EURAD D2.18 Report on the conceptualization of upscaling including upscaling & model abstraction methods for the integration of process-level knowledge to disposal cell scale knowledge

Reactive transport models in the context of radioactive waste disposal tend to become increasingly complex due to advancements in understanding and quantifying of (geo)chemical and transport processes in the engineered barriers and surrounding geological layers.
The complexity of these models is caused by the large number and intricasies of the simulated processes, number of interacting species and/or components, differences in scales at which the interactions occur and amount of couplings to simulate. The models can become even more challenging as they have to be applied to long timescales and large spatial scales.
Many model abstraction techniques have been developed in the last decades and the state of the art is described in this document.  Several techniques are explained together with comprehensive descriptions of a plethora of case studies. 
Performing model abstractions will likely result in many benefits.  It will foremost improve the understanding of the complex models and (the role of) their essential factors.  This again will aid to communicate the modelling results to both a technical and lay public.  The reduced computational burden of the model can lead to a more robust uncertainty and sensitivity analysis, which in turn will build the confidence in the model predictions.