05000298/LER-1985-011, Identifies Defect in Certain DC Motor Starters Used for Controlling ECCS & Primary Containment Isolation Valves, Initially Reported in 851119 LER 85-011.Certain Starters Missing Spacers,Causing Cracking of Disconnect Switch

Identifies Defect in Certain DC Motor Starters Used for Controlling ECCS & Primary Containment Isolation Valves, Initially Reported in 851119 LER 85-011.Certain Starters Missing Spacers,Causing Cracking of Disconnect Switch

ML20136E274
Person / Time
Site:	Cooper
Issue date:	12/26/1985
From:	Pilant J NEBRASKA PUBLIC POWER DISTRICT
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
NUDOCS 8601060484
Download: ML20136E274 (2)

LER-2085-011, Identifies Defect in Certain DC Motor Starters Used for Controlling ECCS & Primary Containment Isolation Valves, Initially Reported in 851119 LER 85-011.Certain Starters Missing Spacers,Causing Cracking of Disconnect Switch

Event date:
Report date:
2982085011R00 - NRC Website

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uj - df Mr. Robert D. Martin Regional Administrator j 1-f DEC 3 01985 I dl i

U.S. Nuclear' Regulatory Commission Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Subject:

Cooper Nuclear Station - DC Motor Starters Failure Nuclear Regulatory Commission Docket No. 50-298, DPR-46

Reference:

1) LER 85-011 "High Pressure Coolant Injection System Inoperability" dated November 19, 1985 This letter is written to advise that Nebraska Public Power District has identified a defect in certain DC motor starters used for controlling ECCS and primary containment isolation valves. The starters were designed by, and supplied to, NPPD by Nutherm International, Inc., Mt. Vernon, Illinois. The initial observation of this defect was reported in Reference 1.

In the manufacturing of the starters, the 60 amp disconnect switches (General Electric Model Number THC32S) were modified to permit the use of ring-tongue wire terminals. This modification removed the existing compression fitting and installed a spacer

in place of the extension with the compression fitting. These spacers were missing from some of the starters suppliad to Cooper i

Nuclear Station and led to cracking of the phenolic base of the disconnect switch. This cracking could permit the shorting of the power leads which.could cause loss of power to the s ta r te r and render the valve actuator inoperable.

The problem was discovered during the replacement of blown fuses j in one starter. After discovery of the problem, all installed starters manufactured by Nutherm were inspected. A Nutherm representative was present to assist in the inspection and repair of the remaining starters.

Of the 28 starters supplied by Nutherm, nine had the THC32S disconnect switches. Three of these starters had the required spacers properly installed, and one had previously been replaced.

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of the remaining five, two switches were cracked and had to be replaced. The remaining three had no indication of cracking and only required that the spacers be. installed.

Due to design differences, the disconnect switches in the remaining starters were not subject to this cracking problem; however,. they were also inspected with no further problems found.

All the installed starters have been inspected and necessary repairs made; therefore, NPPD considers this issue resolved.

If the staff is of the opinion that Reference 1 should be supplemented tc; contain the above additional information, please contact my office.

S ince rely, Jay M. Pilant Manager, Technical Staff Nuclear Power Group ll JMP/ DAW: cts-lg cc: Director, USNRC Office of Inspection ind Enforcement (3 copies)

Leonard F. Hinson (Nutherm International)

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