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 Palo Verde, Unit 2 Failure to Implement Design of Steam Generator Nozzle Dam Requiring Extended Reduced Inventory Configuration Event Date: 2/19/2004 IRs: 50-529/04-04 and -09 CDP1 = 1x10-6
Condition Summary Overvie On February 19, 2004 Palo Verde Unit 2 shutdown due to primary to secondary system leakage via steam generator 2 Both steam generators had been replaced during the previous refueling outage which ended in December 200 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 dam 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 resolve 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 hour7.060185e-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) syste Subsequently, a replacement diaphragm was obtained and was successfully installed with the Ashaved@ pins in the hot leg nozzle da Midloop conditions were reentered and both hot and cold leg nozzle dams were successfully installe Detail The refueling outage completed in December of 2003 installed new steam generator 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 slot This prevented the nozzle dams from installing correctly and once installed prevented them from sealing correctl This problem was not corrected until after the plant operated in an extended reduced inventory conditio The unit was manually tripped from 21% power on February 19 at 18:2 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 shutdow Midloop operations were entered several hours later at 21:40 when the RCS level was lowered below 103.08 fee 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 hour2.893519e-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 hour7.060185e-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 importanc This value is obtained subtracting the baseline core damage probability (CDP) from the conditional core damage probability (CCDP).
IR 50-529/04-09 Caus 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 ring In addition, for much of this time during reduced inventory plant personnel failed to properly vent the operating RHR syste Condition Duratio 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 erro 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 proble Once resolved, the plant re-entered reduced inventory, installed the modified nozzle dams and commenced steam generator inspection and repair activitie After completing the steam generator work, the plant enter reduced inventory for a third time to remove the nozzle dam 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 neede 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 ris 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 hour2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> Recovery Opportunit During steam generator fabrication the fabricator was not able to successfully engage the nozzle dam locking pins on new steam generator 2 The cause was determined to be interference between the lock pins and the locking ring slot The fabricator initiated a change report to document the issu However, the problem was not corrected during fabricatio 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 outage Other Related Conditions or Events during the Condition Perio 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 syste This increased the probability of losing the shutdown cooling system due to air entrainmen 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 belo 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 conditio 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 lengt 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 outag This would be a cold shutdown condition with temperature below 200 F and level in the pressurize Thus this is the baseline risk to be compared against and is given in Table 1 below labeled Mode 5 Floode 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 operation 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 modele This yields base case CDF for a 61-hour duration of 1.1E-During the reduced inventory operation, three POS were evaluated as discussed abov 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-Therefore, the difference in the CDP between at-power and LP/SD is approximately 1.3E-See Table 1 for the detail Table Base CDP Calculation Plant Operating State (POS) Description POS Identifier CCDF (per hour)
POS Durations (hours:
minutes)
CDP 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 solve 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 POS The cutsets for each of the change sets are presented in Tables 4a1, 4a2 and 4a3 belo Table 4b supplies definitions for variables in Tables 4 Table 5 contains the change set parameter value 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 syste This allowed air to accumulate in the syste If too much air accumulates, the system will fai Therefore, failing to properly vent the system increased the failure to run probability of the syste The LP/SD SPAR model treats the loss of shutdown cooling with a compound initiating event called IE-LORH This compound basic event is composed of the following parts with the values shown:
