05000388/LER-2009-001
| Susquehanna Steam Electric Station Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 3882009001R00 - NRC Website | |
EVENT DESCRIPTION
While in Mode 5, Refueling, three (3) Main Steam Safety Relief Valves (SRVs) failed to meet the setpoint criteria of +/- 3% set forth in Technical Specification 3.4.3. All three SRVs actuated at a setpoint less than the -3% criteria.
The following are the test results:
Valve serial #�Setpoint�As Found�Deviation N63790-00-0085 1175 1123 -4.42% N63790-00-0020 1205 1165 -3.32% N63790-00-0019 1195 1155 -3.35% Originally, this event was determined not to be reportable as an Operation or Condition Prohibited by Technical Specifications {10 CFR 50.73(a)(2)(i)(B)} since the minimum number of SRVs required by the Technical Specifications remained operable. In addition, the failure was determined not to be reportable as a Common-Cause Inoperability of Independent Trains or Channels {10 CFR 50.73(a)(2)(vii)} since the guidance provided in Revision 2 to NUREG-1022 did not discuss setpoint drift as a common cause failure. After review of NRC Information Notice 2006-24, "Recent Operating Experience Associated with Pressurizer and Main Steam Safety/Relief Valve Lift Setpoints," these SRV failures were determined to be reportable under 10 CFR 50.73(a)(2)(vii).
The SRVs remained functional and the Technical Specification required number of SRVs (12) remained operable. There were no actual adverse consequences to the fuel, any plant equipment, or to the health and safety of the public as a result of this event.
A review of the previous 3 years of SRV testing revealed the following:
Year Valve serial # Setpoint As Found Deviation 2008 N63790-00-0025 1205 1137 -5.64% N63790-00-0082 1205 1159 -3.82% 2007 N63790-00-0130 1205 1145 -4.98% 2006 N63790-00-0081 1195 1154 -3.43% Based on the above testing results, the failure of 2 SRVs in 2008 is also reportable under 10 CFR 50.73(a)(2)(vii) because of multiple failures.
CAUSE OF THE EVENT
The cause of the event was determined to be setpoint drift.
ANALYSIS/SAFETY SIGNIFICANCE
This event was determined to be reportable under 10 CFR 50.73(a)(2)(vii) in that three (3) SRVs failed their setpoint criteria due to setpoint drift. The SRVs would have relieved pressure at a pressure lower than the setpoint and the Technical Specification required number (12) of SRVs was operable. As a result, there was no safety significance for this event.
CORRECTIVE ACTIONS
The following corrective action has been completed:
The following corrective action is planned:
- Revise reportability procedure to clarify that multiple test failures should also be evaluated for common cause under 10 CFR 50.73(a)(2)(vii) and that setpoint drift is a common cause.
- Evaluate the existing test procedure, valve performance, appropriateness of maintaining the current TS limit, and take actions accordingly.
No regulatory commitments are associated with this report.
ADDITIONAL INFORMATION
Failed Component Information: None
Previous Similar Events:
- LER 2000-003-00, Docket No. 387/License No. NPF-14, "Multiple Test Failures of Suppression Chamber-to-Drywell Vacuum Breakers"
- LER 2000-007-00, Docket No. 387/License No. NPF-14, "Multiple Test Failures of Main Steam Safety Relief Valves"
- LER 2001-005-00, Docket No. 388/License No. NPF-22, "Multiple Test Failures of Main Steam Safety Relief Valves.