actions outside the control room are required.
Procedures Experience/Training Ergonomics/HMI Fitness for Duty Work Processes 1 / 1 No event information is available to warrant a change in these PSFs (for diagnosis and action) from Nominal for these HFEs.
An HEP evaluated using SPAR-H is calculated using the following formula:
Calculated HEP = (Product of Diagnosis PSFs x 0.01) + (Product of Action PSFs x 0.001)
Therefore, basic event FWS-XHE-XM-ERRLT was set to 4x10-2 from its screening value of 0.3.
ANALYSIS RESULTS CCDP. The point estimate CCDP for this event is 2.5x10-5. 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 secondary plant systems (e.g., feed water and condensate), whichever is greater. This CCDP equivalent for Pilgrim is 2.0x10-6. Therefore, this event is a precursor.
Dominant Sequence. The dominant accident sequence is LOOP sequence 6 (CCDP
= 1.1x10-5) which contributes approximately 44% of the total internal events CCDP. The cutsets/sequences that contribute to the top 95% and/or at least 1% of the total internal events CCDP are provided in Appendix A.
The dominant sequence is shown graphically in Figure B-1 in Appendix B. The events and important component failures in LOOP sequence 6 are:
A non-recoverable switchyard-related LOOP occurs, Reactor scram succeeds, Emergency powers succeeds, Safety relief valves reclose (if opened),
RCIC/HPCI succeeds, Operators fail to initiate suppression pool cooling, Operators successfully depressurize the reactor, Low-pressure core spray is successful.
Operators fail to initiate containment spray, Operators fail to vent containment, and Late injection is unavailable.
REFERENCES
- 1. Pilgrim Nuclear Power Station, "LER 293/13-009-Loss of Offsite Power and Reactor Scram, dated December 23, 2013 (ML13364A098).
- 2. U.S. Nuclear Regulatory Commission, Pilgrim Nuclear Power Station - NRC Integrated Inspection Report 05000293/2013005 and Independent Spent Fuel Storage Installation Report 07201044/2013001, dated February 10, 2014 (ML14041A203).
- 3. Idaho National Laboratory, NUREG/CR-6883, The SPAR-H Human Reliability Analysis Method, August 2005 (ML051950061).
- 4. Idaho National Laboratory, INL/EXT-10-18533, SPAR-H Step-by-Step Guidance, May 2011 (ML112060305).
LER 293/13-009 A-1 Appendix A: Analysis Results Summary of Conditional Event Changes Event Description Cond.
Value Nominal Value FWS-XHE-XM-ERRLT OPERATORS FAIL TO ALIGN FIREWATER INJECTION 4.00E-2 3.00E-1 IE-LOOPSC LOSS OF OFFSITE POWER INITIATOR (SWITCHYARD-RELATED) 1.00E+0a 1.04E-2 OEP-XHE-XL-NR01HSC OPERATORS FAIL TO RECOVER OFFSITE POWER IN 1 HOUR (SWITCHYARD-RELATED)
TRUE 6.59E-1 OEP-XHE-XL-NR03HSC OPERATORS FAIL TO RECOVER OFFSITE POWER IN 3 HOURS (SWITCHYARD-RELATED)
TRUE 2.50E-1 OEP-XHE-XL-NR30MSC OPERATORS FAIL TO RECOVER OFFSITE POWER IN 30 MINUTES (SWITCHYARD-RELATED)
TRUE 8.63E-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 LOOPSC 06 1.10E-5 44.2%
/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, CSS, CVS, LI LOOPSC 28-04 6.53E-6 26.3%
/RPS, EPS, /SRV, /HPI-B, /DEP, /FWS-EXT,
/DCL, OPR-03H, DGR-24H LOOPSC 25 2.95E-6 11.9%
/RPS, /EPS, /SRV, HPI, DEP LOOPSC 04 1.98E-6 8.0%
