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JUN 21 W34 MEMORANDUM FOR:
D. Eisenhut, Director, DL R. Vollmer, Director, DE
- R. Mattson, Director, OSI H. Thompson, Director, OHFS FROM:
Themis P. Speis, Director Division of Safety Technology
SUBJECT:
REVIEW OF THE SEABROOK STATION PROBABILISTIC SAFETY. ASSESSMENT A Probabilistic Safety Assessment (PSA) for the Seabro6k Station Nuclear Power Plant was voluntarily performed and submitted to NRC by Public Service Company of New Hampshire, an OL applicant.
The Reliability and Risk Assessment Branch _(RRAB), Division of Safety Tec.h.no_ logy, has the responsibility for the overall coordination.of the review effort with the support of Lawrence Livermore Na.tional Laboratory contracted to review the front-end
.. (accident initiation through plant damage state) portion of the PSA.
' In view o the' circumstances under which this PSA was submitted and the current status of the licensing of the Seabrook Station, the purpose and focus of this review will vary in some ways from-ongoing and previous reviews of probabilistic safety assessments. To elaborate, due t'o the voluntary nature of the decision to perform and submit a PSA for Seabrook, a strictly narrow focus of verifying the accuracy of the numbers presented by extensive requantification or phenomenological analyses would not be an appropriate use of. review resources.
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l Primary foci, as in other reviews, would remain.to be the identification of significant vulnerabilities or weaknesses in design and proposed operation that may not have been considered in deterministic analyses, the identification of significant safety issues that may have generic implications, and the identification of any major problems that would be expected to significantly affect the results of the analysis and the safety of the plant.
These conclusions will then be dealt with in accordance with NRR Office Letters No. 40, No. 39, and'No. 16, Revision 1.
In addition, the Seabrook PSA represents one of the latest PS'As which has incorporated lessons learned from past studies and advancements in the state-of-the-art of probabilistic safety analyses.
An emphasis of the review should be to glean any new information that may be useful or affect the reviews of specific safety issues or other programs.
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The possibility of the PSA beingiused in the Phase II hearings for the Seabrook Station should be kept in mind.
The hearings are expected to take place'in late CY 1984/early'1985.
The issue of. emergency planning is
- expected to be a prominent part of these hearings which is a likely area where there may be use' of risk assessment results.
The schedule for this review-calls for preliminary findings being submitted to RRAS by October 15, 1984.
Enclosed with'this memo is a delineation of portionsofthePSAtobereviewedbythedesjgnateddivisions(s)with guidance as-to the type of review being requested.
We would like to have
'i any questions on.significant areas for transmittal to LLNL for consideration in their' review, or if needed, to~ be discussed with the applicant, by -
August 1, 1984 so that resolution and incorporation in the preliminary report froni LLNL will take place (s'early as possible in order to expedite the finalization of the review document-In consideration of the circumstances and nature of this review, we are planning on only one site visit.
The date
.of this visit must be coordinated with all necessary participants, (i.e., contractors,. subcontractors and reviewers) so as to minimize the burden of ti_me and resources expend.ed on this. review by the utility. We'would also
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like to emphasize that there be close, coordination between the front-end and
-back and reTiewers'in DST and'DSI and respective contractors so that t7ie
' final review'will be a cohesive, integrated ass'essilient of the Seabrook St'ation.'
The Division of Engineering will support RRAB in overseeing the review effort
'by LLNL on external events.
The final product of the review will be in the foriii of a NUREG/CR.
There remains the possibility of SERs or testimony being~ required in support of the licensing of Seabrook.
Sarah.M. Davis, of RRAB is the coordinator for the Seabrook PSA Review.
Ms. Davis'can be-contacted on X27546.
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03IGINAL SIGNED M Themis P. Speis, Director Division of Safety Technology
Enclosure:
Distribution Proposed Review Schedule Central File DST CHR0ll RRAB Rdg S. Davis Davis CHRON R.. Fra hm A. Thadani F. Rowsome AD/T Rdg T. Speis 4
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. OFFICIAL RECORD COPY
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Proposed Schedule
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LLNL -
Review through plant damage state Identification of' major errors or inconsistencies.
Estimation of impact on dominant accident sequences and revised estimates where appropriate.
Summary of results, review conclusions', and major insights gained.
10/15/84 Draft Report Internal NRC. Review OST -
Review to core damage state, Gerieric Safety Issues (medium and high priority), potential new GSIs, and overall coordination.
051 -
Crit'ique.of the containment failure analysis identifying strengths and weaknesses of_ containment design-and critique of release category-astignment. - Provide major insights in this area and any significant variations in the conditional failure probabilities and release fractions.
A brief review of
.. consequence analysis should also be performed.
Based on the results of the consequench rev.iew, centainment failure conditional probabilities, and release fractions, limited con' sequence analysis may be needed.
10/15/84 Oraft Report (Critique and Conclusions)
DE -
Support in overseeing the contractor review of external events.
Please provide a critique of the external events analyses (e.g.,
seismii:,' fire', etc.) contained in the Seabr~ook PRA with, the appropriate support from other Branches / Divisions (e.g., ASB, METB,.etc.).
Any questions or comments to be contractor should be formulated and submitted, transmitted to the to.RRAB by August 1, 1984.
10/15/84 Draft Report'(Critique and Conclusions)
Other -
Upon receipt of the contractor report (10/15/84), we will request Support review support and limited calculations where appropriate from other Divisions and Branches in areas of their expertise, especially for those areas where reestimates were made which affect the set of dominant sequences and overall results of the PRA.
Designation of specific sections to be reviewed will be transmitted to ea'ch Branch / Division at that time.
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