nuclear energ and the environmentnuclear energy and the environmentnuclear energy and the environmentnuclear energy and the environment.ppt

Chapter 20: Nuclear Energy and the Environment Nuclear Energy The energy of the atomic nucleus Two processes can be used to release that energy Fission – splitting of atomic nuclei Fusion – fusing or combining of atomic nuclei Nuclear reactors-devices that produce controlled nuclear fission. Used for commercial energy production Fission Reactors First demonstrated in 1942 Led to development of nuclear energy to produce electricity. Also power submarines, aircraft carriers, and icebreaker ships. Nuclear fission produces much more energy than fossil fuels 1 kilogram of uranium oxide produces heat equivalent to 16 metric tons of coal Fission Reactors Three types (isotopes) of uranium occur in nature Uranium-238 Uranium-235 (only naturally occurring fissionable material) Uranium-234 Enrichment necessary Processing to increase concentration of U235 Fission Reactors Split U-235 by neutron bombardment Reaction produces neutrons, fission fragments and heat. Starts a chain reaction Steam produced runs a turbine that generates electricity. Similar to coal or oil burning power plants Fission Reactors Main components of a reactor Core: fuel and moderator Control rods: control the rate of reaction or stop it Coolant: remove heat Reactor vessel The entire reactor is contained in a reinforced concrete building Fission Reactors Meltdowns Occur when heat not removed fast enough Nuclear fuel becomes so hot it forms a molten mass Breaches containment of reactor and contaminates surrounding area Design philosophy emerged to build smaller reactors W/ passive stability (gravity feed cooling systems) Or helium gas cooled which can’t meltdown Sustainability and Nuclear Power Two aspects Nuclear power’s role in creating alternative fuel supplies Could help the US transition from oil to other energy sources The sustainability of nuclear fuel itself Is a nonrenewable resource Sustainability and Nuclear Power Currently light water reactors are very inefficient Breeder reactors Designed to pro