What Types of Nuclear Reactors Exist?

The structural form of nuclear reactors is diverse. He can be divided into various types of nuclear reactors based on factors such as fuel form, type of coolant, neutron energy distribution form, and special design needs.
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The structural form of nuclear reactors is diverse. He can be divided into various types of nuclear reactors based on factors such as fuel form, type of coolant, neutron energy distribution form, and special design needs.

Chinese name

Nuclear reactor classification

Foreign name

Classification of nuclear reactor

There are currently thousands of large and small nuclear reactors in the world, and their classifications are also diverse.

According to the neutron energy spectrum classification, it can be divided into thermal neutron reactor, neutron reactor and fast neutron reactor. In a fast neutron reactor, fission is caused by fast neutrons (with an average energy of about 0.1 MeV), so no neutron moderator material can be stored in the reactor. All developed countries in the world have paid great attention to this reactor type. There is a certain amount of moderator in the neutron energy reactor, and fission is mainly caused by neutron energy. In fast neutron reactors or neutron reactors, high-enrichment nuclear fuel must be used in the reactor. Fission in a thermal neutron reactor is caused by thermal neutrons, so there must be enough moderator in the reactor. Natural uranium, low-enriched uranium fuel, ²³³ U, and ²³⁹ Pu can all be used as nuclear fuel for thermal neutron reactors. The vast majority of built reactors in the world fall into this category. ^[1]

The coolant in the nuclear reactor is the working medium of the nuclear fission energy generated in the carrier reactor to the thermal system outside the reactor. The thermo-hydraulic properties of nuclear reactors mainly depend on the selected coolant. Therefore, from the perspective of the thermo-hydraulics of nuclear reactors, the types of nuclear reactors are often divided according to the coolant. According to the type of coolant, it can be divided into gas-cooled reactors, liquid-cooled reactors, and liquid metal-cooled reactors. Gas-cooled reactors include CO ₂ and He gas-cooled reactors; liquid-cooled reactors include light-water-cooled pressurized water and boiling water reactors, and heavy-water-cooled heavy water reactors. Liquid-cooled reactors that can also be cooled with organic compounds; liquid metal cooling The reactors mainly include sodium, sodium-potassium alloy, bismuth-cooled, lithium-cooled, lead-bismuth alloy cooled reactors. ^[1]

According to the classification of nuclear reactor applications, it can be roughly divided into three categories: production reactors, research reactors and power reactors. Production reactors are mainly used to produce new fissile nuclides ²³³ U, ²³⁹ Pu and various isotopes for different purposes; research reactors are used to study neutron characteristics, and then to physics, biology, radiation protection and materials science, etc. Research; power reactors military power reactors and civilian power reactors. Nuclear-powered aircraft carriers, nuclear submarines, and nuclear-powered cruisers can be classified as military power reactors. Nuclear power plants, civilian nuclear-powered ships, aerospace nuclear power propulsion devices, nuclear-powered underwater submersibles, and underwater workstations are all classified as civilian power reactors. In addition, there are special-purpose reactors, commonly known as heating reactors, which are used for heating for different purposes, such as building heating, petroleum thermal recovery, etc .; useful nuclear energy for seawater desalination, large-scale refrigeration, hydrogen production, coal Various reactors such as liquefaction or gasification and high-temperature process heating can be referred to as seawater desalination reactors and hydrogen production reactors. ^[1]

According to the classification of nuclear reactions, they can be divided into fission reactor, fusion reactor and fission fusion reactor.

Moderators in nuclear reactors are substances that slow down neutrons and change from neutrons to thermal neutrons. Moderators have a significant impact on the physical properties of thermal neutron reactors, so reactors are often classified according to the type of moderator used, such as light water reactors, heavy water reactors, graphite moderator reactors, and beryllium or beryllium compound reactors. Heavy water (D ₂ O) is the weakest neutron absorber of all moderators, but its moderating ability is very good, so heavy water reactors can use natural uranium as nuclear fuel. Currently, a large number of pressurized water reactors and boiling water reactors are constructed using light water reactors (H ₂ O) as moderators. The nucleus of hydrogen contained in light water is the nucleus with the strongest moderating ability. A reactor with light water as a moderator has a high heating power (power density) per unit volume, which is especially suitable for nuclear-powered ships. ^[1]

Usually according to the enrichment degree of fissile nuclides such as ²³⁵ U in nuclear fuel, the reactor is classified into natural uranium fuel reactor, low enriched uranium fuel reactor, and high enriched uranium fuel reactor. There is also a plutonium breeding reactor that uses plutonium resources. ^[1]