HYTEC

Reactive transport modelling is a topic that has the wind in its sails. Indeed, the approach based on the coupling of an element transportation hydrodynamic model with a speciation model is currently used in an increasing number of fields : radioactive waste storage, geological gas storage, industrial waste recovery, material and structure durability, impact studies of polluting deposits, and many other fields.
 
The chemistry-transportation coupled models, among them HYTEC, are increasingly recognized and used. HYTEC is being under development since 1993 ; it is known for its reliability and especially for its ability in solving real problems posed both by the scientific community and the industrial world.
 

Presentation of the code

HYTEC is a modular and upgradable simulation platform, mainly composed of a hydrodynamic module (R2D2), a reaction module (CHESS) and a coupler. The approach is easily upgradable and coupling with other modules is currently being considered (a module of river flow, for example).
 
The R2D2 module describes the flow of liquid phases (saturated flows, unsaturated flows, transitory steady flows), the transport of heat and that of elements in porous or fractured environments in one, two or three dimensions. In view of the coupling, a scheme of finite volume spatial discretization has been chosen. This scheme is particularly well suited to reactive systems. The flexibility of a Voronoi-type gridding used by default by R2D2 allows irregular domains, possibly very complex domains, to be meshed.
 
The CHESS module simulates the chemical and microbiological reactions within each mesh of the model. CHESS is based on a powerful solution motor, highly optimized for coupled calculations. Chemical calculations use an extended thermodynamic database, allowing calculations to be performed at the equilibrium state. In addition, CHESS has a generalized kinetic approach, applicable to all types of reaction.
 
HYTEC is optimized and can now run on a modern desktop computer. But it is also a massively parallelized software, which allows heavy calculations to be performed in a reasonable CPU time (provided one has a dedicated machine, as a PC cluster for example). In addition to these possibilities, the user has a utility programme for viewing and using results, named HYPE.
 

Application fields

The HYTEC application fields are varied, ranging from simple systems of laboratory columns to the integrated simulation of all the engineered barriers of a radioactive waste storage. It is applied to safety studies of gas geological storage, including the durability of wellhead concrete. As for emerging application fields, HYTEC is particularly well suited to the topic of solidified waste leaching and material biodegradation, or to impact studies of polluting deposits such as mining tailings or cleaning sediments. In addition, the platform is not restricted to porous media and geological systems : it is perfectly suited to calculations of material and structure durability such as the study of steel corrosion in the circuits of nuclear power plants and that of the efficiency of filters and ion exchange resins. Applications thus cover a significant number of time and space scales.