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{{#Wiki_filter:September 24, 2003 NOTE TO:       Stuart Richards, Chief Inspection Program Branch Division of Inspection Program Management Office of Nuclear Reactor Regulation Patrick D. OReilly Operating Experience Risk Applications Branch Division of Risk Analysis and Applications Office of Nuclear Regulatory Research FROM:           Mark F. Reinhart, Chief       /RA/ M. Caruso for Licensing Section Probabilistic Safety Assessment Branch Division of Systems Safety and Analysis Office of Nuclear Reactor Regulation
{{#Wiki_filter:September 24, 2003 NOTE TO:
Stuart Richards, Chief Inspection Program Branch Division of Inspection Program Management Office of Nuclear Reactor Regulation Patrick D. OReilly Operating Experience Risk Applications Branch Division of Risk Analysis and Applications Office of Nuclear Regulatory Research FROM:
Mark F. Reinhart, Chief
/RA/ M. Caruso for Licensing Section Probabilistic Safety Assessment Branch Division of Systems Safety and Analysis Office of Nuclear Reactor Regulation


==SUBJECT:==
==SUBJECT:==
Line 23: Line 26:
CONTACT: Peter Wilson, SPSB/DSSA/NRR 301-415-1114
CONTACT: Peter Wilson, SPSB/DSSA/NRR 301-415-1114


S. Richards                                   2 P. OReilly 2% (1 of 47 cases)         Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)         Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)       Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)       Consistent risk significance.
S. Richards 2
P. OReilly 2% (1 of 47 cases)
Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)
Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)
Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)
Consistent risk significance.
The Rev-1 SDP notebook has been significantly improved as a result of the benchmarking activity. The number of cases that the Rev-1 SDP would match that of the updated licensees PRA has increased from 23 to 33. The number of overestimations by two orders of magnitude decreased from 5 to 1. In addition, the number of underestimations decreased from 8 to 1.
The Rev-1 SDP notebook has been significantly improved as a result of the benchmarking activity. The number of cases that the Rev-1 SDP would match that of the updated licensees PRA has increased from 23 to 33. The number of overestimations by two orders of magnitude decreased from 5 to 1. In addition, the number of underestimations decreased from 8 to 1.
However, the number of overestimations by one order of magnitude increased slightly from 11 to 12.
However, the number of overestimations by one order of magnitude increased slightly from 11 to 12.
The licensees PRA staff was very knowledgeable of the plant model and provided very helpful comments during the benchmark visit.
The licensees PRA staff was very knowledgeable of the plant model and provided very helpful comments during the benchmark visit.
Attachment A describes the process and results of the comparison of the Beaver Valley Unit 2 SDP Phase 2 Notebook and the licensees PRA.
Attachment A describes the process and results of the comparison of the Beaver Valley Unit 2 SDP Phase 2 Notebook and the licensees PRA.
Attachments: As stated CONTACT:       Peter Wilson, SPSB/DSSA/NRR 301-415-1114
Attachments: As stated CONTACT:
Peter Wilson, SPSB/DSSA/NRR 301-415-1114


S. Richards                                     2 P. OReilly 2% (1 of 47 cases)         Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)         Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)       Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)       Consistent risk significance.
S. Richards 2
P. OReilly 2% (1 of 47 cases)
Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)
Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)
Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)
Consistent risk significance.
The Rev-1 SDP notebook has been significantly improved as a result of the benchmarking activity. The number of cases that the Rev-1 SDP would match that of the updated licensees PRA has increased from 23 to 33. The number of overestimations by two orders of magnitude decreased from 5 to 1. In addition, the number of underestimations decreased from 8 to 1.
The Rev-1 SDP notebook has been significantly improved as a result of the benchmarking activity. The number of cases that the Rev-1 SDP would match that of the updated licensees PRA has increased from 23 to 33. The number of overestimations by two orders of magnitude decreased from 5 to 1. In addition, the number of underestimations decreased from 8 to 1.
However, the number of overestimations by one order of magnitude increased slightly from 11 to 12.
However, the number of overestimations by one order of magnitude increased slightly from 11 to 12.
The licensees PRA staff was very knowledgeable of the plant model and provided very helpful comments during the benchmark visit.
The licensees PRA staff was very knowledgeable of the plant model and provided very helpful comments during the benchmark visit.
Attachment A describes the process and results of the comparison of the Beaver Valley Unit 2 SDP Phase 2 Notebook and the licensees PRA.
Attachment A describes the process and results of the comparison of the Beaver Valley Unit 2 SDP Phase 2 Notebook and the licensees PRA.
Attachments: As stated DISTRIBUTION: SPSB:r/f         W. Schmidt Accession#ML032681044 G:\wilson\Pilgrimbench.wpd                             NRR-096 OFFICE     SPSB             SPSB:SC                     SPSB:RII NAME     PWilson:nxh2     MReinhart /RA/ M. Caruso for WSchmidt DATE     09/24/03         09/24/03                     09/24/03 OFFICIAL RECORD COPY
Attachments: As stated DISTRIBUTION: SPSB:r/f W. Schmidt Accession#ML032681044 G:\\wilson\\Pilgrimbench.wpd NRR-096 OFFICE SPSB SPSB:SC SPSB:RII NAME PWilson:nxh2 MReinhart /RA/ M. Caruso for WSchmidt DATE 09/24/03 09/24/03 09/24/03 OFFICIAL RECORD COPY
 
ATTACHMENT A


==SUMMARY==
==SUMMARY==
REPORT ON BENCHMARKING TRIP TO THE BEAVER VALLEY POWER STATION UNIT 2 Pranab K. Samanta Energy Sciences and Technology Department Brookhaven National Laboratory Upton, NY 11973-5000 September 2003 ATTACHMENT A
REPORT ON BENCHMARKING TRIP TO THE BEAVER VALLEY POWER STATION UNIT 2 Pranab K. Samanta Energy Sciences and Technology Department Brookhaven National Laboratory Upton, NY 11973-5000 September 2003
 
ATTACHMENT A
-v-Table of Contents Page Introduction............................................................... 1 Summary Results from Benchmarking.......................................... 2 Proposed Modifications to the Rev. 0 SDP Notebook............................... 8 3.1 Specific Changes to the Rev. 0 SDP Notebook for the Beaver Valley Power Station, Unit 2.................................. 8 3.2 Generic Change in 0609 for Inspectors...............................
10 3.3 Generic Change to the SDP Notebook...............................
10 Discussion on External Events................................................ 11 List of Participants.......................................................... 15 List of Tables Page Table 1.
Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2......................................................... 4 Table 2.
Comparative Summary of Benchmarking Results........................ 7 Table 3.
Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2......................................................... 12


Table of Contents Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Summary Results from Benchmarking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Proposed Modifications to the Rev. 0 SDP Notebook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1      Specific Changes to the Rev. 0 SDP Notebook for the Beaver Valley Power Station, Unit 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2      Generic Change in 0609 for Inspectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3      Generic Change to the SDP Notebook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Discussion on External Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 List of Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 List of Tables Page Table 1.      Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Table 2.      Comparative Summary of Benchmarking Results . . . . . . . . . . . . . . . . . . . . . . . . 7 Table 3.      Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 ATTACHMENT A                                                     -v-
ATTACHMENT A 1. INTRODUCTION A benchmarking of the Risk-Informed Inspection Notebook for the Beaver Valley Power Station, Unit 2, to be referred to as BV-2, was conducted during a plant site visit on July 28-August 2, 2003. NRC staff (P. Wilson and W. Schmidt) and BNL staff (P. Samanta) participated in this Benchmarking exercise.
: 1. INTRODUCTION A benchmarking of the Risk-Informed Inspection Notebook for the Beaver Valley Power Station, Unit 2, to be referred to as BV-2, was conducted during a plant site visit on July 28-August 2, 2003. NRC staff (P. Wilson and W. Schmidt) and BNL staff (P. Samanta) participated in this Benchmarking exercise.
In preparation for the meeting, BNL staff reviewed the SDP notebook for the Beaver Valley Power Station and evaluated a set of hypothetical inspection findings using the Rev. 0 SDP worksheets. In addition, NRC staff provided the licensee with a copy of the meeting protocol.
In preparation for the meeting, BNL staff reviewed the SDP notebook for the Beaver Valley Power Station and evaluated a set of hypothetical inspection findings using the Rev. 0 SDP worksheets. In addition, NRC staff provided the licensee with a copy of the meeting protocol.
The major milestones achieved during this meeting were as follows:
The major milestones achieved during this meeting were as follows:
: 1.     Recent modifications made to the BV-2 PRA were discussed for consideration in the Rev. 1 model to be prepared following benchmarking.
1.
: 2.     Importance measures, including the Risk Achievement Worths (RAWs) for the basic events in the internal events model for average maintenance, were obtained from the licensee.
Recent modifications made to the BV-2 PRA were discussed for consideration in the Rev. 1 model to be prepared following benchmarking.
: 3.     Benchmarking was conducted using the Rev. 0 SDP model and the revised SDP model considering the licensees input and other modifications that were judged necessary based on comparison of the SDP model and the licensees detailed model.
2.
: 4.     For cases where the color evaluated by the SDP notebook differed from that determined based on the RAW values generated by the updated licensees PRA, results of the licensees base case model including the dominant minimal cutsets were reviewed to understand the reason for the differences.
Importance measures, including the Risk Achievement Worths (RAWs) for the basic events in the internal events model for average maintenance, were obtained from the licensee.
3.
Benchmarking was conducted using the Rev. 0 SDP model and the revised SDP model considering the licensees input and other modifications that were judged necessary based on comparison of the SDP model and the licensees detailed model.
4.
For cases where the color evaluated by the SDP notebook differed from that determined based on the RAW values generated by the updated licensees PRA, results of the licensees base case model including the dominant minimal cutsets were reviewed to understand the reason for the differences.
The Rev. 1 version of the SDP notebook was developed considering the changes identified based on the licensees input and the evaluation of the benchmarking results.
The Rev. 1 version of the SDP notebook was developed considering the changes identified based on the licensees input and the evaluation of the benchmarking results.
ATTACHMENT A
 
: 2.  
ATTACHMENT A 2.  


