In order to formulate a fuel debris retrieval plan, it is desirable to reorganize information on the in-core condition obtained from actual equipment investigations, experiments, knowledge, accident progression analyses, or other sources and to improve the estimation of the condition of each unit.

Since it is not possible to confirm the entire inside of the PCV and the RPV, it is desirable to estimate the condition of parts that cannot be visually confirmed, by using analysis and evaluation technologies. These require not only the acquisition and detailed analysis of a portion of the debris, but also evaluation that pays attention to consistency with objective data. In order to maintain technical capability and human resources, it is important to conduct research such as experiments and analyses, and to constantly improve the accuracy of predictions through the exchange of opinions among experts on the content of analysis data and analysis evaluations.

The fuel debris retrieval method, the process management, and the integrity evaluation of structure are important issues because they may lead to improve work efficiency and safety. For this reason, it is important to understand the condition in the reactor that overlook these decommissioning processes (decommissioning management). Mainly during the fuel debris retrieval period and the PCV/RPV/building dismantling period, the in-core status should be updated on an ad-hoc basis based on the results of internal investigations and accident progression analyses and it needs to function as a hub (information collection point) for outputting to the decommissioning process.