2Fusion vs. fission Nuclear fission: A large nucleus splits into several small nuclei when impacted by a neutron, and energy is released in this processNuclear fusion:Several small nuclei fuse together and release energy.2
3A little bit on the atom… Neutral neutrons-Nucleus-------Negative electronsPositive protons
4Conservation of Energy/Mass Energy cannot be created or destroyed – it can only change form.E = mc2Mass is really a form of energy
5Another look at E = mc2 E = energy (J) m = mass (kg) c = speed of light (3 x 108 m/s)Mass is really just another form of energy!
7THE SUNEvery 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.
8Nuclear FusionNuclear 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..
10Complete the Reaction 4Be 1H element 4Be 2He 6C 2He 2He 6C 8O 2He atomic number (protons)4Be1H2He6C2He1H1H6C2He4Be8O2He2He
11Fusion Changes Mass to Energy E=mc2 .993 kg HeliumHeH1kg Hydrogen
12Learning 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.
14NUCLEAR FISSIONA 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
15Nuclear Fission Neutron induced in U235 Fission is Exothermic The sum of the masses ofthe resulting nuclei is lessthan the original mass (about 0.1% less)The “missing mass” is converted to energy according to E=mc2
16Neutrons may:1 - Cause another fission by colliding with a U235 nucleus2 - Be absorbed in other material3 - Lost in the systemIf sufficient neutrons are present, we may achieve a chain reactionCreates two smaller nuclides and free neutronsThe free neutrons potentially collide with nearby U235 nucleiMay cause the nuclide to split as wellEach split (fission) is accompanied by a large quantity of E-N-E-R-G-Y
17How fusion can be used? GOOD EVIL A controlled reaction in a reactor used to produce cleaner, inexpensive electricity???EVILA fission bomb starts a fusion chain reaction to create an incredibly powerful weapon – thermonuclear weapons (H-bombs), MUCH more destructive than atomic bombs.
18A-bomb vs. H-bomb Atomic bomb (Hiroshima)– fission process Killed over 66,000 people instantly13 kilotons of TNT-equivalent2 exploded in warfareHydrogen bomb – fusion process10 megatons (million-tons) of TNT-equivalentNEVER exploded in warfareIs it the bomb too big to ever be used???
19U.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)
20Nuclear Fuel Costs Nuclear Fuel Costs Include UraniumEnrichmentManufacturingWaste DisposalTotal Nuclear Fuel Cost is Only About 0.5 cents per kilowatt-hourUranium accounts for only about 20% of this cost or 0.1 cents per kilowatt-hourIncreasing Uranium Cost has Minimal Impact
21Review Nuclear fission: A large nucleus splits into several small nuclei when impacted by a neutron, and energy is released in this processNuclear fusion:Several small nuclei fuse together and release energy.
22Fiss vs. Fuse Fiss = break down Start with a larger atom and finish with two or more smaller atomsFuse = build upStart with two smaller atoms and finish with one larger atom
23ReviewMass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc2)Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nucleiFusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus
24Mini-assessment1. Which nuclear process produces large amounts of energy?A. FissionB. FusionC. Both fission & fusionD. Neither fission nor fusion
25Mini-assessment2. Fission is the process that _________ atomic nuclei.A. CombinesB. Burns upC. StoresD. Splits
26Mini-assessment3. Mass may be converted into energy.A. TrueB. False
27Mini-assessment 4. The fission process requires heavy atomic nuclei. A. TrueB. False
28Mini-assessment5. Name a nuclear reaction that occurs within the sun:
29Mini-assessment6. Fission is a natural process that occurs on the planet Earth.A. TrueB. False
30Mini-assessment7. Explain this equation: (4 points)E = mc2
318. Draw a Double Bubble Map of Fusion and Fission Differences Similarities Differences
33Cookie 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 tablePlace the atom one cm away from the edge of a wax paper squareRepeat step 2 thru 4 for a second atomPlace the atoms about 2 cm from each otherPlace both atoms on a plate and microwave for 1 minuteRemove the “new element” and let cool for 2 minutesFind the mass of the “new element”Complete the table
34Cookie Fusion Mass Before Cooking Mass After Cooking Atom 1 Atom 2 TotalDifference