ML20112H840
| ML20112H840 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 05/12/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Hunter C (301) 415-1394 | |
| References | |
| LER 341-01-001 | |
| Download: ML20112H840 (13) | |
Text
1
)LQDOPrecursor Analysis Accident Sequence Precursor Program --- Office of Nuclear Regulatory Research April 30, 2004 Fermi 2 Emergency Diesel Generator 14 Inoperable for Greater Than the Technical Specification Allowed 7 Days (YHQW'DWH 03/28/0
/(5 341/01-00
&'3 3x10-6 Condition Summary On March 21, 2001, a 24-hour endurance surveillance test run on emergency diesel generator (EDG) 14 was started. At about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> into the run, the EDG 14 outboard bearing temperature was 228F and rising. The EDG was manually tripped, but about 1 minute later there was a fire on the generator outboard bearing housing. The bearing had catastrophically failed due to a lack of lubrication in the bearing housing. The licensee determined that the EDG 14 oil sight glass and level mark were positioned too low. The diesel was subsequently repaired, tested, and returned to service on March 31, 2001 (References 1, 2, 3, and 4).
Cause. The root cause of this event was lower-than-adequate oil level in the bearing housing.
Two causes led to this event. First, in 1984, during plant construction, a stiffener bar was installed on the EDG 14 end-bell to reduce axial vibrations. This caused improper sight glass piping lengths and the incorrect lowering of the sight glass to show 7/8 inch higher than actual level. Second, in 1997, an NRC maintenance inspection team opened an unresolved item on the EDG bearing level indicators. A technical service request (TSR) was issued to resolve the item. From the TSR, a minor maintenance work request was issued to install green bands on all EDGs. On or about March 3, 1999, a contract system engineer, responsible for installing the bands, failed to follow the TSR and marked the green band too low on EDG 14. The other three diesels were unaffected.
Condition duration. The condition has existed since at least March 3, 1999. The last successful 24-hour endurance test was completed on October 22, 1999. The time from the last successful test until the EDG failed its next 24-hour endurance test is about 17 months (October 22, 1999, to March 21, 2001). The EDG successfully completed a number of short runs during the 17-month period and had run about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> prior to its failure on March 21, 2001. Because there is uncertainty about when the failure cause actually rendered the EDG unable to perform its design function, the time for Part 1 of the condition assessment is taken as one-half of the 17-month interval, or 8.5 months (6185 hours0.0716 days <br />1.718 hours <br />0.0102 weeks <br />0.00235 months <br />). EDG 14 was also inoperable from the time of its failed test on March 21, 2001, until it was subsequently repaired and returned to service on March 31, 2001. The time for Part 2 of the condition assessment is 10 days (240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />).
Recovery opportunities. No recovery opportunity is believed to exist for EDG 14 for this event. The failure of the outboard bearing required about 10 days to repair, test, and return to service. This exceeds the EDG mission times assumed in this analysis.
LER 341/01-001 1 Since this condition did not involve an actual initiating event, the parameter of interest is the measure of the incremental increase between the conditional probability for the period in which the condition existed and the nominal probability for the same period but with the condition nonexistent and plant equipment available. This incremental increase or importance is determined by subtracting the CDP from the CCDP. This measure is used to assess the risk significance of hardware unavailabilities especially for those cases where the nominal CDP is high with respect to the incremental increase of the conditional probability caused by the hardware unavailability.
2 SENSITIVE - NOT FOR PUBLIC DISCLOSURE Analysis Results
Importance1 The risk significance of the EDG being unavailable for automatic initiation is determined by subtracting the nominal core damage probability from the conditional core damage probability:
Part 1 Part 2 Conditional core damage probability (CCDP) =
9.8 x 10-6 1.0 x 10-6 Nominal core damage probability (CDP) =
7.4 x 10-6 4.2 x 10-7 Importance ( CDP = CCDP - CDP) =
2.4 x 10-6 5.8 x 10-7 Total Importance =
3.0 x 10-6 This is an increase of 3.0 x 10-6 over the nominal CDP for the 8.5-month period when the EDG was not available.
The Accident Sequence Precursor Program acceptance threshold is an importance
( CDP) of 1.0 x 10-6.
For this condition we conducted a sensitivity analysis for Part 1 related to power being supplied to various containment isolation valves early in the loss of offsite power (LOOP).
