05000237/FIN-2010002-08
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Finding | |
|---|---|
| Title | Licensee-Identified Violation |
| Description | Title 10 CFR Part 50, Appendix B, Criterion III, Design Control, requires that design changes, including field changes, shall be subject to design control measures commensurate with those applied to the original design and be approved by the organization that performed the original design unless the applicant designates another responsible organization. Contrary to this requirement, on November 3, 2009, it was identified that changes had been made, either intentionally or unintentionally, to the design of the plant by the removal of several Unit 2 core spray instrument piping supports, for an indeterminate period of time, without the application of appropriate design control measures. This finding was entered into the licensees corrective action program as IR 1002474. The licensees corrective actions included: restoration of the supports to the original design configuration; creation of a preventive maintenance activity to walk down piping supports prior to the drywell closeout; and an action to walkdown the Unit 3 drywell to verify all supports are connected and tight. The inspectors used Table 4b of IMC 0609.04, Phase 1 Initial Screening and Characterization of Findings to evaluate the significance of the finding. The finding was determined to involve the degradation of equipment specifically designed to mitigate a seismic event. The impact of the finding was that a seismic event could have resulted in the failure of the core spray dp line which would cause a seismically-induced small loss of coolant accident (LOCA) event with the possible unavailability of the B core spray train. The finding screened as potentially risk significant using the screening criteria of Table 4b. The RIII Senior Risk Analyst (SRA) performed a phase 3 SDP evaluation of the finding using the Dresden Standardized Plant Analysis Risk (SPAR) Model and the Risk Assessment of Operational Events Handbook, Volume 2 External Events. The SRA used the seismic initiating event frequency for Dresden (4.58E-04/yr) from the handbook and assumed that any seismic event would cause the failure of the core spray dp line and result in a small LOCA. A conditional core damage probability was estimated using the SPAR model by assuming a small LOCA event occurred simultaneous with a loss of offsite power and the unavailability of the B core spray train. The seismic initiating event frequency was combined with the estimated conditional core damage probability to estimate the delta CDF. The delta CDF calculated was less than 1E-7/yr, which is a finding of very low safety significance (Green). The dominant core damage sequences involved a seismically-induced small LOCA followed by the failure of both high and low pressure injection |
| Site: | Dresden  |
|---|---|
| Report | IR 05000237/2010002 Section 4OA7 |
| Date counted | Mar 31, 2010 (2010Q1) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Licensee-identified |
| Inspection Procedure: | |
| Inspectors (proximate) | C Phillips D Melendez-Colon E Coffman J Draper M Ring R Krsek R Russell W Slawinski |
| INPO aspect | |
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Finding - Dresden - IR 05000237/2010002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Dresden) @ 2010Q1
Self-Identified List (Dresden)
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