TRUEX Radiolysis Testing Using the INL Radiolysis Test Loop: FY-2012 Status Report

Abstract

SUMMARYThis report presents a summary of the work performed to meet the FCRD level 3 milestone M3FT-12IN0302032, "TRUEX strip/TALSPEAK feed degradation mechanism." The INL radiolysis test loop has been used to evaluate the effects of radiolytic degradation upon the efficacy of the strip section of the TRUEX flowsheet for the recovery of trivalent actinides and lanthanides from acidic solution. The nominal composition of the TRUEX solvent used in this study is 0.2 M CMPO and 1.4 M TBP dissolved in n-dodecane and the nominal composition of the TRUEX strip solution is 1.5 M lactic acid and 0.050 M diethylenetriaminepentaacetic acid. Gamma irradiation of a mixture of TRUEX process solvent and stripping solution in the test loop does not adversely impact flowsheet performance as measured by stripping americium ratios. The observed increase in americium stripping distribution ratios with increasing absorbed dose indicates the radiolytic production of organic soluble degradation compounds. While the observed increases in the americium stripping distributions with increasing absorbed dose are statistically significant, the increase from D Am = <0.001 at 0 kGy absorbed dose to D Am = 0.015 at 1300 kGy absorbed dose is not an insurmountable difficulty. A more troubling observation is the significant decrease in the solvent dispersion number as the strip section of the TRUEX flowsheet is subjected to gamma radiolysis. The dispersion number, N Di , determined for un-irradiated TRUEX solvent and strip solution is N Di = 1.05 x 10 -3 , which is an acceptable value for typical solvent extraction equipment. However, the dispersion number for the irradiated TRUEX solvent and strip solution is 3.94 x 10 -4 , which is a poor value for typical solvent extraction equipment. Dispersion number determinations for mixture of irradiated and un-irradiated solutions suggest that both the aqueous and organic phases play a role in the decrease of the solvent dispersion number.