IR 05000529/2004001
| ML20100K882 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 02/19/2004 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| IR 2004001 | |
| Download: ML20100K882 (19) | |
Text
Final Precursor Analysis Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Failure to Implement Design of Steam Generator Nozzle Dam Palo Verde, Unit 2 Requiring Extended Reduced Inventory Configuration CDP1 = 1x10-6 Event Date: 2/19/2004 IRs: 50-529/04-04 and -09 Condition Summary Overview. On February 19, 2004 Palo Verde Unit 2 shutdown due to primary to secondary system leakage via steam generator 21. Both steam generators had been replaced during the previous refueling outage which ended in December 2003. On February 24, 2004, during reduced inventory operation with reactor water level at midloop conditions to install the steam generator nozzle dams, maintenance personnel experienced difficulties inserting the hot leg nozzle dams. After several unsuccessful attempts to install the hot leg nozzle dam, plant personnel decided to exit the reduced inventory configuration until the nozzle dam problem was resolved. Plant personnel therefore, removed hot and cold leg steam generator 22 nozzle dams, closed the steam generator manways and raised reactor water level above reduced inventory configuration after being in midloop for 44 hours5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br /> and reduced inventory for 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />. In addition, during this reduced inventory operations plant personnel did not properly vent the in service residual heat removal (RHR) system.
Subsequently, a replacement diaphragm was obtained and was successfully installed with the Ashaved@ pins in the hot leg nozzle dam. Midloop conditions were reentered and both hot and cold leg nozzle dams were successfully installed.
Details. The refueling outage completed in December of 2003 installed new steam generators. The design and fabrication of the new steam generators differed enough from the original steam generators to cause interference between the hot leg nozzle dam lock pins and their steam generator locking ring slots. This prevented the nozzle dams from installing correctly and once installed prevented them from sealing correctly. This problem was not corrected until after the plant operated in an extended reduced inventory condition.
The unit was manually tripped from 21% power on February 19 at 18:23. It entered reduced inventory condition with reactor coolant system (RCS) level below 111 feet at 11:57 on February 23rd, approximately 81 hours9.375e-4 days <br />0.0225 hours <br />1.339286e-4 weeks <br />3.08205e-5 months <br /> after shutdown. Midloop operations were entered several hours later at 21:40 when the RCS level was lowered below 103.08 feet. The reactor exited midloop operations when licensee personnel raised RCS level above 103.08 feet on February 25 at 17:55, it had operated in midloop conditions for approximately 44.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />. It exited reduced inventory conditions on February 26 at 01:01 when RCS water level was raised above 111 feet, after duration of approximately 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />.
For a conditional assessment, the parameter of interest is the measure of importance. This value is obtained subtracting the baseline core damage probability (CDP) from the conditional core damage probability (CCDP).
IR 50-529/04-09 Cause. The plant operated for an extended period in reduce inventory as a result of not correcting the incompatibility between the nozzle dams and the steam generator locking rings. In addition, for much of this time during reduced inventory plant personnel failed to properly vent the operating RHR system.
Condition Duration. The plant operated in reduced inventory conditions for approximately an extra 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> because of the failure to correct the design/fabrication error. After this 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> period at reduced inventory, the plant exited reduced inventory to resolve the nozzle dam problem. Once resolved, the plant re-entered reduced inventory, installed the modified nozzle dams and commenced steam generator inspection and repair activities. After completing the steam generator work, the plant enter reduced inventory for a third time to remove the nozzle dams. If the nozzle dam to locking ring incompatibility had not existed the second and third entry into reduced inventory would still have been required however, the first entry would not have been needed. Thus the original entry into reduced inventory (lasting 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />) and the risk accrued because of this added duration was added risk.
During these 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> the plant failed to properly vent the RHR system for approximately 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />.
Recovery Opportunity. During steam generator fabrication the fabricator was not able to successfully engage the nozzle dam locking pins on new steam generator 21. The cause was determined to be interference between the lock pins and the locking ring slots. The fabricator initiated a change report to document the issue. However, the problem was not corrected during fabrication.
During steam generator installation during the previous refueling outage licensee personnel did not perform a test fit of the actual nozzle dams that would be used during subsequent refueling outages.
Other Related Conditions or Events during the Condition Period. For approximately 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> during reduced inventory operation, plant personnel failed to properly vent the operating shutdown cooling system. This increased the probability of losing the shutdown cooling system due to air entrainment.
