ML19282A949
| ML19282A949 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 02/16/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Bryan J UNION ELECTRIC CO. |
| References | |
| NUDOCS 7903080386 | |
| Download: ML19282A949 (1) | |
Text
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UNITED STATES f, ',", ' th NUCLEAR REGULATORY COMMISSION 1
., s REGION 111 g3 y
799 ROOSEVELT ROAD GLEN E LLYN, ILLINol5 601:s1 4
g,r FEB 16 Ji9 Docket No. 50-483 Docket No. 50-486 Union Electric Company ATTN:
Mr. John K. Bryan Vice President - Nuclear P. O. Box 149 St. Louis, MO 63166 Gentlemen:
Thls Infornation 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 h3C evaluations so indicate, an IE Circular, Bulletin or NRR 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.
Sincerely, hh M-hv
(/JamesG.Ke[ pier Director
Enclosures:
1.
IE Information Notice No. 79-04 2.
List of IE Information Notice Issued in 1979 cc w/encls:
Mr. W. H. Weber, Manager, NSIC Nuclear Construction TIC Central Files Region I & IV Director, NRR/DPM Ms. K. Drey Director, NRR/ DOR Hon. C. J. Frass, Chairman PDR Missouri Public Service Local PDR Commission 7 9 0 3 0 8 03gG:,
U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III February 16, 1979 IE Information Notice No. 79-n4 DEGRADATION OF ENGINEERED SAFETY FEATURES Su= mary 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 spurious 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 in that degraded voltage could have resulted 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 certa!n 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 functional testing in preparation for initial criticality and power operation.1 Unit I auxiliary electrical loads were being supplied from the Unit I 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 (hSIV) 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 1 The Unit 2 Operating License did not permit criticality or power operation at the time of the incident.
gg 7903020383