Introduction Technetium-99m, the daughter of 99Mo is the most commonly used radioisotope in nuclear medicine [1–2]. Current global crisis of 99Mo supply, aging of nuclear reactors and staggering costs force the search for alternative sources of 99mTc. Radioisotope Centre POLATOM joined the IAEA Coordinated Research Project on “Accelerator-based Alternatives to Non-HEU Production of 99Mo/99mTc”. The planned outcome of this project is development of 99mTc production method using the reaction of 100Mo(p,2n)99mTc [3] in Polish cyclotron. This work presents the results concerning preparation of 100Mo target for irradiation with protons. Material and Methods The manufacturing of Mo target was performed using pressing of molybdenum powder into pellets and its sintering in hydrogen atmosphere at 1600 oC [4]. For this purpose a tantalum and stainless steel plates were used as support. Several pellets using molybdenum powder with particles size of 2 µm in diameter were pressed at different values of pressure. Results and Conclusion The optimized parameters of pressing molyb-denum pellets with various sizes are given in TABLE 1. It was found that the pellets did not adhere neither to the tantalum nor stainless steel plates but they conducted electricity very well. Pellets prepared with higher pressure were more mechanically resistant, however application, even the highest used pressure did not ensure its satisfactory stability. In order to improve mechanical strength, pressed Mo pellets were sintered in hydrogen atmosphere at temperature of 1600 °C. As a result of this process dimensions of Mo pellets decreased: diameter by 13 %, thickness by 12 %, weight by 1.5 %, volume by 34 % while density increased by 50 %. The changes of these parameters are associated with reduction of molybdenum oxide and removal of oxygen from intermetallic space. It was confirmed by photos of microscopic cross section of pellets before and after sintering. It was observed, that after sintering Mo pellets got a metallic form with very high hardness and mechanical strength.

Introduction 100Mo target design is key to commercially viable large scale cyclotron production of 99mTc. The target back plate supporting the 100Mo must be chemically inert to the target dissolution conditions but ideally it should also be able to dissipate the high thermal loads of irradiation, not contaminate target substrate with radionuclidic by-products, and be adequately inexpensive to allow for single use. Aluminum was selected as our target support as it satisfies these requirements. Our process entails rolling 100Mo powder into a foil of desired thickness, and then diffusion bonding [1] the foil onto an aluminum back plate. The 100Mo targets were designed to be 20×80×0.1 mm to match our TR24 cyclotron’s proton beam profile and energy. Efforts are currently underway to scale up the process to allow for simultaneous production of multiple targets at once. Material and Methods The crude enriched 100Mo foil (99.815% enrichment) was made from 100Mo powder using a horizontally mounted rolling mill and an aluminum hopper. The crude foil was rolled repeated-ly, and the space between the rollers gradually reduced until the thickness of the foil was changed from an initial thickness of 0.3 mm to a thickness of 0.1 mm. The rolled 100Mo foil was annealed under reducing atmosphere and then bonded to the aluminum target plate support under inert atmosphere in a heated press at 500 °C. Results and Conclusion By rolling 100Mo foils from powder we were able to produce uniform foils with an average density of > 98 % compared to the maximum theoretical density of 100Mo (n = 5) and thicknesses of roughly 0.1 mm. All foils produced were the desired 20 mm width (i.e. limited by the width of the opening of the hopper) and trimmed to the desired 80 mm length. The annealing process was necessary due to the brittleness of the un-annealed rolled foil and the difference in the thermal expansion coefficients of molybdenum and aluminum which caused un-annealed foils in previous experiments to crack and break off during pressing (n = 10). Surface preparation of the aluminum support plate was also found to play a critical step in the efficiency of the bond, and continuing effort to scale the above de-scribed procedure to mass produce 100Mo tar-gets is ongoing. Targets have undergone preliminary testing to 250 μA.

Introduction Technetium-99m, the daughter of 99Mo is the most commonly used radioisotope in nuclear medicine [1–2]. Current global crisis of 99Mo supply, aging of nuclear reactors and staggering costs force the search for alternative sources of 99mTc. Radioisotope Centre POLATOM joined the IAEA Coordinated Research Project on “Accelerator-based Alternatives to Non-HEU Production of 99Mo/99mTc”. The planned outcome of this project is development of 99mTc production method using the reaction of 100Mo(p,2n)99mTc [3] in Polish cyclotron. This work presents the results concerning preparation of 100Mo target for irradiation with protons. Material and Methods The manufacturing of Mo target was performed using pressing of molybdenum powder into pellets and its sintering in hydrogen atmosphere at 1600 oC [4]. For this purpose a tantalum and stainless steel plates were used as support. Several pellets using molybdenum powder with particles size of 2 µm in diameter were pressed at different values of pressure. Results and Conclusion The optimized parameters of pressing molyb-denum pellets with various sizes are given in TABLE 1. It was found that the pellets did not adhere neither to the tantalum nor stainless steel plates but they conducted electricity very well. Pellets prepared with higher pressure were more mechanically resistant, however application, even the highest used pressure did not ensure its satisfactory stability. In order to improve mechanical strength, pressed Mo pellets were sintered in hydrogen atmosphere at temperature of 1600 °C. As a result of this process dimensions of Mo pellets decreased: diameter by 13 %, thickness by 12 %, weight by 1.5 %, volume by 34 % while density increased by 50 %. The changes of these parameters are associated with reduction of molybdenum oxide and removal of oxygen from intermetallic space. It was confirmed by photos of microscopic cross section of pellets before and after sintering. It was observed, that after sintering Mo pellets got a metallic form with very high hardness and mechanical strength.

Introduction 100Mo target design is key to commercially viable large scale cyclotron production of 99mTc. The target back plate supporting the 100Mo must be chemically inert to the target dissolution conditions but ideally it should also be able to dissipate the high thermal loads of irradiation, not contaminate target substrate with radionuclidic by-products, and be adequately inexpensive to allow for single use. Aluminum was selected as our target support as it satisfies these requirements. Our process entails rolling 100Mo powder into a foil of desired thickness, and then diffusion bonding [1] the foil onto an aluminum back plate. The 100Mo targets were designed to be 20×80×0.1 mm to match our TR24 cyclotron’s proton beam profile and energy. Efforts are currently underway to scale up the process to allow for simultaneous production of multiple targets at once. Material and Methods The crude enriched 100Mo foil (99.815% enrichment) was made from 100Mo powder using a horizontally mounted rolling mill and an aluminum hopper. The crude foil was rolled repeated-ly, and the space between the rollers gradually reduced until the thickness of the foil was changed from an initial thickness of 0.3 mm to a thickness of 0.1 mm. The rolled 100Mo foil was annealed under reducing atmosphere and then bonded to the aluminum target plate support under inert atmosphere in a heated press at 500 °C. Results and Conclusion By rolling 100Mo foils from powder we were able to produce uniform foils with an average density of > 98 % compared to the maximum theoretical density of 100Mo (n = 5) and thicknesses of roughly 0.1 mm. All foils produced were the desired 20 mm width (i.e. limited by the width of the opening of the hopper) and trimmed to the desired 80 mm length. The annealing process was necessary due to the brittleness of the un-annealed rolled foil and the difference in the thermal expansion coefficients of molybdenum and aluminum which caused un-annealed foils in previous experiments to crack and break off during pressing (n = 10). Surface preparation of the aluminum support plate was also found to play a critical step in the efficiency of the bond, and continuing effort to scale the above de-scribed procedure to mass produce 100Mo tar-gets is ongoing. Targets have undergone preliminary testing to 250 μA.

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