Ch. 16 Environmental Science

 All matter is made of atoms  Atoms have Proton Electron Neutrons Nucleus contains protons and neutrons has most of the mass Neutral protons = electrons

 Properties determined by protons  Proton number never changes for that element  Atomic number is proton number

 Mass number = protons + neutrons  Isotopes – atoms of the same element that have different numbers of neutrons  Uranium  92 protons, 146 neutrons  Mass number 238  Isotope U-235, 143 neutrons

 Radioactive atoms  Unstable  Decay  Emit particles and energy from nuclei

Radiation 1) alpha particles - 2 protons and 2 neutrons, cannot penetrate skin or paper, but dangerous in lung 2) beta particles – high speed electron, can penetrate skin, stopped with aluminum foil 3) gamma rays – electromagnetic radiation, can go through body. Can be blocked by several cm of lead or concrete, or 1 m of water

 Half-life  The amount of time it takes for half the atoms in a sample of radioactive element to decay  May be a few seconds to billions of years

 Nuclear fission  A reaction in which the nucleus of a large atom is split into smaller nuclei  Emits large amounts of energy  May be used for electricity

 Nuclear Fission  U-235 most commonly used  Chain reaction releases energy

 Nuclear reactor vessel  Where the fission of U-234 takes place  Used to produce electricity  Heat produced by fission instead of fossil fuels

 Breeder reactors  Changes U-238 into plutonium-239  Pu-239 used as nuclear fuel  Not used in the US because of terrorism  Plutonium used in atomic bombs  Nuclear Reaction-Plutonium video Nuclear Reaction-Plutonium video

 Nuclear power plants produce radioactive waste  Radiation unhealthy to living cells  May cause cancer and genetic mutations

 High level waste – emit large amounts of radiation  Uranium fuel rods  Control rods  Water used to control the chain reactions  Medium-level and low-level waste are not as radioactive, although more of these are generated

 Difficult to dispose of  Long half-lives – takes 1000’s of years to decay.  Sealed on containers that will not decay  Stored underground- geologically stable  Yucca Mountains, Nevada  Huge environmental concerns

 Meltdown- chain reaction goes out of control and melts the reactor core.  Chernobyl, Ukraine, April 1986-meltdown  116,000 people permanently left  At least 15,000 cases of cancer  Old plant, lacked many safety features  Utube Utube  20 th anniv. Utube 20 th anniv. Utube