ML19290E685
| ML19290E685 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/07/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Papay L SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 8003140379 | |
| Download: ML19290E685 (2) | |
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UNITED STATES 8\\
NUCLEAR REGULATORY COMMISSION 5
REGION V 8
1990 N. CALIFORNI A BOULEVARD o
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SUITE 202, WALNUT CREE K PLAZA WALNUT CREE K, calif 0RNI A 94596 March 7, 1980 Docket Nos. 50-206, 50-361 & 50-362 Southern California Edison Company P. O. Box 800 2244 Walnut Grove Avenue Rosemead, California 91770 Attention: Dr. L. T. Papay, Vice President Advanced Engineering Gentlemen:
This Information Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will distribute this Notice to their operating personnel and will review the information for possible applicability to their facilities.
No specific response is requested at this time.
However, we anticipate that further NRC evaluations will result in issuance of an Addendum to IE Bulletin 79-27 in the near future which will recommend or request specific applicant or licensee actions.
If you have questions regarding the matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, fS75,c C -
R. H. Engelken Director Enclosures :
1.
IE Information Notice No. 80-10 2.
List of IE Information Notices Recently Issued cc w/ enclosures:
J. M. Curran, SCE R. Dietch, SCE 8 0 0314 0 37q
SSINS No.: 6870 UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8002280640 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 March 7, 1980 IE Information Notice No. 80-10 rJ.TIAL LOSS OF NON-NUCLEAR INSTRUMENT SYSTEM POWER SUPPLY DURING OPERATION Description of Circumstances:
This notice contains information regarding Crystal River Unit 3 response to a loss of non-nuclear instrumentation (NNI) as a consequence of loss of the
+24 volt power supply to the NNI.
At 2:23 p.m. on February 26 with Crystal River Unit 3 at 100% power, the
+24 volt power supply to the NNI was lost, due to a short to ground.
This initiated a sequence of events (detailed in the enclosure) wherein the PORV opened and stayed open as a direct result of the NNI power supply loss.
HPI initiated as a result of depressurization through the open PORV, and with approximately 70% of NNI inoperable or inaccurate, the operator correctly decided that there was insufficient information available to justify terminating HPI. Therefore, the pressurizer was pumped solid, one safety valve lifted, and flow through the safety valve was sufficient to rupture the RC Drain Tank rupture disk, spilling approximately forty-three thousand gallons of primary water into containment.
The Crystal River 3 event is closely related to the November 10, 1979 event at Oconee Unit 3 wherein the inverter supplying power to the Integrated Control System (ICS) and to parts of the NNI failed. That event was the subject of IE Information Notice 79-29..(November 16,1979) which was followed by IE Bulletin 79-27(November 30,1979).
The CR-3 event involved loss of only part of the power available from an inverter, rather than the inverter itself, since the +24v supply is only one of several power supplies drawing power from one inverter.
The effects are very similar, however, in that the ICS lost part of its input signals in both events.
The +24 volt power supply short to ground has tentatively been identified by the licensee to have occurred between knife edge connectors of a Bailey Control Company Voltage Buffer Card. The voltage buffer card was misaligned in its receptacle, and adjacent connectors carrying +24v and " common" were bent such that they contacted one another. This short circuit cleared itself during subsequent re-energizing of the power supply by burning through the foil on a
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printed circuit card.
Subsequent t
voltage buffer card which was also The specific circuit cards which w The connectors on these cards are DUPLICATE DOCUMENT different angle than those found o Entire document previously carry part numbers 6624608A1 or 66 entered into system under:
more subject to misalignment.
b ANO N o.
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