==SUMMARY==
==SUMMARY==
RESULTS FROM BENCHMARKING Summary of Benchmarking Results Benchmarking of the SDP Notebook for the Beaver Valley Power Station, Unit 2 was conducted comparing the risk significance of the inspection findings obtained using the notebook with that obtained using the plant PRA. The benchmarking identified the hypothetical inspection findings for which the results of the evaluation using the notebook were under or overestimations compared to the plant PRA. One case of a non-conservative result or underestimation by the notebook (i.e., the significance obtained using the notebook was one color lower than that obtained by the plant PRA) was noted. Also, one case of a conservative result by two orders of magnitude (i.e., the significance obtained using the notebook was two colors higher than that to be obtained using the plant PRA) was noted. A summary of the results of the risk characterization of hypothetical inspection findings is as follows:
RESULTS FROM BENCHMARKING Summary of Benchmarking Results Benchmarking of the SDP Notebook for the Beaver Valley Power Station, Unit 2 was conducted comparing the risk significance of the inspection findings obtained using the notebook with that obtained using the plant PRA. The benchmarking identified the hypothetical inspection findings for which the results of the evaluation using the notebook were under or overestimations compared to the plant PRA. One case of a non-conservative result or underestimation by the notebook (i.e., the significance obtained using the notebook was one color lower than that obtained by the plant PRA) was noted. Also, one case of a conservative result by two orders of magnitude (i.e., the significance obtained using the notebook was two colors higher than that to be obtained using the plant PRA) was noted. A summary of the results of the risk characterization of hypothetical inspection findings is as follows:
2% (1 of 47 cases)           Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)           Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)         Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)         Consistent risk significance.
2% (1 of 47 cases)
Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)
Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)
Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)
Consistent risk significance.
Detailed results of benchmarking are summarized in Table 1. Table 1 consists of eight columns. The first two columns identify the components or the case runs. The assigned colors from the SDP Rev. 0 worksheets without incorporating any modification from the Benchmarking exercise are shown in the third column. The fourth column gives the basic event name in the plant PRA used to obtain the risk achievement worth (RAW) for the component out of service or the failed operator action. The fifth and sixth columns respectively show the licensees internal RAW value and the color to be defined based on the RAW values from the latest PRA model.
Detailed results of benchmarking are summarized in Table 1. Table 1 consists of eight columns. The first two columns identify the components or the case runs. The assigned colors from the SDP Rev. 0 worksheets without incorporating any modification from the Benchmarking exercise are shown in the third column. The fourth column gives the basic event name in the plant PRA used to obtain the risk achievement worth (RAW) for the component out of service or the failed operator action. The fifth and sixth columns respectively show the licensees internal RAW value and the color to be defined based on the RAW values from the latest PRA model.
The seventh column presents the colors for the inspection findings based on the Rev. 1 version of the notebook. The Rev. 1 version of the notebook was prepared considering the revisions to the Rev. 0 version of the SDP notebook judged applicable during Benchmarking. The last column provides comments identifying the difference in results between the SDP Rev. 1 notebook and the plant PRA, and the applicable rules in obtaining the color of the inspection finding using the SDP notebook.
The seventh column presents the colors for the inspection findings based on the Rev. 1 version of the notebook. The Rev. 1 version of the notebook was prepared considering the revisions to the Rev. 0 version of the SDP notebook judged applicable during Benchmarking. The last column provides comments identifying the difference in results between the SDP Rev. 1 notebook and the plant PRA, and the applicable rules in obtaining the color of the inspection finding using the SDP notebook.
Table 2 presents a summary of the comparison between the results obtained using the Beaver Valley Power Station, Unit 2 notebook and the plant PRA. It also shows a comparison of the results using the Rev. 0 and Rev. 1 versions of the notebook. The results show that both underestimations and overestimations by the notebook were reduced and, consequently, matches were increased through revisions to the notebook implemented as a result of Benchmarking. The overestimations were reduced from 34% to 28%, the underestimations were reduced from 17% to 2%, and the matches increased from 49% to 70%.
Table 2 presents a summary of the comparison between the results obtained using the Beaver Valley Power Station, Unit 2 notebook and the plant PRA. It also shows a comparison of the results using the Rev. 0 and Rev. 1 versions of the notebook. The results show that both underestimations and overestimations by the notebook were reduced and, consequently, matches were increased through revisions to the notebook implemented as a result of Benchmarking. The overestimations were reduced from 34% to 28%, the underestimations were reduced from 17% to 2%, and the matches increased from 49% to 70%.
ATTACHMENT A Discussion of Non-conservative Results by the Notebook During benchmarking, non-conservative results or underestimation by the notebook compared to the plant PRA were noted for 1 out of the 48 cases analyzed. The reason for the difference, as identified, is discussed below.
ATTACHMENT A Discussion of Non-conservative Results by the Notebook During benchmarking, non-conservative results or underestimation by the notebook compared to the plant PRA were noted for 1 out of the 48 cases analyzed. The reason for the difference, as identified, is discussed below.
: 1. Operator failure to recover MFW following transient or SLOCA was underestimated by one order by the notebook. The reason for the underestimation was the difference in failure probability for the AFW system in the PRA versus the mitigation credit for AFW in the notebook. In the plant PRA, failure of AFW system was modeled due to common cause failure of the check valves resulting in back flow with a probability of approximately 1E-3. In the notebook, the credit for the AFW system was 4 (3 for the motor-driven pumps and 1 for the turbine-driven pump). This difference was the reason for the underestimation. The notebook did not model the common cause failure of the check valves leading to failure of the AFW pumps.
: 1. Operator failure to recover MFW following transient or SLOCA was underestimated by one order by the notebook. The reason for the underestimation was the difference in failure probability for the AFW system in the PRA versus the mitigation credit for AFW in the notebook. In the plant PRA, failure of AFW system was modeled due to common cause failure of the check valves resulting in back flow with a probability of approximately 1E-3. In the notebook, the credit for the AFW system was 4 (3 for the motor-driven pumps and 1 for the turbine-driven pump). This difference was the reason for the underestimation. The notebook did not model the common cause failure of the check valves leading to failure of the AFW pumps.
Line 65: Line 97:
: 1. Failure of 1 SG ASDV was overestimated by two orders of magnitude, i.e., by two colors. SG ASDVs provide steam relief for the secondary and are used for RCS depressurization. In all cases when SG ASDVs were used, multiple redundancies were available. In the PRA calculation, the loss of 1 SG ASDV has a minimal impact. However, in the notebook evaluation, many sequences were counted considering the base case impact leading to the overestimation by two orders of magnitude.
: 1. Failure of 1 SG ASDV was overestimated by two orders of magnitude, i.e., by two colors. SG ASDVs provide steam relief for the secondary and are used for RCS depressurization. In all cases when SG ASDVs were used, multiple redundancies were available. In the PRA calculation, the loss of 1 SG ASDV has a minimal impact. However, in the notebook evaluation, many sequences were counted considering the base case impact leading to the overestimation by two orders of magnitude.
Changes Incorporated Following Benchmarking Resulting in Updating of Benchmarking Results No change was made following benchmarking that resulted in changes to the benchmarking results.
Changes Incorporated Following Benchmarking Resulting in Updating of Benchmarking Results No change was made following benchmarking that resulted in changes to the benchmarking results.
ATTACHMENT A Table 1. Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 Internal Events CDF = 1.85E-5, excluding internal flooding, at Truncation Level of 1E-10 RAW Thresholds are: W = 1.054, Y = 1.54, R = 6.4, RR = 55. , RRR = 541.5 No. Component Out     SDP     Basic Event Name     RAW       Plant CDF     SDP             Comments of Service or    Before                                      Color        After Failed Operator Action Component
Table 1. Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 Internal Events CDF = 1.85E-5, excluding internal flooding, at Truncation Level of 1E-10 RAW Thresholds are: W = 1.054, Y = 1.54, R = 6.4, RR = 55., RRR = 541.5 No.
: 1. 1 MDAFW pump       R         2FWE-P23A           7.71         R           R A
Component Out of Service or Failed Operator Action SDP Before Basic Event Name RAW Plant CDF Color SDP After Comments Component 1.
: 2. MDAFW pump B       R         2FWE-P23B           1.47         W           Y       over by 1
1 MDAFW pump A
: 3. 1 TDAFW pump       Y         2FWE-P22           2.7         Y           Y
R 2FWE-P23A 7.71 R
: 4. 1 Accumulator       R         2SIS-TK21A         3.45         Y           R       over by 1
R 2.
: 5. 1 Cond. pump       G         Not modeled         1.0         G           G       RAW is assumed to be                                                                                             same as the MFW pump.
MDAFW pump B R
: 6. 1 MFW pump         G         2FWS-P21A           1.0         G           G
2FWE-P23B 1.47 W
: 7. 1 PORV FTO         W           Case run         1.21         W           W
Y over by 1 3.
: 8. 1 PORV FTC         Y       2RCS-PCV455D         1.3         W           W
1 TDAFW pump Y
: 9. 1 RHR pump         G         2RHS-P21A           1.0         G           G
2FWE-P22 2.7 Y
: 10. HHSI pump A         Y         2CHS-P21A         1.25         W           Y       over by 1
Y 4.
: 11. Spare HHSI pump     W         2CHS-P21C         1.34         W           W
1 Accumulator R
: 12. 1 BAT pump         G         Not Modeled                                   G       Comparable RAW not available
2SIS-TK21A 3.45 Y
: 13. 1 LHSI pump         W         2SIS-P21B         1.07         W           W
R over by 1 5.
: 14. QS pump A           G         2QSS-P21A           1.96         Y           Y
1 Cond. pump G
: 15. QS Pump B           G         2QSS-P21B           1.17         W           W
Not modeled 1.0 G
: 16. RS pump C           R         2RSS-P21C           1.95         Y           Y
G RAW is assumed to be same as the MFW pump.
: 17. RS pump D           R         2RRS-P21D           1.32         W           W
6.
: 18. RS HX C             R         2RSS-E21C           1.9         Y           Y
1 MFW pump G
: 19. RS HX D             R         2RSS-E21D           1.28         W           W
2FWS-P21A 1.0 G
: 20. 1 CCP pump         Y         2CCP-P21B           1.04         G           G
G 7.
1 PORV FTO W
Case run 1.21 W
W 8.
1 PORV FTC Y
2RCS-PCV455D 1.3 W
W 9.
1 RHR pump G
2RHS-P21A 1.0 G
G 10.
HHSI pump A Y
2CHS-P21A 1.25 W
Y over by 1 11.
Spare HHSI pump W
2CHS-P21C 1.34 W
W 12.
1 BAT pump G
Not Modeled G
Comparable RAW not available 13.
1 LHSI pump W
2SIS-P21B 1.07 W
W 14.
QS pump A G
2QSS-P21A 1.96 Y
Y 15.
QS Pump B G
2QSS-P21B 1.17 W
W 16.
RS pump C R
2RSS-P21C 1.95 Y
Y 17.
RS pump D R
2RRS-P21D 1.32 W
W 18.
RS HX C R
2RSS-E21C 1.9 Y
Y 19.
RS HX D R
2RSS-E21D 1.28 W
W 20.
1 CCP pump Y
2CCP-P21B 1.04 G
G


