GCR - Gas-Cooled Reactor

The term gas-cooled reactor (GCR) can be used ambiguously. HTGRs, for example, are a subset of GCRs that operate at higher temperatures. As used here, GCRs include "Magnox" reactors designed and built in the United Kingdom since the 1950s and the derivative, advanced gas-cooled reactor (AGR), also operated in the United Kingdom. Similar reactors had been built and operated in France, Sweden, and Japan but have since closed. No GCR design, as defined here, has operated commercially in the United States. Commercial GCRs11 in the United Kingdom have operated longer than any category of commercial reactors anywhere else in the world. Like the PHWRs, the original GCR designs use natural uranium fuels, though newer designs (AGRs) use slightly enriched fuels and are not confined to uranium fuels.