ML25168A030
| ML25168A030 | |
| Person / Time | |
|---|---|
| Issue date: | 01/11/1983 |
| From: | Ray J Advisory Committee on Reactor Safeguards |
| To: | Dircks W NRC/EDO |
| References | |
| Download: ML25168A030 (1) | |
Text
UNITED STATES NUCLEAR REGULATOR.Y-COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, D. C. 20555 Mr. William J. Dircks Executive Director for Operations U.S. Nuclear Regulatory Commission Washington, D. C. 20555
Dear Mr. Dircks:
January 11, 1983
SUBJECT:
CLARIFICATION OF COMMENTS IN THE ACRS REPORT ON THE SYSTEMATIC EVALUATION PROGRAM REVIEW OF THE MILLSTONE NUCLEAR POWER STATION, UNIT 1 During its 273rd meeting, January 6-8, 1983 the Advisory Committee on Reactor Safeguards briefly discussed with the NRC staff the interpretation of ACRS colllflents 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 pl ant-specific probabilistic risk assessments (PRA) were not available for use in connection with the lntegrate,d Assessment.
In this case, a plant-specific PRA for the Millstone plant had been developed as part of the Interim Reliability Evaluation Program (IREP), and the results were used in the assessment of 21 of the issues.
Contrary to our 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 pl ant-specific IREP PRA for the Mi 11 stone pl ant provided a basis for more definitive assessments than the more 1 imited risk analyses developed for the other plants that we have reviewed."
We provide the comments below with respect to this matter.
The statement in the Millstone 1 etter presumably has been inter-preted as saying that plant-specific PRAs are not useful.
This was not our intent; the comment related only to the usefulness of a plant-specific PRA, which lacked treatment of external events, in connection with the very limited set of issues to which it was ap-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.
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 1004
Mr. William January 11, 1983 review in Phase I I I 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 Pl ant Safety Assess-ment, unless external events are included in the PRA.
There are several reasons for this.
One is that the NREP, like !REP, will not include external events, which have represented some of the most important differences in the SEP pl ants reviewed to date.
Another reason is that many of the differences from current cri-teria are not in areas addressed by PRAs.
Sincerely,
~CB J. J. Ray '9-Chairman 1005