No. Component Out         SDP     Basic Event Name   RAW     Plant CDF   SDP             Comments of Service or      Before                                Color    After Failed Operator Action
No.
: 21. SW Pump A             R         2SWS-P21B         1.62       Y         Y
Component Out of Service or Failed Operator Action SDP Before Basic Event Name RAW Plant CDF Color SDP After Comments 21.
: 22. SW pump B             R         2SWS-P21B         1.87       Y         Y
SW Pump A R
: 23. AC Orange Bus         RRR         4KVS-2AE       1013.8     RRR       RRR
2SWS-P21B 1.62 Y
: 24. AC Purple Bus         RRR         4KVS-2DF       1021.1     RRR       RRR
Y 22.
: 25. 1 EDG                 Y         2EGS-EG2-1       3.37       Y         Y
SW pump B R
: 26. ERF DG (Black)         G         1RG-EG-1         1.0       G         G     Always Green
2SWS-P21B 1.87 Y
: 27. DC Orange Bus         RRR       DC-SWBD2-1         277       RR       RRR     over by 1
Y 23.
: 28. DC Purple Bus         RRR       DC-SWBD2-2         161.     RR       RRR     over by 1
AC Orange Bus RRR 4KVS-2AE 1013.8 RRR RRR 24.
: 29. Battery 2-1           Y           BAT-2-1         4.07       Y         Y
AC Purple Bus RRR 4KVS-2DF 1021.1 RRR RRR 25.
: 30. Battery 2-2           Y           BAT-2-2         1.15       W         Y     over by 1
1 EDG Y
: 31. Battery Charger 1     R         BAT-CHG2-1       277.73     RR       RRR     over by 1
2EGS-EG2-1 3.37 Y
: 32. Battery Charger 2     R         BAT-CHG2-2       161.     RR       RRR     over by 1
Y 26.
: 33. 1 EDG Exhaust         Y       2HVD-FN270A         1.0       G         W     over by 1         fan
ERF DG (Black)
: 34. 1 Containment IA       G         2IAC-C21A       1.0       G         G     Always Green compressor
G 1RG-EG-1 1.0 G
: 35. 1 Station Air           G         2SAS-C21A       1.0       G         G     Always Green Compressor
G Always Green 27.
: 36. 1 MSIV                 Y       2MSS-AOV101A       1.62       Y         Y
DC Orange Bus RRR DC-SWBD2-1 277 RR RRR over by 1 28.
: 37. 1 SCCW Pump             G         2CCS-P21A         1.0       G         G     Always Green
DC Purple Bus RRR DC-SWBD2-2 161.
: 38. 1 SG HRV               W       2SVS-HCV104       1.12       W         Y     over by 1
RR RRR over by 1 29.
: 39. 1 SG ASDV               W       2SVS-PCV101A       1.04       G         Y     over by 2 Operator Actions
Battery 2-1 Y
: 40. Op fails to recover     G         OPROF2         5.11       Y         W     under MFW
BAT-2-1 4.07 Y
: 41. Fails to FB             R         OPROB1         28.69       R         R
Y 30.
: 42. Fails to DEP in         W         case run       1.001       G         G SLOCA
Battery 2-2 Y
BAT-2-2 1.15 W
Y over by 1 31.
Battery Charger 1 R
BAT-CHG2-1 277.73 RR RRR over by 1 32.
Battery Charger 2 R
BAT-CHG2-2 161.
RR RRR over by 1 33.
1 EDG Exhaust fan Y
2HVD-FN270A 1.0 G
W over by 1 34.
1 Containment IA compressor G
2IAC-C21A 1.0 G
G Always Green 35.
1 Station Air Compressor G
2SAS-C21A 1.0 G
G Always Green 36.
1 MSIV Y
2MSS-AOV101A 1.62 Y
Y 37.
1 SCCW Pump G
2CCS-P21A 1.0 G
G Always Green 38.
1 SG HRV W
2SVS-HCV104 1.12 W
Y over by 1 39.
1 SG ASDV W
2SVS-PCV101A 1.04 G
Y over by 2 Operator Actions 40.
Op fails to recover MFW G
OPROF2 5.11 Y
W under 41.
Fails to FB R
OPROB1 28.69 R
R 42.
Fails to DEP in SLOCA W
case run 1.001 G
G


No. Component Out       SDP     Basic Event Name   RAW   Plant CDF   SDP           Comments of Service or    Before                              Color    After Failed Operator Action
No.
: 43. RAPDEP in             W         OPRCD1         1.06     W         W SLOCA
Component Out of Service or Failed Operator Action SDP Before Basic Event Name RAW Plant CDF Color SDP After Comments 43.
: 44. Fails to close the     W         OPRPI1         1.0       G         G Block valve
RAPDEP in SLOCA W
: 45. EQ and isolation       R         OPRSL1         2.86     Y         Y in a SGTR
OPRCD1 1.06 W
: 46. RWST makeup           W         Case run       1.27     W         Y     over by 1
W 44.
: 47. Fails to initiate     W         OPRRR1         1.02     G         W     over by 1 RHR
Fails to close the Block valve W
: 48. Emergency             W         OPROA1         1.36     W         W Boration Table 2: Comparative Summary of Benchmarking Results Comparisons               Rev. 0 SDP Notebook                 Following Benchmarking, Rev. 1 Notebook Total Number of Cases = 48 Number of Cases       Percentage         Number of         Percentage Cases SDP: Less                     8 (1)               17               1 (2)               2 Conservative SDP:         one               11                 23               12               26 More        order Conserv ative        two               5                 11                 1                 2 orders SDP: Matched                   23                 49               33               70 Comparable RAW                 1                                    1 not available or not modeled in the Notebook Notes:
OPRPI1 1.0 G
: 1. 2 cases by two orders of magnitude and the remaining 6 cases by one order of magnitude.
G 45.
: 2. By one order of magnitude.
EQ and isolation in a SGTR R
ATTACHMENT A
OPRSL1 2.86 Y
: 3. PROPOSED MODIFICATIONS TO THE REV. 0 SDP NOTEBOOK A set of modifications were proposed for the Rev. 0 SDP notebook as a result of the site visit.
Y 46.
RWST makeup W
Case run 1.27 W
Y over by 1 47.
Fails to initiate RHR W
OPRRR1 1.02 G
W over by 1 48.
Emergency Boration W
OPROA1 1.36 W
W
 
ATTACHMENT A Table 2: Comparative Summary of Benchmarking Results Comparisons Rev. 0 SDP Notebook Following Benchmarking, Rev. 1 Notebook Total Number of Cases = 48 Number of Cases Percentage Number of Cases Percentage SDP: Less Conservative 8 (1) 17 1 (2) 2 SDP:
More Conserv ative one order 11 23 12 26 two orders 5
11 1
2 SDP: Matched 23 49 33 70 Comparable RAW not available or not modeled in the Notebook 1
1 Notes:
: 1.
2 cases by two orders of magnitude and the remaining 6 cases by one order of magnitude.
2.
By one order of magnitude.
 
