Assessment of radiation exposure and evaluation of remedial measures for the uranium mining and milling area of Mailuu Suu, Kyrgyzstan

The area of the town of Mailuu Suu, Kyrgyzstan, is polluted by radionuclides and heavy metals in tailing dumps and heaps resulting from the historic exploitation of uranium mines. Radioactive substances are stored in 23 tailings and 10 heaps situated along the Mailuu Suu River. The stability of many tailings is at risk. Attention is mostly directed to Tailing 3, because of its important radionuclide inventory and since threatened by the borders of a major landslide. In the frame of a European Commission-TACIS funded project, a radiological monitoring programme was set up and a radiological assessment was performed for critical group members living in the city of Mailuu Suu, located downstream the tailings, or in the village of Kara Agach, partially located on a uranium mine-waste dump. The actual radiological situation is of no immediate concern for most of the population of Mailuu Suu. The actual external exposure and exposure from radon are, respectively, around 1.2 mSv a-1 and 5 mSv a-1, at both locations. Ingestion dose was negligible for a critical group member living at Mailuu Suu. At Kara Agach, however, under the hypothesis that all food and fodder is cultivated locally, exposure from ingestion is much higher (~10-30 mSv a-1). Additional dose from irrigation with Mailuu Suu river water is small in actual conditions (<0.1 mSv a-1). However, there is an important possibility that, triggered by an earthquake or a landslide, (part of the) tailing(s) content may be directed to the river Mailuu Suu. In case the content of Tailing 3 is thrust to river, calculated maximum doses are 45 and 77 mSv a-1 for an adult and a child, respectively, for an assumed exposure duration of 2 years. To impede the consequences of a potential disaster, under the TACIS project different remedial options were evaluated for Tailing 3 including in situ stabilisation and tailing translocation. Also more global remedial options for the Mailuu Suu River valley were proposed (translocation of other tailings, tunnel to deviate river, partial protection of river from landslide blockage).