05000388/LER-2016-006
| Susquehanna Steam Electric Station Unit 2 105000388 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| Initial Reporting | |
| ENS 52255 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| 3882016006R00 - NRC Website | |
Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
Susquehanna Steam Electric Station 05000-388 NUMBER NO.
CONDITIONS PRIOR TO EVENT
Unit 1 — Mode 1, approximately 100 percent Rated Thermal Power Unit 2 — Mode 1, approximately 100 percent Rated Thermal Power
EVENT DESCRIPTION
On September 22, 2016 at 03:20, a Nuclear Plant Operator (NPO) reported that Reactor Building Zone II differential pressure (dP) was steady at 0.15 inches water gauge (WG) resulting in entry into Technical Specification 3.6.4.1. Operations determined that the flow control damper (PDD27522A) [EllS System/Component Identifier: VA/DMP] for the "A" Zone II equipment exhaust fan (2V206A) [EIIS System/Component Identifier: VA/FAN] was sticking, resulting in Zone II dP not being properly controlled.
The linkage for the damper was agitated and the damper moved to control dP as designed. Operations placed the "B" division fan (2V206B) in service. Following the fan swap, dP held steady at 0.31 inches WG with 2V206B in service and 2V206A in standby. Technical Specification 3.6.4.1 was cleared at 03:42.
During troubleshooting for this event, the linkage was disassembled and the damper was manually stroked with the linkage arm. The damper stroked smoothly with no binding. Internal inspection identified no issues. The pivot point for the linkage arm was disassembled and replaced. When the pivot point was disassembled, Maintenance discovered that the brass bushing and pins were worn and the grease was hardened and sticky.
This event was reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented fulfillment of a safety function (EN 52255). The condition also requires a Licensee Event Report (LER) in accordance with 10 CFR 50.73(a)(2)(v)(C).
CAUSE OF EVENT
The cause of the event was age related degradation of the brass bushing and grease hardening.
ANALYSIS/SAFETY SIGNIFICANCE
An engineering evaluation was performed and concluded that secondary containment could have performed its safety function of isolating as assumed in the accident analysis and also of re-establishing 0.25 inches vacuum (drawdown) within the assumed accident analysis time (10 minutes). Therefore, the subject event did not cause a loss of safety function. This event will not be counted as a safety system functional failure (SSFF) for the NRC performance indicator based on the engineering analysis that shows there was no loss of ability to fulfill the safety function.
Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
Susquehanna Steam Electric Station 05000-388 NUMBER NO.
CORRECTIVE ACTIONS
Key corrective actions include the following:
1. Work orders were written to disassemble, inspect, and replace the brass bushings for the remaining similar dampers (PDD27522B, PDD17522A/B, PDD17512A/B, and PDD27512A/B).
2. A PM strategy will be evaluated following completion of the inspections of the remaining similar dampers. Industry benchmarking revealed that no other stations perform PMs on these damper linkage arms, and the failure history at Susquehanna is small / minimal.
COMPONENT FAILURE INFORMATION
Information on the failed bushing is as follows:
Manufacturer: Contromatics Model #: 375SR
PREVIOUS SIMILAR EVENTS
Pressure as a Result of Solenoid Failure," dated May 26, 2016 0.25 in wg," dated May 6, 2016 Valve Failure," dated August 5, 2016 of Secondary Containment," dated July 6, 2016 Specification Surveillance Requirement 3.6.4.1.1," dated June 10, 2015