Preparation of thorium alpha source using electrodeposition method

Thorium isotopic ratio can be used for the age determination of uranium ore concentrate (yellow cake). The longer-lived naturally occurring isotopes of thorium are alpha emitters, so the technique of alpha spectrometry can be used to quantify them directly. This work describes the alpha source preparation of thorium by electrodeposition method suitable for thorium isotopic analysis of yellow cake by alpha spectrometry. The purpose of this study is to obtain the optimum electrodeposition parameters in order to get accurate isotopic analysis results. Materials used were uranium and thorium certified standards, and sodium acetate as electrolyte solution. Thorium was electrodeposited onto stainless steel discs (as cathode) using a modified cell with platinum wire as anode. The optimum condition of electrodeposition process was determined by observing the effect of sodium acetate concentration, electric current and deposition time. Effect of pH and the presence of uranium were also studied in order to observe the influence of an incomplete acid and uranium removal on the thorium purification process. The result showed that the highest recovery of the electrodeposited thorium was obtained at 1 M sodium acetate concentration with 0.4 A of current, in 105 minutes deposition time. This optimum condition was chosen for the electrodeposition process conducted in our electrodeposition cell. The more nitric acid left in the residue of thorium effluent solution, the lower pH of electrolyte solution and the smaller area of thorium deposits was formed. The more uranium left in the effluent solution, the thicker yellow layer was formed and causes the absorption effect.