Deuteron irradiation of W and WO3 for production of high specific activity 186Re: Challenges associated with thick target preparation

This investigation evaluated target fabrication and beam parameters for scale-up production of high specific activity Re-186 using deuteron irradiation of enriched W-186 via the W-186(d,2n)Re-186 reaction. Thick W and WO3 targets were prepared, characterized and evaluated in deuteron irradiations. Full-thickness targets, as determined using SRIM, were prepared by uniaxially pressing powdered natural abundance W and WO3, or 96.86% enriched W-186, into Al target supports. Alternatively, thick targets were prepared by pressing W-186 between two layers of graphite powder or by placing pre-sintered (1105 degrees C, 12 h) natural abundance WO3 pellets into an Al target support. Assessments of structural integrity were made on each target prepared. Prior to irradiation, material composition analyses were conducted using SEM, XRD, and Raman spectroscopy. Within a minimum of 24 h post irradiation, gamma-ray spectroscopy was performed on all targets to assess production yields and radionuclidic byproducts. Problems were encountered with the structural integrity of some pressed W and WO3 pellets before and during irradiation, and target material characterization results could be correlated with the structural integrity of the pressed target pellets. Under the conditions studied, the findings suggest that all WO3 targets prepared and studied were unacceptable. By contrast, W-186 metal was found to be a viable target material for Re-186 production. Thick targets prepared with powdered W-186 pressed between layers of graphite provided a particularly robust target configuration. (C) 2016 Elsevier Ltd. All rights reserved.