Nonphosphate Degradation Products of Tributyl Phosphate and Their Reactivities in Purex Media Under Extreme Conditions

The chemical degradation of tributyl phosphate (TBP) in liquid systems, where TBP was in contact with aqueous solutions containing nitric acid and/or uranyl nitrate, was studied experimentally to clarify the mechanisms of the formation and successive reactions of nonphosphate products under atmospheric pressure. Butyl nitrate, propionic acid, acetic acid, butric acid, and butyl alcohol were formed as the nonphosphate butyl products derived from the butyl-groups of TBP in an open system. The total amount of these products almost equals the amount of the major intermediate phosphate products reduced, i.e., di- and monobutyl phosphates and phosphoric acid. Butyl alcohol was found to be the precursor of the other nonphosphate products.

Even when the extremely degraded solvent was further contacted with 10 M nitric acid at 90°C, no significant heat evolution was observed at atmospheric pressure. Only butyl alcohol changed into carboxylic acids by exothermic oxidative reactions.