Analysis Summary This condition was evaluated using the Palo Verde SPAR model for Low Power and Shutdown (LP/SD). Three cold shutdown reduced inventory plant operating states (POS) were evaluated:
1) RCS intact (POS-M5ERIO), 2) RCS vented and steam generators open (POS-M5ERVO), and 3) RCS vented with steam generators open but blocked (POS-M5ERVB). The times as well as the durations are shown in the table below. Finally, the plant entered reduced inventory operations 81 hours9.375e-4 days <br />0.0225 hours <br />1.339286e-4 weeks <br />3.08205e-5 months <br /> after tripping the reactor; this dictates which time window will be use Importance Because this condition did not involve an actual initiating event, the parameter of interest is the conditional core damage probability with the condition versus a baseline core damage condition.
Even though the nozzle dams where difficult to install their installation was not on the outages critical path and thus the condition did not extend the outage length. If the condition did not exist then the plant personnel would have installed the nozzle dams and returned the reactor water level to a normal value for a maintenance outage. This would be a cold shutdown condition with temperature below 200 F and level in the pressurizer. Thus this is the baseline risk to be compared against and is given in Table 1 below labeled Mode 5 Flooded.
The change in risk is obtained by subtracting the base case CDP from the mode 5 reduced inventory
IR 50-529/04-09 total risk for the 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> of additional reduced inventory operations. The base case Palo Verde LP/SD SPAR calculates a CDF of 1.9E-7 per hour (1.6E-3 per year) assuming the nominal availability of all mitigating systems modeled. This yields base case CDF for a 61-hour duration of 1.1E-5.
During the reduced inventory operation, three POS were evaluated as discussed above. The total CDP for the 61 hour7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> duration is 1.3E-5. Therefore, the difference in the CDP between at-power and LP/SD is approximately 1.3E-6. See Table 1 for the details.
Table 1. Base CDP Calculation Plant Operating State (POS) Description POS CCDF POS CDP Identifier (per Durations hour) (hours:
minutes)
Mode 5 reduced inventory, no vent, not block PI-M5ERIO 1.5E-07 24:05 3.7E-6 Mode 5 reduced inventory, vented, open PI-MRERVO 2.6E-07 22:18 5.9E-6 Mode 5 reduced inventory, vented and blocked PI-M5ERVB 2.0E-07 14:41 3.0E-6 Total mode 5 reduced inventory 61:04 1.3E-5 Mode 5 Flooded (Base Line Risk) PI-M5EFIO 1.9E-07 61:04 1.1E-5 Change in risk 1.3E-6 As discussed above, four different POSs were solved. Each was solved with independent change sets in SAPHIRE: One change set with the reactor in cold shutdown and the water level in the pressurizer, and three change sets, one for each for the reduced inventory POSs. The cutsets for each of the change sets are presented in Tables 4a1, 4a2 and 4a3 below. Table 4b supplies definitions for variables in Tables 4a. Table 5 contains the change set parameter values. Finally, Appendix A contains the dominant event tree Sensitivity Case for Improperly Venting Running RHR Pump As discussed in the Other Related Condition section above, for 25 of the 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> of reduced inventory operation, plant personnel failed to properly vent the operating shutdown cooling system.
This allowed air to accumulate in the system. If too much air accumulates, the system will fail.
Therefore, failing to properly vent the system increased the failure to run probability of the system.
The LP/SD SPAR model treats the loss of shutdown cooling with a compound initiating event called IE-LORHR. This compound basic event is composed of the following parts with the values shown:
Table 2. IE-LORHR Components Value Initiating Event Name Description (per hour)
IEX-LORHR-ESFAS Emergency Safety Feature Actuation Signal Isolates RHR 4.5E-6 IEX-LORHR-RHR1 Spurious Closure of RHR Suction Valve 1.4E-5 IEX-LORHR-RHR3 Non-Recoverable Loss of RHR System 1.5E-5 IEX-LORHR-RHR4 Loss of Operating Train of RHR System 6.9E-6 IEX-LORHR-RHR5 Interruption of Operating RHR System 1.2E-5 IE-LORHR Total 5.2E-5 To understand the impact on shutdown cooling of the entrained air, sensitivity cases were conducted.
