Q. Explain Principle, Purpose and Features of Nuclear Reactors

NUCLEAR REACTOR

DEFINITION:

Nuclear reactor is a device which is used to perform controlled fission reaction and extract the hidden energy from the nucleus.

PURPOSE:

Following are some main purpose of the nuclear reactor.
1- To convert controlled fission reaction to controlled chain reaction.
2- To produce large amount of energy.
3- To produce radioisotopes.

PRINCIPLE:

It is used on the principle of nuclear fission a process in which heavy nucleus breaks in to lighter nuclei with the emission of large amount of energy”.

FEATURES OF NUCLEAR REACTOR:

Following are the general features, which are common or almost nuclear reactor.

1. NUCLEAR FUEL:

A Material consisting of the fissionable isotopes is called reactor fuel that may be used in a reactor. For example (Uranium 92U235).

2. MODERATORS:

In the nuclear fission process at least one or more neutrons are produce per fission. To reduce the energy of neutron some suitable material is required which are known as moderators. The ordinary water (light water) an attractive moderator because of its supply at low cost. Heavy water is the best material. Other moderator is graphite beryllium and its oxides and organic compound.

3. COOLANTS:

Huge amount of heat is generated in reactor core as a result of fission take place in the
unclear fuel. To remove this large amount of heat, material are required which are called coolant. These materials are circulated though the core in order to absorb heat and transfer it to the outside of the core.

4. CONTROL MATERIAL:

In order to control nuclear fission in a reactor, suitable neutron absorbing material is required to be placed in the core region. The control material should be such that it does become radioactive by neutron capture. Cadmium and boron are good control materials.

5. SHIELDING:

During nuclear reactions neutrons and gamma rays emits out and becomes hazardous in the vicinity of the reactor, therefore proper shielding material is always required. A shielding material used for such protection is called the biological shielding because its purpose is to protect health. Generally a layer of concrete about 6 to 8 feet thickness has been found to absorb both neutrons and gamma rays. For rector operating at high power thermal shielding is required. A few cm of iron or steel very close to the core of the reactor provide the required thermal shield.