ML003716123

Request for Review of Report Entitled Assessment of Risk Significance Associated with Issues Identified at D.C. Cook Nuclear Power Plant

ML003716123
Person / Time
Issue date:	05/05/2000
From:	Sunil Weerakkody Office of Nuclear Regulatory Research
To:	Ralph Beedle, Drake A, Lochbaum D, Marston T, Solymossy J Electric Power Research Institute, Institute of Nuclear Power Operations (INPO), Nuclear Energy Institute, Union of Concerned Scientists, Westinghouse
References
Download: ML003716123 (11)

Text

Mr. Andrew Drake, Project Manager Westinghouse Owners Group Westinghouse Electric Corporation Mail Stop ECE 5-16 P.O. Box 355 Pittsburgh, PA 15230-0355

SUBJECT:

REQUEST FOR REVIEW OF REPORT ENTITLED ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT Attached for your information and review is the draft report entitled ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT. This report documents the assessment of the risk significance of 141 issues identified at the Donald C. Cook Nuclear Plant, Units 1 and 2 (Cook) since August 1997.

The Operating Experience Risk Analysis Branch of the office of Nuclear Regulatory Research (RES) conducted this assessment as part of the agencys Accident Sequence Precursor (ASP)

Program. In performing this assessment, the RES staff applied the ASP methodology to estimate the risk significance associated with each issue as well as the integrated risk significance associated with the combined issues.

Out of 141 issues analyzed, five issues were identified to be potential accident sequence precursors. The preliminary estimate of the total change in core damage frequency (ÿCDF) resulting from all issues identified at Cook was approximately 4.7x10-4/year for each of the Cook units. The risk significance of the combined impact of all containment-related issues was determined to be small. We plan to finalize the above findings after addressing internal and external peer review comments.

Several high-energy line break (HELB) related issues, degraded seismic capacities, and potential pressure locking conditions in two motor-operated valves were the dominant contributors to the core damage frequency (CDF) increase. The postulated HELB scenarios contributed a ÿCDF of 3.9x10-4/year. The CDF increase attributed to the degraded seismic capacity of block walls and the degraded seismic capacity of the emergency service water pump backwash system was also a dominant contributor, which contributed a ÿCDF of approximately 4.2x10-5/year. The medium and large loss of coolant-accident (LOCA) sequences associated with the potential pressure locking conditions in the motor-operated valves located in the suction path to the residual heat removal pumps from the containment recirculation sump contributed a ÿCDF of 3.6x10-5/year.

Multiple Addressees 2 In accordance with our peer review process, prior to the distribution of the final report, we want to provide you with the opportunity to review and comment on the attached draft report. In order to meet our planned publication schedule, we would appreciate receiving your comments within 60 days from receipt of this letter.

A copy of this draft report and letter are being placed in the Public Document Room at 2120 L Street NW, Washington, DC 20555.

If you have any questions related to this report, please contact Dr. Sunil Weerakkody of my staff at 301-415-6374 or e-mail: sdw1@nrc.gov.

Sincerely, Thomas L. King, Director Division of Risk Analysis and Applications Office of Nuclear Regulatory Research

Attachment:

As stated cc w/o att:

A.Thadani, RES M. Federline, RES S. Collins, NRR R. Zimmerman, NRR B. Sheron, NRR

Multiple Addressees 3 MEMORANDUM DATED: / /00

SUBJECT:

REQUEST FOR REVIEW OF REPORT ENTITLED ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT Distribution w/att.:

OERAB RF DRAA RF File Center Public IDENTICAL LETTERS Mr. Andrew Drake, Project Manager Dr. Theodore U. Marston Westinghouse Owners Group Vice President and Chief Nuclear Officer Westinghouse Electric Corporation EPRI Mail Stop ECE 5-16 3412 Hillview Avenue P.O. Box 355 Palo Alto, CA 94304 Pittsburgh, PA 15230-0355 Mr. Ralph E. Beedle Mr. David A. Lochbaum Senior Vice President and Chief Nuclear Officer Union of Concerned Scientists Nuclear Generation Division 1616 P Street, N.W.

