Report on a programme of testing and improving the geosphere models used within SYVAC

A number of geosphere models for use with the SYVAC (System Variability Analysis Code) computer program have been developed, and are described in various previous reports. The SYVAC computer program provides an assessment of the dose effect to man resulting from buried wastes, using a series of submodels to represent transport processes in the vault, geosphere and biosphere. The work reported herein describes a programme of testing and improvements carried out on these models. It is concluded that the individual solution methods work well within stated parametric limits, and that further development studies should await a commitment to use SYVAC for the radiological assessment of specific named sites. The exception to this general rule may be the consideration of overall time scales and time stepping methods used within SYVAC. (author)