The sensitivity cases modified the initiating event (IE-LORHR) to include a sixth element called IEX-LORHR-AIR. This basic event failure probability was varied between 1% and 50% in the 61 hour7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />
IR 50-529/04-09 exposure time. In reality the exposure time was actually 25 not 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> but this assumption conservatively bounds the situation and simplifies the risk impact calculation. Three additional SPAR model runs were performed. The results are presented in Table 3. These sensitivity cases compare the risk from 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> at reduced inventory assuming the RHR pump was being properly vented to cases where the pump was not being properly vented.
Table 3. Sensitivity Case Results Assumed 1 Reduced Probability of IEX-LORHR-AIR IE-LORHR2 3 Case Inventory CDP Failure (in 61 (per hour) (per hour)
CDP hours)
2A 1% 1.6E-4 2.2E-4 1.3E-5 3.5E-7 2B 10% 1.6E-3 1.7E-3 1.6E-5 3.7E-6 2C 50% 8.2E-3 8.2E-3 3.1E-5 1.9E-5 Note:
1) Calculated by dividing the Assumed Probability of Failure by 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />.
2) IEX-LORHR is calculated by adding IE-LORHR-AIR to the base case value of IE-LORHR in Table 2.
3) CDP is calculated by subtracting the total mode 5 reduced inventory risk of 1.3E-5 in Table 1 from the sensitivity case results.
The results of Table 3 indicate that the risk evaluation is somewhat sensitive to the entrainment of air into the shutdown cooling system. Note that the change in the reduced inventory CDP is not changed proportionately with the change in IE-LORHR as this is only one of three initiating events evaluated in the mode Table 4a1. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERIO Cut % Cut Prob./
Basic Event Description Event Pro N Set Frequency 1 81.63 1.261E-007 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001 PI-M5ERIO POS Identifier 1.000E+000 RCS-XHE-XE-INVT2 OPERATOR FAILS TO TERMINATE LOSS OF INVENTORY 2.600E-002 2 12.35 1.908E-008 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 AFW-XHE-XM-POSM5XR Operator fails to initiate and align AFW for POS-M5XR 1.000E-003 IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event 5.206E-005 PI-M5ERIO POS Identifier 1.000E+000 RHR-SYS-NONREC RHR SYSTEM NOT RECOVERABLE 3.665E-001 3 4.26 6.580E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOOP LOSS OF OFFSITE POWER INITIATING EVENT 1.400E-005 LOP-XHE-XE-DIA23 OPERATOR FAILS TO DIAGNOSE LOOP 4.700E-004 PI-M5ERIO POS Identifier 1.000E+000 4 0.40 6.247E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event 5.206E-005 PI-M5ERIO POS Identifier 1.000E+000 RHR-XHE-XE-DIA23 OPERATOR FAILS TO DIAGNOSE LOSS OF RHR 1.200E-005 5 0.19 2.993E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-CCF-PG-SUMP2 Containment sump plugging during TW-2 fails recirculation 1.000E-001 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 PI-M5ERIO POS Identifier 1.000E+000 RCS-XHE-XE-INVT2 OPERATOR FAILS TO TERMINATE LOSS OF INVENTORY 2.600E-002 6 0.15 2.302E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000
IR 50-529/04-09 Table 4a1. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERIO IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 PI-M5ERIO POS Identifier 1.000E+000 RCS-XHE-XM-MU23 Operator fails to initiate RCS make-up during TW-2or3 2.000E-005 7 0.12 1.872E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOLC LPSD IE - Loss Of Level Control (reduced RCS inv) - CE 9.360E-006 PI-M5ERIO POS Identifier 1.000E+000 RCS-XHE-XM-MU23 Operator fails to initiate RCS make-up during TW-2or3 2.000E-005 8 0.08 1.197E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 HPI-CKV-CF-RWT COMMON CAUSE FAILURE OF RWT DISCAHRGE CHECK VALVES 1.040E-005 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 PI-M5ERIO POS Identifier 1.000E+000 9 0.06 9.734E-011 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 HPI-CKV-CF-RWT COMMON CAUSE FAILURE OF RWT DISCAHRGE CHECK VALVES 1.040E-005 IE-LOLC LPSD IE - Loss Of Level Control (reduced RCS inv) - CE 9.360E-006 PI-M5ERIO POS Identifier 1.000E+000 10 0.05 8.260E-011 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 AFW-XHE-XM-POSM5XR Operator fails to initiate and align AFW for POS-M5XR 1.000E-003 IE-LOOP LOSS OF OFFSITE POWER INITIATING EVENT 1.400E-005 PI-M5ERIO POS Identifier 1.000E+000 RHR-XHE-XM-LOP23 OPERATOR FAILS TO RESTORE RHR SYSTEM 5.900E-003 Table 4a2. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut % Cut Prob./
Basic Event Description Event Prob.
