PRELIMINARY PRODUCTION OF 211At AT THE TEXAS A&M UNIVERSITY CYCLOTRON INSTITUTE

A feasibility study for the production of the alpha particle-emitting radionuclide At-211 was performed at the Texas A&M University Cyclotron Institute as part of the Interdisciplinary Radioisotope Production and Radiochemistry Program. The mission of this program centers upon the production of radionuclides for use in diagnostic and therapeutic nuclear medicine with the primary focus on development of novel therapeutic strategies. As a first step in establishing this program, two goals were outlined: (i) verify production of At-211 and compare results to published data, and (ii) evaluate shielding and radiological safety issues for large-scale implementation using an external target. The radionuclide At-211 was produced via the Bi-209 (alpha, 2n) At-211 reaction using the K500 cyclotron. Two experiments were conducted, using beam energies of 27.8 MeV and 25.3 MeV, respectively. The resulting yields for At-211 were found to be 36.0 MBq mu A(-1) h(-1) and 12.4 MBq mu A(-1) h(-1), respectively, which fall within the range of published yield data. Strategies for increasing absolute yield and production efficiency were also evaluated, which focused chiefly on using a new target designed for use with the K150 cyclotron, which will enable the use of a higher beam current. Finally, neutron and gamma dose rates during production were evaluated by using the Monte Carlo code MCNPX. It was determined that a simple structure consisting of 4-in thick borated polyethylene will reduce the neutron dose rate within the cyclotron production vault by approximately a factor of 2, thereby decreasing activation of equipment.