資源地質，63(2), 81 ～ 90, 2013

現場担当者会議講演論文

The Akouta Underground Uranium Mine, : A Review of Operations

Philippe CROISY*, Hiroyasu MURAOKA* and Tomio HAMAI*

Abstract: The Akouta mine, the largest underground uranium mine in the world, is located in the Tim Mersoi sedimen- tary basin, a well-known uranium province in northern Niger. Two mines in the province, the 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 Carbon- iferous 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 Agen- cy 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.

1. Introduction

The Akouta mine in Niger is located in the prefecture of Agadez, at the southern edge of the Sahara and is 850 km northeast of the capital . The mine is 60 km from the border of the Air Mountains and 10 km southwest from the town of Arlit (Fig. 1). The city of Akokan, 5 km northeast of the mine, was developed to house its workers and is accessible either by airplane (a 2 hour flight from Niamey) or by road. All infrastructure including housing, roads, airport and communications system in the area was developed to support the start of mining activities. Electricity is provided by the SONICHAR coal power plant, 160 km south of the mine. Mining facilities (Fig. 2) in Akouta are located near the entrance of the mine. The natural environment in the region is harsh; a desert with temperatures reaching 50º C in summer. Precipitation Fig.1 Map of Niger.

2013 年 4 月 3 日受付，同年 4 月 3 日受理 日本鉱業協会 平成 25 年度全国鉱山・製錬所現場担当者会議 (2013 年 6 月 12 日，東京 ) にて講演 * Overseas Uranium Resources Development Co., Ltd. (OURD), 2-6-15 Shibakoen Minato-ku, Tokyo, 105-0011, Japan Keywords：Niger, Akouta, uranium, sandstone deposit, room and pillar mining, radiation protection

81 82 Philippe CROISY, Hiroyasu MURAOKA and Tomio HAMAI 資源地質：

Fig.2 Akouta mill.

Fig.3 Simplified geological map of Niger (from World Nuclear Association document) is very low, with the majority of annual precipitation (150- develop the underground mine at Akouta, where the first 250 mm) occurring between July and September. drum of was produced in 1978. Since then, over 65,000 tU has been produced in Akouta from five Exploration for uranium started in the 1950's when the different deposits, from north to south: Akola, Akouta country was still under French colonial rule. The French North, Akouta South, Ebba North and Ebba South. By the Overseas Mining Bureau (BUMIFOM) discovered uranium end of 2012, more than 120,000 tU has been produced showings in 1957 in the . The French Atomic from the two mines. Energy Agency (CEA) then started detailed exploration The current shareholders of COMINAK are AREVA by airborne geophysical and ground geological surveys (34%, France), SOPAMIN (31%, Niger), OURD (25%, and drilling leading to the discovery in 1959 of the Azelik Japan) and ENUSA (10%, Spain). deposit. This was followed by the discoveries of the In 2010, Niger was ranked as the 5th largest uranium Madaouela deposit in 1963, Arlit in 1965, Imouraren in producer in the world with an annual output of 4,197 tU 1966 and Akouta in 1967. (Source, OECD, Red Book 2011) and is expected to rank 3rd In 1968, SOMAIR (Société des Mines de l'Aïr) was from 2016, with the start of Imouraren (5,000tU/y). incorporated to develop the Arlit deposit as an open pit mine and in 1971 Niger joined the select group of world The Nigerien Mining Law was revised in 2007 and uranium producers. This was followed by the creation in the government liberalized the acquisition of exploration 1974 of COMINAK (Compagnie Minière d'Akouta) to permits to attract foreign investment. This brought several 63(2), 2013 The Akouta Underground Uranium Mine, Niger: A Review of Operations 83

The crystalline basement, which formed during the PanAfrican orogenesis consists of metamorphosed rocks, essentially metasediments, intruded by granites. Recognized lithologies include biotite gneiss, leptynitic gneiss and micaceous shale with quartzite and amphibolite. The granite intrusions are syntectonic with the main phase of deformation occurring during the PanAfrican orogenesis. The magmatic activity did continue with post-orogenesis granite intrusions during the Ordovician, Carboniferous and Jurassic. Volcanic activity also occurred during the Tertiary and Quaternary periods. The sedimentary cover of the Tim Mersoi basin, a sub-basin of the Phanerozoic Iullemmeden basin, a vast structural depression of 640,000 km2 which developed on the West African shield basement, consists of a succession of marine to continental sediments and includes rocks ranging from Cambrian-Silurian to Miocene. The thickness of the sediments can reach over 2,000 m; in the Akouta region it varies from 400 to 800 m.

