05000354/LER-2013-005
| Hope Creek Generating Station | |
| Event date: | 10-18-2013 |
|---|---|
| Report date: | 12-17-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3542013005R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) Safety Relief Valves - {SB/RV}* - EllS Identifier Solenoid Operated Valve — {SB/FSV}* — EllS Identifier *Energy Industry Identification System {EllS} codes and component function identifier codes appear as (SS/CCC)
IDENTIFICATION OF EVENT
Event Date: October 18, 2013 Discovery Date: October 18, 2013
CONDITIONS PRIOR TO EVENT
Hope Creek Generating Station (HCGS) was shutdown, in Operational Condition (OPCON) 5, for the eighteenth refueling outage (H1R18).
DESCRIPTION OF EVENT
During the 2013 Hope Creek Generating Station (HCGS) refueling outage (H1R18), all 14 pilot valve solenoid operated valve (SOV){SB/FSV} assemblies (5 Dual SOVs & 9 Single SOVs) for the Main Steam Safety Relief Valves (SRV){SB/RV} were removed and sent to NWS Technologies, LLC (NWS) for required 'as-found' functional and air leakage testing. On October 18, 2013, NWS notified HCGS that the single solenoid operated valve (SOV) H1AB- 1ABSV-3664A-B21 (S/N 481), which is associated with the pilot valve assembly for SRV 1ABHV-F013P (SRV-P), had failed to actuate, and thereby, did not pass the 'as-found' functional testing. The SOV failure affected operability of the relief valve function and the low-low set function of SRV-P required by Technical Specification (TS) 3.4.2.2. The failed SOV was quarantined and sent to an external vendor for failure analysis.
The SRV-P SOV (SIN 481) was a new valve purchased from Target Rock for installation in refueling outage H1R17.
SOV S/N 481 was functionally tested at Target Rock on March 14, 2012, and installed onto the SRV-P pilot valve in H1R17 on April 27, 2012. SOV (S/N 481) was removed and tested in H1R18. A new replacement Target Rock SOV was installed in H1R18.
On December 12, 2013, HCGS received the results of the failure analysis from the external vendor. From the failure analysis, HCGS confirmed that the SOV failure occurred at some point during the operating cycle. Technical Specification 3.4.2.2 requires the relief valve function and the Low-Low Set function of the SRV-H and SRV-P to be operable in Operational Condition 1, 2, and 3. With one SRV inoperable the TS action requires that the valve be restored to operable within 14 days or be in Hot Shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Cold Shutdown in the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Therefore, the SRV-P was inoperable for a period longer than the TS allowed outage time; however, the SRV-H remained operable. This condition is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as an operation or condition that was prohibited by the plant's Technical Specifications.
CAUSE OF EVENT
The cause of the failure of solenoid valve (S/N 481) was determined to be a manufacturer's assembly error. The external vendor found that the anti-rotation pin that secures the adjustable plunger was not installed. Without the pin, the plunger was allowed to rotate and unthread until contacting the internal stop, which prevented the solenoid from picking up when energized. The solenoid coil was in good condition; there was no Indication of an Internal short. The SOV was reassembled with the plunger re-threaded in place. With the valve body installed back on the solenoid, the SOV could be operated. HCGS determined from the results of the failure analysis that the failure of this SOV occurred at some point during the operating cycle.
SAFETY CONSEQUENCES AND IMPLICATIONS
The safety consequences of this occurrence are minimal. The basis of the Low-Low Set function is to ensure that the safety/relief valve discharges are minimized for a second opening of SRVs following any overpressure transient. This is achieved by automatically lowering the closing and opening setpoints of two SRVs. In this way, the frequency and magnitude of the containment blowdown duty cycle is substantially reduced. The failed SOV affected SRV-P; however, the SRV-H remained operable. With the SRV-H operable, the low-low set function remained available. Further, the SOV for the SRV-H was satisfactorily tested by NWS on October 18, 2013; therefore, SRV-H was capable of fulfilling its safety function. Sufficient redundancy is provided for the low-low set system such that failure of any one valve to open or close at its reduced setpoint does not violate the design basis.
The failure of the SOV did not impact the automatic safety valve function of the SRV-P based on SRV-P as-found pilot valve testing completed on November 22, 2013. SRV-P is an 1120 PSIG set pressure safety relief valve, which tested satisfactory in H1R18 with an as-found setpoint of 1152 PSIG (+2.9%).
SAFETY SYSTEM FUNCTIONAL FAILURE
A review of this condition determined that a Safety System Functional Failure (SSFF) as defined in NEI 99-02, "Regulatory Assessment Performance Indicator Guidelines," did not occur. This condition did not prevent the ability of a system to fulfill its safety function to either shutdown the reactor, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident.
PREVIOUS EVENTS
A review of events at Hope Creek for the past five years was performed to determine if a similar event had occurred. No events involving the failure of the SOV associated with an SRV pilot valve was identified.
CORRECTIVE ACTIONS
1. The solenoid operated valve associated with the SRV-P pilot valve was replaced.
COMMITMENTS
This LER contains no regulatory commitments.