ATTACHMENT A 3. PROPOSED MODIFICATIONS TO THE REV. 0 SDP NOTEBOOK A set of modifications were proposed for the Rev. 0 SDP notebook as a result of the site visit.
These proposed modifications are driven by the licensees revisions to the plants PRA, better understanding of the current plant design features, revised Human Error Probabilities (HEPs),
These proposed modifications are driven by the licensees revisions to the plants PRA, better understanding of the current plant design features, revised Human Error Probabilities (HEPs),
modified initiator frequencies, and the results of benchmarking.
modified initiator frequencies, and the results of benchmarking.
3.1   Specific Changes to the Rev. 0 SDP Notebook for the Beaver Valley Power Station, Unit 2 The following changes were made based on the licensees inputs and evaluations conducted as part of Benchmarking:
3.1 Specific Changes to the Rev. 0 SDP Notebook for the Beaver Valley Power Station, Unit 2 The following changes were made based on the licensees inputs and evaluations conducted as part of Benchmarking:
: 1. Changes to Table 1 1.1     Loss of a 4 kV EAC Bus (LAC) was replaced by two separate initiators, Loss of a 4 kV Orange Bus (LACO) and Loss of 4 kV Purple Bus (LACP). Both initiators were placed in Row II.
1.
1.2     Loss of a DC Bus (LDC) was replaced by two separate initiators, Loss of a DC Orange Bus (LDCO) and Loss of a DC Purple Bus (LDCP). Both initiators were placed in Row II.
Changes to Table 1 1.1 Loss of a 4 kV EAC Bus (LAC) was replaced by two separate initiators, Loss of a 4 kV Orange Bus (LACO) and Loss of 4 kV Purple Bus (LACP). Both initiators were placed in Row II.
1.3     Loss of Service Water Header A or B (LOSWH) was replaced by two separate initiators, Loss of Service Water Header A (LOSWHA) and Loss of Service Water Header B (LOSWHB). Both initiators were placed in Row III.
1.2 Loss of a DC Bus (LDC) was replaced by two separate initiators, Loss of a DC Orange Bus (LDCO) and Loss of a DC Purple Bus (LDCP). Both initiators were placed in Row II.
1.4     Loss of Primary Component Cooling Water (LCCP) was added in Row II.
1.3 Loss of Service Water Header A or B (LOSWH) was replaced by two separate initiators, Loss of Service Water Header A (LOSWHA) and Loss of Service Water Header B (LOSWHB). Both initiators were placed in Row III.
: 2. Changes to Table 2 2.1     DC dependency of MFW and condensate pumps was clarified. Startup feed pump was added as a major component. ERF DG was removed as a support system, but a footnote was added stating that the ERF diesel serves as the backup power source for the startup feed pump.
1.4 Loss of Primary Component Cooling Water (LCCP) was added in Row II.
2.2     CIA and SSPS dependency for MSIV were removed. MSIV was included as part of Main Steam.
2.
2.3     SW Header B as the backup water supply for the AFW system was noted in the footnote and removed from the Support System column.
Changes to Table 2 2.1 DC dependency of MFW and condensate pumps was clarified. Startup feed pump was added as a major component. ERF DG was removed as a support system, but a footnote was added stating that the ERF diesel serves as the backup power source for the startup feed pump.
ATTACHMENT A 2.4   125V DC dependency for TD AFW pump was removed. A footnote was added to note that the SOVs on the steam admission line fail open on loss of power.
2.2 CIA and SSPS dependency for MSIV were removed. MSIV was included as part of Main Steam.
2.5   125V DC dependency for EAC Buses was added.
2.3 SW Header B as the backup water supply for the AFW system was noted in the footnote and removed from the Support System column.
2.6   A footnote for the ERF diesel was added to note the separate battery for start and control power.
 
2.7   480V EAC dependency for the 125V DC system was noted.
ATTACHMENT A 2.4 125V DC dependency for TD AFW pump was removed. A footnote was added to note that the SOVs on the steam admission line fail open on loss of power.
2.8   SSPS dependency on Vital Bus Channels was clarified. Channels I and II are needed, not channels III and IV.
2.5 125V DC dependency for EAC Buses was added.
2.9   Major components for Ventilation System was corrected to include only fans.
2.6 A footnote for the ERF diesel was added to note the separate battery for start and control power.
2.7 480V EAC dependency for the 125V DC system was noted.
2.8 SSPS dependency on Vital Bus Channels was clarified. Channels I and II are needed, not channels III and IV.
2.9 Major components for Ventilation System was corrected to include only fans.
Dependency on Vital Bus Channels I and II was deleted.
Dependency on Vital Bus Channels I and II was deleted.
2.10 For the SW system, it was noted in the footnote that ventilation is needed only for starting the standby pumps.
2.10 For the SW system, it was noted in the footnote that ventilation is needed only for starting the standby pumps.
2.11 For the IA/CIA system, a footnote was added to note that ERF diesel provides a backup power supply in case of loss of power.
2.11 For the IA/CIA system, a footnote was added to note that ERF diesel provides a backup power supply in case of loss of power.
2.12 The Chilled Water system was deleted.
2.12 The Chilled Water system was deleted.
: 3. Changes to Worksheets and Event Trees 3.1   RWST makeup in case of failure of HPR and LPR was added, as applicable, for different initiators.
: 3.
3.2   For the HPR and LPR functions in different transient and SLOCA scenarios, success of 1/2 QS pumps is needed and is included as part of the mitigation capability. For MLOCA and LLOCA, success for a QS pump is not required.
Changes to Worksheets and Event Trees 3.1 RWST makeup in case of failure of HPR and LPR was added, as applicable, for different initiators.
3.3   In SLOCA worksheet, use of the Heat Release valve was credited in the RAPDEP function and the operator action credit was reduced to 1 (from 2).
3.2 For the HPR and LPR functions in different transient and SLOCA scenarios, success of 1/2 QS pumps is needed and is included as part of the mitigation capability. For MLOCA and LLOCA, success for a QS pump is not required.
3.4   SLOCA worksheet and event tree were modified to credit FW consistently following loss of AFW.
3.3 In SLOCA worksheet, use of the Heat Release valve was credited in the RAPDEP function and the operator action credit was reduced to 1 (from 2).
3.5   SORV worksheet and event tree were modified similar to SLOCA worksheet and event tree.
3.4 SLOCA worksheet and event tree were modified to credit FW consistently following loss of AFW.
ATTACHMENT A 3.6     LLOCA worksheet and event tree were modified to remove the need for QS for LPR.
3.5 SORV worksheet and event tree were modified similar to SLOCA worksheet and event tree.
3.7     LOOP worksheet and event tree were modified to address the capability to crosstie other units EDG to power a charging pump. For this, Crosstieing other units EDG is separated from the EAC function. RWST makeup is only credited when offsite power is recovered.
 
3.8     SGTR worksheet and event tree were modified to remove the need for EQ following FB and to address RWST makeup.
ATTACHMENT A 3.6 LLOCA worksheet and event tree were modified to remove the need for QS for LPR.
3.9     In the ATWS worksheet, steam relief requirement for AFW was added. Also, RWST suction, in case of failure of the BAT pumps, was included.
3.7 LOOP worksheet and event tree were modified to address the capability to crosstie other units EDG to power a charging pump. For this, Crosstieing other units EDG is separated from the EAC function. RWST makeup is only credited when offsite power is recovered.
3.10     Separate worksheets and event trees were included for Loss of Service Water Headers A and B. For loss of Service Water Header B, RWST makeup is not possible.
3.8 SGTR worksheet and event tree were modified to remove the need for EQ following FB and to address RWST makeup.
3.11     LEAC worksheet was modified to include manual operation of ASDVs and to modify the credit for RAPDEP to operator action = 1.
3.9 In the ATWS worksheet, steam relief requirement for AFW was added. Also, RWST suction, in case of failure of the BAT pumps, was included.
3.12     Separate worksheets and event trees were developed for Loss of Orange and Purple EAC Buses. In the Loss of the Orange Bus (LACO), credit for using feedwater was changed to operator action = 2 based on the plant-specific HEP.
3.10 Separate worksheets and event trees were included for Loss of Service Water Headers A and B. For loss of Service Water Header B, RWST makeup is not possible.
3.11 LEAC worksheet was modified to include manual operation of ASDVs and to modify the credit for RAPDEP to operator action = 1.
3.12 Separate worksheets and event trees were developed for Loss of Orange and Purple EAC Buses. In the Loss of the Orange Bus (LACO), credit for using feedwater was changed to operator action = 2 based on the plant-specific HEP.
Loss of the Purple Bus (LACP) results in loss of the feed pumps and the ability to use RWST makeup.
Loss of the Purple Bus (LACP) results in loss of the feed pumps and the ability to use RWST makeup.
3.13     Similar to loss of AC Buses, separate worksheets and event trees were developed for loss of orange and purple DC Buses.
3.13 Similar to loss of AC Buses, separate worksheets and event trees were developed for loss of orange and purple DC Buses.
3.14     The worksheet and event tree were developed for Loss of Primary Component Cooling water (LCCP).
3.14 The worksheet and event tree were developed for Loss of Primary Component Cooling water (LCCP).
3.2 Generic Change in 0609 for Inspectors None identified.
3.2 Generic Change in 0609 for Inspectors None identified.
3.3 Generic Change to the SDP Notebook None identified.
3.3 Generic Change to the SDP Notebook None identified.
ATTACHMENT A
 
