12Radioisotopes in Medicine Radioisotopes likeTc-99 can be used todetect bone cancer.The Tc-99 accumulatesin areas of abnormalbone metabolism andthen detection of thenuclear radiation (gammarays) show the location ofthe cancer.
13Radioisotopes in Agriculture -Radioactive tracers used to determine the effectivenessof fertilizers.Cobalt-60 producesgamma rays that areused to irradiatefood.
14FissionNuclear fission occurs when scientists bombard a large isotope with a neutron.This collision causes the larger isotope to break apart into two or more elements.These reactions release a lot of energy.You can calculate the amount of energy produced during a nuclear reaction using an equation developed by Einstein: E=mc2
16Nuclear Power PlantsIf the neutrons can be controlled, then the energy can be released in a controlled way. Nuclear power plants produce heat through controlled nuclear fission chain reactions.The fissionable isotope is contained in fuel rods in the reactor core. All the fuel rods together comprise the critical mass.Control rods, commonly made of boron and cadmium, are in the core, and they act like neutron sponges to control the rate of radioactive decay.
17Nuclear ReactorsThe reaction is kept in check by the use of control rods.These block the paths of some neutrons, keeping the system from reaching a dangerous supercritical mass.
18Nuclear Power Plants (cont) In the U.S., there are approximately 100 nuclear reactors, producing a little more than 20% of the country’s electricity.AdvantagesNo fossil fuels are burned.No combustion products (CO2, SO2, etc) to pollute the air and water.DisadvantagesCost - expensive to build and operate.Limited supply of fissionable Uranium-235.Accidents (Three Mile Island & Chernobyl)Disposal of nuclear wastes
19Nuclear ReactorsIn nuclear reactors the heat generated by the reaction is used to produce steam that turns a turbine connected to a generator.
20What is Nuclear Fusion?Nuclear Fusion is the energy-producing process taking place in the core of the Sun and starsThe core temperature of the Sun is about 15 million °C. At these temperatures hydrogen nuclei fuse to give Helium and Energy. The energy sustains life on Earth via sunlight
22Nuclear Fusion Fusion would be a superior method of generating power. The good news is that theproducts of the reaction arenot radioactive.The bad news is that in order to achieve fusion, the material must be in the plasma state at several million kelvins.Tokamak apparati like the one shown at the right show promise for carrying out these reactions.They use magnetic fields to heat the material.