Pyrophoric potential of plutonium-containing salt residues

Ignition temperatures of plutonium and the pyrophoric potential of plutoniu m-containing pyrochemical salt residues are determined from differential th ermal analysis (DTA) data and by modeling of thermal behavior. Exotherms ob served at 90-200 degrees C for about 30% of the residues are attributed to reaction of plutonium with water from decomposition of hydrated salts. Exot herms observed near 300 degrees C are consistent with ignition of metal par ticles embedded in the salt. Onset of self-sustained reaction at temperatur es as low as 90 degrees C is not precluded by these results and heat-balanc e models are developed and applied in predicting the static ignition point of massive metal and in evaluating salt pyrophoricity. Results show that am bient temperatures in excess of 200 degrees C are required for ignition of salt residues and that the most reactive salts cannot ignite at low tempera tures because diffusion of oxidant to embedded metal is limited by low salt porosity. (C) 2000 Elsevier Science B.V. All rights reserved.