Gamma Radiolysis of Hydroxylamine in Aqueous Nitric Acid Solutions

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.