Thermoanalytical investigation of the reactions causing the transuranic waste drum breach that occurred in the Waste Isolation Pilot Plant

•Self-sustaining reactions between drum waste components start at room temperature.•Dry mixtures of nitric acid and wheat-based pet litter can lead to thermal runaway.•Hydrogen- and hydrogen-metal-triethanolamine nitrates react violently above 200°C.•Water inhibits low temperature reactions from self-accelerating to thermal runaway.•Lead nitrate reduces oxidation onset of nitric acid/wheat-based pet litter mixture.