ML19259D271
| ML19259D271 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 10/01/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7910170536 | |
| Download: ML19259D271 (1) | |
Text
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UNITED STATES e8y
,(y' j NUCLEAR REGULATORY COMMISSION 5."
Me REGION V I
1990 fJ. CALIFORNI A BOULEVARD
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WALNUT CREE K, CALIFORtJI A 94596 October 1, 1979 Docket Nos. 50-133 50-275 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention: Mr. Prdlip A. Crane, Jr.
Assistant General Counsel Gentlemen:
This Information Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the information for possible applicability to their facilities.
No specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular, Bulletin, or Generic Letter will be issued to recommend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, 0f5 m ek-R. H. Engelken Director
Enclosures:
1.
IE Information Notice 79-25 2.
List of IE Information Notices Issued in Last Six Months cc w/ enclosures:
W. Barr, PG&E W. Raymond, PG&E
\\}bd db9 R. Ramsay, PGSE, Diablo Canyon E. Weeks, PGSE, Humboldt Bay J. Worthington, PG&E 7910170 %
Accession fo.: 7908220125 SSINS No.: 6870 UNITED STATES NUCLEAR REGULATORY COMMISSI0il 0FFICE OF INSPECTION AND ErlFORCEMENT WASHINGTON, D.C.
20555 October 1, 1979 IE Information Notice 79-25 REACTOR TRIPS AT TURKEY POINT UNITS 3 AND 4
Background
an August 3, Turkey Point Units 3 and 4 tripped while operating at full power.
A voltage spike on a second protection channel caused Unit 4 to trip during surveillance testing on the reactor protection system.
This resulted in a loss of offsite power and subsequent shedding of non-essential loads.
Unit 3 tripped as the result of high coolant pressure caused by a turbine runback.
Discussion While performing a periodic test on channel "C" of the T-Average and Delta T Protection Channels, a spurious signal on channel "A" completed a 2 out of 3 trip logic: tripping Unit 4.
This resulted in a loss of offsite power condi-tion for Unit 4.
At this time, the Unit 4 startup transformer was out of service due to performance of periodic maintenance.
This condition caused the.
initiation of the emergency diesel generator load sequencer which resulted in the shedding of non-vital loads. Among the non-vital loads shea,,;are those on flotor Control Center (MCC) "D" which is common to both units.
Since the Rod Position Indication System for both units is powered by the non-vital portion of MCC-D, a turbine runback on Unit 3 was initiated upon loss of rod position indication.
This resulted in a reactor trip on high pressurizer pressure. At the time, neither of the two pressurizer spray valves was avail-able. One was considered inoperable prior to the transient and the other, temporarily powered by the non-vital portion of MCCD, had become unavailable earlier as a consequence of the Unit 4 trip.
A subsequent review disclosed inadequacies in the administrative controls over the correction of operational problems exhibited by spray valve PCV-3-455B.
The original Hagan controller for spray valve PCV-3-455B had been disconnected and was replaced by another manual controller which was plugged into the valve control circuit and which had been taped to the top of a console in the main control room.
The actual installation nf tho manual enntroller was not performed under established guideline had been issued to ensure consistent operational control of this unusual c DUPLICATE DOCUMENT Entire document previously l}f)
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