ML18038A114

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Provides Addl Info on Rev to Nominal 3-inch Water Gap Between Adjacent Fuel Racks in Spent Fuel Pool Identified in Amend 23 to Fsar.Change Reflects as-built Status of Racks in Spent Fuel Pool
ML18038A114
Person / Time
Site: Nine Mile Point Constellation icon.png
Issue date: 01/09/1986
From: Mangan C
NIAGARA MOHAWK POWER CORP.
To: Adensam E
Office of Nuclear Reactor Regulation
References
(NMP2L-0579), (NMP2L-579), NUDOCS 8601150152
Download: ML18038A114 (4)


Text

Y NIAGARA 0 MOHAWK NIAGARA MOHAWK POWER CORPORATION/300 ERIE BOULEVARD WEST. SYRACUSE. N.Y. 13202/TELEPHONE (315) 474 ~ 15} I January 9, 1986 (NMP2L 0579)

Hs. Elinor G. Adensam, Director BHR Project Directorate No. 3 U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Hashington, DC 20555

Dear Hs. Adensam:

Re: Nine Mile Point Unit 2 Docket No. 50-410 A recent amendment (number 23). to the Final Safety Analysis Report (see page 9.1-8a and Figure 9.1-3) of Nine Mile Point 2 included a revision to the nominal 3-in. water gap between adjacent fuel racks in the spent fuel pool in the north-south direction. This letter presents additional information on the revision.

The change from the 3-in. dimension reflects the as-built status of the racks in the spent fuel pool. Gaps between adjacent racks in the north-south direction, as well as the gaps between the racks and the standoffs on portions of the peripher'y vary between 2-3/4-in. and 3-1/2-in.

The Criticality Safety Analysis (Revision 1, January 1984) prepared by Pickard, Lowe and Garrick, Inc. for Nine Hi le Point Nuclear Station Unit 2 states that a detailed two-dimensional model was used to conservatively calculate the reactivity effect of the spacing between modular fuel rack assemblies. Calculations using this model showed that the perturbation from a uniform infinite array in both the east-west and north-south directions results in a reduction in the k~ of the basic cell. Therefore, no adjustment is required to account for the spacing between rack modules.

A review of the calculations performed for the criticality analysis reveals that the effect of the water gap is so strongly negative that the difference between the nominal 3-in. and the 2-3/4 to 3-1/2-in. actual gaps is insignificant. The poisoning effect due tp any of these water gaps between the stainless steel walls of the racks exceeds that due to the Boraflex between adjacent cells within the racks.

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C Hs. Elinor G. Adensam, >rector Page 2 This information is provided to clarify the brief identification of the change provided with Amendment 23.

Very truly yours, C. V. Hangan Senior Vice President RAC:]a 1220G xc: R. A. Gramm, NRC Resident Inspector Project File (2)

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