B11486, Forwards Small Break Loca/Eccs Performance Analysis W/Axial Shape Index of -0.10. Encl Analysis Amends Loca/Eccs Analysis Provided in Per 10CFR50,App K-II.1.b. Previous Reviews Re Effects of Reloads Remain Valid

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Forwards Small Break Loca/Eccs Performance Analysis W/Axial Shape Index of -0.10. Encl Analysis Amends Loca/Eccs Analysis Provided in Per 10CFR50,App K-II.1.b. Previous Reviews Re Effects of Reloads Remain Valid
ML20115J050
Person / Time
Site: Millstone Dominion icon.png
Issue date: 04/11/1985
From: Counsil W
NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To: John Miller
Office of Nuclear Reactor Regulation
Shared Package
ML20115J053 List:
References
B11486, TAC-56814, NUDOCS 8504230355
Download: ML20115J050 (3)
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Text

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  • Selden Street, Berlin, Connecticut J [,71Tj,"'"L" P.O. BOX 270

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April 11,1985 Docket No. 50-336 Bil486 Director of Nuclear Reactor Regulation ,

Attn: Mr. James R. Miller, Chief i Operating Reactors Branch #5 U.S. Nuclear Regulatory Commission Washington, D.C. 20555

References:

(1) W. G. Counsil letter to R. Reid, dated March 22, 1979. j 1

(2) R. Reid letter to W. G. Counsil, dated May 12, 1979. '

(3) E. 3. Mroczka letter to U.S. Nuclear Regulatory Commission, dated February 20,1985.

Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Small Break Loss-of-Coolant Accident Evaluation j In Reference (1), Northeast Nuclear Energy Company provided the small break LOCA/ECCS performance analysis currently approved for Millstone Unit No. 2.

The Staff, in Reference (2), found the LOCA analysis in conformance with the acceptance criteria for ECCS for light water nuclear power reactors (10CFR50.46).

The Millstone Unit No. 2 Licensee Event Report 85-001-0, Reference (3),

documented an inconsistency between the Millstone Unit No. 2 Technical Specification requirement on axial shape index (ASI) and the safety analysis ASI assumptions used in the Millstone Unit No. 2 small break LOCA analysis.

The most negative ASI input to the Reference (1) analysis was an ASI of (-0.14).

Technical Specifications allow the 100% power ASI to be no more negative than

(-0.10). If the (1 06) 0 ASI uncertainty is introduced into the analysis, the most conservative upper bound with respect to ASI becomes (-0.10) - (0.06) = (-0.16),

which is inconsistent with the (-0.14) ASI input to the small break LOCA model.

Subsequently, a calculation was performed to determine the effects on the small break LOCA analysis of the more negative ASI value of (-0.16). The calculated peak clad temperature, during a postulated small break LOCA, increased from 19710F to 20350F as a result of the more negative ASI of (-0.16). Accordingly, pursuant to 10CFR50 Appendix K-II.l.b, the attachment to this letter provides an amendment of the small break LOCA/ECCS performance analysis provided in Reference (1).

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B504230355 850411 FVf PDR ADOCK 05000336 P PDR ,

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NNECO has determined that all reviews previously performed, concerning the effects of reloads or plant changes on the Reference (1) small break LOCA/ECCS performance analysis, remain valid with the increased peak clad temperature of 20350F.

The results and conclusions stated in the attachment are identical to those stated in Reference (1). With an ASI of (-0.10), the calculated maximum clad temperature for small break LOCA conditions remains below the acceptance criterion of 22000F (10CFR50.46(b)(1)).

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY M101 W. G.' Counsil Senior Vice President

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