ML19257A045

Discusses Review of Fuel Cladding Strain & Assembly Flow Blockage Models in ECCS Calculations to Confirm Conservatism.Models in Analysis Are Less Conservative than New NRC Models.Addl Calculations to Be Completed by 804212

ML19257A045
Person / Time
Site:	Millstone
Issue date:	12/27/1979
From:	Counsil W, Switzer D NORTHEAST UTILITIES
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
TAC-30209, NUDOCS 7912310543
Download: ML19257A045 (2)

Text

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December 27, 1979 Docket No. 50-336 Darrell G. Eisenhut, Acting Director Division of Operating Reactors Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Reference:

(1) D. G. Eisenhut letter to All Operating Light Water Reactors dated November 9,1979.

Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Fuel Cladding Strain and Fuel Assembly Flow Blockage Models In Reference (1), the NRC Staff requested that all licensees review their fuel cladding strain and fuel assembly flow blockage models in the ECCS calculations to confirmpthat they are as conservative as new models developed by the Staff.

If it is determined that regions exist where either model is less conservative than the Staff's new model, additional calculations must be performed to demonstrate compliance with the limits of 10CFR50.46.

Upon review of the current and proposed alternate models for rupture strain and flow blockage with the new NRC models, Northeast Nuclear Energy Company's (NNECO) fuel vendor has determined that the models used in the ECCS analysis performed for Millstone Unit No. 2 are less conservative than the new NRC models.

Preliminary investigations by the vendor indicate that Millstone Unit No. 2 remains in compliance with the peak clad temperature limits of 2200"F without decreasing peak linear heat generation rates. NNECO concurs with these pre-liminary evaluations, and pursuant to the requirements of Reference (1),

will have calculations performed which demonstrate that Millstone Unit No. 2 remains in compliance with the limits of 10CFR50.46. These calculations will be performed by our fuel vendor utilizing a new reflood heat transf er model which has been satisfactorily reviewed by the NRC Staff.

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Due to the time required to perform such an analysis, NNECO proposes to submit the results of the analysis for Millstone Unit No. 2, as required by Reference (1), on or about February 12, 1980.

We trust you find this information responsive to your request.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY b d b m tod4 (

W. G. Counsil Vice President By: /, . , c. . m m D. C. Switzer J President 1664 291