For the containment spray system, the shutdown cooling system, and the suppression pool cooling system, each fault tree had a transfer to DIV-4-AC, modeling the power supply required to open a containment isolation valve in each system. Because we are assuming in this analysis that EDG 14 would run for at least 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, these valves would have power available if they have already received the demand to open. To check the sensitivity of this analysis to this power availability, we performed a sensitivity analysis with three fault tree modifications. For fault trees CSS-B, SDC-B, and SPC-B, we deleted the transfer to DIV-4-AC. The results of this sensitivity analysis gave a CDP of 1.6 x 10-
- 6. We conclude that our original Part 1 results are conservative, but not overly so, based on this nonconservative (lower bound) sensitivity analysis.
Dominant sequences The dominant core damage sequence for this event (for both parts) is a LOOP sequence (Sequence 17). The events and important component failures in Sequence 17 (shown in Figure 1) include:
SENSITIVE - NOT FOR PUBLIC DISCLOSURE a LOOP initiating event, a successful reactor trip, successful operation of the emergency power system, the safety relief valves (SRVs) successfully reclose after opening, failure of the standby feedwater system, successful operation of the reactor core isolation cooling (RCIC) system, failure of the suppression pool cooling mode of the residual heat removal (RHR)
- system, successful manual depressurization, failure of the shutdown cooling mode of the RHR system, failure of the containment spray cooling mode of the RHR system, and failure of the containment venting system.
Results tables The conditional probability of the dominant sequences are shown in Tables 1a and 1b.
The event tree sequence logic for the dominant sequences is provided in Table 2a.
The conditional cut sets for the dominant sequences are provided in Tables 3a and 3b.
Modeling Assumptions
Assessment summary This event was modeled as an at-power condition assessment with EDG 14 unavailable for 8.5 months. Because EDG 14 had successfully completed a number of short runs and had run about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> prior to its failure on March 21, 2001, it is reasonable to assume that the EDG would successfully operate for short mission times. Therefore, this analysis was performed in two parts. The first part considered the portion of the 8.5 months (6185 hours0.0716 days <br />1.718 hours <br />0.0102 weeks <br />0.00235 months <br />) when the EDG was inoperable only for severe weather-related LOOPs lasting longer than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The second part considered the 10 days (240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />) at the end of the period when the EDG was inoperable for all types of LOOPs. Revision 3.01 of the Fermi Unit 2 standardized plant analysis risk (SPAR) model (Reference 5) was used for this assessment. The discussion below provides the bases for significant changes.
Concurrent with this condition, another condition also existed. This event was reported in LER 341/00-009 (Reference 6). Between March 4 and April 2, 2000, EDG 11 was technically inoperable due to low viscosity oil in its alternator bearings. The licensee event report (LER) states that EDG 11 would likely have operated for a period of 3 days and 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> while EDG 13 was out of service for preventive maintenance. Because the failure probability for the diesels includes maintenance/out-of-service time and because the time to failure for EDG 11 exceeds the maximum modeled mission time for EDGs of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, this additional condition was not included in the condition assessment.
Basic event probability changes Tables 4a and 4b provide the basic events that were modified to reflect the event condition being analyzed. The bases for these changes are as follows:
SENSITIVE - NOT FOR PUBLIC DISCLOSURE Frequency of loss of offsite power initiating event (IE-LOOP). In Part 1, the LOOP initiating event frequency was reduced to model only those severe weather LOOP initiating events that lasted longer than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. This was done by subtracting the contribution from plant-centered and grid-related LOOPs out. Then we applied a factor of 0.1 to account for the fact that only 10% of severe-weather related LOOPs last longer than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
Frequency of divisional LOOP initiating event (IE-LOOP-I and IE-LOOP-II). In Part 1, the divisional LOOP initiating event frequencies were reduced to remain proportional to the full LOOP initiating event frequency.
Operator fails to align the alternate DG to a dead bus (EPS-XHE-XM-ALTDG). In Part 1, the probability that the operator would fail to align the alternate DG to a dead bus was modified to account for the longer time available to complete this action. In the nominal model a performance shaping factor (PSF) of 10 is applied for Available Time. In Part 1, there is a nominal amount of time available to complete this action, so the Nominal PSF of 1.0 would apply.
