MODIFYING TOUGH2 TO SUPPORT MODELING OF GAS-TRANPORT THROUGH SATURATED COMPACTED BENTONITE AS PART OF THE LARGE-SCALE GAS INJECTION TEST (LASGIT) IN SWEDEN

The LASGIT (Large Scale Gas Injection Test) project is a full-scale test of gas transport in bentonite at the Aspo Hard Rock Laboratory in Sweden. Simulating conditions in a deep geologic repository for spent fuel, an empty copper container surrounded by compacted bentonite blocks is placed within a large-diameter borehole in the host rock of the Hard Rock Laboratory. Once the buffer is completely saturated with groundwater, He gas is injected from ports on the container and monitored as it migrates from the container through the bentonite buffer to the host rock. The intent of the LASGIT experiment is to improve the understanding of gas migration through the engineered barrier of a deep geologic repository for spent fuel and to validate different modeling approaches which may be used in future safety assessments. A preliminary gas-transport model of the LASGIT experiment was developed with a modified version of TOUGH2. This paper will describe the modifications to the TOUGH2 code, present the implementation of the LASGIT experiment in a numerical model and discuss preliminary model results.