Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6835
IN 84-04
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
January 18, 1984
Information Notice No. 84-04: FAILURE OF ELASTOMER SEATED BUTTERFLY VALVES
USED ONLY DURING COLD SHUTDOWNS
Addressees:
All nuclear power reactor facilities holding an operating license (OL)
or construction permit (CP).
Purpose:
This information notice is provided as a notification of recently observed
failure of redundant elastomer seated butterfly valves used only during cold
shutdowns. No specific action 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 April 19 and August 26, 1983, the Sacramento Municipal Utility District
reported (LER 83-14) that the two reactor building purge inlet valves and
the two reactor building purge outlet valves failed their local leak rate
tests at the Rancho Seco Nuclear Generating Station. The leakage value for
the purge inlet valves was greater than the surveillance acceptance
criteria for total local leak rate. The purge outlet valves were unable to
hold pressure sufficient to test. All four valves were Allis Chalmers Model
60WR butterfly valves.
The purge inlet and outlet valves located inside containment have Limitorque
Model SMB-3 motor operators. The purge inlet and outlet valves located
outside containment have air operators of Allis Chalmers design.
Investigation by the utility's engineers revealed a series of problems
that contributed to the leakage.
1. The purge inlet valve located outside containment required adjustment
of the elastomer seat.
2. The purge inlet valve located inside containment had damage to the
elastomer seat and was found to be past the normally fully closed
position by approximately one inch.
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January 18, 1984
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3. The purge outlet valve located inside containment had a damaged elastomer
seat.
4. The purge outlet valve located outside containment required adjustment of
the elastomer seat and was found to be not fully closed by approximately
one inch.
Further investigation by the utility's engineers and vendor representatives
indicated that the purge inlet valve located inside containment went past the
fully closed position because of problems with its motor operator brakes.
Since the valve, itself, did not have any stops, the valve disk could drift
past its fully closed position. The motor operator brakes were replaced and
the valve was cycled to verify proper operation.
This investigation also indicated that the reason the purge outlet valve
located outside containment did not go to the fully closed position was a lack
of lubrication of the mechanical linkage of the valve operator. This lack of
lubrication made the linkage act to retard the closure of the valve thus
preventing full closure. The linkage was lubricated and the air cylinder was
cleaned and lubricated. The valve was exercised to confirm proper operation.
In addition to the above actions, the valve seats were replaced and adjusted,
as required.
Although not indicated in the LER, a contributing factor quite likely was the
fact that these valves are only opened during cold shutdowns. During normal
plant operations, they are closed and rendered inoperable. Thus, in order to
provide adequate assurance of proper purge isolation and to provide information
for the utility's engineers to evaluate the performance of the valves, the
licensee has implemented programs to:
1. Ensure proper lubrication of the valves through a new preventative
maintenance program.
2. Perform a local leak rate test of the purge inlet and outlet valves before
bringing the unit out of cold shutdown conditions in preparation for
normal operations.
3. Perform a local leak rate test before the initial purge during each cold
shutdown.. IN 84-04
January 18, 1984
Page 3 of 3
No written response to this notice is required. If you have any questions
regarding this matter, please contact 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
