Production of the positron emitter 51Mn via the 50Cr(d, n) reaction: targetry and separation of no-carrier-added radiomanganese

Abstract

Summary In connection with the production of 46.2 min 51Mn via the 50Cr(d, n)-process, several separation techniques such as ion exchange chromatography, solid phase extraction, liquid–liquid extraction and co-precipitation have been investigated; the aim was to separate no-carrier-added radiomanganese from the bulk target chromium. Among the separation systems *MnII/CrIII, *MnII/CrVI and *MnIV/CrVI, the latter applying the co-precipitation of *MnIV with FeIII hydroxide was found to be the optimum; the removal of chromium was rapid and quantitative (remaining content <0.05%) and the separation efficiency was high (99.3% radiochemical yield of *Mn). For production purposes, a sandwiched pellet of the chemical composition Al4·50CrCl3 was developed as a new target. This allowed a quick dissolution after irradiation, thus enabling a fast separation of 51Mn and its production on a MBq scale. A 1 h irradiation at 3 µA (wobbled beam) over an effective deuteron energy range of E d = 12.8 → 7.9 MeV yielded 107 MBq 51Mn. Simultaneously formed nuclides of other elements, such as 38Cl, 24Na, 48V and 51Cr were quantitatively separated using the proposed procedure. Only the shorter-lived radioisotope 52mMn, formed via the 52Cr(d, 2n)52mMn reaction, was present at a low level of 2%, if the enrichment of 50Cr was 95% (with ∼5% 52Cr).