Thermo kinetic studies on chemical denitration of simulated waste solution

Abstract

Denitration of high level liquid waste (HLLW) generated during the aqueous reprocessing of spent fuels of nuclear reactors facilitates reduction of waste volume by evaporation and minimize corrosion in waste storage tanks. Chemical denitration of HLLW using formaldehyde results in the production of only gaseous products NOx, CO2, and H2O. The reaction between HNO3 and formaldehyde is exothermic and can lead to uncontrolled process conditions due to the induction period before starting the reaction and pressure development owing to the release of all gaseous products simultaneously. Reduction of HNO3 in the concentration range 1–4 M as well as a simulated waste solution by formaldehyde was investigated using an adiabatic calorimeter to measure the increase in pressure and temperature during the reaction, which are responsible for the unsafe process. Thermo-kinetic parameters such as the enthalpy change and activation energy were derived for the denitration reaction.