干旱区生态环境知识资源中心(Arid): Spherical diffusion of tritium from a point of release in a uniform unsaturated soil. A deterministic model for tritium migration in an arid disposal site

Arid

DOI	10.2172/10192486
报告编号	NUREG/CR--6108
来源ID	OSTI_ID: 10192486
	Spherical diffusion of tritium from a point of release in a uniform unsaturated soil. A deterministic model for tritium migration in an arid disposal site
	Smiles, D.E.; Gardner, W.R.; Schulz, R.K. [Univ. of California, Berkeley, CA (United States). Dept. of Environmental Science, Policy and Management]
英文摘要	Tritium (Tr), when released as tritiated water at a point in a uniform and relatively dry soil, redistributes in both the liquid and vapor phases. The flux density of Tr in the liquid will exceed that in the vapor phase provided the water content is greater than approximately 15% of the total soil porosity. Thus Tr redistribution must be modeled recognizing transfer ``in parallel`` in both phases. The authors use the diffusion equation cast in spherical coordinates to analyze this problem in order to provide a basis for design of field experiments, and to offer observations on the long term behavior of such systems. The solution of the diffusion equation permits calculation of the evolution of profiles of Tr concentration, within and external to the sphere of released solution, assuming the initial concentration within this sphere to be uniform. The authors also predict the rate of advance of the maximum of Tr as it advances, and attenuates, in the soil. Calculations for the case of 1 million Curies of Tr diluted in 1 liter of water and released at a depth of 20 meters, and 200 meters above the water table, are demonstrated. If the soil has an initial water volume fraction of 0.06 and total porosity of 0.3 they show, for example, that at 5 meters from the point of discharge, the Tr concentration increases to a maximum in 24 years and then slowly declines. That maximum is 1 Curie/liter. The concentration in the gas phase will be 5 orders-of-magnitude less than this. At 60 meters the maximum ever reached in the liquid phase is ca 10{sup {minus}21} Ci/liter; that maximum will be achieved after 408 years. The authors discuss the effects of variation in the volume fractions of water and air originally present in the soil on the effective diffusion coefficient of Tr in soil, consider the effects of a net flux of water in the system, and identify questions to be answered to achieve safe systematic disposal of tritium in the deep unsaturated zone of desert soil.
出版年	1993
报告类型	Technical Report
语种	英语
国家	美国
来源学科分类	54 ENVIRONMENTAL SCIENCES ; SOILS ; RADIONUCLIDE MIGRATION ; TRITIUM ; ENVIRONMENTAL TRANSPORT ; RADIOECOLOGICAL CONCENTRATION ; DIFFUSION 540230 ; RADIOACTIVE MATERIALS MONITORING AND TRANSPORT
URL	http://www.osti.gov/scitech/servlets/purl/10192486
资源类型	科技报告
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/265326
推荐引用方式 GB/T 7714	Smiles, D.E.,Gardner, W.R.,Schulz, R.K. [Univ. of California, Berkeley, CA . Spherical diffusion of tritium from a point of release in a uniform unsaturated soil. A deterministic model for tritium migration in an arid disposal site,1993.