Advanced Test Reactor

Idaho National Laboratory research neutron source

The Advanced Test Reactor (ATR) is a research reactor at the Idaho National Laboratory, located east of Arco, Idaho. This reactor was designed and is used to test nuclear fuels and materials to be used in power plants, naval propulsion, research and advanced reactors. It can operate at a maximum thermal power of 250 MW and has a "Four Leaf Clover" core design (similar to the Camunian rose) that allows for a variety of testing locations. The unique design allows for different neutron flux (number of neutrons impacting one square centimeter every second) conditions in various locations. Six of the test locations allow an experiment to be isolated from the primary cooling system, providing its own environment for temperature, pressure, flow and chemistry, replicating the physical environment while accelerating the nuclear conditions. The ATR is a pressurized light water reactor (LWR), using water as both coolant and moderator. The core is surrounded by a beryllium neutron reflector to concentrate neutrons on experiments, and houses multiple experiment positions as well. It operates at low temperature and pressure 71 °C (160 °F) and up to 2.69 MPa water pressure. The ATR reactor vessel is solid stainless steel, 35 feet (11 m) tall by 12 feet (4 m) across. The core is approximately 4 feet (1 m) tall by 4 feet (1 m) across. In addition to its role in nuclear fuels and materials irradiation, the ATR is the United States' only domestic source of high specific activity (HSA) cobalt 60 (60Co) for medical applications. HSA 60Co is used primarily in gamma knife treatment of brain cancer. Other medical and industrial isotopes have also been produced, and could be again, including plutonium 238 (238Pu), which is useful for powering spacecraft.

Since 1951, fifty two reactors have been built on the grounds of what was originally the Atomic Energy Commission's National Reactor Testing Station, currently the location of the U. S. Department of Energy's Idaho National Laboratory (INL). Constructed in 1967, the ATR is the second oldest of three reactors still in operation at the site. Its primary function is to intensely bombard samples of materials and fuels with neutrons to replicate long term exposure to high levels of radiation, as would be present after years in a commercial nuclear reactor. The ATR is one of only four test reactors in the world with this capability. The reactor also produces rare isotopes for use in medicine and industry.