Preparation of inorganic forms and interhalogen compounds of 211At via distillation techniques

Extractive and dry evaporation techniques are reported for the routine production of inorganic forms of the radioisotope 211At from α-irradiated Bi-metal foils. Both the methods, take about the same time for preparation of the simple inorganic At forms. The yields are comparable. There is a slight preference for the wet technique in routine processing of Bi-targets with low specific activity. The dry evaporation methods seem to be more appropriate for higher specific activities and for preparations under exclusions of water, such as in the case of the interhalogens AtX. At-, At0 and At+ as well as the interhalogen compounds AtCl, AtBr, AtI and AtCl2, AtBr2-, AtI2- are prepared in radiochemically (but not biologically) pure forms with yields ranging from 50 to 70%. 211At is produced via the 209Bi(α,2n)211At nuclear reaction at the isochronous cyclotron of the GfK Karlsruhe. The targets consist of 200 μm thick foils of Bi-metal and are backed by 500 μm thick copper foils. They are irradiated in the internal beam facility with 28 to 30 MeV α-particles at a current of about 20 μA. The Bi-target is protected from melting by almostan almost 4PI-water cooling system with a cooling efficiency, of 50kWcm-2. A 6h irradiation leads to about 50mCi 211At. (T.I.)