UPSC Express

About: Uranium

• Uranium is composed mainly of two isotopes – U-235 and U-238.
  
  • Uranium-235 and U-238 are chemically identical, but differ in their physical properties, notably their mass.
    
  • The nucleus of the U-235 atom contains 92 protons and 143 neutrons, giving an atomic mass of 235 units.
    
  • The U-238 nucleus also has 92 protons but has 146 neutrons – three more than U-235 – and therefore has a mass of 238 units.
    
• Natural uranium contains 99.3% U-238 isotope and 0.7% U-235 isotope.
  
• U-238 isotope is not fissile i.e. it cannot start a nuclear reaction and sustain it.
  
• On the other hand, the U-235 isotope is useful for nuclear power reactors, as well as for nuclear weapons.
  
  • A nuclear power plant requires uranium with 3-4% U-235, known as Low-enriched uranium (LEU) or reactor-grade uranium
    
  • A nuclear weapon needs uranium with 90% U-235, known as Highly-enriched uranium (HEU).
    

About: Uranium Enrichment:

• As nuclear reactors and weapons need higher percent of fissile U-235 isotope, it is attained through Uranium Enrichment.
  
• For this, Isotope separation is used, which is a physical process to concentrate (‘enrich’) one isotope relative to others.
  
• The difference in mass between U-235 and U-238 allows the isotopes to be separated and makes it possible to increase or “enrich” the percentage of U-235.
  
• Typical methods for enrichment include: gaseous diffusion, electromagnetic separation, aerodynamic processes, laser enrichment and centrifuge separation.