United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-10: Motor-Operated Valve Torque Switches Set Below the Manufacturer's Recommended Value

                                                           SSINS No.:  6835 
                                                                   IN 84-10 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D.C. 20555  
                                     
                             February 21, 1984 

Information Notice No. 84-10:   MOTOR-OPERATED VALVE TORQUE SWITCHES SET 
                                   BELOW THE MANUFACTURER'S RECOMMENDED 
VALUE 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 

Purpose: 

This information notice is provided as a notification of motor operated 
valve torque switches being set below the manufacturer's recommended values. 
No specification is required in response to this information notice, but it 
is expected that recipients will review the information presented for 
applicability to their facilities. 

Description of Circumstances:  

On January 5, 1984, the GPU Nuclear Corporation reported (LER 83-024) that a 
review of records had revealed that a number of motor-operated valve torque 
switches were set below the manufacturer's recommended values at the Oyster 
Creek Nuclear Generating Station. Further investigation, by the utility, 
revealed that the torque switch setpoints set during preoperational testing 
were lower than the manufacturer's recommended values. In some cases, these 
setpoints were later changed to values even lower than those used during 
preoperational testing. 

GPU was prompted to review the records by attendance of GPU representatives 
at a recent INPO-sponsored "Valve and Valve Motor Operator Workshop" and 
after reviewing of INPO Significant Operating Event Report No. 83-09, "Valve
Inoperability Caused by Motor Operator Failures" and INPO Report No. 83-037,
"Assessment of Motor Operated Valve Failures." 

GPU attributes the apparent cause of the erroneous torque switch setpoints 
to a lack of sufficient knowledge about setpoint design basis and how the 
setpoints affect safety system functioning. It should be noted that during 
the review, the utility discovered that no formal setpoint requirement or 
documentation identifying the importance of torque switch settings existed. 




8401190062  
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                                                        IN 84-10           
                                                        February 21, 1984  
                                                        Page 2 of 3        

Preoperational testing and subsequent surveillance/maintenance testing was 
apparently conducted under low differential pressure conditions. As a 
result, the utility believes the torque switch settings were reduced to 
prevent applying a force that would cause the valve to jam in the closed 
position and possibly damage the motor operator or valve during periodic 
surveillance. Because differential pressure is a contributor in determining 
the amount of force necessary for full closure, the potential exists that 
some of the valves may not fully close or open under design-basis accident 
conditions. 

The actual design basis will vary with each valve operator in different 
systems, and these bases are presently under investigation by GPU with 
General Electric (the nuclear steam system supplier), the various valve 
manufacturers, and the,valve operator manufacturer (Limitorque). At this 
time, because various unspecified conservatism exist in establishing base 
line setpoints, the utility has not been able to determine that any valve 
would not have operated during accident conditions with setpoints lower than
originally specified. 

GPU's immediate corrective action was to investigate the historical data on 
isolation valves based on the Limitorque bill of material, preoperational 
test data, and surveillance/maintenance records. 

In addition, the following corrective actions on isolation and 
safety-related valves will be initiated: 

1.   The actual design basis investigation will be completed. 

2.   The appropriate torque switch setpoints will be determined. 

3.   The torque switch setpoints will be reset on all applicable valves. 

4.   Administrative controls will be issued to eliminate recurrence of this 
     incident. 

NRC has previously identified problems with torque and limit switch 
setpoints in Bulletin No. 72-3, "Limitorque Valve Operator Failures"; 
Circular No. 77-01, "Malfunctions of Limitorque Valve Operators"; Circular 
No. 81-13, "Torque Switch Electrical Bypass Circuit for Safeguard Service 
Valve Motors"; and Information Notice No. 82-10, "Following Up Symptomatic 
Repairs To Assure Resolution of the Problem." In addition, NRC is currently 
investigating the need for changing the inservice testing and inspection 
programs to ensure that safety-related valves have the torque and limit 
switch settings that will ensure proper operation of the valves during 
postaccident conditions. 
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                                                        IN 84-10           
                                                        February 21, 1984  
                                                        Page 3 of 3        

No written response to this information notice is required. If you have any 
questions regarding this matter, please contact the Regional Administrator 
of the appropriate NRC Regional Office, or this office. 



                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  R. J. Kiessel, IE 
                    (301) 492-8119 

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