: 4. DISCUSSION ON EXTERNAL EVENTS The Beaver Valley Power Station, Unit 2 integrated PRA model includes internal floods, internal fire, and seismic initiators. The CDF in the integrated model including these external initiators was 3.33E-5/reactor-yr. The integrated model was used to assess whether the inclusion of the external initiators will result in increased risk significance for components or operator actions.
ATTACHMENT A 4. DISCUSSION ON EXTERNAL EVENTS The Beaver Valley Power Station, Unit 2 integrated PRA model includes internal floods, internal fire, and seismic initiators. The CDF in the integrated model including these external initiators was 3.33E-5/reactor-yr. The integrated model was used to assess whether the inclusion of the external initiators will result in increased risk significance for components or operator actions.
The assessment was carried out by evaluating the RAWs for a set of components and operator actions for the model that included the fire and flood initiators and then, comparing them with the RAWs calculated previously for internal initiators.
The assessment was carried out by evaluating the RAWs for a set of components and operator actions for the model that included the fire and flood initiators and then, comparing them with the RAWs calculated previously for internal initiators.
Table 3 presents the comparisons for the same set of components and operator actions that were used for benchmarking. Obtaining RAWs for some items required separate computer runs which were not conducted for the integrated model. RAWs for these items were not available and are noted as NA.
Table 3 presents the comparisons for the same set of components and operator actions that were used for benchmarking. Obtaining RAWs for some items required separate computer runs which were not conducted for the integrated model. RAWs for these items were not available and are noted as NA.
To obtain the color for the component being out of service or the failed operator action, new thresholds were obtained. A comparison of the RAWs for the internal initiators with those obtained including the external initiators showed that in two cases the color or the risk significance would have increased by an order of magnitude if the risk contributions of external initiators were included. These items are noted in the table.
To obtain the color for the component being out of service or the failed operator action, new thresholds were obtained. A comparison of the RAWs for the internal initiators with those obtained including the external initiators showed that in two cases the color or the risk significance would have increased by an order of magnitude if the risk contributions of external initiators were included. These items are noted in the table.
Although the BVPS, Unit 2 SDP notebook does not include external initiators, the team compared the Rev. 1 results of Table 1 against the licensees PRA model including external initiators. In the two cases noted above, the notebook would underestimate one case: operator failure to recover MFW.
Although the BVPS, Unit 2 SDP notebook does not include external initiators, the team compared the Rev. 1 results of Table 1 against the licensees PRA model including external initiators. In the two cases noted above, the notebook would underestimate one case: operator failure to recover MFW.
ATTACHMENT A Table 3. Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 Integrated CDF = 3.33E-5, including external initiators, at Truncation Level of 1E-10 RAW Thresholds are: W = 1.03, Y = 1.3, R = 4.0, RR = 31.0, RRR = 301.3 No. Component       Basic Event  Internal      Plant                  Plant CDF    Rev. 1    Comments Out of Service     Name       Initiator     CDF       RAW        Color         SDP or Failed                      RAW         Color     Including  (Including   Color Operator                                  (Internal    External    External Action                                  Initiator)  Initiator  Initiator)
Table 3. Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 Integrated CDF = 3.33E-5, including external initiators, at Truncation Level of 1E-10 RAW Thresholds are: W = 1.03, Y = 1.3, R = 4.0, RR = 31.0, RRR = 301.3 No.
Component
Component Out of Service or Failed Operator Action Basic Event Name Internal Initiator RAW Plant CDF Color (Internal Initiator)
: 1. MDAFW pump       2FWE-P23A       7.71         R         5.07         R         R A
RAW Including External Initiator Plant CDF Color (Including External Initiator)
: 2. MDAFW pump       2FWE-P23B       1.47         W           1.33         Y         Y     risk significance B                                                                                          increased by one order   3. 1 TDAFW pump       2FWE-P22       2.7         Y         1.96         Y         Y
Rev. 1 SDP Color Comments Component 1.
: 4. 1 Accumulator     2SIS-TK21A     3.45         Y           2.3         Y         R
MDAFW pump A
: 5. 1 Cond. pump     Not modeled     1.0           G           G           G         G     RAW is assumed to be same as the MFW pump.
2FWE-P23A 7.71 R
: 6. 1 MFW pump         2FWS-P21A       1.0         G             G           G         G
5.07 R
: 7. 1 PORV FTO         Case run     1.21         W           NA                     W
R 2.
: 8. 1 PORV FTC       2RCS-PCV455D     1.3         W           1.12         W         W
MDAFW pump B
: 9. 1 RHR pump         2RHS-P21A       1.0         G           1.0         G         G
2FWE-P23B 1.47 W
: 10. HHSI pump A       2CHS-P21A     1.25         W           1.27         W         Y
1.33 Y
: 11. Spare HHSI         2CHS-P21C     1.34         W           1.22         W         W pump
Y risk significance increased by one order 3.
: 12. 1 BAT pump       Not Modeled                                                       G
1 TDAFW pump 2FWE-P22 2.7 Y
: 13. 1 LHSI pump       2SIS-P21B       1.07         W           1.04         W         W
1.96 Y
: 14. QS pump A         2QSS-P21A       1.96         Y           1.73         Y         Y
Y 4.
: 15. QS Pump B         2QSS-P21B       1.17         W           1.09         W         W
1 Accumulator 2SIS-TK21A 3.45 Y
: 16. RS pump C         2RSS-P21C       1.95         Y           1.72         Y         Y
2.3 Y
R 5.
1 Cond. pump Not modeled 1.0 G
G G
G RAW is assumed to be same as the MFW pump.
6.
1 MFW pump 2FWS-P21A 1.0 G
G G
G 7.
1 PORV FTO Case run 1.21 W
NA W
8.
1 PORV FTC 2RCS-PCV455D 1.3 W
1.12 W
W 9.
1 RHR pump 2RHS-P21A 1.0 G
1.0 G
G 10.
HHSI pump A 2CHS-P21A 1.25 W
1.27 W
Y 11.
Spare HHSI pump 2CHS-P21C 1.34 W
1.22 W
W 12.
1 BAT pump Not Modeled G
13.
1 LHSI pump 2SIS-P21B 1.07 W
1.04 W
W 14.
QS pump A 2QSS-P21A 1.96 Y
1.73 Y
Y 15.
QS Pump B 2QSS-P21B 1.17 W
1.09 W
W 16.
RS pump C 2RSS-P21C 1.95 Y
1.72 Y
Y
 
No.
Component Out of Service or Failed Operator Action Basic Event Name Internal Initiator RAW Plant CDF Color (Internal Initiator)
RAW Including External Initiator Plant CDF Color (Including External Initiator)
Rev. 1 SDP Color Comments 17.
RS pump D 2RRS-P21D 1.32 W
1.21 W
W 18.
RS HX C 2RSS-E21C 1.9 Y
1.7 Y
Y 19.
RS HX D 2RSS-E21D 1.28 W
1.18 W
W 20.
1 PCCW pump 2CCP-P21B 1.04 G
1.02 G
G 21.
SW Pump A 2SWS-P21B 1.62 Y
1.4 Y
Y 22.
SW pump B 2SWS-P21B 1.87 Y
1.53 Y
Y 23.
AC Bus Orange 4KVS-2AE 1013.8 RRR 595.
RRR RRR 24.
AC Bus Purple 4KVS-2DF 1021.1 RRR 601.
RRR RRR 25.
1 EDG 2EGS-EG2-1 3.37 Y
2.94 Y
Y 26.
ERF DG (Black) 1RG-EG-1 1.0 1.0 1.0 G
G 27.
DC Bus Orange DC-SWBD2-1 277 RR 160.65 RR RRR 28.
DC Bus Purple DC-SWBD2-2 161.
RRR NA RRR 29.
Battery 2-1 BAT-2-1 4.07 Y
3.18 Y
Y 30.
Battery 2-2 BAT-2-2 1.15 W
1.09 W
Y 31.
Battery Charger 1
BAT-CHG2-1 277.73 RR 160.32 RR RRR 32.
Battery Charger 2
BAT-CHG2-2 161.
RR NA RRR 33.
1 EDG Exhaust fan 2HVD-FN270A 1.0 G
1.0 G
W 34.
1 Containment IA compressor 2IAC-C21A 1.0 G
1.0 G
G 35.
1 Station Air Compressor 2SAS-C21A 1.0 G
1.0 G
G 36.
1 MSIV 2MSS-AOV101A 1.62 Y
1.35 Y
Y 37.
1 SCCW Pump 2CCS-P21A 1.0 G
1.02 G
G 38.
1 SG HRV 2SVS-HCV104 1.12 W
1.07 W
Y 39.
1 SG ASDV 2SVS-PCV101A 1.04 G
1.02 G
Y


No. Component         Basic Event  Internal      Plant                  Plant CDF    Rev. 1  Comments Out of Service       Name       Initiator     CDF       RAW        Color         SDP or Failed                        RAW         Color     Including  (Including   Color Operator                                  (Internal    External   External Action                                    Initiator)  Initiator  Initiator)
No.
: 17. RS pump D          2RRS-P21D      1.32          W          1.21          W        W
Component Out of Service or Failed Operator Action Basic Event Name Internal Initiator RAW Plant CDF Color (Internal Initiator)
: 18. RS HX C            2RSS-E21C      1.9          Y           1.7          Y          Y
RAW Including External Initiator Plant CDF Color (Including External Initiator)
: 19. RS HX D            2RSS-E21D      1.28         W          1.18          W          W
Rev. 1 SDP Color Comments Operator Actions 40.
: 20. 1 PCCW pump        2CCP-P21B      1.04          G          1.02        G           G
Op fails to recover MFW OPROF2 5.11 Y
: 21. SW Pump A        2SWS-P21B      1.62          Y          1.4        Y          Y
4.81 R
: 22. SW pump B        2SWS-P21B      1.87          Y          1.53        Y          Y
W risk significance increased by one order of magnitude 41.
: 23. AC Bus Orange      4KVS-2AE    1013.8        RRR          595.        RRR        RRR
Fails to FB OPROB1 28.69 R
: 24. AC Bus Purple      4KVS-2DF    1021.1       RRR          601.       RRR        RRR
16.93 R
: 25. 1 EDG            2EGS-EG2-1      3.37          Y          2.94        Y          Y
R 42.
: 26. ERF DG (Black)      1RG-EG-1      1.0           1.0        1.0         G           G
Fails to DEP in SLOCA case run 1.001 G
: 27. DC Bus Orange    DC-SWBD2-1      277          RR          160.65      RR          RRR          28. DC Bus Purple    DC-SWBD2-2      161.        RRR          NA                    RRR
NA G
: 29. Battery 2-1          BAT-2-1      4.07          Y          3.18          Y          Y
43.
: 30. Battery 2-2          BAT-2-2      1.15          W          1.09        W          Y
RAPDEP in SLOCA OPRCD1 1.06 W
: 31. Battery Charger  BAT-CHG2-1     277.73        RR          160.32        RR        RRR 1
1.03 W
: 32. Battery Charger    BAT-CHG2-2      161.        RR          NA                     RRR 2
W 44.
: 33. 1 EDG Exhaust    2HVD-FN270A      1.0          G          1.0          G          W fan
Fails to close the Block valve OPRPI1 1.0 G
: 34. 1 Containment      2IAC-C21A      1.0          G          1.0          G          G IA compressor
1.0 G
: 35. 1 Station Air      2SAS-C21A      1.0          G          1.0          G          G Compressor
G 45.
: 36. 1 MSIV            2MSS-AOV101A    1.62        Y          1.35          Y          Y
EQ and isolation in a SGTR OPRSL1 2.86 Y
: 37. 1 SCCW Pump        2CCS-P21A      1.0        G          1.02          G          G
2.04 Y
: 38. 1 SG HRV          2SVS-HCV104    1.12        W           1.07          W         Y
Y 46.
: 39. 1 SG ASDV        2SVS-PCV101A    1.04        G          1.02          G          Y
RWST makeup Case run 1.27 W
NA Y
47.
Fails to initiate RHR OPRRR1 1.02 G
1.01 G
W 48.
Emergency Boration OPROA1 1.36 W
1.20 W
W


