[en] Criticality is a major challenging issue to be addressed at each stage of reprocessing of spent fuel has high rich plutonium from Fast Breeder Test Reactor is carried out by modified PUREX process. Generally, the safety measures are taken to prevent the criticality incident, either by controlling geometry of equipment, mass or concentration of plutonium or combination of both may also used. Alternatively, addition of soluble neutron poisons as a primary control has economic advantage as it has no restriction on vessel size, shape and solution concentrations. Among the few potential candidates, gadolinium or samarium is found to be the best possible choice as soluble neutron poison due to its high neutron absorption cross section, adequately high solubility in nitric acid and chemical compatibility in the PUREX solvent extraction process conditions. Hence, its extraction behaviour into tri-n-butyl phosphate (TBP) and Tri iso-amyl phosphate (TiAP) in n-dodecane solvent is investigated in the present study. Batch experiments were carried out by equilibrating equal volumes of 1.1M TBP in nDD with samarium nitrate solution is stopped centrifuged vial for effective mixing using a vortex shaker at a speed of 1700 rpm for 30 minutes. Both phases were allowed to disengage completely. After separation, the acidity and samarium concentration were estimated with appropriate dilution if necessary. The distribution coefficient of samarium was determined by the ratio of concentration of samarium in organic to aqueous phase at equilibrium. Data are presented on the effect of various influencing parameters such as concentration of metal ion, concentration of extractant, acidity, interference ion and temperature on the distribution of samarium between nitric acid and tributyl phosphate-diluent phases under Fast reactor spent fuel reprocessing plant conditions. The results indicate the feasibility of samarium decontamination under typical Purex process conditions. DSm versus different concentration samarium and temperature are represented. The obtained results are compared with 1.1 M TiAP at similar experimental conditions. (author)