R&D project to estimate radioactive source distributions inside reactor building rooms; Overview and key results

Suzuki, Masahiro ; Machida, Masahiko  ; Yamaguchi, Takashi ; Miyamura, Hiroko  ; Yamada, Susumu  ; Okamoto, Koji; Hasegawa, Yukihiro*; Yoshida, Toru*; Wei, S.*

In order to promote decommissioning in 1F, it is crucial to find out strong radioactive hot spots inside reactor building rooms based on environmental measurement data composed of structural surface model data and distribution data of air dose rates. Such hot spot prediction allows to reduce radiation risks of persons working inside 1F and consequently to safely construct access routes to remove fuel debris. We introduce a new scheme to inversely estimate radioactive source distributions using LASSO. The scheme is composed of multiple steps, e.g., one of the most essential steps is to select measurement points of air dose rates. In addition, we develop the other engines calculating 3D distributions of air dose rates from the estimated source distributions together with a tool simulating virtual countermeasures and visualizing various outputs of the above engines in 3D space. In the present paper, we overview R&D project to integrate the above three engines.