Thermo kinetic studies on chemical denitration of simulated waste solution. (April 2020)

• Record Type: Journal Article
• Authors: Mishra, Satyabrata; Chandran, K.; Lavanya, M.; Pandey, N.K.
• Is Part Of: Annals of nuclear energy. Volume 138(2020)
• Publication Date: 2020-04
• Subjects: Formaldehyde -- Nitric acid -- Denitration -- Enthalpy -- Activation energy; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2019.107198
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: Thermo-kinetics of HNO3 and HCHO reaction under various conditions was studied. Neat HCHO is stable up to 438 K followed by exothermic decomposition. Reaction of HCHO and simulated waste solution is more exothermic than HCHO and HNO3. Reaction of lower concentration of HNO3 with HCHO can lead to pressurization. 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 H2 O. 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.