05000336/FIN-2017002-01
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Finding | |
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| Title | Potential Untimely Corrective Action for Anchor Darling Double Disc Gate Valves |
| Description | The inspectors identified that Dominion has not implemented corrective actions to address potential substantial safety hazards associated with several safety significant valves at Millstone Unit 2 that was reported in a 10 CFR Part 21 notification letter dated February 25, 2013. Specifically, after establishing a corrective action plan, to date Dominion has not implemented actions to either evaluate or inspect susceptible valves. However, inspectors need to compare actions taken to Dominions CAP requirements and review industry recommendations to address the Part 21 letter to determine if this represents a performance deficiency or violation of NRC requirements. As a result, the NRC has opened an unresolved item (URI) related to this issue of concern. Description. In 2012, Browns Ferry Nuclear Plant Unit 1 experienced a failure of an isolation valve due to a failure of the valve stem to wedge anti-rotation wedge pin as noted in a 10 CFR Part 21 Notification Letter dated January 4, 2013. Subsequent analysis by Flowserve, owner of Anchor/Darling, determined the cause was a manufacturing defect, wherein the wedge pin installation torque was insufficient to meet the design needs of the valve. Flowserve further concluded that other valves of this type, Anchor Darling double disc gate valves in motor operated valve (MOV) applications with Limitorque or Rotork actuators, could be susceptible to similar failures. As documented in the associated 10 CFR Part 21 Notification Letter from Flowserve dated February 25, 2013, Millstone was susceptible to a potential substantial safety hazard due to this potential failure mechanism. Dominion captured this condition in CR504097 and determined that the following Millstone Unit 2 valves were susceptible: CS-4.1A, Containment Spray Header Isolation CS-4.1B, Containment Spray Header Isolation CS-13.1A, RWST Outlet Isolation CS-13.1B, RWST Outlet Isolation CS-16.1A, Containment Sump Outlet Header Isolation CS-16.1B, Containment Sump Outlet Header Isolation The Dominion fleet MOV Program owner accepted the action (CA284339) to establish a corrective action plan on November 21, 2014, approximately 21 months after 10 CFR Part 21 notification by Flowserve. The corrective action plan for the susceptible valves included valve performance monitoring consistent with current MOV program requirements as well as stem position monitoring during travel every cycle which would indicate potential degradation of the wedge pin. Ultimate resolution for each location incorporates valve disassembly, intrusive inspection, and re-torque of the stem/wedge connection to mitigate the notified potential substantial safety hazard. To date, Dominion has not performed stem position monitoring, contrary to their corrective action plan, thereby limiting their capacity to identify wedge pin degradation without assessment of the change. Furthermore, due to the invasive nature of the ultimate resolution as well as the safety functions of the susceptible locations, final corrective actions for each valve must be performed with the unit offline. Dominion initially established ultimate resolution at each location in spring of either 2016 or 2017 without alignment to an outage schedule or cycle plan. On February 16, 2016, because the 2016 valves would be worked during a refueling outage, the facilities safety review committee met, extending due dates until June 1, 2017. Immediately preceding the spring 2017 refueling outage, Dominion realigned ultimate resolution for the susceptible valves to the fall 2018 and spring 2020 refuel outages due to failure to receive parts required to complete contingency maintenance. Ultimately, from February 25, 2013, through the present, the inspectors identified that Dominion delayed implementation of corrective actions for multiple potential substantial safety hazards that was communicated in a 10 CFR Part 21 notification letter. However, inspectors need to compare actions taken to Dominions CAP requirements and review industry recommendations to address the Part 21 letter to determine if this represents a performance deficiency or violation of NRC requirements. (URI 05000336/2017002-01, Potential Untimely Corrective Action for Anchor Darling Double Disc Gate Valves) |
| Site: | Millstone  |
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| Report | IR 05000336/2017002 Section 4OA5 |
| Date counted | Jun 30, 2017 (2017Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 40001 |
| Inspectors (proximate) | J Ambrosini L Mckown C Highley H Anagnostopoulos M Modes J Grieves |
| INPO aspect | |
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Finding - Millstone - IR 05000336/2017002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Millstone) @ 2017Q2
Self-Identified List (Millstone)
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