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STUDY OF THE COUPLED THERMO-HYDRO-MECHANICAL EFFECTS ON A HLW REPOSITORY IN A GRANITE GEOLOGICAL FORMATION.

Objective

FOR THE EVALUATION OF THE PERFORMANCE OF RADIOACTIVE WASTE GEOLOGICAL STORAGE, THE DESCRIPTION OF HYDRAULIC, THERMAL, CHEMICAL AND MECHANICAL PHENOMENA IS NECESSARY IN THE NEAR FIELD AND IN THE FAR FIELD. THE DIFFICULTY OF THIS DESCRIPTION RESTS, ON ONE HAND IN THE DEFINITION OF BEHAVIOUR LAWS IN ACCORDANCE WITH TIME AND SPACE THAT WE CONSIDER, ON THE OTHER HAND IN THE CONNECTING OF PHENOMENA.
THE STUDIES ALREADY ACHIEVED ON THIS SUBJECT IN THE DIFFERENT COUNTRIES ARE CONCERNED WITH EITHER THERMO-MECHANICAL EFFECTS OR THERMO-HYDRAULIC EFFECTS.
THE MAIN PURPOSE OF THIS STUDY IS TO CONSIDER TOGETHER THE THERMO-HYDRO-MECHANICAL EFFECTS DUE TO A HLW REPOSITORY IN A GRANITE SITE. IN ORDER TO DO SO TWO MODELS AVAILABLE NOW ARE COUPLED : CASTEM (THERMO-MECHANICAL MODEL) AND TRIO (THERMO-HYDRAULIC AND MIGRATION MODEL). STUDIES OF RADIONUCLIDES MIGRATION IN THE GRANITE ROCK ARE CONDUCTED WITH THE COUPLED MODEL AND THE HYDRAULIC MODEL IN ORDER TO EVALUATE THE INFLUENCE OF THE DIFFERENTS PHENOMENA.
The evaluation of the radiological consequences associated with the migration of radionuclides released by a nuclear waste repository in a geological medium should take into account the evolution of the geosphere and consider internal phenomena associated with the presence of the wastes.

In this study an assessment was made of groundwater flow modifications and their consequences on the radionuclide migration connected with the heat generation from vitrified high level wastes. It considered a crystalline site, with isotropic properties, modelled as an equivalent porous medium.

The study showed that a first generation of models can take into account coupled phenomena, and that, using the chosen assumptions of the parameter values, the consequences on radionuclide migration in the framework of a normal evolution scenario are very slight. This can be explained by the behaviour of the radionuclides, which do not reach the zones where the flow is perturbed before the end of the thermal phase, when the initial flow is recovered.
1. THERMAL CALCULATIONS
2. THERMO-MECHANICAL COMPUTATIONS
3. HYDRAULIC AND MIGRATION CALCULATIONS
3.1. REFERENCE CALCULATION WITHOUT THERMAL AND MECHANICAL COUPLING
3.2. COUPLING WITH THERMAL EFFECTS
3.3. FULL COUPLING (THERMAL AND MECHANICAL EFFECTS).

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

NATIONAL RADIOACTIVE WASTE MANAGEMENT AGENCY OF FRANCE
Address
Rue Jean Monnet 1-7
92298 Chatenay Malabry
France