ML19327A063
| ML19327A063 | |
| Person / Time | |
|---|---|
| Issue date: | 07/17/1980 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Plesset M Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-GENERAL, TAC-10985, NUDOCS 8008010115 | |
| Download: ML19327A063 (3) | |
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P00R QUAUTY PAGES Distribution:
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E. Case J. Meyer A. Ferguson W. Dircks PPAS D. Eisenhet T. Schultze jy( 17 jggg E. K. Cornell B. Snyder G. Zech E. Telford MEMORANDUM FOR: Milton S. Plesset, Chairman Advisory Consnittee on Reactor Safeguara FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation THRU:
William J. Dircks Acting Executive Director for Operations:gr.dWJ!iam L Di:ds
SUBJECT:
THE FACTORING OF QUANTITATIVE ESTIMATES INTO SEISMIC SAFETY EVALUATION Regarding your memorandum of June 10, 1980 on the above subject, the staff is beginning development of a probabilistic rationale for estimating risk due to earthquakes. It is clear that we will not be able to convert all of the uncer-tainties associated with acceleration, frequency, ground displacement, lique-faction and butiding and equipnent response into a single, uncontroverted, decision methodology. However, it is hoped that we can eventually do a reason-able job of improving the bases and understandability of prudent and technically sound decisions in these areas.
We are making limited use of probabilistic methods in conjunction with the more traditional empirical-detensinistic methodologies.~ For_ example, in the GETR review probabilistic estimates were used to suppleent classical geological methodologies and judgments with respect to fault evaluations.
In the Sequoyah review probabilistic estimates were used to help assess the relative signiff-cance of differences in ground motion levels determined from different non-probabilistic methodologies. In the Systematic Evaluation Program a probabilistic study aimed at establishing seismic hazard at older nuclear power plants is being used along with non-probabilistic methodologies in defining suggested ground motion levels for plant reevaluations. The study incorporates the diverse opinions of highly qualified seismologists and wide ranging sensitivity studies.
The first two volines will appear within two months as NUREG/CR-1582.
It is anticipated that we should be able to brief the Subconwiittee on Extrane External Phenemana on our progress in this area sometime near the end of Septaber. At the same time, we will brief the Subcomunittee on our recommended I
position regarding plants that do not have seismically qualified auxiliary feed-water systems, or some other seismically qualified method of residual heat 3
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j MEMORANDUM FOR: Milton S. Plesset, Chairman
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Advisory Connittee on Reactor Safeguards FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation l
THRU:
William J. Dircks Acting Executive Director for Operations
SUBJECT:
THE FACTORING OF QUANTITATIVE ESTIMATES }NTO SEISMIC SAFETY EVALUATION Regarding your memorandum of June 10, 1980, on the above subject, the staff is beginning development of a probabilistic rationale or estimating risk due to earthquakes. It is clear that we will not be abl to convert all of the uncer-tainties associated with acceleration, frequency ground displacement, lique-faction and building and equipment response int a single, uncontroverted, decision methodology. However, it is hoped thdt we can eventually do a reason-able job of improving the bases and understa ability of prudent and technically sound decisions in these areas.
It is anticipated that we should be able, brief the Subcommittee on Extreme External Phenomena on our progress in s area sometime near the end of Septanber. At the same time, we will ief the Subconnittee on our recommended position regarding plants that do no ve seismically qualified auxiliary feeo-water systems, or some other seismi lly qualified method of residual heat renoval, which was the subject of ther June 10 ACRS letter.
Harold R. Denton, Director
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,0 June 10, 1980 Mr. William J. Dircks, Acting Executive Director for Operations V. S. Nuclear Regulatory Commission Washington, DC 20555
SUBJECT:
THE FACTORING 0F QUANTITATIVE ESTIMATES INTO SEISMIC SAFETY EVALUATION
Dear Mr. Dircks:
In recent reviews of the seismic safety of reactors, including LACBWR and GETR, the Regulatory Staff and/or the Applicant have included probabilistic estimates of the safe shutdown earthquake, permanent fault displacement, liquefaction, etc. The Committee wishes to encourage such efforts. However, in connection with the development of such quantitative estimates, the ACRS believes it is appropriate to develop a rationale for including them in the decision making process in some consistent way.
The matter was discussed with members of the Regulatory Staff at the Subcom-mittee meeting on Extreme External Phenomena held on June 4,1980.
The ACRS would appreciate learning what basis the Staff is developing in regard to this matter.
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Sincerely, Milton S. Plesset Chairman 8008010lN
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