Overview

Deposit type

• Sedimentary
• Sandstone hosted

Summary:

Uranium mineralization in the Sat1 and Sat2 Area mostly occurs in the middle and upper parts of the Inkuduk aquifer. In the MPP Area, uranium mineralization is generally associated with the Mynkuduk aquifer.

The roll front mineralization is hosted by four horizons: the Middle Inkuduk; the Lower Inkuduk; the Upper Mynkuduk, and the Lower Mynkuduk horizons.

Regional structures in the Chu-Sarysu Basin have had some control in the development of the sedimentary facies and to the movement of uranium bearing groundwater forming the roll fronts. While the hydrostratigraphy of the Cretaceous formations are interpreted to be the primary control to mineralization, structure contour maps of the basement Palaeozoic rocks indicate that linear depressions in the surface may also play a role in overlying roll front development.

Oxidation and mineralization
Different lithologic and geochemical types have been studied to determine the total organic carbon and iron contents.

The zone of uranium mineralization is located along the geochemical barrier marked by the contact zone of partially oxidized rock and the reduced, primary grey-coloured rock. Iron oxides are nearly absent in this zone and organic carbon content is lower. Some associated pyrite, and sometimes carbonates can be present. Four geochemical host rock types have been identified at the deposit:
• diagenetically reduced grey sands and clays containing coalified plant detritus
• green-grey sands and clays, reduced both diagenetically and epigenetically by gley soil (anaerobic organic) processes
• non-reduced initially mottled sediments
• yellow-coloured lithologies that underwent stratal epigenetic oxidation.

The initial colours are typical of channel or flood-plain facies. Diagenetically reduced grey sands and gravel of channel facies are more favourable for uranium deposition compared to greenish-grey or grey-green sands.

Occurrence and development of facies of Upper Cretaceous continental mottled alluvial formation is controlled by syn-sedimentary structures consistent with the tectonic pattern of the basin. Structural-facies control of mineralization is clearly observed in mineralization of the lower Mynkuduk horizon but is less distinct in the upper horizons.

From observations of core, the redox boundary can be readily recognized by a distinct colour change from grey and greenish-grey on the reduced side to light-grey with yellowish stains on the oxidized side, stemming from the oxidation of pyrite to limonite and consumption of organic carbon.

The propagation of the oxidation fronts is affected by hydrostratigraphy (controlling fluid paths and velocities), and rock composition (controlling redox reactions). The implied groundwater movement direction was from the southeast to northwest, leading to the formation of oxidation tongues also oriented to the northwest. It gives rise to characteristic geometries of the redox fronts and associated mineralization described in more detail in the following section.

Geometry
The Inkai deposit has developed along a regional system of superimposed redox fronts in the porous and permeable sand units of the Chu-Sarysu Basin. The overall strike length of the redox fronts and related mineralization envelopes at Inkai is approximately 40 kilometres. The stratigraphic horizons of interest in the basin, located between 250 and 550 metres below surface, have a combined total thickness which ranges from approximately 200 to 250 metres. Four mineralized horizons are present within the Inkai deposit MA Area:
• The Middle Inkuduk in the northern, central and western portion
• The Lower Inkuduk in the northern, eastern and southern portion
• The Upper and Lower Mynkuduk stretching from north to south in the eastern portion.

Morphology in cross-section view
Roll-front morphologies are classified in five major groups:
• simple rolls, mineralization along the nose or edge of a single oxidation tongue, including the classic C-shaped rolls
• cascade type, where two or more superimposed oxidation tongues form overlapping rolls (stacked mineralization)
• adjacent type, where two or more tongues develop in the same level enclosing mineralization in between
• combined cascade-adjacent type
• tabular.

Mineralogy
Uranium
The main uranium minerals are sooty pitchblende (85%) and coffinite (15%). Sooty pitchblende occurs as micron-sized globules and spherical aggregates, while coffinite forms microscopic crystals. Both minerals occur in pores on interstitial materials such as clay minerals, as films around and in cracks within sand grains, and as pseudomorphic replacements of rare organic matter which is also commonly associated with pyrite. The pyrite is interpreted to have formed after the growth of pitchblende as it often coats or rims the uraniferous films and aggregates.

