ML19282B123
| ML19282B123 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 02/16/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 7903090044 | |
| Download: ML19282B123 (1) | |
Text
gn af 00 UNtTED STATES ef
'o NUCLEAR REGULATORY COMMISSION
[
o.
REGION IV 5..
E Gil RYAN PLAZA DRIVE, SUITE 1000 AR LINGTON, TEXAS 76011 k*****/
February 16, 1979 In Reply Refer To:
RIV Docket Nos. 50-498/IE Information Notice fio. 79-04 50-499/IE Information Notice No. 79-04 Houston Light'ng & Power Company ATTN:
Mr. E. 4. Turner, Vice President Power F lant Construction and TecN cal Services Post Office 1:-
1700 Houston, Texai 77001 Gentlemen:
j 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.
fio specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular, Bulletin or NRR 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 NRC Regional Office.
Sincerely, f },
y.
,. j
,fg j., ' -. j *.?':l.- Q Karl V. Seyfrit
/
Director
Enclosures:
1.
IE Infomation Notice No. 79-04 2.
List of IE Information Notices Issued in 1979 79030900 %
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Information 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 of Unit 2 Engineered Safety Features (ESF).
Analysis of the course of the incident has identified three safety ccncerns 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 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 1/ The Unit 2 Operating License did not permit criticality of power operation at the time of the incident.
03 f 6 7903020383