1 / 16

Neutron Resonance Reactions

Neutron Resonance Reactions. Neutron Activation Analysis. ( Z,A ) + n  ( Z , A+1 ).  -.  (-delayed -ray). ( Z+1 , A+1 ). Neutron Attenuation. Neutrons. Target Thickness “x”. Similar to -attenuation. Why?. Neutron Moderation. HW 44.

kipp
Download Presentation

Neutron Resonance Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Neutron Resonance Reactions Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  2. Neutron Activation Analysis (Z,A) + n (Z, A+1) -  (-delayed -ray) (Z+1, A+1) Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  3. Neutron Attenuation Neutrons Target Thickness “x” Similar to -attenuation. Why? Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  4. Neutron Moderation HW 44 Show that, after elastic scattering the ratio between the final neutron energy E\ and its initial energy E is given by: For a head-on collision: After ns-wave collisions: where Lethargy? Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  5. Neutron Moderation HW 44 (continued) How many collisions are needed to thermalize a 2 MeV neutron if the moderator was: 1H 2H 4He 12C 238U Discuss the effect of the thermal motion of the moderator atoms. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  6. Nuclear Fission Surface effect Coulomb effect ~200 MeV  Fission Fusion  Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  7. Nuclear Fission • B.E. per nucleon for 238U (BEU) and 119Pd (BEPd) ? • 2x119xBEPd – 238xBEU = ?? K.E. of the fragments  1011J/g • Burning coal  105J/g • Why not spontaneous? • Two 119Pd fragments just touching  The Coulomb barrier is: • Crude …! What if 79Zn and 159Sm? Large neutron excess, released neutrons, sharp potential edge…! Crude! Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  8. Nuclear Fission • 238U (t½ = 4.5x109 y) for -decay. • 238U (t½ 1016 y) for fission. • Heavier nuclei?? • Energy absorption from a neutron (for example) could form an intermediate state  probably above barrier  induced fission. • Height of barrier is called activation energy. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  9. Nuclear Fission Liquid Drop Shell Activation Energy (MeV) Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  10. Nuclear Fission = Volume Term (the same) Surface Term Bs = - as A⅔ Coulomb Term BC = - aC Z(Z-1) / A⅓  fission  Crude: QM and original shape could be different from spherical. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  11. Nuclear Fission Consistent with activation energy curve for A = 300. Extrapolation to 47  10-20 s. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  12. Nuclear Fission 235U + n  93Rb + 141Cs + 2n Not unique. Low-energy fission processes. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  13. Nuclear Fission Z1 + Z2 = 92 Z1  37, Z2  55 A1 95, A2  140 Large neutron excess Most stable: Z=45 Z=58  Prompt neutrons within 10-16 s. Number depends on nature of fragments and on incident particle energy. The average number is characteristic of the process. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  14. Nuclear Fission The average number of neutrons is different, but the distribution is Gaussian. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  15. Higher than Sn? Delayed neutrons ~ 1 delayed neutron per 100 fissions, but essential for control of the reactor. Follow -decay and find the most long-lived isotope (waste) in this case. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

  16. Nuclear Fission Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh).

More Related