Investigation of Criticality Effects of Deuterium and Beryllium in Package Containing Fissile Material

概要

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The maximum mass of deuterium and beryllium in fissile exempted packages is strictly limited under subparagraph 672(a) of the IAEA Regulations for the Safe Transport of Radioactive Material (TS-R-1). 1) This is because the restriction of fissile material mass in the subparagraph is based upon the assumption of hydrogenous moderation and reflection and that deuterium and beryllium are potentially more effective than hydrogen in terms of criticality. However, the basis of the deuterium and beryllium limits in the subparagraph is not clear and it may be inappropriate to impose a limit on their mass alone.In order to evaluate the reactivity effects of deuterium and beryllium in hydrogenous moderation and reflection, a series of calculations is performed using simple models with various parameters. The parameters include fissile nuclides, fissile concentrations, and concentrations of deuterium or beryllium in the moderator or the reflector. According to the calculation results, the concentrations of deuterium or beryllium as well their mass in the moderator or the reflector should be considered when establishing criticality based limits. This shows that, when beryllium or deuterium are present in very low concentrations within a package containing fissile material, the total mass of each may not be the only relevant factor to consider in terms of criticality.
社団法人日本原子力学会の論文
2007-06-25