Preparation of Promethium-147 Beta-ray Sources with Curie Level Intensities by Means of Electrodeposition

Abstract

The preparation of promethium-147 beta-ray sources with curie level intensities by electrodeposition from non-aqueous solutions is described. As the elements chemically analogous to promethium, samarium and neodymium were used to find the best conditions for producing uniform and adhering layers.
Experience has shown that isopropyl alcohol was favourable as a organic solvent because of the absence of its moisture. Layers electrodeposited from alcohol with a high water content were very powdery and had poor adhesion to the backing. Therefore, the solution for electrodeposition was prepared by adding about 100μl of aqueous solution of the chloride of neodymium or samarium to 20 ml of isopropyl alcohol, or by dissolving those nitrates with same volume of isopropyl alcohol. The concentrations of the materials to be electrodeposited were 200μg/ml. After shaking well all volume of the solution was put in an electrodeposition cell. A platinum wire in the form of a spiral was used as anode. As backing materials, aluminium and stainless steel plates were found to be more favourable than platinum plate from the point of view of the adhesion of electrodeposited layer to those materials. It was derirable to arrange the current density as low as possible because excess current resulted in a less adherent layer. However, current density of more than 120, tA/cm² was required for producing uniform and adhering layers. From the data of thermal analysis, it was concluded that the chemical form of electrodeposited layer was hydroxide. This layer was converted to oxide by heating the backing with the layer at temperatures above 600°C, and hence, more excellent adhesion of the layer was realized in the form of oxide. In case of samarium, a deposited layer of 0.6 mg/cm² (0.5 Ci/cm² calculated in terms of the radioactivity of promethium-147) was obtained in the form of Sm₂O₃ at a time. Thicker layer can be produced by repeating the electrodeposition after heating the backing with the layer. Similarly, promethium of activity 790 mCi per 5.1 cm² was also electrodeposited successfully with a carrier of neodymium of 3.0 mg. The yield of electroposition was 98% for the electrolysis of 16 hours at a current density of 200μA/cm². The sources prejared in this manner are suitable for a wide range of apjlications.