NextEra Energy Duane Arnold (NextEra Energy) makes the following notification under
10 CFR 21.21(d)(3)(i) of a failure to comply found during surveillance testing. The specific issue is insufficient clearance between the spring and the inside of the cylinder of the actuator for a Miller series A63B2N air cylinder actuator for a control valve (CV-1956A, Control Building Chiller Discharge to Emergency
Service Water Isolation). The resulting improper clearance caused an increase in running load, which caused the valve to become stuck in the closed position. The valve failure was discovered on May 10, 2009. The control valve actuator was supplied by
Flowserve US, Inc, as a
basic component in April, 2008 for use at the Duane Arnold Energy Center.
Flowserve has indicated that the actuator was procured as a
commercial grade item and dedicated for safety related installation under their
QA program. The valve and actuator were installed on April 17, 2009.
The lack of spring to actuator clearance resulted in a loss of capability of CV-1956A to perform its intended safety function of providing a safety related seismic discharge path for cooling water from the safety related Control Building Chiller, 1V-CH-1A. The Chiller was declared inoperable as a result of this failure to comply and, on July 1, 2009 was determined to have resulted in a substantial safety hazard.
The actuator for CV-1956A was rebuilt with a replacement spring having proper dimensional clearance and higher opening force capability. The actuator has been installed by a plant modification and the control building chiller has been returned to an operable status.
The air operated valve assembly supplier, Flowserve US Inc, was contacted on July 1, 2009 to discuss NextEra Energy's findings.
NextEra Energy has verified that no other safety related actuators with the incorrect valve actuator cylinder to spring clearances have been installed at the Duane Arnold Energy Center.
The NRC Resident Inspector has been notified.