The stratigraphy of the eastern part of the Tim Mersoi basin, as established by Cazoulat (1984, Fig. 4), is divided (from bottom to top) into four main sequences: - The Lower Visean formations of the Terada Group which consists of the coarse to conglomeratic sandstones of the Teragh and the marine clays of the Talak. - The Upper Visean formations of the Tagora Group, which includes two series starting with a fluvio- deltaic period, followed by a marine to epicontinental sedimentation and ending with a lacustre-alluvial period. The Lower Tagora consists of the Guezouman medium to coarse sandstones and the Tchinezogue Fig.4 Stratigraphy of the East Tim Mersoi basin argillites and fine sandstones. The Upper Tagora (from Cazoulat, 1984). consists of the Tarat medium to very coarse sandstones, the Madaouela silts and the argillaceous new mining companies to start exploration or development sandstones and lacustrine shales of the Arlit formation. projects. Although security in the Sahel region is a concern - A sequence called the "Continental Intercalaire" from and increasing costs could have an impact on the ongoing Permian to Jurassic, which consists mainly of fluvial projects, the region remains prospective for the discovery sandstone sediments with intercalation of lacustrine of new deposits. argillites. - The Lower Cretaceous which consists of the Irhazer 2. Geological Settings shale formation, with the silts and fine sandstones of the Assaouas at its base. 2. 1. Regional Geology

The geology of the Agadez region is dominated The deposits of Akouta and Arlit are hosted in the by the Proterozoic basement of the Air massif and the Upper Visean Carboniferous formations of the Guezouman intracratonic Tim Mersoi sedimentary basin (Fig. 3). and Tarat respectively. The Guezouman sandstone 84 Philippe CROISY, Hiroyasu MURAOKA and Tomio HAMAI 資源地質：

Fig.5 Arlit area structural geology (left) and Akouta mine deposits (right). also hosts the Madaouela deposit. The "Continental paleochannels, favourable uranium traps. Intercalaire" Jurassic formation of Tchirezrine and the Geological host formations are gently dipping Lower Cretaceous formation of Assouas host the ore bodies southwestward and lie 150 m deeper to the west of the Arlit of Imouraren and Azelik. fault. All known economic deposits are located east of the fault. 2. 2. Structural Geology The main structural feature of the Tim Mersoi basin is 3. Deposit and Ore Mineralogy the north trending In Azawa lineament - Arlit fault, which 3. 1. Akouta Deposit Formation extends over hundreds of kilometers through the basin to Algeria. The Air massif basement is strongly folded and A generally accepted model for deposit formation is influenced by two major structures, oriented N20-N30 and a pre-concentration of the mineralization controlled by N135 degrees. In the Arlit area, the N20-N30 direction tectonic, lithologic and physico-chemical factors with is predominant and corresponds to the main lineation and remobilization triggered by the Arlit fault. Ore bodies at the structural feature (Fig. 5). Arlit deposit are located at the intersection of main N-S The deformation of the sedimentary cover is the result and NNE-SSW structures and paleochannels. of basement faulting, with several of the N30 lineaments The Guezouman formation was deposited in a fluvio- offset by N80 structures. The N30 flexures are the direct deltaic environment with the supply of detrital grains result of the vertical displacement of the Arlit normal fault, eroded from the Air massif. Aqueous fluids transported active during the sedimentation phase. These structures, organic matter and plant debris during this period. at the base of the Guezouman sandstone, played a major These materials accumulated on the border of the main role in the formation of a major synclinal axis and paleochannels oriented N80 degrees and syngenetic 63(2), 2013 The Akouta Underground Uranium Mine, Niger: A Review of Operations 85

