Bulk Production of Generator Parent 72se At the Los Alamos IPF Using a NaBr Target

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.