Coupled Thermohydromechanical Modeling of the Full-Scale In Situ Test “Prototype Repository”

Abstract

The Prototype Repository project represents a full-scale in situ test of the Swedish concept for high level radioactive waste disposal in deep geological repositories, being conducted at the underground Äspö Hard Rock Laboratory and managed by SKB (Swedish Agency for Radioactive Waste Disposal). Instead of canisters with radioactive material, heaters installed in cylindrical containers surrounded by compacted bentonite have been used in the test. A large number of thermohydromechanical parameters for materials used in the test were carefully determined based on the latest laboratory experiments and site investigation. After comparison among six simulation models, some valuable conclusions are made about the interaction effects of six deposition holes and the effects of thermohydrogas–mechanical coupling. A three-dimensional coupled thermohydraulic model was selected for the prediction of temperature, whereas an axisymmetric two-dimensional coupled thermohydromechanical model was selected for the prediction of relative humidity and stresses for the system of heater–bentonite–near rock. Selected results of temperature, relative humidity, and total stress are presented and discussed, and the agreement between the compared variables highlights the ability of the developed models to reproduce the complex coupled processes involved in the test.