ML20211K540
| ML20211K540 | |
| Person / Time | |
|---|---|
| Issue date: | 12/01/1986 |
| From: | Speis T Office of Nuclear Reactor Regulation |
| To: | Bernero R, Miraglia F, Novak T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20209C630 | List: |
| References | |
| FOIA-87-10 NUDOCS 8612110281 | |
| Download: ML20211K540 (4) | |
Text
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DEC 1 56 MEMORANDUM FOR: Robert M. Bernero, Director Division of BWR Licensing Frank J. Miraglia, Director Division of PWM Licensing B Thomas M. Novak Deputy Director Division of PWR Licensing A FRCM: Themis P. Spels, Director Division of Safety Review & Oversight
SUBJECT:
GENERIC REQUIREMENTS FOR INDIVIUUAL PLANT EXAMINATIONS tnclosed for your coments is a Draft Generic Letter for Individual Plant txaminations for existing plants. The requirements specified in the urart Generic Letter have been developed to fulfill the position stated in the Comission's Severe Accident Policy Statement.
The Guidelines and Criteria for tne BWR Mark I and III containments and for the PWR Ice t.ondenser containment have been distributed unoer separate cover. The Guidelines and Criteria for the BWR Mark II and PWR Large Dry containments will be distributed shortly.
The Draft Generic letter, incorporating your coments, wil De provided to the ACRS staff on December 5,198b, for discussions with the Severe Accident (Class 9) Subcomittee on December 19, 1986. To meet this schedule your ccmments will be needed by December 3. A CRGR review is planned for January IW and a full ACRS review is planned for February 1987. Pricr to distribution for industry and puolic coment in March 1987, the letter will again De circulated for your cement. Please provide your comments in time to support this schedule. i n .
Themis P. Speis, Director Division of Safety Review & Oversight l
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DRAFT GENERIC LETTER All Holders of Operating Licenses and Construction Permits TO:
Gentlemen:
SUBJECT:
INDIVIDUAL PLANT EXAMINATIONS FOR SEVERE ACCIDENT VULNERABILITIES Severe accidents dominate t.he risk to the public associated with nuclear power plant accidents. The Commission issued a policy statement on severe accidents on August 8, 1985, 50 FR 32138. The objectives of the policy are (1) to
- reduce the probability of a severe accident, and g) shculd a severe The Policy accident Statement occur, to mitigate its consequences to the puolic.
applies to coth future plants and existing plants, whicn include those plants currently holding a construction pemit. Available information led the Comission to conclude that existing plants pose no undue risk to the public health and safety and see no present basis for icinediate action on generic rulemaking or other regulatory changes for these plants. The Consnission was convinced, however, of the need for a systematic examination of existing plants and plants holding active construction permitsPlantsto identify any witn inactive plant-specific vulnerabilities to severe accidents.
construction pemits will be handled in accordance with the Policy Statement provisions.
An Individual Plant Examination (IPE) is to be a systematic examination of the systems, components and human actions as initiators of severe Theaccicents, options or as contributers tcward the consecuences of severe accidents.
available to the individual plant in performing the examination have been developed with tha goal of achieving uniformity in the examinations among the existing plants. 5e options and tne secpe described below will allow for, and determine, tr ffects of significant individual safety features and concerns while providing a reasonably complete assessment of severe accident nazards. A two fold examination is envisioned. First, a prevention assessment looking at design and cperation of tne plant is to be performed to determine the core damage frequencies. Second, a mitigation assessment looking at cesign and emergency actions is to be performed to detemine the containment performance. This two fala examination will, while maintaining and supporting the concept of defense-in-depth, achieve a balance in the considerations of accident prevention and mitigation. The results of these examinations are to be measured against the applicable Guidelines and Criteria attached, or the equivalent therecf. and the Comission's Safety Goals Policy Statement.
