Remediation of Uranium In-Situ Leaching Area at Stráž pod Ralskem, Czech Republic

Abstract

A large-scale development in exploration and production of uranium ores in the Czech Republic was done in the 2nd half of the 20th century. Many uranium deposits were discovered in the territory of the Czech Republic. One of the most considerable deposits in the Czech Republic is the site Hamr na Jezere – Straz pod Ralskem where both mining methods — the underground mining and the acidic in-situ leaching — were used. The extensive production of uranium led to widespread environmental impacts and contamination of ground waters. Over the period of “chemical” leaching of uranium (ca. 32 years), a total of more than 4 million tons of sulphuric acid and other chemicals have been injected into the ground. Most of the products (approx. 99.5 %) of the acids reactions with the rocks are located in the Cenomanian aquifer. The contamination of Cenomanian aquifer covers the area larger then 27 km2. The influenced volume of groundwater is more than 380 million m3. The total amount of dissolved SO42− is about 3.6 million tons. After 1990 a large-scale environmental program was established and the Czech government decided to liquidate the ISL Mine and start the remediation in 1996. The remediation consists of contaminated groundwater pumping, removing of the contaminants and discharging or reinjection of treated water. Nowadays four main remedial technological installations with sufficient capacity for reaching of the target values of remedial parameters in 2037 are used — the “Station for Acid Solutions Liquidation No. One”, the “Mother liquor reprocessing” station, the “Neutralization and Decontamination Station NDS 6” and the “Neutralization and Decontamination Station NDS 10”. It is expected that the amount of withdrawn contaminants will vary from 80 000 to 120 000 tons per year. Total costs of all remediation activities are expected to be in excess of 2 billion EUR.