05000293/LER-1988-001, :on 880106,automatic Isolations of Portions of Primary Containment & Reactor Bldg Isolation Control Sys Occurred.Caused by Failure in Logic Relay 16A-K57.Coil in Relay Replaced & Other Relay Coils Analyzed

:on 880106,automatic Isolations of Portions of Primary Containment & Reactor Bldg Isolation Control Sys Occurred.Caused by Failure in Logic Relay 16A-K57.Coil in Relay Replaced & Other Relay Coils Analyzed

ML20196C065
Person / Time
Site:	Pilgrim
Issue date:	02/05/1988
From:	Bird R, Ellis D BOSTON EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
BECO-88-019, BECO-88-19, LER-88-001, LER-88-1, NUDOCS 8802120231
Download: ML20196C065 (5)

LER-1988-001, on 880106,automatic Isolations of Portions of Primary Containment & Reactor Bldg Isolation Control Sys Occurred.Caused by Failure in Logic Relay 16A-K57.Coil in Relay Replaced & Other Relay Coils Analyzed

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
2931988001R00 - NRC Website

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On January 6,1988 at 1450 hours0.0168 days <br />0.403 hours <br />0.0024 weeks <br />5.51725e-4 months <br />, automatic actuations of portions of the Primary Containment Isolation Control System (PCIS) and Reactor Building Isolation Control System (RBIS) occurred.

The actuations resulted in the following automatic responses.

The Train "B" Primary Containment System (PCS) Group 2 isolation valves received an isolation signal.

The outboard (Train "B") ventilation system dampers of the Secondary Containment System (SCS) closed.

The "B" Train of the SCS/ Standby Gas Treatment System (SGTS) started.

Following immediate investigation the SGTS was secured, the ventilation dampers were opened, and the isolation reset on January 7, 1988 at 0200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br />.

The cause for the actuations was the failure of the coil in a logic relay that is part of the outboard PCIS/RBIS logic circuitry. The relay coil was replaced.

Based on analysis, additional relays (or relay coils) have been selected for replacement prior to startup.

The actuations occurred during an extended outage while in the cold shutdown condition with negligible core decay heat and with the mode switch in the SHUTDOWN position. No control rods were in the withdrawn position at the time of the actuations. The actuations posed no threat to the public health and safety.

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EVENT DESCRIPTION

On January 6, 1988 at 1450 hours0.0168 days <br />0.403 hours <br />0.0024 weeks <br />5.51725e-4 months <br />, automatic actuations of portions of the Primary Containment Isolation Control System (PCIS) and Reactor Building Isolation Control System (RBIS) occurred.

The actuations resulted in the following automatic responses.

The Train "B" Primary Containment System (PCS) Group 2 isolation valves received an isolation signal.

The outboard (Train "B") ventilation system dampers of the Secondary Containment System (SCS) closed.

The "B" train of the SCS/ Standby Gas Treatment System (SGTS) started.

Failure and Halfunction Report 88-6 was written to document the actuations, Notification was made to the NRC Operations Center on January 6, 1988 at 1712 hours0.0198 days <br />0.476 hours <br />0.00283 weeks <br />6.51416e-4 months <br />. Following immediate investigation, the SGTS was secured and the ventilation dampers were reopened, and the isolation reset on January 7, 1988 at 0200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br />. A priority Maintenance Request (MR 88-9) was also issued to investigate.

The actuations occurred during an extended outage while in the cold shutdown condition with negligible core decay heat and with the mode selector switch in the SHUTDOHN position. The reactor vessel head was installed and no control rods were in the withdrawn position at the time of the actuations.

CAUSI The cause for the actuations was the failure of the coil in logic relay 16A-K57.

The failure of the coil resulted in excessive current and caused the 120VAC circuit's fuse (16A-F22) to blow thereby de-energizing the circuit.

The probable cause for this and other failed (burned) coils in CR120A relays has been attributed to the end of useful life; reference Memorandum TCH87-464, "CR120A Relay Evaluation". The failure mode appears to be mechanical stressing of the coil terminal connection resulting in physical separation, overheating and burning of the connection internal to the coil encapsulation.

1 Relay 16A-K57 is located in logic Panel C-942.

The relay (type CR120A) is manufactured by General Electric.

