Light water graphite reactor

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. ^[1] 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. ^[2] China's nuclear weapons program also developed two military plutonium production LWGRs. ^[3] 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. ^[4] RBMKs use slightly enriched uranium (<2% ²³⁵U).

Selected examples of LWGRs

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	[1]
A-1	Soviet Union	10 June 1948	100	First Soviet plutonium production reactor; in Mayak	[2]
AM-1	Soviet Union	6 May 1954	30	First LWGR to generate electricity	[5]
AMB-100	Soviet Union	1 September 1963	286	SCWR test?	[6]
N Reactor	United States	8 December 1963	4000	Also Hanford Site, shutdown following Chernobyl disaster	[1]
AMB-200	Soviet Union	10 October 1967	530	SCWR test?	[7]
Chernobyl Reactor 4	Soviet Union	26 November 1983	3200	Reactor exploded in 1986, worst nuclear accident in history	[8]
Jiuquan reactor	China	1966	~250	China's first plutonium production reactor, military use	[3]
Guangyan reactor	China	1973	~250	Third Front facility, military use	[3]

See also

• RBMK
• Hanford Engineer Works
• Hanford Site
• Void coefficient

References

1. "Plutonium: The First 50 Years". FAS Project on Government Secrecy (1991-2021). 1994-09-30. Retrieved 2025-06-17.
2. Rhodes, Richard (1995). Dark Sun. New York, NY: Simon & Schuster. p. 276. ISBN   978-0-684-80400-2.
3. Zhang, Hui (2011-04-25). "China's HEU and Plutonium Production and Stocks" . Science & Global Security. 19 (1): 68–89. doi:10.1080/08929882.2011.566469. ISSN   0892-9882 . Retrieved 2025-06-17.
4. Panov, Aleksei; Trapeznikov, Alexander; Trapeznikova, Vera; Korzhavin, Alexander (2022). "Influence of operation of thermal and fast reactors of the Beloyarsk NPP on the radioecological situation in the cooling pond. Part 1: Surface water and bottom sediments". Nuclear Engineering and Technology. 54 (8). Elsevier BV: 3034–3042. doi: 10.1016/j.net.2022.03.004 . ISSN   1738-5733.
5. "APS 1 Obninsk". World Nuclear Association. 1951-01-01. Retrieved 2025-06-17.
6. "Beloyarsk 1". World Nuclear Association. 1958-06-01. Retrieved 2025-06-17.
7. "Beloyarsk 2". World Nuclear Association. 1962-01-01. Retrieved 2025-06-17.
8. "Chernobyl 4". World Nuclear Association. 1979-04-01. Retrieved 2025-06-17.