![]() If desired, these other fission products can be recovered separately. Following irradiation, the targets are chemically processed to separate Mo-99 from other fission products. ![]() This irradiation causes U-235 to fission and produces Mo-99 and many other fission products, including I-131 and Xe-133. A recent report of the National Research Council and Institute of Medicine (NAS and IOM, 2007) provides a description of the imaging process.Īs will be described in more detail in the following section, Tc-99m is currently produced through a multistep process that begins with the neutron irradiation of fissile U-235 contained in HEU (see Sidebar 1.1) or LEU targets in a nuclear reactor. The data collected by the camera are analyzed to produce detailed structural and functional images. This photon energy is ideally suited for efficient detection by scintillation instruments such as gamma cameras. The isotope has a half-life of about 6 hours and emits 140 keV photons when it decays to Tc-99, a radioactive isotope with about a 214,000-year half-life. Tc-99m is especially useful for nuclear medicine procedures because it can be chemically incorporated into small molecule ligands and proteins that concentrate in specific organs or tissues when injected into the body. Tc-99m is used for the detection of disease and for the study of organ structure and function. The decay product of Mo-99, Tc-99m, is the workhorse isotope in nuclear medicine for diagnostic imaging. All of these isotopes can be recovered when the targets are processed to obtain Mo-99. ![]() These fission products are produced in the same proportions to each other whether HEU or low enriched uranium (LEU) targets are used. The fission of uranium-235 (U-235) produces a spectrum of fission products (see Figure 2.5) including Mo-99, I-131, and Xe-133. These other medical isotopes are not being recovered for sale by all major Mo-99 producers because they can be more cheaply produced and purchased from other sources. Other medical isotopes such as iodine-131 (I-131) and xenon-133 (Xe-133) are by-products of the Mo-99 production process and will be sufficiently available if Mo-99 is available. 2.īetween 95 and 98 percent of Mo-99 is currently being produced using highly enriched uranium (HEU) targets (NNSA and ANSTO, 2007), which was the major concern of Congress when it mandated this study. The decay product of Mo-99, technetium-99m 1 (Tc-99m), is used in about two-thirds 2 of all diagnostic medical isotope procedures in the United States. The congressional mandate for this study calls for an examination of the production of medical isotopes to include “molybdenum 99, iodine 131, xenon 133, and other radioactive materials used to produce radiopharmaceuticals for diagnostic and therapeutic procedures or for research and development.” However, the authoring committee determined that for the purposes of addressing the statement of task for this study ( Sidebar 1.2), it is sufficient to focus on the production of the medical isotope molybdenum-99 (Mo-99).
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