Homogenous recycling of transuranium elements from irradiated fast reactor fuel by the EURO-GANEX solvent extraction process

Abstract

Abstract The EURO-GANEX process was developed for co-separating transuranium elements from irradiated nuclear fuels. A hot flow-sheet trial was performed in a counter-current centrifugal contactor setup, using a genuine high active feed solution. Irradiated mixed (carbide, nitride) U80Pu20 fast reactor fuel containing 20 % Pu was thermally treated to oxidise it to the oxide form which was then dissolved in HNO3. From this solution uranium was separated to >99.9 % in a primary solvent extraction cycle using 1.0 mol/L DEHiBA (N,N-di(2-ethylhexyl)isobutyramide in TPH (hydrogenated tetrapropene) as the organic phase. The raffinate solution from this process, containing 10 g/L Pu, was further processed in a second cycle of solvent extraction. In this EURO-GANEX flow-sheet, TRU and fission product lanthanides were firstly co-extracted into a solvent composed of 0.2 mol/L TODGA (N,N,N′,N′-tetra-n-octyl diglycolamide) and 0.5 mol/L DMDOHEMA (N,N′-dimethyl-N,N′-dioctyl-2-(2-hexyloxy-ethyl) malonamide) dissolved in Exxsol D80, separating them from most other fission and corrosion products. Subsequently, the TRU were selectively stripped from the collected loaded solvent using a solution containing 0.055 mol/L SO3-Ph-BTP (2,6-bis(5,6-di(3-sulphophenyl)-1,2,4-triazin-3-yl)pyridine tetrasodium salt) and 1 mol/L AHA (acetohydroxamic acid) in 0.5 mol/L HNO3; lanthanides were finally stripped using 0.01 mol/L HNO3. Approximately 99.9 % of the TRU and less than 0.1 % of the lanthanides were found in the product solution, which also contained the major fractions of Zr and Mo.