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Topics
Modeling Hydrogen Generation and Release from Geopolymer Under γ-Ray Irradiation
−Confirmation of the Effectiveness of Geopolymer Immobilization of Radioactive Waste−
Fig. 1 Experimental data on hydrogen (H2) gas generation from geopolymer (a), and predictive model of scale effects (b)
(a) 2 L geopolymer samples from standard (●) and high pH production (●). The amount of H2 source term is constant with time, but the total amount of H2 generated in the high pH preparation is less because the recombination (reaction back to water) of H2 is more pronounced at high pH. (b) The model assumes that the geopolymer is placed in a cylindrical waste drum. The greater the height of the waste drum, the smaller the amount of H2 source term, the width of the curve accounts for variability in the pH and other factors at the time of production.
Immobilization of radioactive waste in inorganic solids is important to prevent the spread of radioactive materials into the environment and to allow safe handling of the waste. These wastes usually contain water which decomposes to dihydrogen (H2) under radiation from radioactive materials, which could limit the waste load. It is necessary to study the generation of H2 gas to assess the risk of pressurization and combustion of the solidified waste after treatment. The use of geopolymers as inorganic solids is economical because immobilization can be performed at room temperature, and the dispersion of radioactive materials during treatment is reduced compared to high temperature treatment.
In this study, the effect of the size of the solidified product on the H2 emission was investigated and modeled. The experiments were conducted in collaboration with the French Atomic Energy Commission (CEA), using their irradiation facility. Fig. 1a shows the experimental results of H2 production (size 2 L, height 22 cm). The experimental values remained constant over time, presumably due to recombination (reaction back to water) and diffusion of H2 in the solidified product. Extending these results from experimental to industrial scale, we have developed a predictive model of H2 generation as a function of waste drum height (height to diameter ratio constant), shown on the Fig. 1b. At the assumed full-scale size (200 L), the H2 generation is significantly lower, confirming the usefulness of geopolymers in waste immobilization.
In this study, the effect of the size of the solidified product on the H2 emission was investigated and modeled. The experiments were conducted in collaboration with the French Atomic Energy Commission (CEA), using their irradiation facility. Fig. 1a shows the experimental results of H2 production (size 2 L, height 22 cm). The experimental values remained constant over time, presumably due to recombination (reaction back to water) and diffusion of H2 in the solidified product. Extending these results from experimental to industrial scale, we have developed a predictive model of H2 generation as a function of waste drum height (height to diameter ratio constant), shown on the Fig. 1b. At the assumed full-scale size (200 L), the H2 generation is significantly lower, confirming the usefulness of geopolymers in waste immobilization.
Acknowledgements
The experiments were conducted in collaboration with the French Atomic Energy Commission (CEA), using their irradiation facility.
Author (Researcher) Information
 | Name | Vincent Cantarel |
|---|---|
| Waste Stream Research Group, Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Fukushima Research and Engineering Institute |
Reference
March 31, 2025
Research and Development Related to the Accident at TEPCO's Fukushima Daiichi NPS [R&D for decommissioning the FDNPS]