8
1 Nuclear Chemistry
and scientists are trying to produce fissionable material from thorium. It is expected
that thorium might replace Uranium as a nuclear fuel in nuclear reactors.
232 Th 90
is a fertile material from which
233 U 92 can be generated. Thus like
238 U 92 which is
used to produce
239 Pu 93 , Thorium-232 can be used in a breeder reactor to produce
Uranium-233. Hence, like Uranium-238, Thorium-232 can be used to develop two
generation reactors.
232 Th 90 when it captures neutrons (irrespective of whether in a
fast breeder reactor or a thermal reactor) produces
233 Th 90 . This emits an electron
and anti-neutrino (ν) by β-decay to become
233 U 92 as shown in the decay scheme:
1 n 0 +
232 Th 90 →
233 Th
β
90 →
233 Pa
β
91 →
233 U 92
In future, we may see many Thorium-based breeders and thermal reactors in India
and then shall not be dependent on other countries to get the fissionable Uranium-233
element.
1.6.2 Fusion Reaction
One of the disadvantages of a fission reaction is that it produces a large quantity of
radioactive isotopes and some of them have a half-life of several years. Hence, the
disposal of radioactive material is a problem with such type of reactor. Alternatively,
H or He can also undergo a similar fission reaction synthesizing higher mass number
nuclides (Fig. 1.1). The energy released is also almost the same as the uranium fission
reaction. The advantage of this type of reaction is that it produces no radioactive
isotopes, and it does not produce a mass number of atoms greater than 12. Since in
such reactions, two atoms are combined or are fused together to produce an atom
with higher binding energy, this reaction to distinguish it from the Uranium fission
reaction is called the Fusion reaction. It is clear from Fig. 1.1 that
4 He 2 has the
maximum mass difference among the lighter atoms. This suggests that H is unstable
in comparison to the He atom. In order to form one He atom, 4 H atoms are required.
The quantification of mass difference can be obtained by considering the masses of
H and He atoms
Mass of 4
1 H 1 = 4 × 1.00728 a.m.u.
= 4.02912 a.m.u.
Mass of
4 He 2 atoms = 4.00150 a.m.u.
Mass difference or excess mass released by the formation of
4 He 2 atom = 0.02761
a.m.u. × 931 = 25.7 MeV. This means that when 4 atoms of H are fused to get He
atoms, they release 25.7 MeV energy. Thus, the energy released in the H fusion
reaction per four He is 25.7 MeV. A by-product of the H fusion reaction is the
formation of a He atom.
1 Nuclear Chemistry
and scientists are trying to produce fissionable material from thorium. It is expected
that thorium might replace Uranium as a nuclear fuel in nuclear reactors.
232 Th 90
is a fertile material from which
233 U 92 can be generated. Thus like
238 U 92 which is
used to produce
239 Pu 93 , Thorium-232 can be used in a breeder reactor to produce
Uranium-233. Hence, like Uranium-238, Thorium-232 can be used to develop two
generation reactors.
232 Th 90 when it captures neutrons (irrespective of whether in a
fast breeder reactor or a thermal reactor) produces
233 Th 90 . This emits an electron
and anti-neutrino (ν) by β-decay to become
233 U 92 as shown in the decay scheme:
1 n 0 +
232 Th 90 →
233 Th
β
90 →
233 Pa
β
91 →
233 U 92
In future, we may see many Thorium-based breeders and thermal reactors in India
and then shall not be dependent on other countries to get the fissionable Uranium-233
element.
1.6.2 Fusion Reaction
One of the disadvantages of a fission reaction is that it produces a large quantity of
radioactive isotopes and some of them have a half-life of several years. Hence, the
disposal of radioactive material is a problem with such type of reactor. Alternatively,
H or He can also undergo a similar fission reaction synthesizing higher mass number
nuclides (Fig. 1.1). The energy released is also almost the same as the uranium fission
reaction. The advantage of this type of reaction is that it produces no radioactive
isotopes, and it does not produce a mass number of atoms greater than 12. Since in
such reactions, two atoms are combined or are fused together to produce an atom
with higher binding energy, this reaction to distinguish it from the Uranium fission
reaction is called the Fusion reaction. It is clear from Fig. 1.1 that
4 He 2 has the
maximum mass difference among the lighter atoms. This suggests that H is unstable
in comparison to the He atom. In order to form one He atom, 4 H atoms are required.
The quantification of mass difference can be obtained by considering the masses of
H and He atoms
Mass of 4
1 H 1 = 4 × 1.00728 a.m.u.
= 4.02912 a.m.u.
Mass of
4 He 2 atoms = 4.00150 a.m.u.
Mass difference or excess mass released by the formation of
4 He 2 atom = 0.02761
a.m.u. × 931 = 25.7 MeV. This means that when 4 atoms of H are fused to get He
atoms, they release 25.7 MeV energy. Thus, the energy released in the H fusion
reaction per four He is 25.7 MeV. A by-product of the H fusion reaction is the
formation of a He atom.