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In a thermal-neutron reactor, the nucleus of a heavy fuel element such as uranium absorbs a slow-moving free neutron, becomes unstable, and then splits into two smaller atoms (fission products). The fission process for 235 U nuclei yields two fission products, two to three fast-moving free neutrons, plus an amount of energy primarily manifested ...
The Research Neutron Source Heinz Maier-Leibnitz (Forschungsreaktor München II or FRM II) (German: Forschungs-Neutronenquelle Heinz Maier-Leibnitz) is a leading German research reactor and neutron source, named in honor of the physicist Heinz Maier-Leibnitz who had conducted a highly successful research program at its predecessor, the FRM I [].
A thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons.. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and structure, which is much lower energy than the fast neutrons initially produced by fission.)
Diagram of a nuclear reactor using graphite as a moderator "Graphite reactor" directs here. For the graphite reactor at Oak Ridge National Laboratory, see X-10 Graphite Reactor. A graphite-moderated reactor is a nuclear reactor that uses carbon as a neutron moderator, which allows natural uranium to be used as nuclear fuel.
One type uses solid nuclear graphite for the neutron moderator and ordinary water for the coolant. See the Soviet-made RBMK nuclear-power reactor. This was the type of reactor involved in the Chernobyl disaster. In the Advanced Gas-cooled Reactor, a British design, the core is made of a graphite neutron moderator where the fuel assemblies are ...
Neutron guide The instrument is located on the TG1 thermal neutron guide of the OPAL reactor. The distance from the reactor is 58 metres (190 ft). The position is the second on the guide after the WOMBAT instrument. The size of the guide is 300 millimetres (12 in) high by 50 millimetres (2.0 in) wide, and it is plated with supermirror coatings.
The mere fact that an assembly is supercritical does not guarantee that it contains any free neutrons at all. At least one neutron is required to "strike" a chain reaction, and if the spontaneous fission rate is sufficiently low it may take a long time (in 235 U reactors, as long as many minutes) before a chance neutron encounter starts a chain reaction even if the reactor is supercritical.
According to the patent application [5] the reactor design has some notable characteristics, that sets it apart from other reactor designs. It uses uranium hydride (UH 3) "low-enriched" to 5% uranium-235—the remainder is uranium-238—as the nuclear fuel, rather than the usual metallic uranium or uranium dioxide that composes the fuel rods of contemporary light-water reactors.