Light water graphite reactor
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The light water graphite reactor (LWGR) is a design of nuclear reactor that uses purified graphite as a neutron moderator and light water (H2O) 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 (GCRs) moderated by graphite, while those used by Israel, India, and Pakistan were believed to be heavy water reactors (HWRs).[citation needed]
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 (<2% 235U).
| Reactor | Country | Criticality date | Initial power (MWth) | Notes | Refs. |
|---|---|---|---|---|---|
| B Reactor | United States | 26 September 1944 | 250 | First LWGR, twin D and F reactors built under Manhattan Project | |
| A-1 | Soviet Union | 10 June 1948 | 100 | First Soviet plutonium production reactor; in Mayak | |
| AM-1 | Soviet Union | 6 May 1954 | 30 | First LWGR to generate electricity | |
| AMB-100 | Soviet Union | 1 September 1963 | 286 | SCWR test? | |
| N Reactor | United States | 8 December 1963 | 4000 | Also Hanford Site, shutdown following Chernobyl disaster | |
| AMB-200 | Soviet Union | 10 October 1967 | 530 | SCWR test? | |
| Chernobyl Reactor 4 | Soviet Union | 26 November 1983 | 3200 | Reactor exploded in 1986, worst nuclear accident in history | |
| Jiuquan reactor | China | 1966 | ~250 | China's first plutonium production reactor, military use | |
| Guangyan reactor | China | 1973 | ~250 | Third Front facility, military use |