Part 21 Report - 2002-050

February 18, 2002
02-01NRC .DOC
MFN 02-008

Document Control Desk
United States Nuclear Regulatory Commission
Washington, DC 20555

Subject: Cutoff Switch Used With Model AK-15, AK-25 and AKR-30S Electrical and Electrical/Manual Operated Circuit Breaker

This letter provides information regarding a recently discovered deviation in the cutoff switch (Part Number 622C505G1) contact assembly used in electrical and electrical/manual operated model AK-15, AK-25 and AKR-30S low voltage power circuit breakers (LVPCB) manufactured by GE. The cutoff switch was manufactured by GE Industrial Systems in Plainville, CT and supplied to licensees by GE-NE as an original circuit breaker part or as a renewal part. Recently GE Nuclear Energy (GE-NE) discovered loose screws in the contact assembly of cutoff switches used in AK-15, AK-25 and AKR-305 LVPCBs. The loose screw was one of two fasteners that hold the normally closed (NC) contact assembly in place. The contact assembly serves as the electrical common node for the two stationary NC contacts and provides a restraining reaction surface for the switch lever operated movable contacts. It was determined that the inner threads of the contact assembly stud deviated from design requirements.

Since the specific applications and associated safety functions of the impacted LVPCBs are not known to GE-NE, we have transferred information pursuant to 10 CFR Part 21.21(b) to those licensees known to be affected. However, since additional licensees may have obtained these devices through other dedicating entities, we cannot assure ourselves that all end-users have been notified. We are therefore providing this information to the NRC for appropriate action.

The installation of a cutoff switch containing a contact assembly fastener with defective stud threads into an AK-15, AK-25, and AKR-30S LVPCB could result in (1) loose parts being introduced into the circuit breaker mechanism which could cause jamming of the breaker mechanism and may make the circuit breaker inoperable, or (2) the stationary contact assembly shorting to ground or common which could cause a loss of control power and may make the circuit breaker inoperable.

It is suggested that licensees perform the foHowing inspections: (Refer to Figure 1)

1. Inspect any GE manufactured cutoff switch assembly located in inventory as soon as possible for a loose fastener or defective stud thread condition by attempting to tighten the contact assembly fastener to a value of six to eight inch pounds. If unable to tighten to this value discard the cutoff switch assembly. There is no cutoff switch assembly repair or rework recommendation.

2. Inspect the cutoff switch assemblies installed in electrical and electrical/manual AK-15, AK-25 and AKR-30S circuit breakers at the next available opportunity.

a. Remove the circuit breaker escutcheon, to gain access to the cutoff switch.

b. Inspect the contact assembly fastener and insulating bushing.

If they are present but loose, remove the circuit breaker from service. The loose insulating bushing and fastener are the prime indication that the assembly stud threads are defective. If the contact assembly fastener and insulating bushing are missing; remove the circuit breaker from service, and remove and replace the cutoff switch assembly. There is no repair or rework recommendation.

If a contact assembly fastener is found loose, remove the cutoff switch assembly from the circuit breaker. Attempt to tighten the contact assembly fastener to a value of six to eight inch pounds. If unable to tighten to this value discard the cutoff switch and replace. There is no repair or rework recommendation.

3. During scheduled maintenance, inspect the cutoff switch assembly installed in electrical and electrical/manual AK-15, AK-25 and AKR-30S circuit breakers.

Assure that the contact assembly fastener can be tightened to a torque value of six to eight inch pounds. If unable to tighten to this value discard the cutoff switch and replace. There is no repair or rework recommendation.

If you have any questions, please call me at (408) 925-5362.

Sincerely,

Jason. S. Post, Manager
Engineering Quality and Safety Evaluations

cc: S.D. Alexander (NRC-NRR/DISPIPSIB)
G. C. Cwalina (NRC-NRRIDISPIPSIB)
J. F. Klapproth (GE-NE)
H. J. Neems (GE-NE)
PRC File

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