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Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
| MITR-II | |
|---|---|
 MIT Nuclear Reactor Laboratory in Cambridge, Massachusetts, with Tower Tech cooling tower in the foreground | |
  Location within Massachusetts | |
Operating institution | Massachusetts Institute of Technology |
| Location | Cambridge, Massachusetts |
| Coordinates | 42°21′37″N 71°05′47″W / 42.36028°N 71.09639°W |
| Type | tank[1] |
| Power | 6 MW[1][2] (thermal) |
| Construction and upkeep | |
Construction cost | US$3 million |
Construction began | 6 June 1956[1] |
| First criticality | 21 July 1958[1][3] |
Annual upkeep cost | US$2.5 million |
| Staff | 36[1] |
| Operators | 15[1] |
Refuel frequency | 3-4 months |
| Technical specifications | |
Max thermal flux | 6.0×1013 cm−2s−1[4] |
Max fast flux | 1.2×1014 cm−2s−1[4] |
| Fuel type | plate type[4] (27 (Three dedicated to in-core experiments)[5]x) |
| Cooling | light water[1] |
| light water[1] | |
| Control rods | |
Cladding material | aluminum alloy[6] |
The MIT Nuclear Research Reactor (MITR) serves the research purposes of the Massachusetts Institute of Technology. It is a tank-type 6 megawatt reactor[2] that is moderated and cooled by light water and uses heavy water as a reflector. It is the second largest university-based research reactor in the U.S. (after the University of Missouri Research Reactor Center) and has been in operation since 1958.[7] It is the fourth-oldest operating reactor in the country.[1]
The first iteration of the reactor, MITR-I, operated from 1958 to 1974. The reactor was then upgraded to a new design, MITR-II, which offers a higher neutron flux.[8]: 46
There are plans to convert the reactor to use low-enriched uranium instead of high-enriched uranium to mitigate the proliferation risk; as of 2016, this conversion was planned for 2027.[9]
The MITR-II design uses finned plate-type fuel arranged in a hexagonal pattern of rhomboid fuel assemblies.[6] Power is controlled by six manual boron-stainless steel blade-type control rods and one aluminum with cadmium control rod which can be placed on automatic control. Light water flows upwards through the core and a tank of heavy water surrounds the core. A wall of dense concrete that serves as shielding surrounds the tank of heavy water. The maximum coolant temperature is 50 °C (122 °F).[2] The light water and heavy water are cooled using forced circulation through heat exchangers to a secondary coolant system. The heat from the reactor is ultimately dissipated to the atmosphere via the secondary cooling system using two modular Tower Tech cooling towers – model TTXL-081950.[10]
The reactor uses highly enriched uranium 235 fuel, in the form of uranium-aluminum cermet with aluminum cladding.
Refueling takes place 3 to 4 times every year.[6] A single refueling involves rearranging the assemblies in the core or a combination of rearranging and replacement of old assemblies with new ones. This is more frequent than nuclear power plants and most research reactors. Power plants typically go 17 to 23 months between refueling outages, at which time they rearrange the entire core and replace 1⁄3 to 1⁄2 of the core. Many research reactors (particularly university reactors) go decades without refueling due to the high energy density of nuclear fuel and infrequent use at high power levels.
The MITR research program encompasses most aspects of neutron science and engineering including nuclear medicine. Some of these activities are:
The MITR is one of only six facilities in the world that was engaged in patient trials for the use of boron neutron capture therapy (BNCT) to treat both brain tumors and skin cancer. The MITR fission converter beam is the first to be designed for BNCT. The facility no longer conducts BNCT trials.
The reactor has been criticized by Miles Pomper of the James Martin Center for Nonproliferation Studies for having insufficiently unique uses relative to the risk of using highly enriched uranium.[9]
Today marks 63 years since the MITR-I first achieved criticality! The MITR-I was the first core configuration of the MIT Reactor (MITR) and was in operation from 1958 until 1973 (when the conversion to the MITR-II, the MITR's current core configuration, began).
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Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
The MIT Nuclear Research Reactor (MITR) serves the research purposes of the Massachusetts Institute of Technology. It is a tank-type 6 megawatt reactor that is moderated and cooled by light water and uses heavy water as a reflector. It is the second largest university-based research reactor in the U.S. (after the University of Missouri Research Reactor Center) and has been in operation since 1958. It is the fourth-oldest operating reactor in the country.
