| 摘要 |
PURPOSE:To slowing down and capture fast-neutrons by elastic scattering and to prevent the formation of a colored center by interposing a light element layer between heavy metallic layers. CONSTITUTION:A cushion layer 20, a radiation shielding layer 30 and a cable seal 40 are provided on an optical fiber unit 10 having a central tension member 12 and optical fibers 14. The layer 30 is of the sandwich structure of 3 layers consisting of a light element layer 34 interposed between inner and outer heavy metallic layers 32, 36. Fast-neutrons lose energy by nonelastic scattering in the heavy metallic layers of iron, lead, copper, etc., are slowed down by elastic scattering in the light element layer and are absorbed by the capturing reaction thereof. If <10>B and <6>Li are suitably mixed in the light element layer, the generation or gamma-rays of the capturing reaction is suppressed. Plastics which contain much hydrogen and are mixed with boron carbide are preferable as the material thereof. |
