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Understanding Nuclear Physics: From Bombs to Power Plants

Learn about radioactive decay, half-life, fission, uranium decay sequence, nuclear reactors, risks of nuclear power, safety measures, and advantages of nuclear energy. Discover key concepts in fission and fusion reactions.

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Understanding Nuclear Physics: From Bombs to Power Plants

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  1. Nuclear physicsBombs, power plants

  2. Requires a metastable nucleus, such as 238U. Radioactive decay

  3. Requires a metastable nucleus, such as 238U. 238U is essentially 234Th + 4He (a particle). Radioactive decay

  4. Requires a metastable nucleus, such as 238U. 238U is essentially 234Th + 4He (a particle). Because of q.m., a has a wave function Radioactive decay

  5. Requires a metastable nucleus, such as 238U. 238U is essentially 234Th+ 4He (a particle). Because of q.m., a has a wave function Decay occurs by tunneling. Lower potential energy means higher kinetic energy. Radioactive decay

  6. Decay rate In each time interval dt, a certain fraction dN/N of the nuclei decay. This gives a solution: Half-life:

  7. Any radioactive nucleus can decay at any moment. Half life is related to probability: Low prob. -> long half life High prob. -> short half life Half life

  8. Decay examples Half-life is the time it takes half the material to decay. Carbon used for dating (formerly) living things.

  9. How much energy is released in one Uranium decay? This is roughly a million times more energy than is released in a typical chemical reaction, such as burning methane or nitroglycerin (the explosive chemical in dynamite).

  10. Where do the elements come from?

  11. Stability diagram Heavy elements can fission into lighter elements that are more stable. Elements from helium to iron were manufactured in the cores of stars by fusion. Heavier elements are metastable and were made during supernovae explosions. Light elements can undergo fusion into heavier elements that are more stable.

  12. Uranium decay sequence(one path)

  13. Uranium decay sequence(one path) Radon is the first isotope in the sequence that is a gas. Uranium occurs naturally in the soil around here, but is not a direct problem because the soil shields the alphas. However, radon, being a gas, rises into our homes causing lung cancer.

  14. Hitting a radioactive nucleus with a neutron can cause it to split into several pieces: FISSION. Energy is released. If you have enough, chain reaction! Fission

  15. Chain reaction For reaction to be self-sustaining, must haveCRITICAL MASS.

  16. Fission bomb

  17. Nuclear reactors

  18. Reactor explosion Risks of nuclear power

  19. Reactor explosion Risks of nuclear power

  20. Reactor explosion Risks of nuclear power • Radiation release from plant. • Storage • Leakage • inert ceramics fix • Inadvertent entry • Terrorist threat

  21. Reactor explosion Risks of nuclear power • Radiation release from plant. -- TMI • Storage • Leakage • inert ceramics fix • Inadvertent entry • Terrorist threat We do not have to worry about reactor fuel stolen for bombs, because it is not sufficiently enriched. • Processing accidents

  22. Tokaimura, Japan September 28, 1999 • Japan’s nuclear industry’s first critical accident. • Inadvertent critical mass • Container size: 16 kg instead of 2.4 • Container shape 10 liters 16 kg Two of three workers died within seven months.

  23. Nuclear power’s track record shows it is among safest energy sources. Wind and hydroelectric are limited. Coal is dangerous (pollution kills). Solar would require huge construction, with accompanying construction accidents. How safe is nuclear power?

  24. Yes! Better training and on-site monitoring by agents paid by government, not power companies. In the event of accident, can almost completely eliminate radiation danger with iodine tablets. Buy your own! Can we make it safer?

  25. No pollution (except thermal, like any heat engine) No lung cancer, emphysema, etc. No greenhouse effect Fewer mining accidents than coal. Advantages of nuclear power

  26. Light nuclei more stable when combined. Tremendous energy release. Hard to do, because nuclei are positive and repel each other. Hydrogen bombs Require a fission bomb to ignite. Fusion power? Controlled fusion is very, very hard. Will not be possible for many, many years. Fusion Example:

  27. Key concepts • Radioactive decay • Fission • Fusion • Critical mass • Alpha decay and alpha particle • Beta decay and beta particle. • How do fission bombs work? • How do fusion bombs work? • How do nuclear reactors work?

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