ML19256B188
| ML19256B188 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 12/29/1978 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Humphreys L GULF STATES UTILITIES CO. |
| References | |
| NUDOCS 7901240238 | |
| Download: ML19256B188 (6) | |
Text
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UNITED STATES q,
NUCLE AR REGULATORY COMMISSION
[
REGION IV 5'
611 RYAN PLAZA ORIVE, SUITE 1000 f
- +
December 29, 1978 In Reply Refer To:
RIV Docket Nos.
50-458/IE Circular 78-19 50-459/IE Circular 78-19 Gulf States Utilities Attn: Mr. L. L. Humphreys Senior Vice President, Energy Development Post Office Box 2951 Beaumont, Texas 77704 Gentlemen:
The enclosed Circula' 78-19 is forwarded to you for information.
If there are any questions related to your understanding of the requested actions, please contact this office.
Sincerely, fhbb L+-fh Karl V. Seyfrit Director
Enclosures:
1.
IE Circular No. 78-19 2.
List of IE Circulars Issued in 1978 790124 oa%
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular NoO Date:
December 29, 1978 Page 1 of 2 MANUAL OVERRIDE (BYPASS) 0F SAFETY SYSTEM ACTUATION SIGNALS Description of Circumstances:
A review of several recent events has raised questions about safety system circuit designs which incorporate manual override (bypass) features. The two events described below directly relate to the practice of containment purging during normal plant operation by manually overriding containment isolation signals.
In these instances the automatic isolation function of the purge system containment isola-tion valves was unintentionally made inoperable, and this condition was neither continuously indicated in the control room nor known to the plant operators.
During a review of operating procedures on July 25, 1978, the Northeast Nuclear Energy Company discovered that since May 1,1978, intermittent containment purge operations had been conducted at Millstone Unit No. 2 with the safety actuation isolation signals to both inlet and outlet redundant containment isolation valves (48 inch butterfly valves) in the purge inlet and outlet penetrations manually overridden and inoperable.
The isolation signals which are required to automatically close the purge valves for containment integrity were manually overridden to allow purging of containment with a high radiation signal present. The manual override circuitry designed by the plant's architect / engineer defeated not only the high radiation signal but also all other isolation signals to these valves. To manually override a safety actuation signal, the operator cycles the valve control switch to the closed position and then to the open position.
This action energizeo a relay which blocked the safety sigrial and allowed manual operation independent of any safety actuation signal. This circuitry was designed to permit reopening these valves after an accident to allow manual oper,ation of certain safety equipment.
On September 8,1978, the Public Service Electric and Gas Company advised the staff that, as a matter of routine, Salem Unit No. I has been venting the containment through the containment ventilation system valves to reduce pressure.
In certain instances this venting has occurred with the containment high particulate radiation monitor isolation signal to the purge and pressure-vacuum relief valves overridden.
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