05000275/FIN-2008004-02
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Finding | |
|---|---|
| Title | Failure to Perform a Safety Assessment for Following Discovery of Explosive Gas in the Auxiliary and Containment Buildings |
| Description | The inspectors identified a noncited violation of 10 CFR Part 50, Appendix B, Criteria V, Instructions, Procedures, and Drawings, after Pacific Gas and Electric personnel failed to perform a safety assessment prior to implementing a temporary procedure on July 20, 2008, to transfer an explosive gas mixture from the waste gas system to the Unit 2 vent. The explosive mixture of oxygen and hydrogen was discovered in the Unit 2 reactor coolant drain tank, waste gas surge tank, and interconnecting piping. The licensee also identified that the Unit 2 pressurizer relief tank vapor space exceeded the lower flammable limits. The explosive and flammable gas created a condition outside the plant design bases and was inconsistent with safety analysis. Plant Procedure TS3.ID2, Licensing Basis Impact Evaluation, required the licensee to have performed a safety assessment prior to conducting activities outside the design bases and inconsistent with safety analysis. The licensee entered this condition into the corrective actions system as Action Request A0741069. This finding is greater than minor because explosive and flammable gas within the containment and auxiliary buildings affected the Initiating Events Cornerstone objective to limit the likelihood of events that may upset plant stability and challenge critical safety functions during power operations and protect against external factors such as fire and explosions. The inspectors used Inspection Manual Chapter 0609, Appendix F, Fire Protection Significance Determination Process, to analyze the significances of the finding. The inspectors determined this finding was a fire prevention and administrative controls category due to the failure to meet the equipment control guideline for combustible gas flammability limits. The inspectors concluded that that this finding is of very low safety significance because the condition represented a low degradation rating due to the lack of a direct ignition source. This finding has a crosscutting aspect in human performance in the area of Decision Making because the licensee failed to use the systematic process provided in Procedure TS3.ID when making a safety significant or risk-significant decision when faced with the unexpected explosive gas mixture within containment and auxiliary building plant systems H.1(a) |
| Site: | Diablo Canyon  |
|---|---|
| Report | IR 05000275/2008004 Section 1R05 |
| Date counted | Sep 30, 2008 (2008Q3) |
| Type: | NCV: Green |
| cornerstone | Initiating Events |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | M Brown M Peck P Elkmann L Ellershaw S Graves J Adams |
| CCA | H.13, Consistent Process |
| INPO aspect | DM.1 |
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Finding - Diablo Canyon - IR 05000275/2008004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Diablo Canyon) @ 2008Q3
Self-Identified List (Diablo Canyon)
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