Development of Vault Model 'VERMIN' For Post Closure Behaviour of Repositories for Non-Heat Generating Radioactive Wastes

摘要

The computer model VERMIN has been developed to simulate the post closure time dependent behaviour of the vault section of a Land 3 and a Land 2 type repository. Development was carried out within the constraints of the computer code SYVAC. Output from the new model, in terms of radionuclide fluxes versus time, provides the source term for that code. A number of conceptual designs for different geological conditions were produced and used to develop the model. Unlike SYVAC, the boundary of the vault was considered to be at the interface between the damaged rock zone and the undamaged host rock. VERMIN treats the vault as a series of engineered barriers namely: waste matrix, waste package, backfill material liner and the damaged rock zone. For the Land 3 repository, the vault was considered to be fully saturated and consequently corrosion, leading to eventual package failure, will occur. VERMIN allows for package failure and subsequent leaching and then calculates the migration of nuclides from within the vault out to its boundary. One dimensional advection and two dimensional diffusion/dispersion are modelled allowing for retardation due to sorption radionuclide saturation and radionuclide decay. Radioactive decay chains up to eight members can be modelled by VERMIN. (Atomindex citation 15:059742)