Scale-up and optimization of a two-stage molten salt oxidation reactor system for the treatment of cation exchange resins

A prototype two-stage MSO (molten salt oxidation) reactor system with a capacity of 10 kg/h was developed based on the test results of lab-scale and bench-scale MSO systems. This study first discusses the features of the prototype MSO reactor system. The second part of the study attempts to identify the proper conditions of the prototype two-stage MSO reactor system, where each reactor performs different functions. The volatility of radioactive elements doped in the spent resins was first investigated to establish the proper operating conditions of the primary MSO reactor. A parametric model study of the secondary MSO reactor for the oxidation of hydrocarbons from the primary reactor and an experimental validation were then performed to establish the optimum conditions for the two-stage MSO reactor system. The retention of cesium was greatly influenced by the pyrolysis temperature. The highest pyrolysis temperature with cesium retention of ≥99.9% was 790 °C and this was established as the optimum primary reactor temperature. The optimum conditions of secondary MSO reactor for the substantial oxidation of hydrocarbons generated from the primary MSO reactor were determined to be λ (the ratio of actual air feed rate per stoichiometric air rate) of 2, and a temperature of 800 °C.