Explosion and fire during conversion of liquid uranyl nitrate to solid uranium oxide

During the conversion of molten uranyl nitrate to solid uranium oxide at the Savannah River Plant, a rapid chemical reaction occurred in a denitrator and expelled the contents, including combustible gases, into the process room. The gases ignited and caused a gas-phase explosion and fire. An excessive amount of organic material (approximately 120 liters of tributyl phosphate in the form of uranyl nitrate adduct) had been unintentionally transferred, along with normal process material, through two evaporators to the denitrator. During heating of the denitrator contents, the organic material decomposed rapidly between 170 and 210/sup 0/C, emitting combustible and noncombustible gases that ejected the denitrator contents into the denitrator room. The gas collected at the ceiling in the room and ignited with a low explosive force. Two employees sustained minor injuries, and there was about $230,000 damage to the building and equipment.