05000348/FIN-2011010-09
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Finding | |
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| Title | Evaluation of MDAFW Pump Suction Check Valves |
| Description | The team identified an URI regarding the licensees identification and evaluation of corrective actions taken to address AFW pump suction check valve oscillations. In 2005 the licensee retained services of Kalsi Engineering to perform an analysis of the effects of partially open TDAFW pump suction check valves (2446, Kalsi Engineering, Auxiliary Feedwater Check Valve Analysis for Farley Nuclear Plant, Rev. 0, January 24, 2006). The engineering analysis determined that for 100 gpm of flow the check valve opening was 0.7 degrees with a disc peak-to-peak oscillating angle of 1.89 degrees. For 400 gpm of flow the check valve opening was 10.4 degrees with a disc peak-to-peak oscillating angle of 7.58 degrees. The analysis concluded that for each flow condition oscillation would not result in significant hinge pin wear. The scope of this review was limited to the TDAFW pump suction check valves only and the MDAFW pump suction check valves were not included in the analysis. The team noted that the 6 MDAFW pump suction check valves are the same model as the 8 TDAFW pump suction check valves. The teams review of the operating conditions for the AFW pump suction check valves identified the following observations: The quarterly inservice testing of the MDAFW pumps is performed at or near minimum flow conditions. The flow was not measured during the test; only the pumps differential pressure was monitored. The AFW system functional description indicates that this flow was approximately 50 gpm. The team determined that at this MDAFW pump flowrate, the check valve flow velocity was approximately 0.56 ft/sec, which was less than the TDAFW approximate velocity of 0.64 ft/sec at 100 gpm. However, since MDAFW pump flow was not monitored during testing, any pump flow instability due to suction check valve oscillations may not be revealed during the current method of testing. Degradation (partial sticking) of the MDAFW pump suction check valves may not be identified by routine testing. If these valves are partially stuck open, then functional testing by either the quarterly surveillances or the comprehensive surveillance test will not reveal this condition, since higher-than-design-basis CST levels would mask the valve being partially stuck open. On October 2, 2008, the licensee initiated CR 2008110018, which identified that while the TDAFW pump was running in a minimum flow alignment, the pump exhibited flow fluctuations at the flow rates below approximately 230 gpm. The licensee attributed this condition to a partially open TDAFW suction check valve (Q2N23V0006). During the subsequent troubleshooting, the licensee disassembled this check valve on October 28, 2008, and verified that the check valve was functioning properly without any abnormal wear indications. Proposed corrective actions considered replacement of the swing check valves with the in-line check valves. However, because of the reliability concerns and difficulty in performing maintenance inspections on that type of check valve, this modification was not pursued. Additionally, the team noted that the MDAFW pump suction check valves were not inspected. Based on a review of the operating and corrective action history related to AFW check valve oscillations for this issue over the last 5 years, the team concluded that there was not sufficient evidence to conclude that the MDAFW pump suction check valves would not be subject to the same oscillation issue that was observed on the TDAFW pump. Additionally, the team noted that the check valve oscillating condition that had been previously evaluated for the TDAFW pumps, had not been evaluated for MDAFW pumps |
| Site: | Farley  |
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| Report | IR 05000348/2011010 Section 1R21 |
| Date counted | Dec 31, 2011 (2011Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | E Crowe A Nielsen F Ehrhardt G Kuzo S Sandal B Collins J Sowa C Dykesd Jonesm Shlyamberg S Sandal R Nease J Eargle P Wagner |
| INPO aspect | |
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Finding - Farley - IR 05000348/2011010 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Farley) @ 2011Q4
Self-Identified List (Farley)
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