Screening of TODGA/TBP/OK solvent mixtures for the grouped extraction of actinides

Abstract

The solvent combination N,N,N'N'-tetraoctyl diglycolamide (TODGA)/tributyl phosphate (TBP)/odourless kerosene (OK) is examd. as a potential solvent system for a Grouped Actinide Extn. (GANEX) process to sep. all of the actinides from fission products when reprocessing spent nuclear fuel. A series of solvent extn. batch expts. were performed with a range of TODGA/TBP/OK solvent combinations to assess the sensitivity of distribution values for a no. of key elements towards [TBP] (0-1.1 M), [TODGA] (0.1-0.4 M), [HNO3] (0.1-5 M) and heavy metal loading ([U] 0-200 g/l). There is little impact on DAm or DEu across the solvent range and no influence from U loading. Excellent DNp values (>10) are obsd., increasing with increasing [TODGA], with [TBP] having little influence. Such high DNp values may obviate the need for preconditioning of dissolved fuel feeds to control Np routing. High DTc values are found even at 5 M HNO3, therefore Tc is expected to remain in the solvent phase. Both Pu(III) and Pu(IV) are readily extd. with DPu(III) > DPu(IV). Uranium is extd. by both TBP and TODGA and TBP is shown to effectively compete with TODGA for uranium coordination sites. Third phase formation occurs at high [U] loading and [HNO3] but is suppressed by increasing [TBP]. [on SciFinder(R)]