05000206/LER-1979-014, Forwards LER 79-014/03L-0

Forwards LER 79-014/03L-0

ML13330A769
Person / Time
Site:	San Onofre
Issue date:	09/28/1979
From:	James Drake SOUTHERN CALIFORNIA EDISON CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML13330A770	List: 05000206/LER-1979-014, Forwards LER 79-014/03L-0 05000206/LER-1979-014-03, /03L-0:on 790829,erratic Behavior of One of Two Subchannels of Sequencer 2 Was Observed.Caused by Failure of Voltage Regulating Transistor in Power Supply.Reactor Brought to Subcritical Condition & Power Supply Replaced
References
NUDOCS 7910040299
Download: ML13330A769 (3)

LER-1979-014, Forwards LER 79-014/03L-0

Event date:
Report date:
2061979014R00 - NRC Website

text

Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE J.

H. DRAKE ROSEMEAD, CALIFORNIA 91770 TELEP-ONE VICE PRESIDENT 213-572-2258 September 28, 1979 U. S. Nuclear Regulatory Commission Iegion V Office of Inspection and Enforcement Suite 202, Walnut Creek Plaza 1990 North California Boulevard Walnut Creek, California 94596 Attention:

Mr. R. H. Engelken, Director Docket No. 50-206 San Onofre Unit 1

Dear Sir:

This letter describes a reportable occurrence involving the No. 2 safeguard load sequencer.

This is one of two load sequencers, each con trolling the actuation of one of two safety injection trains and one of two emergency diesel generators.

Submittal is in accordance with the reporting requirements stipulated in section 6.9.2(b) of Appendix A to the Provisional Operating License DPR-13.

On August 29, while performing routine testing of the No. 2 diesel generator, erratic behavior of one of the two subchannels of the No. 2 sequencer was observed.

Diagnostic testing of this sequencer revealed a voltage disturbance on the 15 Vdc bus of the erratic subchannel.

Addi tional testing revealed small variations in the 125 Vdc source voltage to the power supply, resulting in large variations in the 15 Vdc power supply output.

A review of. the sequencer logic led to the conclusion that a malfunc tion of the subject power supply could potentially prevent proper operation of the No. 2 sequencer and its associated emergency diesel generator during a postulated accident.

Therefore, in accordance with sections 3.3.1 and 3.7 of the Technical Specifications the unit was removed from service at 9:00 p.m. on August 29 in order to effect repairs.

After the reactor was brought to a subcritical condition, the No. 2 sequencer was removed from service and the subject power supply was replaced.

After successfully testing the No. 2 sequencer, the unit was returned to service at 4:45 a.m.

the following morning.

U. S. Nuclear Regulatory Commission Page 2 Subsequent investigations by the power supply manufacturer indicates the cause of the malfunction to be a random failure of a voltage regulating transistor internal to the 15 Vdc power supply.

Since this failure was random in nature, no further corrective action is planned.

During the course of this event the No. 1 sequencer and associated diesel generator were operable.

Therefore, there was no degradation of plant safety as a result of this occurrence.

Should you have any questions regarding this matter, please contact me.

/

Si-ncerel

Attachment:

Licensee Event Peport 79-014 cc:

Director, Nuclear Reactor Regulation (30)

Director, Office of Management Information & Program Control (3)

NRC-FORM366 U. S. NUCLEAR REGULATORY COMMISSION (7-77)

NSEE EVENT REPORT CONTROL BLOCK:

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 1 6

III I ci Al Si O S1 1110 01 -1 0 o0 0000 0

- I 1014 I 11 111 j 4 1 1

7 8

9 LICENSEE CODE 14 15 LICENSE NUMBER 25 26 LICENSE TYPE 30 57 CAT 58 CON'T 1RRE L LJ@6 01 51 01 0121 01 61 I 10 1812191 7191 1019121 817 19 7

8 60 61 DOCKET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES o21 I During normal operations while conducting routine monthly testing of the No. 2 diesel I generator, erratic behavior of one of two subchannels of the No.

2 sequencer was l

I observed.

Diagnostic testing revealed the cause of this behavior to be a failed I

o5 1 15 Vdc power supply on one subchannel.

The failure of this power supply could have l

o6-I prevented the proper operation of one of two emergency diesel generators and one of I

o=~ I two safety injection trains.

The redundant sequencer and diesel generator were o 8-Ioperable during this event.

This report is per T.S. 6.9.2(b).

7 89 80 SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE 0I El@D L E@ LG (3 X l XI XI XI Xl Xl LJ L

7 8

9 10 11 12 13 18 19 20 SEQU ENTIAL OCCURRENCE REPORT REVISION RR EVENT YEAR REPORT NO.

CODE TYPE NO.

0 REPOR j

7 l9 l1 l

1 0 1 40l LL O

3J 21 22 23 24 26 27 28 29 30 31 32 ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIMECOMP.

COMPONENT TAKEN ACTION ON PLANT METHOD HOURS (22 SUBMITTED FORM SUB.

SUPPLIER MANUFACTURER LJ@

LA LL:JJO 10 18 011 0 L i LLI SL 21 51 71s 33 34 35 36 37 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS I The cause of this failure was determined to be the random failure of a voltage I regulating transistor internal to the power supply. Corrective actions consisted of bringing the reactor to a subcritical condition, removing the No.

2 sequencer from service and replacing the failed power supply.

7 8

9 80 FSATUS

% POWER OTHER STATUS MISOD DISCOVERY DESCRIPTION FALTYS M

OE TESTS&

DSETHO OFCVRYDSRITO 1

1 [j

1 l 0 I 0 NA I Lj0i Routine testing 7

8 9

10 12 13 44 45 46 80 ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY-LOCATION OF RELEASE

[ 6] Lz I @

U NA I

I NA 7

8 9

10 11 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE

DESCRIPTION

[

loloo @ Z II I NA 7

8 9

11 12 13 80 PERSONNEL INJURIES NUMBER DESCRIPTION)

[ ]I01 01 0181 NA I

7 8

9 11 12 80 LOSS OF OR DAMAGE TO FACILITY TYPE

DESCRIPTION

I9 1j 1I 7

8 9

10 80 PUBLICITY NRC USE ONLY ISSUED

DESCRIPTION

4 I

I I6 1

NA I IH-i IlI 7

8 9

1N 68 69 80 J.

M. Curran NAME OF PREPARER HN9 (7442-000