Partitioning of mercury from actinides in the TRUEX process

A mercury complexant, L-cysteine hydrochloride, was tested for use in separating Hg(II) from actinides during transuranic extraction (TRUEX) processing of wastes at the Idaho National Engineering and Environmental Laboratory (INEEL). Mercury, americium, plutonium, and uranyl distributions for the TRUEX solvent were characterized over a nitric acid concentration range of 0.01 to 2M with and without cysteine. The applicability of cysteine was evaluated for selective Hg(II) complexation in an INEEL sodium-bearing waste simulant. A test was also conducted to evaluate the applicability of cysteine to separate Hg(II) from Sr in the strontium extraction (SREX) process with Sr Resin used as a stand-in for the SREX process solvent. In all cases, the use of L-cysteine HCl retained Hg in the aqueous phase while causing no or little perturbation in the actinide and Sr distribution behavior.