The CALIBRE source-term code: technical documentation for Project-90

A numerical model has been developed which simulates the diffusion of radionuclides from a high-level waste canister, through a backfill region and into a fractured rock matrix. The model includes chain decay and ingrowth, linear equilibrium sorption, solubility limiting and response to a redox front as it emerges from the canister and migrates through the near-field. Radial advection (which approximates the advection downstream from the canister and buffer) is applied in the fracture, in addition to diffusion or dispersion. This document describes the mathematical model and numerical methods used in developing CALIBRE, together with a number of verification tests which compare the results with those computed using analytic solutions. (au)