Gas Cooled Reactors

In the Gas Cooled Reactor (GCR), the moderator is graphite. Carbon dioxide gas is() circulate through the core at a pressure of ~1.6 MP_aor 230 pounds per square inch to remove the heat from the fuel elements. The fuel consists of natural uranium metal with a cladding material which is an alloy of magnesium known as Magnox (thus the name for the reactor type).

The newer Advanced Gas Cooled (AGR) Reactors use a slightly enriched uranium dioxide clad with stainless steel. Carbon dioxide is the coolant gas used.

Two key advantages of this design are:

higher operating temperature with a higher thermal efficiency
not susceptible to accidents of the type possible with water cooled/moderated reactors.

The simplified sketch below shows the typical Gas Cooled Reactor or Advanced Gas Reactor cycle.

Courtesy Scottish Nuclear

Scottish Nuclear and BNFL have sites devoted to gas cooled reactors. In the United Kingdom, electrical suppliers are British Energy and Magnox Electric. Scottish Nuclear (SNL) and Nuclear Electric (NEL) are subsidiaries of British Energy. NEL generates most of the nuclear electricity in the UK from Advanced Gas Cooled reactors and the only UK PWR (Sizewell B). Magnox Electric is still owned by the government and now runs all the Magnox reactors in Britain not owned by BNFL. The Hinckley Point site has both types of reactors - the A units are of the older GCR design; the B units are of the AGR design.

The BNFL Commercial Center Technologies and Expertise page provides detailed information on nuclear fuels, uranium enrichment, and reprocessing. Their Company Profile page provides information about their operational sites including the Chapelcross and Calder Hall Magnox reactors.


Capenhurst - Courtesy BNFL	Hunterston B - Courtesy Scottish Nuclear

Scottish Nuclear has provided a very nice tour of the Advanced Gas Cooled Reactor Torness facility. Additional information about the - Hunterston and Torness - facilities includes nuclear fundamentals, tour information, contact, rating, and startup dates, and the Windscale event.

In the United States, a commercial High Temperature Gas Cooled Reactor produced by General Atomic was operated by Public Service of Colorado at Ft. St. Vrain for many years. However, the plant was shutdown because the plant did not meet the design output expectations of the utility. The Nuclear High Temperature Gas-Cooled Reactor (HTGR) design still holds promise as shown in a paper by Yi-Chie Chuan of University of California Berkeley.