Modelling of Nitric and Nitrous Acid Chemistry for Solvent Extraction Purposes

As a first step in the overall objective of enhancing process models, the kinetic data for nitric acid decomposition reactions has been investigated in order to produce an initial dynamic model of decomposition under aqueous conditions. The identification of a set of kinetic reactions suitable for modelling has been the primary focus of this work. A model of nitric acid thermal decomposition will help develop a better understanding of nitric acid decomposition chemistry and enable better prediction of the oxidation states of species in solution. It is intended to later extend the model to include radiolytic reactions and then further to incorporate an organic phase in order to have a model which covers all decomposition routes for nitric acid within a nuclear fuel reprocessing scheme. The model will be used as a sub model for process models relating to nuclear fuel reprocessing to allow the nitric acid decomposition to be included and the effect of this on operations to be predicted. This is particularly relevant for models of maloperations where different fault scenarios can be investigated and the results of these predicted, as for example unusually high acidity could increase the yields of redox active species significantly altering actinide oxidation states.