Minimization of cobalt nuclide emissions in supercritical water oxidation of spent resin

Review of the destruction of organic radioactive wastes by supercritical water oxidation

Organic materials, such as ion exchange resins, plastic, oils, and solvents, are widely used in the operation and decommission of nuclear facilities. The generated radioactive organic wastes are both radioactive and organic; therefore, the degradation of such wastes becomes more difficult. Due to delays in the disposal of radioactive organic wastes, potential safety risks are increasing. With the advantages of degrading refractory organics rapidly and thoroughly, supercritical water oxidation (SCWO) has become a potential alternative way to degrade radioactive organic wastes. This review focused on the degradation characteristics of different radioactive wastes from the perspective of potential practical applications. Some improved methods for facilitating the degradation of radioactive wastes by SCWO are considered and analyzed. Moreover, the kinetics and intermediate pathways of radioactive organic wastes are further analyzed. The distribution, migration and transformation of radionuclides during the SCWO reaction, as well as the further processing of radionuclides in gas-, liquid- and solid-phase products, were summarized and discussed. Furthermore, some fruitful areas for further work were reviewed for the highly efficient degradation of radioactive organic wastes. This review can provide useful information and guidance for the industrial applications of SCWO treatment for radioactive wastes.

Nanoscale Fe0/Cu0 bimetallic catalysts for Fenton-like oxidation of the mixture of nuclear-grade cationic and anionic exchange resins

Spent resins generated from the nuclear industrial processes are still difficult to be treated and disposed. Fenton-like processes have great application potential in the treatment of spent resins, but the Fenton reaction mechanisms and resin degradation pathways remain challenging. In this study, nanoscale Fe⁰/Cu⁰ bimetallic catalysts were prepared and characterized for the Fenton-like degradation of the mixture of cationic and anionic resins. High catalytic property of Fe⁰/Cu⁰ bimetallic nanoparticles activated by H₂O₂ was evaluated, according to the effects of various nanoparticles, temperature, catalyst amount, H₂O₂ concentration and the mixing ratio of cationic and anionic resins. Combined the shape and color changes of mixed resins with the experimental and calculated characterization results, different degradation difficulty of cationic and anionic resins and their degradation mechanisms were studied. According to the density functional theory calculations of the optimized resin molecules with the Fe⁰/Cu⁰ catalyst, the mechanisms of Fenton-like reactions and the degradation of mixed resins through the synergistic effect of Fe and Cu species were proposed. The comprehensive Fenton-like reactions and degradation mechanisms provide new insights to advance the treatment of spent resins and organic polymers by Fenton-like processes.