Al-Balqa Applied University Nuclear Physics Final Exam Dr. Saed ...

Al-Balqa Applied University
Nuclear Physics
Final Exam
Dr. Saed Dababneh January 17 th , 2008
Question 1
a) Find the macroscopic thermal neutron absorption cross section for iron, which has a
density of 7.86 g.cm -3 . The microscopic absorption cross section of iron is 2.56 barns
and the gram atomic weight is 55.847 g. [3]
b) A reactor operating at a flux level of 3x10 13 neutrons.cm -2 s -1 contains 10 20 atoms of
235 U per cm 3 . The reaction rate is 1.29x10 12 fissions.cm -3 s -1 . Calculate Σ f and σ f . [3]
c) How many collisions are required to thermalize a neutron from an energy of 2 MeV
using water as the moderator Water has a value of 0.948 for the average change in
lethargy. [3]
d) Calculate the thermal utilization factor for a homogeneous reactor both at startup with
fresh fuel and after poison buildup. What is the negative reactivity due to this poison
The macroscopic absorption cross section of the fuel is 0.3020 cm -1 , of the moderator
is 0.0104 cm -1 , and of the poison is 0.0118 cm -1 . [5]
e) Calculate η for a reactor that uses 10% enriched uranium fuel. The total microscopic
absorption cross section for 235 U is 694 barns and for 238 U is 2.71 barns. The
microscopic fission cross section for 235 U is 582 barns. The atom density of 235 U is
4.83x10 21 atoms/cm 3 and of 238 U is 4.35x10 22 atoms/cm 3 . ν is 2.42. [4]
f) In the 19 F(p,αγ) reaction, what is the Q-value for the reaction and for the formation of
the compound nucleus For a proton resonance at 668 keV in the lab system, what is
the corresponding energy level in the compound nucleus 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 [5]
Question 2 [7]
The shell model level scheme leads us to expect
π 11 −
= 2
I for the ground state of 203 Tl (Why),
1
while the observed value is +
. Give the shell model configuration of this nucleus that is
2
consistent with the observation and comment on the nuclear physics phenomenon responsible
for this configuration.
Question 3 [5]
If the energy of a single particle state in the absence of spin-orbit splitting is E 0 , find the
energies of the two members of the spin-orbit doublet whose difference is given by
1
2
(2l + 1) h .
2
Question 4 [5]
Tritium can be produced through the absorption of low energy neutrons by
2
3
deuterium H + n→
H + γ (6.256MeV
) . Show that the recoil energy of 3 H is about 7 keV.
Calculate the difference in binding energy between the two hydrogen isotopes. Comment on
the result.

Question 5 [5]
By tabulating the possible m states of three quadrupole phonons and their symmetrized
combinations, show that the permitted resultant states are 0 + , 2 + , 3 + , 4 + , 6 + .
Question 6 [5]
Show that for a (d,p) reaction taking place on the surface of a 90 Zr nucleus, and with 5 MeV
deuterons, the angular momentum transfer can be approximated by l = 8sin(θ/2), where θ is
the angle the outgoing proton makes with the incident deuteron direction.