The reaction of tri-n-butyl phosphate with nitrates

Laboratory experiments show that when tri-n-butyl phosphate is heated with nitric acid or metal nitrates, chemical reaction generates gas mixtures that can spontaneously ignite. In closed vessels, ignition of these gases was observed at gas phase temperatures of 184 to 264 degrees C, corresponding to liquid-phase temperatures of 158 to 225 degrees C. Pressures of fens of megapascals were measured. Several accidents associated with Purex processing in the nuclear industry appear to have been caused by ignition of the products of this reaction, either inside or outside process vessels. Safety measures involve controlling the temperature and providing adequate vents.