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Nuclear Fission

Nuclear Fission. Historic Dates Fission Mechanism Binding Energy Liquid-Drop Model Classification of Heavy Nuclides Prompt Neutrons Delayed Neutrons. Historic Introduction. 1932: The neutron is discovered by J.Chadwick → experiments with neutrons.

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Nuclear Fission

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  1. Nuclear Fission • Historic Dates • Fission Mechanism • Binding Energy • Liquid-Drop Model • Classification of Heavy Nuclides • Prompt Neutrons • Delayed Neutrons T8: Fission

  2. Historic Introduction • 1932: The neutron is discovered byJ.Chadwick → experiments with neutrons. • 1939: Bombardment of U gives medium-heavy atoms (Ba), O.Hahn and F.Strassman; L.Meitner explains; E.Fermi and co-workers did not recognize fission. • 1940: Spontaneous Fission (SF) is discovered by G.N.Flerov and K.A.Petrzhak. • 1947: Ternary fission is discovered by Qian Sabqiang and He Zehui. T8: Fission

  3. Basic Notation • Z is the number of protons, charge number or atomic number • N is the number of neutrons • A = Z + N is the number of nucleons,A is called the mass number • is a specific nucleus, X– chem. sym. • is in an excited state T8: Fission

  4. Nuclides and Isotopes • Isotope ≡ atoms with same Z and A • Nuclide = atoms/nuclei with same Z and A and being in a specific energy state • Isomer = long-lived excited states, T8: Fission

  5. Nuclear Energy Production T8: Fission

  6. Fission Process Ternary: 1/400 0.00650.7% T8: Fission

  7. Compound Nucleus T8: Fission

  8. Binding Energy T8: Fission

  9. Energy Release T8: Fission

  10. Fission Energy T8: Fission

  11. Liquid-Drop Model Nuclear force Surface force Coulomb repulsion Stability maximum Spin factor T8: Fission

  12. Fissionable Ratio T8: Fission

  13. Excitation Energy AX A+1X* T8: Fission

  14. Classification of Heavy Nuclides T8: Fission

  15. Examples of Fission T8: Fission

  16. Fission Product Yield T8: Fission

  17. Kinetic Energy Distribution T8: Fission

  18. Energy Released in Fission T8: Fission

  19. Prompt Neutrons 239Pu 235U 233U E = 1 T8: Fission

  20. Prompt Neutron Energy T8: Fission

  21. E 87Br T½ = 54.5s β– (2%) 87Kr* 86Kr + n β– (98%) 87Kr 87Rb 87Sr t Delayed Neutron Precursors T8: Fission

  22. Delayed Neutron Groups T8: Fission

  23. Delayed Neutron Spectra T8: Fission

  24. Microscopic Cross Section Background material detector Δx Reaction rate R = #/(sm2sec) θ Monoenergetic beam of neutrons I = n/(sm2 sec) x detector cross section σ Microscopic cross section σ is defined by R = σ× I × NB [#/(sm2 sec)] = [sm2] ×[#/(sm2sec)]×[#/sm2] σ/A = Probability per nucleus that a neutron in the beam will interact with it T8: Fission

  25. Fission Cross Section T8: Fission

  26. Resonances T8: Fission

  27. 235U vs. 238U T8: Fission

  28. The END T8: Fission

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