05000346/FIN-2016001-02
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Finding | |
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| Description | As discussed in Section 1R12.1 of this report, during the colder months of the year the demand on the SW system is reduced. During these winter months, the licensee operates the system in a mode specifically intended to reduce header pressure to avoid any challenges to the SW header relief valves, as the reduced SW flow requirements would otherwise tend to cause SW header pressure to rise. In this header pressure control mode, the SW side of a spare HX is placed in service to allow flow to pass without cooling any loads, and the increased SW system flow subsequently reduces SW header pressure back down to a more nominal value. Licensee operating crews frequently utilize the swing CCW HX No. 3 to perform this function, and its associated outlet valve (SW37) is throttled by procedure to accomplish this. Again, as discussed in Section 1R12.1 of this report, SW37 has experienced a number of leakage issues, at least in part, as a result of this practice. Most recently, excessive through leakage on SW37 was identified in March of 2015 (CR 201503283). Initially, the licensees evaluation of the condition only evaluated the impact of the through leakage on the valves isolation function. The evaluation concluded that the valve could be considered operable, but degraded, since an alternate means of isolation was available. The evaluation did not, however, assess the impact of the valve degradation on operation of the SW system if CCW HX No. 3 were to be placed in service or credited to be aligned to one of the CCW and SW headers in standby. As licensee engineering and technical personnel were preparing for an upcoming SW system flow test, their analyses of the condition began to suggest that small changes in the resistance of SW37 as a result of continued valve degradation could impact SW flow and possibly challenge minimum SW design basis flow assumptions for certain accident scenarios. As a result, in January of 2016 the licensee prohibited use of CCW HX No. 3 as an in-service or standby HX (CR 201600438). However, the licensees evaluation of the condition continued to permit CCW HX No. 3 and SW37 to be used for SW header pressure control. In reviewing the issue, the inspectors noted that the licensees evaluation, as documented in CR 201600438 and entered into their CAP, did not contain any technical justification for the continued use of SW37 in header pressure control mode. Field observations by the inspectors revealed that the licensee operations staff had attached a plant information tag to the SW37 valve hand wheel warning personnel of the degraded condition of the valve and the potential for rendering SW Header No. 1 inoperable if the valve position were to be altered. Given the unknown condition of the SW37 valve internals, the unknown extent of the degradation of the valves liner/seat, and the unknown nature of the mechanism causing the degradation, the inspectors questioned how it could be possible for the licensee to conclude that use of SW37 in header pressure control mode would be acceptable. On February 18, 2016, the inspectors raised their concerns on this matter to the licensees operations supervisory staff, and asked to be provided with the licensees technical basis for continued operability of the SW system with the degraded SW37 being utilized for header pressure control. After several days had passed without receiving an answer, the inspectors elevated the question to the Site Vice President on February 23, 2016. On February 24, 2016, licensee engineering and operations management informed the inspectors that CCW HX No. 3 and SW37 had been removed from SW header pressure control and would be precluded from further use in that manner pending additional licensee analysis. The licensee entered this issue into their CAP as CR 201602667. Because the inspectors had not yet received the results of the licensees additional analysis concerning the use of CCW HX No. 3 and SW37 for SW header pressure control at the end of this inspection period, the issue is being treated as an unresolved item (URI) pending the inspectors review of the licensees completed evaluation. (URI 05000346/201600102) |
| Site: | Davis Besse  |
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| Report | IR 05000346/2016001 Section 1R15 |
| Date counted | Mar 31, 2016 (2016Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | D Kimble J Cameron T Briley L Alvaredod Kimblej Cameron J Cassidy J Rutkowski N Valos T Bilik T Briley |
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Finding - Davis Besse - IR 05000346/2016001 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2016Q1
Self-Identified List (Davis Besse)
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