Other elements
Overall, elements of potential concern (EOPC) such as molybdenum (Mo), selenium (Se) and vanadium (V) occur in background levels consistent with average values for the Earth’s crustal rocks. However, elevated local vanadium and molybdenum values are sometimes observed where organic material has accumulated. Authigenic minerals includes pyrite, siderite, calcite, native selenium, chlorite, sphalerite, pyrolusite and apatite. Additional quantitative methods of analysis in mineralized and waste sands were used to study the content of rhenium, scandium, yttrium, and other rare earths.

Deposit Types
Roll-front deposits of the Chu-Sarysu Basin
The Inkai uranium deposit is a roll-front stratiform system. Roll-front deposits are a type of stratiform deposit that forms within permeable sandstones in localised reduced environments. Microcrystalline uraninite and coffinite are deposited during diagenesis by oxygenated and uraniferous groundwater, in a crescent-shaped lens that cuts across bedding and forms at the interface between oxidized and reduced lithologies. Sandstone host rocks are medium to coarse grained and were highly permeable at the time of mineralization.

The mineralizing system responsible for the formation of the uranium deposits in the Chu-Sarysu Basin is related to the rise of the Tien-Shan Mountains which started in the Oligocene and is still active today.

Mining Methods

• Solution mining

Summary:

Mining at Inkai is based upon a conventional and well-established ISR process. ISR mining of uranium is defined by the International Atomic Energy Agency as “the extraction of ore from a host sandstone by chemical solutions (lixiviants) and the recovery of uranium at the surface. ISL [ISR] extraction is conducted by injecting a suitable leach solution into the ore zone below the water table; oxidizing, complexing and mobilizing the uranium; recovering the pregnant (loaded) solutions through production wells (extraction wells or recovery wells); and finally, pumping the uranium bearing solution to the surface for further processing.”

ISR mining at Inkai uses a sulphuric acid based lixiviant. The mining process comprises the following components to produce UBS, which goes to settling ponds and then to the respective IX plant before being directed to the MPP for production of uranium as yellowcake:
• Determination of the GT cut-off for the initial design and the operating period. The design cutoff sets the minimum amount of uranium per pattern required to justify wellfield installation before funds are committed, and the operating head grade in UBS cut-off for individual producer wells that dictates the lower limit once a well has entered production.
• Preparation of a production sequence which will deliver the UBS to meet production requirements considering the rate of wellfield uranium recovery, UBS uranium head grades, and wellfield flow rates.
• Wellfield development using an optimal pattern design to distribute barren lixiviant to the wellfield injectors, and to collect UBS back to the MPP, Sat1, or Sat2, as the case may be.

The above factors are used to estimate the number of operating wellfields, wellfield patterns and header houses over the production life. They also determine the unit cost of each of the mining components required to realize the production schedule, including drilling, wellfield installation and wellfield operation.

Wellfield design and development
For ISR mining, the basic unit of production is a ‘pattern’ with an extraction well and associated injector wells. Economic patterns must cover the cost of well installation, connection of the wells to a piping system to carry the lixiviant to and from the IX plant, the cost of the chemicals needed to leach the uranium, the operating cost of the pumps and maintenance on the pumps, the downstream plant costs (elution, precipitation, filtering and drying), post-processing costs, and administrative overhead. While individual well performance can vary significantly, long-range scheduling assumes a general average flow using past production results which is deemed sufficient for predicting the behaviour of a large numbers of patterns.

Many factors can affect the design of the pattern, including:
• permeability of the host sands
• depth of the host sands
• cost of drilling
• thickness of the mineralized units
• surface topography
• target wellfield uranium recovery.

Where there are no historical operations to use as a baseline, extensive hydrological modelling may be required for wellfield design and production planning. This is not the case with Inkai, as there has been significant experience following the start of commercial production in 2009 to support the current production plan. Inkai uses both 7-spot (also known as hexagonal) and line drive patterns. In a 7-spot pattern, six injectors are located on the vertices of a hexagon with one extractor in its centre. The distances between the wells in a hexagonal pattern varies from 35 to 45 metres, with average distance of 40 metres. In line drive patterns, rows of injectors alternate with rows of extractors. The distance between rows varies from 50 to 65 metres. The distance between wells in injector rows vary from 20 to 25 metres and in extractor rows from 25 to 30 metres. The total injector to extractor ratio is approximately 2.6. The screen length varies from 3 to 15 metres, with 6 metres being the most typical target length. The horizontal and vertical patterns geometries depend

Mining Equipment
In ISR mining, ore is accessed through the wells. A total of 1,000 to 1,300 wells are required to be drilled, developed and equipped annually at Inkai. All of this work is contracted.