Operator fails to recover ac power (ACP-XHE-NOREC-30, -90, -4H, and -BD). In Part 1, the probability that the operator would recover ac power was set to a failure probability of TRUE to reflect that the event being modeled is a severe weather LOOP lasting longer than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. This analysis conservatively assumes that failed diesel generators cannot be repaired in time to be of use in preventing core damage.
Operator fails to recover offsite power (OEP-XHE-NOREC-01H, -02H, -04H, and
-10H). In Part 1, the probability that the operator would recover offsite power was set to a failure probability of TRUE to reflect that the event being modeled is a severe weather LOOP lasting longer than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
Probability of failure of diesel generator 14 (EPS-DGN-FR-DGD). In both parts, the probability that the EDG would fail to start and run was set to a failure probability of TRUE to reflect the failure of the EDG to provide emergency power.
Model update A project rule was added to model the complete dependence between basic events EPS-XHE-XM-ALTDG and EPS-XHE-XM-CTG. The new rule is as follows:
if EPS-XHE-XM-ALTDG
- EPS-XHE-XM-CTG then DeleteEvent = EPS-XHE-XM-CTG; AddEvent = EPS-XHE-XM-CTG1; endif
SENSITIVE - NOT FOR PUBLIC DISCLOSURE References 1.
LER 341/01-001, Emergency Diesel Generator 14 Inoperable for Greater Than the Technical Specification Allowed 7 Days, March 28, 2001 (ADAMS Accession No. ML011500260).
2.
NRC Inspection Report No. 50-341/01-06, April 27, 2001 (ADAMS Accession No. ML011170320).
3.
NRC Inspection Report No. 50-341/01-09, July 25, 2001 (ADAMS Accession No. ML012070116).
4.
NRC Supplemental Inspection Report No. 50-341/01-10, August 17, 2001 (ADAMS Accession No. ML012330138).
5.
J. A. Schroeder, Standardized Plant Analysis Risk Model for Fermi 2 (ASP BWR C),
Revision 3.01, Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID, September 2003.
6.
LER 341/00-009, Emergency Diesel Generator Inoperable Due to Low Viscosity Oil in the Alternator Bearings, May 8, 2000 (ADAMS Accession No. ML003722838).
SENSITIVE - NOT FOR PUBLIC DISCLOSURE Table 1a. Conditional probabilities associated with the highest probability sequences.
(Part 1)1 Event tree name Sequence no.
Conditional core damage probability (CCDP)
Core damage probability (CDP)
Importance (CCDP - CDP)3 LOOP 17 8.6E-007 8.1E-008
XFMR65 06 6.1E-007 1.3E-007
LOOP 60-04 3.8E-007 1.5E-008 Total (all sequences)2 9.8E-006 7.4E-006 2.4E-006 Note:
- 1. (File name: GEM 341-01-001 03-29-2004 141404 Part 1.wpd)
- 2. Total CCDP includes all sequences (including those not shown in this table).
- 3. Importance is calculated using the total CCDP and total CDP from all sequences. Sequence level importance measures are not additive.
Table 1b. Conditional probabilities associated with the highest probability sequences.
(Part 2)1 Event tree name Sequence no.
Conditional core damage probability (CCDP)
Core damage probability (CDP)
Importance (CCDP - CDP)3 LOOP 17 4.2E-007 4.0E-008
LOOP 31 8.1E-008 6.2E-009
LOOP 56 5.0E-008 2.7E-009
Total (all sequences)2 1.0E-006 4.2E-007 5.8E-007 Note:
- 1. (File name: GEM 341-01-001 03-29-2004 134628 Part 2.wpd)
- 2. Total CCDP includes all sequences (including those not shown in this table).
- 3. Importance is calculated using the total CCDP and total CDP from all sequences. Sequence level importance measures are not additive.
SENSITIVE - NOT FOR PUBLIC DISCLOSURE Table 2a. Event tree sequence logic for the dominant sequences.
Event tree name Sequence no.
Logic
(/ denotes success; see Table 2b for top event names)
LOOP 17
/RPS, /EPS, /SRV, SFW, /RCI, SPC, /DEP, SDC, CSS, CVS XFMR65 06
/RPS, PCS, /SRV, /SFW, SPC, /DEP, SDC, CSS, CVS LOOP 60-04
/RPS, EPS, /SRV, /RCI, /DEP, VA3, AC-4HR Table 2b. Definitions of fault trees listed in Table 2a.
