useheavy waterI.eDeuterium oxideAsModeratorOfnuclear reactorIs called heavy water reactor, orHeavy water reactorAlmost all reactors today use heatneutronTherefore, moderator is an indispensable part of the reactor. If moderator collides with neutron to reduce the number of neutrons, it will lose its significance.Therefore, heavy water is a very excellent moderatorgraphiteSide by side is the most commonly used moderator.
1942 United StatesUniversity of ChicagoThe world's first self-sustaining chain reaction device was built, which ushered in a new era of nuclear energy utilization.
The reactor is composed ofCore、Cooling system、Moderating system、Reflector、Control and protection system、Shielding system、Radiation monitoring systemEtc.
Fuel
The fuel of the reactor is not coal or oil, butFissile material。natureThe only natural fissile material is U-235Natural uraniumOnly 0.711%, and the other twoisotopeU-238 andU-234They account for 99.238% and 0.0058% respectively, and the latter two are not easy to fission.
In addition, there are two types ofFissile materialU-233 and Pu-239.
Use these fissile materials to make metalMetal alloy、oxide、carbideAnd other forms as fuel for the reactor.
Due to slow speedneutronMore likely to causeU-235Fission, and neutron fission is fast neutron, so some reactors need to put materials that can slow down the neutron speed, which is calledModerator, general moderators include waterheavy water、graphiteEtc.
Reflector
ReflectorLocated around the active area, it can be heavy water, light waterberyllium、graphiteOr other materials.It canActive regionInternally escapedneutronReflect back to reduce neutron leakage.
The structural form of reactor is various, which is based on the fuel form, coolant typeneutronenergyThe distribution form, special design needs and other factors can be built into various types of reactors.There are thousands of reactors of different sizes in the world, and their classifications are also varied.Fission is caused by thermal neutrons and fast neutrons according to energyThermal reactorandfast reactor；PresscoolantThere are light water reactors, namelyOrdinary water reactor(also divided intoPWRandBoiling water reactor）、Heavy water reactor、Gas cooled reactorandSodium cooled reactor。
It is divided into:
（1）Research and test reactorIt is used to study the characteristics of neutronsRadiation protectionAnd material science;
(2) Production reactor, mainly to produce new fissile materials U-233 and Plutonium-239;
It refers to the reactor used as an experimental research tool. It does not include the reactor built for the research and development of specific reactor types, which is itself the research object, such as prototype reactor, zero power reactor, various model reactors, etc.The experimental research field of research experimental reactor is very wide, including reactor physics, reactor engineering, biology, chemistry, physics, medicine, etc. At the same time, it can also produce variousradio isotopeAnd training reactorScientific and technical personnel。There are many kinds of research and experiment reactors, such as swimming pool type research and experiment reactor, in which water not only acts as moderator, reflector and coolant, but also plays a major role in shielding.Because the pool is often made into a swimming pool shaped oblong, it gets its name.
Tank type research and experiment reactor: since higher operating temperature and larger coolant flow can only be achieved in the pressurized system, the pressurized tank type structure must be adopted.
In additionsolidModeratorResearch and Experimental Reactor, Homogeneous Research and Experimental ReactorFast neutronExperimental reactor, etc.
Production reactor
Mainly used for productionfissile materials Or other materials, or used for industrial scaleirradiation。Production reactors include plutonium production reactors,Tritium reactorAnd plutonium and tritium production dual-use reactor, isotope production reactor and large-scale irradiation reactor. Unless otherwise specified, the production reactor usually refers to the plutonium production reactor.The reactor has a simple structure. The fuel elements in the production reactor are both fuel and raw materials for producing plutonium-239.neutronFromNatural uraniumU-235 in the fabricated element.U-235Fission neutronThe output is 2-3.Except maintenanceFission reactionIn addition to the required neutrons, the remaining neutrons are absorbed by U-238, which can be converted into Pu-239. On average, 0.8 plutonium atoms can be obtained by burning one U-235 atom.It can also be produced with production reactorthermonuclearFuel tritium.useheavy waterTritium production of type I production reactor is better than that of type II production reactorgraphiteThe production reactor produces 7 times more tritium.
