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NUREG-1742, “Perspectives Gained From the Individual Plant Examination of External Events (IPEEE) Program”; Draft for Comment

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Nuclear Regulatory Commission.


Notice of availability of the draft report for comment NUREG-1742, “Perspectives Gained from the Individual Plant Examination of External Events (IPEEE) Program”.


The Nuclear Regulatory Commission issued on June 28, 1991, Supplement 4 to Generic Letter 88-20, “Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities, 10 CFR 50.54(f).” Associated guidance for conduct of the IPEEEs was issued in June 1991 in NUREG-1407, “Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities.” Specifically, the Nuclear Regulatory Commission requested that each licensee perform an IPEEE to identify and report to the Nuclear Regulatory Commission all plant-specific vulnerabilities to severe accidents caused by external events. This review was limited to plant behavior under full-power operating conditions. The external events to be considered included seismic events; internal fires; and high winds, floods, and other (HFO) external initiating events including transportation or nearby facility accidents and plant-unique hazards. All currently operating nuclear power plants in the United States have completed their assessments and submitted their analyses to the NRC.

Consistent with the intent of Generic Letter 88-20, the primary goal of the IPEEE program has been for each licensee to identify plant-specific vulnerabilities to severe accidents. More specifically, Supplement 4 to Generic Letter 88-20 identified the following four objectives for the IPEEE:

  • To develop an appreciation of severe accident behavior,
  • To understand the most likely severe accident sequences that could occur at the licensee's plant under full-power operating conditions,
  • To gain a qualitative understanding of the overall likelihood of core damage and fission product releases, and
  • To reduce, if necessary, the overall likelihood of core damage and radioactive material releases by modifying, where appropriate, hardware and procedures that would help prevent or mitigate severe accidents.

The primary objective of the NRC's technical review process was to ascertain the extent to which the licensee's IPEEE submittals have achieved the intent of Generic Letter 88-20, satisfied the four principle IPEEE objectives listed above, and followed the recommended guidance in NUREG-1407. The reviews focused on verifying that the critical elements of acceptable IPEEE analyses in the fire, seismic, and HFO areas were performed in accordance with the guidelines in NUREG-1407. Results of the reviews of each IPEEE are documented in plant-specific Staff Evaluation Reports and Technical Evaluation Reports which were transmitted to each licensee and made publically available. It should also be noted that the staff's reviews were not intended to validate or verify the licensees' IPEEEs analyses or results (i.e., an in-depth evaluation of the various inputs, assumptions, and calculations was not performed). Rather, methods, approaches, assumptions, and results were reviewed for reasonableness. If inconsistencies were encountered, they were reported in the plant-specific IPEEE Technical Evaluation Reports.

The draft report NUREG-1742, “Perspectives Gained from the Individual Plant Examination of External Events (IPEEE) Program” summarizes the findings from the review of the licensees' IPEEE submittals. The public is invited to provide feedback on this draft report.

As part of the IPEEE program, some generic issues were addressed by the licensees in their submittals. As noted in draft NUREG-1742, while this has resulted in resolution of most of the generic issues related to the IPEEE program, some aspects of some generic issues were not sufficiently discussed in all submittals to reach a resolution. Those remaining issues will be addressed separately from the IPEEE program.

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This notice serves as a request for public comment on the Nuclear Regulatory Commission's draft report NUREG-1742, “Perspectives Gained from the Individual Plant Examination of External Events (IPEEE) Program,” that is dated April 2001 (web address:​NRC/​NUREGS/​SR1742/​V1/​index.html). Only written comments are requested. Feedback is especially requested on the following specific questions.

1. Does the information contained in NUREG-1742 represent a useful understanding of the potential vulnerabilities of nuclear power plants to external events? How will the information in this report be used by various stakeholders? What would make the information more useful?

2. Are there another comparisons of information from the IPEEE submittals that would yield useful insights? If so, what comparisons would be useful? Why?

3. Given the information from the IPEEE submittals on the risk from fire, seismic and other external events, is additional research needed to improve methods, reduce uncertainties, or resolve issues? If so, what research should be pursued and why? If not, why not?

4. Potential plant improvements, identified by licensees in their Start Printed Page 22270submittals, can be divided into three general categories—improvements that (1) have been completed, (2) will be made, or (3) will receive further consideration. Are there any improvements in either of the last two categories that have been completed and that resulted in a significant change in a plant's ability to withstand potential external events? If so, what are the improvements and the related changes to the plant's capability?

5. How can the results of the IPEEE program be used to (1) maintain safe operations of nuclear facilities; (2) make NRC activities and decisions more effective, efficient, and reliable; (3) increase public confidence; or (4) reduce unnecessary regulatory burden on stakeholders?

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Written comments may be sent to Dr. Alan M. Rubin, Probabilistic Risk Analysis Branch, Division of Risk Analysis and Applications, Office of Nuclear Regulatory Research, Mail Stop T10E50, U.S. Nuclear Regulatory Commission, Washington, DC 20555, or e-mail:

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Submit comments by July 31, 2001. Comments received after this date will be considered if it is practical to do so, but the Commission is able to ensure consideration only for comments received on or before this date.

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Dated this 10th Day of April 2001.

For the Nuclear Regulatory Commission.

Thomas L. King,

Director, Division of Risk Analysis and Applications, Office of Nuclear Regulatory Research.

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[FR Doc. 01-11113 Filed 5-2-01; 8:45 am]