N Set Frequency 1 47.68 1.261E-007 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001 PI-M5ERVO POS Identifier 1.000E+000 RCS-XHE-XE-INVT2 OPERATOR FAILS TO TERMINATE LOSS OF INVENTORY 2.600E-002 2 9.60 2.540E-008 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 RCS-XHE-XM-GRAVF OPERATOR FAILS TO ALIGN GRAVITY FEED 1.000E+000 RCS-XHE-XM-MU23 Operator fails to initiate RCS make-up during TW-2or3 2.000E-005 3 8.66 2.290E-008 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event 5.206E-005 OPR-XHE-XM-FRRW23 OPERATOR FAILS TO INITIATE FORCED FEED IN TW-2&3 (LORHR) 1.200E-003 PI-M5ERVO POS Identifier 1.000E+000 RCS-XHE-XM-GRAVF OPERATOR FAILS TO ALIGN GRAVITY FEED 1.000E+000 RHR-SYS-NONREC RHR SYSTEM NOT RECOVERABLE 3.665E-001 4 7.21 1.908E-008 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-CCF-PG-SUMP2 Containment sump plugging during TW-2 fails recirculation 1.000E-001 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event 5.206E-005 PI-M5ERVO POS Identifier 1.000E+000 RHR-SYS-NONREC RHR SYSTEM NOT RECOVERABLE 3.665E-001 5 3.13 8.265E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000
IR 50-529/04-09 Table 4a2. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut % Cut Prob./
Basic Event Description Event Prob.
N Set Frequency RCS-CKV-CF-ALL CCF OF RCS INLET CHECK VALVES 6.508E-006 RCS-XHE-XM-GRAVF OPERATOR FAILS TO ALIGN GRAVITY FEED 1.000E+000 6 2.49 6.580E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOOP LOSS OF OFFSITE POWER INITIATING EVENT 1.400E-005 LOP-XHE-XE-DIA23 OPERATOR FAILS TO DIAGNOSE LOOP 4.700E-004 PI-M5ERVO POS Identifier 1.000E+000 7 2.45 6.477E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 LOI-XHE-XE-DIA23 OPERATOR FAILS TO DIAGNOSE LOSS OF INVENTORY 5.100E-006 PI-M5ERVO POS Identifier 1.000E+000 8 1.83 4.850E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 SDC-XHE-XM OPERATOR FAILS TO INITIATE THE SDC SYSTEM 1.000E-003 9 0.95 2.522E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 RHR-XHE-XM-LOI23 OPERATOR FAILS TO RESTORE RHR SYSTEM 5.200E-004 10 0.94 2.476E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 ESP-MDP-CF-STRT CCF OF ESSENTIAL SPRAY POND MDP'S TO START 1.950E-004 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 11 0.94 2.476E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 ECW-MDP-CF-STRT CCF OF ESSENTIAL COOLING WATER SYSTEM MDP'S TO START 1.950E-004 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 12 0.48 1.270E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-CCF-PG-SUMP2 Containment sump plugging during TW-2 fails recirculation 1.000E-001 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 SDC-XHE-XM OPERATOR FAILS TO INITIATE THE SDC SYSTEM 1.000E-003 13 0.43 1.143E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 ACP-BAC-LP-PBA 4160V AC BUS PBA-S03 FAILS 9.000E-005 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 14 0.36 9.458E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 ESP-MDP-CF-STRT CCF OF ESSENTIAL SPRAY POND MDP'S TO START 1.950E-004 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000
IR 50-529/04-09 Table 4a2. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut % Cut Prob./
Basic Event Description Event Prob.
