05000302/FIN-2004009-05
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Finding | |
|---|---|
| Title | Motor Operated Valves Not Protected From Hot Shorts that Could Bypass Torque Switches |
| Description | The team noted that the licensees Appendix R Fire Study indicated that a number of motor-operated valves were not protected from certain hot shorts that could spuriously actuate the valve and also bypass the torque and limit switches. The team noted that such an occurrence could potentially defeat the post-fire SSD strategy, and the licensee planned to further evaluate whether such a vulnerability actually existed. This issue is unresolved pending NRC review of the licensees evaluation. The licensees Appendix R Fire Study stated that many MOVs have had their control circuits modified such that hot shorts which can spuriously actuate the valves will not be able to bypass the torque and limit switches as addressed in NRC Information Notice 92-18. The Fire Study further stated that one exception to this is for a fire located at the valves motor control center. The team noted that fires could occur at motor control centers, and if such a fire caused a hot short that spuriously actuated a motor operated valve that was needed for post-fire SSD and also bypassed the torque switch, the valve could be rendered inoperable by becoming jammed into its valve seat. Consequently, operators would not be able to subsequently open the valve. The team also noted that the plant design included MOVs that were relied upon for both A train and B train post-fire SSD. Examples included the makeup pump minimum-flow valves. These two MOVs were installed in series in the combined minimum-flow line for all three makeup pumps. One was powered from the A train and one from the B train of the electrical system. If either one of these valves were to become damaged in the closed position, all minimum-flow for all makeup pumps would be lost. However, the licensees Appendix R Fire Study relied on having makeup pump mininimum-flow available for post-fire SSD. Another example would be the decay heat drop line, which similarly included two MOVs in series. In response to NRC questions about this potential vulnerability that could affect post-fire SSD, the licensee initiated NCR 148225 to further evaluate whether such a vulnerability actually existed. This issue is unresolved pending NRC review of the licensees evaluation: URI 05000302/2004009-005, Motor Operated Valves Not Protected From Hot Shorts That Could Bypass Torque Switches. |
| Site: | Crystal River  |
|---|---|
| Report | IR 05000302/2004009 Section 1R05 |
| Date counted | Mar 31, 2005 (2005Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | D Payne J Quinones-Navarro T Harrison X Bellarmine R Rodriguez C Smith R Schin G Wisemann Merriweatherm Thomas J Munday L Suggs J Dymek |
| INPO aspect | |
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Finding - Crystal River - IR 05000302/2004009 | |||||||||||||||||||||||||
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Finding List (Crystal River) @ 2005Q1
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