Odyn Code (Generic Letter 81-08)

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

                              January 29, 1981

ALL HOLDERS OF CONSTRUCTION PERMITS AND OPERATING LICENSES FOR BOILING WATER
     REACTORS 

SUBJECT:  ODYN CODE (GENERIC LETTER 81-08) 

By letter dated November 4, 1980, we informed you of our requirments for use
of the ODYN code to calculate pressurization transients, and stated that a 
safety evaluation describing the basis for our acceptance of this code would
be mailed to you in the near future. 

ENclosed you will find a safety evaluation and a supplemental safety 
evaluation which jointly evaluate the ODYN code and provide information 
required for application of ODYN. 

As you were informed in our letter of November 4, 1980, transient analyses 
performed by General Electric supporting reload submittals recieved after 
February 1, 1981, must contain appropriate ODYN analyses in place of those 
previously performed with REDY for the limiting transients. 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. Also, this requirement for the calculation of 
the limiting transients with the ODYN code is applicable to applicants for 
an operating license and is a prerequisite to obtaining an operating 
license. 

                                   Sincerely, 


                                   Darrell G. Eisenhut, Director 
                                   Division of Licensing 

Enclosures:
1) Safety Evaluation
2) Supplemental Safety Evaluation