Scale up effect on geopolymer H production under gamma irradiation

Cantarel, V.   ; Arisaka, Makoto ; Yamagishi, Isao 

The present study aimed at completing previous results on geopolymer H production under irradiation, taking into account physical phenomena such as gas diffusion. Experimental data showed the consumption of hydrogen by the wasteform itself under irradiation provided hydrogen diffusion was slow enough or the sample large enough. Sample with the same water content and same internal chemistry were shown to have very different effective radiolytic yield by modification of the sample dimensions (100 times smaller for a 40 cm long cylinder compared to the powder of the same sample). A simple model taking in account only hydrogen gas diffusion in the sample, its production and a pseudo first order reaction for the H consumption allowed to predict correctly the effective experimental hydrogen production. A strong dependency between H production, wasteform dimensions and sample permeation properties was highlighted and understood. This difference in our vision of hydrogen production opens new horizons for active waste immobilization.