Coupled effects of initial temperature and sub-atmospheric pressure on the flammability limits and explosion characteristics of Tributyl Phosphate/kerosene mixtures

TBP/kerosene mixtures are vital extraction solvents in nuclear fuel reprocessing, yet their explosion characteristics under coupled high temperature and sub-atmospheric pressure are poorly understood. This study experimentally investigated the flammability limits and explosion intensities of these vapor mixtures at 60°C and 120°C (75–100 kPa, 0.75 bar-1.0 bar). Results show that reducing initial pressure significantly suppresses explosion intensity and narrows the flammable range. At 120°C, the explosive range (1.0%–11.0% at 100 kPa) converges to a singular critical point (3.5% at 75 kPa); when at 60°C, the critical pressure threshold rises to 95 kPa. The maximum explosion pressure consistently occurred at a stoichiometric concentration of 7.0%. Sensitivity analysis indicates the upper flammability limit is more pressure-sensitive than the lower flammability limit at 120°C, driven by reduced molecular collision frequency and oxygen limitation in fuel-rich zones. These findings provide essential thermodynamic data for safety design and risk assessment in nuclear chemical facilities under extreme conditions.