IAEA-SM-362/37 WASTE MANAGEMENT IN URANIUM COMPANIES OF NIGER Mining Company of Akouta (COMINAK), Akouta, Agadez II 111 I II III 111 lllllll Mining Society of Air (SOMAIR), Arlit, Agadez XA0055932 Niger Two companies produce uranium (yellow cake) in Niger: the "Societe des Mines de l'Ai'r (SOMAIR)" and the "Compagnie Miniere d'Akouta (COMINAK)". SOMAIR exploits uranium an open pit mining whereas COMINAK exploits an underground mining. The uranium ores with a grade of 0.25%U to 0.5%U [1] are treated by SOMAIR and COMINAK mills since 1971 and 1978 respectively. During the uranium recovery processing the principal following inputs are used: uranium ores, sulphuric acid (75 kg/t to 80 kg/5), nitric acid (10 kg/t recycled), sodium oxidant (2.5 kg/t) and water (150 l/t) [2]. The main chain of mining and milling is the following: Mining • Crushing • Leaching —• Solid-Liquid separation —*• Solvent extraction —• Uranium recovery —• Tailings management. The wastes produced (from mining and milling) can be classified as liquid wastes and solid wastes. The first one (liquid wastes) is of two kinds: wastewater and other liquid effluents. The wastewater is decanted for reuse in mills (COMINAK uses 16 basins with 4m of depth on an area of 44 ha to treat 3.4 millions mVyear [3]). Other liquid effluents are stored in basins of evaporation (COMINAK which has produced a volume of 2.18 millions m3 used 11 basins with 4 m of depth on an area of 65 ha against 10 ha for SOMAIR [3])- The solid wastes are barren overburden, low grade uranium ore and tailings mill. For example COMINAK produced in 1997 the following solid wastes [3]: • Low grade uranium ore: 423 561 tn with 0.14%; • Residues of lixiviation: 401 894 tn (till 1990); • Mill solid wastes: 9 millions of tons. The management of wastes must minimise the environmental and health impacts. Thus, against seepage, each basin is lined with an impervious PVC membrane. The basins are situated about 2 km from the mill, in a clayey zone which provides additional protection against any contamination of the underlying acquifer. The control of hydraulic gradient is made by piezometry. The NOg vapours created in leaching step are collected and contacted with water to generate nitric acid. Tailings need safe management as they contain long lived uranium and its daughters, some of which, especially radium, are toxic. Unless controlled, radium may escape from the tailings and, with its decay products, contribute to contamination and radiation exposure in the environment. The emanation of radon and thoron with their long lived daughter products is the basis of the problem posed by mill tailings. So to find solution to this problem a pilot project to recover mill tailings has been created. 148 The project will test what recovered materials can be used to reduce radon emanation levels from the sold waste to acceptable levels compared to natural background levels. These levels were not measure prior to operations beginning and thus waste rock of low specific activity will be used. The process to be adopted ;will be iterative as follows: • Trial perimeter is defined; • Points of radon measurement are identified by co-ordinate; • A first measurement was carried out on all points; • Cover material is put in place to a known height; • Repeat the first measurements at the same points; • Comparisons are made with the first measurement to determine the degree of attenuation; • The process is repeated until acceptable levels are achieved. COMINAK and SOMAIR have to ensure the safety of workers, to respect and ensure the protection of population and environment having regard to Niger mining law 31 MMII of the 79-12-5. An environment group which has responsibility to control waste management activities and provide for environmental protection was recently created in 1998. REFERENCES [1] MANAGEMENT OF RADIOACTIVE WASTE FROM EXTRACTIVE INDUSTRIES IN NIGER REPUBLIC (IAEA/CN/78/95) R. ABDOU. [2] URANIUM EXTRACTION TECHNOLOGY, IAEA, VIENNA, 1993. [3] AUDIT ENVIRONMENT COMINAK, MARCH 1998. 149.