Odyn Code Reanalysis Requirements (Generic Letter 81-37)

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

                              December 29, 1981

ALL BOILING WATER REACTOR LICENSEES (EXCEPT HUMBOLDT BAY AND DRESDEN 1) 

SUBJECT:  ODYN CODE REANALYSIS REQUIREMENTS (GENERIC LETTER 81-37) 

By letter dated November 4, 1980 we informed you of our requirements for use
of the ODYN code to calculate pressurization transients. We stated that 
after January 1982 all operating BWRs with General Electric analyses must 
have the limiting transients recalculated with the ODYN code, even if no 
reload submittal has been received. 

By letter dated January 29, 1981 we provided you a safety evaluation and a 
supplemental safety evaluation describing our basis for acceptance of this 
code, and information required for ODYN application, including a description
of two options for application. 

For those plants which can be demonstrated to have scram times bounded by 
the option B scram time distribution, the option B calculations would be 
expected to be less limiting than REDY. Therefore, delay of OYDN analyses 
until the next refueling is a reasonable approach. For such plants, the 
licensees are requested to submit to the NRC before January 1982 their 
conclusion that option B is applicable to their plant. Those plants which 
cannot demonstrate scram times bounded by the option B scram time 
distribution should, by January 1982, submit ODYN analyses in accordance 
with option A or should propose and support other appropriately conservative 
operating limitations. 

This request for information was approved by OMB under clearance number 
3150-0080 which expires December 31, 1982. Comments on burden and 
duplication may be directed to the Office of Management and Budget, Reports 
Management Room 3208, New Executive Office Building, Washington, D. C. 
20503. 

                              Sincerely, 


                              Darrell G. Eisenhut, Director 
                              Division of Licensing 
                              Office of Nuclear Reactor Regulation 

cc:  Service List 



8201040001