Results of detailed analyses performed on boring cores extracted from the concrete floors of the Fukushima Daiichi Nuclear Power Plant reactor buildings

Maeda, Koji  ; Sasaki, Shinji  ; Kumai, Misaki; Sato, Isamu; Osaka, Masahiko  ; Fukushima, Mineo ; Kawatsuma, Shinji; Goto, Tetsuo*; Sakai, Hitoshi*; Chigira, Takayuki*; Murata, Hirotoshi*

Due to the earthquake and tsunami, and the following severe accident at the Fukushima Daiichi Nuclear Power Plant, concrete surfaces within the reactor buildings were exposed to radioactive liquid and vapor phase contaminants. In order to clarify the situation of this contamination in the buildings of Units 1-3, selected samples were transported to the FMF of JAEA-Oarai where they were subjected to analyses to determine the surface radionuclide concentrations and to characterize the radionuclide distributions. In particular, penetration of radio-Cs in the surface coatings layer and sub-surface concrete was evaluated. The analysis results indicate that the situation of contamination in the building of Unit 2 was different, and the protective coatings on the concrete floors provided significant protection against radionuclide penetration. The localized penetration of contamination was found to be confined within 1 mm of the surface of the coating layer of some mm.