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Description
Technetium-99m is the most used medical radioisotope and has historically been produced in nuclear reactor facilities around the globe but supply chain disruptions have resulted in critical shortages of 99mTc. [1]. Due to continued demand for this radioisotope, interest in 98Mo and 100Mo has grown since the early 2000s as accelerator-based production of 99mTc replaces the reactor-based 235U spallation pathway [2] [3]. Neutron activation of 98Mo and cyclotron based 100Mo(p,2n) production pathways are actively under development and are increasing demand for enriched molybdenum targets in the form of thin foils for nuclear data studies. Foil targets must be free of pinholes and near-uniform in areal density to produce accurate data during beamline experiments. High-quality molybdenum foils are notoriously difficult to make due both to a high melting point and a propensity to shatter during the cold rolling process [4]. Prior literature has demonstrated different pathways of producing rolled molybdenum foils [5-7], but materials characterization of the produced material is lacking. An individual study that applies different production pathways and characterizes the produced material does not exist. This study directly examines the influence of vacuum hot-pressing vs. vacuum sintering as well as electron-beam melting vs. arc melting on the final purity, uniformity, and continuity of the rolled molybdenum foils. Impurity analysis was conducted using ONH analysis and ICP-OES to determine the trace metal and oxygen contamination picked up throughout the fabrication process. Metallography was conducted on the arc/electron beam-melted material to examine for potential voids and harmful oxide/carbide inclusions that limit the final thickness a foil can be rolled to. The outcome of this work is a detailed methodology illustrating an optimal production pathway for pinhole-free rolled molybdenum foils with thicknesses of below 1mg/cm2.
[1] International Atomic Energy Agency. Non-HEU Production Technologies for Molybdenum-99 and Technetium-99m. Technical Report Series No. NF-T-5.4, 3-16 (2013).
[2] Nuclear Energy Agency. Review of Potential Molybdenum-99/Technetium-99m Production Technologies. The Supply of Medical Radioisotopes 13-18 (2010).
[3] J. Ballinger. Short- and long term responses to molybdenum-99 shortages in nuclear medicine. The British Journal of RadiologyVol. 83899-901 (2010).
[4] A. Pandley et al. Fabrication of thin Molybdenum backed target using rolling method. Applied Radiation and IsotopesVol 199 (2023).
[5] F. J. Karasek. Fabrication of Target Foils by Rolling Techniques. Nuclear Instruments and MethodsVol. 102457-458 (1972).
[6] J. P. Greene et al. The production of molybdenum targets for heavy-ion experiments by electron beam evaporation. Nuclear Instruments and Methods in Physics ResearchVol. A303 165-167 (1991).
[7] A. Stolarz et al. Molybdenum targets produced by mechanical reshaping. Journal of Radioanalytical and Nuclear Chemistry Vol 203. 947-952 (2015).
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Isotope R&D and Production.