N Set Frequency PI-M5ERVO POS Identifier 1.000E+000 15 0.36 9.458E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 ECW-MDP-CF-STRT CCF OF ESSENTIAL COOLING WATER SYSTEM MDP'S TO START 1.950E-004 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 16 0.36 9.458E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 LPI-MDP-CF-START COMMON CAUSE FAILURE OF LPI TRAINS TO START 1.950E-004 PI-M5ERVO POS Identifier 1.000E+000 17 0.25 6.608E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOOP LOSS OF OFFSITE POWER INITIATING EVENT 1.400E-005 OPR-XHE-XM-FLLW23 OPERATOR FAILS TO INITIATE FORCED FEED IN TW-2&3 (LOOP) 8.000E-003 PI-M5ERVO POS Identifier 1.000E+000 RCS-XHE-XM-GRAVF OPERATOR FAILS TO ALIGN GRAVITY FEED 1.000E+000 RHR-XHE-XM-LOP23 OPERATOR FAILS TO RESTORE RHR SYSTEM 5.900E-003 18 0.25 6.604E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-CCF-PG-SUMP2 Containment sump plugging during TW-2 fails recirculation 1.000E-001 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 RHR-XHE-XM-LOI23 OPERATOR FAILS TO RESTORE RHR SYSTEM 5.200E-004 19 0.24 6.247E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event 5.206E-005 PI-M5ERVO POS Identifier 1.000E+000 RHR-XHE-XE-DIA23 OPERATOR FAILS TO DIAGNOSE LOSS OF RHR 1.200E-005 20 0.18 4.860E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 SDC-MOV-CF-651652 CCF OF SDC SUCTION MOVs UV-651/652 1.002E-004 21 0.18 4.860E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 SDC-MOV-CF-HTXOUT CCF OF SDC OUTLET MOVs HV-686/696 FROM CSR HTXs 1.002E-004 22 0.18 4.860E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 SDC-MOV-CF-653654 CCF OF SDC SUCTION MOVs UV-653/654 1.002E-004 23 0.18 4.860E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000
IR 50-529/04-09 Table 4a2. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut % Cut Prob./
Basic Event Description Event Prob.
N Set Frequency IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 SDC-MOV-CF-655656 CCF OF SDC SUCTION MOVs UV-655/656 1.002E-004 24 0.18 4.860E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 SDC-MOV-CF-BYP CCF OF SDC HTX BYPASS MOVs 1.002E-004 25 0.18 4.860E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVO POS Identifier 1.000E+000 SDC-MOV-CF-657658 CCF OF SDC OUTLET MOVs HV-657/658 FROM CSR HTXs 1.002E-004 26 0.18 4.743E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 CSR-HTX-CF-ALL COMMON CAUSE FAILURE OF SHUTDOWN HTXs 3.734E-005 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 27 0.18 4.743E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 ECW-HTX-CF-HTXS CCF OF ECW LOOPA/B HEAT EXCHANGERS 3.734E-005 IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr) 1.270E-003 PI-M5ERVO POS Identifier 1.000E+000 Table 4a3. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVB Cut % Cut Prob./
Basic Event Description Event Prob.
N Set Frequency 1 61.75 1.261E-007 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001 PI-M5ERVB POS Identifier 1.000E+000 RCS-XHE-XE-INVT2 OPERATOR FAILS TO TERMINATE LOSS OF INVENTORY 2.600E-002 2 11.21 2.290E-008 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event 5.206E-005 OPR-XHE-XM-FRRW23 OPERATOR FAILS TO INITIATE FORCED FEED IN TW-2&3 (LORHR) 1.200E-003 PI-M5ERVB POS Identifier 1.000E+000 RCS-XHE-XM-GRAVF OPERATOR FAILS TO ALIGN GRAVITY FEED 1.000E+000 RHR-SYS-NONREC RHR SYSTEM NOT RECOVERABLE 3.665E-001 3 9.34 1.908E-008 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 C-CCF-PG-SUMP2 Containment sump plugging during TW-2 fails recirculation 1.000E-001 C-XHE-ALT-RWST2 Operators fail to align alternate RWST water source (TW-2) 1.000E-002 IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event 5.206E-005 PI-M5ERVB POS Identifier 1.000E+000 RHR-SYS-NONREC RHR SYSTEM NOT RECOVERABLE 3.665E-001
IR 50-529/04-09 Table 4a3. Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVB Cut % Cut Prob./
Basic Event Description Event Prob.
