A proportion of 30 wt % of tributyl phosphate (TBP) in suitable diluents is the workhorse in the extraction of U and Pu in the plutonium uranium extraction (PUREX) process. Accelerating rate calorimetric (ARC) studies of effects of diluents on TBP behavior reveal a similar thermal behavior irrespective of the nature of diluents. The reactive thermal hazards of 30 wt % of TBP with 4N HNO 3 in different diluents show onset temperatures in the range of 105−130°C with a significant pressure rise. Although the onset points are closer to the operating temperature range of the PUREX process, the heat rates are small. However, the process poses pressurization hazards due to the breakdown of the structure of TBP. Oxidation of butanol to butanoic acid is the main cause for exothermic behavior in all cases.

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