The surface infrastructure comprising of roads, overhead powerlines, acid lines, lixiviant and UBS pipelines, header houses and acidification units are required to be developed to deliver lixiviant, acid and electric power to wellfields and UBS to the processing facilities. A total of 20 to 25 wellfields are required to be developed annually.

Most wellfield construction is carried out by Inkai using its own equipment. Submersible pumps installed in each extractor well are used to lift UBS from the productive horizons and to maintain the required flowrate to transport it to the processing facilities. A total of 350 to 550 extractors are required to work at any given time to achieve the target flowrate. All submersible pumps are owned by Inkai.

Wellfield production
Production objectives
The annual production target of 10.4 million pounds U3O8 requires a combined flow of approximately 5,680 m3/h and an average head grade of approximately 100 parts per million of uranium delivered to the IX columns. Flow capacity within individual production wells generally vary between 8.0 m3/h and 10.5 m3/h on average resulting in approximately 550 patterns required to be in operation to achieve the required flow to the IX circuits. Wellfields are typically in production for two to five years.

Comminution

Crushers and Mills

Processing

• Sulfuric acid (reagent)
• Resin adsorption
• Elution
• Dewatering
• Filter press
• In-Situ Recovery (ISR)
• Ion Exchange (IX)

Summary:

The process consists of the following major steps:
• uranium in situ leaching with a sulphuric acid-based lixiviant
• uranium adsorption from UBS with IX resin
• elution of uranium from resin with ammonium nitrate
• precipitation of uranium as yellowcake with hydrogen peroxide and anhydrous ammonia
• yellowcake thickening, dewatering, and drying
• packaging of dry yellowcake product in containers

There are three surface processing facilities at Inkai: MPP, Sat1 and Sat2. The processing equipment in the MPP circuit currently includes IX units (adsorption and elution columns), along with yellowcake precipitation, thickening, drying and packaging process units. The processing equipment at both Sat1 and Sat2 consists of adsorption and elution equipment. The MPP currently produces a uranium peroxide (UO4·nH2O) dried product from the UBS. Periodically, when there is a shortage in drying capacity, eluate from the process circuit is shipped to a toll mill for processing to U3O8. Planning continues related to upgrading the drying circuit to produce U3O8 by processing the uranium peroxide in an electrically heated rotary calciner.

Loaded IX resin is produced from UBS and is eluted at the MPP, Sat1 and Sat2 processing plants. All eluate from Sat1 and Sat2 is be transported to the MPP for the production of uranium peroxide.

The following demonstrated capacity estimates are based on periods when higher head grades have been attained during production in the specific block. The existing MPP, Sat1 and Sat2 circuit capacities were estimated using Inkai monthly process summaries. The MPP has demonstrated an IX capacity of 2.7 million pounds U3O8 per year and a product drying and packaging capacity of 8.3 million pounds U3O8 per year. Sat1 has a demonstrated IX capacity of 6.3 million pounds U3O8 per year as eluate. The current demonstrated IX capacity of Sat2 is 4.5 million pounds U3O8 per year as eluate.

Plans are progressing to install filtering, drying and calcining circuits at the MPP to support planned production levels of at least 10.4 million packaged pounds per year.

Engineering work for a process expansion of the Inkai circuit to support a nominal production of at least 10.4 million pounds U3O8 per year has been completed and construction is in progress. The expansion project includes an upgrade to the yellowcake filtration and packaging units, and the addition of a pre-dryer and calciner. Inkai estimates the completion of the expansion project in 2025, subject to it successfully managing the schedule risk related to contractor performance.

Ion exchange resin adsorption (loading)
Wellfield acid solution, containing the leached uranium (UBS), is pumped from the selected wellfield(s) via pipelines to a settling pond and then to the IX circuits for adsorption of the contained uranium. The uranyl sulphate anions are selectively adsorbed onto solid synthetic IX resin beads with fixed ionic sites. The resin bed is retained in IX vessels where resin is contacted with UBS.

Once the resin in an IX column is fully loaded with uranium, the column is isolated from the continuous IX circuit and the resin is retained for elution or transferred with push water to an elution vessel. In the case of the MPP, the UBS can be directed to one of the adsorption column trains. Each train is capable of performing resin adsorption and then operated in the desired mode of elution. In the case of Sat1, the UBS reports to either an adsorption column train or a semi-batch adsorption column. In the case of Sat2, UBS solution reports to a semi-batch adsorption column.

