Remediation of the Radioactive Tailings Ponds in the Navoi Mining and Metallurgy Combine (NMMC), Uzbekistan

During 1964 to 1995, all uranium ore mined in Uzbekistan was processed at the Navoi Hydro- Metallurgical Plant producing 57 059 270 tons (solid mass) of uranium tailings, deposited in an impoundment extending over more than 637 ha, which is subdivided into 8 compartments. After 1996 the processing at the Navoi plant switched to processing of gold ore. To handle the legacy of the uranium ore processing a remediation project was implemented, which consists of hydraulic placement of thin layers of gold tailings over the uranium tailings up to a thickness necessary to reach the required attenuation of gamma radiation, radon exhalation and infiltration of precipitation. By gradual placement of thin layers and following a successive loading-consolidation and reloading cycles the covering of weak, compressible tailings becomes possible. The placement of tailings cover layers alternates between the tailings compartments, thus allowing the drying/consolidation in one compartment while continuing the cover placement in the next compartment. After construction of the attenuation layer, a layer of fertile soil is placed to support vegetation of the final surface and protect the remediated tailings from erosion. The implemented remedial solution provides the necessary confinement of the uranium tailings and has a better economic performance than the dry cover placement. (author)