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Physics for Scientists and Engineers, 6e
Chapter 45 - Applications of Nuclear Physics
Which of the following is a possible set of products
for a fission reaction in which two neutrons are
released?
1.
25% 25% 25% 25%
2.
3.
4.
1
2
3
4
5
1
2
3
4
This is the only set of products of the four
that satisfies the conditions that the atomic
numbers add to 92 and the atomic mass
numbers add to 234, (allowing for two
neutrons to make up the total of 236).
When a nucleus undergoes fission, the two
daughter nuclei are generally radioactive. By
which process are they most likely to decay?
1
1.
alpha decay
2.
beta decay (e–)
3.
beta decay (e+)
2
3
4
5
33%
1
33%
2
33%
3
According to Figure 44.4, the ratio N/Z
increases with increasing Z. As a result,
when a heavy nucleus fissions to two
lighter nuclei, the lighter nuclei tend to
have too many neutrons for the nucleus
to be stable. Beta decay in which
electrons are ejected decreases the
number of neutrons and increases the
number of protons in order to stabilize
the nucleus.
Which of the following has the function of slowing
down fast neutrons?
1
1.
control rods
2.
moderator
3.
fuel elements
2
3
4
5
33%
1
33%
2
33%
3
Collisions of the neutrons with
moderator nuclei slow them down.
To reduce the value of the reproduction constant K,
you would:
1.
2.
1
2
push the control rods
deeper into the core
50%
50%
pull the control rods
farther out of the core
3
4
5
1
2
To reduce the value of K, more neutrons
need to be absorbed, so a larger volume
of the control rods must be inside the
reactor core.
In the core of a star, hydrogen nuclei combine in fusion
reactions. Once the hydrogen has been exhausted, fusion of
helium nuclei can occur. Once the helium is used up, if the star
is sufficiently massive, fusion of heavier and heavier nuclei can
occur. Consider fusion reactions involving two nuclei with the
same value of A. For these types of reactions, which of the
following values of A are impossible?
25% 25% 25% 25%
1
1.
12
2.
20
3.
28
4.
64
2
3
4
5
1
2
3
4
Figure 44.5 shows that the curve representing
the binding energy per nucleon peaks at A ≈ 60.
Consequently, combining two nuclei with equal
values of A > 60 results in an increase in mass,
so that a fusion reaction will not occur.