05000247/FIN-2007007-03
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Finding | |
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| Title | Use of Motor Control Center Methodology for Periodic Verification of the Design Basis Capability of Safety- Related MOV |
| Description | The team identified an unresolved item (URI) concerning the adequacy of the motor control center (MCC) testing methodology used for periodic verification of the design bases capability of safety-related MOVs. Entergy implemented MCC testing in 2004 as a method of implementing periodic verification in addition to the previously NRCreviewed method of taking stem thrust and torque measurements at the valve. The MCC method uses motor current, voltage, and winding resistance measured at the MCC to calculate motor torque of the valves motor operator. The calculated motor torque is then compared to motor torque target and limit values based on 1) packing loads, 2) thrust required to close the valve, 3) stall motor torque, and 4) valve or actuator structural limits. Entergy Report IP-RPT-04-00890, Technical Basis for Using MCC Technology for Periodic Verification Testing at IP 2 and IP 3, states that this methodology would be used initially on MOVs with generally low safety significance and high operating margin, but also states that the report applies to all safety related MOVs at IP 2 and IP 3. Since 2004, Entergy has used the MCC methodology for periodic verification on nine safety-related MOVs: three high risk, three medium risk, and three low risk MOVs, where risk significance is defined as the combined effects of MOV risk of failure and safety significance. Based on the available information, the team was unable to verify that the MCC method had been appropriately validated. Specifically, there did not appear to be a justified correlation between the MCC methodology calculated motor torque and actual stem thrust and torque. It was also unclear whether the MCC methodology had adequate allowances to compensate for its uncertainties in establishing MOV design basis capability (such as uncertainties related to stem friction coefficient, load sensitive behavior, and actuator efficiency) since stem thrust and stem torque are not directly measured. MCC testing was performed in 2004 as a periodic verification test on MOV 747, the No. 21 RHR heat exchanger discharge valve, a high risk valve. The team identified that this test was invalid because this was not performed in accordance with IP-RPT-04-00890. Specifically, MOV 747 was tested using the Motor Torque Method of MCC testing which, according to IP-RPT-04-00890, is only valid for motors whose torque is between 2 and 60 foot-pounds. The motor on MOV 747 is an 80 foot-pound. motor and use of the Correlated Thrust/Torque Method was required. As a result, Entergy exceeded the sixyear periodic verification test interval for MOV 747 because the last at the valve valid performance verification test was performed in May 2000. Entergy has provided justification for the reasonable continued operability of the valve until its scheduled testing in 2008 based on successful in-service tests, stem lubrication and actuator preventive maintenance and inspection performed in 2006. The team reviewed Entergys basis for the operability of MOV 747 and determined that there was reasonable assurance of continued operability of the MOV. Entergy committed to follow the Joint Owners Group program for periodic verification of MOVs in their response to NRC Generic Letter 96-05. This periodic verification program established valve margin by measuring stem thrust and torque at the valve. Entergys response did not indicate that the MCC method would be used for MOV periodic verification. The MCC test method for periodic verification of MOVs is a departure from the NRCreviewed method, which is based on direct measurement of stem thrust and torque. The acceptability of the use of the MCC methodology for periodic verification of MOVs will be an unresolved item pending further NRC review. Included with this review will be a determination of whether the MOV performance testing conducted on MOV 747 constitutes a violation of NRC requirements. |
| Site: | Indian Point  |
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| Report | IR 05000247/2007007 Section 1R21 |
| Date counted | Mar 31, 2007 (2007Q1) |
| Type: | URI: |
| cornerstone | Initiating Events, Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | H Anderson J Lilliendahl S Pindale W Sherbin J Krafty D Orr S Kobylarz S Smithk Mangana Ziedonis S Smith L Doerflein |
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Finding - Indian Point - IR 05000247/2007007 | |||||||||||||||||||||||||
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Finding List (Indian Point) @ 2007Q1
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