Geological characterization of 4 potential sites for siting of the deep geological repository in the Czech Republic.

Radioactive waste repository authority (SÚRAO) is responsible for the safe disposal of radioactive waste in the Czech Republic in accordance with the requirements of nuclear safety and environmental protection. SÚRAO currently operates low- and intermediate-level waste repositories Bratrství in Jáchymov (a former uranium mine), Richard (a discontinued limestone mine), and Dukovany (located on the premises of a nuclear power plant). Globally, deep geological repositories (DGR) are regarded as the safest solution for high-level waste and spent nuclear fuel, , Janoch, Hrádek, and Horka. The final site will be determined through a multicriteria evaluation, with an emphasis on favorable geological conditions. To support this decision, SÚRAO, in collaboration with its partners and contractors, is conducting one of the largest geological investigations in Czech history, aiming to finalize the site selection by 2030.

Generally, there are 3 main host rock types for DGR; sedimentary, crystalline and salt. Czech Republic decided to adapt crystalline host rock concept base on the rock type composition of region.  All sites are situated within Bohemian massif unit, comprised mostly of variscian methamorpohsed rocks with numerous plutonic intrusions. The westernmost site is Březový potok, belonging to Central Bohemian Pluton. The site is formed by granodiorites intrusion into the older moldanubian unit ca. 346 Ma. Janoch is located within monotonous moldanubian subunit, part of moldabian unit. It comprises of paragneiss ca 340 Ma old. Hrádek mostly consists of granites (Eisgarn type) belonging to moldanubian plutonic complex. Horka sites sits within Třebíč pluton complex formed by K- and Mg-rich melanocratic microsyenite, commonly known as “Durbachite” which intruded into the older moldanubian rocks ca. 340 Ma.

While geological investigations have been ongoing throughout the site selection process, current efforts focus on obtaining detailed data at depths of 500 meters, the projected depth for the Czech DGR. Advanced geophysical methods, capable of delineating geological structures at depths of up to 1,000 meters, are critical to this process. Extensive drilling campaigns are planned at each site, involving multiple boreholes targeting depths of 300, 600, and 1,200 meters. Each borehole is planned to produce oriented drill cores and carry on comprehensive borehole testing, designed to verify crucial geological features above, at, and below the intended DGR depth. In addition to drilling, complementary research activities, such as detailed geological mapping and monitoring, are ongoing. These combined methods aim to construct comprehensive 3D geological models for each potential site. These models will serve as the cornerstone for the final site selection process in 2030.