Power reactor
Power reactors in the world can be divided into submarine power reactors and commercial power reactors.Nuclear submarines usually usePWRAs its power unit.The reactors for commercial scale nuclear power plants mainly include pressurized water reactorsBoiling water reactor、Heavy water reactor、graphiteGas cooled reactor andfast reactorEtc.
PWR
Use low enriched (uranium - 235 concentration is about 3%)Uranium dioxideAs fuel and high-pressure waterModeratorandcoolant。It is the most mature heap type in the world at present.
heavy waterdoModeratorHeavy water (or boiling light water) can be used as coolant, natural uranium can be used as fuel, and only the CANDU reactor developed in Canada can reach the commercial level. China is building aHeavy water reactor nuclear power plant。
Graphite gas cooled reactor
withgraphitedoModerator, carbon dioxide as coolantNatural uraniumThe maximum operating temperature of fuel is 360 ℃. This kind of reactor has rich operating experience and has operated for 650 reactor years by the early 1990s.
Use light water asModeratorandcoolantOfnuclear reactorgo by the name ofLight water reactor, including boiling water reactor and pressurized water reactor light water, which is general water, is widely used as moderator and coolant of reactor.Andheavy waterIn contrast, light water has the advantage of low cost. In addition, its deceleration efficiency is also very high. The characteristics of boiling water reactor are thatWater vaporIt is directly sent to the gas turbine without heat exchanger, thus preventingthermal efficiencyThe pressurized water reactor uses high pressure to suppress boiling, and generally adds 100 to 160 atmospheric pressure to light water, so that the heat exchanger completely separates the primary cooling system (heat generated by taking out the core) and the secondary cooling system (steam sent to the worm gear).
Water is produced in nuclear reactorsneutronOne of the best materials for deceleration.Use heavy waterDeuterium oxide(D2O) As moderator, the nuclear reactor is called heavy water reactor, orHeavy water reactorToday, almost all reactors usethermal neutron, soModeratorIt is an indispensable part of the reactor. If moderators collide with neutrons to reduce the number of neutrons, it will lose its significance.So,heavy waterIt is a very excellent moderatorgraphiteSide by side is the most commonly used moderator.
By-product
Announce
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Ratio of by-products (such as plutonium, tritium, etc.) produced by heavy water reactorLight water reactorIt can produce more, and these by-products can be used to produce fission type atomic bombs, fusion type atomic bombsBulletAnd primary thermonuclear weapons.
advantage
Although ordinary light water is used in some reactors (such asLight water reactor）Can also be used as neutronsModeratorHowever, because light water can absorb neutrons and reduce the neutron concentration in the reactor, the nuclear fuel in the light water reactor needs to be enriched to a higher degree to reachCritical massTo ensure continuous response.Therefore, compared with light water reactors, heavy water reactors have very low requirements for the concentration of effective radioisotopes in nuclear fuel, which can eliminate most of theIsotope separationProcess, and itsSpent fuelPost processing is not necessary.
harm
Some opponents of heavy water reactors believe that this type of reactor is availableLow enriched uraniumEven non enriched uranium is used as nuclear fuel, so the establishment of nuclear power plants based on such reactors will increase the risk of nuclear proliferation: when a country has mastered the technology of heavy water reactors, it only needsNatural uraniumThe nuclear power plant can be operated andnuclear reactionCreate a danger that can be used to make nuclear weaponsradioactivityAs a by-product, these countries can bypassenriched uraniumTo develop nuclear weapons.
India once extracted plutonium from a research heavy water reactor called "CIRUS" and used it for the first timenuclear test("Laughter Buddha Nuclear Test").
