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Immobilization of highly radioactive and long-lived isotope of 129I, which is a fission product in spent nuclear fuel, requires development of new durable host-materials.
Iodine is a very volatile chemical element, and even its chemically strong compounds such as AgI and CuI are not stable under ultraviolet irradiation or oxidizing conditions. Therefore, development of host materials for iodine immobilization is based on unusual approach – the search and testing of new compounds which were not studied before in respect of iodine sorption and strong fixation.
Although FCC material demonstrated high loading capacity to iodine sorption it is necessary to take into account that FCC itself is not a final form of 129I immobilization. Either for disposal in geological formation or iodine transmutation in nuclear reactors the FCC should be converted into more chemically and mechanically durable material. In case of transmutation it is necessary to provide, also, an acceptable «transparency» of final material to neutron fluxes. Therefore, we decided to consider two main groups of durable compounds: silicon carbides and carbon nitrides (of fullerene structure) as possible targets of FCC conversion. It was assumed that synthesis of SixCy might be carried out at relatively low temperature as a result of chemical reaction between FCC and Si-organic chemicals. Successful synthesis of CxNy of fullerene-like structure might be carried out using N-ion bombardment of carbon material.
In the framework of first year (“KRI-KIRSI”-HRC Agreement 280203) we have studied optimal synthesis conditions and principal features of FCC. The preliminary results have been obtained from precise XRD analyses of iodine-doped and pure FCC samples before and after gamma-irradiation. It was found that iodine doping and irradiation caused principal changes in phase composition of FCC such as substituting of crystalline fullerene C60 (formed by benzene-like carbon rings) for crystalline chaoite phase (formed by carbyne carbon chains). It was decided to continue these experiments during second (current) year (“KRI-KIRSI”-HRC Agreement 280203-1) in comparison with study of activated carbon. In our experiments we decided to use samples of activated carbon SKT-3S that is widely used in Russian nuclear industry for different purposes including sorption of 129I.
Absorption; Fullerenes; Iodine — Isotopes; Radioactive wastes; Reactor fuel reprocessing; Sequestration (Chemistry); Silicon carbide; Sorbents
Iodine--Isotopes; Radioactive wastes; Sorbents
Chemistry | Oil, Gas, and Energy | Physical Chemistry
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Burakov, B. E.
Development, Fabrication and Study of Fullerene-Containing Carbon Material (FCC) for Immobilization of Iodine: Final report 2005.
Available at: https://digitalscholarship.unlv.edu/hrc_trp_separations/49