Types of Atomic tests: -
Atmospheric, Underwater, Underground.
Science behind Atomic Weapons Testing – Atomic weapons are weapons of
mass destruction based on two types of reactions – nuclear fission and
fusion reaction.
Nuclear Fission based atomic weapon
In nuclear fission reaction a critical
mass is created by combining two sub-critical mass capable to support a
chain reaction. There are two ways in which a critical mass can be
created. In the gun-type method, sub-critical masses of fissionable
material are placed a little apart from one another in a device similar
to a gun barrel. A powerful conventional explosive is packed behind one
piece, the fuse is triggered and the explosive goes off propelling one
of the sub-critical masses into the other at high-speed. A combined mass
become super-critical and initiates the self-sustaining chain reaction.
For example, the bomb dropped on Hiroshima used the gun-type method.
The other method is the implosion method. A spherical sub-critical
mass is surrounded by conventional explosives. The explosive goes off on
detonation, compressing the sub-critical mass into high density
supercritical mass resulting into a high density supercritical mass
resulting into chain reaction. For example the atom bomb dropped on
Nagasaki was of the implosion type. |
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| Pictures of Atomic Explosions | |
Nuclear Fusion based atomic weapons
In fusion weapons, the power comes from
the fusion or combination of lightweight nuclei under intense heat, the
reason why they are also called thermonuclear weapons. The nuclei of the
isotopes of hydrogen, deuterium and tritium, are fused. The product of
fusion weight less than the combined original nuclei and the lost matter
turns into energy. The very high temperature required for fusion is
achieved by means of fusion explosion. The explosion of the fission
device also release neutrons which strike against a compound of
lithium-6 deuteride inside the weapon. On being struck by neutrons the
compound gives rise to helium and tritium. Now pairs of one tritium
nuclei, pair of deuterium nuclei and pair of one tritium-one deuterium
nuclei combine to form helium nuclei. As some amount of matter from the
deuterium and tritium nuclei is converted into a large amount of energy a
thermonuclear explosion takes place. The explosive power of the weapon
is increased by surrounding lithium-6 deuteride with U-238 because the
thermonuclear explosion fissions the uranium-238. The device is also
known as hydrogen bomb as isotopes of hydrogen are responsible for its
explosive power.
Nuclear Reactor Technology
A nuclear reactor is a device in which
nuclear chain reactions are initiated, controlled, and sustained at a
steady rate. The most significant use of nuclear reactors is as an
energy source for the generation of electrical power and for the power
of propulsion in nuclear submarines.
The physics of operating a nuclear
reactor is explained by Nuclear reactor physics. The natural uranium is
the fuel used in the reactor and consists of two types of isotopes – U
238 and U-235 in the ratio of 139:1. The U-235 isotope undergoes fission
and release energy. When a slow neutron struck U-235 atom, it splits
into two or more fragments and tw or three fast neutrons. Tremendous
amount of energy is produced in this process. The fast neutrons re made
to slow down before they strike other U-235 atoms, thus releasing chain
reaction is attained in due course of time.
Classifications
Nuclear Reactor are classified by
several methods such as based on nuclear reaction, moderator material,
coolant, phase of fuel, use etc. A brief outline of these classification
schemes is provided below:
Nuclear fission – Most reactors, and all
commercial ones, are based on nuclear fission. They generally use
uranium and its product plutonium as nuclear fuel cycle is also
possible. Fission reactors can be divided roughly into two classes,
depending on the energy of the neutrons that sustain the fission chain
reaction. Thermal reactors use slowed or thermal neutrons and fast
neutron reactors use fast neutrons to cause fission in their fuel. they
do not have a neutron moderator and use less moderating coolants.
Light water moderated reactors (LWRs) –
Light water reactors use ordinary water to moderate and cool the
reactors. At operating temperature, the density of water drops because
of increase in its temperature, and fewer neutrons passing through it
are slowed enough to trigger further reactions. Due to the extra
thermalization, these types can use natural uranium/unreached fuel.
| Name of Nuclear Explosions (Atomic Explosions) | Country | Yield (Kt) | Year |
| Trinity | USA | 19 | 1945 |
| Little Boy | USA | 15 | 1945 |
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