05000336/LER-2009-004
| Docket Numbersequential Revmonth Day Year Year Number No Month Day Year 05000 | |
| Event date: | 11-11-2009 |
|---|---|
| Report date: | 01-11-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3362009004R00 - NRC Website | |
1. Event Description On November 11, 2009, while Millstone Power Station Unit 2 (MPS2) was in Mode 5 at 0% power, the operators discovered a thermal relief valve [RV] in the inservice test (1ST) program was not tested or replaced within the allowed time interval as required by the ASME OM Code Mandatory Appendix 1, paragraph 1-1390, and when subsequently tested the valve failed its acceptance criteria. The 1ST program requires class 2 and 3 pressure relief devices used for thermal relief be tested or replaced on a ten year interval, i.e., once per ten years. Technical Specification (TS) 4.0.5 invokes ASME Code (Code) requirements and specifically excludes Code required ISTs with frequencies greater than 2 years from the provisions of TS 4.0.2 (maximum 25% grace period). The valve was replaced approximately seven and a half months beyond the end of the current ten year test interval. The relief valve is on the inlet to the 'B' containment spray pump seal cooler [BE, P, CLR]. NUREG 1022, 'Event Reporting Guidelines, 10 CFR 50.72 and 50.73' provides guidance that if a surveillance test is performed beyond its required scheduled date and fails, it is assumed the failure occurred at the time the test should have been performed. It is therefore assumed the valve was not capable of performing its relief function for approximately seven and a half months.
This event is reportable as an operation or condition prohibited by Technical Specifications per 10 CFR 50.73 (a)(2)(i)(B).
MPS2 is designed such that a closed cooling water system (reactor building closed cooling water {RBCCW} [CC]) is utilized to cool equipment that could be potentially contaminated (e.g., low and high pressure safety injection pumps, containment spray pumps, and shutdown heat exchangers). Where the piping configuration is such that a portion of the system could be isolated and its contents heated up, the Code requires a relief valve be installed for thermal protection of the piping.
Upon investigation it was determined that at no time during the period when the relief valve was considered 'failed' was the RBCCW system configured such that the relief valve would have been required to provide its relief function.
2. Cause The cause of the missed 1ST was determined to be failure to follow procedures. The preventive maintenance (PM) program was selected as the vehicle to ensure the 1ST surveillance frequency requirements were met. The PM program is controlled by procedure and requires a basis for any changes to a PM frequency. The governing procedure required a preventive maintenance change request (PMCR) be generated. In this case the planner changed the required completion date on these components without initiating PMCR(s). The PMCR(s) would have provided for the review of the requested due date changes for acceptability as well as documenting the basis for the date changes.
3. Assessment of Safety Consequences This condition was determined to be of low safety significance because at no time during the period when the relief valve was considered 'failed' was the RBCCW system configured such that the relief valve would have been required to provide its relief function, and therefore no safety systems or components were inoperable and incapable of performing their safety functions.
4. Corrective Action The planners were briefed on the event and counseled on the need to follow station procedure requirements.
The relief valve was replaced with an operational valve. Additional corrective actions will be evaluated in accordance with the station's corrective action program.
The extent of condition review determined there are 51 thermal relief valves at MPS2. The required completion dates for these valves have been reviewed and no other issues were found. There are 56 thermal relief valves on MPS3. The test history for these valves was reviewed and all 56 valves have been tested within the last ten years.
5. Previous Occurrences No previous similar events/conditions were identified.
Energy Industry Identification System (EllS) codes are identified in the text as [XX].