Hydrogeologicky vyzkum v Podzemnim vyzkumnem pracovisti Bukov v dole Rozna

In 2013 Radioactive Waste Repository Authority (RAWRA) launched the construction of the underground research facility Bukov (URF Bukov) on the 12th floor of a uranium mine Rožná at a depth of 600 m below the surface. The research of the rock and groundwater properties at depths planned for geological repository of a high level waste (nuclear spent fuel) is the main objective of the URF Bukov. The aim of hydrogeological research is to obtain information on the flow regime and the chemical composition of shallow and deep groundwater in the area and vicinity of the URF Bukov. The documentation of groundwater inflows, the establishment of the monitoring network at the surface as well as in the underground and the sampling for chemical and isotopic composition of the groundwater were performed during the first year of the survey. The continuous monitoring program was initiated in June 2015. An integral part of the research was study of the development of the groundwater composition at different depths on the Bukov site. The groundwater type Ca-SO₄ is typical for the shallow parts of the rock environment and it changes to Ca-HCO₃ water type in the zone of deeper circulation. Stagnant groundwater is Na-HCO₃ type at depths of 1,000 m. Total dissolved solids (TDS) remains unchanged with increasing depth. The TDS of groundwater varies between 200 and 500 mg.l^-1 in both the shallow as well as deep levels of the Rožná mine. The comparison of the chemical composition of the groundwater from the 12th level shows a different origin of the groundwater inflowing from the fault zone in an adit section between 167 and 172 meters (marked as BK06 point). The source of this discharge is probably water leaking from higher levels of the mine.
The evaluation of isotope analyses based on tritium and CFCs showed that the proportion of young waters with age less than several hundred years is minimal.
There was an evidence of considerably high variability of the chemical composition of the groundwater and inflow yield of the waters in the URF. The total discharge from the URF Bukov is about first units of liter and the occurrence of several significant inflows from fault zones shows that highly conductive structures appear even at depths of 600 m under the surface. Subsequent study of these conductive zones is crucial for the future siting of a deep geological repository.