N Set Frequency 4 3.22 6.580E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOOP LOSS OF OFFSITE POWER INITIATING EVENT 1.400E-005 LOP-XHE-XE-DIA23 OPERATOR FAILS TO DIAGNOSE LOOP 4.700E-004 PI-M5ERVB POS Identifier 1.000E+000 5 2.38 4.850E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVB POS Identifier 1.000E+000 SDC-XHE-XM OPERATOR FAILS TO INITIATE THE SDC SYSTEM 1.000E-003 6 1.24 2.522E-009 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVB POS Identifier 1.000E+000 RHR-XHE-XM-LOI23 OPERATOR FAILS TO RESTORE RHR SYSTEM 5.200E-004 7 0.46 9.458E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 ESP-MDP-CF-STRT CCF OF ESSENTIAL SPRAY POND MDP'S TO START 1.950E-004 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVB POS Identifier 1.000E+000 8 0.46 9.458E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 ECW-MDP-CF-STRT CCF OF ESSENTIAL COOLING WATER SYSTEM MDP'S TO START 1.950E-004 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 PI-M5ERVB POS Identifier 1.000E+000 9 0.46 9.458E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event 1.151E-005 LOI-NO-ECR Given a LOI IE, prob that LOCA is outside containment - CE 4.214E-001
/LOI-NT LOSS OF INVENTORY TERMINATED 1.000E+000 LPI-MDP-CF-START COMMON CAUSE FAILURE OF LPI TRAINS TO START 1.950E-004 PI-M5ERVB POS Identifier 1.000E+000 10 0.32 6.608E-010 SD Plant Shutdown (Mode 4, 5 or 6) 1.000E+000 IE-LOOP LOSS OF OFFSITE POWER INITIATING EVENT 1.400E-005 OPR-XHE-XM-FLLW23 OPERATOR FAILS TO INITIATE FORCED FEED IN TW-2&3 (LOOP) 8.000E-003 PI-M5ERVB POS Identifier 1.000E+000 RCS-XHE-XM-GRAVF OPERATOR FAILS TO ALIGN GRAVITY FEED 1.000E+000 RHR-XHE-XM-LOP23 OPERATOR FAILS TO RESTORE RHR SYSTEM 5.900E-003
IR 50-529/04-09 Table 4b. Definitions of Basic Events Listed in Tables 4a1, 2 & 3 Top Event Definition IE-LOI SHUTDOWN IE - LOSS OF INVENTORY - Compound Event IE-LOIRI SD IE - Loss of Inventory - overdraining (per M5xRV hr)
IE-LOLC LPSD IE - Loss Of Level Control (reduced RCS inv) - CE IE-LOOP LOSS OF OFFSITE POWER INITIATING EVENT IE-LORHR SHUTDOWN IE - LOSS OF RHR - Compound Event LOI-NT Loss of Inventory Terminated MODE5 Plant is in mode 5 M5E Early time frame for Mode-5 M5ER Reduced RCS inventory given Early Mode-5 M5ERV Vented RCS given Reduced-RCS and Early Mode-5 M5ERVB Blocked RCS loops given Vented-Reduced-RCS and Early Mode-5 PI-M5ERIO POS Identifier PI-M5ERVB POS Identifier PI-M5ERVO POS Identifier TW2M5E Time Window 2 Mode-5 Early Table 5. Change Set Values Change/Flag Set Event Cal Prob/ Description Type Freq 1 Feb 2004 SGTR outage - CSD full TW2 M4ERIO SIR-529-2004-009-EFIO Sequences solved: 08-10 to 08-1 M5E T Early time frame for Mode-5 M5ER F Reduced