QUEST FOR FAIL-SAFE REACTORS
Light-water reactors require redundant and expensive emergency systems to prevent fuel melting if they lose coolant. During the 1980s, citizens worldwide expressed increased concerns about the reliability and safety of emergency cooling systems.
Laboratory researchers concluded that complex cooling systems would be unnecessary in high-temperature gas-cooled reactors. In 1988 John Cleveland of ORNL's Engineering Technology Division found merit in this conclusion when he participated in landmark safety tests at Germany's Arbeitsgemeinschaft Versuchs Reaktor (AVR). To observe gas-cooled reactor performance after sudden coolant loss, researchers deliberately stopped the coolant flow to the reactor. The reactor ran for five days without any coolant other than natural convection and conduction to its steam generator and through its walls. The test demonstrated the reliability of an inherently safe reactor.
This demonstration augured well for fundamentally safe and economical nuclear power, although a commercially viable unit remains years away. Oak Ridge and German scientists continued to collaborate on designing larger modular high-temperature gas-cooled reactors based on the inherently safe principles illustrated at the AVR.
In the United States, the Department of Energy has initiated studies of 350-megawatt (thermal) modular high-temperature gas-cooled reactors to produce electricity and tritium for defense purposes.
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