Generator radionuclides constitute a convenient tool for applications in nuclear medicine. Arsenic-72 (half life 26 h) is a medium-lived positron emitting radionuclide for PET imaging that can be produced as a daughter of 72Se (half life 8.5 d). A 72Se/72As generator system would be suitable for hospital on-site utilization. No portable 72Se/72As generator system is available on the market for convenient, repeated 72As elution at the point of care (“milking”). Radionuclide generator principles for 72Se/72As have been proposed in the literature, including repeated distillation of “grown-in” 72AsCl3 from carrier added 72Se stock solutions, electroplating of 72Se as Cu2Se on Cu backings, and solid phase extraction of 72Se. We describe a 72Se/72As generator system analogous to a well-developed commercial 82Sr/82Rb generator system.
Production of the parent 72Se via 90 MeV proton bombardment of a natural NaBr target has been successfully demonstrated at the Los Alamos National Laboratory’s Isotope Production Facility (LANL-IPF) following a thorough target safety analysis for high beam currents.
Safety analysis included a high intensity beam thermal study and product nuclide estimates utilizing Monte Carlo code MCNPX. The thermal study illustrated the high thermal stability with good thermal contact being maintained throughout the irradiation, results will be presented. The 72Se from proton irradiated NaBr targets was chemically recovered at the LANL Hot Cell Facility in good yield (94%). Good agreement of theoretical thick yields and experimental results were obtained. Batch recovery of 72As via liquid-liquid extraction was also effective at 76% yield, with minimal breakthrough of the 72Se parent (0.9%). Moreover, the feasibility of a solid phase generator system will be discussed.
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