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NE 301 - Introduction to Nuclear Science Spring 2012

NE 301 - Introduction to Nuclear Science Spring 2012. Classroom Session 4: Radioactive Decay Types Radioactive Decay and Growth Isotopes and Decay Diagrams Nuclear Reactions Energy of nuclear reactions Neutron Cross Sections Activation Calculations. Reminder. Load TurningPoint

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NE 301 - Introduction to Nuclear Science Spring 2012

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  1. NE 301 - Introduction to Nuclear ScienceSpring 2012 Classroom Session 4: Radioactive Decay Types Radioactive Decay and Growth Isotopes and Decay Diagrams Nuclear Reactions Energy of nuclear reactions Neutron Cross Sections Activation Calculations

  2. Reminder • Load TurningPoint • Reset slides • Load List

  3. The Energy Released (or consumed), Q Change in BE: Or since BE is related to mass defect Change in M: A + B  C + D + E Preferred! because we have table B.1. Remember:The Equation Has to BeBALANCED!

  4. Please remember… BALANCE! Before starting to work

  5. Main Radioactive Decay Modes (Table 5.1 -page 89-Shultis)

  6. Kinetic Energy of Radioactive Decay Products • Parent nucleus is at rest (Eth~ 0.025 eV~17 oC) • Conservation of Linear Momentum and Kinetic Energy requires products to travel in opposite directions (2 product). v2 m2 m2 m1 m1 m1v1=m2v2 Original atom that will split in 2 pieces v1 Q=½ m1v12+ ½ m2v22 What is the energy of emitted particle? (it is what we measure)

  7. Kinematics of radioactive decay… Notice 2:1

  8. Main Radioactive Decay Modes (Table 5.1 -page 89-Shultis)

  9. Beta Decay Remember: ’sDO NOT have exactly defined energies 3 body interactions Max energy = neutrino took zero energy away… What is this energy? Page 554 11

  10. -, + produce three products: • Cannot say energy of  • Neutrinos by Fermi (1933) • We only can say maximum energy of  • Page 98-Shultis

  11. Similarly for ’s

  12. Kinetic Energy of De-excitation Decay In principle gamma () photons would have Q of the reaction, but… Q=2.50 MeV • Details of the decays are needed to predict the correct  spectrum. • Radioactive Decay Diagrams (e.g. book) • Write all 3 rxn shown

  13. Radioactive Decay Diagrams… • In figure 5.6 • Write all the reactions indicated in the diagram. If initially we have 100 g of 64Cu, how much Zn and Ni will we have after all Cu has decayed?

  14. Branching Decay Example

  15. Branching Decay Example

  16. On to

  17. Binary Nuclear Reactions • Binary = 2 reactants (many times 2 products too) • Most important type of nuclear reaction • Most elements produced by binary rxns. in stars • Nomenclature: Light nuclide usually projectile Light Product Heavy Product Heavy nuclide usually target

  18. Binary Reactions • (,p) • First reaction reported by Rutherford: • Nitrogen in air bombarded by alphas producing protons • (,n) • In 1932, the neutron was discovered (Chadwick). • Rxn. still used in some neutron generators today or or

  19. Example Binary Reactions, cont. • (,n) • Photo-nuclear rxns: Highly energetic gamma rays can knock neutrons out of the nucleus. • (n,p) • Fast neutrons react with oxygen in the water in a reactor core producing radioactive 16N. or or or

  20. Mechanisms of Nuclear Reactions • Direct Interactions • Projectiles w/ KE>40MeV have de Broglie wavelengths ~ size of a nucleon in target nucleus • Usually interact with individual nucleons • Near surface of nucleus (peripheral reactions) • Compound Nucleus • Projectiles w/ KE ~ MeVhave de Broglie wavelengths ~ size of the whole target nucleus • Usually interact with whole nucleus • Forms compound, highly excited nucleus Products have no “memory” of the reactants.

  21. Reaction Nomenclature: • Transfer Reactions • (,d) (d,n) • Scattering Reactions • (x,x) elastic • (x,x’) inelastic • Knockout Reactions • (n,2n) (n,3n) (n,np) • Capture • (n,) • Photo-Nuclear • (,n) Direct Reactions 1-2 nucleons transfer between projectile and target projectile and target remain the same (it is a collision) Direct Reaction: Original projectile emerges and is accompanied by other nucleons (i.e. spallation: SNS) Projectile is absorbed by target nucleus (usually leaving it excited) Strong gamma kicks nucleon from the target nucleus

  22. For Binary Reactions: x +X  Y + y • x is a projectile with KE (Ex). X is a target stationary nucleus EX=0 simplification

  23. A 5.5 MeV particle is incident on Li causing 7Li(,n)10B. What is the KE of neutron scattered 30o?

  24. A 5.5 MeV particle is incident on Li causing 7Li(,n)10B. What is the KE of neutron scattered 30o? • 0 MeV • 0.31 MeV • 1.31 MeV • 2.31 MeV • 3.31 MeV • 5.5 MeV

  25. FIRST BALANCE THE EQUATION!!! 7Li(alpha,n)10B Endothermic Rxn Neutron Energy = 1.31MeV What would be the neutron energy if incident alpha particle is 1MeV instead? Can’t happen…

  26. Solution exists only if • Potential “” Factors • Q<0 • Heavy projectiles (mY-mx<0) • Large scattering angles Cos <0 • Big enough Ex can guarantee • Physical meaning: Threshold Energy Argument of root >0

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