ML19282A950
| ML19282A950 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 02/16/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Tallman W PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| References | |
| NUDOCS 7903080389 | |
| Download: ML19282A950 (1) | |
Text
b UNITED STATES M
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NUCLEAR REGULATORY COMMISSION y
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REGION I o
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,s,.(j KING OF PRUSSI A, PENNSYLVANI A 19406 February 16, 1979 Docket Nos. 50-443 50-444 Public Service Company of New Hampshire ATTN: Mr. W. C. Tallman President 1000 Elm Street Manchester, New Hampshire 03105 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.
No specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular or Bulletin or NRR Generic Letter will be issued to recommend or request specific licensee actions.
If you have questions regarding the matter, please contact this office.
Sincerely, h
Boyce H. Grier Director
Enclosures:
1.
IE Information Notice No. 79-04 2.
List of IE Information Notices Issued in 1979 cc w/encls:
John D. Haseltine, Project Manager 7903080380
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Infonnation Notice No. 79-04 Date:
February 16, 1979 Page 1 of 5 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 spurious activation and degraded operation or 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 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 1 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 1 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 Transfonner 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 NSIV to 1
The Unit 2 Operating License did not permit criticality or power operation at the time of the incident.
7903020383