| 摘要 |
PROBLEM TO BE SOLVED: To improve the efficiency in the utilization of neutrons in a region where radioactive nuclides are generated by locating a material, such as graphite, whose action for reflecting neutrons is strong behind the region where radioactive nuclides are generated. SOLUTION: A reflector 3 made of graphite is located behind a region 2, composed of a lithium hydroxide solution, where radioactive nuclides are generated. Then, neutrons generated from a neutron source 1 reach the region 2 and react with 6Li to generate 3t. The 3t reacts like 16O and 16O(t, m)18F to generate radioactive nuclides 18F for positron emission tomography(PET). On this occasion, the neutrons reflected by the graphite generate 3t again similarly and it reacts like 16O and 16O(t, m)18F to generate radioactive nuclides 16F for PET similarly, so that substances can be used effectively. In other words, the provision of the reflector 3 makes it possible to obtain a neutron utilization rate of 60% or higher even if the thickness of the region 2 is 3 cm.
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