Transient diffusion of radionuclides from a cylindrical waste solid into fractured porous rock

Technical Report · Sat Sep 01 00:00:00 EDT 1990

DOI:https://doi.org/10.2172/5986672· OSTI ID:5986672

Ahn, J ^[1]; Chambre, P L; Pigford, T H ^[2]

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1. Tokyo Univ. (Japan). Faculty of Engineering
2. California Univ., Berkeley, CA (USA). Dept. of Nuclear Engineering Lawrence Berkeley Lab., CA (USA)

This paper presents the numerical results of an analytical study for mass transfer and transport of radionuclides released from a cylindrical waste solid into water-saturated fractured porous rock. The purposes of this study are (1) to predict the diffusive mass flux from a cylindrical waste solid into a planar fracture and the surrounding rock matrix for the low-flow conditions wherein near-field mass transfer is expected to be controlled by molecular diffusion and (2) to investigate the effects of cylindrical geometry and of multidimensional matrix diffusion including diffusion in the directions parallel to the fracture plane. In the paper are presented the derivation of an analytical solution for the time-dependent mass transfer from the cylinder for low-flow conditions and computer-code implementation and numerical results. The problem was first proposed and solved analytically by Chambre. Numerical results are shown for (1) the diffusive mass fluxes from the cylindrical waste solid into the fracture and into the rock matrix, (2) the diffusive mass flux across the rock/fracture interface, and (3) the instantaneous concentration isopleths in the fracture and in the rock matrix. Comparison of the present cylindrical model with previous planar models, wherein contaminant was assumed to be released only into the fracture and diffusion in the rock matrix was assumed to be one-dimensional perpendicular to the fracture plane, shows that the cylindrical model is more conservative than the planar models with respect to the mass transfer from the source into the fracture and with respect to the far-field transport, provided that diffusion is dominant in the fracture. 21 refs., 10 figs., 3 tabs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• Sponsoring Organization: DOE; USDOE, Washington, DC (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5986672
• Report Number(s): LBL-25766; ON: DE91010211
• Country of Publication: United States
• Language: English

Related Subjects

052002* -- Nuclear Fuels-- Waste Disposal & Storage
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
540230 -- Environment
Terrestrial-- Radioactive Materials Monitoring & Transport-- (1990-)
COMPUTER CODES
COMPUTERIZED SIMULATION
DIFFUSION
ENVIRONMENTAL TRANSPORT
FRACTURE MECHANICS
GEOMETRY
HIGH-LEVEL RADIOACTIVE WASTES
IMPLEMENTATION
MANAGEMENT
MASS TRANSFER
MATERIALS
MATHEMATICAL MODELS
MATHEMATICS
MECHANICS
POROSITY
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTES
RADIONUCLIDE MIGRATION
ROCKS
SIMULATION
SPACE DEPENDENCE
TIME DEPENDENCE
WASTE DISPOSAL
WASTE MANAGEMENT
WASTES