120 Development of Risk Assessment Method for Fire Caused by Earthquake (IV) (PSAM-0128)

In Japan, earthquakes occur frequently. In 1995, the Great Hanshin Earthquake struck the western region of Japan, and caused the worst damage to the nation. The damage included the secondary disasters such as fires caused by the quake. It cannot be ignored that there is a possibility of a nuclear power plant accident caused by the loss of safety functions by a fire, even if the earthquake itself is not strong enough to destroy equipment. Therefore it is necessary to establish an assessment method for the risk of fires caused by earthquakes. The purpose of this research is to establish such an assessment method in the framework of Probabilistic Safety Assessment (PSA). For this purpose, we have set four tasks and started a five-year research project in 1999. In Task 1, we obtained detailed and sufficient information on earthquakes and fires, which were necessary to develop realistic and meaningful scenarios. In Tasks 2 and 3, the “ignition code” and “fire progression analysis code”, were developed. The ignition code is a code that assesses equipment damages caused by earthquake and the probability of catching fire. On the other hand, the fire progression analysis code simulates a fire progression. We conducted experiments for the fire progression analysis code, which were very useful to verify the parameters. In Task 4 we examined these methods developed in this study by utilizing them on assessments of a sample plant.

In the assessments of a sample plant, the scenarios for occurrence of fires caused by an earthquake discussed in Task 1 were utilized effectively. The results of this study will be applicable not only for the assessment of nuclear power plants but also for chemical plants, traffic systems etc.