Light water graphite reactor
The light water graphite reactor '' is a design of nuclear reactor that uses purified graphite as a neutron moderator and light water as a liquid coolant. Due to the superior moderating properties of graphite, natural uranium can be used as a fuel, avoiding enrichment.
The design was developed during the Manhattan Project, in a horizontal layout, first used in the 1944 B Reactor, also the world's first large-scale reactor. The Project's Hanford Site constructed nine LWGRs in total for plutonium production, used throughout the Cold War. The Soviet Union subsequently developed a vertical design for use in military plutonium production reactors, constructed at Mayak, the Siberian [Chemical Combine] in Seversk, and the Mining and Chemical Combine in Zhelenogorsk. China's nuclear weapons program also developed two military plutonium production LWGRs. Reactors used for plutonium production in the nuclear weapons programs of the United Kingdom, France, and North Korea used gas-cooled reactors moderated by graphite, while those used by Israel, India, and Pakistan were believed to be heavy water reactors.
The Soviet Union also developed civilian power prototypes eventually into the RBMK design, the only widespread use of LWGRs for commercial nuclear power plants. RBMKs use slightly enriched uranium.
| Reactor | Country | Criticality date | Initial power | Notes | Refs. |
| B Reactor |  United States |