RCS inventory given Early Mode-5 MODE5 T Plant is in mode 5 PI-M5EFIO P 1 POS Identifier TW2M5E T Time Window 2 Mode-5 Early Feb 2004 SGTR outage - CSD TW2 M5ERIO SIR-529-2004-009-ERIO Sequences solved: 09-10 to 09-1 M5E T Early time frame for Mode-5 M5ER T Reduced RCS inventory given Early Mode-5 M5ERV F Vented RCS given Reduced-RCS and Early Mode-5 MODE5 T Plant is in mode 5 PI-M5ERIO P 1 POS Identifier TW2M5E T Time Window 2 Mode-5 Early Feb 2004 SGTR outage - CSD TW2 M5ERVO SIR-529-2004-009-ERVO Sequences solved: 10-10 to 10-1 M5E T Early time frame for Mode-5 M5ER T Reduced RCS inventory given Early Mode-5 M5ERV T Vented RCS given Reduced-RCS and Early Mode-5 M5ERVB F Blocked RCS loops given Vented-Reduced-RCS and Early Mode-5 MODE5 T Plant is in mode 5 PI-M5ERVO P 1 POS Identifier TW2M5E T Time Window 2 Mode-5 Early Feb 2004 SGTR outage - CSD TW2 M5ERVB SIR-529-2004-009-ERVB Sequences solved: 11-10 to 11-1 M5E T Early time frame for Mode-5 M5ER T Reduced RCS inventory given Early Mode-5 M5ERV T Vented RCS given Reduced-RCS and Early Mode-5 M5ERVB T Blocked RCS loops given Vented-Reduced-RCS and Early Mode-5 MODE5 T Plant is in mode 5 PI-M5ERVB P 1 POS Identifier TW2M5E T Time Window 2 Mode-5 Early Note 1: This is the change set for the base case (cold shutdown, flooded without the nozzle dams installed; cutsets are not given for this change set cas IR 50-529/04-09 Appendix A Event Tree Models
IR 50-529/04-09 Plant Plant Mode RCS RCS RCS Shutdown is in Time Inventory Integrity Loop (Mode 4, 5 or 6) Mode Frame Status Status Status SD MODE MXE MXXR MXXXV MXXXXB # PLANT_STATE 1 @
Open(0.01)
Mode6 (0.44) 2 T POS-M6XFVO N/A Full Vented RCS Open Blocked(0.99)
3 T POS-M6XFVB Full Intact Open 4 T POS-M5LFIO Late Intact 5 T POS-M5LRIO Reduced(0.04)
Open 6 T POS-M5LRVO Mode5 (0.47) Vented(0.5)
Blocked(0.99)
7 T POS-M5LRVB RCS de-pressurized Full 8 T POS-M5EFIO Early(0.36) Intact 9 T POS-M5ERIO Reduced(0.42)
Open 10 T POS-M5ERVO Vented(0.1)
Blocked(0.28)
11 T POS-M5ERVB Late(0.48) Full Intact Open Mode4 (0.08) 12 T POS-M4LFIO RCS Early(0.52) Full Intact Open 13 T POS-M4EFIO Pressurized Figure A-1. Shutdown (SD)
IR 50-529/04-09 Plant POS Time LP/SD Operating Identifier Window Initiating State Event POS PI-M5ERIO TW IE # Transfer 1 @
2 @
3 @
IE-LORHR 4 T LORHR-M5XR IE-LOI TW1M5E(0.21) 5 T LOI-M5XR IE-LOLC 6 T LOIRI-M5XR IE-LOIRI 7 @LOIRI-M5XR IE-LOOP 8 T LOOP-M5XR 9 @
10 T LORHR-M5XR TW2M5E(0.40) 11 T LOI-M5XR PI-M5ERIO 12 T LOIRI-M5XR 13 @LOIRI-M5XR 14 T LOOP-M5XR 15 @
16 T LORHR-M5XR TW3M5E(0.30) 17 T LOI-M5XR 18 T LOIRI-M5XR 19 @LOIRI-M5XR 20 T LOOP-M5XR 21 @
22 T LORHR-M5XR TW4M5E(0.09) 23 T LOI-M5XR 24 T LOIRI-M5XR 25 @LOIRI-M5XR 26 T LOOP-M5XR Figure A-2. POS-M5ERIO