No. Component          Basic Event  Internal      Plant                  Plant CDF    Rev. 1    Comments Out of Service        Name        Initiator      CDF      RAW        Color        SDP or Failed                        RAW        Color      Including  (Including  Color Operator                                    (Internal    External    External Action                                    Initiator)  Initiator  Initiator)
ATTACHMENT A 5. LIST OF PARTICIPANTS Wayne Schmidt USNRC - Region I Peter Wilson USNRC - NRR Pranab Samanta BNL Robert Buell INEEL William Etzelf First Energy/Beaver Valley Power Station}}
Operator Actions
: 40. Op fails to          OPROF2        5.11          Y          4.81          R          W      risk significance recover MFW                                                                                  increased by one order of magnitude
: 41. Fails to FB          OPROB1        28.69          R          16.93        R          R
: 42. Fails to DEP in      case run      1.001          G          NA                      G SLOCA
: 43. RAPDEP in            OPRCD1        1.06        W          1.03          W          W SLOCA
: 44. Fails to close      OPRPI1        1.0          G          1.0          G          G the Block valve          45. EQ and isolation    OPRSL1        2.86          Y          2.04          Y          Y in a SGTR
: 46. RWST makeup          Case run      1.27        W            NA                      Y
: 47. Fails to initiate    OPRRR1        1.02        G          1.01          G          W RHR
: 48. Emergency            OPROA1        1.36        W          1.20          W          W Boration
: 5. LIST OF PARTICIPANTS Wayne Schmidt   USNRC - Region I Peter Wilson   USNRC - NRR Pranab Samanta BNL Robert Buell   INEEL William Etzelf First Energy/Beaver Valley Power Station ATTACHMENT A                    }}

Latest revision as of 07:40, 16 January 2025

Results of the Beaver Valley Power Station Unit 2 SDP Phase 2 Notebook Benchmarking Visit, During July, 2003
ML032681044
Person / Time
Site: Beaver Valley
Issue date: 09/24/2003
From: Reinhart F
Division of Systems Safety and Analysis
To: O'Reilly P, Richards S
NRC/NRR/DIPM/IIPB, NRC/RES/DRAA/OERAB
Wilson P, NRR/DSSA/SPSB, 415-1114
References
Download: ML032681044 (22)
v • d • e


Text

September 24, 2003 NOTE TO:

Stuart Richards, Chief Inspection Program Branch Division of Inspection Program Management Office of Nuclear Reactor Regulation Patrick D. OReilly Operating Experience Risk Applications Branch Division of Risk Analysis and Applications Office of Nuclear Regulatory Research FROM:

Mark F. Reinhart, Chief

/RA/ M. Caruso for Licensing Section Probabilistic Safety Assessment Branch Division of Systems Safety and Analysis Office of Nuclear Reactor Regulation

SUBJECT:

RESULTS OF THE BEAVER VALLEY POWER STATION UNIT 2 SDP PHASE 2 NOTEBOOK BENCHMARKING VISIT During July, 2003, NRC staff and contractors visited the Beaver Valley Power Station to compare the Beaver Valley Unit 2 Significance Determination Process (SDP) Phase 2 notebook and licensees risk model results to ensure that the SDP notebook was generally conservative.

The Beaver Valley Unit 2 PRA did include most external initiating events, so sensitivity studies were performed to assess the impact of these initiators on SDP color determinations. In addition, the results from analyses using the NRCs draft Revision 3i Standard Plant Analysis Risk (SPAR) model for Beaver Valley Unit 2 were compared with the licensees risk model. The results of the SPAR model benchmarking effort will be documented in the next revision of the SPAR (revision 3) model documentation.

The benchmarking visit identified that there was a strong correlation between the Phase 2 SDP Notebook and the licensees PRA. The results indicate that the Beaver Valley Unit 2 Phase 2 notebook was generally more conservative in comparison to the licensees PRA. The revision 1 SDP notebook will capture 96% (results matched or overestimated the licensees PRA by one order of magnitude) of the risk significance of inspection findings. A summary of the results of comparisons of hypothetical inspection findings between SDP notebook and the licensees PRA are as follows.

CONTACT: Peter Wilson, SPSB/DSSA/NRR 301-415-1114

S. Richards 2

P. OReilly 2% (1 of 47 cases)

Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)

Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)

Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)

Consistent risk significance.

The Rev-1 SDP notebook has been significantly improved as a result of the benchmarking activity. The number of cases that the Rev-1 SDP would match that of the updated licensees PRA has increased from 23 to 33. The number of overestimations by two orders of magnitude decreased from 5 to 1. In addition, the number of underestimations decreased from 8 to 1.

However, the number of overestimations by one order of magnitude increased slightly from 11 to 12.

The licensees PRA staff was very knowledgeable of the plant model and provided very helpful comments during the benchmark visit.

Attachment A describes the process and results of the comparison of the Beaver Valley Unit 2 SDP Phase 2 Notebook and the licensees PRA.

Attachments: As stated CONTACT:

Peter Wilson, SPSB/DSSA/NRR 301-415-1114

S. Richards 2

P. OReilly 2% (1 of 47 cases)

Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)

Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)

Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)

Consistent risk significance.

The Rev-1 SDP notebook has been significantly improved as a result of the benchmarking activity. The number of cases that the Rev-1 SDP would match that of the updated licensees PRA has increased from 23 to 33. The number of overestimations by two orders of magnitude decreased from 5 to 1. In addition, the number of underestimations decreased from 8 to 1.

However, the number of overestimations by one order of magnitude increased slightly from 11 to 12.

The licensees PRA staff was very knowledgeable of the plant model and provided very helpful comments during the benchmark visit.

Attachment A describes the process and results of the comparison of the Beaver Valley Unit 2 SDP Phase 2 Notebook and the licensees PRA.

Attachments: As stated DISTRIBUTION: SPSB:r/f W. Schmidt Accession#ML032681044 G:\\wilson\\Pilgrimbench.wpd NRR-096 OFFICE SPSB SPSB:SC SPSB:RII NAME PWilson:nxh2 MReinhart /RA/ M. Caruso for WSchmidt DATE 09/24/03 09/24/03 09/24/03 OFFICIAL RECORD COPY

ATTACHMENT A

SUMMARY

REPORT ON BENCHMARKING TRIP TO THE BEAVER VALLEY POWER STATION UNIT 2 Pranab K. Samanta Energy Sciences and Technology Department Brookhaven National Laboratory Upton, NY 11973-5000 September 2003

ATTACHMENT A

-v-Table of Contents Page Introduction............................................................... 1 Summary Results from Benchmarking.......................................... 2 Proposed Modifications to the Rev. 0 SDP Notebook............................... 8 3.1 Specific Changes to the Rev. 0 SDP Notebook for the Beaver Valley Power Station, Unit 2.................................. 8 3.2 Generic Change in 0609 for Inspectors...............................

10 3.3 Generic Change to the SDP Notebook...............................

10 Discussion on External Events................................................ 11 List of Participants.......................................................... 15 List of Tables Page Table 1.

Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2......................................................... 4 Table 2.

Comparative Summary of Benchmarking Results........................ 7 Table 3.

Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2......................................................... 12

ATTACHMENT A 1. INTRODUCTION A benchmarking of the Risk-Informed Inspection Notebook for the Beaver Valley Power Station, Unit 2, to be referred to as BV-2, was conducted during a plant site visit on July 28-August 2, 2003. NRC staff (P. Wilson and W. Schmidt) and BNL staff (P. Samanta) participated in this Benchmarking exercise.

In preparation for the meeting, BNL staff reviewed the SDP notebook for the Beaver Valley Power Station and evaluated a set of hypothetical inspection findings using the Rev. 0 SDP worksheets. In addition, NRC staff provided the licensee with a copy of the meeting protocol.

The major milestones achieved during this meeting were as follows:

1.

Recent modifications made to the BV-2 PRA were discussed for consideration in the Rev. 1 model to be prepared following benchmarking.

2.

Importance measures, including the Risk Achievement Worths (RAWs) for the basic events in the internal events model for average maintenance, were obtained from the licensee.

3.

Benchmarking was conducted using the Rev. 0 SDP model and the revised SDP model considering the licensees input and other modifications that were judged necessary based on comparison of the SDP model and the licensees detailed model.

4.

For cases where the color evaluated by the SDP notebook differed from that determined based on the RAW values generated by the updated licensees PRA, results of the licensees base case model including the dominant minimal cutsets were reviewed to understand the reason for the differences.

The Rev. 1 version of the SDP notebook was developed considering the changes identified based on the licensees input and the evaluation of the benchmarking results.

ATTACHMENT A 2.

SUMMARY

RESULTS FROM BENCHMARKING Summary of Benchmarking Results Benchmarking of the SDP Notebook for the Beaver Valley Power Station, Unit 2 was conducted comparing the risk significance of the inspection findings obtained using the notebook with that obtained using the plant PRA. The benchmarking identified the hypothetical inspection findings for which the results of the evaluation using the notebook were under or overestimations compared to the plant PRA. One case of a non-conservative result or underestimation by the notebook (i.e., the significance obtained using the notebook was one color lower than that obtained by the plant PRA) was noted. Also, one case of a conservative result by two orders of magnitude (i.e., the significance obtained using the notebook was two colors higher than that to be obtained using the plant PRA) was noted. A summary of the results of the risk characterization of hypothetical inspection findings is as follows:

2% (1 of 47 cases)

Non-conservative; underestimation of risk significance (by one order of magnitude) 2% (1 of 47 cases)

Conservative; overestimation of risk significance (by two orders of magnitude) 26% (12 of 47 cases)

Conservative; overestimation of risk significance (by one order of magnitude) 70% (33 of 47 cases)

Consistent risk significance.

