The high boiling point of lead provides safety advantages as it can cool the reactor efficiently even if it reaches several hundred degrees Celsius above normal operating conditions. The two main design approaches to sodium-cooled reactors are pool type and loop type. These are opposed to the first generation reactors, which refer to the early class of power reactors. as it allows for a high power density with a low coolant volume. Each type of SMR has its own advantages and disadvantages, and the choice of reactor technology depends on various factors, including the intended use, the site characteristics, and the regulatory requirements. temperature operation of a bismuth-cooled reactor at relatively low pressures. 43 0 obj <> endobj The control rods of a typical PWR are inserted from the top (through the reactor head), whereas those of a BWR are inserted from the bottom. The Calder Hall reactor design was fueled with slugs of natural uranium metal canned in aluminum, was cooled with carbon dioxide, and employed a moderator consisting of a block of graphite pierced by fuel channels. Liquid metal cooled reactors were studied by Pratt & Whitney for use in nuclear aircraft as part of the Aircraft Nuclear Propulsion program.[9]. Plant Modernization," Physics 241, Stanford University, Winter 0000004408 00000 n A sodium-cooled fast reactor is a fast neutron reactor cooled by liquid sodium. On the other hand, even though the internals of the PWR are simpler, a BWR power plant is smaller, because it has no steam generators. Feed water from the condenser enters the boiler, the heated sodium potassium liquid passing through the tube gives heat to the water thus converting it into steam (superheated). One example of this was the A few examples include organic liquid-cooled and liquid-moderated reactors that can operate like a pressurized-water reactor but without requiring pressures in the primary circuit to be as high as those in the traditional PWR; sodium-cooled graphite-moderated reactors; and heavy-water reactors built in a pressure-vessel design. This makes them attractive in situations where size and weight are at a premium, like on ships and submarines. Most LMRs are fueled with uranium dioxide or mixed uranium-plutonium dioxides. Over time, light-water reactors have tended to increase in size, reaching electric capacity ratings of 1,000 megawatts or more. More Information on reusing IAEA copyright material. work is the author's own and that Stanford University provided no input endstream endobj 44 0 obj<> endobj 45 0 obj<>/Encoding<>>>>> endobj 46 0 obj<> endobj 47 0 obj<>/Font<>/ProcSet[/PDF/Text/ImageB]>> endobj 48 0 obj<>stream [8] The electrically-conductive molten sodium can be moved by electromagnetic pumps. For example, the metal's high refractory fuel elements. In 2000 the High Temperature Reactor-10 (HTR-10), a Chinese reactor based on the German pebble-bed design, began operating at a nominal steady-state power level of 10 megawatts. [19], Actinides and fission products by half-life, Plus radium (element 88). The depletion of fossil fuels has led to a search for new methods of fuel and chemical production from biomass. %PDF-1.6 % startxref The Sodium Reactor Experiment was an experimental sodium-cooled graphite-moderated nuclear reactor (A Sodium-Graphite Reactor, or SGR) sited in a section of the Santa Susana Field Laboratory then operated by the Atomics International division of North American Aviation. Seminar Series," Argonne National Laboratory, energy systems to address several large-scale nuclear use challenges, A liquid metal cooled reactor (LMCR) is an advanced type of nuclear reactor that uses a liquid metal as the primary coolant. The Magnox design is replaced by the advanced gas cooled reactor with a similar cooling system but some changes to improve the economic performance. Liquid metal cooled reactors were first adapted for breeder reactor power generation. 0000005339 00000 n A large variety of reactor types have been built and operated on an experimental basis. potential to serve as an opportunity to further develop the technology's The Very High Temperature Reactor (VHTR) is a type of high-temperature gas cooled reactors (HTGRs) that, in concept, can reach high outlet temperatures, up to 1000 C. [6] Like PWRs, the sodium-cooled fast reactor (SFR) utilizes . other rights, including commercial rights, are reserved to the Safety features include a long thermal response time, a large margin to coolant boiling, a primary cooling system that operates near atmospheric pressure, and an intermediate sodium system between the radioactive sodium in the primary system and the water and steam in the power plant. The reactor core in all such systems is a tightly packed bundle of fuel in steel cladding through which the sodium coolant flows to extract the heat. Neutron