| Advanced Test Reactor | |
|---|---|
 Advanced Test Reactor | |
  Idaho National Laboratory | |
| Operating Institution | Idaho National Laboratory |
| Location | Butte County, near Arco, Idaho, United States |
| Coordinates | 43°35′09″N 112°57′55″W / 43.585833°N 112.965278°W |
| Power | 250 MW |
| Construction and Upkeep | |
| Construction Began | 1967 |
| Technical Specifications | |
| Max Thermal Flux | 1015 s−1 cm−2 |
| Max Fast Flux | 5·1014 s−1 cm−2 |
| Cooling | Light water |
| Neutron Moderator | Light water |
| Neutron Reflector | Beryllium |
| Cladding Material | Stainless steel and concrete |
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 (3.7 m) across. The core is approximately 4 feet (1.2 m) tall by 4 feet (1.2 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.