Application of molybdenum-99 to nuclear medicine and its production

Mo-99 is produced in large quantity as the parent nuclide of Tc-99m recently used most in the field of nuclear medicine. It is administered into human bodies in the form of radioactive medicines combined with various compounds, and utilized for nuclear-medical diagnosis such as cancer. The pervasion of Tc-99m is mostly owing to its excellent nuclear and chemical characteristics, the development of the generators to effectively utilize it and the advance of the equipment for diagnosis such as scintillation cameras. For the mass production of Mo-99, the neutron capture reaction of Mo in nuclear reactors or the nuclear fission of U-235 are utilized. In the former, the manufacturing process is simple, but it is hard to obtain the product with high specific radioactivity. In the latter, Mo-99 must be separated with high purity from the fission products of many kinds and large quantity, therefore, the manufacturing process is very complex. However, the specific radioactivity of the product is very high. These are used separately according to the object of diagnosis. In this paper, the present status of the manufacture and utilization of Mo-99 is explained, centering around the state of development of its manufacturing techniques in Japan Atomic Energy Research Institute. (Kako, I.)