Nuclear Reactor Type And Working Principle
Nuclear reactors, also known as atomic energy reactors or reactors, are devices that maintain a controlled self-sustaining chain nuclear fission reaction to achieve nuclear energy utilization. Nuclear reactor through the rational distribution of nuclear fuel, so that no additional neutron source in the conditions under which self-sustaining chain fission process. Strictly speaking, the term reactor should cover fissile reactors, fusion reactors, fission fusion stacks, but in general only finger fissures.
Nuclear reactor is the heart of nuclear power plants, it works like this:
The atoms consist of nuclei and nuclear electrons. The nucleus consists of protons and neutrons. When the nucleus of uranium 235 is bombarded by external neutrons, a nucleus will absorb a neutron split into two smaller nuclei, while releasing 2-3 neutrons. This fission of the neutrons and bombardment of another uranium 235 nuclei, causing a new fission. So the ongoing chain reaction is fission. Chain reaction produces a lot of heat. Use circulating water (or other substances) to take away heat to prevent the reactor from burning overheating. Derived heat can make water into water vapor, to promote the turbine power generation. It can be seen that the most basic composition of nuclear reactors is fission nuclei + heating body. But only these two can not work. Because the high-speed neutrons will be a lot of scattering, which requires neutrons to increase the chance of collision with the nucleus; nuclear reactors according to their wishes to determine the working state, which must have control facilities; uranium and fission products are strong radioactive, Will cause harm to people, so there must be a reliable protective measures; nuclear reactor accident, to prevent a variety of accident conditions, radiation leakage, so the reactor also need a variety of security systems. In summary, the rational structure of the nuclear reactor should be: nuclear fuel + moderator + heating body + control facilities + protective equipment + safety facilities.
It should also be noted that uranium ore can not do nuclear fuel directly. Uranium ore to be selected, crushed, acid leaching, enrichment and other procedures, made of a certain uranium content, a certain geometric shape of the uranium rods or spherical fuel to participate in the reactor work.
Depending on the use, nuclear reactors can be classified into the following types
① neutron beam used in experiments or the use of neutron beam nuclear reaction, including research reactor, material experiments.
② production of radioactive isotopes of nuclear reactors.
③ production of nuclear fissile material nuclear reactor, known as the production reactor.
④ to provide heating, desalination, chemical and other heat with the nuclear reactor, such as multi-purpose heap.
⑤ nuclear power generation for the occurrence of nuclear reaction, known as the generator stack.
⑥ used to propel ships, aircraft, rockets and other nuclear reactors, known as power reactor.
In addition, the nuclear reactor is divided into natural uranium reactor according to the type of fuel, enriched uranium reactor, thorium reactor; according to the neutron energy is divided into fast neutron reactor and thermal neutron reactor; according to the coolant (heat carrier) material is divided into water- Cold storage, organic liquid cold reactor, liquid metal cold reactor; according to moderator is divided into graphite reactor, water reactor, organic reactor, molten salt reactor, sodium cold reactor; according to neutron flux is divided into high-throughput reactor and general energy Heap; according to the thermal state is divided into boiling heap, non-boiling heap, pressurized water reactor; according to the operation mode is divided into pulse reactor and steady state heap, and so on. The concept of nuclear reactors can have more than 900 designs, but in reality very limited.