Overview on the Application of Denitration in the Nuclear Field

In recent years varying emphasis has been dedicated to the denitration of high active waste (HAW) and medium active waste (MAW) solutions generated in the nuclear fuel cycle, particularly in fuel reprocessing. These solutions contain free nitric acid and considerable amounts of nitrate salts. Denitration can be performed either thermally or in solution by chemical means. Various organic reductants such as formic acid, formaldehyde and sugar have been successfully applied. Yet another alternative is electrolytic denitration.The main incentive of chemical denitration is reducing the acid content and in turn the salt load of the wastes formed by the neutralization of the acid with caustic soda. The ruthenium volatilization in the course of calcination and vitrification is also reduced. Further, the corrosion of waste storage tanks is minimized.Conflicting opinions exist on whether or not the benefits arising from a chemical denitration of HAW concentrates are worthwhile the extra expenditures required. In case of MAW conditioning the situation is different if an incorporation into an organic matrix, e.g. bitumen or platics, is foreseen. Safety considerations may well justify a pre-treatment step.