Expected repository environments in granite: assessment of rock stability of the container drill hole region

This report was prepared as part of a study on Expected Repository Environments in Granite (ERE-G). The repository regions considered in this report were the disposal room, the pillar between rooms, and the waste container drillhole. Three-dimensional analyses were performed to predict temperatures in the rock and to investigate the thermoelastic response and its effect on rock stability. Calculated factors-of-safety of intact rock identify zones of potential rock instability. The analyses were performed for three different types of waste: spent fuel (SF), commercial high-level waste (CHLW), and defense high-level waste (DHLW). The highest temperatures were predicted in the rock when considering CHLW and the lowest when considering DHLW. The analyses did not predict any rock instability as a consequence of excavating the room and the container drillhole. In all cases, relatively high tensile stresses develop in the upper part of the drillhole. The analyses give evidence of potential stability problems of the rock around the drillhole later in time for both the SF and the CHLW. In the case of DHLW, no instability of the rock was predicted during the time period considered in these analyses. 7 references, 24 figures