Uranium Ore Processing

Environmental issues
1. Water management
  1. Aquifer contamination
    1. Water balance analysis
2. Radioactive decay
  1. Slow, U-238 has a half life of 4.47 billion years
  2. Alpha, beta and gamma decay
3. Tailings management
4. Polution
  1. Chemical spills
Excavation
1. Open pit
  1. Lower
    1. More
      1. More likely
        Larger
2. Underground mine
  1. Higher
    1. Less
      1. Less likely
        Smaller
  2. In-situ Leach (ISL)
    1. Minimal environmental impact
    2. Use of solutions to dissolve Uranium underground before pumping out
      1. Sulfuric acid
      2. Nitric acid
      3. Carbonates
      4. Dissolved oxygen
      5. Uranium recovered as precipitate
      6. Alkali solutions
        Used when carbonate minerals present
      7. Pumping of fluids
    3. Porous unconsolidated materials
3. Advantages & disadvantages
  1. Cost
    1. Waste rock
      1. Radiation & health issues
        Surface footprint
4. Cut-off grade around 0.07 %
  1. Is it economically viable in the current market conditions
5. By-product from other mines such as copper or gold
Impact on society
1. Economic
  1. Increased wealth
  2. Tax benefits
  3. Growth
  4. Mining company payments to mineral rights owners
2. Negative
  1. Industrialisation of rural areas
  2. Noise
  3. Effects on local industries e.g agriculture or tourism
  4. Health risks
    1. Cancer
    2. Kidney disease
    3. Lukemia
    4. Birth defects
3. Positive
  1. Energy source
  2. Reduced carbon emissions
  3. Jobs
Extraction from ore
1. Separation of mineral from gangue
  1. Heap leaching
    1. Low grade ores
    2. Low clay content
    3. Low metal recovery
  2. Filtration of leach solution
    1. Separation of tailings
      1. Tailings disposal or storage
        Possibility of acid mine drainage
    2. Horizontal belt, pressure or drum filters.
    3. Purification
      1. Pregnant solution
        Precipitation of uranium
        Use of ammonia, hydrogen peroxide, caustic soda or caustic magnesia
        Solids separation
        Centrifuge/filtering
        Yellowcake (uranium oxide concentrate)
        Drying
        Calcination
      2. Ion exchange
      3. Solvent extraction
  3. Tank leaching
    1. Conventional uranium mill
  4. Oxidation of uranium compounds
    1. Acid leaching reaction UO3 + 2H^+ = UO2^2+ H2O
    2. Alkaline leaching reaction 2UO2 + O2 = 2UO3
2. Crushing & grinding
  1. Water/slurry mixture
  2. Jaw crusher
    1. Rod or ball mill
Uranium: Radioactive metal used primarily as fuel in nuclear reactors
1. Two most common isotopes: U-238, U-235
Hazards
1. Military or unpeaceful use
  1. Can be unclear if production of enriched Uranium is for peaceful or unpeaceful use if organisations not transparent
2. Dust
3. Radiation
4. Gas emissions
5. Toxicity
6. Dangers for future generations
Refining
1. Yellow cake and Fluorine reaction to produce uranium hexafluoride gas
  1. Separation of isotopes
    1. Newer technology: laser enrichment
      1. Based on photoexcitation principles
    2. Two output streams
      1. Enriched U-235
        Nuclear fuel fabrication
        Phase change from gas to solid
        Conversion to uranium dioxide powder
        Shaped into fuel pellets and heated to make a hard material
        Nuclear reactor rods
        Reaction with calcium
      2. Depleted U-235, mostly U-238
    3. Diffusion
      1. Use of many porous membranes
        More expensive than centrifuge
    4. Centrifuge
      1. Separates molecules with different densities
        More efficient than diffusion
        Less environmental impact
2. Uranium enrichment
  1. Increasing the proportion of the U-235 isotope

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Uranium Ore Processing

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	Creado por Sebastian Eunson hace más de 7 años