Unit 6.6 - Nuclear Energy

Question 1

Nuclear Fission and Radioactivity

Answer 1

• A neutron is fired into the nucleus of a radioactive (unstable) element such as Uranium
  - Nucleus breaks apart and releases lots of energy (heat) + more neutrons that breals more nuclei apart, releasing more energy (chain reaction)
• Radoactivity refers to the energy given off by the nucleus of a radioactive isotope (Uranium-235)
  - Radioactive nuclei decay, or breakdown and give off energy (radiation) even ithout sission; nuclear fission just releases tons of energy all at once
• Radioactive half-life = te amount of time is takes for 50% of a radioactive substance to decay (breakdown)

Question 2

Generating Electrcity

Answer 2

• Same electricity generation process as with fossil Fuels, just uranium fission to heat water into steam
  - heat -> water into steam -> seam turns a turbine -> turbine powers generator -> generator produces electricity
• U235 stores in fuel rods, submerged in water in reaction core; heat from fission turns H2O into steam
• Control rods - are lowered into reactor to absorb neutrons and slow down the reaction, preventing meltdown (explosion)
• Water pump - brings in cool water to be turned into steam and also cools reactor down from overheating
• Cooling tower - allows steam from turbine to condense back into liquid and cool down before being reused 9this gives off H2O vapor)

Question 3

Nonrenewable, but cl eaner than Fossil Fuels

Answer 3

• Nuclear energy is nonrenewable because radioactive elements like uranium are limited
• No air pollutants (Pm, SOx, Nox) or CO2/CH4 are released when electricity is generated: mining of uranium and plant construction still releaes GHG
• Only gas released from electricity generation s water vapor (which is technically a GHG, but stays in th atmosphere very breifly)
• Other drawbacks of nuclear energy include possibility of meltdown and radioactive contamination
• spent fuel rods - used fuel rods remain radioactive for millions of years and need to be stored on lead containers on site at nucear power plants
• Mine tailings - lefotover rock and soil from mining may haver adioactive eleents that can contaminate water or soil nearby
• Water use - nuclear power plans require lots of water and can deplete local surface or gorundwaer sources
• Thermal Pollution - hot water from Power Plant released back into surface waters can cause them thermal shock (decreased O2 and suffocation)

Question 4

Nuclear Meltdowns

Answer 4

• three Mile Island (US), Fukushima Japan, and Chernobyl Ukraine = 3 most famous nuclear meltdowns
• Three Mile Island (US) - Partial meltdown due to testing error, radiation released but no deaths or residual cancer cases
• Fukushima (japan) - an earthquake and tsunami triggered coolingpump failuer that lead to a meltdown (explosion of reactor and core) and widespread radiation release
• Chernobyl (Ukraine) - stuck cooling valve during test lead to complete meltdown (explosion of reactor core), several deaths and wdespread radiation release
• Environmental consequences of meltdowns: genetic mutations and cancer in surrounding people, animals, and plants due to radiation released from reactor core
• Contaminated soil - radiation can remain in soil and harm lants and animals in the future (genetic mutations)
• Radiation spread - radiation can be carried by the wind over long distances, affecting ecosystems far from the meltdown site