Conclusions and Opinion of the Scientific Secretaries

Basically denitration of radioactive liquid waste is performed batchwise by feeding formic acid or formaldehyde into a nitric waste solution at boiling temperature or vice-versa. Although sugar and ethanol have been proposed as alternatives, their respective advantages over formic acid and formaldehyde (lower cost for sugar and better efficiency for ethanol) do not appear, in most cases high enough to counteract their inherent drawbacks (longer reaction time for sugar and high flammability in case of ethanol). The only application for which sugar is definitely superior deals with denitration of high level waste during vitrification (in the rotary kiln according to the AVM process) which enables a significant reduction of Ru and Tc volatilities. However, for all the other applications, so far, formic acid and formaldehyde remain the most suitable reagents for denitrating adioactive liquid waste.