NRC Generic Letter 80-91, Odyn Code Calculation

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GL80091

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

November 4, 1980

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

The use of the ODYN code to calculate pressurization transients has been reviewed extensively by the staff and discussed with the General Electric Company. We have found that ODYN provides acceptable best estimate calculation predictions of the core responses to pressurization transients. A safety evaluation describing the basis for this conclusion will be mailed to you in the very near future. This letter is for the purpose of advising you as early as possible of our requirements for implementation of ODYN for licensing basis calculations performed by the General Electric Company. These requirements are applicable to license applications and all proposed license amendments, including core reloads for which analyses are provided by General Electric.

Transient analyses performed by General Electric supporting reload submittals received prior to February 1, 1981, will be reviewed taking into account the results of recent generic transient analyses with ODYN. Appropriate CPR penalties will be applied on a case by case basis. Transient analyses performed by General Electric supporting reload submittals received after February 1, 1981, must contain appropriate ODYN analyses in place of those previously performed with REDY for the limiting transients. Generally, these will include generator load rejection/turbine trip without bypass (whichever is limiting), feedwater controller failure - maximum demand, and main steamline isolation valve closure (to satisfy ASME code pressure requirements). 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. The transients analyzed with ODYN must be justified to be the limiting transients.

General Electric has provided an ODYN analysis for the two most limiting events for BWR 3 and BWR 4 plant types and has committed to provide analyses for a BWR 2 plant type by November 1, 1980. Any

.November 4, 1980

penalties resulting from our review of the analyses for any plant type will be applied to all plants of that type until plant-specific calculations have been performed with ODYN for the two most limiting transients.

Sincerely,

Darrell G. Eisenhut, Director Division of Licensing

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