05000311/LER-2012-002
| Docket Numbersequential 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 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| 3112012002R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
Westinghouse — Pressurized Water Reactor (PWR/4) Auxiliary Feedwater System (AFW) {BAN * Energy Industry Identification System {EMS} codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF OCCURRENCE
Event Date: July 5, 2012 Discovery Date: July 5, 2012
CONDITIONS PRIOR TO OCCURRENCE
Salem Unit 2 was in Operational Mode 1 at 100% power with no other structures, systems or components inoperable at the time of the discovery that contributed to the event.
DESCRIPTION OF OCCURRENCE
On July 5, 2012, Salem Unit 2 was in Mode 1, operating at 100% power and steady state conditions.
In-service testing of the 21 AFW Pump was in progress in accordance with station surveillance testing procedure S2.0P-ST.AF-0001. At approximately 0307 hours0.00355 days <br />0.0853 hours <br />5.076058e-4 weeks <br />1.168135e-4 months <br /> upon start of the 21 AFW Pump, 23AF21, the AFW Flow Control Valve to the 23 SG was observed to be open. Flow to the 23 SG was observed along with an increase in 23 SG level. Normal in-service testing of the 21 AFW Pump aligns the pump discharge for recirculating flow back to the AFW Storage Tank {BA/TK} and flow to a SG is not an expected condition for this test. The control room operator attempted to manually close the valve from the control panel but the valve would not respond to valve controller demand. At approximately 0308 hours0.00356 days <br />0.0856 hours <br />5.092593e-4 weeks <br />1.17194e-4 months <br /> the 21 AFW Pump was stopped from the control room and the 23AF21 valve was verified to have closed automatically.
Unit 2 declared entry into two Technical Specification (TS) Action Statements at 0307 hours0.00355 days <br />0.0853 hours <br />5.076058e-4 weeks <br />1.168135e-4 months <br />. TS 3.7.1.2 was entered for inoperability of the 21 AFW Pump and TS 3.6.3 was entered for inoperability of Containment Isolation Valve 23AF21.
At 0325 hours0.00376 days <br />0.0903 hours <br />5.373677e-4 weeks <br />1.236625e-4 months <br /> the AFW flow path to the 23 SG was manually isolated in compliance with TS Action Statement 3.6.3. At 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, troubleshooting identified the cause of the failure to be the � misposition of an air supply valve to the 23AF21 electro-pneumatic converter. The valve was returned to its normally open position. Valve 23AF21 was retested successfully and the unit exited TS 3.6.3 at 1220 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.6421e-4 months <br />. A successful retest of the 21 AFW Pump was performed and the 21 AFW Pump was declared operable. TS 3.7.1.2 was exited at 1349 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.132945e-4 months <br />.
An 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> report to the NRC was made at 1745 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.639725e-4 months <br /> under 10 CFR 50.72(b)(3)(v)(D), "Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems needed to mitigate the consequences of an accident.
CAUSE OF OCCURRENCE
Troubleshooting identified the cause of the failure to be the misposition of air supply valve 2FA3957 IV to the 23AF21 electro-pneumatic converter. The air supply valve was in the closed position instead of its normal open position. Valve 2FA3957 IV is located in local AFW system air control panel 205-2. The 23AF21 valve is an air to dose actuating valve and a loss of air to the flow control valve electro pneumatic converter caused 23AF21 to fully open on the start of the 21 AFW Pump.
A review of work history in the area which might have affected the 23AF21 air supply valve could not identify the cause of the mispositioned valve. The likely cause of this event was inadvertent valve manipulation of 2FA3957 IV sometime between the time of discovery and the previously performed AFW surveillance test on April 5, 2012. A causal evaluation of this event is in progress.
PREVIOUS OCCURRENCES
A review of LERs for Salem Units 1 and 2 for the previous three years did not identify any similar events.
SAFETY CONSEQUENCES AND IMPLICATIONS
This event did not adversely affect the ability of the AFW system to deliver AFW flow to the SGs. The 21 AFW Pump was capable of performing its design function of providing AFW flow to the 23 and 24 SGs.
This event is reported under 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications." The mispositioning of the air supply valve to 23AF21 may have placed the 21 AFW Pump in an inoperable status as early as the last in-service test of the 21 AFW Pump which occurred on April 5, 2012 (91 days). This would have made the AFW Pump inoperable for a period greater than the AFW TS 3.7.1.2 Allowed Outage Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for single pump inoperability. Further investigation of maintenance and testing history indicated that the 23 AFW Pump was also inoperable due to scheduled maintenance for approximately 29 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br /> during this period. This could have created a condition in which two AFW Pumps were inoperable for a time exceeding the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AFW TS 3.7.1.2 Allowed Outage Time for two pump inoperability. The Containment Isolation function of 23AF21 would also have been inoperable during this 91, day period exceeding the Containment Isolation Valve TS 3.6.3 isolation requirement of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
This event is also reported under 50.73(a)(2)(v)(D), "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident." The Salem Updated Final Safety Analysis Report (UFSAR) assumptions for a postulated Steamline Break and Main Feedline Break allow only 10 minutes for operators to perform necessary actions to terminate AFW flow to a faulted SG. In the case of a steamline or main feedline break, blow down of the affected SG could cause a Lo-Lo SG Level AFW Pump auto-start actuation signal to lock-in preventing the stopping of the AFW Pump from the control room panel and continue to feed the SG. Emergency Operating Procedures provide continuous action steps for isolating a faulted SG. A failed open 23AF21 which could not be closed from the control room would need to be locally closed, isolated, or it's associated 21 AFW Pump breaker would need to be tripped. Subsequent steaming through the SG fault greater than the 10 minute time could result in higher containment design pressure and temperature.
A review of this event determined that a Safety System Functional Failure as defined in Nuclear Energy Institute (NEI) 99-02 did occur.
CORRECTIVE ACTIONS
1. An extent of condition component lineup verification was performed on both Salem Units 1 and 2 for the AFW system air control panels. No other issues were identified.
2. A causal evaluation is in progress to determine root causes and any further corrective actions.
COMMITMENTS
No commitments are made in this LER