The Akouta mine, the largest underground uranium mine in the world, is located in the Tim Mersoi sedimentary basin, a well-known uranium province in northern Niger. Two mines in the province, the Arlit mine since 1971 and the Akouta mine since 1978, provided the entire uranium production of Niger until 2011, when operations started at a third mine, Azelik. To date, more than 120,000 tU has been produced from the province.
In the Tim Mersoi basin, the uranium deposits are sandstone hosted and largely tabular with local roll front structures (Akouta). The deposits were formed by complex interaction between tectonic, lithologic and paleogeographic factors. They occur from surface to a depth of 250 m and the grade is relatively low, between 0.1% and 0.6% U. The Carboniferous formations of the Guezouman (Akouta) and Tarat (Arlit), the Jurassic formation of the Tchirezrine (Imouraren deposit) or the Cretaceous formation of the Assouas (Azelik deposit) host the ore bodies.
At Akouta, the deposit lies 250 m deep at the base of the Guezouman sandstone. The mineralization is 1 m to 15 m thick and nearly flat-lying, with an average grade of 0.4% U. The mining method is room and pillar with conventional drilling and blasting equipment. With this method, the miners are in direct contact with low-grade ore and suitable ventilation measures are utilized to reduce the risk of radiation exposure.
OURD, with the support of Japanese utilities, mining and trading companies, joined the French Atomic Energy Agency in 1970 in exploration and development activities in Akouta. Since 1978, OURD has provided uranium to Japanese utilities from its share of mine production. Until the Fukushima nuclear accident in 2011, uranium supplied by OURD from Niger accounted for about one hour of total daily electricity produced in Japan.