Detailed results of benchmarking are summarized in Table 1. Table 1 consists of eight columns. The first two columns identify the components or the case runs. The assigned colors from the SDP Rev. 0 worksheets without incorporating any modification from the Benchmarking exercise are shown in the third column. The fourth column gives the basic event name in the plant PRA used to obtain the risk achievement worth (RAW) for the component out of service or the failed operator action. The fifth and sixth columns respectively show the licensees internal RAW value and the color to be defined based on the RAW values from the latest PRA model.

The seventh column presents the colors for the inspection findings based on the Rev. 1 version of the notebook. The Rev. 1 version of the notebook was prepared considering the revisions to the Rev. 0 version of the SDP notebook judged applicable during Benchmarking. The last column provides comments identifying the difference in results between the SDP Rev. 1 notebook and the plant PRA, and the applicable rules in obtaining the color of the inspection finding using the SDP notebook.

Table 2 presents a summary of the comparison between the results obtained using the Beaver Valley Power Station, Unit 2 notebook and the plant PRA. It also shows a comparison of the results using the Rev. 0 and Rev. 1 versions of the notebook. The results show that both underestimations and overestimations by the notebook were reduced and, consequently, matches were increased through revisions to the notebook implemented as a result of Benchmarking. The overestimations were reduced from 34% to 28%, the underestimations were reduced from 17% to 2%, and the matches increased from 49% to 70%.

ATTACHMENT A Discussion of Non-conservative Results by the Notebook During benchmarking, non-conservative results or underestimation by the notebook compared to the plant PRA were noted for 1 out of the 48 cases analyzed. The reason for the difference, as identified, is discussed below.

1. Operator failure to recover MFW following transient or SLOCA was underestimated by one order by the notebook. The reason for the underestimation was the difference in failure probability for the AFW system in the PRA versus the mitigation credit for AFW in the notebook. In the plant PRA, failure of AFW system was modeled due to common cause failure of the check valves resulting in back flow with a probability of approximately 1E-3. In the notebook, the credit for the AFW system was 4 (3 for the motor-driven pumps and 1 for the turbine-driven pump). This difference was the reason for the underestimation. The notebook did not model the common cause failure of the check valves leading to failure of the AFW pumps.

Failure of AFW pumps due to failure of the check valves could be recovered through closure of the hydraulic control valves in the line. This action was not modeled in the plant PRA.

Discussion of Conservative Results by the Notebook Eight cases of overestimations or conservative results were noted during the benchmarking. Of the eight cases, one case was overestimated by two orders of magnitude and the remaining seven cases were overestimated by one order of magnitude. Since the notebooks are designed to be screening tools and include assumptions that can result in conservative assessment, overestimation by an order of magnitude, i.e., by one color, is not unexpected.

We discuss the overestimation by two orders of magnitude

1. Failure of 1 SG ASDV was overestimated by two orders of magnitude, i.e., by two colors. SG ASDVs provide steam relief for the secondary and are used for RCS depressurization. In all cases when SG ASDVs were used, multiple redundancies were available. In the PRA calculation, the loss of 1 SG ASDV has a minimal impact. However, in the notebook evaluation, many sequences were counted considering the base case impact leading to the overestimation by two orders of magnitude.

Changes Incorporated Following Benchmarking Resulting in Updating of Benchmarking Results No change was made following benchmarking that resulted in changes to the benchmarking results.

Table 1. Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 Internal Events CDF = 1.85E-5, excluding internal flooding, at Truncation Level of 1E-10 RAW Thresholds are: W = 1.054, Y = 1.54, R = 6.4, RR = 55., RRR = 541.5 No.

Component Out of Service or Failed Operator Action SDP Before Basic Event Name RAW Plant CDF Color SDP After Comments Component 1.

1 MDAFW pump A

R 2FWE-P23A 7.71 R

R 2.

MDAFW pump B R

2FWE-P23B 1.47 W

Y over by 1 3.

1 TDAFW pump Y

2FWE-P22 2.7 Y

Y 4.

1 Accumulator R

2SIS-TK21A 3.45 Y

R over by 1 5.

1 Cond. pump G

Not modeled 1.0 G

G RAW is assumed to be same as the MFW pump.

6.

1 MFW pump G

2FWS-P21A 1.0 G

G 7.

1 PORV FTO W

Case run 1.21 W

W 8.

1 PORV FTC Y

2RCS-PCV455D 1.3 W

W 9.

1 RHR pump G

2RHS-P21A 1.0 G

G 10.

HHSI pump A Y

2CHS-P21A 1.25 W

Y over by 1 11.

Spare HHSI pump W

2CHS-P21C 1.34 W

W 12.

1 BAT pump G

Not Modeled G

Comparable RAW not available 13.

1 LHSI pump W

2SIS-P21B 1.07 W

W 14.

QS pump A G

2QSS-P21A 1.96 Y

Y 15.

QS Pump B G

2QSS-P21B 1.17 W

W 16.

RS pump C R

2RSS-P21C 1.95 Y

Y 17.

RS pump D R

2RRS-P21D 1.32 W

W 18.

RS HX C R

2RSS-E21C 1.9 Y

Y 19.

RS HX D R

2RSS-E21D 1.28 W

W 20.

1 CCP pump Y

2CCP-P21B 1.04 G

G

No.

Component Out of Service or Failed Operator Action SDP Before Basic Event Name RAW Plant CDF Color SDP After Comments 21.

SW Pump A R

2SWS-P21B 1.62 Y

Y 22.

SW pump B R

2SWS-P21B 1.87 Y

Y 23.

AC Orange Bus RRR 4KVS-2AE 1013.8 RRR RRR 24.

AC Purple Bus RRR 4KVS-2DF 1021.1 RRR RRR 25.

1 EDG Y

2EGS-EG2-1 3.37 Y

Y 26.

ERF DG (Black)

G 1RG-EG-1 1.0 G

G Always Green 27.

DC Orange Bus RRR DC-SWBD2-1 277 RR RRR over by 1 28.

DC Purple Bus RRR DC-SWBD2-2 161.

RR RRR over by 1 29.

Battery 2-1 Y

BAT-2-1 4.07 Y

Y 30.

Battery 2-2 Y

BAT-2-2 1.15 W

Y over by 1 31.

Battery Charger 1 R

BAT-CHG2-1 277.73 RR RRR over by 1 32.

Battery Charger 2 R

BAT-CHG2-2 161.

RR RRR over by 1 33.

1 EDG Exhaust fan Y

2HVD-FN270A 1.0 G

W over by 1 34.

1 Containment IA compressor G

2IAC-C21A 1.0 G

G Always Green 35.

1 Station Air Compressor G

2SAS-C21A 1.0 G

G Always Green 36.

1 MSIV Y

2MSS-AOV101A 1.62 Y

Y 37.

1 SCCW Pump G

2CCS-P21A 1.0 G

G Always Green 38.

1 SG HRV W

2SVS-HCV104 1.12 W

Y over by 1 39.

1 SG ASDV W

2SVS-PCV101A 1.04 G

Y over by 2 Operator Actions 40.

Op fails to recover MFW G

OPROF2 5.11 Y

W under 41.

Fails to FB R

OPROB1 28.69 R

R 42.

Fails to DEP in SLOCA W

case run 1.001 G

G

No.

Component Out of Service or Failed Operator Action SDP Before Basic Event Name RAW Plant CDF Color SDP After Comments 43.

RAPDEP in SLOCA W

OPRCD1 1.06 W

W 44.

Fails to close the Block valve W

OPRPI1 1.0 G

G 45.

EQ and isolation in a SGTR R

OPRSL1 2.86 Y

Y 46.

RWST makeup W

Case run 1.27 W

Y over by 1 47.

Fails to initiate RHR W

OPRRR1 1.02 G

W over by 1 48.

Emergency Boration W

OPROA1 1.36 W

W

ATTACHMENT A Table 2: Comparative Summary of Benchmarking Results Comparisons Rev. 0 SDP Notebook Following Benchmarking, Rev. 1 Notebook Total Number of Cases = 48 Number of Cases Percentage Number of Cases Percentage SDP: Less Conservative 8 (1) 17 1 (2) 2 SDP:

More Conserv ative one order 11 23 12 26 two orders 5

11 1

2 SDP: Matched 23 49 33 70 Comparable RAW not available or not modeled in the Notebook 1

1 Notes:

1.

2 cases by two orders of magnitude and the remaining 6 cases by one order of magnitude.

2.

By one order of magnitude.

ATTACHMENT A 3. PROPOSED MODIFICATIONS TO THE REV. 0 SDP NOTEBOOK A set of modifications were proposed for the Rev. 0 SDP notebook as a result of the site visit.

These proposed modifications are driven by the licensees revisions to the plants PRA, better understanding of the current plant design features, revised Human Error Probabilities (HEPs),

modified initiator frequencies, and the results of benchmarking.

3.1 Specific Changes to the Rev. 0 SDP Notebook for the Beaver Valley Power Station, Unit 2 The following changes were made based on the licensees inputs and evaluations conducted as part of Benchmarking:

1.

Changes to Table 1 1.1 Loss of a 4 kV EAC Bus (LAC) was replaced by two separate initiators, Loss of a 4 kV Orange Bus (LACO) and Loss of 4 kV Purple Bus (LACP). Both initiators were placed in Row II.

1.2 Loss of a DC Bus (LDC) was replaced by two separate initiators, Loss of a DC Orange Bus (LDCO) and Loss of a DC Purple Bus (LDCP). Both initiators were placed in Row II.

1.3 Loss of Service Water Header A or B (LOSWH) was replaced by two separate initiators, Loss of Service Water Header A (LOSWHA) and Loss of Service Water Header B (LOSWHB). Both initiators were placed in Row III.

1.4 Loss of Primary Component Cooling Water (LCCP) was added in Row II.

2.

Changes to Table 2 2.1 DC dependency of MFW and condensate pumps was clarified. Startup feed pump was added as a major component. ERF DG was removed as a support system, but a footnote was added stating that the ERF diesel serves as the backup power source for the startup feed pump.

