[2B14-17] Cement and Geopolymer

[2B17] Study on the Radionuclide Contamination Mechanisms of Concrete and the Estimation of Distribution of Radionuclides

(26) Important factors for the contamination survey and estimation of concrete in Fukushima Daiichi NPP: cracks, aggregate, cement, competitive ions, dry-carbonation-Ca leaching, reversibility/irreversibility of ion adsorption

*Kazuo Yamada¹, Ippei Maruyama², Kazutoshi Shibuya³, Yasumasa Tojo⁴, Haruka Aihara⁵, Yoshifumi Hosokawa⁶, Go Igarashi⁷, Yoshikazu Koma⁵ (1. NIES, 2. UTokyo, 3. Taiheiyo Consultant, 4. Hokkaido Univ., 5. JAEA, 6. Taiheiyo Cement, 7. Nagoya Univ.)

Keywords:Fukushima Daiichi NPP, Concrete, Contamination, Cracks, Aggregate, Carbonation, Irreversible adsoprtion

Many studies have been carried out on the mechanisms of radioactive contamination of concrete. In the investigation and estimation of contamination after the Fukushima Daiichi Nuclear Power Plant (1F) accident, the factors specific to the 1F accident that should be considered are summarised. Firstly, cement type and aggregate as materials, then drying, carbonation and cracking as concrete conditions, and finally the reaction between competing ions and contaminated water as contamination history. These factors can change the apparent diffusion coefficient and adsorption by an order of magnitude or more, and it is insufficient to refer to or consider studies that do not take these factors into account.1F Post-accident concrete contamination has occurred through ion penetration, which is due to the interaction between the pore water in the concrete and the solid phase. The interactions can be ion exchange and dissolution/re-precipitation reactions. In the case of ion exchange, normal ion adsorption does not retard ion penetration, while fixed adsorption of Cs, e.g. by aggregates, causes significant penetration retardation.