Biomedical Engineering Reference
In-Depth Information
Estimate the capture cross section of
10
B for 100-eV
neutrons.
19.
(a)
(b)
What is the capture probability per cm for a 100-eV
neutron in pure
10
B (density
= 2.17
gcm
-3
)?
(c)
Estimate the probability that a 100-eV neutron will
penetrate a 1 cm
10
B shield and produce a fission in a
1-mm
239
Pu foil (density 18.5 g cm
-3
) behind it. Neglect
energy loss of the neutron due to elastic scattering.
The thermal-neutron reaction
1
5
B(n,
)
3
Li
leaves the
3
Li
nucleus in the ground state 4% of the time. Otherwise, the
reaction leaves the
3
Li
nucleus in an excited state, from which
it decays to the ground state by emission of a 0.48-MeV gamma
ray.
(a)
20.
α
Calculate the
Q
value of the reaction in both cases.
(b)
Calculate the alpha-particle energy in both cases.
21.
How much energy is released per minute by the
1
7
N(n, p)
1
6
C
reaction in a 10-g sample of soft tissue bombarded by 2
10
10
thermal neutrons
cm
-2
s
-1
? Nitrogen atoms constitute 3% of
the mass of soft tissue.
×
Calculate the
Q
value for the reaction
3
H(p, n)
3
He
.
22.
(a)
(b)
What is the threshold energy for this reaction when
protons are incident on a tritium target?
23.
How much kinetic energy is associated with the center-of-mass
motion in the last problem?
24.
Calculate the threshold energy for neutron production by
protons striking a lithium target via the reaction
7
Li(p,n)
7
Be.
25.
Calculate the maximum energy of the neutrons produced when
10-MeV protons strike a
7
Li target.
26.
Verify Eqs. (9.20)-(9.29).
A sample containing 127 g of
23
Na (100% abundant) is exposed
to a beam of thermal neutrons at a constant fluence rate of
1.19
27.
10
4
cm
-2
s
-1
. The thermal-neutron capture cross section
for the reaction
23
Na(n,
×
)
24
Na
is 0.53 barn.
γ
(a)
Calculate the saturation activity.
(b)
Calculate the
24
Na activity in the sample 24 h after it is
placed in the beam.
(c)
How many
23
Na atoms are consumed in the first 24 h?
28.
What is the saturation activity of
24
Na that can be induced in a
400-g sample of NaCl with a constant thermal-neutron fluence
rate of 5
10
10
cm
-2
s
-1
? The isotope
23
Na is 100% abundant
and has a thermal-neutron capture cross section of 0.53 barn.
×
A sample containing 62 g of
31
P (100% abundant) is exposed to
2
29.
10
11
thermal neutrons
cm
-2
s
-1
. If the thermal-neutron
capture cross section is 0.19 barn, how much irradiation time
is required to make a 1-Ci source of
32
P?
×
