Bounding the Chemistry Conditions in the HM Solvent Extraction Process Criticality Safety Analyses

An approach new to the H-Canyon facility criticality safety analysis has been performed using highly detailed models of the H-Modified process mixer settlers. The HM process uses tributyl phosphate (TBP) in organic n-paraffin to extract and purify uranium from used nuclear fuel. This occurs in two cycles of counter-current solvent extraction. The aqueous stream is a weak to moderate nitric acid and the feed stock is an aqueous stream. The 1st Cycle, consisting of two 16-stage banks (A and B-Banks) and one 12-stage bank (C-Bank), is a three step process that separates uranium from the fuel matrix, fission products, and most of the transuranic actinide content. The 1^st Cycle aqueous product is concentrated, adjusted for acidity and fed to the 2^nd Cycle. The 2^nd Cycle, consisting of one 16-stage bank (D-Bank) and one 12-stage bank (E-Bank), is a two step process that further purifies the uranium and removes to a great extent remaining actinides and fission products.