クロム・ターゲットよりイソプロピルエーテル抽出法による無担体52Feの放射化学的分離

秋葉 文正, 村上 悠紀雄

doi:10.2116/bunsekikagaku.20.1530

In connection with the practical production of ⁵²Fe formed by bombardment of ³He and α particles on natural chromium, the solvent extractions of carrierfree ⁵²Fe with isopropyl ether (IPE) and methylisobutyl ketone (MIBK) from chromium targets and other byproduced radioactive isotopes are investigated. The extractability and the separation conditions of Fe(III), V(IV), Cr (III) and Mn (II) from hydrochloric acid solution were examined in detail by use of ⁵⁹Fe, ⁴⁸V, ⁵¹Cr and ⁵⁴Mn tracers. The advantage and the disadvantage of both methods are discussed with giving considerations to high radiation level, rapidness and radiochemical purity. It was shown that the radicactive iron can be separated in carrier-free state from the chromium and others by isopropyl ether, which is superior to methyl-isobutyl ketone. In the production process, use was made of a natural chromium metal target of about 70×20×0.5 mm dimension electroplated on a copper block; after the electroplating, silver is also electroplated on the copper surface to get a target assembly from which the chromium is easily dissolvable into warm hydrochloric acid. Thus, by making use of remarkable difference of extractability of Fe(III) from that of V(IV), Cr(III) and Mn(II) in IPE, the extraction of ferric iron can be efficiently performed at the acidity of 8N hydrochloric acid solution. The separation seemed to be troublesome, because of the tendency of chromium to form passive state, but it was found that O₂-bubbling has a very large accelerating effect on the dissolution of the irradiated chromium. It is thought that the increase in the dissolution rate is probably due to not only the minor impurity formed in the chromium target in the course of the irradiation, but also the dissolution was carried out as it was plated on the copper surface. Extraction of the ⁵²Fe from the hydrochloric acid solution into isopropyl ether suits well for the remotecontrolled technique. The extracted ⁵²Fe is taken out from the remotehandling cell, then it is back-extracted into water and supplied to medical researches. The radiochemical purity of the ⁵²Fe extracted by the proposed method was proved to be satisfactory by the results of gamma-spectrometry and decay curve of ⁵²Fe.

クロム・ターゲットよりイソプロピルエーテル抽出法による無担体<SUP>52</SUP>Feの放射化学的分離

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