United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 80-20: Failures of Westinghouse Type W-2 Spring Return to Neutral Control Switches

                                                       SSINS No.: 6820 
                                                       Accession No.: 
                                                       8006190023 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555
                                     
                                July 31, 1980

                                                      IE Bulletin No. 80-20 

FAILURES OF WESTINGHOUSE TYPE W-2 SPRING RETURN TO NEUTRAL CONTROL SWITCHES 

By letter dated June 18, 1980, Commonwealth Edison Company submitted 
Licensee Event Report No. LER 50-295/80-24 to the NRC describing a 
malfunction of a Westinghouse Type W-2 control switch at the Zion Generating 
Station, Unit 1. The malfunctioning switch is a three position spring return 
to neutral switch. Although the switch was in its proper neutral position 
when it malfunctioned, its neutral contacts failed to close properly thereby
preventing the automatic start of 1A Service Water Pump. 

Subsequent tests conducted on the malfunctioning switch revealed that 
contact closure was intermittent with the switch in the neutral (or "Auto 
Start") position. Other tests conducted on identical switches from spares 
and from Unit 2 equipment disclosed two additional switches with a tendency 
for intermittent contact closure. 

A review of this matter by Westinghouse led to the issuance of NSD Technical
Bulletin No. NSD-TB-80-9 to the utility owners of all Westinghouse operating
plants. The recommendations contained in the Westinghouse technical bulletin
include: (i) testing the neutral position contacts of the subject W-2 
switches for continuity, and (ii) rewiring of the indicating light circuit 
to permit the early detection of a neutral contact failure as shown in 
Figure 1. 

Depending on how the indicating light circuit is wired, loss of continuity 
thru the neutral position contact of a W-2 switch could remain undetected 
until the equipment associated with the switch were called upon to operate. 
Since such a failure would be equivalent to by-passing the system associated
with the switch, consideration should be given to rewiring the switches used
in safety-related applications as shown in Figure 1. Such rewiring would 
provide an acceptable means for detecting contact failure, provided the 
indicating light is in the control room and readily visible by the operator.
If the indicating light is not so located, consideration should be given to 
annunciating the neutral position contact failures at the control room to 
alert the operator of the inoperable status of a safety-related system. In 
addition, consideration should be given to adding redundant contacts to the 
W-2 switches or to replacing the W-2 switches with others having a more 
positive contact wiping action. 

ACTIONS TO BE TAKEN BY LICENSEES AND HOLDERS OF CONSTRUCTION PERMITS: 

1.   Determine whether Westinghouse Type W-2 control switches with spring 
     return to neutral position are used in safety-related applications at 
     your facility. If so, identify the safety-related systems using these 
.

IE Bulletin No. 80-20                                      July 31, 1980 
                                                           Page 2 of 2 

     switches and the total number of switches so used. If no such switches 
     are used in your facility, you should indicate that this is the case 
     and ignore the remaining questions. 

2.   Licensees of operating plants using Type W-2 spring return to neutral 
     control switches in safety-related applications shall perform 
     continuity tests on all such switches. These tests shall be performed 
     with the switch operator in the neutral position and completed within 
     ten (10) days of the date of this bulletin. In addition, this 
     continuity test shall be repeated at least every thirty-one (31) days 
     after the initial test and after each manipulation of the switch from 
     its neutral position. These continuity tests may be discontinued 
     subsequent to implementing the longer term corrective measures 
     described below. 

3.   Licensees of operating plants and holders of construction permits shall
     describe the longer term corrective measures planned and the date by 
     which such measures will be implemented by actual installation or by 
     design change, as appropriate. As a minimum, the longer term corrective
     measures should include rewiring the indicating light as shown in 
     Figure 1 provided the light is readily visible to the control room 
     operator. If not, failures of the neutral position contacts should be 
     annunciated in the control room. 

A report addressing the above matters, including the number of failures 
detected during the first series of tests and the safety-related systems 
involved, shall be submitted to the director of the appropriate NRC regional
office within forty-five (45) days of the date of this bulletin. A copy of 
the report shall be forwarded to the Director, Division of Reactor 
Operations Inspection, Office of Inspection and Enforcement, Nuclear 
Regulatory Commission, Washington, D. C. 20555. 

Approved by GAO, B180225 (ROO72); clearance expires 7/31/80. Approval was 
given under a blanket clearance specifically for identified generic 
problems. 

Enclosure: 
Figure 1 
Page Last Reviewed/Updated Tuesday, July 23, 2013