1. Resonance Reactions HW 34 In the 19F(p,) reaction:
The Q-value is 8.??? MeV.
The Q-value for the formation of the C.N. is 12.??? MeV.
For a proton resonance at 668 keV in the lab system, the corresponding energy level in the C.N. is at 13.??? MeV.
If for this resonance the observed gamma energy is 6.13 MeV, what is the corresponding alpha particle energy?
If for this resonance there has been no gamma emission observed, what would then be the alpha particle energy?
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

2. Neutron Resonance Reactions
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

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

4. Neutron Attenuation Similar to -attenuation. Why? Neutrons Target
Thickness “x”
Similar to -attenuation. Why?
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

5. Neutron Moderation
HW 35
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 n s-wave collisions:
where
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

6. Neutron Moderation HW 35 (continued)
How many collisions are needed to thermalize a 2 MeV neutron if the moderator was:
1H 4He 238U
Discuss the effect of the thermal motion of the moderator atoms.
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

7. Nuclear Fission Surface effect Coulomb effect ~200 MeV  Fission
Fusion 
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

8. Nuclear Fission B.E. per nucleon for 238U (BEU) and 119Pd (BEPd) ?
2x119xBEPd – 238xBEU = ??  K.E. of the fragments   1011 J/g
Burning coal  105 J/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…!
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

9. 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 above g.s. is called activation energy.
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

10. Nuclear Fission Liquid Drop Shell Activation Energy (MeV)
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

11. Nuclear Fission =  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, 1st Semester, (Saed Dababneh).

12. Nuclear Fission Consistent with activation energy curve for A = 300.
Extrapolation to 47   s.
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

13. Low-energy fission processes.
Nuclear Fission
235U + n 
93Rb + 141Cs + 2n
Not unique.
Low-energy fission processes.
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

14. 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 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, 1st Semester, (Saed Dababneh).

15. Nuclear Fission
The average number of neutrons is different, but the distribution is Gaussian.
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

16. 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, 1st Semester, (Saed Dababneh).

17. Nuclear Fission
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).

18. Nuclear Fission 1/v 235U thermal cross sections fission  584 b.
Fast neutrons should be moderated.
235U thermal cross sections
fission  584 b.
scattering  9 b.
radiative capture  97 b.
Fission Barriers
Nuclear and Radiation Physics, BAU, 1st Semester, (Saed Dababneh).