Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
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 6-12F 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 2200F. 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 120F 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
