05000346/FIN-2011002-04
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Finding | |
|---|---|
| Title | Licensee-Identified Violation |
| Description | Technical Specification 3.7.5 B requires that an inoperable auxiliary feedwater train be restored to operable status in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Contrary to this, in August 2010, the licensee determined that auxiliary feedwater train 2, because of a failed position controller board for the pumps discharge valve, had been inoperable for a period of approximately 18 days. The licensees investigation determined that the failure was attributable to the controller board experiencing a voltage higher than the boards design for a period of time sufficient to cause failure and that the higher voltage was caused by a ground on the dc bus power supply to the board. The licensee also determined that there was a previous failure of the same board for the same reason and that the licensee had failed to recognize the potential significance of a direct current bus ground and failed to assign proper priority for finding and eliminating the ground. The licensee documented the condition in CR 10-81273. Inspection Manual Chapter 0609,Significance Determination Process, screening indicated a need to perform Phase 3 internal and external events analyses for determining the significance of the event. These analyses were performed by the Region III Senior Reactor Analyst staff. The total estimated delta core damage frequency (CDF) for the 18-day exposure time was the sum of the internal events contribution (4.2E-7/yr) and the external events contribution (3.4E-7/yr) or 7.6E-7/yr. Based on the Phase 3 analysis, the inspectors determined that the finding was of very low safety-significance. |
| Site: | Davis Besse  |
|---|---|
| Report | IR 05000346/2011002 Section 4OA7 |
| Date counted | Mar 31, 2011 (2011Q1) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Licensee-identified |
| Inspection Procedure: | |
| Inspectors (proximate) | J Rutkowski A Wilson D Kimble T Go J Cameron |
| INPO aspect | |
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Finding - Davis Besse - IR 05000346/2011002 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2011Q1
Self-Identified List (Davis Besse)
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