複雑形状部遮蔽設計法の安全裕度評価に関する実験的研究

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Investigation and assessment are carried out for approximate design calculation methods of radiation streaming in shield irregularities. Investigation items are definition of source and streaming radiation components, calculation methods of streaming radiation, streaming formulas for each irregularity, problems in application of streaming formulas, simple calculation codes and albedo data. As a result, it is clarified that streaming calculation formulas are not enough to cover various irregularities and their accuracy or application limit is not sufficiently clear. Accurate treatment is not made in the formulas with respect to the radiation behavior for slant incidence, bend part, offset and so on that results in too much safety factors in the design calculation and distrust of the streaming calculation. To overcome the state and improve the accuracy of the design calculation for shield irregularities, a simple method is developed to calculate radiation streaming through irregularities in an ordinary concrete shield. It includes neutron and gamma-ray calculations and can be applied to the problems of practical slant incidence. The method is essentially one of summing the streaming dose rates from the different neutron and gamma components which are functions of energy and angle of incident radiation, dimensions of irregularities, etc. Dose rates in irregularities are calculated by the Monte Carlo code MCNP. Radiation sources are plane mono-directional fission neutrons, intermediate neutrons, thermal neutrons and 1.25-MeV gamma rays. Incident angles of radiation are changed between 0 and 60 deg. For bend ducts or slits, an isotropic plane source is placed inside the inlet opening to reduce computation time. Calculated results are arranged into the form of a database. Reliability of the Monte Carlo calculations are assessed by comparison with experiments using a 6OCo source or a 252Cf source and calculations by an one-dimensional discrete ordinates code ANISN.
独立行政法人海上技術安全研究所の論文
2002-06-28

複雑形状部遮蔽設計法の安全裕度評価に関する実験的研究

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