ML19270F690
| ML19270F690 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 02/16/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Mary Johnson SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 7903080555 | |
| Download: ML19270F690 (1) | |
Text
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FEB 161979 In Reply Refer To:
RII:JPO 50-395 South Carolina Electric anu Gas Company Attn:
Mr. M. C. Johnson, Vice President and Group Executive - Special Services and Purchasing P. O. Box 764 Columbia, South Caroline 29202 Ge... l eme n :
This Information Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the infor-mation for possible applicability to their facilities.
No specific action or response is requested at this time.
If further h3C evaluations so indicate, an IE Circular, Bulletin or NRR Generic Letter will be issued to recomend 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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James P. O'Reilly 0'R-Di re c t o r
Enclosures:
1.
IE Information Notice No. 79-04 2.
List of IE Information Notices Issued in 1979 7903080666
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 February 16, 1979 IE Information Notice No. 79-04 DEGRADATION OF ENGINEERED SAFETY FEATURES Summary On September 16, 1978, an unusual sequence of events occurred at Arkansas Nuclear One, Units 1 and 2.
The events involved the electrical power sources and culminated in the spuricus activation and degraded operation of Unit 2 Engineered Safety Features (ESF). Analysis of the course of the incident has identified three safety concerns in the electrical distribution system operation and design.
(1) The offsite power supply for ANO Unit 1 Engineered Safety Feature loads was deficient ia that degraded voltage could have resalted in the unavailability of ESF equipment, if it were to be needed.
(2) The design of the ANO site electrical system that provides offsite power to Units 1 and 2 did not fully meet the Commission's Regula-tions, 10 CFR 50, Appendix A, General Design Criterion 17, because in certain circumstances a loss of one of the two offsite 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 I was operating at 100 percent power; Unit 2 was in hot standby performing hot functiona criticalityandpoweroperation.}testinginpreparationforinitial Unit I auxiliary electrical loads were being supplied from the Unit 1 main generator via the unit auxiliary transformer.
Unit 2 auxiliary electrical loads were being fed from the offsite grid through Startup Transformer No. 3.
The normal operating status was interrupted by the failure of the Unit 1 Loop "A" Main Steam Line Isolation Valve (MSIV) air operator solenoid causing the MSIV to close as designed. The Unit 1 Reactor Protection System sensed conditions requiring reactor shutdown and tripped the reactor.
The The Unit 2 Operating License did not permit criticality of power operation at the time of the incident,
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