Research Article
Accident Sequence Precursor Analysis of an Incident in a Japanese Nuclear Power Plant Based on Dynamic Probabilistic Risk Assessment
Table 1
Assumed reliability model of EDGs.
| | Status | EDG-A | EDG-B | Remark | | Failure probability (−) | Failure timing (h) | Failure probability (−) | Failure timing (h) |
| | Base | 1 × 10−2 | Uniform (0, 4) | 1 × 10−2 | Uniform (0, 4) | Assuming normal condition | | State i | 1 × 10−2 | Uniform (0, 4) | 1 × 10−1 | Uniform (0, 4) | Assuming degradation of EDG-B, set failure rate 10 times higher than the base case | | State ii | 1 × 10−2 | Uniform (0, 4) | 1 | Normal (1, 0.1) | EDG-B failure is assumed to occur with certainty, and the time of occurrence is assumed to be uncertain | | State iii | 1 × 10−1 | Uniform (0, 4) | 1 | Normal (1, 0.1) | Assuming degradation of EDG-A, set failure rate 10 times higher than the base case | | State iv | 1 | Normal (1, 0.1) | 1 | Normal (1, 0.1) | EDG-A failure is assumed to occur with certainty, and the time of occurrence is assumed to be uncertain | | State v | — | This state is in scope of low-power or shutdown mode PRA and excluded from our evaluation |
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