An automated flow system incorporating in-line acid dissolution of bismuth metal from a cyclotron irradiated target assembly for use in the isolation of astatine-211.

Astatine-211 (211 At) is a promising cyclotron-produced radionuclide being investigated for use in targeted alpha therapy. The wet chemical isolation of trace quantities of 211 At, produced within several grams of Bi metal deposited onto an aluminum cyclotron target assembly, involves a multi-step procedure. Because the 211 At isolation method is labor-intensive and complex, automation of the method is being developed to facilitate routine processing at the University of Washington and to make it easier to transfer the process to other institutions. As part of that automation effort, a module useful in the initial step of the isolation procedure, dissolution of the Bi target, was designed and tested. The computer-controlled module performs in-line dissolution of Bi metal from the target assembly using an enclosed target dissolution block, routing the resulting solubilized 211 At/Bi mixture to the subsequent process step. The primary parameters involved in Bi metal solubilization (influent HNO3 concentration and flow rate) were optimized prior to evaluation of the system using replicate 211 At-bearing cyclotron irradiated targets. The results indicate that the system performs in a predictable and reproducible manner, with cumulative Bi and 211 At recoveries following a sigmoidal function.