36
3 Nuclear Reaction
and energy is generated continuously while the fuel is accessible. In the fission process, fissile material breaks up into approximately two equal parts, of mass numbers
about 85 and 105, with a release of the total energy of about 200 MeV per fission.
This energy is used for peaceful purposes, such as the generation of electricity. The
assembly for generating energy for peaceful purposes is called a nuclear reactor.
3.3.3.1 Laboratory Neutron Source
In a laboratory, neutrons are produced either by (γ , n) or (α, n) reaction. In the (α, n)
type neutron sources, an α-active radio-nuclei is thoroughly mixed with Beryllium
and sealed in a robust-stainless steel container. Proper sealing is very important in
order to make sure that radioactive emanation (e.g., radon from radium) does not leak
out of the capsule. When in use, the capsule is shielded for γ -radiation and neutrons.
α-active nuclei used in neutron sources are Actinium-227 (such sources are
cheaper), Radium-226, and Polonium-210. In each case, α-particles emitted from
radioactive elements collide with beryllium, to give neutrons.
9 Be 4 +
4 He 2 →
12 C 6 +
1 n 0
The Ra/Be neutron source seems to be the most useful because α-particle density
in the mixture is high, since various daughter products of Radium-226 are active.
However, a Po/Be neutron source, which has the disadvantage of a fairly short halflife, is not associated with a lot of γ -radiation. A Pu/Be neutron source also has this
advantage, coupled with a long half-life.
3.3.3.2 Interaction with Electromagnetic Radiations
Nuclear reactions initiated with electromagnetic radiations have been utilized to
prepared laboratory neutron source. Antimony-124 is produced by thermal neutron
(n, γ ) by irradiation of Antimony-123. This radioactive isotope (Antimony-124)
decays by γ -rays.
124 Sb 51 →
124 Te 52 + γ -rays
If this isotope is mixed with Beryllium-9, γ -rays emitted by Antimony-124 react
to produce thermal neutron.
9 Be 4
(γ ,n)
−−→
8 Be 4 +
1 n 0
This source is made by the hot compacting of equal volumes of powdered Beryllium and Antimony, and the sources are sheathed in aluminum. They are activated by
irradiation in a nuclear reactor to the required strength. An extra casing of the source
3 Nuclear Reaction
and energy is generated continuously while the fuel is accessible. In the fission process, fissile material breaks up into approximately two equal parts, of mass numbers
about 85 and 105, with a release of the total energy of about 200 MeV per fission.
This energy is used for peaceful purposes, such as the generation of electricity. The
assembly for generating energy for peaceful purposes is called a nuclear reactor.
3.3.3.1 Laboratory Neutron Source
In a laboratory, neutrons are produced either by (γ , n) or (α, n) reaction. In the (α, n)
type neutron sources, an α-active radio-nuclei is thoroughly mixed with Beryllium
and sealed in a robust-stainless steel container. Proper sealing is very important in
order to make sure that radioactive emanation (e.g., radon from radium) does not leak
out of the capsule. When in use, the capsule is shielded for γ -radiation and neutrons.
α-active nuclei used in neutron sources are Actinium-227 (such sources are
cheaper), Radium-226, and Polonium-210. In each case, α-particles emitted from
radioactive elements collide with beryllium, to give neutrons.
9 Be 4 +
4 He 2 →
12 C 6 +
1 n 0
The Ra/Be neutron source seems to be the most useful because α-particle density
in the mixture is high, since various daughter products of Radium-226 are active.
However, a Po/Be neutron source, which has the disadvantage of a fairly short halflife, is not associated with a lot of γ -radiation. A Pu/Be neutron source also has this
advantage, coupled with a long half-life.
3.3.3.2 Interaction with Electromagnetic Radiations
Nuclear reactions initiated with electromagnetic radiations have been utilized to
prepared laboratory neutron source. Antimony-124 is produced by thermal neutron
(n, γ ) by irradiation of Antimony-123. This radioactive isotope (Antimony-124)
decays by γ -rays.
124 Sb 51 →
124 Te 52 + γ -rays
If this isotope is mixed with Beryllium-9, γ -rays emitted by Antimony-124 react
to produce thermal neutron.
9 Be 4
(γ ,n)
−−→
8 Be 4 +
1 n 0
This source is made by the hot compacting of equal volumes of powdered Beryllium and Antimony, and the sources are sheathed in aluminum. They are activated by
irradiation in a nuclear reactor to the required strength. An extra casing of the source