Target manufacturing by Spark Plasma Sintering for efficient Zr production.

Zirconium-89 (Zr) is an emerging radionuclide for positron emission tomography (PET), with nuclear properties suitable for imaging slow biological processes in cellular targets. The Y(p,n)Zr nuclear reaction is commonly exploited as the main production route with medical cyclotrons accelerating low-energy (< 20 MeV) and low-current (< 100 μA) proton beams. Usually, natural yttrium solid targets manufactured by different methods, including yttrium electrodeposition, yttrium sputtering, compressed yttrium powders, and foils, were employed. In this study, the Spark Plasma Sintering (SPS) technique has been investigated, for the first time, to manufacture yttrium solid targets for an efficient Zr radionuclide yield. The natural yttrium disc was bonded to a niobium backing plate using a commercial SPS apparatus and a prototype machine assembled at the University of Pavia. The resulting targets were irradiated in a TR19 cyclotron with a 12 MeV proton beam at 50 μA. A dedicated dissolution module, obtained from a commercial system, was used to develop an automated process for the purification and recovery of the produced Zr radionuclide. The production yield and recovery efficiency were measured and compared to Zr produced by irradiating standard yttrium foils. SPS manufactured targets withstand an average heat power density of approximately 650 W∙cm for continuous irradiation up to 5 h without visible damage. A saturation yield of 14.12 ± 0.38 MBq/μAh was measured. The results showed that the obtained Zr production yield and quality were comparable to similar data obtained using standard yttrium foil targets. In conclusion, the present work demonstrates that the SPS technique might be a suitable technical manufacturing solution aimed at high-yield Zr radioisotope production.