ML19210E723
| ML19210E723 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/16/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Arenal A SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 7912110517 | |
| Download: ML19210E723 (1) | |
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UNITED STATES
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SulTE 202. WALNUT CREEK PLAZA WALNUT CREEK. CALIFORNI A 94596 November 16, 1979 Docket flos. 50-206 50-361 50-362 Southern California Edison Company P. O. Box 800 2244 Walnut Grove Avenue Rosemead, California 91770 Attention: Mr. A. Arenal, Vice President Advanced Engineering Gentlemen:
This Information flotice is provided as an early notification of a possibly significant matter.
It is expected that recipients will distribute this Notice to their cperating 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 NRC Regional Office.
Sincerely, V
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% R. H. Engelken Director
Enclosures:
1.
IE Information Notice No. 79-29 2.
List of IE Information Notices Recently Issued cc w/ enclosures:
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7910250490' UNITED STATES gof NUCLEAR REGULATORY CC m ISSION OFFICE OF INSPECTION AND ENFORCE!'FNT WASHINGTON, D. C.
20555 Dn cp November 16, 1979 DLui IE Information Notice No. 79-29 LOSS OF NONSAFETY-RELATED REACTOR COOLANT SYSTEM INSTRU!iENTATION DURING OPERATION This notice contains infonnation regarding a loss of reactor coolant system instrumentation as a consequence of a failure of a static transfer switch to transfer to an alternate sucoly.
At 3:15 p.m. on November 10 with Unit 3 of the Oconee Station at 100 oercent power, the main condensate punps tricoed, apparently as a result of a technician performing maintenance on the hotwell level control system. This led to reduced feedwater flow to the steam 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 p.m.,
the inverter power sucoly, nonsafety-related, feeding all oower to the integrated control system (ICS) tripped and failed to automatically transfer its loads from the DC power source to the regulated AC cower source. The inverter had tripped due to blown fuses, resulting in loss of RCS indicators and recorders in the control room, except one wide range RCS pressure recorder.
This condition existed for approximately three minutes, until an ocerator could reach the equipment roon and switch the inverter manually to the regulated AC source. As a result of the oower 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 ocerator, expecting this condition, started all makeuo pumps and ooened the associated high pressure injection valves to the RCS which limited the rate of RCS oressure reduction and associated reduction in pressurizer level. At 3:20:42 o.n.,
oower was restored to the ICS and RCS conditions were restored.
Althounh RCS cooldown limits were exceeded, the cressurizer and steam generators did not go dry, and at least 79 degrees F subcoolina was maintained durino this event. No engineered safety features actuation setpoints were reached, and, except for the conponents 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 suoply should the original static switch fail to transfer.
Longer term resolution of the need or desirability to seaarate these instruments onto diverse electrical supplies or to nrovide redundant instrumentation display channels for operator use from essential power sucolies are also under 1533 062
IE Infomation Notice No. 79-29 Flavenber 16, 1979 Page 2 of 2 consideration.
It is anticioated that further MRC evaluations will result in issuance of an IE Circular, pulletin, or MRR Generic letter in the near future which will recommend or recuest saecific acolicant or licensee actions.
This Infomation Notice is provided to infom licensees of a oossibly sionificant matter.
It is excetted that recioients will disseminate the infomation to all ocerational cersonnel workina at their licensed facilities.
If you have cuestions regardino this ratter, clease contact the Director of the approcriate NRC Regional Office.
No written response to this Infomation Notice is recuired.
1533 063
IE Information Notice No. 79-29 Enclosure November 16, 1979 RECENTLY ISSUED IE I?lFOP?iATI0tl NOTICES Informa tion Subject Gate Issued To Notice flo.
Issued 79-28 Overloadino of Structural 11/16/79 All cower reactor facilities Elements Oue to Pioe Suncort with an OL or CP Loads 79-27 Steam Generator Tube 11/16/79 All cower reactor facilities Ruotures At Two PWR holding OLs and cps Facilities79-12A Attemoted 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 cower reactor facilities Integrity holding CLs and cps 79-25 Reactor Trips At Turkey 10/1/79 All oower facilities with Point l' nits 3 And 4 an OL or a CP 79-24 Overpressurization Of 10/1/79 All oower reactor facilities Containment Of A PWR Plant with a CP After A f*ain Stean Line Break 79-23 Emergency Diesel Generator 9/26/79 All power reactor Lube Oil Coolers facilities holding OLs and cps 79-22 Qualification of Control 9/1d/79 All oower reactor Systems facilities with operating licenses and construction oernits.
79-21 Transoortation and Commercial 9/7/79 All cower and research Burial of Radioactive aterial 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 Ocerators 1533 064