A key aspect of Quintessa's work is state of the art numerical analysis of complex coupled systems to develop an understanding of systems and their controlling processes and parameters. Examples include Thermal-Hydraulic-Mechanical-Chemical (THMC) models of radioactive waste disposal facilities at all scales, detailed predictive and retrospective analysis of field and laboratory experiments, complex non-linear near-surface hydrogeological modelling and novel mechanical modelling of AGR reactor cores. COMSOL Multiphysics forms an increasingly important part of Quintessa's capability to deliver such sophisticated bespoke modelling solutions.

Successful modelling and simulation requires expert users in addition to state-of-the-art software. Quintessa employees have a wide range of scientific experience encompassing the mathematical, physical, chemical, biological and earth sciences, and are well versed at applying their expertise to novel projects, as well as the more established areas of radioactive waste management, contaminated land and groundwater, and sub-surface carbon dioxide storage. Typical multiphysics projects at Quintessa encompass:

• Hydrogeological Analysis, including conceptual analysis, fate and transport simulation, coupled variable density flow, vapour transport and non-Darcy behaviour.
• Thermal Analysis, including radiation and non-linear effects.
• Mechanical Analysis, including coupled poro-mechanics, creep and plasticity.
• Chemical Analysis, including reactive and non-reactive transport in fractures and porous media, often in direct support of radioactive waste disposal safety cases.

The following images illustrate Quintessa's application of COMSOL Multiphysics to nuclear industry problems.