05000316/FIN-2015003-02
Finding | |
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| Title | Failure of Steam Dump Valves Results in Plant Trip |
| Description | A finding of very low safety significance (Green) was self-revealed on April 23, 2015, when two condenser steam dump valves failed open during startu
following the Unit 2 refueling outage. In response to the failure, the licensee manually tripped the Unit 2 reactor. Contrary to the requirements of PMP5040MOD007, Engineering Modifications, the design of the new valves that were installed was not compatible with the steam dump system. This finding does not involve enforcement action because no violation of a regulatory requirement was identified. The licensee replaced three steam dump valves on Unit 2 with a new design during the spring refueling outage. Shortly following reactor startup, two of the new valves failed open after being placed in service. The resulting temperature transient required operators to manually trip the reactor to comply with Technical Specification (TS) requirements for minimum temperature while critical. Design work and planning to perform the modifications failed to meet timeliness milestones prior to the outage. Contrary to the modification procedure for these circumstances, the change was not considered fast-track, therefore, additional risk assessments and management oversight were not provided. As a result, the operational impact of the new design was not fully realized. The steam dump system can be subject to significant amounts of condensate. The new valves trapped some of the condensate. This, along with a different plug design, caused a backpressure of sufficient force to cause the valves to fail open when steam was admitted. The licensee stabilized the plant following the trip, replaced two valves with the old design, isolated the other via a temporary modification, and returned the unit to service. The issue was also entered into the Corrective Action Program (CAP) as Action Request (AR) 20155825. The issue was more than minor because it adversely affected the Design Control attribute of the Initiating Events Cornerstone, whose objective is to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Specifically, the inadequate design caused the new valve to fail open, which resulted in a manual reactor trip. Utilizing IMC 0609, Appendix A, The Significance Determination Process (SDP) for Findings At-Power, effective July 1, 2012, the inspectors determined the finding was Green, or very low safety significance, by answering no to the Transient Initiators question in Exhibit 1. Specifically, while the transient caused a plant trip, all mitigation equipment remained available to respond to the trip. The inspectors determined the finding had an associated cross-cutting aspect in the Human Performance area, namely, H.8, Procedure Adherence. The licensee failed to follow the requirements of the modification procedure, which would have prompted a more thorough review of the modification. |
| Site: | Cook  |
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| Report | IR 05000316/2015003 Section 1R18 |
| Date counted | Sep 30, 2015 (2015Q3) |
| Type: | Finding: Green |
| cornerstone | Initiating Events |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71111.18 |
| Inspectors (proximate) | J Ellegood J Lennartz J Mancuso K Riemer M Garza M Learn R Edwards R Elliott T Taylor |
| CCA | H.8, Procedure Adherence |
| INPO aspect | WP.4 |
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Finding - Cook - IR 05000316/2015003 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Cook) @ 2015Q3
Self-Identified List (Cook)
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