ML20028D337
| ML20028D337 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 01/11/1983 |
| From: | Ray J Advisory Committee on Reactor Safeguards |
| To: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20028D338 | List: |
| References | |
| NUDOCS 8301180540 | |
| Download: ML20028D337 (2) | |
Text
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NUCLEAR REGULATORYCOMMISSION 5~
.I ADVISORY COMMITTEE ON REACTOR SAFEGUARDS c,, i.f4 g
WASHINGTON, D. C. 20555
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.s January 11, 1983, Mr. William J. Dircks Executive Director for Operatioas U.S. Nuclear Regulatory Commission Washington, D. C. 20555
Dear Mr. Dircks:
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SUBJECT:
CLARIFICATION OF COMMENTS IN THE ACRS REPORT ON THE. SYSTEMATIC EVALUATION PROGRAM REVIEW 0F THE MILLSTONE NUCLEAR POWER STATION, UNIT 1 N.. '
During its 273rd meeting, January 6-8, 1983 the Advisory Con)mittee on
. ' Reactor Safeguards briefly discussed with the NRC staff the interpretat' ion of ACRS comments in its December 13, 1982 report regarding the usefulness of plant-specific probabalistic risk assessments in support of the systematic evaluation program (SEP).
Specifically, the following paragraph:
"We have noted in previous' letters on the SEP program that plant specific probabilistic risk assessments (PRA) were not available for use in connection with the Integrated. Assessment.
In this case, a plant-specific PRA for the Millstone'jlant-had been developed as part 9
of the Interim Reliability Evaluation Program (IREP), and the results were used in the assessment of 21 of the issues.
Contrary to our i
previous belief (contained in our August 18, 1982 and May 11,1982 reports on the Ginna and Palisades SEP reviews), it does not ' appear that the plant-specific IREP PRA.for the Millstone plant provided a basis for more definitive assessments than the more limited risk analyses developed for the other pl ants th:t we have reviewed."
l We provide the comments below with respect to this matter.
l l
The statement in the Millstone letter presumably has been inter-preted as saying that plant-specific PRAs are not useful.
This was not our intent; the comment rel ated only to the usefulness of a plant-specific PRA, which lacked treatment of external events, in l
I connection with the very limited set of issues to which it was ap-i plicable for the SEP Phase II as it has been conducted.
Our favor-able views regarding the desirability and usefulness of plant-specific PRAs have been expressed several times in the past.
l In another sense, the statement in the Millstone letter has been interpreted as arguing against the requirement of a National Reli-ability Evaluation Program (NREP) PRA for the plants selected for
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Mr. William J. Dircks 2-
. January 11, 1983 review in Phase III of the SEP.
To some extent this is correct.
If Phase III is to be conducted in essentially the same manner as Phase II, except for a smaller number of topics, it does not seem that it would be cost-effective to require a plant-specific PRA if its only use were to assist in the Integrated Plant Safety-Assess-ment, unless external events are included in the PRA..There.are several reasons for this.
One is that the NREP, like IREP, vill
.not include external events, which have represented some, of the most important differenchs in the SEP plants reviewed to date.
Another reason is that many of the differences from current cri-teria are not in areas addressed by PRAs.
S,incerely, s
J. J. Ray Y Chairman b
.