IE Circular No. 81-13, Torque Switch Electrical Bypass Circuit for Safeguard Service Valve Motors
SSINS No.: 6830
Accession No.:
8107230029
IEC 81-13
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
September 25, 1981
IE CIRCULAR NO. 81-13: TORQUE SWITCH ELECTRICAL BYPASS CIRCUIT FOR
SAFEGUARD SERVICE VALVE MOTORS
Background:
A common wiring discrepancy between the as-designed and as-installed valve
motor control circuitry caused, at least in part, a valve malfunction at two
operating boiling water reactors. In each case, an electrical bypass circuit
around the valve-open torque switch on a Limitorque valve operator was not
installed as designed. The intent of this bypass feature is to override the
valve-open or valve-close torque switch circuits to ensure that full motor
torque is applied to the valve until it is near full open or full closed.
This is to eliminate the chance of the valve stalling out under emergency
conditions before it has completed its travel.
Description of Circumstances:
Brunswick Unit 2 - During a test of the reactor core isolation cooling
(RCIC) system at this facility, in March 1978, the injection valve would not
open. The valve and valve motor were checked, cycled and tested; no problems
were identified. In September 1980, following a reactor scram, the same
valve failed to fully open. An inspection of the valve motor control
circuitry by the licensee revealed that the electrical bypass circuit wiring
around the valve-open torque switch was not installed as designed.
Examination of other RCIC system valves revealed that four of ten similar
torque switch bypass circuits had not been installed. The missing electrical
bypasses were installed.
Cooper Station - During a test of the residual heat removal (RHR) system at
this facility, in December 1980, one of the RHR loop injection line
isolation valves would not open. The problem was reported to be an incorrect
closing torque switch setting. However, it was noted and reported, as
unrelated to this event, that both Train A and Train B injection valve-open
torque switch bypass circuits had not been installed in the valve motor
control circuitry as designed. This discrepancy was corrected.
Recommended Action for Holders of Operating Licenses or Construction
Permits:
1. Verify that all valves important to safety, which are required by the
design to have torque switch bypass circuits installed, do in fact have
these circuits installed.
2. Verify that all applicable electrical drawings correctly reflect these
electrical bypass circuits.
.
IEC 81-13
September 25, 1981
Page 2 of 2
3. If inspection reveals that required bypass circuits are not installed,
installation should be initiated as soon as practicable after the need
has been determined.
4. Establish controls to assure that torque switch bypass circuits are not
inadvertently removed and that they are restored if they are removed
for maintenance or test.
No written response to this circular is required; however, if discrepancies
are found, a report may be required by applicable Technical Specifications
or other NRC reporting requirements. If you need additional information with
regard to this subject, please contact the Director of the appropriate NRC
Regional Office.
Attachment:
Recently issued IE Circulars
Page Last Reviewed/Updated Tuesday, March 09, 2021