Fig.6 Ebba zone - W-E vertical cross section. mineralization occurred in this zone. Faulting during - The upper unit corresponds to an alternate sequence sedimentation also had a strong influence on mineralization of white carbonaceous fine sandstones and grey clay- control. During the Jurassic period, the movement of the silts; this unit is often altered. Arlit fault triggered the circulation of hot oxidized fluids 3. 3. Source of Uranium and Mineralogy from the west to the east. According to Forbes (1989), these fluids were enriched in U that precipitated along A possible major source of uranium is the detrital paleochannels, in the redox fronts formed at the contact of grains from the erosion of Air crystalline massif. A oxidized and reduced zones. Syngenetic uranium was also secondary source is the volcanic activity between the oxidized and remobilized. Upper Carboniferous and Jurassic periods. In Akouta, five mineralizing phases have been 3. 2. Host Formation: Guezouman Sandstone distinguished by Forbes (1989): (1) an early replacement The Guezouman thickness varies from 40 to 70 m and of wood fragments by pyrite and formation of quartz is composed of three units: overgrowths on detrital quartz grains; (2) a sulphate - The lower unit corresponds to the Teleflak conglomerate phase with formation of barite; (3) the U-Mo-V- and is composed of numerous clays, rhyolite, quartz Zn-Zr deposition phase; (4) the alteration of feldspars pebbles, phosphorous gravels and organic debris and formation of kaolinite on the west side and (5) the cemented by pyritic and ferruginous quartz. This unit is, formation of iron oxides and manganese rich-cements. however, not always present at the Akouta deposit. Uranium occurs essentially as pitchblende and minor - The intermediate unit consists of deltaic iso-granular coffinite, Isotopic dating on pitchblende samples has given and mid-grained sandstone, grey to light grey in an age of mineralization between 150 Ma and 200 Ma. colour, pyrite rich and cemented by calciceous clays. The presence of significant amounts of Zr associated When the Teleflak conglomerate is not present, the with Mo, V and Zn suggests an alkaline volcanic source for contact with the underlying Talak formation consists these elements (Pagel et al, 2005) Isotopic dating has given of grey- black carbonaceous coarse sandstone, an age including organic matter and is very calciceous. 3. 4. Deposit Characteristics Economic mineralization is always hosted at the base of this unit (Fig. 6). The Akouta mine, with over 250 km of galleries, is the 86 Philippe CROISY, Hiroyasu MURAOKA and Tomio HAMAI 資源地質：

Table 1 Akouta Mine Deposits Ore Content (2011 Estimation). Deposit Ore M(t) Grade(%) U(t) Akola 5.9 0.49 29,200 Produced Ore Tonnage Akouta North 6 0.43 25,800 Akouta South ≧4.0 ≧0.30 > 12,000 Under production Ebba North ≧3.0 ≧0.30 > 9,000 Tonnage Estimation Ebba South ≧4.0 ≧0.30 > 12,000

Akouta Mine Uranium Production (tU) 2500

2000

1500

1000

500

0 1980 1985 1990 1995 2000 2005 2010

Fig.7 Uranium Production at the Akouta mine.

largest underground uranium mine in the world. The N-S Past and recent exploration over the permit areas has distance is 9 km and the maximum lateral extension is led to the discovery of numerous prospects such as: Akola about 2 km. West, Ebene and Moradi. The company is investigating Mining at Akouta started with the development of these prospects and extensions of known deposits by the Akouta North deposit. The mine has progressively drilling at a 50 m to 200 m spacing. The yearly drilling been developed northwards to Akola and southwards to meterage ranges from 30,000 m to 40,000 m; rotary mud Akouta South, Ebba North and Ebba South deposits. The drilling is utilized. Since 1978, over 1,100 km of drilling mineralized horizon averages 3 m in thickness and is has been completed. gently dipping to the south. In some areas, this horizon can contain 3 layers: the main (or lower), the central and the In the Tim Mersoi basin, the selection and determination of upper layer. Ore tonnages and grades tend to decrease to prospective zones is based on the following three factors: the south (Table 1). - paleochannels and redox fronts The Akola deposit was mined from 1988 to 2010 with - structures (faults, synclines) more than 29,200 tU ([email protected]% U) extracted.The - geological formations hosting economic mineraliza- Akouta North deposit was mined from 1978 to 2000 and tion (Guezouman, Tarat, Tchizerine) more than 25,800 tU (6Mt@ 0.43% U) was extracted. The remaining crown pillars are expected to be mined before Three stages of exploration can be defined as: mine closure. The Akouta South, Ebba North and Ebba - Initial reconnaissance stage or greenfield exploration: South deposits are under production at this time consists of airborne geophysical surveys, ground geological reconnaissance, rock sampling, 4. Exploration and Development Drilling geochemical analysis, radon soil survey followed by large scale reconnaissance drilling with a few hundred At the current production rate, 15 years of reserves meters to a few kilometers spacing grid. have been confirmed and COMINAK is continuing with - Advanced greenfield exploration: includes a more exploration and development drilling on its properties (204 intensive medium to closely spaced drilling program km2) to find additional resources. in prospective zones, generally at a spacing of 200 63(2), 2013 The Akouta Underground Uranium Mine, Niger: A Review of Operations 87