/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, CSS,
/CVS, LI01 LOOPSC 28-11 1.32E-6 5.3%
/RPS, EPS, /SRV, /HPI-B, /DEP, FWS-EXT, OPR-03H, DGR-08H LOOPSC 12 3.13E-7 1.3%
/RPS, /EPS, /SRV, /HPI, SPC, DEP Total 2.48E-5 100.0%
Referenced Fault Trees Fault Tree Description CSS CONTAINMENT SPRAY CVS CONTAINMENT VENTING DEP MANUAL REACTOR DEPRESS DGR-08H OPERATORS FAIL TO RECOVER EMERGENCY DIESEL IN 8 HOURS DGR-24H OPERATORS FAIL TO RECOVER EMERGENCY DIESEL IN 24 HOURS EPS EMERGENCY POWER FWS-EXT FIREWATER INJECTION HPI HIGH PRESSURE INJECTION LI LONG-TERM LOW PRESS INJECTION LI01 PILGRIM LATE INJECTION FAULT TREE OPR-03H OPERATORS FAIL TO RECOVER OFFSITE POWER IN 3 HOURS SPC SUPPRESSION POOL COOLING
LER 293/13-009 A-2 Cut Set Report - LOOPSC 06 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 1.10E-5 100 1
1.03E-5 93.83 IE-LOOPSC,CVS-XHE-XM-VENT1,RHR-XHE-XM-ERROR1,RHR-XHE-XM-SPCERROR Cut Set Report - LOOPSC 28-04 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 6.53E-6 100 1
2.82E-6 43.14 IE-LOOPSC,ACP-CRB-CF-504604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR24H 2
2.82E-6 43.14 IE-LOOPSC,ACP-CRB-CF-505605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR24H 3
1.99E-7 3.05 IE-LOOPSC,ACP-CRB-CC-504,ACP-CRB-CC-605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR24H 4
1.99E-7 3.05 IE-LOOPSC,ACP-CRB-CC-505,ACP-CRB-CC-605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR24H 5
1.99E-7 3.05 IE-LOOPSC,ACP-CRB-CC-504,ACP-CRB-CC-604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR24H 6
1.99E-7 3.05 IE-LOOPSC,ACP-CRB-CC-505,ACP-CRB-CC-604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR24H Cut Set Report - LOOPSC 25 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 2.95E-6 100 1
7.80E-7 26.43 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-FR-P205,RCI-TDP-FR-P206 2
3.56E-7 12.04 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FR-P206 3
2.83E-7 9.60 IE-LOOPSC,DCP-BCH-CF-D11D12D14 4
2.27E-7 7.67 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-TM-P205,RCI-TDP-FR-P206 5
2.01E-7 6.80 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-FR-P205,RCI-TDP-TM-P206 6
1.28E-7 4.34 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-FR-P205,RCI-TDP-FS-P206 7
1.28E-7 4.34 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-FS-P205,RCI-TDP-FR-P206 8
9.15E-8 3.10 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-TM-P206 9
7.19E-8 2.43 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-XHE-XO-ERROR1,RCI-XHE-XO-ERROR 10 5.93E-8 2.01 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-FR-P205,RCI-RESTART,RCI-TDP-FS-P206RS,RCI-XHE-XL-RSTRT 11 5.84E-8 1.98 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FS-P206 12 3.93E-8 1.33 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-FR-P205,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 13 3.72E-8 1.26 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-TM-P205,RCI-TDP-FS-P206 14 3.30E-8 1.12 IE-LOOPSC,ADS-SRV-CF-203-3ABCD,HCI-TDP-FR-P205,RCI-TDP-FR-P206 15 3.30E-8 1.12 IE-LOOPSC,ADS-XHE-XM-MDEPR,HCI-TDP-FS-P205,RCI-TDP-TM-P206