cross-section of steel is higher than beryllium, and this shift requires the application of enriched uranium fuel to balance. The superheated water vapour is then used as the working fluid to turn the steam turbine. The prismatic block reactor has a configuration of prismatic block core, in which hexagonal graphite blocks are placed in a cylindrical pressure vessel. sodium-oxide aerosols and explosions caused by sodium fires due to the The reactor has two coolant loop. In comparison, a GCR can run at temperatures up to 800850C and yield a heat-to-electricity conversion efficiency of more than 40% using conventional steam turbine facilities or as high as 50% using a more advanced gas turbine apparatus. against overheating if coolant flow is lost. . In the United States, however, the greatest success has been with metal fuels. The author grants Not only one of the cheapest available metals (DuPont reactor grade Niapure is approximately $1.60/lb), liquid sodium is further advantageous because it carries a high power density and is non-corrosive to stainless steels: oxygen reacts preferentially with sodium, forming Na 2 O. Magnesium oxide has an order of magnitude lower probability of interacting with neutrons (thermal and fast) than elements such as iron. Graphite moderator can retain its mechanical strength and purity at high temperature. One of the methods of converting biomass into valuable products is the process of pyrolysis. Then, it passes through boiler assemblies (steam generator) outside the core but still within the concrete pressure vessel. The US EBR-2, French Phnix and others used this approach, and it is used by India's Prototype Fast Breeder Reactor and China's CFR-600. The Magnox also ran almost cooler gas temperatures than other power-producing plants, which led to less efficient steam conditions. Capacity factor refers to the ratio of time that a reactor is operating at full power during a given period versus the total available time during that same period. This means that the pressure of nitrogen cannot be maintained. This There are two competitive designs of this reactor type: (1) a German pebble bed system that uses spherical fuel elements, nominally 60 mm (2.5 inches) in diameter, containing a graphite-and-fuel mixture coated in a graphite shell; and (2) an American version in which the fuel is loaded into precisely located graphite hexagonal prisms that interlock to create the core of the vessel. Sodium has high thermal conductivity, meaning that it can effectively remove heat from the fuel rods. xref (GIF), an international collective representing 14 countries, has led Therefore, they are also called supercritical boilers. The Encapsulated Nuclear Heat Source (ENHS) concept is a liquid metal-cooled reactor of 50 MWe being developed by the University of California. Liquid metal coolant has been applied to both thermal- and fast-neutron reactors. Due to their high thermal conductivity, metal coolants remove heat effectively, enabling high power density. If you would like to learn more about the IAEAs work, sign up for our weekly updates containing our most important news, multimedia and more. The first generation of French nuclear power plants was UNGGs. Under atmospheric condition, sodium boils at 880C and freezes at 95C, therefore sodium is first melted by electric heating system and then pressurized to about 7 bar, thus the sodium turns into liquid phase. Do You Know Which African American Inventor Created Which Product? 1, the Each fuel assembly to be removed is grasped by a fuel-handling tool and then lifted from its position in the core into a shielded cask, within which the assembly is transferred to a storage pool for cooling while it is still highly radioactive. Reactors (SFR) have received concentrated research efforts from some Large pressurized water reactors, on the other hand, have a significant cost disadvantage compared to gas cooled reactors; their pressure vessels are more highly contaminated and normally will need to be cut up before being transported for disposal. Greater inherent safety. Sodium exhibits the best combination of . MSRs are reactors that use a fluid fuel in the form of either molten fluoride or chloride salt mixed with a liquid fuel in the form of UF 4 or thorium. Combined with the much higher temperatures achieved in the reactor, this means that the reactor in shutdown mode can be passively cooled. 0000015331 00000 n Liquid metallic sodium may be used to carry heat from the core. [3] "GIF R&D 3. Because of its large heat storage capacity, it was expected to be able to produce surge power of 500 MWe for 5+ hours, beyond its continuous power of 345 MWe. basic power cycles in nuclear power plants. These reactors apply natural or somewhat enriched uranium as fuel. As the world's population continues to grow, the need The result of this policy is the Canada Deuterium Uranium (CANDU) reactora line of natural uranium-fueled reactors moderated and cooled by heavy water. 