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INTRODUCTION to FUSION AND FISSION

INTRODUCTION to FUSION AND FISSION. Warm-up. There are 1200 students in a hall. A student starts talking. If each talking student starts 3 others to talk each second,. … what is the minimum time required for all students to be talking?. Warm-up. 64. 64. 256. 256. 256. 1024. 1024.

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INTRODUCTION to FUSION AND FISSION

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  1. INTRODUCTION toFUSION AND FISSION

  2. Warm-up There are 1200 students in a hall. A student starts talking. If each talking student starts 3 others to talk each second, ... … what is the minimum time required for all students to be talking?

  3. Warm-up 64 64 256 256 256 1024 1024 1024 4096 The time required = 6 s How to stop it from being out of control? Sec. No. of talking students 0 1 1 1 + 1  3 = 4 2 4 + ____  3 = ____ 3 ____ + ____  3 = ____ 4 ____ + ____  3 = ____ 5 ____ + ____  3 = ____ 6 ____ + ____  3 = ____ 4 16 16 16 64 Ask teachers responsible for discipline to patrol around the hall.

  4. Nuclear Reactions When a heavy nucleus splits up, huge amount of energy is released. E.g. atomic bomb When 2 light nuclei join together to form a heavy nucleus,  huge amount of energy is released. E.g.the Sun

  5. Nuclear Fission • Fission is the process of splitting a nucleus into two nuclei with smaller masses. • Large amount of energy is releases • A chain reaction is an on-going series of fission reactions. • Critical mass is the amount of fissionable material required to continue a reaction at a constant rate Exothermic Reaction

  6. Nuclear fission U n Ba Kr n n 1 1 1 235 144 90 92 56 36 0 0 0 uncharged  not repelled on approaching nuclei Ba-144 nucleus neutron neutron neutron U-235 nucleus Kr-90 nucleus + + + + + energy

  7. Nuclear fission U n Ba Kr n n 1 1 1 235 144 90 92 56 36 0 0 0 energy + + + + + The total mass of the fission products is found less than the total mass before fission takes place. Naturally-occurring uranium consists of 2 isotopes, U-238 (99.3%) & U-235 (0.7 %).  It is the rare isotope (U-235) which undergoes fission.

  8. Chain reaction When a uranium nucleus splits, 2 or 3 neutrons are emitted. neutron U-235 nucleus splits If these neutrons carry on splitting other uranium nucleus...

  9. Chain reaction escapes self-sustaining  chain reaction neutron U-235 nucleus splits

  10. Chain reaction If a small piece of uranium is used,  the fraction of neutrons escaping. If the mass of uranium is below a critical mass,  the chain will break very quickly.

  11. Nuclearfission

  12. 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 achain 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 ofE-N-E-R-G-Y

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

  14. Nuclear Fusion • Fusion occurs when two nuclei with low masses are combined to form one nucleus of larger mass. • Can only happen when the nuclei are moving fast enough to get “close” to each other • Temperature in stars are high enough for fusion to occur (millions of degrees Celsius) FUSION video clip

  15. Nuclear fusion A HUGE AMOUNT of energy is also released when two light nuclei join together to form a heavy nucleus. This process is called nuclear fusion.

  16. Nuclear fusion H H He n 3 2 1 4 2 1 1 0 hydrogen-2 nucleus hydrogen-3 nucleus fusion neutron helium-4 + + + energy

  17. Nuclear fusion H H He n 3 2 1 4 2 1 1 0 + + + energy Since nuclei carry “+” charges, they repel each other. For fusion to occur, the 2 hydrogen nuclei must approach each other with very high speed.  hydrogen gas of high temperature (108 C)!

  18. Nuclear fusion Nuclear fusion occurs in the core of the Sun, giving out heat and light. The reaction takes place continuously for billions of years.

  19. Q1 Which of the following… Which of the following elements is used in nuclear fission? A U-235 B U-238 C Hydrogen D Helium

  20. Q2 According to Einstein’s… According to Einstein’s mass-energy equation E = mc2, what is the amount of energy produced if 1 kg of a certain element completely changes into energy? A 3  108 J B 3  1016 J C 6  1016 J D 9  1016 J

  21. Q3 In nuclear… (U) fission In nuclear ___________, nuclei of uranium are split into smaller pieces and large amount of energy will be released. In order to maintain the ___________ reaction, mass of uranium used should exceed the __________ mass. chain critical

  22. Q4 In nuclear… (H) fusion In nuclear __________, nuclei of hydrogen are joined together and ____________ nucleus is formed. helium

  23. 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.

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

  25. 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

  26. U.S. Electrical Power Production by Source Source: EIA (2004)

  27. 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

  28. 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.

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