Understanding of location,amount and properties of fuel debris and FP distribution

　The following are the ways to estimate the location, amount and properties of fuel debris and the FP distribution based on the logic tree in Figure 1

①Estimation by actual unit investigation

Investigations of certain structures such as internal conditions of the RPV/PCV and S/C and torus rooms, and the whole image of the fuel debris using of the muon detection system.

②Estimation by analysis

Analysis is conducted using accident progression analysis codes.

③Estimation based on knowledge and experiments

Estimation from the knowledge and experiments is conducted by studies based on the past accidents and researches and engineering studies on plant data and experiments on simulated debris.