ML20197C292

Describes Proposed Design Changes to Emergency Diesel Generators (EDG) Breaker Control Circuitry,Responding to LOCA Concurrent W/Loss of Offsite Power While EDG Performing Surveillance Test,Per 861021 Meeting

ML20197C292
Person / Time
Site:	Byron
Issue date:	10/29/1986
From:	Ainger K COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
2333K, NUDOCS 8611060037
Download: ML20197C292 (2)

Text

,# i f Commonwealth Edison

, One First National Plaza. Chicago, lilinois k ,

.y,e Address Reply to: Post Office Box 767

\d Chicago, Illinois 60690 0767 October 29, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Byron Station Units 1 and 2 Emergency Diesel Generators NRC Docket Nos. 50-454 and 50-455

Dear Mr. Denton:

The capability of Byron Station's Emergency Diesel Generators (EDG) to respond to a Loss-of-Coolant Accident (LOCA) concurrent with a loss of off-site power while the EDG is performing its surveillance test was discussed in a meeting held in Bethesda, MD on October 21, 1986.

Commonwealth Edison personnel met with members of the NRC Staff to review potential design changes to EDG breaker control circuitry. A description of the proposed design change is provided below.

A two position " Normal-Test" OT2 type control switch will be added in the Main Control Boards directly above the existing breaker control switch for each diesel generator unit. The " Test" position of this control switch will be used to bypass the control circuit interlock provided by the STP breaker control switch contact which presently prevents the automatic reclosure of the diesel generator breaker in the event of three specific conditions.

These conditions are:

a) A design basis accident (LOCA) b) A loss of offsite power occurring simultaneously or sequentially with 'a' above.

c) The EDG is undergoing full load testing while 'a' and 'b' occur.

This testing is performed with the EDG in parallel with the offsite power sources.

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Mr. H. R. Denton October 29, 1986 In addition, administrative procedures will be established requiring that this new control switch be operated prior to closing the diesel generator breaker during periodic testing. This will ensure that the proposed design change will be functioning whenever an EDG is placed on parallel with the offsite power sources. Thus, no operator action will be required to ensure that an EDG will successfully power the appropriately sequenced loads in the event of a LOCA and a loss of offsite power during the performance of an EDG surveillance test.

This design change will be implemented on Byron Unit 1 prior to startup following the first refueling outage. The change will be implemented on Byron Unit 2 prior to exceeding % power.

If any questions arise regarding this matter, please direct them to this office.

Very truly yours, K. A. Ainger Nuclear Licensing Administrator 1m cc: Resident Inspector - Byron L. N. Olshan - NRR 2333K