Fusion vs. fission 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.
A little bit on the atom… Negative electrons Positive protons Neutral neutrons Nucleus
Conservation of Energy/Mass Energy cannot be created or destroyed – it can only change form. E = mc 2 Mass is really a form of energy
Another look at E = mc 2 E = energy (J) m = mass (kg) c = speed of light (3 x 10 8 m/s) Mass is really just another form of energy!
FUSION AND FISSION
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. THE SUN
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 TRITIUM HELIUM NEUTRON
Complete the Reaction 1H 4 Be 1H1H 8O8O 2 He 1H1H 6C6C 1 H element atomic number (protons) 6C6C
Fusion Changes Mass to Energy E=mc 2 H HeHe 1kg Hydrogen.993 kg Helium
Learning Check What process creates energy in the Sun? Fusion of hydrogen into helium in the Suns core generates the Suns 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.
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 U 235 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=mc 2
Neutrons may: 1 - Cause another fission by colliding with a U 235 nucleus 2 - Be absorbed in other material 3 - Lost in the system If sufficient neutrons are present, we may achieve a chain reaction Each split (fission) is accompanied by a large quantity of E-N-E-R-G-Y Creates two smaller nuclides and free neutrons The free neutrons potentially collide with nearby U 235 nuclei May cause the nuclide to split as well
How fusion can be used? GOOD –A controlled reaction in a reactor used to produce cleaner, inexpensive electricity??? EVIL –A fission bomb starts a fusion chain reaction to create an incredibly powerful weapon – thermonuclear weapons (H-bombs), MUCH more destructive than atomic bombs.
A-bomb vs. H-bomb Atomic bomb (Hiroshima)– fission process –Killed over 66,000 people instantly –13 kilotons of TNT-equivalent –2 exploded in warfare Hydrogen bomb – fusion process –10 megatons (million-tons) of TNT-equivalent –NEVER exploded in warfare –Is it the bomb too big to ever be used???
U.S. Electrical Power Production by Source 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.
Fiss vs. Fuse Fiss = break down Start with a larger atom and finish with two or more smaller atoms Fuse = build up Start with two smaller atoms and finish with one larger atom
Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc 2 )Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc 2 ) Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nucleiFission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleusFusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus Review
Mini-assessment 1. Which nuclear process produces large amounts of energy? A. Fission B. Fusion C. Both fission & fusion D. Neither fission nor fusion
2. Fission is the process that _________ atomic nuclei. A. Combines B. Burns up C. Stores D. Splits Mini-assessment
3. Mass may be converted into energy. A. True B. False Mini-assessment
4. The fission process requires heavy atomic nuclei. A. True B. False Mini-assessment
5. Name a nuclear reaction that occurs within the sun: Mini-assessment
6. Fission is a natural process that occurs on the planet Earth. A. True B. False Mini-assessment
7. Explain this equation: (4 points) E = mc 2 Mini-assessment
8. Draw a Double Bubble Map of Fusion and Fission fusion fission Differences Similarities Differences
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