ML19323G213

Responds to IE Bulletin 80-04.Original FSAR Analysis Did Not Consider Runout Auxiliary Feedwater Flow.Most Limiting Transient Was Break Upstream of Flow Restrictor W/Offsite Power.Will Conduct Further plant-specific Analyses

ML19323G213
Person / Time
Site:	Prairie Island
Issue date:	05/15/1980
From:	Gilberts D NORTHERN STATES POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-80-04, IEB-80-4, NUDOCS 8005300572
Download: ML19323G213 (2)

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MSP NORTHERN STATES POWER COMPANY M I N N E A PO LI s. M I N N E S OTA 55401 May 15, 1980 Mr. James G. Keppler Director, Region III Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137

Dear Mr. Keppler:

Prairie Island Nuclear Generating Plant Docket No. 50-282 License No. DPR-42 Docket No. 50-306 License No. DPR-60 IE Bulletin No. 80-04 This letter and the attached report are intended to address each area noted for licensee action in the subject bulletin. A time extension to May 15, 1980 was requested and approved in a telephone conversation at 0745 on May 7, 1980 between J. A. Gonyeau (NSP) and D. C. Boyd (NRC). The purpose of this extension was to allow time for additional sensitivity studies and quality assurance reviews of the results.

Item 1 Northern States Power Company has reviewed the containment pressure response analysis for the main steam line break in containment. We have determined that the original FSAR analysis, while conservative in many respects including consideration of design AFW flow and fu.1 feedwater flow, did not consider ]

runout AFW flow. Section 2 of the attached report describes relevant assump-tions made by the NSSS vendor. i Item 2 Northern States Power Company has reviewed the analysis for the reactivity increase resulting from the main steam line break inside and outside contain-ment. The most limiting transient, considering reactor cooldown rate and the potential for return of the reactor to power with the most reactive control rod in the fully withdrawn position, was the break upstream of the flow re-strictor with offsite power available. The original analyses (Westinghouse and Exxon) did not consider the total impact of all potential water sources.

However, the analyses did include many conservative assumptions as noted in Section 2 of the attached report. Since all potential sources were not in-cguggju NSP has conducted new analyses using the DYN0DE-P Version 2 code as C'U hhEscribed in Section 3 of the report. The report describes the following:

secuooS72- * " '* "

Mr. James G. Keppler Page 2 May 15, 1980 A.. Analysis boundary conditions (Section 3)

B. Consideration of the most restrictive single failure in the SI system and the effect of that failure (Section 4)

C. The effect of extended water supply to the affected steam generator (Sections 3 and 6)

D. Appropriate hot channel factors and MDNBR (Section 6) in addition to a description of overall system response to a main steam line break (Section 4) and typical shutdown margins expected (Section 5).

Item 3 As noted in the attached report (Sections 3 and 6), the containment pressure will increase but will not exceed design pressure if the heat removal capability of the containment fan coils and/or containment spray system is considered.

The reactor-return-to-power response has not worsened; thus no corrective action is required. However, we do intend to conduct further plant specific analyses. We will notify you of the results of that review when complete.

Yours truly, 0/ b%

D. E. Gilberts Vice President Power Production cc: Mr. G. Charnoff Director, Office of Inspection and Enforcement Washington, D. C.

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