LER 293/13-009 A-3 Cut Set Report - LOOPSC 04 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 1.98E-6 100 1
4.45E-7 22.52 IE-LOOPSC,FWS-EDP-FR-P140,SSW-MDP-CF-FS,SSW-MDP-CFG-P208BER 2
4.45E-7 22.52 IE-LOOPSC,FWS-EDP-FR-P140,SSW-MDP-CF-FS,SSW-MDP-CFG-P208ADR 3
6.37E-8 3.22 IE-LOOPSC,FWS-EDP-TM-P140,SSW-MDP-CF-FS,SSW-MDP-CFG-P208BER 4
6.37E-8 3.22 IE-LOOPSC,FWS-EDP-TM-P140,SSW-MDP-CF-FS,SSW-MDP-CFG-P208ADR 5
4.36E-8 2.20 IE-LOOPSC,FWS-EDP-FS-P140,SSW-MDP-CF-FS,SSW-MDP-CFG-P208BER 6
4.36E-8 2.20 IE-LOOPSC,FWS-EDP-FS-P140,SSW-MDP-CF-FS,SSW-MDP-CFG-P208ADR 7
3.52E-8 1.78 IE-LOOPSC,ACP-CRB-CC-605,ACP-XHE-XM-NORECBKR,FWS-EDP-FR-P140,RHR-HTX-TM-E207A 8
3.52E-8 1.78 IE-LOOPSC,ACP-CRB-CC-604,ACP-XHE-XM-NORECBKR,FWS-EDP-FR-P140,RHR-HTX-TM-E207A 9
3.48E-8 1.76 IE-LOOPSC,FWS-EDP-FR-P140,RBC-MDP-CF-STRT-ABCDEF 10 2.54E-8 1.29 IE-LOOPSC,FWS-EDP-FR-P140,RBC-MDP-CF-STRT-ABCDE 11 2.54E-8 1.29 IE-LOOPSC,FWS-EDP-FR-P140,RBC-MDP-CF-STRT-BCDEF 12 2.54E-8 1.29 IE-LOOPSC,FWS-EDP-FR-P140,RBC-MDP-CF-STRT-ABCEF 13 2.54E-8 1.29 IE-LOOPSC,FWS-EDP-FR-P140,RBC-MDP-CF-STRT-ABDEF 14 2.54E-8 1.29 IE-LOOPSC,FWS-EDP-FR-P140,RBC-MDP-CF-STRT-ABCDF 15 2.54E-8 1.29 IE-LOOPSC,FWS-EDP-FR-P140,RBC-MDP-CF-STRT-ACDEF Cut Set Report - LOOPSC 28-11 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 1.32E-6 100 1
2.83E-7 21.39 IE-LOOPSC,ACP-CRB-CF-505605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FR-P140 2
2.83E-7 21.39 IE-LOOPSC,ACP-CRB-CF-504604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FR-P140 3
2.17E-7 16.43 IE-LOOPSC,ACP-CRB-CF-504604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-XHE-XM-ERRLT 4
2.17E-7 16.43 IE-LOOPSC,ACP-CRB-CF-505605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-XHE-XM-ERRLT 5
4.05E-8 3.06 IE-LOOPSC,ACP-CRB-CF-505605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-TM-P140 6
4.05E-8 3.06 IE-LOOPSC,ACP-CRB-CF-504604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-TM-P140 7
2.77E-8 2.09 IE-LOOPSC,ACP-CRB-CF-505605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FS-P140 8
2.77E-8 2.09 IE-LOOPSC,ACP-CRB-CF-504604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FS-P140 9
2.00E-8 1.51 IE-LOOPSC,ACP-CRB-CC-505,ACP-CRB-CC-604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FR-P140 10 2.00E-8 1.51 IE-LOOPSC,ACP-CRB-CC-505,ACP-CRB-CC-605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FR-P140 11 2.00E-8 1.51 IE-LOOPSC,ACP-CRB-CC-504,ACP-CRB-CC-604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FR-P140 12 2.00E-8 1.51 IE-LOOPSC,ACP-CRB-CC-504,ACP-CRB-CC-605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-EDP-FR-P140
LER 293/13-009 A-4 CCDP Total%
Cut Set 13 1.54E-8 1.16 IE-LOOPSC,ACP-CRB-CC-505,ACP-CRB-CC-605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-XHE-XM-ERRLT 14 1.54E-8 1.16 IE-LOOPSC,ACP-CRB-CC-505,ACP-CRB-CC-604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-XHE-XM-ERRLT 15 1.54E-8 1.16 IE-LOOPSC,ACP-CRB-CC-504,ACP-CRB-CC-605,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-XHE-XM-ERRLT 16 1.54E-8 1.16 IE-LOOPSC,ACP-CRB-CC-504,ACP-CRB-CC-604,ACP-XHE-XM-NORECBKR,EPS-XHE-XL-NR08H,FWS-XHE-XM-ERRLT Cut Set Report - LOOPSC 12 Only items contributing at least 1% to the total are displayed.
