SwiBAC (Swiss Biosphere Assessment Code) has been developed by Quintessa for the Swiss National Cooperative for the Disposal of Radioactive Waste (Nagra). It provides a capability to assess potential radiological exposures in the biosphere, should radionuclides be released from a geological repository and migrate to the surface environment over long periods of time post-closure.

SwiBAC models a variety of radionuclide transfer processes in a closed self-sustaining agricultural system following transport by groundwater through the geosphere. SwiBAC takes user input and generates models that are run using Quintessa's generic compartment modelling code, AMBER. SwiBAC is run via text input files, the style of which is fully consistent with those for Nagra's source term and geosphere modelling codes, STMAN and PICNIC, which are also supported by Quintessa. SwiBAC can be used independently or linked to time-dependent radionuclide fluxes from PICNIC geosphere calculations, facilitating integrated calculations.

The conceptual and mathematical basis for SwiBAC are fully described in supporting documentation, together with the verification of the code. SwiBAC is developed and maintained within Quintessa's TickITplus accredited quality management system.