IR 50-529/04-09 Plant POS Time LP/SD Operating Identifier Window Initiating State Event POS PI-M5ERVO TW IE # Transfer 1 @
2 @
3 @
IE-LORHR 4 T LORHR-M5XR IE-LOI TW1M5E(0.21) 5 T LOI-M5XR IE-LOLC 6 T LOIRI-M5XR IE-LOIRI 7 T LOIRI-M5XR IE-LOOP 8 T LOOP-M5XR 9 @
IE-LORHR 10 T LORHR-M5XR IE-LOI TW2M5E(0.40) 11 T LOI-M5XR IE-LOLC PI-M5ERVO 12 T LOIRI-M5XR IE-LOIRI 13 T LOIRI-M5XR IE-LOOP 14 T LOOP-M5XR 15 @
16 T LORHR-M5XR TW3M5E(0.30) 17 T LOI-M5XR 18 T LOIRI-M5XR 19 T LOIRI-M5XR 20 T LOOP-M5XR 21 @
22 T LORHR-M5XR TW4M5E(0.09) 23 T LOI-M5XR 24 T LOIRI-M5XR 25 T LOIRI-M5XR 26 T LOOP-M5XR Figure A-3. POS-M5ERVO
IR 50-529/04-09 Plant POS Time LP/SD Operating Identifier Window Initiating State Event POS PI-M5ERVB TW IE # Transfer 1 @
2 @
3 @
IE-LORHR 4 T LORHR-M5XR IE-LOI TW1M5E(0.21) 5 T LOI-M5XR IE-LOLC 6 T LOIRI-M5XR IE-LOIRI 7 @LOIRI-M5XR IE-LOOP 8 T LOOP-M5XR 9 @
IE-LORHR 10 T LORHR-M5XR IE-LOI TW2M5E(0.40) 11 T LOI-M5XR IE-LOLC PI-M5ERVB 12 T LOIRI-M5XR IE-LOIRI 13 @LOIRI-M5XR IE-LOOP 14 T LOOP-M5XR 15 @
16 T LORHR-M5XR TW3M5E(0.30) 17 T LOI-M5XR 18 T LOIRI-M5XR 19 @LOIRI-M5XR 20 T LOOP-M5XR 21 @
22 T LORHR-M5XR TW4M5E(0.09) 23 T LOI-M5XR 24 T LOIRI-M5XR 25 @LOIRI-M5XR 26 T LOOP-M5XR Figure A-4. POS-M5ERVB
IR 50-529/04-09 LORHR OPERATOR RHR RCS SECONDARY FORCED BLEED GRAVITY LONG-TERM M5XR DIAGNOSES RECOVERY VENTED (REFLUX) FEED (SPILL) FEED RECIRC EVENT COOLING IE D R V S F B G C # STATE 1 OK 2 OK 3 CD 4 OK 5 CD 6 OK 7 OK 8 CD 9 CD F-HPI 10 CD 11 CD Figure A-5. LORHR-M5XR
IR 50-529/04-09 LOI OPERATOR RCS Loss of RHR RCS SECONDARY FORCED BLEED GRAVITY LONG-TERM M5XR DIAGNOSES Inventory Inventory RECOVERY VENTED (REFLUX) FEED (SPILL) FEED RECIRC EVENT Make-UP Terminated COOLING IE D M LOI-NT R V S F B G C # STATE 1 OK 2 OK 3 CD 4 OK 5 OK 6 CD 7 CD F-HPI 8 CD 9 OK 10 CD 11 OK 12 CD 13 CD 14 CD Figure A-6. LOI-M5XR
IR 50-529/04-09 LOIRI OPERATOR RCS RHR RCS SECONDARY FORCED BLEED GRAVITY LONG-TERM M5XR DIAGNOSES INVENTORY RECOVERY VENTED (REFLUX) FEED (SPILL) FEED RECIRC EVENT MAKE-UP COOLING IE D M R V S F B G C # STATE 1 OK 2 OK Vented 3 CD 4 OK 5 OK Not Vented 6 CD 7 CD F-HPI 8 CD 9 OK 10 CD 11 CD 12 CD Figure A-7. LOIRI-M5XR
IR 50-529/04-09 LOOP OPERATOR Loss of RHR RCS OFFSITE SECONDARY FORCED BLEED GRAVITY LONG-TERM M5XR DIAGNOSES EMERGENCY RECOVERY VENTED POWER (REFLUX) FEED (SPILL) FEED RECIRC EVENT AC POWER RECOVERY COOLING IE D EPS-LPSD R V N S F B G C # STATE 1 OK 2 OK 3 CD 4 OK 5 CD 6 OK C-L N-L 7 CD F-L 8 OK 9 CD 10 OK 11 OK 12 CD 13 CD F-HPI 14 CD 15 OK 16 OK N-L C-L 17 CD S-L B-L 18 CD F-HPI-L 19 CD 20 OK 21 CD 22 OK 23 CD 24 OK 25 CD 26 OK 27 OK 28 CD 29 CD F-HPI 30 CD 31 CD 32 CD Figure A-8. LOOP-M5XR 19