Nuclear Fission
It is
the process of disintegration of a heavy nuclei when bombarded with slow moving
projectiles like neutrons.
During
nuclear fission, there is loss of some mass which gets converted into energy,
called fission energy. When U-235 isotope is bombarded with neutrons, U-236 is
formed. U-236 being unstable breaks into two fragments, i.e. Ba-141, and Kr-92.
The nuclear equation is written as follows:
92235U
+ 10n ž92236Už56141Ba+3692Kr+301n
The actual
mass of the products formed as a result of fission is found to be less than the
mass of the species before fission. The difference in mass is called mass
defect. The mass defect in this case is found to be 0.2135amu.
Hence, loss
in energy when 0.2135amu mass is lost= 0.2135×931.48 Me V=198.87Me
V
In the
above reaction, three neutrons produced can further disintegrate the uranium
nuclei and thus a chain reaction sets in producing a very large amount of
energy.
Nuclear Fusion
The nuclear reaction that involves the
combination or fusion of two lighter nuclei to form a stable nucleus of higher
mass is called nuclear fusion.
It is found
that nuclear fusion occurs at a very high temperature. Such a high temperature
prevails on the sun which is of the order of 10 million degree centigrade.
Clearly, sufficient energy is needed to overcome the repulsive forces and only
then the atomic nuclei fuse. The energy of the sun arises from the following
thermo nuclear reactions:
11H+11Hž12H++10e+Energy
11H+12Hž23He+Energy
23H+23Hž24He+211H+Energy
The net
loss of mass during the change is calculated as equal to 0.0286amu. It is
equivalent to 26.64 MeV.
Advantages
of Nuclear Fusion
(i)
There
is no problem of pollution due to nuclear wastes.
(ii)
The
fusion energy is greater than fission energy.
(iii)
Only
lighter elements are used in fusion reaction.
Applications of Radio Isotopes
1.
As
Radioactive tracers. The presence of a radioactive Isotope can be detected by
means of certain sensitive instruments like Geiger Muller counter. The
radioactive Isotope used to trace the path followed by it in a reaction, in a
plant or in human body is called radioactive tracer.
2.
In
agriculture. Radioactive phosphorus helps to study the at which phosphorus
compounds are absorbed by plants.
3.
In
medical diagnosis. (a) In order to know whether blood injected to a wounded patient
is reaching the wound or not, NaCl containing radio-Isotopes Na-24 is mixed
with blood and injected P-32 is used in the treatment of leukemia (b)
Radio-iodine is easily taken up by thyroid gland. Thus, it is employed to
diagnose and treat hyperthirodism.
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