Table IE-LORHR Components Initiating Event Name Description Value (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 conducte The sensitivity cases modified the initiating event (IE-LORHR) to include a sixth element called IEX-LORHR-AI 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 tim 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 calculatio Three additional SPAR model runs were performe The results are presented in Table 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 vente Table Sensitivity Case Results Case Assumed Probability of Failure (in 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />)
IEX-LORHR-AIR1 (per hour)
IE-LORHR2 (per hour)
Reduced Inventory CDP CDP3 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 hour7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br /> )
IEX-LORHR is calculated by adding IE-LORHR-AIR to the base case value of IE-LORHR in Table )
CDP is calculated by subtracting the total mode 5 reduced inventory risk of 1.3E-5 in Table 1 from the sensitivity case result The results of Table 3 indicate that the risk evaluation is somewhat sensitive to the entrainment of air into the shutdown cooling syste 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 4a Conditional Cutsets for Dominating Sequences with Logic for POS M5ERIO Cut N % Cut Set Prob./
Frequency Basic Event Description Event Pro.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
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
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
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
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
0.15 2.302E-010 SD Plant Shutdown (Mode 4, 5 or 6)
1.000E+000
IR 50-529/04-09
Table 4a 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
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
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
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
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 4a Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut N % Cut Set Prob./
Frequency Basic Event Description Event Pro.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
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
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
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
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 4a Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut N % Cut Set Prob./
Frequency Basic Event Description Event Pro 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
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
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
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
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
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
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
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
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
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 4a Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut N % Cut Set Prob./
Frequency Basic Event Description Event Pro PI-M5ERVO POS Identifier 1.000E+000
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
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
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
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
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
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
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
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
0.18 4.860E-010 SD Plant Shutdown (Mode 4, 5 or 6)
1.000E+000
IR 50-529/04-09
Table 4a Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVO Cut N % Cut Set Prob./
Frequency Basic Event Description Event Pro 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
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
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
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
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 4a Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVB Cut N % Cut Set Prob./
Frequency Basic Event Description Event Pro.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
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
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 4a Conditional Cutsets for Dominating Sequences with Logic for POS M5ERVB Cut N % Cut Set Prob./