A nuclear reactor is a device used to sustain a controlled fission nuclear chain reaction. They are used for commercial electricity, marine propulsion, weapons production, and research. Fissile nuclei (primarily uranium-235 or plutonium-239) absorb single neutrons and split, releasing energy and multiple neutrons, which can induce further fission. Reactors stabilize this, regulating neutron absorbers and moderators in the core. Fuel efficiency is exceptionally high; low-enriched uranium is 120,000 times more energy-dense than coal. When the fissile nuclei splits, it generates heat; which is then passed to a coolant, usually water. In commercial reactors, this drives turbines and electrical generator shafts. Some reactors are used for district heating, and isotope production for medical and industrial use. After the discovery of fission in 1938, many countries launched military nuclear research programs. Early subcritical experiments probed neutronics. In 1942, the first artificial critical nuclear reactor, Chicago Pile-1, was built by the Metallurgical Laboratory. From 1944, for weapons production, the first large-scale reactors were operated at the Hanford Site. The pressurized water reactor design, used in about 70% of commercial reactors, was developed for US Navy submarine propulsion, beginning with S1W in 1953. In 1954, small-scale nuclear electricity production began with the Soviet Obninsk plant. The first commercial nuclear power station was Calder Hall at Sellafield, England, which started operation in 1956. Spent fuel can be reprocessed, potentially reducing nuclear waste and recovering reactor-usable fuel. This also poses a nuclear proliferation risk via production of plutonium for nuclear weapons. Reactor accidents have been caused by combinations of design and operator failure. The 1979 Three Mile Island accident, at INES Level 5, and the 1986 Chernobyl and 2011 Fukushima disasters, both at Level 7, had major effects on the nuclear industry and anti-nuclear movement. As of 2026, there are 441 commercial reactors, 228 research reactors, and over 200 marine propulsion reactors in operation globally. Commercial reactors provide 9% of the global electricity supply, compared to 30% from renewables, together comprising low-carbon electricity. Almost 90% of this comes from pressurized and boiling water reactors. Other designs include gas-cooled, fast-spectrum, breeder, heavy-water, molten-salt, and small modular, each of which improves safety, efficiency, cost, fuel type, enrichment, or burnup, and the now-obsolete Light water graphite reactor.
A pebble-bed reactor (PBR) is a type of nuclear reactor where the nuclear fuel is contained within a bed of pyrolytic graphite spheres (pebbles), with the graphite serving as a neutron moderator. Pebble-bed reactors are typically high temperature gas-cooled reactors (HTGRs), and are capable of being refueled during operation. The helium-cooled PBR design is considered a type of very-high-temperature reactor (VHTR), one of the six classes of nuclear reactors in the Generation IV initiative. The basic design features spherical fuel elements called pebbles. These tennis ball-sized elements (approx. 6.7 cm or 2.6 in in diameter) are made of pyrolytic graphite (which acts as the moderator), and contain thousands of 1mm sized fuel particles called tristructural-isotropic (TRISO) particles. These TRISO particles consist of a fissile material (such as 235U) surrounded by a ceramic coating of silicon carbide for structural integrity and fission product containment. Thousands of pebbles are amassed to create a reactor core. The core is cooled by a gas that does not react chemically with the fuel elements, such as helium, nitrogen, or carbon dioxide. Other coolants such as FLiBe (molten Li2(BeF4)) have been suggested. The pebble-bed design has passively safe features. Because the reactor is designed to handle high temperatures, it can cool by natural circulation and survive accident scenarios, which may raise the temperature of the reactor to 1,600 °C (2,910 °F). Their normal operating temperatures are higher than traditional nuclear power plants, allowing greater thermal efficiency (up to 50%). Additionally, the gases do not dissolve contaminants or absorb neutrons as water does, resulting in fewer radioactive fluids in the core. The concept was first suggested by Farrington Daniels in the 1940s, inspired by the innovative design of the Benghazi burner by British desert troops in WWII. Commercial development came in the 1960s via the West German AVR reactor designed by Rudolf Schulten. This system was plagued with problems and the technology was abandoned. The AVR design was licensed to South Africa as the PBMR and China as the HTR-10. The HTR-10 prototype was developed into China's HTR-PM demonstration plant, which connects two reactors to a single turbine producing 210 MWe, operating commercially since 2023. Other designs are under development by MIT, University of California at Berkeley, General Atomics (U.S.), Dutch company Romawa B.V., Adams Atomic Engines, Idaho National Laboratory, X-energy and Kairos Power.
Experimental Breeder Reactor I (EBR-I) is a decommissioned research reactor and U.S. National Historic Landmark located in the desert about 18 miles (29 km) southeast of Arco, Idaho. It was the world's first breeder reactor. At 1:50 p.m. on December 20, 1951, it became one of the world's first electricity-generating nuclear power plants when it produced sufficient electricity to illuminate four 200-watt light bulbs. EBR-I soon generated sufficient electricity to power its building and the town of Arco, and continued to be used for experimental research until it was decommissioned in 1964. The museum is open for visitors from Memorial Day weekend through Labor Day weekend.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →The Greenwood District.
