ML19317F845
| ML19317F845 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 09/24/1975 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML19317F846 | List: |
| References | |
| NUDOCS 8002210589 | |
| Download: ML19317F845 (1) | |
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' SACRAMENTO MUNICIPAL UTILITY DISTRICT D 6201 S Street. Box 15830. Sacramento. California 95813: (916) 452 3211 September 24, 1975 Mr. R. H. Engelken Director of Regulatory Operations Region V NRC Operations Office si 1990 N. California Boulevard Walnut Creek Plaza, Suite 202 Walnut Creek, California 94596 Re: Operating License DPR-54 Docket No. 50-312 i
Abnormal occurrence 75-13
Dear Mr. Engelken:
p As' defined by proposed Amendment No. 30 to Technical Specificntions
i for the Rancho Seco Nucicar Generating Station, Section 6.9.1 and Regulatory
- Cuide 1.16, Revision 3, Section C.2.B.2, we are reporting the following J
Abnormal Occurrence as A0-75-13.
1 O
A surveillance test of the Diesel Generators safety features actuation i
(
was being performed on September 3, 1975. The plant was-in a cold shutdown for maintenance with the "A" Decay Heat Removal System in service. During the course of the test Breaker 52-3B06 blew a fuse and failed to cycle, pre-venting operation of a "B" diesel vent fan. Investigation into the cause of i
the failure revealed a missing internal spacer on a stationary conta'et in-one of the relay circuits, a Westinghouse Type MG-6, Model #288B977A19, General'.
and Specific Purpose Relay. The missing spacer allowed the stationary contact?
to travel forward approximately 1/4" and contact a crimped lug on a negative contact. This effectively placed 125 volts DC across the relay contacts, destroying them and preventing the 52-3B06 relay from operating.
The relay was repaired and the ' fuses replaced, returning Breaker 52-3B06 to operation. The surveillance test was again performed on September 5, 1975 to test the system, which operated correctly.
The cause of this equipment failure was the omission of a spacer during the assembly of a relay. An inspection of simi W relays for a similar omission
]
will be performed to prevent recurrence of thi4 wul.
There was no plant transient associated with this occurrence.
Respectfully,
- .f)
A a
Enclosure.
J. J. Mattimoe
- [mI Director, MIPC(3)
Assistant General Manager
~ C I ces:.Directo'r', IE(30) and Chief Engineer 8 0 02 210 N7 COPY SENT REGION 9
AN. ELECTRIC $
- TEM S E RVIN G M O R E T H A N - 6 0 0.0 0 0 IN.T H E HEART OF CALIFO R N I A
.