Additional Information RE 11/09/79 Letter On ECCS Calculations (Generic Letter 79-66)

 GL79066 

                                 UNITED STATES 
                         NUCLEAR REGULATORY COMMISSION 
                            WASHINGTON, D.C. 20555 

                                   November 27, 1979 

(LETTER TO ALL OPERATING LIGHT WATER REACTORS) 

Gentlemen: 

Letters, dated November 9, 1979, were sent to all the licensees requesting 
information concerning the new fuel cladding strain and fuel assembly 
blockage models and compliance with 10 CFR 50.46. Subsequently further 
infornation was provided by the NSSS vendors and fuel suppliers regarding 
the impact of cladding heating-rate dependent burst temperature effects on 
rupture time and rupture strain/blockage and consequently on calculated peak 
cladding temperatures. The vendors and fuel suppliers supplied additional 
information by letters to the staff. 

Copies of these additional letters are enclosed. This new information should 
be used in preparing your response to the November 9, 1979 request. 

                                        Sincerely, 


                                        Darrell G. Eisenhut, Acting Director
                                        Division of Operating Reactors 

Enclosures: 
1. Letter from Babcock & Wilcox, dated November 20, 1979 
2. Letter from Combustion Engineering, dated November 16, 1979 
3. Letter from Exxon Nuclear Co., dated November 16, 1979 
4. Letter from General Electric Co., dated November 16, 1979 
5. Letter from Westinghouse Electric Co., dated November 16, 1979 
6. Letter from Yankee Atomic Electric Co., dated November 20, 1979 

                                                               80 010703-276