Issues related to FP behavior for improvement of decommissioning work efficiency and source-term predicting accuracy, 5; Issues extracted from the investigations of accident analyses by NRA

Karasawa, Hidetoshi; Okada, Hidetoshi*; Hidaka, Akihide*

In order to contribute to "contributing to the improvement of source term prediction technology", which is one of the objectives of this committee, meeting materials of the "Study Group on Analysis of the Accident at TEPCO's Fukushima Daiichi Nuclear Power Station" conducted by the Nuclear Regulation Authority have been surveyed. Among them, meeting materials related to three areas were examined. (1) Contamination of the piping system for emergency gas treatment systems and their formation mechanisms, (2) Radiation levels on the operation floor and near the shield plugs and the presence of cesium between the shield plugs, and (3) Dose distribution in the building. As a result of the survey, the following issues were identified. Project 1: Evaluation of vent gas radiation dose, Project 2: Contamination mechanism of bent lines, Project 3: Confirmation of PCV leak pathways. In the future, these issues will be examined and evaluated by working groups, and the progress and results of activities will be summarized in a technical report to help improve the FP emission model.