Inboard and outboard logic relays (of the PCIS and RBIS) are located in PCIS/RBIS logic panels C-941 and C-942, respectively.

The CR120A logic relays located in these panels are mounted in a closely packed array and are continuously energized.

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CORRECTIVE ACTION

A new coil was installed in relay 16A-K57 via MR 88-9 (MSC 88-9-1).

Post work testing was performed using procedure number 8.H.2-1.5.2, "Hain Steam Line Isolation Valve Logic-Test B-Outboard".

A discrepancy unrelated to the cause for the actuations was identified at Step 31 of the procedure.

The step is performed to verify that the "Outboard Main Steam Isolation Valve Logic Test" light is 0FF; the light was ON.

Investigation revealed that contacts M1 and Tl of relay 16A-K16X were not separated as expected for this part of the test.

Examination of the relay revealed that the pivot points of the contacts (M1 and il) were bound.

The binding appeared to be caused by a misalignment of the plastic parts that house the relay reeds.

Relay 16A-K16X is an Agastat Model GPIC 750 relay. A review of database (SEEK) records and interviews with Instrumentation and Control Supervisors revealed no known previous failures for this type of relay at Pilgrim Station.

Relay 16A-K16X was replaced via MSC 88-9-2.

F.ollowing the replacement, post work testing was completed satisfactorily.

Previous failures of CR120A relays led to the evaluation documented in Memorandum TCH 87-464.

The evaluation resulted in the issuance of an Engineering Service Request (ESR 87-643).

The E$R requested Nuclear Engineering Department evaluation for reporting CR120A relay failures pursuant to 10CFR Part 21. The evaluation performed concluded that reporting (10CFR Part 21) was not applicable because the relays were installed in accordance with the technical requirements included in the procurement design documents and because the relays operated properly for approximately 10 years prior to the first failure.

The ESR also requested implementation of recommendations (TCH 87-464) to improve the reliability of CR120A relays.

The technical evaluation documented in TCH 87-464 reviewed CR120A relays installed at Pilgrim Station. The review included the specific application of each individual relay, the overall operating history of these relays as compared to industry information and a failure effects analysis of the safety related relays.

Based on this technical evaluation, specific relays (or relay coils) have been selected for replacement prior to startup.

The recommendations regarding the remaining items are being evaluated for incorpcration into the long term maintenance program.

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This event was determined to be reportable pursuant to 10CFR50.73(a)(2)(iv) because (false) PCIS/RBIS signals actuated accident mitigating systems (SCS,5GTS and PCS).

SIMILARITY OF PREVIOUS EVENTS A review of Pilgrim Station Licensee Event Reports (LER's) written since January 1984 was conducted.

The review focused on LCR's submitted pursuant to 10CFR50.73 (a)(2)(iv) that were caused by a failed coil in CR120A relay.

The review revealed a previous failure reported in LER 50-293/87-018-00.

The failure of the coil in relay 16A-K55 resulted in the automatic closure of the outboard PCS/ Group 6 (Reactor Water Cleanup System) isolation valves.

ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) CODES The EIIS codes for the actuations are as follows:

CO@0NENTS CODES Coil CL 04 Relay, tripping (16A-K57)

SYSTEMS Containment Isolation Control System (PCIS/RBIS)

JH Engineered Safety Features Actuation System (PCIS/RBIS) JE Primary Containment System (PCS)

JH Reactor Building (SCS)

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10CFR50.73 Pilgrim Nuclear Ptmer Station Rocky HalRoad Plymouth, Massachusetts o236o February 5, 1988 -

Ralph G. Sini 8ECo Ltr. #88-19 Serwor Vice President - Nuclear U.S. Nuclear Regulatory Commission Attn: Document Control Desk Hashington, D.C. 20555 Docket No. 50-293 License No. DPR-35

Dear Sir:

The attached Licensee Event Report (LER) 88-001-00 "Automatic Actuations of Portions of Primary containment, Secondary Containment and Standby Gas Treatment Systems" is submitted in accordance with 10CFR Part 50.73.

Please do not hesitate to contact me if you have any questions.regarding this subject.

A.G.(Bird DHE/b1

Enclosure:

LER 88-001-00 cc: Mr. Hilliam Russell Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Rd.

King of Prussia, PA 19406 Sr. Resident Inspector - Pilgrim Station Standard BECo LER Distribution

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