United States Nuclear Regulatory Commission - Protecting People and the Environment

Westinghouse ECCS Evaluation Models (Generic Letter No. 86-16)


                               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
Page Last Reviewed/Updated Thursday, June 27, 2013