Transient-Diffusion Measurement of Radon in Japanese Soils from a mathematical Viewpoint
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概要
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A transient-diffusion measurement method for radon diffusion coefficients in porous materials was first developed in the U.S.A. To get a correct interpretation of measured data by the transient-diffusion method, more attention needs to be put on mathematical treatment which has been somewhat neglected perhaps because of the inherent mathematical difficulty. Strictly speaking, the measured radon concentrations have to be interpreted mathematically as a two-region problem. But, solving diffusion equations is quite difficult analytically because of time-dependent boundary conditions for the two-region problem. On the other hand, the advent of high performance computers has made it possible to easily solve diffusion equations numerically. However, without good knowledge of the diffusion phenomena in the actual measuring system, there is a possibility that the wrong boundary conditions are set. To prevent this, prior consideration by mathematical interpretation leading to visual understanding of the diffusion phenomena is necessary. The present paper examined how to set up boundary conditions in diffusion equations to obtain radon diffusion coefficients in porous materials, especially Japanese soils, using transient-diffusion data. To reduce the two-region problem to a one-region problem, effective length to the radon measuring device was proposed using the relationship, Dair⁄(B1)2=Dsoil⁄(B2)2, where the subscripts refer to each region, D denotes the radon diffusion coefficient and B denotes the length to the measuring device. This formula was derived in a general form and has universal application; it is not limited to soils. Additionally, as part of a mathematical discussion, a checking method for detector calibration was proposed.
- 一般社団法人 日本原子力学会の論文
- 2006-07-25
著者
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Okuda Takeshi
Nuclear Fuel Industries Ltd.
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Sasaki Tomozo
Radioactive Waste Management Funding And Res. Center
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Gunji Yasuyoshi
Nuclear Fuel Industries Ltd.
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- Transient-Diffusion Measurement of Radon in Japanese Soils from a mathematical Viewpoint