CCDP Total%
Cut Set 3.12E-7 100 1
2.50E-7 80.01 IE-LOOPSC,ADS-XHE-XM-MDEPR,RHR-XHE-XM-SPCERROR 2
1.06E-8 3.39 IE-LOOPSC,ADS-SRV-CF-203-3ABCD,RHR-XHE-XM-SPCERROR 3
5.33E-9 1.71 IE-LOOPSC,ADS-XHE-XM-MDEPR,RHR-HTX-CF-E207AB 4
5.00E-9 1.60 IE-LOOPSC,ADS-XHE-XM-MDEPR,RHR-STR-CF-NLOCA 5
4.80E-9 1.53 IE-LOOPSC,ADS-XHE-XM-MDEPR,RHR-MOV-CF-34AB36AB 6
4.28E-9 1.37 IE-LOOPSC,ADS-XHE-XM-MDEPR,SSW-MDP-CF-FS,SSW-MDP-CFG-P208BER 7
4.28E-9 1.37 IE-LOOPSC,ADS-XHE-XM-MDEPR,SSW-MDP-CF-FS,SSW-MDP-CFG-P208ADR 8
3.89E-9 1.25 IE-LOOPSC,ADS-XHE-XM-MDEPR,RHR-MOV-CF-18AB 9
3.89E-9 1.25 IE-LOOPSC,ADS-XHE-XM-MDEPR,RHR-MOV-CF-16AB Referenced Events Event Description Probability ACP-CRB-CC-504 4.16KV STARTUP TRANSFORMER FEEDER CIRCUIT BKR 152-504 FAILS TO OPEN RESULTS IN LOSS OF POWER TO BUS A5 2.39E-3 ACP-CRB-CC-505 4.16KV UNIT AUXILIARY TRANSFORMER FEEDER CIRCUIT BKR 152-505 FAILS TO OPEN RESULTS IN LOSS OF POWER TO BUS A5 2.39E-3 ACP-CRB-CC-604 4.16KV STARTUP TRANSFORMER FEEDER CIRCUIT BKR 152-604 FAILS TO OPEN RESULTS IN LOSS OF POWER TO BUS A6 2.39E-3 ACP-CRB-CC-605 4.16KV UNIT AUXILIARY TRANSFORMER FEEDER CIRCUIT BKR 152-605 FAILS TO OPEN RESULTS IN LOSS OF POWER TO BUS A6 2.39E-3 ACP-CRB-CF-504604 CCF OF STARTUP TRANSFORMER FEEDER CIRCUIT BKR 152-504
& 604 TO OPEN RESULTS IN LOSS OF POWER TO BUS A5 & A6 8.08E-5 ACP-CRB-CF-505605 CCF OF UNIT AUXILIARY TRANSFORMER FEEDER CIRCUIT BKRs 152-505 & 605 TO OPEN RESULTS IN LOSS OF POWER TO BUS A5
& A6 8.08E-5 ACP-XHE-XM-NORECBKR SUT or UAT FEEDER BREAKER FAULTS TO BUS A5 or BUS A6 NOT RECOVERED 1.20E-1 ADS-SRV-CF-203-3ABCD SRVS RV-203-3A, 3B, 3C & 3D FAIL FROM COMMON CAUSE 2.12E-5 ADS-XHE-XM-MDEPR OPERATORS FAIL TO DEPRESSURIZE THE REACTOR 5.00E-4 CVS-XHE-XM-VENT1 OPERATORS FAIL TO VENT CONTAINMENT USING DIRECT TORUS VENT 1.44E-1 DCP-BCH-CF-D11D12D14 BATTERY CHARGERS FAIL FROM COMMON CAUSE 2.83E-7 EPS-XHE-XL-NR08H OPERATORS FAIL TO RECOVER EMERGENCY DIESEL IN 8 HOURS 5.60E-1
LER 293/13-009 A-5 Event Description Probability EPS-XHE-XL-NR24H OPERATORS FAIL TO RECOVER EMERGENCY DIESEL IN 24 HOURS 2.90E-1 FWS-EDP-FR-P140 ENGINE DRIVEN FIRE PUMP P-140 FAILS TO RUN 5.21E-2 FWS-EDP-FS-P140 ENGINE DRIVEN FIRE PUMP P-140 FAILS TO START 5.09E-3 FWS-EDP-TM-P140 ENGINE DRIVEN FIRE PUMP P-140 IS IN TEST OR MAINT 7.45E-3 FWS-XHE-XM-ERRLT OPERATORS FAIL TO ALIGN FIREWATER INJECTION 4.00E-2 HCI-MOV-CC-IVFRO HPCI INJECTION MOV FAILS TO REOPEN 1.50E-1 HCI-MULTIPLE-INJECT MULTIPLE HPCI INJECTIONS REQUIRED 1.50E-1 HCI-TDP-FR-P205 HPCI PUMP TRAIN P-205 FAILS TO RUN GIVEN IT STARTED 3.95E-2 HCI-TDP-FS-P205 