Ch. 16 Environmental Science
All matter is made of atoms Atoms have
Proton Electron Neutrons
Nucleus contains protons and neutronshas 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 atomsUnstableDecayEmit particles and
energy from nuclei
Radiation1) alpha particles - 2 protons and 2 neutrons, cannot penetrate skin or paper, but dangerous in lung2) beta particles – high speed electron, can penetrate skin, stopped with aluminum foil3) 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 power plants produce radioactive waste
Radiation unhealthy to living cells May cause cancer and genetic
mutations
High level waste – emit large amounts of radiationUranium fuel rodsControl rodsWater 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 20th anniv. Utube