2017. This makes them attractive for improving power output, cost effectiveness, and fuel efficiency in nuclear power plants. A liquid metal cooled reactor (LMCR) is an advanced type of nuclear reactor that uses a liquid metal as the primary coolant. Despite sodium's low specific heat (as compared to water), this enables the absorption of significant heat in the liquid phase, while maintaining large safety margins. Regulatory Commission - Advanced Fuel Cycle Research and Development oxygen-free system prevents corrosion. reactors including other types of fast reactors. Another advantage of these types of reactors is that they are small and can operate at high temperatures. The Very High Temperature Reactor (VHTR) is a type of high-temperature gas cooled reactors (HTGRs) that, in concept, can reach high outlet temperatures, up to 1000 C. Light-water reactors (LWRs) are power reactors that are cooled and moderated with ordinary water. sustainability and efficiency. Advantages and Disadvantages Advantages FBRs have improved neutron economy FBRs can recycle nuclear waste FBRs can produce fuel for thermal reactors FBRs liquid metals have superior heat transfer properties FBRs do not use pressure vessel Disadvantages FBRs must use superior control system However, the half-life of activated sodium is only 15 hours. Sodium need not be pressurized since its boiling point is much higher than the reactor's operating temperature, and sodium does not corrode steel reactor parts, and in fact, protects metals from corrosion. (i) Features: The SFR is based on the technologies of conventional liquid metal fast breeder reactor and integral fast reactor. Beside its highly corrosive character,[4][5] its main disadvantage is the formation by neutron activation of 209Bi (and subsequent beta decay) of 210Po (T'"`UNIQ--templatestyles-0000000D-QINU`"'12 = 138.38 day), a volatile alpha-emitter highly radiotoxic (the highest known radiotoxicity, above that of plutonium). Further advantages of tin are the high boiling point and the ability to build a crust even over liquid tin helps to cover poisonous leaks and keeps the coolant in and at the reactor. Most LMRs are breeders or are capable of breeding, which is to say that they all produce more fissile material than they consume. The reference liquid coolants for Generation IV reactors are sodium (Na), lead (Pb) and the lead-bismuth eutectic (Pb-Bi). Ultimately, this fuel will be transferred to the U.S. Department of Energy for reprocessing or waste disposal or both, though a viable disposal program has not yet been established. Tin causes any reactor type to be unusable for normal operation. The alloy that forms has a low eutectic melting temperature. Abstract Iron-chromium-aluminum alloys containing 15-20 wt.% Cr and 4-6 wt.% Al have shown excellent corrosion resistance in the temperature range up to 600 C or higher in liquid lead and lead-bismuth eutectic environments by the formation of protective Al2O3 layers. In addition, there may be a secondary shutdown system that involves the injection of nitrogen into the coolant. Together with the BN-600, one of only two commercial fast reactors in the world. the reactor can also be used as a breeder to regenerate fuel. In fact, the steam generators of a PWRthere are typically four of them in a big plantare larger than the reactor vessel itself. century. Therefore the same design of turbo-generator could be applied. thermal conductivity and heat capacity creates a large thermal inertia There are also numerous research reactors, and some navies of the world have submarines or surface ships driven by propulsion reactors. Each type of SMR has its own advantages and disadvantages, and the choice of reactor technology depends on various factors, including the intended use, the site characteristics, and the regulatory requirements. Designs," Institut de Radioprotection et de Sret [3,4] Because of this, SFRs A disadvantage of sodium is its chemical reactivity, which requires special precautions to prevent and suppress fires. explosion that delayed the reactor's repairs after a partial core The high temperatures reached by the coolant (the Phnix reactor outlet temperature was 560 C) permit a higher thermodynamic efficiency than in water cooled reactors. The many Member States are interested in working on advanced High-Temperature Gas Cooled Reactors (HTGRs) that employ helium as a coolant. The fuel assembly of a CANDU reactor, which consists of a bundle of short zirconium alloy-clad tubes containing natural uranium dioxide pellets, can be changed while the system is running. 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Fast-Neutron reactors `` GIF R & D 3 are placed in a pressure!
