A nuclear reactor, also known as an atomic reactor or reactor, is a device that can maintain a controllable self-sustaining chain nuclear fission reaction to realize the utilization of nuclear energy.
The nuclear reactor can have a self-sustaining chain fission process without adding a neutron source through reasonable arrangement of nuclear fuel. Strictly speaking, the term reactor should cover fission reactors, fusion reactors and fission-fusion hybrid reactors, but generally it only refers to fission reactors. Nuclear energy is mainly used for power generation, but it is also widely used in other aspects. Such as nuclear heating and nuclear power.
To generate nuclear energy with reactors, the following four problems need to be solved:
1. Provide necessary conditions for the nuclear fission chain reaction to be carried out.
2. The chain reaction must be controlled by people through certain devices. Uncontrolled fission energy can not only be used for power generation, but also lead to disasters.
3. The energy generated by fission reaction should be taken out of the reactor safely.
4. Neutrons and radioactive substances produced in fission reaction are very harmful to human body, so we must try to avoid their harm to nuclear power plant staff and nearby residents.
Extended information:
Atoms are composed of nuclei and extranuclear electrons. The nucleus consists of protons and neutrons. When the nucleus of uranium-235 is bombarded by foreign neutrons, one nucleus will absorb a neutron and split into two nuclei with smaller mass, and at the same time release 2-3 neutrons. The neutrons produced by this fission bombard another uranium-235 nucleus, causing new fission. This continuation is the chain reaction of fission.
chain reaction generates a lot of heat energy. Only by taking away heat with circulating water (or other substances) can the reactor be prevented from being burnt down due to overheating. The derived heat can turn water into steam and push the steam turbine to generate electricity. Therefore, the most basic composition of nuclear reactor is fission nucleus+heat carrier. But only these two items can't work.
Because high-speed neutrons will scatter in large quantities, it is necessary to slow down neutrons and increase the chance of collision with the nucleus; The working state of nuclear reactor should be determined according to people's wishes, which requires control facilities; Uranium and fission products are highly radioactive and will cause harm to people, so reliable protective measures must be taken.
when an accident occurs in a nuclear reactor, it is necessary to prevent radiation leakage under various accident conditions, so the reactor also needs various safety systems. To sum up, the reasonable structure of nuclear reactor should be: nuclear fuel+moderator+heat carrier+control facilities+protective devices+safety facilities.
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