05000206/LER-1981-001, Forwards LER 81-001/01T-0

Forwards LER 81-001/01T-0

ML13333A912
Person / Time
Site:	San Onofre
Issue date:	01/19/1981
From:	Haynes J Southern California Edison Co
To:	Engelken R NRC Office of Inspection & Enforcement (IE Region V)
Shared Package
ML13333A913	List: 05000206/LER-1981-001, Forwards LER 81-001/01T-0 05000206/LER-1981-001-01, /01T-0:on 810116,design Problem Noted Re Safeguard Load Sequencing Sys.Caused by Possible Resequencing of Safety Injection Sys Loads Due to Oscillation of Safety Injection Parameters About Setpoints
References
NUDOCS 8102030408
Download: ML13333A912 (2)

LER-1981-001, Forwards LER 81-001/01T-0

Event date:
Report date:
2061981001R00 - NRC Website

text

Southern California Edison Company P. o.

BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770

\\2 J. G. HAYNES TELEPHONE MANAGER OF NUCLEAR OPERATIONS January 19, 1981

(

3) 572-1742 U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region V 1990 North California Boulevard Suite 202, Walnut Creek Plaza Walnut Creek, California 94596 Attention: Mr. R. H. Engelken, Director 0 2 i

U.S0 #M tWIAAr=

DOCKET NO. 50-206 SAN ONOFRE -

UNIT 1

Dear Sir:

Cr This letter describes a design problem involving the Safeguard Load Sequencing System and is being reported in accordance with Specification 6. 9. 2.a of the San Onofre Unit 1 Technical Specifications.

Provided as an enclosure is the Licensee Event Report 81-001. This letter constitutes the complete report on this problem such that a two week followup report will not be necessary.

By letter dated September 16, 1980, we provided your office with a written followup report regarding design problems with the sequencers. In the process of correcting the design problems indicated in our September 16, 1980 letter, an additional design problem has been determined. In the event the safety injection system were to be actuated and an LOP occurred, the sequencer would automatically load the safety injection loads sequentially. This loading takes place in 10 to 21 second timing groups. If the safety injection actuation parameters were to oscillate about their safety injection setpoints, the sequencer timing would be reset and resequencing would occur when the parameters reach the safety injection setpoints again. Following actuation of the safety injection system, the operator is instructed by the emergency operating procedure to engage the safety injection block switch.

This prevents resequencing of the sequencer and the safety injection loads even in the event the safety injection parameters are oscillating about their setpoints. In the event the operator does not engage the block switch and oscillation occurs, the scenarios described below could occur.

8G 2 0 /0

Mr. R. H. Engelken, Director January 19, 1981 If the oscillations occur prior to 21 seconds, some of the safety injection load groups would not be automatically actuated. Once all the safety injection loads have been automatically loaded and the oscillations were to occur after 21 seconds, the sequencer would still resequence; however, the safety injection loads would not be affected and would still remain operating.

This design problem will also be resolved prior to the return to operation. If you have any questions regarding this matter, please call me.

Sincerely, Enclosure cc:

Director, Office of Management and Information Program Control (2)