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This explains why most reactors fueled with 235 U need a moderator to sustain a chain reaction and why removing a moderator can shut down a reactor. The probability of further fission events is determined by the fission cross section, which is dependent upon the speed (energy) of the incident neutrons.
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.
A gas-cooled reactor (GCR) is a nuclear reactor that uses graphite as a neutron moderator and a gas (carbon dioxide or helium in extant designs) as coolant. [1] Although there are many other types of reactor cooled by gas, the terms GCR and to a lesser extent gas cooled reactor are particularly used to refer to this type of reactor.
A boiling water reactor (BWR) is a type of nuclear reactor used for the generation of electrical power. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR). BWR are thermal neutron reactors, where water is thus used both as a coolant and as a moderator, slowing down neutrons.
Thus, this reactor design is self-regulating, meltdown is impossible, and the design is inherently safe. From a safety point of view, the design leverages the technology used in the TRIGA reactor, which uses uranium zirconium hydride (UZrH) fuel and is the only reactor licensed by the U.S. Nuclear Regulatory Commission for unattended operation.
1943 Reactor diagram using boron control rods. Control rods are inserted into the core of a nuclear reactor and adjusted in order to control the rate of the nuclear chain reaction and, thereby, the thermal power output of the reactor, the rate of steam production, and the electrical power output of the power station.
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 ...
In nuclear engineering, the void coefficient (more properly called void coefficient of reactivity) is a number that can be used to estimate how much the reactivity of a nuclear reactor changes as voids (typically steam bubbles) form in the reactor moderator or coolant. Net reactivity in a reactor depends on several factors, one of which is the ...