TECHN-OSP: Molybdenum target preparation techniques for cyclotron-based technetium-99m production

Cyclotron-based production of Technetium-99m by 100Mo(p,2n)99mTc reaction has been developed in the framework of TECHN-OSP project financed by CSN5 of INFN. Molybdenum-100 enriched target design and preparation is one of the most critical technological challenges in cyclotron production of Technetium- 99m. During TECHN-OSP project a set of standard (hydraulic manual pressing, pressing forwarded by sintering) and also non- classical techniques for metallic target preparation, like magnetron sputtering, HIgh energy Vibration Powders Plating (HIVIPP) and Spark Plasma Sintering (SPS) have been studied. It was developed a cyclotron solid target prototype composed of Mo sputtered layer onto complex backing plate, consisted of synthetic diamond brazed to copper. Such composite backing plate guarantees chemical inertness in target dissolution media (concentrated hydrogen peroxide) due to synthetic diamond and also high thermal performance (>1 kW/cm2) due to high thermal conductivity materials used and good thermal contact provided by brazing in vacuum. The HIVIPP [3] electrostatic deposition was applied here for Mo with >95% deposition efficiency and high uniformity. The trials of Mo HIVIPP deposition provided small thickness (2-3 m) that for the moment is limiting the use of HIVIPP for Technetium-99m production target preparation. However, further development of the technique in direction of thickness increase is planned in the framework of new CSN5 INFN project E-PLATE (Electrostatic Powders pLating for Accelerator TarEts) in 2018-2019. In order to decrease the costs of cyclotron-based production of Technetium-99m, a method to recover expensive Molybdenum-100 from separation module Mo-rich waste in metallic form with efficiency about 90% was developed.