ML050210284
| ML050210284 | |
| Person / Time | |
|---|---|
| Issue date: | 02/11/2005 |
| From: | Ader C NRC/RES/DRAA |
| To: | Bischoff G, Brooks C, Fertel M, Gaertner J, Gray J, Holm J, Lochbaum D, Mallay J, Rahn F B & W Owners Group, BWR Owners Group, Electric Power Research Institute, Entergy Nuclear Operations, Framatome Technologies, Institute of Nuclear Power Operations (INPO), Nuclear Energy Institute, Union of Concerned Scientists |
| References | |
| Download: ML050210284 (17) | |
Text
February 11, 2005 Mr. Charles Brooks, Staff Assistant Industry and Government Relations Institute of Nuclear Power Operations 700 Galleria Parkway, SE, Suite 100 Atlanta, GA 30339-5957
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Brooks:
In accordance with our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency (CDF) estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
The evaluation results indicate an industry average SBO CDF (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from
C. Brooks approximately 1980 through the present, which show a downward trend from a high of 2.0 x 10-5/rcry to the present value. This historical decrease in estimated SBO CDF is probably the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO CDF for U.S. commercial NPPs.
Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated
C. Brooks LETTERS DATED: 2/7/05
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS Distribution w/o attachment:
OERAB RF RBarrett, NRR GShukla, NRR MHoncharik, NRR DRAA RF BSheron, NRR DHolland, NRR TAlexion, NRR JCraig/CPaperiello, RES RBorchardt, NRR BBenney, NRR BPham, NRR JLamb, NRR JDyer, NRR SLee, OEDO JCalvo, NRR Identical Letters:
Mr. Charles Brooks, Staff Assistant Mr. Gordon C. Bischoff, Manager Industry and Government Relations Owners Group Program Management Office Institute of Nuclear Power Operations Mail Stop 5-16 700 Galleria Parkway, NW, Suite 100 P.O. Box 355 Atlanta, Georgia 30339-5957 Pittsburgh, PA 15230-0355 Mr. Marvin S. Fertel Mr. Jerald Holm, Director of Regulatory Affairs Senior Vice President/Chief Nuclear Officer B&W Owners Group Services Nuclear Energy Institute Framatome Technologies, Inc.
1776 I Street, NW, Suite 400 3315 Old Forest Road Washington, DC 20006-3708 P.O. Box 10935 Lynchburg, VA 24506-0935 Mr. David A. Lochbaum, Nuclear Safety Engineer Union of Concerned Scientists Mr. Jack A. Gray, Jr., Regulatory Response Group Chairman 1707 H Street, NW, Suite 600 BWR Owners Group Washington, DC 20006-3962 Entergy Nuclear Operations, Inc.
440 Hamilton Avenue, Mail Stop 12C Mr. John P. Gaertner, Senior Technical Leader P.O. Box 5029 Risk Assessment and Management White Plains, NY 10601-5029 Electric Power Research Institute 1300 Harris Blvd.
Mr. Frank J. Rahn, Manager P.O. Box 217097 Risk-Based Prioritization Charlotte, NC 28221 Electric Power Research Institute 3412 Hillview Avenue Palo Alto, CA 94304-1395 DOCUMENT NAME: G:\\EXTERNAL SBO REPORT REVIEW LETTER.WPD OAR in ADAMS? (Y or N) Y ADAMS Accession No.: ML050210284 Template No. RES-006 Attachment ML No.: ML050140399 Publicly Available? (Y or N) Y Date of Release to Public Sensitive? N
- See previous concurrence To receive a copy of this document, indicate in the box: C = Copy wo/encl E = Copy w/encl N = No copy OFFICE
- OERAB E
- OERAB N
- OERAB C
- RES Tech Editor N
- SISP Review N
NAME DRasmuson CLui NChokshi PGarrity DRasmuson DATE 1/21/05 1/21/05 1/21/05 1/23/05 1/21/05 OFFICE
- SISP Review N
- DRAA NAME NChokshi CAder DATE 1/21/05 2/11/05
February 11, 2005 Mr. Marvin S. Fertel Senior Vice President/Chief Nuclear Officer Nuclear Energy Institute 1776 I Street, NW, Suite 400 Washington, DC 20006-3708
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Fertel:
In accordance with our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency (CDF) estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
The evaluation results indicate an industry average SBO CDF (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from approximately 1980 through the present, which show a downward trend from a high of
M.S. Fertel 2.0 x 10-5/rcry to the present value. This historical decrease in estimated SBO CDF is probably the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO CDF for U.S. commercial NPPs.
Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated
February 11, 2005 Mr. David A. Lochbaum, Nuclear Safety Engineer Union of Concerned Scientists 1707 H Street, NW, Suite 600 Washington, DC 20006-3962
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Lochbaum:
In accordance with our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency (CDF) estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
The evaluation results indicate an industry average SBO CDF (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from approximately 1980 through the present, which show a downward trend from a high of 2.0 x 10-5/rcry to the present value. This historical decrease in estimated SBO CDF is probably
D.A. Lochbaum the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO CDF for U.S. commercial NPPs.
Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated
February 11, 2005 Mr. John Gaertner, Senior Technical Leader Risk Assessment and Management Electric Power Research Institute 1300 Harris Blvd.
P.O. Box 217097 Charlotte, NC 28221
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Gaertner:
In accordance with our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency (CDF) estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
The evaluation results indicate an industry average SBO CDF (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from
J.P. Gaertner approximately 1980 through the present, which show a downward trend from a high of 2.0 x 10-5/rcry to the present value. This historical decrease in estimated SBO CDF is probably the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO CDF for U.S. commercial NPPs.
Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated
February 11, 2005 Mr. Gordon Bischoff, Manager Owners Group Program Management Office Mail Stop 5-16 P.O. Box 355 Pittsburgh, PA 15230-0355
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Bischoff:
In accordance with our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency (CDF) estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
The evaluation results indicate an industry average SBO CDF (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from approximately 1980 through the present, which show a downward trend from a high of
G.C. Bischoff 2.0 x 10-5/rcry to the present value. This historical decrease in estimated SBO CDF is probably the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO CDF for U.S. commercial NPPs.
Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated
February 11, 2005 Mr. Jerald Holm, Director of Regulatory Affairs B&W Owners Group Services Framatome Technologies, Inc.
3315 Old Forest Road P.O. Box 10935 Lynchburg, VA 24506-0935
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Holm:
In accordance with our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency (CDF) estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
The evaluation results indicate an industry average SBO CDF (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from
J. Holm approximately 1980 through the present, which show a downward trend from a high of 2.0 x 10-5/rcry to the present value. This historical decrease in estimated SBO CDF is probably the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO CDF for U.S. commercial NPPs.
Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated
February 11, 2005 Mr. Jack A. Gray, Jr.
Regulatory Response Group Chairman BWR Owners Group Entergy Nuclear Operations, Inc.
440 Hamilton Avenue, Mail Stop 12C P.O. Box 5029 White Plains, NY 10601-5029
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Gray:
In accordance with the our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
J.A. Gray The evaluation results indicate an industry average SBO core damage frequency (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from approximately 1980 through the present, which show a downward trend from a high of 2.0x10-5/rcry to the present value. This historical decrease in estimated SBO core damage frequency is probably the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO core damage frequency for U.S.
commercial NPPs. Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated
February 11, 2005 Mr. Frank J. Rahn, Manager Risk-Based Prioritization Electric Power Research Institute 3412 Hillview Avenue Palo Alto, CA 94304-1395
SUBJECT:
REQUEST FOR PEER REVIEW OF DRAFT REPORT ENTITLED, STATION BLACKOUT RISK EVALUATION FOR NUCLEAR POWER PLANTS
Dear Mr. Rahn:
In accordance with the our peer review process, we are offering you the opportunity to review and comment on the enclosed draft report entitled, Station Blackout Risk Evaluation for Nuclear Power Plants. This contractor-prepared NUREG-series report documents core damage frequency estimates associated with station blackout (SBO) scenarios. The results presented in the enclosed report will support a reevaluation of the adequacy of regulations related to electrical power for the safe operation of nuclear power plants. We would appreciate receiving your comments within 45 days after you receive this letter.
The NRC sponsored this study to achieve the following objectives:
Update the LOOP frequency estimates and nonrecovery probabilities using the latest LOOP event information.
Calculate SBO risk (in terms of core damage frequency) with updated SPAR models for a spectrum of plants.
The NRC addressed the first objective in a draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which was sent to you for comment on December 6, 2004. The enclosed report addresses the second of these objectives.
The enclosed report presents the current estimated core damage risk associated with SBO scenarios for internal events at all 103 operating U.S. commercial NPPs. In conducting the reported evaluation, the researchers evaluated risk only for internal events during critical operation; thus, the evaluation did not address the risks associated with either shutdown operation or external events. To evaluate core damage risk, the researchers used the standardized plant analysis risk (SPAR) models, which the NRC developed for the Nations 103 operating plants. The researchers also augmented the existing SPAR models by adding an extensive set of enhancements to provide up-to-date modeling of LOOP and SBO risk. In addition, the researchers reevaluated emergency diesel generator performance using recent data to establish current reliability levels.
The evaluation results indicate an industry average SBO core damage frequency (point estimate) of 2.9x10-6 per reactor critical year (rcry). This report compares those results with historical estimates from approximately 1980 through the present, which show a downward trend
F. J. Rahn from a high of 2.0x10-5/rcry to the present value. This historical decrease in estimated SBO core damage frequency is probably the result of many factors, including plant modifications in response to the SBO rule, improvements in plant risk modeling, and improved component performance. However, the major contributing factor for this historical decrease appears to be improved emergency diesel generator performance.
The enclosed report also documents several sensitivity studies. As expected, SBO CDF is sensitive to emergency diesel generator performance. In addition, the companion draft report entitled, Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1986 - 2003, which the NRC issued for public comment on December 17, 2004, identified a significantly higher LOOP frequency during the summer months (May - September). (See the related notice in the Federal Register, Vol. 69, No. 242, page 75570.) As a result, the potential effects of allowing 14-day outages for emergency diesel generators (which are assumed to occur approximately once every 36 months) are highly dependent upon when such outages occur. If such outages occur only during the summer months, the annual average SBO CDF is about 75% larger than the baseline annual average SBO CDF. However, if such outages are limited to the non-summer months, the corresponding annual average SBO CDF is approximately 5%
higher than the baseline.
Overall, the study succeeded in evaluating the risk of SBO core damage frequency for U.S.
commercial NPPs. Strengths of the study are the use of the SPAR models to cover all 103 plants and the review of recent emergency diesel generator performance.
If you have any questions regarding this report, please contact Dr. Dale M. Rasmuson at (301) 415-7571 or by email to DMR@nrc.gov.
Sincerely,
/RA/
Charles E. Ader, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research
Enclosure:
As stated