AC-4HR OPERATOR FAILS TO RECOVER AC POWER IN 4 HOURS CSS CONTAINMENT SPRAY COOLING IS UNAVAILABLE CVS CONTAINMENT (SUPPRESSION POOL) VENTING FAILS DEP MANUAL DEPRESSURIZATION FAILS EPS EMERGENCY POWER FAILS PCS POWER CONVERSION SYSTEM IS UNAVAILABLE RCI RCIC FAILS TO PROVIDE SUFFICIENT FLOW TO REACTOR RPS REACTOR SHUTDOWN FAILS SDC SHUTDOWN COOLING MODE OF RHR FAILS SFW STANDBY FEEDWATER IS UNAVAILABLE SPC SUPPRESSION POOL COOLING MODE OF RHR FAILS SRV NO SRV FAILS TO CLOSE VA3 FIREWATER INJECTION IS UNAVAILABLE
SENSITIVE - NOT FOR PUBLIC DISCLOSURE Table 3a. Conditional cut sets for Sequence 17 (Part 1).
CCDP Percent contribution Minimal cut sets1 Event Tree: LOOP, Sequence 17 9.90E-008 11.2
/SRV EPS-DGN-TM-DG12 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 9.90E-008 11.2
/SRV EPS-DGN-TM-DG11 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 8.04E-008 9.0
/SRV EPS-DGN-FS-DG11 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 8.04E-008 9.0
/SRV EPS-DGN-FS-DG12 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 5.44E-008 6.3
/SRV ESW-MDP-TM-TRNB EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 5.44E-008 6.3
/SRV ESW-MDP-TM-TRNA EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 5.20E-008 6.0
/SRV EPS-DGN-FR-DG11 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 5.20E-008 6.0
/SRV EPS-DGN-FR-DG12 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 3.09E-008 3.6
/SRV EPS-FAN-FC-2DG12 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 3.09E-008 3.6
/SRV EPS-FAN-FC-1DG11 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 3.09E-008 3.6
/SRV EPS-FAN-FC-2DG11 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 3.09E-008 3.6
/SRV EPS-FAN-FC-1DG12 EPS-XHE-XM-ALTDG EPS-XHE-XM-CTG1 7.8E-007 Total2 Notes:
1.
See Table 4a for definitions and probabilities for the basic events.
2.
Total CCDP includes all cut sets (including those not shown in this table).
SENSITIVE - NOT FOR PUBLIC DISCLOSURE Table 3b. Conditional cut sets for Sequence 17 (Part 2).
CCDP Percent contribution Minimal cut sets1 Event Tree: LOOP, Sequence 17 5.28E-008 12.5
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-ALTDG EPS-DGN-TM-DG12 5.28E-008 12.5
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-ALTDG EPS-DGN-TM-DG11 4.32E-008 10.1
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-ALTDG EPS-DGN-FS-DG12 4.32E-008 10.1
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-ALTDG EPS-DGN-FS-DG11 2.88E-008 7.1
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-ALTDG ESW-MDP-TM-TRNB 2.88E-008 7.1
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-ALTDG ESW-MDP-TM-TRNA 1.68E-008 4.0
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-ALTDG EPS-FAN-FC-2DG12 1.68E-008 4.0
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-CTG EPS-FAN-FC-1DG11 1.68E-008 4.0
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-CTG-TM-CTG EPS-FAN-FC-1DG12 1.68E-008 4.0
/SRV OEP-XHE-NOREC-10H EPS-XHE-XM-CTG1 EPS-XHE-XM-CTG EPS-FAN-FC-2DG11 3.8E-007 Total2 Notes:
1.
See Table 4b for definitions and probabilities for the basic events.
2.
Total CCDP includes all cut sets (including those not shown in this table).
LER 341/01-001 10 SENSITIVE - NOT FOR PUBLIC DISCLOSURE Table 4a. Definitions and probabilities for modified or dominant basic events (Part 1).