Nuclear Energy Institute Suite 310 1776 I Street N.W. Washington, D.C. 20035-1495 Suite 400 Washington, D.C. 20006-3708 Mr. Joseph M. Solymossy Director of Project Services Institute of Nuclear Power Operations 700 Galleria Parkway, NW Atlanta, GA 30339-5957 DOCUMENT NAME: A:\EXT-REVIEW-COOK.WPD To receive a copy of this document, indicate in the box: C = Copy wo/encl E = Copy w/encl N = No copy OFFICE OERAB OERAB OERAB OERAB NAME SWeerakkody SMays PBaranowsky TKing DATE / /00 / /00 / /00 / /00 OFFICIAL RECORD COPY (RES File Code) RES 2C-3 Accession Number: ML003716123 Template Number: RES-006

Dr. Theodore U. Marston Vice President and Chief Nuclear Officer EPRI 3412 Hillview Ave.

Palo Alto, CA 94304

SUBJECT:

REQUEST FOR REVIEW OF REPORT ENTITLED ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT Attached for your information and review is the draft report entitled ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT. This report documents the assessment of the risk significance of 141 issues identified at the Donald C. Cook Nuclear Plant, Units 1 and 2 (Cook) since August 1997.

The Operating Experience Risk Analysis Branch of the office of Nuclear Regulatory Research (RES) conducted this assessment as part of the agencys Accident Sequence Precursor (ASP)

Program. In performing this assessment, the RES staff applied the ASP methodology to estimate the risk significance associated with each issue as well as the integrated risk significance associated with the combined issues.

Out of 141 issues analyzed, five issues were identified to be potential accident sequence precursors. The preliminary estimate of the total change in core damage frequency (ÿCDF) resulting from all issues identified at Cook was approximately 4.7x10-4/year for each of the Cook units. The risk significance of the combined impact of all containment-related issues was determined to be small. We plan to finalize the above findings after addressing internal and external peer review comments.

Several high-energy line break (HELB) related issues, degraded seismic capacities, and potential pressure locking conditions in two motor-operated valves were the dominant contributors to the core damage frequency (CDF) increase. The postulated HELB scenarios contributed a ÿCDF of 3.9x10-4/year. The CDF increase attributed to the degraded seismic capacity of block walls and the degraded seismic capacity of the emergency service water pump backwash system was also a dominant contributor, which contributed a ÿCDF of approximately 4.2x10-5/year. The medium and large loss of coolant-accident (LOCA) sequences associated with the potential pressure locking conditions in the motor-operated valves located in the suction path to the residual heat removal pumps from the containment recirculation sump contributed a ÿCDF of 3.6x10-5/year.

Mr. Ralph E. Beedle Senior Vice President and Chief Nuclear Officer Nuclear Generation Division Nuclear Energy Institute 1776 I Street N.W.

Suite 400 Washington, D.C. 20006-3708

SUBJECT:

REQUEST FOR REVIEW OF REPORT ENTITLED ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT Attached for your information and review is the draft report entitled ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT. This report documents the assessment of the risk significance of 141 issues identified at the Donald C. Cook Nuclear Plant, Units 1 and 2 (Cook) since August 1997.

The Operating Experience Risk Analysis Branch of the office of Nuclear Regulatory Research (RES) conducted this assessment as part of the agencys Accident Sequence Precursor (ASP)

Program. In performing this assessment, the RES staff applied the ASP methodology to estimate the risk significance associated with each issue as well as the integrated risk significance associated with the combined issues.

Out of 141 issues analyzed, five issues were identified to be potential accident sequence precursors. The preliminary estimate of the total change in core damage frequency (ÿCDF) resulting from all issues identified at Cook was approximately 4.7x10-4/year for each of the Cook units. The risk significance of the combined impact of all containment-related issues was determined to be small. We plan to finalize the above findings after addressing internal and external peer review comments.

Several high-energy line break (HELB) related issues, degraded seismic capacities, and potential pressure locking conditions in two motor-operated valves were the dominant contributors to the core damage frequency (CDF) increase. The postulated HELB scenarios contributed a ÿCDF of 3.9x10-4/year. The CDF increase attributed to the degraded seismic capacity of block walls and the degraded seismic capacity of the emergency service water pump backwash system was also a dominant contributor, which contributed a ÿCDF of approximately 4.2x10-5/year. The medium and large loss of coolant-accident (LOCA) sequences associated with the potential pressure locking conditions in the motor-operated valves located in the suction path to the residual heat removal pumps from the containment recirculation sump contributed a ÿCDF of 3.6x10-5/year.

Mr. David A. Lochbaum Union of Concerned Scientists 1616 P Street, N.W.