Frequency Basic Event Description Event Pro.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
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
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
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
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
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
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 4 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 Change Set Values Change/Flag Set Event Cal Type Prob/
Freq Description SIR-529-2004-009-EFIO
Feb 2004 SGTR outage - CSD full TW2 M4ERIO 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
POS Identifier
TW2M5E T
Time Window 2 Mode-5 Early SIR-529-2004-009-ERIO
Feb 2004 SGTR outage - CSD TW2 M5ERIO 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
POS Identifier
TW2M5E T
Time Window 2 Mode-5 Early SIR-529-2004-009-ERVO
Feb 2004 SGTR outage - CSD TW2 M5ERVO 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
POS Identifier
TW2M5E T
Time Window 2 Mode-5 Early SIR-529-2004-009-ERVB
Feb 2004 SGTR outage - CSD TW2 M5ERVB 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
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
MXXXXB RCS Loop Status MXXXV RCS Integrity Status MXXR RCS Inventory Status MXE Mode Time Frame MODE Plant is in Mode SD Plant Shutdown (Mode 4, 5 or 6)
PLANT_STATE
@
T POS-M6XFVO
T POS-M6XFVB
T POS-M5LFIO
T POS-M5LRIO
T POS-M5LRVO
T POS-M5LRVB
T POS-M5EFIO
T POS-M5ERIO
T POS-M5ERVO
T POS-M5ERVB
T POS-M4LFIO
T POS-M4EFIO Mode5 (0.47)
Early(0.36)
Late Reduced(0.04)
Full Vented(0.5)
Intact Blocked(0.99)
Open Intact Open Mode4 (0.08)
Full Vented Blocked(0.99)
Late(0.48)
Early(0.52)
Full Full Intact Intact Open Open Full Reduced(0.42)
Open(0.01)
N/A RCS Open RCS de-pressurized RCS Pressurized Intact Vented(0.1)
Open Blocked(0.28)
Mode6 (0.44)
Figure A-Shutdown (SD)
IR 50-529/04-09
Figure A-POS-M5ERIO IE LP/SD Initiating Event TW Time Window PI-M5ERIO POS Identifier POS Plant Operating State
Transfer
@
@
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
@LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
@LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
@LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
@LOIRI-M5XR
T LOOP-M5XR IE-LORHR IE-LOI IE-LOLC IE-LOIRI IE-LOOP TW1M5E(0.21)
PI-M5ERIO TW2M5E(0.40)
TW3M5E(0.30)
TW4M5E(0.09)
IR 50-529/04-09
IE LP/SD Initiating Event TW Time Window PI-M5ERVO POS Identifier POS Plant Operating State
Transfer
@
@
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
T LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
T LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
T LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR
T LOIRI-M5XR
T LOIRI-M5XR
T LOOP-M5XR PI-M5ERVO TW1M5E(0.21)
IE-LORHR IE-LOI IE-LOLC IE-LOIRI IE-LOOP TW2M5E(0.40)
TW3M5E(0.30)
TW4M5E(0.09)
IE-LORHR IE-LOI IE-LOLC IE-LOIRI IE-LOOP
Figure A-POS-M5ERVO
IR 50-529/04-09
Plant
Figure A-POS-M5ERVB IE-LORHR IE-LOI IE-LOLC IE-LOIRI IE-LOOP PI-M5ERVB IE LP/SD Initiating Event TW Time Window PI-M5ERVB POS Identifier POS Operating State
Transfer
@
@
@
IE-LORHR
T LORHR-M5XR IE-LOI
T LOI-M5XR TW1M5E(0.21)
IE-LOLC
T LOIRI-M5XR IE-LOIRI
@LOIRI-M5XR IE-LOOP
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR TW2M5E(0.40)
T LOIRI-M5XR PI-M5ERVB
@LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR TW3M5E(0.30)
T LOIRI-M5XR
@LOIRI-M5XR
T LOOP-M5XR
@
T LORHR-M5XR
T LOI-M5XR TW4M5E(0.09)
T LOIRI-M5XR
@LOIRI-M5XR
T LOOP-M5XR
IR 50-529/04-09
Figure A-LORHR-M5XR C
LONG-TERM RECIRC G
GRAVITY FEED B
BLEED (SPILL)
F FORCED FEED S
SECONDARY (REFLUX)
COOLING V
RCS VENTED R
RHR RECOVERY D
OPERATOR DIAGNOSES EVENT IE LORH R
M5XR
STATE
OK
OK
CD
OK
CD
OK
OK
CD
CD
CD
CD F-HPI
IR 50-529/04-09
Figure A-LOI-M5XR C
LONG-TERM RECIRC G
GRAVITY FEED B
BLEED (SPILL)
F FORCED FEED S
SECONDARY (REFLUX)
COOLING V
RCS VENTED R
RHR RECOVERY LOI-NT Loss of Inventory Terminated M
RCS Inventory Make-UP D
OPERATOR DIAGNOS ES EVENT IE LOI M5XR
STATE
OK
OK
CD
OK
OK
CD
CD
CD
OK
CD
OK
CD
CD
CD F-HPI
IR 50-529/04-09
Figure A-LOIRI-M5XR C
LONG-TERM RECIRC G
GRAVITY FEED B
BLEED (SPILL)
F FORCED FEED S
SECONDARY (REFLUX)
COOLING V
RCS VENTED R
RHR RECOVERY M
RCS INVENTOR Y
MAKE-UP D
OPERATOR DIAGNOSE S
EVENT IE LOIR I
M5XR
STATE
OK
OK
CD
OK
OK
CD
CD
CD
OK
CD
CD
CD F-HPI Vented Not Vented
IR 50-529/04-09
C LONG-TERM RECIRC G
GRAVITY FEED B
BLEED (SPILL)
F FORCED FEED S
SECONDARY (REFLUX)
COOLING N
OFFSITE POWER RECOVERY V
RCS VENTED R
RHR RECOVERY EPS-LPSD Loss of EMERGENC Y
AC POWER D
OPERATOR DIAGNOS S E
STATE
OK
OK
CD
OK
CD
OK
CD
OK
CD
OK
OK
CD
CD
CD
OK
OK
CD
CD
CD
OK
CD
OK
CD
OK
CD
OK
OK
CD
CD
CD
CD
CD F-L C-L F-HPI S-L F-HPI-L B-L C-L F-HPI N-L N-L Figure A-LOOP-M5XR