3.3 Reactions Initiated by Uncharged Particles
35
directly used for carrying out the nuclear reaction. While in thermal neutron reaction,
the energy of a neutron is slowed down to the energy of 0.03–0.1 eV.
The energy of a fast neutron is lowered by allowing it to interact with materials like
pure graphite (known as moderator). This material instead of absorbing allows the
neutron to undergo several collisions. In each collision, the neutron loses its kinetic
energy and finally after several collisions, it becomes a thermal neutron.
3.3.1 Thermal Neutron Reaction
The most common type of nuclear reaction induced by a thermal neutron is the
radioactive capture process, represented by (n, γ ) in which a slow neutron is absorbed
by the target. The excess energy (i.e., the difference between the energy of the interacting neutron and energy of the target nucleus) is emitted in the form of radiation.
The product of such a nuclear reaction is the isotope of the target material with its
mass number one unit higher. For example, thermonuclear reaction with Chlorine-35
present in Na
35 Cl will give an isotope of Chlorine-36 as Na
36 Cl.
3.3.2 Fast Neutron Reaction
With fast neutrons, that is to say, with neutrons possessing energies in the range of
1–2 MeV, (n, p) type reaction is fairly common; high energy is required to permit the
proton to escape from the compound nucleus (i.e., intermediate nucleus formed after a
neutron has been absorbed by the parent nuclei). In such reactions, e.g.,
35 Cl(n, p)
35 S,
the product nucleus has the same mass but its atomic number is one unit less than that
of the target. The advantage of this type of reaction is that radioactive materials of
high specific activity can be obtained because the product nucleus is different from
parent one.
Another example of a high energy nuclear reaction is with fast neutrons (possessing energy about 10 MeV energy). Such neutron undergoes a (n, 2n) type reaction,
e.g.,
238 U 92 +
1 n 0 →
237 U 92 + 2
1 n 0
3.3.3 Nuclear Fission Reaction
Another important neutron-induced reaction is the fission of higher mass number
elements, e.g., Uranium-235 and Plutonium-239, which is also accompanied by the
emission of neutrons (approximately two or three neutrons per fission) and the liberation of energy. Consequently, it is possible for the process to be self-sustaining,
35
directly used for carrying out the nuclear reaction. While in thermal neutron reaction,
the energy of a neutron is slowed down to the energy of 0.03–0.1 eV.
The energy of a fast neutron is lowered by allowing it to interact with materials like
pure graphite (known as moderator). This material instead of absorbing allows the
neutron to undergo several collisions. In each collision, the neutron loses its kinetic
energy and finally after several collisions, it becomes a thermal neutron.
3.3.1 Thermal Neutron Reaction
The most common type of nuclear reaction induced by a thermal neutron is the
radioactive capture process, represented by (n, γ ) in which a slow neutron is absorbed
by the target. The excess energy (i.e., the difference between the energy of the interacting neutron and energy of the target nucleus) is emitted in the form of radiation.
The product of such a nuclear reaction is the isotope of the target material with its
mass number one unit higher. For example, thermonuclear reaction with Chlorine-35
present in Na
35 Cl will give an isotope of Chlorine-36 as Na
36 Cl.
3.3.2 Fast Neutron Reaction
With fast neutrons, that is to say, with neutrons possessing energies in the range of
1–2 MeV, (n, p) type reaction is fairly common; high energy is required to permit the
proton to escape from the compound nucleus (i.e., intermediate nucleus formed after a
neutron has been absorbed by the parent nuclei). In such reactions, e.g.,
35 Cl(n, p)
35 S,
the product nucleus has the same mass but its atomic number is one unit less than that
of the target. The advantage of this type of reaction is that radioactive materials of
high specific activity can be obtained because the product nucleus is different from
parent one.
Another example of a high energy nuclear reaction is with fast neutrons (possessing energy about 10 MeV energy). Such neutron undergoes a (n, 2n) type reaction,
e.g.,
238 U 92 +
1 n 0 →
237 U 92 + 2
1 n 0
3.3.3 Nuclear Fission Reaction
Another important neutron-induced reaction is the fission of higher mass number
elements, e.g., Uranium-235 and Plutonium-239, which is also accompanied by the
emission of neutrons (approximately two or three neutrons per fission) and the liberation of energy. Consequently, it is possible for the process to be self-sustaining,