ML20245C201
| ML20245C201 | |
| Person / Time | |
|---|---|
| Issue date: | 06/29/1987 |
| From: | Murley T Office of Nuclear Reactor Regulation |
| To: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20244D847 | List:
|
| References | |
| FOIA-88-198 NUDOCS 8707060019 | |
| Download: ML20245C201 (6) | |
Text
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MEMORANDUM TOR: Victor Stello, Jr.
Executive Director for Operations FROM: Thomas E. Murley, Director Office of Nuclear Reactor Regulation
SUBJECT:
PROPOSED COURSE OF ACTION ON BWR MARK I CONTAINMENT Your memorandum of April 20, 1987 directed NRR to determine a recommended course of action with regard to earlier proposals for an initiative to enhance BWR containment performance in the event of a severe core damage accident.
The staff has for some time recognized the potential vulnerability of BWR Mark I containments under certain severe accident conditions (see e.g., NUREGs 1079 and 1150) and, as a result, has studied means for reducing the Mark I containment failure probability. Last year the staff developed a set of proposed generic improvements with the general intention of reducing the conditional probability of Mark I containment failure during severe accidents. It was thought that, if these improvements were implemented, it would be unnecessary for these BWR plants to have containment performance evaluated as part of the Individual Plant Examinations (IPE).
In the intervening time since the generic improvements were put forward there have been several discussions among the staff, industry groups and the research comunity. The Reactor Risk Reference Document (NUREG 1150) was l completed in February 1987 as well. The conclusion that seems to have emerged ,
from these activities is that there is no clear consensus on whether the '
Mark I generic improvements are needed, whether the cost estimates are realistic, and whether the proposed improvements would be effective in significantly reducing risks. After reviewing these matters. I have concluded that a more comprehensive approach to this issue should be taken.
l The approach outlined below is not intended to delay clear safety improvements but rather to ensure we look at all reactor types and understand those areas )
where we are most likely to attain safety improvements. I y ~ ~..
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V. Stello, Jr. JUN2910 In examining the broad question of how to reduce the risks of severe accidents, the following three areas must be considered.
- 1. IMPROVED PLANT OPERATIONS Every safety study since WASH 1400 has shown the sensitivity of risk to hurnan errors. Our own analysis of operating experience confirms the importance of reducing maintenance, surveillance, testing and control room errors. Thus, an overall approach to this issue must include a program to improve plant operations and should consider at least the tasks below:
(a) Continued improvement of the SALP program; (b) Regular reviews by senior NRC managers to evaluate those plants that may not be meeting hRC and industry standards of operational performance; (c) Diagnostic Team Inspections to probe further the performance of those plants above; (d) Regulatory actions to improve operational performance where it has fallen below expected standards; (e) Improved Technical Specifications; (f) Continued improvement of Emergency Operating Procedures (EOPs); and (g) Expanding E0Ps to include Severe Accident Procedures.
- 2. COMPREHENSIVE SEARCH FOR SEVERE ACCIDENT VULNERABILITIES The Severe Accident Policy Statement contemplated a program of Individual Plant Examinations (IPEs) that would be a systematic approach to examine all plants for possible significant risk contributors. The staff has ,
i been working with the IDCOR industry group to develop the IPE methodology and has reached conclusion on a proposed program. The IPE program will have to be integrated with the improved operations program and with the containment performance research program below.
- 3. CONTAINMENT PERFORMANCE RESEARCH The assessment of containment performance during severe accidents is a very difficult problem, and years of research have not yielded a consensus on what improvements are needed, if any. We should anticipate there will be the need for a long-range, continuing research program to
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Victor Stello, Jr -3 .".W 2 0 1-R assess the challenges to containments, to evaluate potential improvements, and to continue improving our understanding of source terms. Within this long range program there should be near-term results where the weight of technological evidence supports recommendations for containment improvements. The BWR Mark I would be one area targeted for near-term results. Clearly, this research effort must be integrated closely with the IPE program which will be examining accident vulnerabilities that could threaten containment integrity at specific plants.
The comprehensive program for reducing severe accident risks outlined above has not been fully developed. A schematic portrayal is shown in the attached figure. When developed and implemented I believe the program should lead to closure of the severe accident issue. Nonetheless, elements of the containment performance research program and the improved plant operations program will no doubt extend well into the future as we gain more research knowledge and more operating experience.
In keeping with the intent of the reorganization ttat RES develop resolutions for generic safety matters, I suggest that RES develop, with NRR guidance and support, the overall program outlined above. I further suggest that RES develop an interim response to the Conrnission's request for an options paper (February 9, 1987, memo from Chilk to Stello). This interim response would provide an outline of the program discussed above and would provide schedules for implementing key parts of the program such as IPE and containment performance evaluations. Finally, because of the importance of this issue, I will continue to work closely with the Director, RES, to coordinate the overall guidance for these activities. Similarly, the NRR and RES staffs will work closely on this program.
Original signed by
% u I.Murley Thomas E. Murley, Director Office of Nuclear Reactor Regulation
Enclosure:
As stated Cc w/ encl.
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