2013/03/12 sheep mountain project heap leaching technology ... · 3/13/2013 6 11 energy fuels inc....

3/13/2013

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13 March 2013

SHEEP MOUNTAIN PROJECT

HEAP LEACHING TECHNOLOGY & ONGOING TESTWORK

Meeting with the U.S. Nuclear Regulatory Commission (NRC) ‐ Washington, D.C.

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ENERGY FUELS INC.

Heap Leaching Technology & Sheep Mountain Ore Testing

Overv iew

Heap Leach Pad Technology: Types of heap leach pads Project design criteria Ore characteristics

Sheep Mountain On‐going Ore Characterization: Consideration of agglomeration Geotechnical testwork under saturated and unsaturated

conditions Column leach testing

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Heap Leach ing ‐ Genera l

Excellent reference: Hutchison & Ellison (eds.), 1992, Mine Waste Management,

654 pp. Chapter 9 – “Heap Leaching”

Applicability of current regulations to heap leaching: After leaching, the processed uranium ore on the Heap Leach

Facility (HLF) will become 11e.(2) byproduct material As such, most regulations pertaining to uranium tailings

considered applicable to the uranium HLF

Types of Leach Pads

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Leach Pad Technology

Types of Leach Pads:Standard (Conventional)Valley FillOn/Off (Reusable)Hybrid

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Types of Leach Pads – Standard Leach Pad

Standard (Conventional) Leach Pad:Ore heap under leach while continually loaded

Containment berms

Leach solutions routed to external ponds

Grade to drain

Liner system design per 10 CFR 40

Relatively flat topography preferredExternal solution and storm water ponds

Can tolerate variable ore production and leach cycle time

Liner system(typically single composite liner)

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Types of Leach Pads – Valley Fill

Valley Fill Leach Facility

Uses natural topography to form leach pad

Requires hard, durable ore Can tolerate variable ore production and leach cycle time

Internal solution storage (no external ponds)Internal pond(s) require pumping system

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Types of Leach Pads – On/Off

On/Off Leach Pad:

Liner system(exposed to loading/unloading stresses)

Ore types:Ores with short leach cycles (30 days or less)Soft ores that cannot be stacked very high

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On/Off Leach Pads – Additional Considerations

Generally less expensive to construct, but higher operational cost per ton (double‐handling of ore)

Lower operational flexibility ‐ Cannot tolerate variable ore production and leach cycle time

Requires suitable waste site for spent ore

Increased maintenance

Need to build at least three pads or cells to have continuous operation

Unloading of anOn/Off Pad:

Design Parameters

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Design Criteria – What does the designer need to know?Ore characteristicsGradation Stacked dry density Permeability under load

Porosity Strength characteristics (after leach)Moisture contents (as‐delivered, under leach, retained)

Capacity requirements

Ore production schedule Life of mine capacity

Phase construction scheduleMethod of ore transport

Geometry

Lift height

Leaching characteristics Solution application rate Volumetric flow rates

Leach cycle time

Solution application method

No. leach cycles per layerDesign draindown

Environmental requirements

Factors of safety Site characteristics Seismicity

Meteorological data

Material parameters

Interface strengths*Note – This is only a partial list

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Ore Geotechnical Testing ‐ Objectives

Critical to heap leach pad designHydraulic characteristicsMechanical characteristicsCompressibility

Shear strength

Characteristics are not constantf(x) of ore depthMaybe f(x) of time

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Ore Geotechnical Testing ‐ Importance

Geotechnical testing most critical when:

Ore heap heights>150 mSteep terrain with challenging slopesDifficult ore: Mineralogy

Reagent Soft Time dependent decrepidation

High fines content

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Ore Test Program – ConsiderationsConsider the conditions within the ore heap Ore should be tested to replicate the heap conditions as close as practical:How is the ore going to be placed (haul truck or conveyor)?Will the ore be pre‐treated (agglomeration, “aged”, lime addition, etc)?

Consider the type of leach padStress conditions in standard, valley‐fill, and on/off pad are different and will affect ore differently

Is the ore susceptible to degradation?Is the ore compressible? What is the desired maximum ore depth?

What type(s) of solutions are to be used for leaching?

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Sheep Mountain On-going Ore Characterization

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Sheep Mountain Ore Testing Program (Part 1)Agglomeration amenability testworkcompleted:Potential ore permeability concerns

Tests performed using polymer and sulfuric acid as agglomerating agents

Selected non‐anionic dilute polymer agglomeration

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Agglomerating Drum (Typical)

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Sheep Mountain Ore Testing Program (Part 2)

Additional Metallurgical Testwork:Column leach testing: Two (2) columns planned

Compare recovery and processing requirements for agglomerated ore to non‐agglomerated ore

Analytical testwork: Characterize waste streams:

Leachate Spent ore

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Sheep Mountain Ore Testing Program (Part 3)Additional Geotechnical Testwork:Untreated ore: Consolidation‐percolation testing (unsaturated)

Agglomerated ore: Consolidation‐percolation testing (unsaturated)

Consolidation‐permeability testing (saturated)

Strength testing

Consolidation-Percolation Test Apparatus

Consolidation-Permeability Test Apparatus

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Consolidation‐Percolation Test: Aspects

Pass/Fail TestTest investigates proposed solution application rate

Sensitive to ore sizeIncremental increase to applied load

Potential “by‐pass” along sides of vesselFailing tests exhibit ponding at surfaceMonitor settlement and percolation (e.g., collapsible ores)

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Consolidation‐Permeability Test: Aspects

While ore is most commonly leached under unsaturated conditions, the saturated ore hydraulic conductivity:

Represents the maximum solution application rate for the ore:

Testing under load allows the designer to assess whether the ore heap is likely to become saturated under future conditions (i.e., increased load)

Ore Permeability = f(x) of depth

Ore Permeability = f(x) of time

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ENERGY FUELS INC.


Ore Geotechnical Testing ‐ Conclusions

Ore geotechnical testing critical to heap leach pad designGeotechnical tests are relatively inexpensiveProvides data on the performance (hydraulic and mechanical) of ore under load and leaching conditions

Important to recognize that the ore’s physical properties are not constant, but may change due to:

Ore loading (depth)Degradation of ore from leaching

Changes in process (crushing)

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Sheep Mountain Ore Testing ‐ Schedule

Agglomeration amenability testing completed

Geotechnical testwork:Testing of non‐agglomerated ore complete

Testing of agglomerated ore underway

Column leach testing:Scheduled to commence on April 1st

Anticipate 70 to 90 days for completion

2013/03/12 sheep mountain project heap leaching technology ... · 3/13/2013 6 11 energy fuels inc....

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