New insight on the simultaneous H(2) and HNO(2) production in concentrated HNO(3) aqueous solutions under alpha radiation

Knowledge of hydrogen and nitrous acid yields (G(H(2)) and G(HNO(2))) from α radiolysis of nitric acid solutions is of critical importance for the technological aspects of reprocessing of spent nuclear fuel (SNF). This study provides critical information on the G values for external alpha irradiation of concentrated HNO(3) solutions. An investigation-specifically developed experimental setup allows performing this investigation without encountering issues related to extreme high local doses. In situ monitoring of the UV-visible induced absorption in irradiated HNO(3) solutions permitted quantification of HNO(2) production, and mass spectrometry was used to quantify H(2). The influence of the dose rate and HNO(3) concentration was investigated, and the primary yields of these two species were determined. It was found that dose rate increase leads to diminished production of HNO(2) and H(2), while HNO(3) concentration increase leads to increased HNO(2) formation and reduced H(2) production. The values of the primary yields of these two species were determined and compared to the literature reported values. While the determined values show similar trends as those reported, this study provides accurate radiolytic yields for H(2) and HNO(2) that are radioelement-independent compared to the α radiolysis using radioisotope/HNO(3) mixtures and provides the basis for perfecting numerical codes used for simulating the radiolytic processes associated with SNF reprocessing.