Hot zone formation in combustion tests simulating solvent fires in reprocessing plants – concerns on boilover phenomenon

This paper reports the first case of hot zone formation in a combustion test simulating an organic solvent fire in a reprocessing plant. Our goal is to add a boilover component to a computational model for quantitatively predicting the accident progression of the fire. Although the scale of boilover combustion increases when hot zones are formed in the solvent, it has not been clarified whether a hot zone is formed in the combustion of a 30% tributyl phosphate (TBP)/dodecane solvent mixture. To clarify this point, we conducted beaker-scale combustion tests and measured the temperature distribution in the burning solvent with thermocouples to obtain the following results. (1) No hot zone was formed by the combustion of only dodecane. (2) In the combustion of 30% TBP/dodecane, hot zones were not formed as long as dodecane remained in the solvent. (3) A hot zone was formed when only TBP was burned. These results suggest that boilover combustion with hot zones may occur in the case of a fire caused by the leakage of organic solvents with nitric acid solution in a reprocessing plant.