Fig.8 Room and pillar mining (modified from COMINAK internal document).

m to 800 m. This allows for a better assessment of - The room development which consists of a 6 m wide the geology, location of paleochannels, definition of drift and 6 m crosscut with a minimum opening height targets for the next phase of drilling, associated with of 2.5 m. This removes about 40% of the ore and the mineralized intersects. leaves 18 m by 18 m pillars. - Brownfield exploration: exploration or development - The retreat pillar mining is carried out back towards drilling at a 50 m to 200 m grid spacing. the access drifts. During this phase, the remaining pillar is mined in two different ways depending on the Borehole geophysics (radiometric, resistivity) is also uranium grade. performed after drilling. Ground geophysics is not effective - Retreat pillar with no backfilling (lower grade in the search for tabular deposits. panels): two perpendicular cuts in the center of the pillar remove an additional 33% of the ore and 5. Mining four 6 m wide crown pillars are left. Backfilling is not performed and bolts of 1.8 m are fixed for roof Two parallel declines of 1,300 m, inclined at 20%, with stability. an opening of 20 m2 provide access to the Akouta North - Retreat pillar with backfilling (cut-off depending on deposit at 250 m depth. The eastern decline is used for ore economics): the pillar is completely mined and the passage of personnel and equipment and the western backfilled and 100% of the ore is extracted. First, a 6 decline for ore extraction on a conveyor belt. From the m cut in the middle of the pillar is achieved and, after bottom of the declines, two galleries provide access to the backfilling, the two lateral sides of the pillar are mined production stopes of the main (or lower) mineralized layer. and backfilled. Drifts are also backfilled during the In deposits with a mineable central and upper layer, an retreat. upward ramp links the main layer to these layers From the mining face, the blasted ore is transported to The room and pillar mining method is used with the panel loading platform, then hauled by LHD or dump conventional mechanical equipment that includes drilling truck to the primary crusher. The ore size is crushed to machines, jumbos, bolting machines, Long Haul Dump 0-250 mm to feed directly the mill or the ore stockpile (LHD) and dump trucks. The mining cutoff grade is 0.2% area. U. Backfill material is made from a low cement content Each deposit is divided into blocks and the development of (3-4%) sandstone (granulometry 0-40 mm) and water. panels takes place in two phases (Fig. 8): The backfill paste is sent underground by gravity through 88 Philippe CROISY, Hiroyasu MURAOKA and Tomio HAMAI 資源地質：

Fig.9 Milling process flow (modified from IAEA document).

