ML19282B125
| ML19282B125 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/16/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 7903090047 | |
| Download: ML19282B125 (1) | |
Text
km neou UNITED STATES
'o NUCLEAR REGULATORY COMMISSION f
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REciON iv 5
.., E 611 RYAN PLAZA DRIVE,SulTE 1000
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s, February 16, 1979 In Reply Refer To:
RIV Docket flos.
50-445/IE Infomation flotice flo. 79-04 50-446/IE Information flotice flo. 79-04 Texas Utilities Generating Company ATTil: fir. R. J. Gary, Executive Vice President and General flanager 2001 Bryan Tower Dallas, Texas 75201 Gentlemen:
This Infomation flotice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the infomation for possible applicability to their facilities. flo specific action or response is requested at this time.
If further flPC evaluations so indicate, an IE Circular, Bulletin or flRR Generic Letter will be issued to recommend or request specific licensee action.
If you have questions regarding this matter, please contact the Director of the appropriate flRC Regional Office.
Sincerely, l-D.
-4,;,. "i.. gu 2
Karl V. Seyfr,i,t Director
Enclosures:
1.
IE Infomation Notice flo. 79-04 2.
List of IE Infomation flotices Issued in 1979 7903090047' n
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.h UNITED STATES NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555
.%.g IE Information Notice No. 79-04 Date:
February 16, 1979 Page 1 of 5 DEGRADATION OF ENGINEERED SAFETY FEATURES Summary:
l 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 coeration 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.
y (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
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.".8 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
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that convert DC to AC power for the uninterruptable 120 volt T
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
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criticality and power operation ]f.
Unit 1 auxiliary electrical loads ga were being supplied from the Unit 1 main generator via the unit
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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" 1
Main Steam Line Isolation Valve (MSIV) air operator solenoid causing the 2
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MSIV to close as designed. The Unit 1 Reactor Protection System sensed conditions requiring reactor shutdown and tripped the reactor.
The
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_1] The Unit 2 Operating License did not permit criticality of power l'
operation at the time of the incident.
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