ML13308B488
| ML13308B488 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/16/1976 |
| From: | Head J SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 8103060530 | |
| Download: ML13308B488 (5) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE J. T. HEAD, JR.
ROSEMEAD, CALIFORNIA 91770 TELEPHONE VICE PRESIDENT 213-572-1472 September 16, 1976 U. S. Nuclear Regulatory Commission Region V Office of Inspection and Enforcement RCGIOV Walnut Creek Plaza, Suite 202 1990 North California Boulevard Ql'\\ T Walnut Creek, California 94596 Docket No. 50-206 Attention: R. H. Engelken, Director
Dear Sir:
This letter describes a reportable occurrence concerning the San Onofre Nuclear Generating Station Unit 1 Instrumentation and Control System. It is submitted in accordance with the reporting requirements stipulated in Section 6.9.2.b of the Technical Specifications.
On August 23, 1976, at 2:20 p.m., the Vital Bus Number 1 transferred to the backup power source. This transfer was the result of a component failure in the Number 1 inverter, the normal power, source for this bus. The momentary loss of power precipitated a transfer of all three steam generator feedwater level control systems from their normal power supplies which are fed from Vital Bus Number 1 to their backup power supplies.
The backup positive fifteen volt power source had malfunctioned and was operating at approximately eight volts. This voltage was inadequate to support the components in the feedwater control systems. The result was a loss of steam and feedwater flow signals to the three steam generator level control systems. Under these circumstances the steam feedwater flow mismatch reactor trip was inoperable.
The steam generator feedwater systems were transferred to manual control, and continuous operator surveillance was initiated as specified in Technical Specification 3.5, Table 3.5.1. The feedwater control system was immediately manually transferred back to the normal power source. The positive fifteen volt backup power supply was repaired and the control system returned to normal operation.
-2 This was the first failure of a steam generator level control system power supply at this facility and no further action is planned at this time.
Sincerely,
Attachment:
Licensee Event Report cc:
Director, NRC Office of Inspection and Enforcement Director, NRC Office of Management Information and Program Control
Southern California Edison Company J. T. HEAD, JR.
SEMlv CALIFO
'770 TELEPHONE VICE PRESIDENT 213-5721472 Sep 1V U. S. Nuclear Regulatory Commi Region V Office of Inspection and Enforcement CMMISSION Walnut Creek Plaza, Suite 202 1990 North California Boulevard Walnut Creek, California 94596 Docket No. 50-206 Attention: R. H. Engelken, Director
Dear Sir:
This letter describes a reportable occurrence concerning the San Onofre Nuclear Generating Station Unit 1 Instrumentation and Control System. It is submitted in accordance with the reporting requirements stipulated in Section 6.9.2.b of the Technical Specifications.
On August 23, 1976, at 2:20 p.m., the Vital Bus Number 1 transferred to the backup power source. This transfer was the result of a component failure in the Number 1 inverter, the normal power source for this bus.
The momentary loss of power precipitated a transfer of all three steam generator feedwater level control systems from their normal power supplies which are fed from Vital Bus Number 1 to their backup power supplies.
The backup positive fifteen volt power source had malfunctioned and was operating at approximately eight volts. This voltage was inadequate to support the components in the feedwater control systems. The result was a loss of steam and feedwater flow signals to the three steam generator level control systems. Under these circumstances the steam feedwater flow mismatch reactor trip was inoperable.
The steam generator feedwater systems were transferred to manual control, and continuous operator surveillance was initiated as specified in Technical Specification 3.5, Table 3.5.1. The feedwater control system was immediately manually transferred back to the normal power source. The positive fifte'en volt backup power supply was repaired and the control system returned to normal operation.
-3
-2 This was the first failure of a steam generator level control system power supply at this facility and no further action is planned at this time.
Sincerely,
Attachment:
Licensee Event Report cc:
Director, NRC Office of Inspection and Enforcement Director, NRC Office of Management Information and Program Control
LICENSEE EVENT REPOf CONTROL BLOCK:
(PLEASE PRINT ALL REQUIRED INFORMATION]
1 6
LICENSEE LICENSE EVENT NAME LICENSE NUMBER TYPE TYPE
@i Ic AISIO SI 0 0 00101_10 1
01 01-01_00 10 10 13L 1 4l0 LoI L.n J
7 89 14 15 25 26 30 31 32 REPORT REPORT CATEGORY TYPE SOURCE DOCKET NUMBER EVENT DATE REPORT DATE
[iCONi T DJj LL] L j 10 15 101-10 12 1 0 161 101812131716 1 9 11 017 161 7
8 57 58 59 60 61 68 69 74 75 80 EVENT DESCRIPTION 0 During normal operations, Number 1 vital bus transferred to its backup power source, I
7 8 9 80 03 Iwhich precipitated the transfer of all three feedwater control systems to their backup I 7
8 9 80 EB Ipower supplies. The backup power supply for the feedwater control system was deq adedi 7 89 80 05 land under these circumstances, the steam feedwater flow mismatch reactor trip was 7 89..
80 0 8 ginoperable. Feedwater control was immediately transferred back to its normal power s 7
8 9 PRIME 80 SYSTEM CAUSE COMPONENT COMPONENT CODE CODE COMPONENT CODE SUPPLIER MANUFACTURER VIOLATION 7I I1 AI LE II I NISI T RI UI l_NJ IW 1 12 1!0 1 LNJ 7
8 9 10 11 12 17 43 44 47 48 CAUSE DESCRIPTION 0a 8
The steam generator feedwater control system backup power supply failure was caused 7
8 9 80 09 1by the failure of bridge rectifier diodes in the fifteen volt supply. The power 7 B 9
.80 l supply was repaired.
7 8 9 80 FACILITY METHOD OF STATUS
% POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION
[E]
l 101 81 3 _I I NA a
I NA 7
8 9
10 12 13 44 45 46 80 FORM OF ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE 12
[
z ZJI NA NA 7
8 9
10 11 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION 301 01 01 Lz I I NA 7
8 9 11 12 13 80 PERSONNEL INJURIES NUMBER DESCRIPTION ME] 101 01 01 I NA 7
8 9 11 12 80 OFFSITE CONSEQUENCES NA 7
8 9 80 LOSS OR DAMAGE TO FACILITY TYPE DESCRIPTION I
LJ I
NA 7
8 9 10 80 PUBLICITY l17 IEvent released to standard publicity list.
7 8 9 80 ADDITIONAL FACTORS (Event Description continued) 16 Isupply.
Redundant systems were not available.
This event is nonrepetitive.
7 6 9 80 Reference Station Incident 76-22.
7 8 9 f80 H. L. Ottoson PHONE: (714) 492-7700 NAME:
PHGPOO88 GPO 88e1.66 7