The number of nitrates and organics present in the feed for nuclear waste processing directly coincides with the amount of NOx emissions generated. A reduction of nitrates and nitrites in nuclear waste will directly reduce emissions produced from the vitrification process and will help to ease some processing constraints in the facility. A modular electrochemical denitration system is proposed as a potential aid to accelerate the processing of nuclear waste at the Hanford site. In order to develop an engineering-scale electrochemical processing skid for the denitration (removal of nitrate and nitrite anions) of Hanford tank waste, small scale experiments are necessary and were performed to optimize electrochemical performance of the denitration electrolyzer.
In this case, the electrochemical nitrate reduction reaction (NO3RR) is utilized to remove nitrate and nitrite from simulated alkaline tank waste supernate. Outside the field of nuclear waste processing, the NO3RR has had a recent renewed interest as an less energy intensive ammonia production scheme. Lessons learned from this study may prove to be viable in both fields of research.
This paper explores aspects of performing bench-scale experiments with an intent to develop a full-scale modular system for implementation. Focus on the influence of electrolyte composition and electrode material performance will be shown. Conversion products and efficiency were determined through in-situ liquid phase Raman spectroscopy and mass spectrometry. The chemical conversion was further confirmed through the quantification of the resulting solutions via ion chromatography and pH measurements. The NO3RR show promise for treating nuclear waste tank supernate.
