Geological investigation work

Geological investigation work provides the data required for the basic description of the candidate site, the results of which form input for the assessment of long-term and operational safety, technical feasibility and the environmental impact assessment.

The planning and realisation of such work is based on the requirements of the Geological Act (Act No. 62/1988 Coll.), the Atomic Act (Act No. 263/2016 Coll.), the requirements of an SÚJB Decree on the siting of nuclear facilities (Decree No. 378/2016 Coll.) and the criteria for the selection of the site for the construction of the deep geological repository (SÚRAO MP.22 document).

The basic output of geological investigation work consists of information on the lithological composition of the rock, mutual connections between rock complexes, the localisation and character of brittle rock disruption (fractures, faults, fault zones) and the structural and metamorphic development and geochemical character of the rock environment. Equally importantly, information is also obtained on the natural phenomena and processes that can be expected to occur within the repository, the occurrence of mineral resources including the groundwater and anthropogenic activities that influence the various components of the natural environment.

Geological investigation work is performed in the form of two basic procedures as defined by the Geological Act – geological research and geological survey work. The geological survey is conducted via the application of so-called exploration area polygons and is aimed specifically at determining a rock block suitable for the permanent disposal of the anticipated radionuclide inventory of the future deep geological repository and the future territorial protection of the site. Geological research is conducted over a wider area than the survey (i.e. up to 300 km from the site) and serves primarily for compiling general descriptions of the relationships between individual rock units and the hydrogeological regime as well as for the assessment of the risk of seismic events.

Geological investigation work involves the application of the full range of research and exploration methods available. In the past, SÚRAO has conducted, for example, aerial geophysical research, micro-seismic and hydrogeological monitoring, the study of satellite and aerial photographs and geological mapping. The outcomes of the geological investigation work consist of a geological map, i.e. a two-dimensional model of the area in question and a comprehensive database of geological knowledge that can be used to compile geological models of the rock mass using advanced computer programs. The most important models that SÚRAO has compiled and put into practice to date include a 3D structural-geological model which covers a depth range exceeding 1 km and a hydraulic model which describes the velocity and direction of groundwater flow.

Moreover, the data obtained also allows for the compilation of transport models that describe the potential velocity of the transport of radioactive substances through the rock environment. Other models based on data obtained from geological investigation work include geochemical models that describe the state of and changes in the groundwater chemistry, and geomechanical models that provide for the assessment of the stability of the future underground workings based on the determined stress directions within the rock environment and the geotechnical parameters of the rock and the rock massifs. All of this information provides input for the assessment of the long-term safety of the deep geological repository and its feasibility as well as the evidence that the site fulfils national and international requirements relating to the construction of nuclear facilities. These models are regularly updated so as to reflect the results of the latest research and survey work at each stage of the site selection process.

Geological surveying