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The Fission Mechanism: Understanding Nuclear Energy and Chain Reactions

This document explores the fundamental concepts of nuclear fission, detailing the fission mechanism, spontaneous fission, and neutron-induced fission. It examines key processes such as chain reactions and their regimes—sub-critical, critical, and supercritical—alongside the energy released during fission. References to notable discoveries and contributions in nuclear physics, including the works of Enrico Fermi and the discovery of fission fragments like Barium, are also included. The importance of understanding these mechanisms is crucial for the development and utilization of nuclear energy.

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The Fission Mechanism: Understanding Nuclear Energy and Chain Reactions

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  1. 06.12.2011 Nuclear Power The Fission Mechanism And Nuclear Energy

  2. FISSION • Fission Mechanism, Spontaneous Fission • Neutron-Induced Fission, Chain Reaction • Nuclear Energy

  3. FISSION • Fission Mechanism, Spontaneous Fission • Neutron-Induced Fission, Chain Reaction • Nuclear Energy

  4. Fission Mechanism: fission barrier spherical nucleus

  5. Spontaneous Fission: Fissility(derivation: Demtröder 4, p.164) • surface: • Coulomb: spontaneous fission: → fissility: → spontaneous fission: or example: : … deformation Bethe-Weizsäcker-formula

  6. FISSION • Fission Mechanism, Spontaneous Fission • Neutron-Induced Fission, Chain Reaction • Nuclear Energy

  7. Neutron-Induced Fission 1934 Enrico Fermi: new elements by impact of neutrons on Uranium → β-active products 1939 F. Straßmann, Lise Meitner, O. Hahn: - discovered Barium as one of these products => fission:

  8. Neutron-Induced Fission Uranium Plutonium

  9. Neutron-Induced Fission: Fission Fragments minimum: maximum:

  10. Chain Reaction

  11. Chain Reaction • chain reaction: • since , a multi- plicative effect can occur • number of neutrons will be multiplied • reaction rate incrases

  12. Chain Reaction: Multiplication Factor supercritical regime → chain reaction • sub-critical regime → no chain reaction critical regime → constant reaction • dependency: • non fissioning absorbtion • diffusion • … • mass (k=1 => critical mass)

  13. FISSION • Fission Mechanism, Spontaneous Fission • Neutron-Induced Fission, Chain Reaction • Nuclear Energy

  14. Nuclear Energy • exothermic nuclear reactions: • α-decay: • fission: • energy release for : → … sum of the kinetic energies of the fission fragments

  15. Binding energy per nucleon B/A(120) = 8.5MeV B/A(240) = 7.6MeV

  16. Picture Credits • http://www.zamandayolculuk.com/cetinbal/nuclearchemistry.htm • A.Junghans • http://frank.mtsu.edu/~phys3110/Syllabus/Examples/CH_11/EX_11_VII/ex_11_vii.html • W. Demröder: (Springer, Heidelberg, 1998) Kern-, Teilchen- und Astrophysik 4 • http://www3.mpch-mainz.mpg.de/~elbert/geschichte.htm • J.Grehn, J.Krause: (Schroedel Verlag, Hannover, 1998) Metzler Physik • http://clautechonolgyblog.wordpress.com/ • http://thushararadioactivity.blogspot.com/ • J.L.Basdevant, J.Rich, M. Spiro: (Springer, Heidelberg, 2005) Fundamentals in Nuclear Physics • http://www.nucleonica.net/wiki/images/d/d4/NuclideChart.pdf

  17. References • J.L.Basdevant, J.Rich, M. Spiro: (Springer, Heidelberg, 2005) Fundamentals in Nuclear Physics – From nuclear structure to cosmology • W. Demröder: (Springer, Heidelberg, 1998) Kern-, Teilchen- und Astrophysik 4 • Horst Hänsel / Werner Neuman: (Spektrum, Akad. Verl., Heidelberg, Berlin, Oxford, 1995) Physik – Atome, Atomkerne, Elementarteilchen • Dr. Arnd Junghans (Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics)

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