ML19309A159
| ML19309A159 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/05/1977 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML19309A160 | List: |
| References | |
| NUDOCS 8003260873 | |
| Download: ML19309A159 (2) | |
Text
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, SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street, Box 15830, Sacramento Califomia 95813; (916) 452-3211
.m December 5,1977-
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.a Director of Regulatory Operations, ~.
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Mr. R. H. Engelken O 2j
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Walnut Creek Plaza, Suite 202
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NRC Operations Office, Region V 1990 North California Boulevard
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Re: Operating License DPR-54 Dc,xes. No. 50-312 Reportable Occurrence 77-17 K
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Dear Mr. Engelken:
In accordance with Technical Specifications for Rancho Seco Nuclear Generating Station, Section 6.9.1, and Regulatory Guide 1.16, Revision 4, Section C.2.b(3), the Sacramento Municipal Utility District is hereby reporting
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To conform with new requirenruts for long-term cooling capability, some modifications were made to the high pressure injection system during the.
last refueling outage. A 1-1/2 inch line branching off one of the two high pressure injection lines of the "B" loop provides auxiliary spray to the d
pressurizer for shutdown operations. Motor operators were added to the normally closed valve on the auxiliary spray line and to the high pressure?
injection line stop/ check valve that is immediately downstream of the 1-1/2 inch line. Remote closing of the stop/ check valve and opening the spray line valve permit this line to be used as a backup path to provide recirculation flow through the core. During power operation, the proper position for the stop/ check valve is open (operator breaker racked out) while the spray line valve remains closed.
On November 11, 1977, with the plant at 78 percent full gower, the
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shift supervisor checked the position of HV-23802 (spray line valve) as indi-cated by the backlighted pushbutton. This new switch had been installed with Z
the closed position on top, a complete reversal of standard control room practice which has the open indication on top and the closed on the bottom.
This inverted switch was misread, leading the shift supervisor to think that HV-23802 was open. While not in itself an unsafe condition, this led to restoring power to HV-23801 (stop-check valve) to check its position. The same error was made in reading the position of this valve, which gave the false impression that the high pressure injection line was isolated. Both valves were repositioned at 1800, and the shift supervisor prepared a reporrable p) occurrence report and notified the Assistant Superintendent.
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AN ELECTRIC ~ $4 STEM SERVfN3 MORE THAN 600,000 IN THE HEART 3F C Ali F 0 R N I A
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f, M'. R. H. Engelken December 5, 1977 r
The following day, a surveillance procedure required verification of flow through the HPI lines and the closed stop/ check valve was discovered. The valves were properly positioned at 1220 on November 12, restoring the one iso-laced HPI line to service.
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- t During this period when the valve was positioned incorrectly, high pressure injection was available through both lines in the A loop and the open line in the B loop.
Injection flow also would have occurred through the open 1-1/2 inch line into the pressurizer.
Since no testing has been performed to verify that injection flow through one 2-1/2 inch injection line and the spray line is adequate, it is assumed that some reduction in the redundancy existed.
a i To prevent possible recurrence of this incident, the new switches will be invarted so they conform to standard practice. Also, the circuitry for the stop/ check valve, for the new long-term cooling valve which allows
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drainage to the emergency sump, and for the two core flood tank vest valves will be modified to retain control room panel indication of valve position ~
with the breaker racked out.
1 There was no plant shutdown or transient as a result of this
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occurrence.
l Respectfully submitted,
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J. J. Mattimoe Assistant General Manager
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and Chief Engineer JJM:FTE: jim cs:
Director, MIPC (3)
Director, IE (30)
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