ML20062K219

Recommends Licensee Submit Revised Safety Analyses Using W-3 Critical Heat Flux Correlation for Review of XN-NF-82-21, Application of Exxon Nuclear Co PWR Thermal Margin Methodology to Mixed Core Configurations

ML20062K219
Person / Time
Site:	Cook
Issue date:	08/02/1982
From:	Berlinger C Office of Nuclear Reactor Regulation
To:	Varga S Office of Nuclear Reactor Regulation
Shared Package
ML17319B487	List: ML17319B486 ML20062K219
References
NUDOCS 8208170090
Download: ML20062K219 (2)

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MEMORANDUM FOR: Steven A. Varga, Chief Operating Reactors Branch #1 1

Division of Licensing FROM:

Carl H. Berlinger, Chief jl Core Perfomance Branch Division of Systems Integration

SUBJECT:

D. C. COOK UNIT 2 CYCLE 4 RELOAD Presently the Core Perfomance Branch (CPB) is reviewing XN-NF-82-21,

" Application of Exxon Nuclear Company PWR Themal Margin Methodology to Mixed Core Configurations," and XN-NF-621, Revision 1, " Exxon Nuclear DNB Correlation for PWR Fuel Designs".

Both of these topical reports are referenced by the Indiana and Michigan Electric Company as supporting infoncation for the Cycle 4 operation of D. C. Cook Unit 2.

CPB has reviewed the methodology described in XN-NF-82-21(P) and identified a number of concerns on ENC's approach to calculating the location and value of the minimum departure from nucleate boiling ratio (MDNBR). We anticipate completing our review of this topical by Septeaber 30, 1982. This would be consistent with the Cook 2 startup date of December 1,1982; however, the conclusion presently being fomulated by CPB is that the use of this methodology nay result in a DNBR penalty.

With respect to the critical heat flux (CHF) correlation presented in XN-NF-621, Revision 1, CPB has contracted with the Idaho National Engineering Laboratory (INEL) to review the validity of the correlation.

INEL has a number of concerns with the correlation and CPB does not foresee completing our review in time for the Cook reload. Therefore, we are recommending that the licensee submit revised safety analyses using the W-3 CHF correlation.

In addition to these concerns, CPB has a major concern in the area of themal-hydraulic compatibility of two different types of fuel assemblies, e.g., fuel rod 00s of 0.374" and 0.360" and different grid designs. Before we can approve a mixed core reload of this type, Exxon must provide additional submittals which demonstrate in a more quantified manner the effects on diversion cross-

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i AUG 2 1982 Steven A. Varga flow of the different grid designs and fuel pin diameters and the consequential effects on DNB. Also, ENC should provide information which demonstrates that sufficient thermal margin is available to account for any interbundle crossflow uncertainties.

In recent discussions with the project manager, we were i*nformed that the August 1,1982 due date could be alteredl therefore, CPB is requesting that the August 1,1982 due date be postponed to November 23, 1982. Also the above information should be submitted by Exxon at least two months for to November 1982. This will ensure that sufficient time is'savaial for CPB to perfonn a complete review of the submittal.

M ah Carl H. Berling r, Chief

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Core Performance Branch Division of Systems Integration cc:

R. Mattson L. Rubenstein J. Berggren R. Cilimberg 4