ML20204G533

Requests Info Re Basis for Use of Tau Effect in Establishing Seismic Design Basis.Acrs 830831-0902 Meetings Will Include Discussion of Commissioner 830708 Questions Re Tau Effect. Response Requested by 830825

ML20204G533
Person / Time
Issue date:	08/08/1983
From:	Fraley R Advisory Committee on Reactor Safeguards
To:	Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO)
Shared Package
ML20204G536	List: ML20204G533 ML20207Q719 ML20207Q721 ML20207Q722 ML20207Q723 ML20207Q724 ML20207Q725 ML20207Q727 ML20207Q728 ML20207Q731 ML20207Q732 ML20207Q733 ML20207Q736 ML20207Q738 ML20207Q739 ML20207Q741 ML20207Q742
References
FOIA-86-151, FOIA-86-197 NUDOCS 8309090018
Download: ML20204G533 (1)

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' *d " ' NUCLEAR REGULATORY COMMISSION 5  :. r ADVISORY COMMITTEE ON REACTOR SAFEGUARDS o, [ WASHINGTON, D. C. 20555 gv f August 8,1983 MEMORANDUM FOR: W. J. Dircks Executive Di 7 - for perations FROM: R. F. Fral .xecutive ector, ACRS

, SU6J ECT: COMMISSIONER GIllNSKY'S REQUEST FOR ACRS COMMENTS ON THE USE OF THE TAU EFFECT Comissioner Gilinsky has requested that the ACRS comment on tne tau effect, its scientific and engineering basis, and its use in establishing seismic design basis criteria for nuclear power plants. A copy of Commissioner Gilinsky 's July 8, 1983 letter is attached. The ACRS will De discussing this matter ' during the August 31-September 2, 1983 ACRS meeting and intends to respond to Comissioner Gilinsky's questions at this meeting. To as-sist the ACRS in this matter, the Subcomittee Chairman has requested tnat the NRC Staff provide the ACRS with their written responses to the follow-ing questions by August 25, 1983.

1. From the NRC Staff perspective, what is the scientific basis for the establishment of the existence of and the quantifica-tion of the tau effect? What uncertainties are associated with the use of this methodology in establishing a seismic design basis for or in evaluating tne seismic design margins associated with a _ nuclear power plant?

2. Wnat is the NRC Staff's current position as to the use of the tau effect in establishing a seismic cesign basis for plants other than Diablo Canyon?

Dr. Ricnard Savio will be coordinating the ACRS activities on this for tne ACRS Office. If there is a need for additional discussions, I can be reached on 634-3265 and Dr. Savio can be reached on 634-3267.

Attachment:

Memo for Jeremiah Ray, Chairman, ACRS, from Comissioner Victor .Gilinsky dated 7/8/83 re tau effect cc:

ACRS Members J. P. Knight, AD/CSE M. Licarkin, ACR$

G. Quittsenreiber, ACRS R. Savio, ACRS g%7{6}QCf)j//'

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PE!'.ORANDUM FOR JEREMIAH RAY, CHAIRMAN, ACRS I regret that we did not have an opportunity to discuss the quantification of seismic design margins during our meeting this afternoon. I am particularly interested in the validity of the reductions in a seismic spectrun which fall under the rubric of " tau effect", especially because the Appeal Board's opinion in Diablo Canycn, and the Ccemission's decision not to take review of that opinion, would seem to endorse the application of this technique in other cases. In its July 14, 1978 letter to the Commission, the ACES did not appear to specifically endorse ~this technique but corrented favorably on certain off-setting factors for this already completed plant.

I would like to know whether the tau effect has a sufficiently sound scientific or engineering basis to Justify its use to reduce seismic design standards that apply to nuclear power plants. Should NRC do further research en this question? I would be grateful if the Committee could provide a response within two months, w .w Victor Gilinsky Commissioner cc: Chairman Palladino Commissioner Roberts Commissioner Asselstine SECY OPE _.__

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