Pyrophoric potential of plutonium-containing salt residues

Abstract Ignition temperatures of plutonium and the pyrophoric potential of plutonium-containing pyrochemical salt residues are determined from differential thermal analysis (DTA) data and by modeling of thermal behavior. Exotherms observed at 90–200°C for about 30% of the residues are attributed to reaction of plutonium with water from decomposition of hydrated salts. Exotherms observed near 300°C are consistent with ignition of metal particles embedded in the salt. Onset of self-sustained reaction at temperatures as low as 90°C is not precluded by these results and heat-balance models are developed and applied in predicting the static ignition point of massive metal and in evaluating salt pyrophoricity. Results show that ambient temperatures in excess of 200°C are required for ignition of salt residues and that the most reactive salts cannot ignite at low temperatures because diffusion of oxidant to embedded metal is limited by low salt porosity.