NUCLEAR POWER PLANT

RADIOACTIVITY

• Nucleus is stable forces acting on electron and proton are equal.

• Nucleus is unstable Un equal forces.

• Becomes stable by emitting radiation (particles or EM Waves).

• This phenomenon is called radioactivity.

• Alpha

• Beta

• gamma

RADIOACTIVITY

• Alpha particle nucleus of a Helium atom, 24He.

• Beta particles negatively charged high speed electrons emitted by

the nucleus. They have no mass but posses a charge of -1. They are

denoted by -10e.

• Gamma rays are high energy photons travelling with the velocity of

light. They have no mass or charge. They are denoted by 00y.

NUCLEAR FISSION

• Splitting of nucleus into lighter nuclei by colliding it with a neutron

(projectile).

• Must have an energy equivalent to nuclear binding energy to split the

nucleus.

• Nuclear fission produces heat and electromagnetic radiation.

• E = mc2.

NUCLEAR FISSION

• Fission produces additional neutrons (projectiles) which can then be

captured by other atoms to continue the reaction (chain reaction)

• The reaction can get out of control and an explosion can occur.

• To prevent this control rods that absorb the extra neutrons are used.

• Uranium-235 is the most commonly used fuel for fission.

• The materials U-235, U-233 and Pu-239 are called fissionable

materials.

• The only fissionable nuclear fuel occurring in nature is uranium

• 99.3 % is U-238

• 0.7% is U-235

• U-234 is only a trace.

• Out of these isotopes only U-235 will fission in a chain reaction.

NUCLEAR FISSION

• The materials U-235, U-233 and Pu-239 are called fissionable

materials.

• The only fissionable nuclear fuel occurring in nature is uranium

• 99.3 % is U-238

• 0.7% is U-235

• U-234 is only a trace.

• Out of these isotopes only U-235 will fission in a chain reaction.

NUCLEAR FISSION

• REACTOR CORE

• Contains nuclear fuel – U 235

• MODERATOR

• To reduce the speed of the neutrons (projectile) so as to maintain reaction

• Hydrogen, Deuterium, Helium, Lithium, Berylium, Boron, Carbon, Nitrogen,

Oxygen

• CONTROL RODS

• Absorb neutrons to control the reaction

• boron-10, cadmium, graphite.

• COOLANT

• Transfer heat to water

• GAS - Air, helium, hydrogen and CO2

• LIQUID - light and heavy water

• METAL - molten sodium and lithium

• REFLECTOR

• Confines the neutrons within the reactor.

• SHIELDING

• Lead or thick concrete.

• Protection from alpha, beta and gamma rays

Boiling Water Reactor (BWR )

Ordinary water is used as coolant and moderator

Pressurized Water Reactor (PWR )Water under pressure is used as coolant and moderator

Heavy Water Cooled And Moderated (CANDU Type) Reactor

CANDU Canadian Deuteriurn Uranium.

Heavy water is moderator and coolant

Fast-Breeder Reactor.

• Uranium or plutonium is surrounded by a blanket of U-238 or Th-232. • U-238 or Th-232 absorbs neutrons produced by the fissioning of U-235 and produces fissile material Pu-239 or U-233• Thus secondary fuels (U-233 and Pu-239) results in reduction of fuel cost. • Two heat exchangers are used to prevent the possibility of a sodium-water reaction with the radio-active sodium.

GAS COOLED REACTOR

• Uses CO2 and Helium as coolant.

• Graphite as the moderator.

• A large quantity of gas is required, due to poor heat transfer qualities.