Resin elution (stripping)
In the elution process, uranium that has been adsorbed onto the IX resin during the adsorption cycle (loaded resin) is desorbed from the resin using ammonium nitrate. The eluate produced from this step is stored in tanks.

At the MPP and Sat1, loaded resin can either be retained in the vessel for elution or hydraulically conveyed to a vessel specifically designed for elution within the circuit. Loaded resin can also be transferred between the two plants for elution based on available capacity. At Sat2, loaded resin is hydraulically transferred from the adsorption vessel to an elution vessel.

Denitrification
After the uranium has been stripped from the resin in the elution process, the adsorption sites on the resin are initially left in a nitrate form. The adsorption sites on the resin must be denitrified and converted to a sulphate form for re-use in the IX circuit. This is accomplished by contacting the resin with a solution of sulphuric acid and process water in a denitrification vessel. Each plant has a denitrification vessel to complete this step.

Precipitation
Eluate from Sat1 and Sat2 is transported to and stored with the MPP eluate before being directed to the precipitation circuit. Hydrogen peroxide is added to the precipitation tanks to induce precipitation. The pH of this stream is adjusted within the tank through the addition of anhydrous ammonia. The tanks are operated in a cascade configuration to allow the required retention time for the precipitation reaction to proceed to completion. The final yellowcake slurry is discharged from the last tank in the series and pumped into a thickener.

Yellowcake product thickening
The slurry from the precipitation circuit is pumped into a thickener where the contained yellowcake slurry is thickened to approximately 35% solids and pumped to filter presses for further dewatering and cake washing.

Filter press operation
The yellowcake slurry from the yellowcake thickener underflow reports to the filter presses. The slurry is first washed and then dewatered in the filter presses to approximately 65% solids.

Drying
The dewatered yellowcake from the filter press is then pumped into rotary vacuum dryers where the yellowcake product is produced.

The vacuum dryers are totally enclosed during the drying cycle to assure zero emissions. The offgases and steam generated during the drying cycle are filtered and condensed to collect entrained particulates and moisture within the process system.

Packaging
Once the dryer contents have cooled, a measured amount of dried yellowcake is transferred through a rotary valve into drums before being shipped.

Overall uranium recovery
The uranium extraction efficiency (recoverability) of ISR operation is determined by uranium loss in underground leaching and in surface production facilities. Plant recovery of the uranium from the UBS has averaged approximately 98% since 2015. Based on the blend of feeds from the various wellfields over the LOM, an overall uranium recovery, or metallurgical recovery, of 85% is expected for the remainder of the LOM plan.

Expansion project
Engineering work for a process expansion of the Inkai circuit to support a nominal production of at least 10.4 million pounds U3O8 per year has been completed and construction is in progress. The expansion project includes an upgrade to the yellowcake filtration and packaging units, and the addition of a pre-dryer and calciner.

Following completion of the expansion project, total expected production capacity is expected to be approximately 13 million pounds per year from leaching and IX, and approximately 12 million pounds per year from calcining and packaging.

Following completion of the expansion project, the use of toll milling services to reach annual packaged production targets is not expected to be required.

Water Supply

Summary:

Inkai has access to sufficient water from groundwater wells for all planned industrial activities. Potable water for use at the camp and at the site facilities is supplied from shallow wells on site drawing from the Uvanas Aquifer while industrial use water is drawn from the Zhalpak Aquifer. The water systems include well houses, pump stations, storage for reserve demands and fire protection and distribution to points of use and fire protection mains. Sewage disposal is in a standard septic tank and leach field system.

The main impact of the Cameco’s activities on water resources is the volume of water consumption. But this factor is also minimised, since the production facilities use technologies for the multiple reuse of industrial water, thereby increasing the volume of recycled water.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Chief Geologist	Alain D. Renaud		Feb 25, 2025
Chief Metallurgist	Biman Bharadwaj		Feb 25, 2025
Deputy General Director, Operations	Anselme Diracca		Feb 25, 2025
Deputy General Director, Technical Services	Sergey Ivanov		Feb 25, 2025
Health, Safety & Environment Director	Kanat Moldakhymetov		Feb 25, 2025