title: Experimental study on thermal hazard of tributyl phosphate-nitric acid mixtures using micro calorimeter technique.
abstract: 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.
authors.affiliation: State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, Anhui, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, Anhui, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, Anhui, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Gong
authors.affiliation: State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, Anhui, China. Electronic address: sunjh@ustc.edu.cn.
authors.forename: Jin-Hua
authors.initials: JH
authors.lastname: Sun
keywords: Activation energy; Red oil; Spent fuel reprocessing; Thermodynamics; Tributyl phosphate