Research Progress of Red Oil Explosion Accidents in Nuclear Fuel Reprocessing Plant

From 1953 to now, it has happened six times so-called red oil explosion accidents worldwide, resulting in different degrees of equipment and construction damage and environmental contamination. And research related to red oil has never stopped. Preventive measures for red oil explosion were established in some reports, and these measures provided good practice experience and reference for other countries. Nevertheless, research conclusions and knowledge of red oil vary from country to country. Especially, investigations on stability of tributyl phosphate (TBP)—nitric system was made in recent years, and the results indicated that the red oil runway reaction will happen even in lower temperature and lower nitric acid concentration in contrast with the reported value. Therefore, in order to facilitate future study on red oil explosion, related research results of red oil explosion accidents were combed in this paper, and the characters of study work of different periods were also summarized, and definition, formation conditions of red oil were analyzed and compared, as well as the new viewpoints of recent literatures.

Experimental study on thermal hazard of tributyl phosphate-nitric acid mixtures using micro calorimeter technique

During PUREX spent nuclear fuel reprocessing, mixture of tributyl phosphate (TBP) and hydrocarbon solvent are employed as organic solvent to extract uranium in consideration of radiation contaminated safety and resource recycling, meanwhile nitric acid is utilized to dissolve the spent fuel into small pieces. However, once TBP contacts with nitric acid or nitrates above 130°C, a heavy "red oil" layer would occur accompanied by thermal runaway reactions, even caused several nuclear safety accident. Considering nitric acid volatility and weak exothermic detection, C80micro calorimeter technique was used in this study to investigate thermal decomposition of TBP mixed with nitric acid. Results show that the concentration of nitric acid greatly influences thermal hazard of the system by direct reactions. Even with a low heating rate, if the concentration of nitric acid increases due to evaporation of water or improper operations, thermal runaway in the closed system could start at a low temperature.