(nuclear power)
(fast reactors) average energy around 0.5 to 1.5 megaelectron volts
Researcher and author: Dr. ( Afshin Rashid)
Note: In fast reactors, no attempt is made to slow down the neutrons (no moderator is needed). The average energy of neutrons in this type of reactor is around 0.5 to 1.5 megaelectron volts.
For this reason, the fuel rods must be inside the moderator for the reaction to take place. In fact, the moderator should not absorb the kinetic energy of the neutron in addition to it. Generally, low mass number materials are good retarders. Nuclear power units that work with light water are usually operated with 2 to 5 percent of uranium 235. In a reactor, usually 3 resistors will be used simultaneously to equalize the neutron flux and produce uniform heat and energy. So that during refueling during the operation of the reactor, the fuel with more richness is placed on the outer side of the fuel assemblies of the heart of the reactor, and after about 12 to 18 months, the next refueling is done and by placing new uranium, the spent assembly is removed from The center of the reactor core will be removed and the new fuel will move from the outer environment to the middle and the fuel with medium richness will occupy the place of the fuel with less richness. During each thermal fission, 2.43 neutrons will be created, and if one of these neutrons is used for the next fission, 1.43 neutrons remain, which must be removed from the environment in nuclear reactors.
But the important point is that the neutrons produced as a result of nuclear fission have different energies and their average energy is Mev 2 (2 mega electron volts [each electron volt is equivalent to 1.6 x 10-19 joules of energy) ]) the situation is that uranium 235 reacts with neutrons whose energy is much lower than this value, i.e. about 25,000 electron volts and their speed is 2,200 meters per second, and since the main fuel of nuclear reactors is It is the type of uranium, so the energy of neutrons must decrease. Yellow cake is generally used to prepare nuclear reactor fuel, in fact, it is this material that is converted into UO2 after some processes and used in fuel rods. This material can also be used for enrichment to Uranium hexafluoride or UF6 gas is converted, because in this case, the density of uranium 235 isotopes can be increased in it.
The main fuel of nuclear power reactors is uranium, which is used in different reactors in different combinations. In these reactors, enriched uranium is used as the starting material for nuclear fission. Enriched uranium is uranium whose isotope 238 has been artificially reduced. Uranium dioxide (UO2) is used. In homogeneous or homogeneous reactors (fuel and moderator form a single unit) always and without exception, uranium enriched in solution (UO2SO4) is used. These fuels are often used in the form of rods, belts and pellets.
Conclusion :
In fast reactors, no attempt is made to slow down the neutrons (no moderators are needed). The average energy of neutrons in this type of reactor is around 0.5 to 1.5 megaelectron volts.
Researcher and author: Dr. ( Afshin Rashid)
Specialized doctorate in nano-microelectronics