Managing beryllium in nuclear facility applications
原子力施設におけるベリリウム管理
Longhurst, G. R.*; 土谷 邦彦
; Dorn, C.*; Folkman, S. L.*; Fronk, T. H.*; 石原 正博
; 河村 弘; Tranter, T. N.*; Rohe, R.*; 内田 宗範*; Vidal, E.*
Longhurst, G. R.*; Tsuchiya, Kunihiko; Dorn, C.*; Folkman, S. L.*; Fronk, T. H.*; Ishihara, Masahiro; Kawamura, Hiroshi; Tranter, T. N.*; Rohe, R.*; Uchida, Munenori*; Vidal, E.*
金属ベリリウムは、核分裂炉や核融合炉の原子力分野で重要な材料の一つである。実際、核分裂炉では材料試験炉の反射体や減速材として、核融合炉では中性子増倍材として使用されている。一方、中性子照射環境下で使用された使用済ベリリウムは、
Co,
Hなどの放射性核種が含まれるため、廃棄が困難である。さらに、米国では
Cや
Nbも含まれることから、クラスC廃棄物として扱われるようになった。本論文は、照射済ベリリウムの廃棄処分に関する課題、リサイクルへの提案をまとめたものである。
Beryllium has important roles in nuclear facilities such as fission reactors and fusion reactors. Its neutron multiplication capability and low atomic weight make it very useful as a reflector in fission reactors. In both applications, the beryllium and the impurities in it become activated by neutrons transmutating to radionuclides, some of which are long-lived and difficult to dispose of. Also, gas production, notably helium and tritium, results in swelling, embrittlement, and cracking, which means that the beryllium must be replaced periodically, especially in fission reactors where dimensional tolerances must be maintained. It has long been known that neutron activation of inherent iron and cobalt in the beryllium results in significant
Co activity. In 2001, it was discovered that activation of naturally occurring contaminants in the beryllium creates sufficient
C and
Nb to render the irradiated beryllium "Greater-Than-Class-C" for disposal in US radioactive waste facilities. In this paper we review the extent of the disposal issue, processes that have been investigated or considered for improving the disposability of irradiated beryllium, and approaches for recycling.