Purex Diluent Chemical Degradation

The chemical degradation of normal paraffin hydrocarbon (NPH) diluents both in the pure state and mixed with 30% tributyl phosphate (TBP) was investigated in a series of experiments. The results show that degradation of NPH in the TBP-NPH-HNO₃ system is consistent with the active chemical agent being a radical-like nitrogen dioxide (NO₂) molecule, not HNO₃ as such. Spectrophotometric, gas chromatographic, mass spectrographic, and titrimet-ric methods were used to identify the degradation products, which included alkane nitro and nitrite compounds, alcohols, unsaturated alcohols, nitro alcohols, nitro alkenes, ketones, and carboxylic acids. The degradation rate was found to increase with increases in the HNO₃ concentration and the temperature. The rate was decreased by argon sparging to remove NO₂ and by the addition of butanol, which probably acts as a NO₂ scavenger.