Spectroscopic Investigation of the Formation of Hypochlorite, Radiolysis By- Products in 5 M NaCl Featuring High-Energy Proton Beam Line Experiments

摘要

In the event of inundation of a nuclear waste repository located in a deeprngeological salt formation, chloride brines could contact waste and be exposed to radiationrnfrom the waste. The radiolysis of the chlorides brines via the α-radiation produced byrntransuranic wastes, which are mainly Pu, U, Am and Np, could lead to the formation of α-rnradiolysis by-products. Ionizing radiation affects the chemistry of aqueous solutions throughrnthe generation of free radical, ionic and molecular products such as hypochlorite (OCl-), andrnhypochlorous acid (HOCl). In the absence of reductants, hypochlorite could cause a highrnredox potential in the brine, which (1) may accelerate the dissolution of waste-forms, and (2)rnoxidize actinides. Therefore, the effect of radiolysis on high-saline brine are of particularrninterest because the presence of oxochlorides could influence the stability of Pu waste-forms.rnMeaningful predictions of long-term redox conditions in a nuclear repository strongly rely onrnestimations of G-values (number of molecules generated by 100 eV of radiation) of thernirradiation-induced formation of the oxidizers OCl- and HOCl. G-values not only depend onrnthe total absorbed doses over the relevant timeframe, but also on the kind of irradiationrninvolved. To overcome the serious constraints and obstacles of conventional radiochemicalrnwork with Curie activity levels, we are simulating α-irradiation of chloride brines by thernadaptation of beam-line experiments.rnOur long-term goal is to determine whether the main oxidizing chloride species such asrnhypochlorite caused by radiolysis may affect the overall behavior of actinides under saltrnrepository conditions by oxidizing Pu(III/IV) to Pu(V/VI). This paper describes our first stepsrntowards the production, the identification and the determination of these oxidizing species byrnbeam line experiments.