(450a) 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.