2.2 CIA and SSPS dependency for MSIV were removed. MSIV was included as part of Main Steam.

2.3 SW Header B as the backup water supply for the AFW system was noted in the footnote and removed from the Support System column.

ATTACHMENT A 2.4 125V DC dependency for TD AFW pump was removed. A footnote was added to note that the SOVs on the steam admission line fail open on loss of power.

2.5 125V DC dependency for EAC Buses was added.

2.6 A footnote for the ERF diesel was added to note the separate battery for start and control power.

2.7 480V EAC dependency for the 125V DC system was noted.

2.8 SSPS dependency on Vital Bus Channels was clarified. Channels I and II are needed, not channels III and IV.

2.9 Major components for Ventilation System was corrected to include only fans.

Dependency on Vital Bus Channels I and II was deleted.

2.10 For the SW system, it was noted in the footnote that ventilation is needed only for starting the standby pumps.

2.11 For the IA/CIA system, a footnote was added to note that ERF diesel provides a backup power supply in case of loss of power.

2.12 The Chilled Water system was deleted.

3.

Changes to Worksheets and Event Trees 3.1 RWST makeup in case of failure of HPR and LPR was added, as applicable, for different initiators.

3.2 For the HPR and LPR functions in different transient and SLOCA scenarios, success of 1/2 QS pumps is needed and is included as part of the mitigation capability. For MLOCA and LLOCA, success for a QS pump is not required.

3.3 In SLOCA worksheet, use of the Heat Release valve was credited in the RAPDEP function and the operator action credit was reduced to 1 (from 2).

3.4 SLOCA worksheet and event tree were modified to credit FW consistently following loss of AFW.

3.5 SORV worksheet and event tree were modified similar to SLOCA worksheet and event tree.

ATTACHMENT A 3.6 LLOCA worksheet and event tree were modified to remove the need for QS for LPR.

3.7 LOOP worksheet and event tree were modified to address the capability to crosstie other units EDG to power a charging pump. For this, Crosstieing other units EDG is separated from the EAC function. RWST makeup is only credited when offsite power is recovered.

3.8 SGTR worksheet and event tree were modified to remove the need for EQ following FB and to address RWST makeup.

3.9 In the ATWS worksheet, steam relief requirement for AFW was added. Also, RWST suction, in case of failure of the BAT pumps, was included.

3.10 Separate worksheets and event trees were included for Loss of Service Water Headers A and B. For loss of Service Water Header B, RWST makeup is not possible.

3.11 LEAC worksheet was modified to include manual operation of ASDVs and to modify the credit for RAPDEP to operator action = 1.

3.12 Separate worksheets and event trees were developed for Loss of Orange and Purple EAC Buses. In the Loss of the Orange Bus (LACO), credit for using feedwater was changed to operator action = 2 based on the plant-specific HEP.

Loss of the Purple Bus (LACP) results in loss of the feed pumps and the ability to use RWST makeup.

3.13 Similar to loss of AC Buses, separate worksheets and event trees were developed for loss of orange and purple DC Buses.

3.14 The worksheet and event tree were developed for Loss of Primary Component Cooling water (LCCP).

3.2 Generic Change in 0609 for Inspectors None identified.

3.3 Generic Change to the SDP Notebook None identified.

ATTACHMENT A 4. DISCUSSION ON EXTERNAL EVENTS The Beaver Valley Power Station, Unit 2 integrated PRA model includes internal floods, internal fire, and seismic initiators. The CDF in the integrated model including these external initiators was 3.33E-5/reactor-yr. The integrated model was used to assess whether the inclusion of the external initiators will result in increased risk significance for components or operator actions.

The assessment was carried out by evaluating the RAWs for a set of components and operator actions for the model that included the fire and flood initiators and then, comparing them with the RAWs calculated previously for internal initiators.

Table 3 presents the comparisons for the same set of components and operator actions that were used for benchmarking. Obtaining RAWs for some items required separate computer runs which were not conducted for the integrated model. RAWs for these items were not available and are noted as NA.

To obtain the color for the component being out of service or the failed operator action, new thresholds were obtained. A comparison of the RAWs for the internal initiators with those obtained including the external initiators showed that in two cases the color or the risk significance would have increased by an order of magnitude if the risk contributions of external initiators were included. These items are noted in the table.

Although the BVPS, Unit 2 SDP notebook does not include external initiators, the team compared the Rev. 1 results of Table 1 against the licensees PRA model including external initiators. In the two cases noted above, the notebook would underestimate one case: operator failure to recover MFW.

Table 3. Summary of Benchmarking Results for Beaver Valley Power Station, Unit 2 Integrated CDF = 3.33E-5, including external initiators, at Truncation Level of 1E-10 RAW Thresholds are: W = 1.03, Y = 1.3, R = 4.0, RR = 31.0, RRR = 301.3 No.

Component Out of Service or Failed Operator Action Basic Event Name Internal Initiator RAW Plant CDF Color (Internal Initiator)

RAW Including External Initiator Plant CDF Color (Including External Initiator)

Rev. 1 SDP Color Comments Component 1.

MDAFW pump A

2FWE-P23A 7.71 R

5.07 R

R 2.

MDAFW pump B

2FWE-P23B 1.47 W

1.33 Y

Y risk significance increased by one order 3.

1 TDAFW pump 2FWE-P22 2.7 Y

1.96 Y

Y 4.

1 Accumulator 2SIS-TK21A 3.45 Y

2.3 Y

R 5.

1 Cond. pump Not modeled 1.0 G

G G

G RAW is assumed to be same as the MFW pump.

6.

1 MFW pump 2FWS-P21A 1.0 G

G G

G 7.

1 PORV FTO Case run 1.21 W

NA W

8.

1 PORV FTC 2RCS-PCV455D 1.3 W

1.12 W

W 9.

1 RHR pump 2RHS-P21A 1.0 G

1.0 G

G 10.

HHSI pump A 2CHS-P21A 1.25 W

1.27 W

Y 11.

Spare HHSI pump 2CHS-P21C 1.34 W

1.22 W

W 12.

1 BAT pump Not Modeled G

13.

1 LHSI pump 2SIS-P21B 1.07 W

1.04 W

W 14.

QS pump A 2QSS-P21A 1.96 Y

1.73 Y

Y 15.

QS Pump B 2QSS-P21B 1.17 W

1.09 W

W 16.

RS pump C 2RSS-P21C 1.95 Y

1.72 Y

Y

No.

Component Out of Service or Failed Operator Action Basic Event Name Internal Initiator RAW Plant CDF Color (Internal Initiator)

RAW Including External Initiator Plant CDF Color (Including External Initiator)

Rev. 1 SDP Color Comments 17.

RS pump D 2RRS-P21D 1.32 W

1.21 W

W 18.

RS HX C 2RSS-E21C 1.9 Y

1.7 Y

Y 19.

RS HX D 2RSS-E21D 1.28 W

1.18 W

W 20.

1 PCCW pump 2CCP-P21B 1.04 G

1.02 G

G 21.

SW Pump A 2SWS-P21B 1.62 Y

1.4 Y

Y 22.

SW pump B 2SWS-P21B 1.87 Y

1.53 Y

Y 23.

AC Bus Orange 4KVS-2AE 1013.8 RRR 595.

RRR RRR 24.

AC Bus Purple 4KVS-2DF 1021.1 RRR 601.

RRR RRR 25.

1 EDG 2EGS-EG2-1 3.37 Y

2.94 Y

Y 26.

ERF DG (Black) 1RG-EG-1 1.0 1.0 1.0 G

G 27.

DC Bus Orange DC-SWBD2-1 277 RR 160.65 RR RRR 28.

DC Bus Purple DC-SWBD2-2 161.

RRR NA RRR 29.

Battery 2-1 BAT-2-1 4.07 Y

3.18 Y

Y 30.

Battery 2-2 BAT-2-2 1.15 W

1.09 W

Y 31.

Battery Charger 1

BAT-CHG2-1 277.73 RR 160.32 RR RRR 32.

Battery Charger 2

BAT-CHG2-2 161.

RR NA RRR 33.

1 EDG Exhaust fan 2HVD-FN270A 1.0 G

1.0 G

W 34.

1 Containment IA compressor 2IAC-C21A 1.0 G

1.0 G

G 35.

1 Station Air Compressor 2SAS-C21A 1.0 G

1.0 G

G 36.

1 MSIV 2MSS-AOV101A 1.62 Y

1.35 Y

Y 37.

1 SCCW Pump 2CCS-P21A 1.0 G

1.02 G

G 38.

1 SG HRV 2SVS-HCV104 1.12 W

1.07 W

Y 39.

1 SG ASDV 2SVS-PCV101A 1.04 G

1.02 G

Y

No.

Component Out of Service or Failed Operator Action Basic Event Name Internal Initiator RAW Plant CDF Color (Internal Initiator)

RAW Including External Initiator Plant CDF Color (Including External Initiator)

Rev. 1 SDP Color Comments Operator Actions 40.

Op fails to recover MFW OPROF2 5.11 Y

4.81 R

W risk significance increased by one order of magnitude 41.

Fails to FB OPROB1 28.69 R

16.93 R

R 42.

Fails to DEP in SLOCA case run 1.001 G

NA G

43.

RAPDEP in SLOCA OPRCD1 1.06 W

1.03 W

W 44.

Fails to close the Block valve OPRPI1 1.0 G

1.0 G

G 45.

EQ and isolation in a SGTR OPRSL1 2.86 Y

2.04 Y

Y 46.

RWST makeup Case run 1.27 W

NA Y

47.

Fails to initiate RHR OPRRR1 1.02 G

1.01 G

W 48.

Emergency Boration OPROA1 1.36 W

1.20 W

W

ATTACHMENT A 5. LIST OF PARTICIPANTS Wayne Schmidt USNRC - Region I Peter Wilson USNRC - NRR Pranab Samanta BNL Robert Buell INEEL William Etzelf First Energy/Beaver Valley Power Station

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