Alternative design concepts for the electron to photon converter in the accelerator based production of technetium-99m

Abstract

The photonuclear production of radioisotopes using electron LINAC bremsstrahlung sources offers an industry alternative to reactor and ion beam production methods. One such method under development is the utilization of the Giant Dipole Resonance in the (y,n) reaction cross-section. This method is being studied for use in the production of 99mTc from enriched 100Mo by electron beam induced bremsstrahlung photons. Of primary concern to any radioisotope production system is the specific activity it is able to create of the radioisotope. In a photoneutronic production system maximizing the number of GDR photons on a given target increases the specific activity. Proper design and optimization of the electron-to-photon converter maximizes the number of GDR photons. This study examines some alternative types of converter design. MCNP is used to predict isotope yields and energy deposition in the converter assemblies and an Excel Spreadsheet is used to analyze the heat-transfer capabilities of the systems. Optimized designs are presented for the different types of converters studied. A radiantly cooled converter is presented as a low-yield design, while a circulating loop of molten lead is analyzed for use in a high-yield system.