Event name Description Probability/
frequency Modified ACP-XHE-NOREC-30 OPERATOR FAILS TO RECOVER AC POWER IN 30 MINUTES TRUE YES1 ACP-XHE-NOREC-4H OPERATOR FAILS TO RECOVER AC POWER IN 4 HOURS TRUE YES1 ACP-XHE-NOREC-90 OPERATOR FAILS TO RECOVER AC POWER IN 90 MINUTES TRUE YES1 ACP-XHE-NOREC-BD OPERATOR FAILS TO RECOVER AC POWER BEFORE BATTERY DEPLETION TRUE YES1 EPS-CTG-FR-BLKST BLACKSTART CTG FAILS TO RUN 5.0E-002 NO EPS-CTG-FS-BLKST BLACKSTART CTG FAILS TO START 4.0E-002 NO EPS-CTG-TM-CTG CTG OUT FOR TEST & MAINTENANCE 6.0E-002 NO EPS-DGN-CF-RUN DIESEL GENERATOR FAILS FROM COMMON CAUSE TO RUN 1.9E-003 NO EPS-DGN-FR-DG11 DIESEL GENERATOR 11 FAILS TO RUN 1.7E-002 YES2 EPS-DGN-FR-DG12 DIESEL GENERATOR 12 FAILS TO RUN 1.7E-002 YES2 EPS-DGN-FR-DG13 DIESEL GENERATOR 13 FAILS TO RUN 1.7E-002 YES2 EPS-DGN-FR-DG14 DIESEL GENERATOR 14 FAILS TO RUN TRUE YES3 EPS-DGN-FS-DG11 DIESEL GENERATOR 11 FAILS TO START 2.5E-002 NO EPS-DGN-FS-DG12 DIESEL GENERATOR 12 FAILS TO START 2.5E-002 NO EPS-DGN-FS-DG13 DIESEL GENERATOR 13 FAILS TO START 2.5E-002 NO EPS-DGN-TM-DG11 DG 11 IS UNAVAILABLE BECAUSE OF MAINTENANCE 3.1E-002 NO EPS-DGN-TM-DG12 DG 12 IS UNAVAILABLE BECAUSE OF MAINTENANCE 3.1E-002 NO EPS-DGN-TM-DG13 DG 13 IS UNAVAILABLE BECAUSE OF MAINTENANCE 3.1E-002 NO EPS-FAN-FC-1DG11 DG11 ROOM COOLING FAN 1 FAILS TO START AND RUN 1.0E-002 NO EPS-FAN-FC-1DG12 DG12 ROOM COOLING FAN 1 FAILS TO START AND RUN 1.0E-002 NO EPS-FAN-FC-2DG11 DG11 ROOM COOLING FAN 2 FAILS TO START AND RUN 1.0E-002 NO EPS-FAN-FC-2DG12 DG12 ROOM COOLING FAN 2 FAILS TO START AND RUN 1.0E-002 NO EPS-XHE-XM-ALTDG OPERATOR FAILS TO ALIGN ALT DG TO DEAD BUS 5.0E-003 YES4 EPS-XHE-XM-CTG OPERATOR FAILS TO START CTG 6.0E-002 NO5 EPS-XHE-XM-CTG1 OPERATOR FAILS TO START CTG 1 1.0E+000 YES5 ESW-MDP-TM-TRNA ESW PUMP A IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.8E-002 NO ESW-MDP-TM-TRNB ESW PUMP B IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.8E-002 NO IE-LOOP LOSS OF OFFSITE POWER INITIATOR 1.0E-007 YES6 IE-LOOP-I LOSS OF OFFSITE POWER TO DIVISION I INITIATOR 1.7E-007 YES7 IE-LOOP-II LOSS OF OFFSITE POWER TO DIVISION II INITIATOR 1.9E-008 YES7 OEP-XHE-NOREC-01H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR TRUE YES1 OEP-XHE-NOREC-02H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 2 HOURS TRUE YES1 OEP-XHE-NOREC-04H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 4 HOURS TRUE YES1
LER 341/01-001 Table 4a. Definitions and probabilities for modified or dominant basic events (Part 1).
Event name Description Probability/
frequency Modified 11 SENSITIVE - NOT FOR PUBLIC DISCLOSURE OEP-XHE-NOREC-10H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 10 HOURS TRUE YES1 Notes:
1.
Updated value for Part 1 to reflect modeling only severe weather LOOPs lasting longer that 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
2.
Updated value for Part 1 using a 24-hour mission time for the diesel generator.
3.
Basic event changed to reflect event being analyzed.
4.
Human error probability updated to reflect greater time to complete action for this condition. Base model updated to reduce Available Time PSF from 10 to 1.
5.
Basic event added to model complete dependence with EPS-XHE-XM-ALTDG.
6.
The LOOP initiating event frequency was reduced to model only those severe weather LOOP initiating events that lasted longer that 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
7.
