TRIGA (Training, Research, Isotopes, General Atomics) is a class of small nuclear reactor designed and manufactured by General Atomics. The design team for TRIGA, which included Edward Teller, was led by the physicist Freeman Dyson.
TRIGA is a pool-type reactor that can be installed without a containment building, and is designed for use by scientific institutions and universities for purposes such as undergraduate and graduate education, private commercial research, non-destructive testing and isotope production.
The TRIGA reactor uses uranium zirconium hydride (UZrH) fuel, which has a large, prompt negative fuel temperature coefficient of reactivity, meaning that as the temperature of the core increases, the reactivity rapidly decreases. Because of this unique feature, it can be safely pulsed at a power of 22,000 megawatts, even though it is a low power reactor. TRIGA was originally designed to be fueled with highly enriched uranium, but in 1978 the US Department of Energy launched its Reduced Enrichment for Research Test Reactors program, which promoted reactor conversion to low-enriched uranium fuel.  
The TRIGA was developed to be a reactor that, in the words of Frederic de Hoffmann, head of General Atomics, was designed to be "safe even in the hands of a young student." Edward Teller headed a group of young nuclear physicists in San Diego in the summer of 1956 to design a reactor which could not, by its design, suffer from a meltdown. The design was largely the suggestion of Freeman Dyson. The prototype for the TRIGA nuclear reactor (TRIGA Mark I) was commissioned on 3 May 1958 in San Diego and operated until shut down in 1997. It has been designated as a nuclear historic landmark by the American Nuclear Society.
Mark II, Mark III and other variants of the TRIGA design have subsequently been produced, and a total of 35 TRIGA reactors have been installed at locations across the United States. A further 35 reactors have been installed in other countries. Many of these installations were prompted by US President Eisenhower's 1953 Atoms for Peace policy, which sought to extend access to nuclear physics to countries in the American sphere of influence. Consequently, TRIGA reactors can be found in Austria, Bangladesh, Brazil, Congo, Colombia, Finland, Germany, Taiwan, Japan, Italy, Indonesia, Malaysia, Mexico, Philippines, Puerto Rico, Romania, Slovenia, Thailand, Turkey, and Vietnam.
TRIGA International, a joint venture between General Atomics and CERCA — a subsidiary of AREVA of France — was established in 1996. Since then, TRIGA fuel assemblies have been manufactured at CERCA's plant in Romans-sur-Isère, France.
The TRIGA reactor constructed and installed at the University of Texas is estimated to have cost 5.8 million dollars
- TRIGA® Nuclear Reactors General Atomics
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- Teller (2001), p. 423
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- UxC webpage about the TRIGA Power System
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- Edward Teller (2001). Memoirs: A Twentieth-Century Journey in Science and Politics. Perseus Publishing.