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Journal Articles

Online measurement of the atmosphere around geopolymers under gamma irradiation

Cantarel, V.; Lambertin, D.*; Labed, V.*; Yamagishi, Isao

Journal of Nuclear Science and Technology, 58(1), p.62 - 71, 2021/01

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The gas production of wasteforms is a major safety concern for encapsulating active nuclear wastes. For geopolymers and cements, the H$$_{2}$$ produced by radiolytic processes is a key factor because of the large amount of water present in their porous structure. Herein, the gas composition evolution around geopolymers was monitored on line under $$^{60}$$Co gamma irradiation. Transient evolution of the hydrogen production yield was measured for samples with different formulations. The rate of its evolution and the final values are consistent with the presence of a chemical reaction of the pseudo-first order consuming hydrogen in the samples. The results show this phenomenon can significantly reduce the hydrogen source term of geopolymer wasteform provided their diffusion constant remains low. Lower hydrogen production rates and faster kinetics were observed with geopolymers formulations in which pore water pH was higher. Besides hydrogen production, a steady oxygen consumption was observed for all geopolymers samples. The oxygen consumption rates are proportional to the diffusion constants estimated in the modelization of hydrogen recombination by a pseudo first order reaction.

Journal Articles

On the hydrogen production of geopolymer wasteforms under irradiation

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

Journal of the American Ceramic Society, 102(12), p.7553 - 7563, 2019/12

 Times Cited Count:5 Percentile:48.77(Materials Science, Ceramics)

The hydrogen gas (H$$_{2}$$) production of wasteforms is a major safety concern for encapsulating nuclear wastes. For geopolymers, the H$$_{2}$$ produced by radiolytic processes is a key factor because of the large amount of water present in their porous structure. Herein, the hydrogen production was measured under $$^{60}$$Co gamma irradiation. The effect of water saturation and sample size were studied for pure geopolymers, or using zeolites as an example waste. When geopolymer monolithic samples were large and saturated by water, the hydrogen released was measured up to two orders of magnitude lower with a 40 cm long cylinder samples (1.9$$times$$10$$^{-10}$$ mol/J) than a sample in powder form (2.2$$times$$10$$^{-8}$$ mol/J). To interpret results, a simple model was used, considering only hydrogen production, a potential recombination and its diffusion in the geopolymer matrix. Knowing the diffusion constant of the matrix, the model was able to reproduce the evolution of the hydrogen release as a function of the water saturation level and predict the evolution when sample size is increased up to 40 cm.

Journal Articles

3D X Ray micro-tomography as a tool to formulate metakaolin-based geopolymer-oil emulsions

Lambertin, D.*; Davy, C. A.*; Hauss, G.*; Planel, B.*; Marchand, B.*; Cantarel, V.

Proceedings of 1st International Conference on Innovation in Low-Carbon Cement and Concrete Technology (ILCCC 2019) (USB Flash Drive), 4 Pages, 2019/06

Composite materials made of geopolymer (GP) cement and organic liquids are useful to synthetize porosity-controlled media, for the management of radioactive organic liquid waste, or as phase change materials (PCM). Indeed, GP cements are able to integrate huge amounts of organic oils by direct emulsion in the fresh paste. The emulsion (GEOIL) remains stable during GP hardening. In this contribution, by using 3D X Ray micro Computed Tomography (micro CT) with a voxel size of 1 micron$$^{3}$$, we investigate the effect of formulation parameters (oil proportion, Si/Al molar ratio, surfactant) on the 3D oil droplet structure of GEOIL pastes. Samples are emulsified in the fresh state, and imaged in the hardened state. Porosity, oil droplet size distribution and mean distance between droplets are all determined quantitatively. It is observed that the presence of surfactant provides significantly smaller oil droplets. The increase in Si/Al ratio also decreases the oil droplet sizes, but to a lesser extent.

Journal Articles

Hydrogen production of Zeolite A containing geopolymers

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

Proceedings of 3rd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2018) (USB Flash Drive), 4 Pages, 2018/10

Geopolymers were successfully synthesized with different water content and loading of zeolites (0 to 40%wt). Zeolite A, geopolymer and their composites were then irradiated by a $$^{60}$$Co source (1.5 to 2.5 kGy/h) up to 10 kGy. The hydrogen was measured by GC after irradiation. Yields of radiolitic hydrogen were obtained for individual components. Obtained yields suggested a recombination process during irradiation. The system was then modelled to explain the observed behavior and predict the hydrogen production under $$gamma$$ ray irradiation of larger samples.

JAEA Reports

Geopolymers and their potential applications in the nuclear waste management field; A Bibliographical study

Cantarel, V.; Motooka, Takafumi; Yamagishi, Isao

JAEA-Review 2017-014, 36 Pages, 2017/06

JAEA-Review-2017-014.pdf:3.37MB

After a necessary decay time, the zeolites used for the water decontamination will eventually be conditioned for their long-term storage. Geopolymer is considered as a potential matrix to manage radioactive cesium and strontium containing waste. For such applications, a correct comprehension of the binder structure, its macroscopic properties, its interactions with the waste and the physico-chemical phenomena occurring in the waste form is needed to be able to judge of the soundness and viability of the material. Although the geopolymer is a young binder, a lot of research has been carried out over the last fifty years and our understanding of this matrix and its potential applications is progressing fast. This review aims at gathering the actual knowledge on geopolymer studies about geopolymer composites, geopolymer as a confinement matrix for nuclear wastes and geopolymer under irradiation. This information will finally provide guidance for the future studies and experiments.

Oral presentation

Scale up effect on geopolymer H$$_{2}$$ production under gamma irradiation

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

no journal, , 

The present study aimed at completing previous results on geopolymer H$$_{2}$$ 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$$_{2}$$ consumption allowed to predict correctly the effective experimental hydrogen production. A strong dependency between H$$_{2}$$ 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.

Oral presentation

On the hydrogen production of geopolymers under gamma irradiation

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

no journal, , 

Oral presentation

Gas diffusion effect on H$$_{2}$$ release caused by water radiolysis in geopolymer

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

no journal, , 

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