The divisional LOOP initiating event frequencies were reduced to remain proportional to the full LOOP initiating event frequency.
LER 341/01-001 12 SENSITIVE - NOT FOR PUBLIC DISCLOSURE Table 4b. Definitions and probabilities for modified or dominant basic events (Part 2).
Event name Description Probability/
frequency Modified EPS-DGN-FR-DG11 DIESEL GENERATOR 11 FAILS TO RUN 8.1E-003 NO EPS-DGN-FR-DG12 DIESEL GENERATOR 12 FAILS TO RUN 8.1E-003 NO EPS-DGN-FR-DG14 DIESEL GENERATOR 14 FAILS TO RUN TRUE YES1 EPS-DGN-FS-DG11 DIESEL GENERATOR 11 FAILS TO START 2.5E-002 NO EPS-DGN-FS-DG12 DIESEL GENERATOR 12 FAILS TO START 2.5E-002 NO EPS-DGN-TM-DG11 DG 11 IS UNAVAILABLE BECAUSE OF MAINTENANCE 3.1E-002 NO EPS-DGN-TM-DG12 DG 12 IS UNAVAILABLE BECAUSE OF MAINTENANCE 3.1E-002 NO EPS-FAN-FC-1DG11 DG11 ROOM COOLING FAN 1 FAILS TO START AND RUN 1.0E-002 NO EPS-FAN-FC-1DG12 DG12 ROOM COOLING FAN 1 FAILS TO START AND RUN 1.0E-002 NO EPS-FAN-FC-2DG11 DG11 ROOM COOLING FAN 2 FAILS TO START AND RUN 1.0E-002 NO EPS-FAN-FC-2DG12 DG12 ROOM COOLING FAN 2 FAILS TO START AND RUN 1.0E-002 NO EPS-XHE-XM-ALTDG OPERATOR FAILS TO ALIGN ALT DG TO DEAD BUS 5.0E-002 NO EPS-XHE-XM-CTG OPERATOR FAILS TO START CTG 6.0E-002 NO EPS-XHE-XM-CTG1 OPERATOR FAILS TO START CTG 1 1.0E+000 YES2 ESW-MDP-TM-TRNA ESW PUMP A IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.8E-002 NO ESW-MDP-TM-TRNB ESW PUMP B IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.8E-002 NO OEP-XHE-NOREC-01H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 3.0E-001 NO OEP-XHE-NOREC-10H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 10 HOURS 2.7E-002 NO Notes:
1.
Basic event changed to reflect event being analyzed.
2.
Basic event added to model complete dependence with EPS-XHE-XM-ALTDG.
S LER 341/01-001 13 VA1 LONG-TERM LOW PRE SS INJECTION CR1 CRD INJECT ION (1 PUMP)
CVS CONT AINME NT VENT ING CS S CONTAINMENT SPRAY SDC SHUT DOWN COOLING DEP M ANUAL REACTOR DEPRESS SPC SUPPRESSION POOL COOLING VA ALTERNAT E LOW PRE SS INJECTION LCI LOW PRE SS COOLANT INJECTION LCS CORE SPRAY DE P MANUAL RE ACTOR DE PRE SS HCI HPCI RCI RCIC SFW STANDBY FE EDWATER SRV SRVS CLOSE EPS EME RGENCY POWER RPS REACTOR SHUTDOWN IE-LOOP LOSS OF OFFSITE POWER STATE NOTE S 1
OK 2
OK 3
OK 4
OK 5
CD 6
OK 7
OK 8
CD 9
OK 10 OK 11 OK 12 OK 13 CD 14 OK 15 OK 16 CD 17 CD 18 OK 19 CD 20 OK 21 CD 22 CD 23 OK 24 OK 25 OK 26 OK 27 CD 28 OK 29 OK 30 CD 31 CD 32 OK 33 CD 34 OK 35 CD 36 CD 37 OK 38 OK 39 OK 40 OK 41 OK 42 CD 43 CD 44 OK 45 OK 46 OK 47 OK 48 OK 49 CD 50 CD 51 OK 52 OK 53 OK 54 OK 55 CD 56 CD 57 CD 1
58 T LOOP-1 59 T LOOP-2 60 T SBO 61 CD P1 P2 VA2 VA2 SP1 SD1 CS1 LOOP - LOSS OF OFFSITE POWER 2003/07/15 Figure 1 Loss of offsite power event tree.