The Principles of a Fission Reactor

By: Anthony Long Hong Gong Tran LOLand BOBBY Moiler

What is a Fission Reactor?

The Principles of Fission Reactors are similar to that of an Atomic Reactor

Fission Reactors are more controlled

Produces fissions one neutron after another when the reactor reaches a certain power level, maintaining the reaction at a steady rate

Occurs as neutrons strikes a larger nucleus (U-235) whilst being absorbed by it

Large shielded structures utilising control of fission of uranium or plutonium for heat production used to generate electricity

Types of Fission Reactors

There are two types of Chain Reactions that occur within a Fission Reactor:

Controlled Chain Reactions

Uncontrolled Chain Reactions

Basic Reactor Elements

The Basic Elements of a Fission Reactor consists of the following:

Fuel Rods

Moderator

Control Rods

Coolant

Fuel Rods The types of fuel used in fission reaction must be burned in order to derive

nuclear energy.

Most materials are formed and composed into fuel rods mixed with structural moderation or neutron reflecting materials.

Contains heavy amount of fissile elements that are capable of nuclear fission reaction as they are capable of emitting neutrons that break apart when struck.

Sustains chain reactions that releases energy with controlled or uncontrolled rates.

Common fuel rods include Uranium-235 and Plutonium-239.

Moderator

The moderator is a medium that reduces the speed of fast moving neutrons from approx. 1 MeV to 0.5 eV through multiple collisions

Converts into thermal neutrons in order to sustain a nuclear chain reaction that involves uranium-235.

Water, Graphite, Helium, Beryllium and Sodium are commonly used moderators in a Fission Reactor.

Causes slow moving neutrons to become unstable which then splits into fissions.

Fills space between fuel rods in thermal reactors.

Neutrons of fissionable material captured by atoms will undergo fission

Control Rods

Used to control the rate of fission of uranium and plutonium.

Made of chemical elements capable of absorbing neutrons without fission including: Silver Indium Cadmium

Removed or inserted into central cores of a nuclear reactor in order to control the neutron flux which then further splits up uranium atoms.

Affects thermal power of the reactor, amount of steam produced and electricity generated.

Partially removed from the core to allow chain reactions.

Number of rods inserted and displacement distance determines the control of the reactivity of the reactor.

Coolant

Used to transfer heat from reactor core during fission.

Circulated around the core in order to absorb heat from neutrons and fission products.

Transfers heat to separate water or steam system, driving conventional turbine electricity generators.

Most coolants consist the use of water under high pressure