ML19256A730
| ML19256A730 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 12/29/1978 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Boyer V PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 7901100005 | |
| Download: ML19256A730 (1) | |
Text
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KING OP PRUS$1 A. PENN5YLVANI A 19404 e
t 631 PARK AVENUE December 29, 1978 Docket Nos. 50-352 50-353 Philadelphia Electric Company ATTN:
Mr. V. S. Boyer Vice President Engineering and Research 2301 Market Street Philadelphia, PA 19101 Gentlemen:
The enclosed IE Circular No. 78-19 is forwarded to you for informa-tion.
No written response is required.
Should you have any questions related to your understanding of this matter, please contact this office.
Sincerely, M
n Boyce H. Grier Director Er.iosures:
1.
IE Circular No. 78-19 2.
List of IE Circulars Issued in 1978 7901100006 Q
1 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 78-19 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 isolation 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 s' itch 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 7901040236
g IE Circular No. 78-19 Date: December 29, 1978 Page 2 of 2 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 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 recomend 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 Regilation 50.55a(h) requirements will be verified 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 Date:
December 29, 1978 Page 1 of 3 ENCLOSURE 2 LIST OF IE CIRCULARS ISSUED IN 1978 Circular Subject First Date Issued To No.
of Issue 78-01 Loss of Well Logging 4/14/78 All Holders of Source Well Logging Source Licenses 78-02 Proper Lubricating Oil 4/20/78 All Power Reactor for Terry Turbines Facilities with an Operating License (0L)orConstruction Permit (CP) 78-03 Packaging Greater Than 5/12/78 All Power Reactor Type A Quantities of Facilities w;th an Low Specific Activity OL or CP; and all Radioactive Material Fuel Cycle, Priority I for Transport Materials and Waste Disposal Licensees 78-04 Installation Errors That 5/18/78 All Power Reactor Could Prevent Closing Facilities with an of Fire Doors OL or CP 78-05 Inadvertent Safety 5/26/78 All PWR Power Injection During Reactor Facilities Cooldown with an OL or CP 78-06 Potential Common Mode 5/31/78 All Power Reactor Flooding of ECCS Facilities with an Equipment Rooms at OL or CP BWR Facilities 78-07 Damaged Components on a 5/31/78 All Power Reactor Bergen-Paterson Series Facilities with an 25000 Hydraulic Test Stand OL or CP 78-08 Environmental Qualifica-5/31/78 All Power Reactor tion of Safety-Related Facilities with an Electrical Equipment at OL or CP Nuclear Power Plants
IE Circular No. 78-19 Date: December 29, 1978 Page 2 of 3 ENCLOSURE 2 (Co'icinued)
LIST OF IE CIRCULARS ISSUED IN 1978 Circular Subject First Date Issued To No.
of Issue 78-09 Arcing of General Electric 6/8/78 All Power Reactor Company NEMA Size 2 Facilities with an Contactors OL or CP 78-10 Control of Sealed Sources 6/1.4/78 All Institutional Used in Radiation Therapy Medical Licensees 78-11 Recirulation M-G Set 6/15/78 All BWR Power Reactor Overspeed Stops Facilities with an OL or CP 78-12 HPCI Turbine Control 6/30/78 All Power Reactor Valve Lift Rod Facilities with an Bending OL or CP having a HPCI Terry Turbine 78-13 Inoperability of 7/10/78 All Power Reactor Multiple Service Facilities with an Water Pumps OL or CP 78-14 HPCI Turbine Re-7/17/78 All Power Reactor versing Chamber Facilities with an Hold Down Bolting OL or CP having a HPCI Terry Turbine excepting Duane Arnold and Monticello 78-15 Tilting Disk Check 7/24/78 All Power Reactor Valves Fail to Close Facilities with an with Gravity in Vertical OL or CP Position 78-16 Limitorque Valve 7/26/78 All Power Reactor Actuators Facilities with an OL or CP 78-17 Inadequate Guard 10/13/78 All Power Reactor Training / Qualification Facilities with an and Falsified Training OL; Susquehanna 1 & 2, Records Shoreham, and Salem 2
IE Circular No. 78-19 Date: December 29, 1978 Page 3 of 3 ENCLOSURE 2 (Continued)
LIST OF IE CIRCULARS ISSUED IN 1978 Circular Subject First Date Issued To No.
of Issue 78-18 UL Fire Test 11/6/78 All Power Reactor Facil' ties with an OL or CP
.