Abatement of the NOx Evolved during Denitration of Reprocessing Concentrate

In the treatment and solidification of medium and high level radioactive waste concentrates, large amounts of NOx are produced, which are normally scrubbed with nitric acid or alkaline solutions. In this way big volumes of secondary wastes containing high nitrate concentrations, which cannot be easily discharged, are obtained. The NOx catalytic abatement with selective ammonia reduction, which has been studied at the COMB/MEPIS-RIFIU Laboratory, would permit to avoid this problem, with large cost savings. The NOx catalytic abatement has been experimentally studied at laboratory scale taking into consideration the following operational parameters: the catalyst bed temperature; the gas residence time; the vapour concentration; the NOx concentration; the gas velocity; the catalyst grain size distribution; the catalyst time-life. The best operational conditions have been selected for obtaining abatement yields of the order of 99.5%.