The AFCI’s fast reactor (pdf) research program focuses on improving the designs of the experimental test reactors that have operated successfully in the past. The basic design and operation of fast reactors has been demonstrated by numerous reactors that have operated for many years. The first nuclear reactor that produced electricity was, in fact, a sodium cooled fast reactor that operated more than fifty years ago. These early reactors were small experimental reactors that were designed to test certain aspects of what were then new and innovative technologies.

What makes a fast reactor (pdf) different from a light water reactor is neutron speed. In a fast reactor, the neutrons produced by fission are not slowed down (moderated) significantly before they cause more fission reactions. Thus, fast reactors must minimize use of materials, such as water, which slow neutrons. The higher energy neutrons can fission all types of uranium and transuranic elements, rather than just the “fissile” isotopes split in thermal reactors. This allows the fast reactor to transmute (consume) the transuranics efficiently and safely. Thus, fast reactors can extract energy from all types of uranium and all isotopes of the transuranic elements. AFCI focuses on a type of fast reactor, the advanced burner reactor, which is designed to maximize consumption of transuranic elements. “Burner” in this instance doesn’t mean incineration or combustion, but rather a conversion of transuranics into shorter-lived isotopes.

Work continues to make fast reactors smaller with greater electrical output, more reliable, and more economical in order to make them attractive to the commercial industry. Research and development is being conducted in three areas: advanced materials, innovative components and systems, and computer models and simulation by the DOE national laboratories, universities, and private industry. Similar research and development is also being performed in other countries as well.

Artist's representation of an advanced fast reactor