FUSION AND FISSION

THE SUN Every second, the sun converts 500 million metric tons of hydrogen to helium. Due to the process of fusion, 5 million metric tons of excess material is converted into energy in each second. This means that every year, 157,680,000,000,000 metric tons are converted into energy.

Nuclear Fusion Nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy depending on the masses of the nuclei involved..

FUSION DEUTERIUM NEUTRON HELIUM TRITIUM http://fusioned.gat.com

Nuclear Fusion Iron and nickel nuclei have the largest binding energies per nucleon of all nuclei and therefore are the most stable.

Nuclear Fusion The fusion of two nuclei lighter than iron or nickel generally releases energy. The fusion of nuclei heavier than them absorbs energy.

Complete the Reaction 4Be 1H element 4Be 2He 6C 2He 2He 6C 8O 2He atomic number (protons) 4Be 1H 2He 6C 2He 1H 1H 6C 2He 4Be 8O 2He 2He

Energy needed for Fusion The thermal activity of a gas is described by its temperature measurement which is really an indication of its velocity/energy. Thermal energy is represented by the height that the upper magnet. The upper ring has a potential energy given by PE = mgh at its drop point which is converted into kinetic energy (KE = 1/2 mv2) As the magnet falls towards the lower magnet. The two magnets click lightly when the kinetic energy is just greater than the magnetic energy that holds them apart. Since Kinetic Energy = Potential Energy (ignoring frictional components), the gravitational pull and mass of the upper magnet are constant, then the height needed to overcome the magnetic repelling force is proportional to that magnetic repelling force.

Energy needed for Fusion PE =mg x h2-h1 PE = KE = Fxh1 F=force of repulsion F=PE/h1 Upper Drop Position Ring Magnets Float Position Lower Magnet Wood Block h2 h1

Fusion Changes Mass to Energy E=mc2 .993 kg Helium He H 1kg Hydrogen

Cookie Fusion Procedure Cut 2 squares of wax paper 10 cm on a side Cut 5 cm wide slice of cookie dough (atom) Find the mass of the atom and record on the table Place the atom one cm away from the edge of a wax paper square Repeat step 2 thru 4 for a second atom Place the atoms about 2 cm from each other Place both atoms on a plate and microwave for 1 minute Remove the “new element” and let cool for 2 minutes Find the mass of the “new element” Complete the table

Cookie Fusion Mass Before Cooking Mass After Cooking Atom 1 Atom 2 Total Difference

Learning Check What process creates energy in the Sun? Fusion of hydrogen into helium in the Sun’s core generates the Sun’s energy. How long ago did fusion generate the energy we now receive as sunlight? Fusion created the energy we receive today about a million years ago. This is the time it takes for photons and then convection to transport energy through the solar interior to the photosphere. Once sunlight emerges from the photosphere, it takes only about 8 minutes to reach Earth.

Learning Check

NUCLEAR FISSION A reaction in which an atomic nucleus of a radioactive element splits by bombardment from an external source, with simultaneous release of large amounts of energy, used for electric power generation

Nuclear Fission Neutron induced in U235 Fission is Exothermic The sum of the masses of the resulting nuclei is less than the original mass (about 0.1% less) The “missing mass” is converted to energy according to E=mc2

Neutrons may: 1 - Cause another fission by colliding with a U235 nucleus 2 - Be absorbed in other material 3 - Lost in the system If sufficient neutrons are present, we may achieve a chain reaction Creates two smaller nuclides and free neutrons The free neutrons potentially collide with nearby U235 nuclei May cause the nuclide to split as well Each split (fission) is accompanied by a large quantity of E-N-E-R-G-Y

U.S. Electrical Power Production by Source The United States has 103 nuclear power reactors in 31 states. Nuclear energy provides electricity for one of every five homes and business … the second-largest source of electricity after coal. Some states are clearly are more dependent on nuclear energy than others. Vermont gets 76 percent of its electricity from nuclear reactors … New Hampshire, 58 percent … and South Carolina, 55 percent. In Virginia, nuclear power provides more than 40 percent of the electricity used. Source: EIA (2004)

Nuclear Fuel Costs Nuclear Fuel Costs Include Uranium Enrichment Manufacturing Waste Disposal Total Nuclear Fuel Cost is Only About 0.5 cents per kilowatt-hour Uranium accounts for only about 20% of this cost or 0.1 cents per kilowatt-hour Increasing Uranium Cost has Minimal Impact

Review Nuclear fission: A large nucleus splits into several small nuclei when impacted by a neutron, and energy is released in this process Nuclear fusion: Several small nuclei fuse together and release energy.

Draw a Double Bubble Map of Fusion and Fission Differences Similarities Differences