ML19274C937
| ML19274C937 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/29/1978 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Johari Moore SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 7901080013 | |
| Download: ML19274C937 (1) | |
Text
- eN UNITED STATES "4' q
- *e NUCLEAR REGULATORY COMMISSION
)d REGION V SulTE 202, WALNUT CREEK PL AZA 0
1990 N, C AllFORNI A BOULEVARD
+9***>*9 WALNUT C REEK, C ALIFORNI A 94596 DEC 2 9 F50 Docket Nos. 50-361 50-362 Southern California Edison Company P. O. Box 800 2244 Walnut Grove Avenue Rosemead, California 91770 Attention: Mr. Jack B. Moore Vice President Gentlemen:
The enclosed Circular 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, hdqefb R. H. Engelken Director
Enclosures:
1.
IE Circular No. 79-19 2.
List of IE Circulars Issued in 1978 cc w/encls.
J. M. Curran, SCE J. T. Head, SCE J. H. Drake, SCE 79010800C$
s IE Circular No. 78-19 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 energized a relay which blocked the safety signal 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 operation 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.1 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. Override of the containment isolation signal was accomplished by resetting the train A and B reset buttons. Under these circumstances, six valves in the containment vent and purge systems could be opened with a high particulate isolation signal present. This override was performed after verifying that the actual containment particulate levels were acceptable 4
7901040236
IE Circular No. 78-19 December 29, 1978 Page 2 of_2 for venting. The licensee, after further investigation of this practice, determined that the reset of the particulate alarm also bypasses the containment isolation signal to the purge valves and that the purge valves would not have automatically closed in the event of an emergency core cooling system (ECCS) safety injection signal.
These events and information gained from recent licensing actions have raised a generic concern relative to potential design deficiencies that could permit manually defeating a protection function. Since all plants with construction permits must meet the requirements of IEEE 279, we recommend that you review the design of all_ safety actuation signal circuits which incorporate a manual override feature to ensure that overriding of one safety actuation signal does not also cause the bypass of any other safety actuation signal, that sufficient physical features are provided to facilitate adequate administrative controls, and that the use of each such manual override is annunciated at the system level for every system impacted.
Compliance with Federal Regulation 50.55a(h) requirements will be ver.ified by NRC through the licensing review process and during regular onsite inspections for plants with construction permits. NRC's requirements relative to this matter have been conveyed to all operating plant licensee's via a generic letter.
No written response to this Circular is required.
If you require additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
IE Circular No. 78-19 December 29, 1978 LISTING 0F IE CIRCULARS ISSUED IN 1978 Circular Subject Date Issued To Ho.
of Issue 78-01 Loss of Well Logging 4/5/78 All Holders of Source Well Logging Source Licenses 78-02 Proper Lubricating Oil 4/20/78.
All Holders of for Terry Turbines Reactor OLs or cps 78-03 Packaging Greater Than 5/12/78 All Holders of Type A Quantities of Reactor OLs, cps, Low Specific Activity Fuel Cycle, Radioactive Material Priority I Material for Transport and Waste Disposal Licenses 78-04 Installation Error That 5/15/78 All Holders of Could Prevent Closing of Reactor OLs or Fire Doors cps 78-05 Inadvertent Safety Injection 5/23/78 All Holders of During Cooldown Reactor OLs or cps 78-06 Potential Common Mode 5/23/78 All Holders of Flooding of ECCS Equipment Reactor OLs or Rooms at BWR Facilities cps 78-07 Damaged Components of a 5/31/78 All Holders of Bergen-Paterson Series Reactor OLs or 25000 Hydraulic Test cps Stand 78-08 Environmental Qualification 5/31/78 All Holders of of Safety Related Equipment Reactor OLs or at Nuclear Power Plants cps 78-09 Arcing of General Electric 6/5/78 All Holders of Company Size 2 Contactors cps Enclosure Page 1 of 2
IE Circular tio. 78-19 December 29, 1978 LISTING 0F IE CIRCULARS ISSUED Ill 1978 Circular Subject Date of Issued to N o..
Issue 78-10 Control of Sealed 6/14/78 All Medical Sources Used in Licensees in Radiation Therapy Categories G and G1 78-11 Recirculation M-G 6/15/78 All Holders of Set Overspeed Stops BWR OLs or cps 78-12 HPCI Turbine Control 6/30/78 All Holders of Valve lift Rod Bending BWR OLs or cps for plants with HPCI Terry Turbine 78-13 Inoperability of Multiple 7/10/78 All Holders of Service Water Pumps Reactor OLs and cps except for plants located in: AL, AK, CA, FL, GA, LA, MS, SC 78-14 HPCI Turbine Reversing 7/12/78 All Holders of BWR Chamber Hold Down Bolting OLs or cps for plants wito a HPCI Terry Turbine excepting Duane Arnold and Monticello 78-15 Checkvalves Fail to 7/20/78 All Holders of Close In Vertical Reactor OLs or cps Position 78-16 Limitorque Valve 7/26/78 All Holders of Reactor OLs or cps Actuators 78-17 Inadequate Guard Training /
10/13/78 All Holders of and Qualification and Falsified applicants for Training Records Reactor Ols 78-18 UL Fire Test 11/6/78 All Holders of Reactor Ols or cps Enclosure Page 2 of 2