The words "nuclear reactor" are now familiar to everyone, in fact, becoming a symbol of an entire era. Despite the potential danger of using such devices, in light of the depletion of global oil reserves, nuclear fuel reactors are very promising.
A nuclear reactor is an engineering device in which a controlled fission reaction of fissile radioactive material occurs , accompanied by the release of energy. The main purpose is the generation of electric current (nuclear power plants - nuclear power plants), as well as the production of heavy fissile elements of the periodic table (conversion). The first nuclear reactor was assembled and put into operation in 1942 in America under the control of the outstanding physicist of his time - Enrique Fermi. Three years later, Canada launched its reactor, and in 1946, Russia.
We note one important point: many people unfamiliar with this topic often believe that a nuclear reactor produces electricity directly, and it is a by-product of fissile radioactive fuel. Unfortunately, this is not the case. In fact, a nuclear reactor is a huge heater, if not a “boiler”, which communicates thermal energy to a coolant, which performs useful work to generate electricity through a conventional generator.
To answer many questions, consider the design of a nuclear reactor. Structurally, any nuclear reactor includes the following elements:
- Central core with a fast neutron moderator. This is where the fission reaction takes place;
- a layer reflecting neutrons. It is necessary to reduce penetrating ionizing radiation, as well as to increase the efficiency of the installation;
- radiation protection. As a rule, lead shields;
- coolant. In all modern reactor models is an indispensable part;
- a core device for controlling the course of the decay reaction of nuclei;
- cooling circuit;
- remote control mechanism.
For the operation of nuclear reactor boilers, heavy metals are used - Uranium-233, 235 or Plutonium-239. The features of these elements are that each unit of time in their atomic structure occurs spontaneous decay (splitting). In this process, neutrons are released from the nuclei of atoms. An atom that has lost (acquired) a neutron turns into another element of the periodic table. For example, in this way, Plutonium-239 is obtained from Uranium-238. Hitting neighboring atoms of the fuel material, due to their high speed, they release additional neutrons. The total number increases in progression - a chain reaction of fission of nuclei begins . If at this stage no measures are taken to regulate it, the result will be an uncontrolled nuclear chain reaction, accompanied by an avalanche-like release of a colossal amount of energy (nuclear explosion).
Two mandatory methods are used for control: introducing into the active zone a moderator that reduces the neutron velocity to the level of a self-sustaining process, as well as introducing the right amount of control rods (cadmium or boron) that absorb excess neutrons.
When the nuclei decay, heat is released that heats the circulating coolant (water), it is converted into steam and rotates the turbine of the electric generator.
This is the basic scheme. There are several varieties of it. For example, the heat transfer water may be naturally boiling or pressurized. The latter makes it possible to obtain superheated steam, increasing efficiency. In addition, water is not the only type of coolant (it can be gas or liquid metal). Also, in some modifications of the reactors, a moderator is not used.