05000354/LER-2010-003
| Docket Number Sequential Revmonth Day Year Year Month Day Yearnumber No. | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3542010003R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) RHR/LPCI System (BWR) - EllS Identifier {BO}* Relief Valve - El IS Identifier {RV} * * Energy Industry Identification System {EIIS} codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF OCCURRENCE
Event Date: November 1, 2010 Discovery Date: November 1, 2010
CONDITIONS PRIOR TO OCCURRENCE
Hope Creek was in Operational Condition Five (OPCON 5) for the sixteenth refueling outage (H1R16).
No structures, systems or components were inoperable at the time of discovery that contributed to the event.
DESCRIPTION OF OCCURRENCE
In December 2009 a Hope Creek self assessment included a technical review of all components in the In service Test (1ST) program to ensure that the testing being performed matched the ASME Code requirements based on the classification of each component. This review discovered a technical error in the testing being performed on 1BCPSV-4425 {RV}, Residual Heat Removal (RHR) {BO} Shutdown Cooling (SDC) suction relief valve.
1BCPSV-4425 is an ASME Class One (1) valve, but had been improperly grouped with 10 RHR system Class Two (2) and Three (3) valves. ASME OM Code, Mandatory Appendix I, Section I-1320 specifies that Class 1 valves be tested on a maximum interval of five years, with a minimum of 20% of each valve group tested in any 24 month period. Section 1-1350 governs testing frequency for Class Two (2) and Three (3) valves and specifies a maximum testing interval of ten years, with a minimum of 20% of each valve group tested in any 48 month period. As a result of the error in grouping, 1BCPSV-4425 has been, throughout the life of the plant, tested on a ten year, instead of a five year interval.
1BCPSV-4425 was last tested on October 25, 2007. Since there is no other ASME Class One (1) valve of this type, it would be in a group all by itself and therefore required to be tested every 24 months. As such, this discovery constituted a missed surveillance for 1BCPSV-4425 and required application of Technical Specification (TS) 4.0.3.
A risk evaluation was performed in accordance with TS 4.0.3 on December 17, 2009 to justify delay of the DESCRIPTION OF OCCURRENCE (cont'd) test until the Fall 2010 refueling outage. A bounding evaluation was performed in accordance with the procedure for risk assessments of missed or deficient surveillances. The evaluation for the TS surveillance for 1BCPSV-4425 Shutdown Cooling Suction line safety relief valve function supported a maximum deferral time equal to the normal surveillance interval. The evaluation concluded there was no significant increase in risk as a result of the missed surveillance. The surveillance test was performed during the Fall 2010 refueling outage (H1R16). The test results were unsatisfactory. The setpoint for the valve is 1250 psig.
The as-found setpoint was 1346.3 psig which is outside the ± 3% acceptable range [Reference — ASME OM Code-2001, Mandatory Appendix I (Inservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants), Section 1-1300 Guiding Principles, Subsection 1-1320 Test Frequencies, Class1 Pressure Relief Valves, Paragraph (c) Requirements for Testing Additional Valves, Subsection (1)] .
Therefore, this failed late surveillance is reportable per 10 CFR 50.73(a)(2)(i)(B).
CAUSE OF OCCURRENCE
A review of available plant documents, including all applicable procedures and the original program data base, and discussions with the IST Engineer identified the apparent cause of the error in grouping as a technical rigor application deficiency that occurred at the inception of the Hope Creek relief valve program development in 1985.
The relief valve was replaced with a spare and the removed valve was disassembled. No replacement parts were required. The valve was reassembled, bench calibrated, and returned to stock as a spare.
The most likely cause of the failure of the valve to actuate within the acceptable band is corrosion bonding or bridging.
PREVIOUS OCCURRENCES
A review of LERs for the three prior years at Hope Creek was performed to determine if a similar event had occurred. Two similar events were identified:(1) During the 2009 Hope Creek refueling outage when six Main Steam Safety Relief Valves (SRVs) were found out of the TS required limits of +/- 3%.
This event was reported as LER 354/2009-002-00 and its supplement 354/2009-002-01(2) During the 2010 Hope Creek refueling outage when six Main Steam SRVs were found out of the TS required limits of +/- 3%. This event was reported as LER 354/2010-002.
SAFETY CONSEQUENCES AND IMPLICATIONS
1BCPSV-4425 is located on the common RHR shutdown cooling suction line. The valve is located between inboard and outboard isolation valves H1BC-1BCV-071 and H1-1BCV-164 respectively. The valve is a safety relief valve with a minimum design capacity of 0.1 gpm (ref. Specification 10855-M 141(Q), Appendix C). The valve is designed to relieve system pressure in the event of a primary containment isolation signal that would cause the referenced valves to close following the system reaching maximum design values. Per the design piping specification the maximum pressure and temperature this piping is rated for is 1375 psig and 575 °F. During the as found testing the relief valve lifted at 1346.3 psig, lower than the maximum rating of the piping. The valve moving off of its seat would relieve enough pressure to meet the requirement of 0.1 gpm, since the full open capacity is 100 GPM at 10% accumulation. Therefore a 10% accumulation for this application is very conservative and the valve would have performed its design function upon initial opening.
A review of this event determined that a Safety System Functional Failure (SSFF) did not occur as defined in Nuclear Energy Institute (NEI) 99-02, "Regulatory Assessment Performance Indicator Guideline".
CORRECTIVE ACTIONS
(1) Upon discovery of the improper grouping of 1BCPSV-4425, an immediate, detailed, item by item review of all relief devices in the IST program was performed individually by the IST Program Manager and the Relief Valve Program manager. This review was focused specifically on the ASME classification of the valves and whether or not any other components were not appropriately grouped per their classification. This review confirmed that 1BCPSV-4425 is the only IST relief device, other than the Main Steam Safety Relief Valves, that are Class 1 components. All other IST relief devices are Class 2 and 3 and assigned to groupings with the appropriate testing frequency based on Classification and function. (Complete) (2) The operating experience of this event was rolled to the Programs Engineering Group by the Manager of that group as a re-enforcement for the need for thorough technical rigor application in the production and review of engineering products. (Complete) (3) The procedure for testing of Hope Creek ASME class 1, 2, 3 safety/relief valves was revised to establish a new valve group for 1BCPSV-4425. (Complete) (4) The Maintenance Plan for 1BCPSV-4425 was revised to 18 months not to exceed 24 months.
(Complete) (5) 1BCPSV-4425 was replaced with a spare (that was satisfactorily tested), rebuilt, bench calibrated and returned to stock. (Complete)