The program for the final disposal of low and intermediate level radioactive waste was established by Paks Nuclear Power Plant, Hungary. Preparation for final disposal of radioactive wastes has been done as part of a national program since 1993. The Central Nuclear Financial Fund and the Public Limited Company for Radioactive Waste Management (Puram) have been established to coordinate organizations and activities for all tasks in connection with nuclear waste treatment. The project started with a geological screening in order to find the most suitable formation for the radioactive waste disposal. The selected potential host rock is a granite complex in the Mórágy Granite Formation in the south-western part of Hungary, close to the village of Bátaapáti. The goal of this paper is to present the newest modeling results of the Excavation Damaged Zones around the Bátaapáti radioactive waste repository. The following zones are thoroughly investigated and modeled in both 2D and 3D: EdZ: Excavation Disturbed Zone; EDZ: Excavation Damaged Zone and HDZ: Highly Damaged Zone.
These Excavation Damaged Zones (EDZs) are very important for understanding the hydromechanical and geomechanical behavior. Therefore the EDZs were analyzed by hydrogeological, filed-survey, geophysical and Borehole Television (BHTV) methods. Our modeling was using both high number of laboratory rock tests and the field measurements. The correlation between the computed and measured values, were verified.
Due to the latest studies of excavation damaged and disturbed zones three different zones are distinguished (see Figure 1):
Excavation disturbed Zone or Excavation Influence Zone (EdZ or EIZ), which is a zone with hydromechanical and geomechanical modifications, without major changes in flow and transport properties. Stress and/or strain in EdZ zone involves only elastic change and EdZ is situated beyond the EDZ. The pore volume may be affected close to the EIZ-EDZ transition by the elastic strain.
Excavation Damaged Zone (EDZ), is a zone with hydromechanical and geomechanical modifications inducing significant changes in flow and transport properties. The damage in this zone is in the form of grain scale fractures and minor interface dilation from the EIZ-EDZ transition to interconnected at the EDZ-HDZ. This zone could be subdivided into outer – EDZo and inner EDZi zones.
Highly Damaged Zone (HDZ), is a zone where macro-scale fracturing or spalling may occur. The EDZ and HDZ in different cases: homogeneous rock mass_ (a), modification of EDZ and HDZ due to one pre-existing fracture (b), modification of EDZs in jointed rock mass (c) (after Lanyon et al. 2009).
fractures are typically interconnected which results in a significant increase of the effective permeability in this zone.