Evaluation Method of Gas Leakage Rate from Transportation Casks of Radioactive Materials. (II). Effect of Kinds of Gases on Leakage Rate.:Effect of Kinds of Gases on Leakage Rate

概要

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A sealing function is essential for transportation casks of radioactive materials in order to prevent radioactive materials from being released into the environment. In the safety analysis report, the release rate of radioactive materials into the environment is evaluated from leak path diameter and length obtained from gas leakage test. In this paper, experimental results of gas leakage rates from a very narrow orifice and a capillary tube simulating a leak path experimentally investigated using helium, argon, nitrogen and air as working fluids are presented in order to understand hydrodynamics of choked flow, non-choked free expansion flow and laminar flow in a very narrow leak path : (1) The contraction coefficient of choked flow from very narrow orifices are obtained, (2) an evaluation model of gas leakage rate from a capillary tubes is proposed, in which the acceleration loss in the entrance region, the friction loss in laminar flow with expansion effect and the exit loss for choked flow or non-choked free expansion flow are modeled, and (3) as for gas leakage rates of 10-4 to 10-2 cm3/s which are closely related to the sealing performance of transportation casks of radioactive materials, the proposed simplified evaluation method is verified for various gases.
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