Study on Description of Plant Status at Fukushima Accident by Emergency Action Level

This paper aims at verifying the current Japanese Emergency Response Guideline, especially the “notification” (reporting) scheme of emergency action level (EAL), through the analysis of the progress of Fukushima nuclear accident. We compared timing and emergency classification between two datasets of the plant statuses which expressed by the old prediction-based notification and the latest EAL-based notification, in order to assess the current EAL scheme along the effectiveness of protective action for the local residents. We observed that the plant statuses expressed by the current EAL-based notification gave more engineering insights in the earliest accident phase to identify the accident scenario. However, potential improvement area of the guideline was also observed in the following severe accident management (SAM) phase after the trigger of first precautionary action, where we are required to reduce uncertainties in both processes of the operator's notification and the government's decision making by evaluating the progression speed of the severe accident.