dedicated vertical shafts and loaders haul the paste to the The pugged ore is cured for 2.5 hours on a series working face. of two 100 m long conveyor belts, then re-pulped with water in 5 successive tanks at a temperature of 65o C to 6. Milling obtain a solid to liquid ratio of 1:1. The pulp is washed with water and filtered on a series of two filter bands. The COMINAK's mill has a capacity of 2,000 tU/year pregnant solution filtered from the first series of filters with an acid plant of 200 tA/day. The ore is processed is sent for clarification. The solid cake generated by the dynamically; acid leaching with solvent extraction is used second filtration is transported to the tailings area while the for uranium recovery (Fig. 9). pregnant solution, recycled to wash the pulp on the first series of filters. The size of ore, crushed underground to 0-250 mm, After clarification, a five stage mixer-settler system is reduced to 0-550 μm in the autogeneous mill before is used to extract uranium and solvent from the solution feeding the leaching tank at a rate of 100 t/h. Sulfuric and another five stage mixer-settler system for solvent acid mixed with nitric acid, sodium nitrate as an oxidant stripping. The uranium solution stripped from the solvent and water are added in the tank. The acid consumption is sent to the uranium precipitation stage. Sodium averages 100 kg/t and sodium nitrate 2.3 kg/t, respectively. carbonate is added to the remaining stripped solvent (a During this process, the oxidation reaction generates sodium chloride solution) in a three stage mixer-settler nitrogen oxides (NOx) which is mixed with water in the unit where molybdenum and impurities are eliminated absorption tower, producing nitric acid. The nitric acid is and the solvent is recycled. Magnesia milk is added to the recycled to the leaching tank and provides about 85% of uranium solution. The final product, called yellowcake, is a the oxidant requirement. magnesium diuranate (MgU2O7) containing 75% uranium. 63(2), 2013 The Akouta Underground Uranium Mine, Niger: A Review of Operations 89

The uranium recovery rate of the milling plant averages the remaining products are transported and stocked in 93%. dedicated sewage ponds. The dried yellowcake is packed into 220 liter drums 7. 2. Radiation Protection before shipping. The drums are transported by road from Arlit to the port Cotonou in Benin, about 2,000 km COMINAK puts a high priority on protecting the southwest, and shipped to AREVA's Comurhex conversion workers' health and safety, reducing the industrial and plant in Southern France, where MgU2O7 is converted into environmental risks. Since 2006, the Niger law has uranium hexafluoride (UF6) gas. imposed a maximum exposure level of 20 mSv/y for Minor production of uranium from low grade ore is nuclear workers. COMINAK has adopted even lower also obtained by heap leaching. standards with a limit of 16 mSv/y and follows the ICRP In 2012, the annual production at Akouta totaled 1,506 60 recommendations. tU. With the adoption of the room and pillar method, miners 7. Water Treatment and Radiation Protection are in direct contact with the ore body and different measures must be taken to reduce their exposure risks: Two of the main challenges encountered during the - gamma radiation from minerals (external exposure) daily operations at Akouta are the containment of mine - radon progeny (internal exposure) water and its treatment, as well as the safety of workers - long-lived radioactive dusts (internal exposure). against radiation. Each miner wears an individual dosimeter which measures parameters associated with the three above risks. This 7. 1. Water Treatment dosimeter includes: Industrial water used for the operations comes from - an air sampler associated to a battery powered the Tarat aquifer, also the source of potable water in the centrifugal pump, district, and from the mine. - an integrated head for the measure of short-lived descendants of radon 222 and 220 isotopes and long- 7.1.1. Mine Water lived alpha emitters from uranium and thorium chains. In the mine, water comes principally from three Long-lived alpha emitters in the airborne dust are sources : collected on the sampling filter. A thermo luminescent - the ventilation shafts that cross the Tarat aquifer detector in the head collects equivalent doses from - the exploited Guezouman formation gamma ambient radiations. - the water used during mining operations These parameters are controlled every month. The inflow of mine water reaches 200-250 m3/h and is the cause of numerous problems for the underground To reduce the risks, the following measures have been operations. One of the main issues encountered is the implemented: formation of mud in the galleries, particularly in areas - isolation of the belt conveyor where clays from the underlying Talak formation has been - spray water during mining and in the access galleries excavated. The mud increases corrosion and can damage to direct dust toward the ground equipment. - increase the number of ventilation shafts The mine water is collected in underground sumps - erect barriers in the production panels to improve for decantation and pumped to the surface ponds, where airflow it is also treated by decantation. Mineralized fines and - strict respect of ventilation standards impurities deposit at the bottom of the ponds and the water - strengthen controls collected is recycled as industrial water. - increase employees education about adequate behaviors 7.1.2. Water from the Mill All these measure have a positive impact in strongly Industrial water used in the mill and effluents is reducing the radon progeny and long-lived radioactive collected and stocked in surface ponds (11 ponds for a dusts risk. Gamma radiation accounts for half of the risk. surface of 65 ha, 2.6 Mm3). This water evaporates and 90 Philippe CROISY, Hiroyasu MURAOKA and Tomio HAMAI 資源地質：

