Integral fast reactor

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The integral fast reactor (IFR, originally advanced liquid-metal reactor) is a design for a nuclear reactor using fast neutrons and no neutron moderator (a "fast" reactor). IFR would breed more fuel and is distinguished by a nuclear fuel cycle that uses reprocessing via electrorefining at the reactor site.

The U.S. Department of Energy began designing an IFR in 1984 and built a prototype, the Experimental Breeder Reactor II. On April 3, 1986, two tests demonstrated the safety of the IFR concept. These tests simulated accidents involving loss of coolant flow. Even with its normal shutdown devices disabled, the reactor shut itself down safely without overheating anywhere in the system. The IFR project was canceled by the US Congress in 1994, three years before completion.^[1]

The proposed Generation IV Sodium-Cooled Fast Reactor is its closest surviving fast breeder reactor design. Other countries have also designed and operated fast reactors.

S-PRISM (from SuperPRISM), also called PRISM (Power Reactor Innovative Small Module), is the name of a nuclear power plant design by GE Hitachi Nuclear Energy (GEH) based on the IFR.^[2] In 2022, GE Hitachi Nuclear Energy and TerraPower began exploring locating 5 Natrium sodium fast reactors based nuclear power plant design incorporating a PRISM reactor based on the IFR plus Terrapower's Traveling Wave design with a molten salt storage system in Kemmerer, Wyoming.^[3][4]