Modeling dihydrogen generation and release from geopolymer under y-ray irradiation

Cantarel, V.   ; Chupin, F.; Ortega-Charlot, M.*; 山岸 功 ; 上野 文義  

Cantarel, V.; Chupin, F.; Ortega-Charlot, M.*; Yamagishi, Isao; Ueno, Fumiyoshi

The use of geopolymers as inorganic solids such as cement and geopolymer for the immobilization of radioactive waste is economical, can be done at room temperature, with a low dispersal of radio-active materials during treatment. On the other hand, they contain water, which decomposes under radiation from radioactive materials to produce dihydrogen (H) gas. We investigate the generation of H gas to evaluate the risk of pressurization and combustion after treatment. Irradiation was performed in the Gammatec experimental facility with the French Atomic Energy Agency (CEA). In this study, the effect of the scale of the solidified product on the H emission was investigated and modeled. The experimental values became constant with time and lower than the source term measured with powder sample (2210 mol/J). This is thought to be due to the recombination (reaction back to water) and diffusion of H in the solidified product. We have created a model considering the dynamic of H diffusion and recombination using finite elements to reproduce the data. It can also be extrapolated to predict H generation as a function of the scale of the waste drum. At the assumed full-scale size (200 L), the H generation is noticeably smaller, confirming that the H source term is not scale independent. Current work aims at extending these results to other matrices and evaluating effects of dose rate on the dynamic.