HPCI PUMP P-205 FAILS TO START 6.49E-3 HCI-TDP-TM-P205 HPCI TRAIN P-205 IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.15E-2 HCI-XHE-XL-INJECT OPERATORS FAIL TO RECOVER HPCI INJECT MOV FAILURE TO REOPEN 8.00E-1 HCI-XHE-XO-ERROR1 OPERATORS FAIL TO START/CONTROL HPCI INJECTION 1.44E-1 IE-LOOPSC LOSS OF OFFSITE POWER INITIATOR (SWITCHYARD-CENTERED) 1.00E+0 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-P206 RCIC PUMP P-206 FAILS TO RUN GIVEN THAT IT STARTED 3.95E-2 RCI-TDP-FS-P206 RCIC PUMP P-206 FAILS TO START 6.49E-3 RCI-TDP-FS-P206RS RCIC FAILS TO RESTART GIVEN START AND SHORT-TERM RUN 8.00E-2 RCI-TDP-TM-P206 RCIC PUMP TRAIN P-206 IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.02E-2 RCI-XHE-XL-RSTRT OPERATORS FAIL TO RECOVER RCIC FAILURE TO RESTART 2.50E-1 RCI-XHE-XL-XFER OPERATORS FAIL TO RECOVER SUCTN XFER FAILURE 2.50E-1 RCI-XHE-XO-ERROR OPERATORS FAIL TO START/CONTROL RCIC INJECTION 1.00E-3 RHR-HTX-CF-E207AB RHR HEAT EXCHANGERS FAIL FROM COMMON CAUSE 1.07E-5 RHR-HTX-TM-E207A RHR HEAT EXCHANGER E-207A UNAVAILABLE DUE TO TEST OR MAINTENANCE 2.36E-3 RHR-MOV-CF-16AB RHR HTX BYPASS VALVES 16A,B FAIL FROM COMMON CAUSE 7.78E-6 RHR-MOV-CF-18AB RHR MINFLOW VALVES 18 A, B FAIL TO CLOSE FOR ENHANCED COOLING 7.78E-6 RHR-MOV-CF-34AB36AB SPC INJECTION VALVES FAIL BY COMMON CAUSE 9.59E-6 RHR-STR-CF-NLOCA SUPPRESSION POOL STRAINERS FAIL FROM COMMON CAUSE (NON-LOCA) 1.00E-5 RHR-XHE-XM-ERROR1 OPERATORS FAIL TO START/CONTROL CONTAINMENT SPRAY COOLING MODE OF RHR 1.43E-1 RHR-XHE-XM-SPCERROR OPERATORS FAIL TO START/CONTROL SUPPRESSION POOL COOLING MODE OF RHR 5.00E-4 SSW-MDP-CF-FS COMMON CAUSE FAILURE TO START OF THREE SSW PUMPS 1.71E-5 SSW-MDP-CFG-P208ADR SSW PUMP P-208A & D RUNNING 5.00E-1 SSW-MDP-CFG-P208BER SSW PUMP P-208B & E RUNNING 5.00E-1
LER 293/13-009 B-1 Appendix B: Key Event Tree Figure B-1. Pilgrim Nuclear Power Station Switchyard-Related LOOP event tree.
IE-LOOPSC LOSS OF OFFSITE POWER INITIATOR (SWITCHYARD-CENTERED)
RPS REACTOR SHUTDOWN FTF-SBO EPS EMERGENCY POWER SRV TWO OR MORE STUCK OPEN SRVs HPI HIGH PRESSURE INJECTION SPC SUPPRESSION POOL COOLING DEP MANUAL REACTOR DEPRESS LPI LOW PRESS COOLANT INJECTION (LCS or LPCI)
VA ALTERNATE INJECTION SPC SUPPRESSION POOL COOLING CSS CONTAINMENT SPRAY CVS CONTAINMENT VENTING LI LONG-TERM LOW PRESS INJECTION End State (Phase - CD) 1 OK 2
OK 3
OK LI01 4
CD 5
OK 6
CD 7
OK 8
OK 9
OK 10 CD 11 CD 12 CD 13 OK 14 OK 15 OK LI01 16 CD 17 OK 18 CD 19 OK 20 OK 21 OK 22 OK 23 CD 24 CD 25 CD P1 26 LOOP-1 P2 27 LOOP-2 28 SBO-CHRIS-2 29 ATWS