Severe Accident vulnerabilities, for this examination, are the absence of any preventive or mitigating factor, be it hardware, human action or procedure,For that leads to unacceptable core melt frequencies or containment failure. Current the purpose of this study, only internal vulnerabilities are sought.
risk assessments indicate that risk from external events could be a major
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2 e contributor. The position of the NRC staff, and its basis, has been explained in SECY 86-162, " Treatment of External Events in the Implementation of the Severe Accident Policy Statement." The NRC reccgnizes that while FRAs have been performed which incluoe external as well as internal events, Shouldthethe10COR-licensee IPEM in its present form is limited to internal events.
determine that it is preferable to proceed directly to an IPE that considers external events, the NRC staff will be available to discuss the methods, assumptions and approach to be used throughout the course of the examination.
Five options are considered to be acceptable to satisfy the examination requirements. First, previously performed PRAs may be utilized, provided they have been performed at least at level II or III with appropriate updates.
Second, the approved 10COR-IPEM may be applied. Third, previous PRAs pertomed at level I and supplemented by the appropriate IPEM parts, or equivalents, may be applied. Fourth, simplified, or " Phase I" PRAs may be applied with prior NRC approval. Fifth, otherThesystematic NRC's staffevaluation approval of methods the may be applied with prior NRC approval.
applicable IDCOR-IPEM, which was developed by the industry to meet tne intent of the Commission's Policy Statement, and evaluation of the applicable reference plant are included in the appendices to this letter.
An IPE for existing plants using an acceptable method is required to comply with the Severe Accident Policy Statement implementation. The implementation is understood to include as a part of the examination: (1) visual examination of the plant systems for potential vulnerabilities, (2) review of postulated events cerived from known precursors to severe accioents, (3) incorporation of an up-to-cate data base using data unique to the design teatures of the plant, (4) methodology management sufficient to insure proper verification and validation or cata used and analysis techniques, (5) review of equipment survivability in postulated post accident environments, and (6) development of fault trees and event trees sutticient to identify vulnerabilities for the plant. The details of the examination and the results are to be measured against guidelines and criteria applicable to the plant.
The IPE is to be documented to provide the basis for the findings in a traceable manner. The minimum level of reporting is as tollows: (1) certification that an IPE has been completed as requested and in compliance i
with the provisions contained in this generic letter. (2) Ine results submitted for review are to be comparisons with the Guidelines and Criteria and the Comission's Safety Goals Policy Statement. (3) The cominant secuences for the plant are to be identified. (4) Should severe accident vulnerabilities be discovered, they are to be identified and described along with proposed actions a.10 schedules for remedial actions. If no action is proposed, a justification is to be provided. (5) The accident management program for the plant is to be provided. This is to address the accident
' management strategy, the organizational structure and responsibilities, emergency operating procedures, training of personnel ano availability and reliability of needed instrumentation ano equipment. All documentation pertaining to the examination must be retained by tne licensee in an auditable fom for tne life of the plant.
3 The submitted results will be reviewed and evaluated by the NRC. Any NRL required plant modifications will be analyzed according to the backfit rule, 10 CFR 50.109. Generic backfits, if any, will be proposed via rulemaking.
The industry, via organizations such as INPO, is encouraged to perform audits of the plant evaluations.
The incividual plant examinations are to be performea in conformance with the rollowing schedules.
- 1. Plants with existing PRAs (Level II or III) anc IPEM test cases -
8 to 14 montns atter receipt of this lett?r.
- 2. Other plants - 14 to 20 months after receipt of this letter.
Utilities are requested to submit actual schedules for completion of the individual plant examinations within 60 cays of receipt of this letter.
Meetings with utility representatives will be scheduled in each Region shortly. Quarterly meetings at NRC Heacquarters are planned during the examinations to ciscuss subjects raised by licensees and to provide necessary clarifications.
Reference plants representing five generic containment contigurations (BWR Mark I, II and III, PWR Ice Condenser and PWR Large Dry) were selected for examination in preparation of the NRC's Reactor Risx Reference Document and l
Tor test application of the IDCOR-IPEM. The NRC prepared Guidelines and Criteria applicable to each of these five generic containment configurations based the examinations of these plant types.
Attached to this generic letter are the applicable NRC preparec Guidelines and criteria the approval of the applicable IDCOR-IPEM, and hRC evaluation of the applicable Reference Plant (xamination. These attachrents are supplied for use in the IPE or as guidance in development of equivalent examination bases.
This letter is issued pursuant of 10 LFR 50.54(f). Accordingly, all responses should be under oath or affirmation.
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