Nuclear Power Notes

Nuclear Reactors in the United States

• There are currently 104 commercial nuclear reactors in the United States
• California has two in operation
• The majority are located on the East coast and were built many years ago
• No new reactors have been built in the past 30 years
• Produces 70% of carbon-free electricity
• Only 20% of the energy we use is from nuclear power.
• Department of Energy contributes towards nuclear power.
  • $40 million towards research and development of nuclear power plants in the United States.
• The United States is ranked first in energy usage in the world.
  • Measured in tonnes in oil equivalent per person per year.
  • The United States has an equivalent of 8.35 tonnes in oil equivalent per
    person.
  • Developed European countries average 5.0 per year.

How Nuclear Power Works

• Electricity is generated through the process of fission, using the element Uranium as fuel
• It is a non-renewable energy source
• In a nuclear reactor, the atoms of uranium are hit with neutrons, and the atoms break apart
• When the atoms break apart, heat is a byproduct
  • This process is called fission
  • Another byproduct is nuclear waste
• The heat generated is used to boil water and create steam
• The steam is used to power turbines which generate electricity

Uranium

• Uranium is used to fuel nuclear power
• It is unstable and slightly radioactive
• Uranium is found throughout the Earth’s crust
• So how do we get uranium out of the crust?

Uranium Mining

• Prior to 2004 there were 5,000 companies with uranium mining rights in the United States, today there are over 32,000
• The majority of mines are located in the Western United states where there are over 14,000 mines
• Open Pit (Surface) Mining
  • This method is used when the uranium ore is close the the surface
  • It is dug out of the ground using heavy machinery
  • The displaced soil is stored nearby until the mining is complete
  • When complete, the soil is used to to fill in the mine
• Underground Mining
  • This method is used when the uranium is deeper in the ground
  • Natural pillars and walls are left in the mine to provide support
  • Ore and soil are moved out of the mine with rail cars
• Heap Leaching
  • Heap leaching is used to remove the uranium from the ore that was obtained using open pit or underground mining
  • The rock is crushed to sand-sized particles and deposited in a heap onto a pad of clay or coated concrete
  • A sprinkler sprays the leaching solution onto the pile, as it trickles down it moves the uranium with it
  • The solution is then processed to remove the uranium and made into yellowcake
  • This process is no longer common in the U.S.
• In-Situ Leaching
  • In situ leaching is the most common type of uranium mining, it is also the most economical
  • Injection wells are drilled on either side of a production well
  • The injection wells pump lixiviant into the ground, which dissolves the uranium and it flows to the production well
  • Lixiviant is a mixture of carbon dioxide, water, and oxygen
  • From the production well the solution is processed to make yellowcake

Risks of Uranium Mining

• There are health and environmental hazards associated with uranium mining
• In situ leaching reduces risks to miners from dust, accidents, and radiation
• Groundwater can be contaminated
• After mining, the groundwater is returned to EPA drinking water maximum contaminant limit levels if possible
• The leaching solution can permeate the area and not be able to be removed
• Health hazards are currently under debate
• Exposure to uranium can affect the renal system and cause problems with the urinary tract and kidneys
• According to a branch of the CDC, there is no link to naturally-occurring uranium ore and cancer
• Other groups say that there is a direct link

Uranium Enrichment

• Uranium 238: Mined in its natural form Uranium Oxide (U3O8)
• Only 1% of mined of Uranium 238 contains Uranium 235
• Uranium 235 is fissile Uranium needed for nuclear reactions.
• Enriching Uranium 235: The process of increasing Uranium 238 to approximately 4% Uranium 235.

Next Generation Nuclear Power

• Traditional nuclear reactors are light water reactors
  • Water is used to cool the Uranium during the fission process.
  • These reactors operate at approximately 300¾ Celsius.
• Next Generation Nuclear Plants
  • HTGC (High Temperature Gas Cooled) reactors.
  • Helium is used to cool the reactors.
  • NGNP reactors operate between 750¾ and 900¾ Celsius.
  • 100 times more energy yield from the same amount of Uranium 235.

Risks of Nuclear Power

• Radioactive nuclear waste: Currently no long-term disposal plan
• Cost: It is expensive to build power plants, can cost several billion dollars
• Risk of catastrophe
  • If a nuclear reactor fails there is potential for a major disaster
  • Hundreds of thousands were exposed to radiation when the Chernobyl plant failed in1986, responsible for approximately 4,000 deaths
  • Three Mile Island (Harrisburg, Pennsylvania): The reactor was damaged, but the radiation was contained
• There is little public support: Due to the above factors, there is little support for new nuclear reactors to be built

Benefits of Nuclear Power

• Zero carbon emissions
  • As the Earth’s population grows, the demand for electricity will increase
  • This increase in demand will generate even more carbon emissions that contribute to climate change, unless we use low or zero carbon emission sources of energy
• Small amounts of waste generated
  • Nuclear power generates two thousand tons of waste annually in the United States, while over two BILLION tons of carbon dioxide is produced annually from burning coal
• Fuel source is abundant in the U.S. and throughout the world
  • Uranium is found throughout the Earth’s crust (1% concentration), high concentrations (10-20%) in Australia and Canada
• Dependable and cheap source of electricity
  • Operating costs are about the same as coal
  • More reliable than renewable sources of energy
  • Compared to solar:
    • Photovoltaic Cells
      • Higher startup costs:$15 per Megawatt
      • More expensive to operate: Approximately 25 cents per Kwh.
    • Nuclear Power Plant -
      • Lower startup costs.$3.75 per Megawatt.
      • Less expensive to operate.Approximately 1.85 cents per Kwh.
• Much safer than in the past
  • Chernobyl accident was the result of a poor design and undertrained employees
• New jobs would stimulate local economies in isolated areas in the United States that have been hit hard during the recession.