| 摘要 |
PROBLEM TO BE SOLVED: To provide a control material for a nuclear system and control rods for a reactor capable of increasing control worth. SOLUTION: An absorber having 2 opposite characteristics together utilizes proper spacial change in neutron spectrum in poison assembly concentrated in neutron flux field in a thermal' reactor. The absorber having 2 opposite characteristics together (poison assembly) contains two types of absorber. The first absorber is strong heat absorber 26' near the surface of an assembly and the second absorber is strong resonance absorber 26" inside a poison assembly. Outside region of the poison assembly is constituted of strong '1/v' heat absorber and inside region of the poison assembly is constituted of the resonance absorber. As this resonance absorber selectively absorbs epi-thermal neutron, hardened characteristic of neutron spectrum in the absorber assembly is more properly utilized. By forming the poison assembly having 2 opposite characteristics together, control material worth can be increased maintaining the outer dimensions of structure containing the control material like BWR control rods.
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