ML19210E721
| ML19210E721 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 11/16/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7912110510 | |
| Download: ML19210E721 (1) | |
Text
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UNITED STATES y ','g,.g g NUCLEAR REGULATORY COMMISSION g !.u.t HEGION V
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1990 N. C ALIFORNI A BOULEVARD o,
M n' SUITE 202, WALNUT CRECK PLAZA e,,,e WALNUT CRE E K, CALIFORNI A 94593 November 16, 1979 Docket Nos. 50-133 50-275 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94105 Attention:
Mr. Philip A. Crane, Jr.
Assistant General Counsei Gentl emen:
This Information Notice is provided as an early notification of a possibly si9nificant 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 action or response is requested at this time.
However, we anticipate that further NRC evaluations will result in issuance of an IE Circular, Bulletin, or NRR Generic Letter 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 fiRC Regional Office.
Sincerely, e
u R. H. Engelken Director
Enclosures:
1.
IE Information Notice No. 79-29 2.
List of IE Information Notices Recently Issued
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.v o November 16, 1979 IE Infomation Notice Fo. 79-29 LOSS OF NONSAFETY-RELATED REACTOR COOLANT SYSTEM INSTPUMENTATION DURING OPERATION This notice contains infomation regarding a loss of reactor coolant systen instrumentation as a consequence of a failure of a static transfer switch to transfer to an alternate supply.
At 3:15 p.m. on November 10 with Unit 3 of the Oconee Station at 100 oercent power, the main condensate pumps tripped, apparently as a result of a technician performing maintenance on the hotwell level control systen. This led to reduced feedwater flow to the stean cenerators, which resulted in a high reactor coolant system (RCS) pressure reactor trip and simultaneous turbine trip at 3:16:57 o.m.
At 3:17:15 o.n., the inverter power sucoly, nonsafety-related, feeding all power to the inteqrated control systen (ICS) tripped and failed to automatically transfer its loads fron the DC power source to the regulated AC power source. The inverter had tripped due to blown fuses, resultino in loss of RCS indicators and recorders in the control roon, exceot one wide range RCS pressure recorder.
This condition existed for approximately three minutes, until an onerator could reach the equipnent roon and switch the inverter nanually to the regulated AC source. As a result of the power failure to the ICS, all valves controlled by the system assured their respective fail cositions. This resulted in a cool down of the RCS to 1635 psi and 530 degrees F.
The coerator, expecting this condition, started all makeuo punos and ooened the associated high pressure injection valves to the RCS which limited the rate of RCS pressure reduction and associated reduction in pressurizer level. At 3:20:42 p.n.,
power was restored to the ICS and RCS conditions were restored.
Althouah RCS cooldown limits were exceeded, the pressurizer and steam generators did not go dry, and at least 79 degrees F subcooline was raintained durina this event. No engineered safety features actuation setnoints were reached, and, except for the components discussed above, no component malfunc-tions occurred.
The licensee has installed a redundant electromechanical transfer switch between the loads and the regulated supply. This switch will actuate and power the loads from the regulated sunply should the original static switch fail to transfer.
Longer tem resolution of the need or desirability to seoarate these instrunents onto diverse electrical supplies or to nrovide redundant instrumentation display channels for operator use from essential power suonlies are also under 1533 066
IE Information Notice No. 79-29 Novenber 16, 1979 Page 2 of 2 consideration.
It is anticipated that further NRC evaluations will result in issuance of an IE Circular, Bulletin, or NRR Generic letter in the near future which will recommend or request specific aoolicant or licensee actions.
This Information Notice is provided to inforn licensees of a nossibl.y sianificant matter.
It is expected that recinients will dissaninate the information to all operational personnel workina at their licensed facilities.
If you have questions regarding this natter, olease contact the Director of the approoriate NRC Regional Office.
No written response to this Infornation Notice is required.
1533 067
IE Information Notice No. 79-29 Enclosure Nover ber 16, 1979 RECENTLY ISSUED IE INF0F11ATION NOTICES Informatinn Subject Date Issued To Notice flo.
Issued 79-28 Overloadina of Structural 11/16/79 All power reactor facilities Elemants Due to Pine Suncort with an OL or CP Loads 79-27 Stean Generator Tube 11/16/79 All cover reactor facilities Ruotures At Two PWR holding OLs and cps Facilities79-12A Atterated Damage To New 11/9/79 All Fuel Facilities, Fuel Assemblies research reactors, and power reactors with an OL or CP 79-26 Breach of Containment 11/5/79 All oower reactor facilities Integri ty holdina OLs and cps 79-25 Reactor Trips At Turkey 10/1/79 All cover facilities with Point Units 3 And 4 an OL or a CP 79-24 Overpressurization Of 10/1/79 All oower reactor facilities Containnent Of A PWR Plant with a CP After A fiain Stean Line Break 79-23 Eneraency Diesel Generator 9/26/79 All power reactor Lube Oil Coolers facilities holding OLs and cps 79-22 Qualificaticn of Control 9/14/79 All power reactor Systems facilities with operatina licenses and construction pen,its.
79-21 Transoortation and Connercial 9/7/79 All power and research Burial of Radioactive 'faterial reactors with OL's 79-20 NRC Enforcement Policy 9/7/79 All Holders of Reactor (Rev. 1)
NRC Licensed Individuals OLs and cps and Production Licensees with Licensed Operators 1533 068