ML20009E222
| ML20009E222 | |
| Person / Time | |
|---|---|
| Site: | Monticello, Dresden, Davis Besse, Palisades, Perry, Fermi, Kewaunee, Point Beach, Byron, Braidwood, Prairie Island, Callaway, Duane Arnold, Clinton, Cook, Quad Cities, La Crosse, Big Rock Point, Zion, Midland, LaSalle, Zimmer, Bailly, Marble Hill  |
| Issue date: | 07/24/1981 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 8107270253 | |
| Download: ML20009E222 (1) | |
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American Electric Power Service Corporation gj g D. C. Cook 1, 2 (50-315, 50-316)
Cincinnati Gas and Electric Company Zimmer (50-358)
The Cleveland Electric Illuminating Company Perry 1, 2 (50-440, 50-441)
Commonwealth Edison Company Braidwood I, 2 (50-456, 50-457)
Byron 1, 2 (50-454, 50-455)
Dresden 1, 2, 3 (50-10, 50-237, 50-249) '
La Salle 1, 2 (50-373, 50-374)
Quad-Cities 1, 2 (50-254, 50-265)
Zion 1, 2 (50-295, 50-304)
Consumers Power Company Big Rock Point (50-155)
Palisades (50-255)
Midland 1, 2 (50-329, 50-330)
Dairyland Power Corporation LACBWR (50-409)
The Detroit Edison Company Fermi 2 (50-341)
Illinois Power Company Clinton 1, 2 (50-461, 50-462) s Rf s p
'/4 Iowa Electric Light and Power Company Duane Arnold (50-331)
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$ @ v-Northern Indiana Public Service Company Bailly (50-367)
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Northern States Power Company q
Monticello (50-263)
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Public Service of Indiana Marble Hill 1, 2 (50-546, 50-547)
Toledo Edison Company Davis-Besse 1 (50-346) g h9\\
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Union Electric Company N
i Callaway 1, 2 (40-483,50-48o)
.y Wisconsin Electric Power Company Point Beach 1, 2 (50-260, 50-301) g Wisconsin Public Service Corporation Kenaunee (50-305)
Illinois Department of Nuclear Safety 810727025385072I Y
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SSINS No.:
6830 Accession No.:
8103300406 IEC 81-12 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 July 22, 1981 IE Circul3r No. 81-12:
INADEQUATE PERIODIC TEST PROCEDURE OF PWR PROTECTION SYSTEM Description of Circumstances:
On November 30, 1980, ground isolation procedures were being carried out to locate an electrical ground in the 125V dc bus No.1 at the St. Lucie Nuclear Power Plant.
Part of the procedure requires deenergizing the de control power to the reactor trip circuit breakers (TCBs).
These breakers are designed to trip (fail-safe mode) on undervoltage upon loss of de control power.
Referring to Figure 1, the four TCBs (TCB 1,3,5, and 7) that are supplied control power from dc bus No. I did not trip immediately (because of binding) on undervoltage when control power was deenergized. The operators did verify that the shunt.
trip for each of the four TCBs was functioning.
Operators also verified that the redundant TCBs from dc bus No. 2 (TCB 2,4,6, and 8) tripped on similar undervoltage conditions, and, in fact, inadvertently caused a plant trip while testing.
Investigation into the problem by the licensee identified the cause of failure as an out-of-adjustment condition in the linkage mechanism of the undervoltage trip device.
This adjustment problem, together with the lack at cleaning and periodic relubricating of the trip shaft muhanism, is the subject of IE Bulletin 79-09 which was issued April 17, 1979.
While shutdown, the undervoltage trip mechanism on each of the above four faulty TCBs was adjusted and verified to operate satisfactorily.
Investigation by the licen u e revealed that the reactor protection system (RPS) periodic test procedure in use at the time did not verify the trip function of the undervoltage trip coil independent of the shunt trip coil.
Referring to Figure 1, it can be seen that during a reactor trip test at this facility, these coils operate simultaneously causing the trip opening of the associated TCBs.
This arrangement of the RPS and the trip test procedure may be similar for other PWRs.
BWRs may use similar circuit breakers in safety systems; therefore, similar indequaci n in their circuit breaker test procedures may exist.
Following adjustment of the linkage mechanism of the undervoltage trip device the licensee instituted a revised surveillance test procedure to check the under-voltage and shunt trip devi:.s independently and to insure proper breaker operation. Although not 2nown in Figure 1, the undarvoltage trip coil and the shunt trip coil are separately fused so that test procedure changes resolved the problem at St. Lucie.
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IEC 81-12 July 22,1981 Page 2 of 2 Recommended Action for Holders of Operating Licenses and Construction Permits:
It is recommended that holders of operating licenses and construction permits review for applicability the specific items presented in the " Description of Circumstances." It is further recommended that the procedure for surveillance testing of trip circuit breakers be reviewed and revised as necessary to provide independent testing of each trip function, including position verification to ensure that the breaker actually trips.
If the trip circuit breakers do not have provisions for independent testing of each trip function, including position verification, then appropriate modifi-i cations should be made to include such features (e.g., local pushbuttons for the shunt and undervoltage trip coils, separately fused circuits for the shunt and undervoltage trip coils, etc).
No written response to this circular is required.
If you need additional information with regard to this subject, please contact the director of the appropriate NRC Regional Office.
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IEC 81-12 July 22, 1981 RECENTLY. !ED IE CIRCbtARS Circular Date of No. Subject Issue Issued to 81-10 Steam Voiding in the Reactor 7/2/81 All power reactor Coolant System During Decay facilities with an Heat Removal Cooldown OL and CP 81-09 Containment Effluent Water-7/10/81 All power reactor That Bypasses Radioactivity facilities with an Monitor OL or CP 81-08 Foundation Materials 5/29/81 All power reactor facilities with an OL or CP 81-07 Control of Radioactively 5/14/81 All power reactor Contaminated Material facilities with an OL or CP 81-06 Potential Deficiency Affecting 4/14/81 All power reactor Certain Foxboro 20 to 59 facilities with an Milliampere Transmitters OL or CP 81-05 Self-Aligning Rod End Bushings 3/31/81 All power reactor for Pipe Supports facilities with an OL or CP 81-04 The Role of Shift Technical 4/30/81 All power reactor Advisors and Importan e of facilities with an Reporting Operationai Events OL or near-term OL 81-03 Inoperable Seismic Monitoring 3/2/81 All power reactor Instrumentation facilities with an OL or CP 81-02 Performance of NRC-Licensed 2/9/81 All oower reactor Individuals While on Duty facilities (research & test) with an OL or CP OL = Operating Licenses CP = Construction Permit /}}