Which of the following is used as a moderator in nuclear reactor?

Option B

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 first artificial nuclear reactor, the Chicago Pile-1, used graphite as a moderator. Graphite moderated reactors were involved in two of the best known nuclear disasters: an untested graphite annealing process contributed to the Windscale fire (but the graphite itself did not catch fire), while a graphite fire during the Chernobyl disaster contributed to the spread of radioactive material.

Types

There are several types of graphite-moderated nuclear reactors that have been used in commercial electricity generation:

• Gas-cooled reactors
  • Magnox
  • UNGG reactor
  • Advanced gas-cooled reactor (AGR)
• Water-cooled reactors
  • RBMK
  • EGP-6
• High-temperature gas-cooled reactors (past)
  • Dragon reactor
  • AVR
  • Peach Bottom Nuclear Generating Station, Unit 1
  • THTR-300
  • Fort St. Vrain Generating Station
• High temperature gas-cooled reactors (in development or construction)
  • Pebble-bed reactor
  • Prismatic fuel reactor
  • UHTREX Ultra-high-temperature reactor experiment