ML19290E681
| ML19290E681 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 03/07/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8003140374 | |
| Download: ML19290E681 (2) | |
Text
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UNITED STAT ES e! 'y
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' 'g NUCLEAR REGULATORY COMMISSION E <
REGION V
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1990 N. CALIFORNIA 000LEVARD o, 1
,o SUITE 202, WALNUT CREE K PLAZA D
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WA LNUT CR E E K, CAllF ORNI A 94596 fiarch 7,1980 Docket flos. 50-133, 50-275 & 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention: fir. Philip A. Crane, Jr.
Assistant General Counsel Gentlemen:
This Information flotice is provided as an early notification of a possibly signifi ant matter.
It is expected that recipients will distribute this flotice 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 flRC Regional Office.
Sincerely, 6{ YmtSL R. H. Engelken Director
Enclosures:
1.
IE Information flotice flo. 80-10 2.
List of IF Information flotices Recently Issued cc w/ enclosures:
W. Barr, PG&E W. Raymond, PG&E R. Ramsay, PG&E, Diablo Canyon E. Weeks, PG&E, Humboldt Bay E. B. Langley, Jr., PG&E 8o03140379
SSIf1S flo. :
6870 UtlITED STATES Accession No.:
flUCLEAR REGULATORY COMMISS10fl 8002280640 0FFICE OF IflSPECTI0ft Afl0 ErlFORCEMEilT WASHillGT0ft, D.C.
20555 March 7, '680 IE Information Notice flo. 80-10 PARTIAL LOSS OF il0ft-flUCLEAR IflSTRUMEllT SYSTEM POWER SUPPLY DURIf,G OPERATION Description of Circunstances:
This notice contains information regarding Crystal River Unit 3 response to a loss of non-nuclear instrumentation (ftfil) as a consequence of loss of the
+24 volt power supply to the flill.
At 2:23 p.m. on February 26 with Crystal River Unit 3 at 100% pcwer, the
+24 volt power supply to the fifil was lost, due to a short to ground. This initiated a sequence of events (detailed in the enclosu e) wherein the PORV opened and stayed open as a direct result of the titlI pswer supply loss.
HPI initiated as a result of depressurization through the open PORV, and with approximately 70% of fillI 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 flovember 10, 1979 event at Oconee Unit 3 wherein the inverter supplying power to the Integrated Control System (ICS) and to parts of the fillI failed.
That event was the subject of IE Information flotice 79-29.. (flovember 16,1979) which was followed by IE Culletin 79-27 (flovember 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 adjacert 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 printed circuit card. Subsequent r
+"
voltage buffer card which was also The specific circuit cards which we The connectors on these cards are s DUPLICATE DOCUMENT different angle than those found on carry part numbers 6624608A1 or 662 Entire document previously more subject to misalignment.
entered into system under:
M hh ANO No. of pages:
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