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oai:figshare.com:article/34037326 2026-10-01T00:12:54Z category_1 category_873 category_39 category_734 category_133 portal_63 item_type_6 month_year_10_2026

Gamma Radiolysis of Hydroxylamine in Aqueous Nitric Acid Solutions Jacy K. Conrad (13994563) Joseph R. Wilbanks (20766697) Gregory P. Horne (3336096) Biophysics Chemical Sciences not elsewhere classified Ecology Biological Sciences not elsewhere classified Plant Biology valuable predictive tool sup >+</ sup quantitatively accurate predictions primary degradation mechanisms dominant degradation product complete experimental dataset aminoxyl radical intermediate multiscale computer model model quantitatively reproduced deterministic kinetic model concentrated nitric acid solvent nitrate ions plutonium finishing operations validated multiscale model 3 </ sub 2 </ sub solutions containing nh plutonium finishing model uncertainty nitrous acid plutonium reductant water radiolysis structure simulations smaller amounts radiolytic loss radiation conditions principal source oxalate precipitation nitrous oxide molecular nitrogen latter exclusively initial concentration holding pu The radiolytic stability of hydroxylamine (NH₃OH⁺) in concentrated nitric acid (HNO₃) is directly relevant to plutonium finishing in used nuclear fuel reprocessing, where NH₃OH⁺ serves as both a plutonium reductant and nitrous acid (HNO₂) scavenger under high-radiation conditions. In this study, aqueous 1 M HNO₃ solutions containing NH₃OH⁺ were gamma irradiated to accumulated doses of up to 100 kGy. The radiolytic loss of NH₃OH⁺ was found to be independent of its initial concentration, pointing to its reaction with HNO₂ and hydroxyl (^•OH) and nitrate (NO₃^•) radicals as the primary degradation mechanisms. Nitrous oxide (N₂O) was the dominant degradation product, with smaller amounts of molecular nitrogen (N₂) and hydrogen (H₂)the latter exclusively from water radiolysis. A multiscale computer model was developed, combining stochastic radiation track-structure simulations with a deterministic kinetic model, and validated against the complete experimental dataset. The model quantitatively reproduced the radiolytic loss of solute NH₃OH⁺ and solvent nitrate ions (NO₃^–), and the evolution of N₂ and H₂. The N₂O yields, however, are determined by reactions of the aminoxyl radical intermediate (NH₂O^•), whose rate coefficients under strongly acidic conditions remain experimentally uncharacterized, representing the principal source of model uncertainty. Nevertheless, the presented model provides robust, quantitatively accurate predictions of NH₃OH⁺ stability under conditions relevant to plutonium finishing operations. Because maintaining a sufficient NH₃OH⁺ inventory is critical for holding Pu(III) prior to oxalate precipitation, the validated multiscale model is a valuable predictive tool that could be leveraged for process optimization within reprocessing flowsheets. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acs.jpca.6c04665.s001 https://figshare.com/articles/journal_contribution/Gamma_Radiolysis_of_Hydroxylamine_in_Aqueous_Nitric_Acid_Solutions/34037326 CC BY-NC 4.0