Primary ventilation is assured by vertical shafts of 2.4 References m, equipped with 30 kW ( ～ 35 m3/s) or 55 kW ( ～ 50 m3/s), for a total airflow of 2000 m3/s. Measurements of Cazoulat, M. (1985) Geology environment of the radioactive pollutants and air quality are done continuously uranium deposits in the Carboniferous and Jurassic in the mine. Regular controls and countermeasures to sandstones of the western margin of the Air Mountains protect from radiation exposure are also done in the mill in the Republic of Niger. Geological environments and sensitive areas of the industrial zone. A network of 11 of sandstone- type uranium deposits, IEAE- stations around the mining site and in Akokan monitor air TECDOC-328, 247-263. quality and the impact of mining activities. Water quality Carisey, J.C. Geology of COGEMA's uranium deposits in and emissions of CO2, NOx, SOx and COV and also Niger and Gabon. closely monitored. Chagnes, A., Cote, G., Syna, N., Courtaud, B. and Thiry, J. (2012) Review on Uranium Recovery 8. Conclusions from COMINAK Ores: Problems and Assessments. IMPS 2012, The International Mineral Processing The Akouta mine is the only underground mine in Symposium, Bodrum, Turkey, October 10-12, 2012. Niger and has been operating continuously for the past 35 COMINAK (2002) Etude de faisabilité Afasto. Internal years. COMINAK has developed high level experience in Report. the room and pillar mining method and the company puts Dahlkamp, F. (1993) Deposits. Springer- a high priority on maintaining and improving the level of Verlag, 84-94. operations, safety of employees and particularly reducing Forbes P. (1989) Rôles des structures sédimentaires the radiation exposure risk. et tectoniques, du volcanisme alcalin régional et OURD has been an active joint venture partner in des fluides diagénétiques-hydrothermaux pour la Niger for more than 40 years and continues to contribute formation des minéralisations à U-Zr-Zn-V-Mo towards the Akouta operations to insure the safety, stability d'Akouta (Niger). Thèse de l'Université de Bourgogne, and improvement of mining activities. 375 p. Fukuda, M.(1980) Projet Afasto- Ouest, Rapport As the geological attributes of the Tim Mersoi basin synthetique pour fin de campagne. OURD internal are favorable for more discoveries, the ongoing exploration document. efforts by junior and major companies, coupled with the IAEA (1993) Uranium Extraction Technology. Technical change in the Mining Law in 2007, will hopefully lead to Reports Series No.359, 104-108, 327-331. additional new deposits and their development into open OECD (2012) Uranium 2011: Resources, Production and pit and underground mines. The experience and knowledge Demand. 60, 337-345. gained at Akouta will therefore benefit the mining industry Pagel, M., Cavellec, S., Forbes, P. et al (2005) Uranium in the country. deposits in the Arlit area (Niger). Mineral Deposit Research: Meeting the Global Challenge. Springer, Acknowledgements New-York, 303-305. The authors thank COMINAK, especially Mr. Salze, D., (2008) Etude des interactions entre uranium Michel Capobianco, President, and Mr. Mahamane Sidi, e t c o m p os és o rg a n i q u es d a n s l es s ys t è m e s General Secretary, for providing valuable documents and hydrothermaux. Thèse de l'Université Henri Poincaré - information for the preparation of this paper. The authors Nancy 1, 131-242. also thank Mr. Suraj Ahuja, Geological Consultant, for his Souley, M. (2005) AREVA in Niger, a long term uranium insightful review and advice. producer. International Symposium on Uranium Production and Raw Materials for the Nuclear Fuel Cycle–Supply and Demand, Economics, the Environment and Energy Security. IAEA Conference, Vienna, Austria, June 20-24, 2005. Proceedings of an international symposium, 225-234.