## Abstract

The FORTRAN IV program DIFMIG calculates one-dimensionally (i.e. column) the diffusive migration of single substances through arbitrary multi-barrier systems according to the diffusion equation

∂C/∂+ = D'(t)∂

where D'(t) is the effective dispersion coefficient and F'(C,t) is a function responsible for time dependent changes in concentration other than dispersion/diffusion (e.g. slow dissolution of a compound from a repository, radioactive decay, and/or build up of daughter products. The method takes possible time dependent variations in the effective dispersion into account.

The diffusion equation is solved by a finite difference implicite method, the resulting trigonal matrix equation being solved by standard methods.

∂C/∂+ = D'(t)∂

^{2}C/∂x^{2}+ F'(C,t)where D'(t) is the effective dispersion coefficient and F'(C,t) is a function responsible for time dependent changes in concentration other than dispersion/diffusion (e.g. slow dissolution of a compound from a repository, radioactive decay, and/or build up of daughter products. The method takes possible time dependent variations in the effective dispersion into account.

The diffusion equation is solved by a finite difference implicite method, the resulting trigonal matrix equation being solved by standard methods.

Original language | English |
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Place of Publication | Roskilde, Denmark |
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Publisher | Risø National Laboratory |

Number of pages | 32 |

ISBN (Print) | 87-550-0810-0 |

Publication status | Published - 1981 |

Series | Risø-M |
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Number | 2262 |

ISSN | 0418-6435 |

## Keywords

- Risø-M-2262
- D codes
- Diffusion lenght
- Finite difference method
- Migration length
- One-dimensional calculations
- Radionuclide migration