05000346/FIN-2011004-01
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Finding | |
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| Title | |
| Description | On September 15, 2011, instrumentation and controls (I&C) technicians replaced the HPI 3A and 3B flow instrument signal monitors with refurbished modules. Upon insertion of the module into the cabinet, the control room received an unexpected alarm for ICS Input Mismatch. The alarm immediately cleared and was attributed to a slight disruption in voltage when the modules were inserted. A decision was made to continue replacement activities. On September 16, 2011, I&C technicians commenced PMT of the signal monitors. During the string check of the HPI flow instrument alarms, annunciator alarm 14-4-E, ICS Input Mismatch, was received. The alarm initially cleared, then returned. Coincident with ICS Input Mismatch alarm, the plants ICS began reducing reactor power without any operator input. On-watch plant operators entered procedure DB-OP-02526, Primary to Secondary Plant Upset, and went through actions of placing ICS stations in manual control. The I&C technicians performing the HPI flow instrument signal monitor refurbishment were directed to stop their activities. Reactor power initially dropped to approximately 95 percent before operators stabilized the plant, and then returned reactor power to approximately 100 percent using manual controls. The refurbished HPI flow instrument signal monitor modules were removed from the system and taken to the I&C shop for inspection and testing, while the original signal monitor modules were reinstalled. Inspection and testing of the refurbished modules in the I&C shop did not reveal any issues. The modules have been sent to the licensees testing laboratory for further analysis. The inspectors continued to review the circumstances surrounding the event to determine if the issue was within the licensees ability to foresee and correct and should have been prevented. Pending further review of the licensees cause analysis, the issue is considered an unresolved item. |
| Site: | Davis Besse  |
|---|---|
| Report | IR 05000346/2011004 Section 4OA5 |
| Date counted | Sep 30, 2011 (2011Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | |
| Inspectors (proximate) | A Wilson D Kimble J Beavers J Maynen J Neurauter J Steffes L Jones M Bielby M Holmberg R Jones T Bilik T Goa Wilsond Kimble J Cameron J Neurauter J Steffes L Jones M Holmberg M Mitchell P Cardona Morales P Smagacz T Briley T Go |
| INPO aspect | |
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Finding - Davis Besse - IR 05000346/2011004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2011Q3
Self-Identified List (Davis Besse)
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