ML19296A394
| ML19296A394 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 02/16/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 7903190520 | |
| Download: ML19296A394 (1) | |
Text
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q, NUCLEAR nEGULATonY COS.1?.11SSIO J f
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WALNUT C REEK, C AllFOHNI A 94596 February 16, 1979 Docket No. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager 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.
flo specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular, Bulletin or f;RR Generic Letter will be issued to recommend or request specific licensee actions.
If you have questions regarding the matter, please contact the Director of the appropriate NRC Regional Office.
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R. H. Engelken Director
Enclosures:
1.
IE Information flotice No. 79-04 2.
List of IE Information Notices Issued in 1979 cc w/encls:
R. J. Rodriguez, SMUD L. G. Schwieger, SMUD 7 9 0 319 0 5ao
9 Uf!ITED STATES i'UCLEAR REGULATORY COMMISSIO" 0FFICE OF IllSPECTI0ft Af;D Ef; FORCE".E'.T UASHIfiGT0fl, D.C.
- U555 February 16, 1979 IE Infornatic, Notice fio. 79-04 DEGRADATI0fl 0F Ef;GIflEERED SAFETY FEATURES Summary On September 16, 1978, an unusual sequence of events occurred at Arkansas fluclear One, Units 1 and 2.
The events involved the electrical power sources and culminated in the spurious activation and degraded operation of Unit 2 Engineered Safety Features (ESF). Analysis o# the ccurse c#
the incident has identified three safety concerns ir. the electrical distribution system operation and design.
(1) The offsite power supply for Af;0 Unit 1 Engineered Ea#ety Feature loads was deficient in that degraded voltage could have resulted in the unavailability of ESF equipment, if it v ere tc be needed.
(2) The design of the Afl0 site electrical system that orcvides offsite power to Units 1 and 2 did not fully meet the Cc-ission's Regula-tions,10 CFR 50, Appendix A, General Design Criteri:n 17, because in certain circumstances a loss of one of the two c'# site power circuits would also result in a loss of the other such circuit.
(3) Deficiencies existed in the operation of the Unit 2 inverters that convert DC to AC power for the uninterruptable 120 volt vital AC buses.
Description of Circumstances Initially Unit 1 was operating at 100 percent power; Unit 2 was in hct standby performing hot functional testing in preparaticn for initial criticality and power operation (l) Unit 1 auxiliary electrical loads were being supplied from the Unit 1 main generator via the unit auxiliary transformer. Unit 2 auxiliary electrical leads were being fed from the offsite grid through Startup Transfomer f:o. 3.
The nomal operating status was interrupted by the failure of the Unit 1 Lcop A" Main Steam Line Isolation Valve (fiSIV) air operator solenoid causing the MSIV to close as designed. T hc. Unit 1 Reactor Protection Systen sensed conditions requiring reactar shutdown and tripped the reactor. The 1 The Unit 2 Operating License did not permit criticalit:. of power operation at the time of the incident.
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