Gas cooled fast reactor (GFR). Source: Idaho National LaboratoryThe Gas-Cooled Fast Reactor (GFR) system is a nuclear reactor design which is currently in development. The GFR system features a fast-spectrum, helium-cooled reactor and closed fuel cycle. The main characteristics of the GFR are: a self-generating core (i.e., conversion ratio = 1) with a fast neutron spectrum, robust refractory fuel, high operating temperature, direct energy conversion with a gas turbine, and full actinide recycling (possibly with an integrated, on-site fuel reprocessing facility).

The GFR is a Generation IV reactor, a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030, with the exception of a version of the Very High Temperature Reactor.

The reference reactor design is a helium-cooled system operating with an outlet temperature of 850°C using a direct Brayton cycle gas turbine for high thermal efficiency. Several fuel forms are being considered for their potential to operate at very high temperatures and to ensure an excellent retention of fission products: composite ceramic fuel, advanced fuel particles, or ceramic clad elements of actinide compounds. Core configurations are being considered based on pin- or plate-based fuel assemblies or prismatic blocks, which allows for better coolant circulation than traditional fuel assemblies.

Several fuel forms are candidates that hold the potential to operate at very-high temperatures and to ensure an excellent retention of fission products: composite ceramic fuel, advanced fuel particles, or ceramic clad elements of actinide compounds. Core configurations may be based on prismatic blocks, pin- or plate-based assemblies.

The GFR is primarily envisioned for missions in electricity production and actinide management, although it may be able to support hydrogen production as well. The GFR design will utilize a direct-cycle, helium turbine for electricity and process heat for production of hydrogen. Through the combination of a fast-spectrum and full recycle of actinides, the GFR minimizes the production of long-lived radioactive waste. The GFR's fast-spectrum also makes it possible to use available fissile and fertile materials (including depleted uranium) considerably more efficiently than thermal-spectrum gas reactors with once-through fuel cycles.

Sources

• Generation IV International Forum, Generation IV Nuclear Energy Systems, Accessed 31 October 2008.
• Idaho National Laboratory, Generation IV Nuclear Energy Systems, Accessed 31 October 2008.
• Wikipedia Contributors, Gas-cooled fast reactor, Wikipedia The Free Encyclopedia, Accessed 31 October 2008.