05000275/FIN-2009005-04
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Finding | |
|---|---|
| Title | Less than Adequate Replacement Reactor Head Modification Design Control |
| Description | The inspectors identified a noncited violation of Title 10 CFR, Part 50, Appendix B, Criterion III, Design Control, after the design contractor failed to perform adequately calculations demonstrating that the replacement reactor head met ASME Code acceptance criteria. The contractor failed to use the critical seismic damping values specified in the plant design basis for the design of the integrated head assembly and the control rod drive mechanism housing assembly and when calculating component stress during a postulated design basis earthquake. The licensee entered this condition into the corrective action program as Notifications 50276107 and 50276288. The inspectors concluded that the failure to properly implement the plant design basis in the replacement head design was a performance deficiency. The finding is more than minor because the performance deficiency is associated with the Initiating Events Cornerstone design control attribute and adversely affected the cornerstone objective to limit the likelihood of loss of a coolant accident during a seismic event. The inspectors determined the finding is of very low safety significance because assuming worst case degradation, the finding would not result in exceeding the Technical Specification limit for reactor coolant system leakage nor have likely affected other mitigation systems resulting in a total loss of their safety function. This finding has a crosscutting aspect in the area of problem identification and resolution associated with the corrective action program component because the licensee did not identify the use of improper damping values with a low threshold for identifying issues during oversight of contractor activities and design reviews, P.1(a) |
| Site: | Diablo Canyon  |
|---|---|
| Report | IR 05000275/2009005 Section 4OA5 |
| Date counted | Dec 31, 2009 (2009Q4) |
| Type: | NCV: Green |
| cornerstone | Initiating Events |
| Identified by: | NRC identified |
| Inspection Procedure: | |
| Inspectors (proximate) | G Guerra M Brown M Peck G George G Miller S Makor D Graves N Greene |
| CCA | P.1, Identification |
| INPO aspect | PI.1 |
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Finding - Diablo Canyon - IR 05000275/2009005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Diablo Canyon) @ 2009Q4
Self-Identified List (Diablo Canyon)
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