11.3 Nuclear Energy Key Concepts: What happens during a nuclear fission reaction? How does a nuclear power plant produce electricity? How does a nuclear fusion reaction occur? Key terms: Nucleus, nuclear fission, reactor vessel, fuel rod, control rod, meltdown, nuclear fusion

Nuclear Fission Nucleus – core of an atom that contains protons and neutrons Nuclear reactions convert matter into energy E=mc2 Nuclear fission – splitting of an atom’s nucleus into two smaller nuclei Fuel for this reaction is a large atom with an unstable nucleus, like uranium 235. When the neutron hits a U-235 nucleus, the nucleus splits apart into two smaller nuclei and two or more neutrons The total mass is just a little less than the original This missing mass is converted to energy (like Einstein said) Creates a chain reaction with more missing mass, creating more energy

Energy from fission What happens to all the energy? If it is not controlled, you have bad things like atomic bombs. If it is controlled, you get nice things like heat. Sounds smart to have done this, doesn’t it?

Nuclear power plants In a nuclear power plant, the heat released from fission reactions is used to change water into steam. The steam then turns the blades of a turbine and generates electricity. Reactor vessel – where fission occurs Fuel rods – inside the vessel – has the U-235 Control rods – made of metal cadmium – inserted between fuel rods to absorb neutron release and slow the reaction Heat exchanger – heat is removed from the reactor vessel by water or another fluid. The fluid passes through a heat exchanger where it boils water to produce steam.

Risks of nuclear power Meltdown – excess heat can cause explosions Radioactive material explodes into the environment and lasts for decades… meaning people/animals can’t or shouldn’t live there

Quest to control fusion Nuclear fusion – two hydrogen nuclei combine to create a helium nucleus, which has slightly less mass than the two hydrogen nuclei. The lost mass is converted to energy. Fusion could provide more energy than fission