Comprehensive Analysis and Evaluation of Fukushima Daiichi Nuclear Power Station Unit 2

Estimation and understanding of the state of the fuel debris and fission products inside the plant comprise an essential step in the decommissioning of Tokyo Electric Power Company Holdings’ Fukushima Daiichi nuclear power station (1F). However, because of the plant’s high-radiation environment, direct observation of the plant interior is difficult. Therefore, in order to understand the plant’s interior conditions, comprehensive analysis and evaluation based on various measurement data from the plant, analysis of plant data during the accident progression phase, and information obtained from computer simulations for this phase are necessary. These evaluations can be used to estimate the conditions of the interior of the reactor pressure vessel (RPV) and the primary containment vessel (PCV). This paper addresses 1F Unit 2 as the subject to produce an estimated map of the fuel debris distribution from data obtained about the RPV and PCV based on comprehensive evaluation of various measurement data and information obtained from the accident progression analysis, which were released to the public in June 2018.