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Research reactors are
nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...
-based
nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...
s that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritime propulsion.


Purpose

The
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the atomic nucleus, nuclei of atoms. Since protons and ...
s produced by a research reactor are used for neutron scattering, non-destructive testing, analysis and testing of materials, production of
radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
s, research and public outreach and education. Research reactors that produce radioisotopes for medical or industrial use are sometimes called isotope reactors. Reactors that are optimised for beamline experiments nowadays compete with spallation sources.


Technical aspects

Research reactors are simpler than power reactors and operate at lower temperatures. They need far less fuel, and far less
fission products Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...
build up as the fuel is used. On the other hand, their fuel requires more
highly enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U ...
, typically up to 20% U-235, although some use 93% U-235; while 20% enrichment is not generally considered usable in nuclear weapons, 93% is commonly referred to as " weapons-grade". They also have a very high power density in the core, which requires special design features. Like power reactors, the core needs cooling, typically natural or forced
convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...
with water, and a moderator is required to slow the neutron velocities and enhance fission. As neutron production is their main function, most research reactors benefit from reflectors to reduce neutron loss from the core.


Conversion to low enriched uranium

The
International Atomic Energy Agency The International Atomic Energy Agency (IAEA) is an intergovernmental organization that seeks to promote the peaceful use of nuclear energy and to inhibit its use for any military purpose, including nuclear weapons. It was established in 195 ...
and the U.S. Department of Energy initiated a program in 1978 to develop the means to convert research reactors from using highly enriched uranium (HEU) to the use of
low enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (2 ...
(LEU), in support of its nonproliferation policy. By that time, the U.S. had supplied research reactors and highly enriched uranium to 41 countries as part of its Atoms for Peace program. In 2004, the U.S. Department of Energy extended its Foreign Research Reactor Spent Nuclear Fuel Acceptance program until 2019. As of 2016, a
National Academies of Sciences, Engineering, and Medicine The National Academies of Sciences, Engineering, and Medicine (also known as NASEM or the National Academies) are the collective scientific national academy of the United States. The name is used interchangeably in two senses: (1) as an umbrell ...
report concluded converting all research reactors to LEU cannot be completed until 2035 at the earliest. In part this is because the development of reliable LEU fuel for high
neutron flux The neutron flux, φ, is a scalar quantity used in nuclear physics and nuclear reactor physics. It is the total length travelled by all free neutrons per unit time and volume. Equivalently, it can be defined as the number of neutrons travellin ...
research reactors, that does not fail through swelling, has been slower than expected. , 72 HEU research reactors remain.


Designers and constructors

While in the 1950s, 1960s and 1970s there were a number of companies that specialized in the design and construction of research reactors, the activity of this market cooled down afterwards, and many companies withdrew. The market has consolidated today into a few companies that concentrate the key projects on a worldwide basis. The most recent international tender (1999) for a research reactor was that organized by the Australian Nuclear Science and Technology Organisation for the design, construction and commissioning of the Open-pool Australian lightwater reactor (OPAL). Four companies were prequalified:
Atomic Energy of Canada Limited Atomic Energy of Canada Limited (AECL) is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory. AECL developed the CANDU reactor technology starting in the 1950s, and in October 2011 licensed this ...
(AECL),
INVAP INVAP S.E. is an Argentine company that provides design, integration, construction and delivery of equipment, plants and devices. The company operates in North America, Europe, Asia Pacific, Latin America, the Middle East and Africa, and delive ...
,
Siemens Siemens AG ( ) is a German multinational conglomerate corporation and the largest industrial manufacturing company in Europe headquartered in Munich with branch offices abroad. The principal divisions of the corporation are ''Industry'', ''E ...
and Technicatom. The project was awarded to INVAP that built the reactor. In recent years, AECL withdrew from this market, and Siemens and Technicatom activities were merged into
Areva Areva S.A. is a French multinational group specializing in nuclear power headquartered in Courbevoie, France. Before its 2016 corporate restructuring, Areva was majority-owned by the French state through the French Alternative Energies and Atom ...
.


Classes of research reactors

*
Aqueous homogeneous reactor Aqueous homogeneous reactors (AHR) are a type of nuclear reactor in which soluble nuclear salts (usually uranium sulfate or uranium nitrate) are dissolved in water. The fuel is mixed with the coolant and the moderator, thus the name "homogeneo ...
*
Argonaut class reactor The Argonaut class reactor is a design of small nuclear research reactor. Many have been built throughout the world, over a wide range of power levels. Its functions are to teach nuclear reactor theory, nuclear physics and for use in engineering la ...
* DIDO class, six high-flux reactors worldwide * TRIGA, a highly successful class with >50 installations worldwide * SLOWPOKE reactor class, developed by AECL, Canada * Miniature neutron source reactor, based on the SLOWPOKE design, developed by AECL, currently exported by China * Aerojet General Nucleonics, 201 Models. Developed by Aerojet General in the United States. 3 current reactors in operation at Idaho State University, The University of New Mexico, and Texas A&M University.


Research centers

A complete list can be found at the List of nuclear research reactors. Research centers that operate a reactor: Decommissioned research reactors:


References


WNA Information Paper # 61: Research ReactorsNuclear Nonproliferation: DOE Needs to Take Action to Further Reduce the Use of Weapons-Usable Uranium in Civilian Research Reactors
GAO, July 2004, GAO-04-807


External links


IAEA searchable list of Nuclear Research Reactors in the worldThe National Organization of Test, Research, and Training Reactors, Inc.NMI3 - EU-FP7 Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy
{{Authority control Nuclear reactors Nuclear research reactors Neutron Neutron sources