Neutron Sources
Ilya Obodovskiy, in Radiation, 2019
19.1.1 Research Reactors
Nuclear reactors are powerful neutron sources. A large number of reactors are used to generate energy, but there is a whole group of special research nuclear reactors that are used as neutron sources, by which neutron beams are emitted. The operation of these reactors can serve as a means of teaching the basics of nuclear physics and the specifics of reactor control. Such reactors are necessary for all kinds of technical experiments. The neutrons produced by a research reactor are used for neutron scattering, nondestructive testing, analysis and testing of materials, production of radionuclides, research, and public education.
Database of nuclear research reactors [1] shows that there were 817 of both research and training reactors in operation worldwide; 225 of them are still in operation (up to summer 2018). 56 research reactors operate in North America (United States and Canada) and 28 operate in Western Europe. In Eastern Europe, currently 72 reactors are active, 53 of them are in Russia. The neutron productivity of these reactors can be shown by two examples.
The Training and Research Reactor IRT-2000 is operating in Moscow, at the National Research Nuclear University "MEPhI." The reactor capacity is 2.5 MW. The maximum thermal neutron flux density is 4.8·1013 cm−2/s; fast neutrons are 4.3·1013 cm−2/s. The reactor has 10 horizontal and 20 vertical channels. It works 24 h a day, 6 days a week, and 42 weeks a year. About 600 students are involved in the training sessions at the reactor. The reactor started to function in critical mode in May, 1967.
The HFIR nuclear reactor in the Oak Ridge National Laboratory has a capacity of 85 MW and produces neutron fluxes of the order of 1015 cm−2/s. The reactor was commissioned in August, 1965.
Neutrons are the power instruments of the nuclear research and the single type of radiation that can induce radioactivity. Hence, the neutron sources deserve separate consideration. In this chapter, the different types of nuclear reactors, namely, research reactors, pulse reactors, power reactors, reactors of nuclear icebreakers, aircraft carriers, and submarines, are described. For all these reactors the neutron flux density is pointed out. Special attention is paid to the so-called natural nuclear reactor in Oklo. Besides, nuclear generators, which are built on the basis of accelerators, and radionuclide neutron sources are described.
thermal neutrons: plural form of thermal neutron
neutron: Neutrons are heavy nuclear particles with no electrical charge and approximately the same mass as protons With protons, they are the principal components of atomic nuclei They are composed of two "down" quarks and one "up" quark
neutron: an elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus
neutron: One of the three basic atomic particles The neutron weighs about the same as the proton and, as its name implies, has no charge Neutrons make effective atomic projectiles See also: Electron, Proton
neutron: An elementary particle which has approximately the same mass as a proton but no electrical charge and is a constituent of all nuclei having a mass number greater than one
neutron: A particle that appears in the nucleus of all atoms except hydrogen Neutrons are one of three basic particles that make up the atom Neutrons have no electrical charge
neutron: An unchanged elementary particle that has a mass nearly equal to that of the PROTON and is present in all known atomic nuclei except the HYDROGEN nucleus
neutron: A particle that may be emitted from the nucleus of atoms and carries no electrical charge
neutron: A common neutral particle equal in size to a proton, often found in the nucleus of atoms Composed of two down quarks and one up quark
neutron: A subatomic particle with a mass of about 1 amu and no charge
neutron: A particle that is found in the nucleus of an atom, has a mass approximately equal to that of a proton, and has no electric charge
neutron: A neutral elementary particle that occurs in the nuclei of elements (except ordinary hydrogen) Free neutrons decay into a proton, an electron and an anti-neutrino A neutron is about 1,838 times heavier than an electron
neutron: Atomic sub-particle found in the nucleus of an atom This particle is similar in mass to a proton but does not have an electromagnetic charge
neutron: {i} elementary particle in atomic nuclei which has no electrical charge (Physics)
neutron: Neutrons, which have no electrical charge, and protons, which have positive charge, are the particles which make up the nuclei of atoms
neutron: One of the basic particles which make up an atom A neutron and a proton have about the same weight, but the neutron has no electrical charge