Extraction studies of gadolinium relevant to its use as neutron poison in the PUREX process

The extraction behavior of gadolinium into tri-n-butyl phosphate (TBP) (0.37-1.1M) in n-dodecane (n-DD) as diluent from different concentrations of nitric acid (1-13.5M) has been systematically investigated to establish the feasibility of using gadolinium as soluble neutron poison for ensuring nuclear criticality safety during the processing of FBR spent fuel containing higher concentrations of fissile material. The effect of acidity, temperature, metal loading and gadolinium concentration on the distribution co-efficient of Gd(III) are established. The obtained results clearly indicate the feasibility to decontaminate Gd(III) under typical FBR fuel reprocessing conditions thereby enabling to qualify the final product to be pure from the point of view of nuclear poison impurity.