Suite 310 Washington, D.C. 20035-1495

SUBJECT:

REQUEST FOR REVIEW OF REPORT ENTITLED ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT Attached for your information and review is the draft report entitled ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT. This report documents the assessment of the risk significance of 141 issues identified at the Donald C. Cook Nuclear Plant, Units 1 and 2 (Cook) since August 1997.

The Operating Experience Risk Analysis Branch of the office of Nuclear Regulatory Research (RES) conducted this assessment as part of the agencys Accident Sequence Precursor (ASP)

Program. In performing this assessment, the RES staff applied the ASP methodology to estimate the risk significance associated with each issue as well as the integrated risk significance associated with the combined issues.

Out of 141 issues analyzed, five issues were identified to be potential accident sequence precursors. The preliminary estimate of the total change in core damage frequency (ÿCDF) resulting from all issues identified at Cook was approximately 4.7x10-4/year for each of the Cook units. The risk significance of the combined impact of all containment-related issues was determined to be small. We plan to finalize the above findings after addressing internal and external peer review comments.

Several high-energy line break (HELB) related issues, degraded seismic capacities, and potential pressure locking conditions in two motor-operated valves were the dominant contributors to the core damage frequency (CDF) increase. The postulated HELB scenarios contributed a ÿCDF of 3.9x10-4/year. The CDF increase attributed to the degraded seismic capacity of block walls and the degraded seismic capacity of the emergency service water pump backwash system was also a dominant contributor, which contributed a ÿCDF of approximately 4.2x10-5/year. The medium and large loss of coolant-accident (LOCA) sequences associated with the potential pressure locking conditions in the motor-operated valves located in the suction path to the residual heat removal pumps from the containment recirculation sump contributed a ÿCDF of 3.6x10-5/year.

Mr. Joseph M. Solymossy Director of Project Services Institute of Nuclear Power Operations 700 Galleria Parkway, NW Atlanta, GA 30339-5957

SUBJECT:

REQUEST FOR REVIEW OF REPORT ENTITLED ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT Attached for your information and review is the draft report entitled ASSESSMENT OF RISK SIGNIFICANCE ASSOCIATED WITH ISSUES IDENTIFIED AT D.C. COOK NUCLEAR POWER PLANT. This report documents the assessment of the risk significance of 141 issues identified at the Donald C. Cook Nuclear Plant, Units 1 and 2 (Cook) since August 1997.

The Operating Experience Risk Analysis Branch of the office of Nuclear Regulatory Research (RES) conducted this assessment as part of the agencys Accident Sequence Precursor (ASP)

Program. In performing this assessment, the RES staff applied the ASP methodology to estimate the risk significance associated with each issue as well as the integrated risk significance associated with the combined issues.

Out of 141 issues analyzed, five issues were identified to be potential accident sequence precursors. The preliminary estimate of the total change in core damage frequency (ÿCDF) resulting from all issues identified at Cook was approximately 4.7x10-4/year for each of the Cook units. The risk significance of the combined impact of all containment-related issues was determined to be small. We plan to finalize the above findings after addressing internal and external peer review comments.

Several high-energy line break (HELB) related issues, degraded seismic capacities, and potential pressure locking conditions in two motor-operated valves were the dominant contributors to the core damage frequency (CDF) increase. The postulated HELB scenarios contributed a ÿCDF of 3.9x10-4/year. The CDF increase attributed to the degraded seismic capacity of block walls and the degraded seismic capacity of the emergency service water pump backwash system was also a dominant contributor, which contributed a ÿCDF of approximately 4.2x10-5/year. The medium and large loss of coolant-accident (LOCA) sequences associated with the potential pressure locking conditions in the motor-operated valves located in the suction path to the residual heat removal pumps from the containment recirculation sump contributed a ÿCDF of 3.6x10-5/year.

Date 5/2/00 ROUTING AND TRANSMITTAL SLIP TO: (Name, office symbol, room #, building, agency/post) Initials Date

1. S. Weerakkody - Concur

2. S. Mays - Concur

3. P. Baranowsky - Concur

4. T. King - Concur/Signature 5.

6.

7.

8.

9.

10.

Action File Note and Return Approval For Clearance Per Conversation As Requested For Correction Prepare Reply Circulate For Your Information See Me Comment Investigate X Concurrence/Signature Coordination Justify REMARKS Identical Letters.

Room # - Bldg.

FROM: (Name, org. symbol, Agency/Post)

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