NRC Generic Letter 86-16, Westinghouse ECCS Evaluation Models
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WASHINGTON, D. C. 20555
October 22, 1986
TO: All Pressurized Water Reactor Applicants and Licensees (Generic Letter 86-16)
SUBJECT: WESTINGHOUSE ECCS EVALUATION MODELS
Gentlemen:
In a letter dated June 2, 1986 (non-proprietary version enclosed),
Westinghouse notified the NRC of the need for some additions and corrections to the ECCS Evaluation Models that contain the WREFLOOD and the BART codes. The problems with these codes were discussed at a meeting in Bethesda, Maryland, on June 23, 1986. If either of these codes were used in your ECCS analyses, then this letter is applicable to your plant(s). This letter also applies to non-Westinghouse reactor licensees who use these codes, e.g.,
Millstone, Unit 2.
For those plants which were analyzed with the 1978 and 1981 versions of the Westinghouse ECCS Evaluation Model, the change to the WREFLOOD code would result in a 6-12<deg>F increase in peak clad temperature. Westinghouse has informed the NRC that the increase would not cause the peak clad temperature (PCT) in current analyses to exceed 2200<deg>F. A new ECCS reanalysis is not required. It is our understanding that Westinghouse does not plan to modify the 1978 and 1981 ECCS Evaluation Models or use them for future ECCS analyses.
For those plants which were analyzed with the 1981 Westinghouse ECCS Evaluation Model with BART, the changes in WREFLOOD and BART could result in approximately 120<deg>F increase in peak clad temperature. In a letter dated July 24, 1986, Westinghouse submitted an addendum to the BART code which makes the corrections identified in the June 2 letter and modifies the application of the radiation heat transfer model. We have approved the addendum to the BART code (safety evaluation enclosed) and concluded that the modifications to the heat transfer model mitigate the increase in the peak clad temperature caused by the other BART and WREFLOOD changes.
Therefore, if you used the 1981 Westinghouse ECCS Evaluation Model with BART in a current analysis, a reanalysis is not required. However, if you use an ECCS analysis to support a future licensing action, then that analysis must be performed with a correct evaluation model. It is our understanding that ECCS analysis performed with the 1981 ECCS Model with BART which support licensing actions currently under review by the NRC have already been redone with the corrected version.
Sincerely,
Harold R. Denton, Director Office of Nuclear Reactor Regulation
Enclosure: As Stated 8610220369