A key feature of the Integral Fast Reactor (IFR) is its metallic alloy fuel. Metal fuel is crucial to the improved safety characteristics if the IFR, as well as to a new and much simpler fuel cycle technology.

Most reactors today use a ceramic fuel, generally uranium oxide. Compared to oxide, metal fuel has a conductivity about ten times higher (ceramics are generally thought of more as insulators, rather than conductors, of both electricity and heat). With high thermal conductivity, the heat generated by fission within the fuel slug is transferred to the coolant more effectively, resulting in a much lower temperature in the center of the fuel/. This is a major safety advantage. Abnormal reactor conditions involving loss of coolant flow to the reactor core can be accommodated with little or no damage of any kind, even if normal safety systems fail to function.

Metal fuel also allows a much simpler, more compact fuel cycle. Only a few pieces of equipment, located in a relatively small facility, are all that is needed to recycle the unused fuel. New metal rods are fabricated by simple injection casting. The finished rods are then inserted into new cladding jackets, and arranged into new fuel assemblies, which are then loaded into the reactor. The simplicity of the fuel cycle results in significant savings in cost.

Nuclear power generated in fast reactors holds the promise of greatly extending world energy resources. Metal fuel and liquid-metal reactor coolant are the best practical choices for managing uranium resources.

Metal fuel has been standard fuel in the EBR-II since it began operation in 1964. Through years of development and testing the excellent performance characteristics of metal fuel have become understood. A new alloy has been developed for the IFR which incorporates the latest improvements.

What constitutes good fuel performance? First, it should be capable of remaining in the reactor, producing power for a long time. IFR metal fuel can achieve a four-year residence in the reactor under full power conditions before it must be removed for recycling. Second, the fuel should be robust, capable of being subjected to a range of abnormal operating conditions without challenging system reliability and with minimum impact on continued reactor operation.

Since 1985 the new IFR metal fuel has been tested in the EBR-II reactor, with all results indicating excellent performance. These tests of the IFR fuel build upon 25 years of experience of constantly improving the metallic fuel used in EBR-II Hundreds of thousands of metallic fuel pins have been irradiated in EBR-II with excellent results. Currently, EBR-II is completely fueled with IFR assemblies in its role as the IFR prototype.

cc:AR