ML20106J510

Forwards Nonproprietary WCAP-10640 & Proprietary WCAP-10639, Technical Bases for Eliminating Large Primary Loop Pipe Rupture as Structural Design Basis for Prairie Island Unit 1. Proprietary Rept Withheld (Ref 10CFR2.790)

ML20106J510
Person / Time
Site:	Prairie Island
Issue date:	10/24/1984
From:	Musolf D NORTHERN STATES POWER CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML19269A708	List: ML20106J510 ML20106J526 ML20106J537
References
GL-84-4, TAC-8731, TAC-87311, TAC-8732, TACS-8731, TACS-8732, NUDOCS 8411010239
Download: ML20106J510 (2)

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Northern States Power Company 414 Nicottet Mall Minneapons, Minnesota 55401 Teleonone 5612) 330 5500 October 24, 1984 Director of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Elimination of Large Reactor Coolant System Pipe Ruptures from Structural Design Basis In our letter dated June 15,198t. we informed the commission that we would contract with Westinghouse Electric Company to perform a mechanistic fracture mechanics evaluation for the reactor coolant loops to justify e eliminating postulating large breaks for structural design purposes.

This analysis would serve as the basis for an exemption request from the requirements of GDC-4 of Appendix A to 10 CFR Part 50 as permitted by NRC Ceneric Letter 84-04 dated February 1, 1984. The purpose of this letter is to provide, for the information of the NRC Staff, the Westinghouse analytical results for Unit No. 1 and the status of the Unit 2 analytical work.

Forty copies of this letter and Westinghouse Report WCAP 10640,

" Technical Bases for Eliminating Large Primary Loop Pipe Rupture as the Structural Design Basis for Prairie Island Unit 1", September, 1984 are provided. Ten copies of the proprietary version of this report, WCAP 10639 are also attached. WCAP 10639 should be withheld from public disclosure in accordance with Section 2.790 of the Commission's regulations. An affidavit signed by Westinghouse, the owner of this information, is attached.

The attached Westinghouse report addresses only Unit 1. Westinghouse has found that for some of the Unit 2 primary loop piping, the projected end-of-life toughness falls below the benchmark toughness of the worst case thermally-aged material. The Unit 2 piping material thus could not be entirely qualified as has been done for the Unit 1 piping. We are now working with Westinghouse on alternatives available for Unit 2.

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Director of NRR-October 24, 1984 Page 2 Northem States Power Company At this time, Northern States Power Company believes that an analysis for

. Unit 2 can be performed. Additional evaluation or tdsting will be necessary. No finn schedule for resolving this matter has been determined at this time. We will continue to keep our Project Manager in the Division of Licensing informed of our schedule for completing the Unit 2 work. An exemption request from CDC-4 will be submitted following the completion

.of the Unit 2 analysis.

Please contact us if you have any questions related to tne information we have provided.

Dj Mw.

David Musolf Manager - Nuclear Suppor Services DMM/ dab c: Regional Administrator-III, NRC NRR Project Manager, NRC Resident Inspector, NRC G Charnoff Attachments: (1) WCAP-10640 (40 copies)

(2) Affidavit supporting non-disclosure of WCAP-10639 (3) WCAP-1063) (10 copies) - Westinghouse Proprietary t

ATTACHMENT (3) C0tTIAINS 10 CFR PART 2, SECTION 2.790 ftATERIAL NOT TO BE PLACED IN PUBLIC DOCUMENT ROOM

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