Radiological Characterization of a Copper/Cobalt Mining and Milling Site

Extensive copper and cobalt ore deposits can be found in the Katanga Province of the Democratic Republic of the Congo near the city of Kolwezi. These deposits have been mined via open pit and underground mines since the 19th century with many changes in control of the mines including colonial industrial control and Congolese government control. With the recent re-establishment of a relatively stable democratic government in the DRC, foreign investors returned to the area to restart mining activities that were abruptly terminated in the 1990’s due to political turmoil. Some of these new projects are being performed in accordance with World Bank and International Finance Corporation Social & Environmental Sustainability standards. As part of these standards, radiological characterization of the mines, processing facilities, and surrounding environment was conducted to establish current conditions, evaluate human health and ecological risks, and provide a basis for establishment of radiation safety and environmental remediation programs. In addition to naturally occurring radioactive materials associated with the copper/cobalt ore, the site was reputedly historically used to store ore from the Shinkolobwe uranium mine, the source of the uranium ore for the World War II Manhattan project. The radiological characterization was conducted via extensive gamma radiation surveys using vehicle-mounted sodium-iodide detectors, random grid composite soil sampling, biased soil sampling of areas with elevated gamma radiation levels, and sampling of surface water features. The characterization revealed broad areas of elevated gamma radiation levels of up to 160 μGy/hr in two distinct areas believed to be the Shinkolobwe uranium mine ore storage locations. Other areas, with gamma radiation levels of up to 80 μGy/hr, were detected associated with copper/cobalt ore refinery tailings and waste rock (overburden) sediments. The gamma radiation surveys revealed that elevated radiation levels were largely confined to areas previously disturbed by mechanized mining activities. Radiological contaminants in local surface water sources were within drinking water standards with the exception of one river heavily polluted with both uranium and other metals by waste streams from an ore processing and refining facility. Surrounding areas that appeared to be undisturbed by mining, including agricultural areas, native villages, and urban colonial-architecture cities, exhibited soil concentration and gamma radiation levels consistent with expected background levels.