FVY-86-105, Part 21 Rept Re Design Defect Relating to Limitorque Motor Operators Mfg Prior to 1975.Mfg Contacted & Retrofit Kits Installed on safety-related & nonsafety-related Operators. Addl Info Encl

Part 21 Rept Re Design Defect Relating to Limitorque Motor Operators Mfg Prior to 1975.Mfg Contacted & Retrofit Kits Installed on safety-related & nonsafety-related Operators. Addl Info Encl

ML20215E438
Person / Time
Site:	Salem, Vermont Yankee, 05000000
Issue date:	11/10/1986
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20215E442	List: FVY-86-105, Part 21 Rept Re Design Defect Relating to Limitorque Motor Operators Mfg Prior to 1975.Mfg Contacted & Retrofit Kits Installed on safety-related & nonsafety-related Operators. Addl Info Encl ML20215E462
References
REF-PT21-86-392-000 FVY-86-105, PT21-86-392, PT21-86-392-000, NUDOCS 8612220300
Download: ML20215E438 (4)

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VERMONT YANKEE NUCLEAR POWER CORPORATION FVY 86-105 RD 5, Box 169, Ferry Road, Brattleboro, VT 05301 ,,,,,7,.

p ENGINEERING OFFICE 1671 WORCESTER ROAD

• FRAMINGHAM, MASSACHUSETTS 01701

• TELEPHONE 617-e72-8100 November 10, 1986 U.S. Nuclear Regulatory Commission Office of Inspection & Enforcement Region I 631 Park Avenue King of Prussia, PA 19406 Attn: Dr. Thomas E. Murley Regional Administrator

References:

a) License No. DPR-28 (Docket No. 50-271)

Subject:

Notification of Potential Existence of a Design Defect in Accordance with 10 CFR 21.21 In accordance with the provisions of 10 CFR 21, Section 21, we are hereby notifying you that we have obtained information indicating that a design defect may exist with respect to Limitorque Motor Operators manufactured prior to 1975.

Enclosure I to this letter documents the details of this evaluation.

Should you have any questions regarding this matter, please contact me.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION

$4<*--- WM Warren P. Murphy Vice President and Manager of Operations

/dm 8612220300 DR 861110 g ADOCK 05000271 PDR . / \g

ENCLOSURE I COMPANY INFORMING Vermont Yankee Nuclear Power Corporation THE COMMISSION RD 5, Box 160 Ferry Road Brattleboro, Vermont 05301 FACILITY Vermont Yankee Nuclear Power Corporation PO Box 157 Governor Hunt Road Vernon, Vermont 05354 COMPONENT Limitorque Operator Spring Packs FIRM SUPPLYING Limitorque Corporation COMPONENTS Lynchburg, Virginia NATURE OF DEFECT During the 1985-86 outage, as part of Vermont Yankee's ongoing MOV Reliability Program, extensive inspections and overhauls were performed on approximately 40 motor operators. These operators were rebuilt utilizing the most current technical manuals and with the assistance of a Limitorque Field Engineer. During the rebuilding, the actuators were repacked with new less viscous NEBULA-EP-0 grease which is recommended for use in nuclear containments by Limitorque Technical Manuals.

On June 4, 1986, Vermont Yankee experienced a motor burnout on MOV 2-438.

The conditions surrounding this event were reported to the Commission in LER 86-12, Rev. 1, dated August 22, 1986. As a result of this burnout, Vermont Yankee and Limitorque performed an investigation which concluded that, due to the unique orientation, the new less viscous EP-0 grease had leaked from the operator housing into the spring pack area creating a hydraulic lock condition, subsequently restricting the torque switch operation and, therefore, burning up the electric motor. This is the first motor burnout of this type identified by Vermont Yankee.

DATE OF INCIDENT The motor burnout of MOV 2-438 occurred on June 4, 1986. The Potential Part 21 Report Evaluation was initiated on June 25, 1986.

NUMBER OF COMPONENTS Vermont Yankee has approximately 80 safety-related valves in service.

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Enclosure I Page 2 CORRECTIVE ACTION After the initial discovery of the failed operator, the manufacturer was contacted. Limitorque indicated that this problem had been identified some years ago and they had developed a retrofit kit to correct the problem. No evidence could be found by either Vermont Yankee or Limitorque documenting that this information was ever disseminated to the industry. Limitorque has also been unable to reproduce this type of failure in their own test facilities, however does acknowledge the potential of it to happen.

The retrofit kits were installed on all 32 safety-related and 8 non safety-related operators which had the new less viscous EP-0 grease installed during the 1985-86 outage. This included all' operators in the drywell (11) and all opera-tors in the steam tunnel (7). The kits are designed to allow a flow path to prevent trapping grease in the spring pack and therefore eliminate the possibi-lity of a hydraulic lockup.

Vermont Yankee will take the required actions to ensure that the hydraulic lockup kit modifications will be installed on all remaining safety-related motor operators prior to the installation of any new grease and no later than the end of the 1987 refuel outage.

RELATED ADVICE Our evaluation has determined that a significant safety hazard does not exist at Vermont Yankee since we have taken appropriate corrective actions on all valves which utilize the less viscous EP-0 grease. However, Limitorque appears not to have given notification to other utilities of the possible need to retrofit pre-1975 valves, even though they have made an internal modification in their newer valves to eliminate the grease lock condition. Therefore, this Part 21 is being submitted to forewarn other plants of this potential problem.

It is recommended that utilities review this information for applicability to their locations.

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