ML20203E586

Forwards Rev 1 to 1589.01, Seismic Fragilities of Structures..., PLG-0432, ...Risk Mgt & Emergency... & PLG-0465, ...Emergency Planning Sensitivity... in Support of Probabilistic Safety Assessment Review

ML20203E586
Person / Time
Site:	Seabrook
Issue date:	07/21/1986
From:	Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	Noonan V Office of Nuclear Reactor Regulation
Shared Package
ML20203E591	List: ML20203E586 ML20203E594 ML20203E604 ML20203E616
References
SBN-1167, NUDOCS 8607240181
Download: ML20203E586 (4)

Text

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r , SEABROOK STATION Engineering Office b

~ D bI July 21, 1986 PutWe Service of New Hampshke NEW HAMPSHIRE YANKEE DIVISION SBN- 1167 T.F. B7.1.9 9 United States Nuclear Regulatory Commission Washington, DC 20555 Attention: Mr. Vincent S. Noonan, Project Director PWR Project Directorate No. 5

References:

(a) Construction Permits CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) PSNH Letter (SBN-1053), dated May 17, 1986, " Response to NRC/LLNL Dratt Review of SSPSA", J. DeVincentis to V. S. Noonan (c) USNRC Letter dated April 4, 1985, "Seabrook PSA Review",

G. W. Knight to P.. J. Harrison (d) NUREG/CR-4540, dat ed February 1986, "A Review of the Seabrook Station Probabilistic Safety Assessment:

Containment Failure Modes and Radiological Source Terms", Brookhaven National Laboratory

Subject:

Seabrook Station Probabilistic Safety Assessment Update

Dear Sir:

Reference (b) provided our response to the NRC/LLNL review of the SSPSA, and advised the NRC of our continuing ef forts to enhance under-standing of risk levels and the factors that contribute to these levels.

As a result of these ongoing ef forts, new information is available for use in updating the SSPSA. In light of our continuing use of the SSPSA to improve Seabrook Station's Technical Specifications as well as other potential uses (e.g., design change reviews, backfit asalysis) we believe it is important for the NRC to continue its review of our analyses. In this regard, we also reaf firm that we are available to support further s review of the SSPSA and the enclosed additional information.

Od I l ng72 mamba h

Seabrook Station Construction Field Office P.O. Box 700 + Seabrook. NH O3874

4 ,

United Statss Nuclear Rrgulatory Commission SBN- 1167 Attention: Mr. Vincent S. Noonan Page 2 In your review, Reference (c), you indicated that the SSPSA seismic fragility analysis may be overly conservative. The attached reassessment of seismic f ragilities and revised report (Attachment 1) updates our response to this comment. It should be noted that the increases in seismic capacity shown in the revised report result primarily from conducting a detailed review of the most recent Seabrook Station component seismic qualification reports as well as uncovering multiple conservatisms in the qualifications that were not apparent from review of the summaries used for the initial fragility analysis. We plan to use these revised fragilities in future updates of the SSPSA.

Attachments 2 and 3 evaluate the sensitivity of early health risk to a spectrum of assumptions including a very conservative source term that envelops those evaluated in the Brookhaven National Laboratory review, Reference (d). The results of the conservative source terms, Attachment 3, illustrates the value of the Seabrook Station containment with its high pressure capacity. The source terms in Attachment 2, which express our present state of knowledge, including uncertainties, will be used in future updates of the SSPSA.

Attachment 2 also provides a more realistic model of the V-sequence, which dominated the early containment bypass f requency in the SSPSA. We updated this model to account for new insights and more realistic treat-ment of the initiation, progression, and mitigation of this class of accident sequences. As a result of the updated analysis the risk contri-bution of these events has been reduced because of the reductioa in the likelihood of early containment bypass.

Since efforts to use this new information and to update the SSPSA are in progress your prompt review of the attached information is requested.

1[n this regard we would suggest a meeting, at your earliest convenience, to discuss the attached information and develop a mutually acceptable schedule for conducting the review.

Very truly yours, fs / W John DeVincentis l

Director of Engineering Attachments cc: Atomic Safety and Licensing Board Service List

Disna Curr2n, Ezquira , ,

Pater J. Msthawa, Mayer City Hall H:rmon & Weica 2001 S. Street, N.W. Ntwburyport, MA 01950 Suite 430 Washington, D.C. 20009 Judith H. Mizner Silvergate, Gertner, Baker, Sherwin E. Turk, Esq. Fine, Good & Mizner Office of the Executive Legal Director 88 Broad Street U.S. Nuclear Regulatory Commission Boston, MA 02110 Tenth Floor Washington, DC 20555 Calvin A. Canney City Manager Robert A. Backus, Esquire City Hall 116 Lowell Street G 126 Daniel Street P.O. Box 516 Portsmouth, NH 03801 Manchester, NH 03105 '

Stephen E. Merrill, Esquire Philip Ahrens, Esquire Attorney General Assistant Attorney General George Dana Bisbee, Esquire Department of The Attorney General Assistant Attorney General Statehouse Station #6 Office of the Attorney General Augusta, ME 04333 25 Capitol Street Concord, NH 03301-6397 Mrs. Sandra Gavutis Chairman, Board of Selectmen Mr. J. P. Nadeau RFD 1 - Box 1154 Selectmen's Office Kenusington, NH 03827 10 Central Road Rye, NH 03870 Carol S. Sneider, Esquire ,

Assistant Attorney General Mr. Angie Machiros Department of the Attorney General Chairman of the Board of Selectmen One Ashburton Place, 19th Floor Town of Newbury Boston, MA 02108 Newbury, MA 01950 Senator Gordon J. Humphrey Mr. William S. Lord U.S. Senate Board of Selectmen Washington, DC 20510 Town Hall - Friend Street (ATTN: Tom Burack) Amesbury, MA 01913 Richard A. Hampe, Esq. Senator Gordon J. Humphrey Hampe and McNicholas 1 Pillsbury Street 35 Pleasant Street Concord, NH 03301 l

Concord, NH 03301 (ATTN: Herb Boynton)

I Thomas F. Powers, III H. Joseph Flynn, Esquire Town Manager Office of General Counsel Town of Exeter Federal Emergency Management Agency l

10 Front Street 500 C Street, SW Exeter, NH 03833 Washington, DC 20472 Brentwood Board of Selectmen Paul McEachern, Esquire RFD Dalton Road Matthew T. Brock , Esquire Brentwood, NH 03833 Shaines & McEachern 25 Maplewood Avenue Gary W. Holmes, Esq. P.O. Box 360 Holmes & Ells Portsmouth, NH 03801 47 Winnacunnet Road Hampton, NH 03842 Robert Carrigg Town Office Mr. Ed Thomas Atlantic Avenue FEMA Region I North Hampton, NH 03862 442 John W. McCormack PO & Courthouse Boston, MA 02109

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