Nuclear Energy
Pitchblende or Uranium Oxide or U3O8
Pitchblende is a mixture of…….. 235U & 234U & 238U Only 235U is fissionable
Uranium is common in the Earth’s crust Uranium is common in the Earth’s crust. It is 35 times more common than silver!
First: Mine Mine the pitchblende out of the ground (subsurface or surface)
Big Eagle Open Pit Uranium Mine (Wyoming)
Second: Mill Milling. Mined uranium ores normally are milled by grinding the ore materials to a uniform particle size and then treating the ore to extract the uranium by heap leaching. The milling process commonly yields dry powder-form material consisting of natural uranium, "yellowcake," which is sold on the uranium market as U3O8.
The result of milling is….. Yellow Cake! Yummmmmmm
Uranium Milling Locations
Third: Conversion Uranium conversion. Milled uranium oxide, U3O8, must be converted to uranium hexafluoride, UF6 (which can be enriched).
Fourth: Enriching Enrichment. The concentration of the fissionable isotope, 235U is less than that required to sustain a nuclear chain reaction in reactor cores. Natural UF6 must be "enriched" in order for it to be used as nuclear fuel.
Gas centrifuge is the most commonly used uranium enrichment technology. In the gas centrifuge process, the UF6 gas is spun at high speed in a series of cylinders. This acts to separate the 235UF6 and 238UF6 atoms based on their slightly different atomic masses.
The enriching process results in excess 238U that is called depleted uranium.
Depleted uranium is used in warheads Depleted uranium is used in warheads . It is used because it carries a lot of kinetic energy (it is dense) and does a lot of damage on impact.
Depleted uranium (tailings)
Milling and Enriching
Highly Enriched 235U (in the hand’s of a fool)
Fifth: Fabrication Fabrication. For use as nuclear fuel, enriched UF6 is converted into uranium dioxide (UO2) powder which is then processed into pellet form.
The pellets are then fired in a high temperature furnace to create hard, ceramic pellets of enriched uranium. The cylindrical pellets then undergo a grinding process to achieve a uniform pellet size. The pellets are stacked, according to each nuclear core's design specifications, into tubes of corrosion-resistant metal alloy.
The tubes are sealed to contain the fuel pellets: these tubes are called fuel rods. The finished fuel rods are grouped in special fuel assemblies that are then used to build up the nuclear fuel core of a power reactor.
Fuel Rods (3% U-235; 97% U-238) Fuel Assembly Fuel Rods Pellets
Fuel rods Reactor Core
The Process
The nuclear reaction
Neutron Fissionable U-235 Unstable U-236 Two fission fragments: Ba-141 & Kr-92 3 neutrons
The Fission Process 1 (of 3 neutrons) hit a U-235 = critical < 1 neutron hits a U-235 = subcritical > 1 neutron hits a U-235 = supercritical (yikes!)
Who Has the Uranium? Country Percentage of Uranium Australia 23% Kazakhstan 16% Canada 11% United States 10% South Africa 8% Niger 6% Namibia