Question

What is the purpose of using the graphite moderator

Answer 1

Hope it will help you

Answer 2

A graphite reactor is a nuclear reactor that uses carbon as a neutron moderator, which allows un-enriched uranium to be used as nuclear fuel. The very first artificial nuclear reactor, the Chicago Pile-1, used graphite as a moderator.

Advantages
One benefit of graphite is that even at the high purity that is necessary for graphite to perform well, it is available at a fairly low price. In addition, graphite is a good moderator as it is thermally stable and conducts heat well.

Function
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235 or a similar fissile nuclide.