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A side effect of using a moderator in a nuclear explosive is that as the chain reaction progresses, the moderator will be heated, thus losing its ability to cool the neutrons. Another effect of moderation is that the time between subsequent neutron generations is increased, slowing down the reaction.
Thermal reactors consist of the following: Neutron moderator to slow down the neutrons. In light water reactors and heavy water reactors it doubles as the nuclear reactor coolant. Nuclear fuel, which is a fissile material, usually uranium. Reactor vessel that is a pressure vessel containing the coolant and reactor core.
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.
Most reactor designs in existence are thermal reactors and typically use water as a neutron moderator (moderator means that it slows down the neutron to a thermal speed) and as a coolant. But in a fast breeder reactor, some other kind of coolant is used which will not moderate or slow the neutrons down much. This enables fast neutrons to ...
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.
Most fission reactors are thermal-neutron reactors that use a neutron moderator to slow down ("thermalize") the neutrons produced by nuclear fission. Moderation substantially increases the fission cross section for fissile nuclei such as uranium-235 or plutonium-239.
It has to do with the neutron count, the detectors showing the rate of multiplication of the neutrons in the reactor. It has to do with the positions of the control rods as they’re slowly ...
The BN-350 fast-neutron reactor at Aktau, Kazakhstan.It operated between 1973 and 1994. A fast-neutron reactor (FNR) or fast-spectrum reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons (carrying energies above 1 MeV, on average), as opposed to slow thermal neutrons used in thermal-neutron reactors.