The Soviet BN-600 is sodium cooled. These types of reactors can obtain very high fuel utilization rates and work at high temperatures. xref In addition, there may be a secondary shutdown system that involves the injection of nitrogen into the coolant. nuclear reactor. 0000001054 00000 n explosion that delayed the reactor's repairs after a partial core [3] An In this design, to penetrate the moderator and control the reaction, boron control rods are utilized. Thus, although the higher thermal efficiency is an advantage, the fuel is used less efficiently. 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. 0000000016 00000 n For fast breeders using a liquid metal cooling system, sodium is the selected coolant since it can remove heat effectively from the compact reactor core and remains in the liquid state over a fairly broad temperature range. The Soviet November-class submarine K-27 and all seven Alfa-class submarines used reactors cooled by lead-bismuth eutectic and moderated with beryllium as their propulsion plants. Although a number of AGRs have been built in the United Kingdom, maintenance and malfunction issues have proved to be more costly than expected, and no new AGRs are projected for construction. 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. 43 0 obj <> endobj Utilities schedule maintenance and reload during the spring and fall, when electricity demand is lowest and the electrical grid usually has reserve capacity. Hence, the salt can be both the fuel and the coolant at the same time. Liquid metals generally have high boiling points, reducing the probability that the coolant can boil, which could lead to a loss-of-coolant accident. And fire hazard risk, corrosion and production of radioactive products are other threats. The many Member States are interested in working on advanced High-Temperature Gas Cooled Reactors (HTGRs) that employ helium as a coolant. Liquid sodium is currently used in the Russian BN-600 and BN-800 reactorsthe only ones operating SFRs so far in the worldand is proposed to be used in Generation IV SFRs. Also, a second life extension of up to 80 years may be economical in some cases. 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. interested in managing their nuclear supply and nuclear waste. other than typesetting and referencing guidelines. This makes them attractive for improving power output, cost effectiveness, and fuel efficiency in nuclear power plants. Other significant types are briefly described, as are research and propulsion reactors. Sodium at high temperatures ignites in contact with oxygen. These reactors apply natural or somewhat enriched uranium as fuel. This allows for the coolant to operate at higher temperatures and lower pressures than current reactorsimproving the efficiency and safety of the system. Options available to nuclear plant operators are to store the spent fuel more densely than originally planned, to build new pools, or to store the oldest in aboveground silos (dry storage) locally on site. Since they use various forms of fuel and cladding, they avoid chemical reactions of steam/zirconium cladding which can release explosive hydrogen gas under unintended conditions in light water reactors. Therefore, short-term reprocessing of the fuel is essential and requires highly shielded facilities for this. suffered from corrosion and sodium leaks that resulted in runaway [4] The six chosen concepts were Plant Modernization," Physics 241, Stanford University, Winter The sodium-cooled fast reactor (SFR) uses liquid metal (sodium) as a coolant instead of water that is typically used in U.S. commercial power plants. A new assembly is simply pushed into one end of a pressure tube, and the spent fuel that it replaces is collected as it is extruded at the opposite end. temperature operation of a bismuth-cooled reactor at relatively low pressures. Another advantage of liquid sodium coolant is that sodium melts at 371K and boils / vaporizes at 1156K, a difference of 785K between solid / frozen and gas / vapor states. Sodium-cooled fast reactors are described briefly in Chapter 3.Some more details are discussed below [15-18]. The once-through boiler works at pressures above the critical water point pressure. Another advantage of liquid cooling is that it is more efficient in removing excess heat. Together with the BN-800, one of only two commercial fast reactors in the world. In the early 21st century, signs began to emerge of a reviving nuclear power sector in the United States as demand for reliable energy sources continued to increase and it became evident that the fleet of U.S. nuclear power plants was aging. countries, as seen by the 652 million euro budget granted to the ASTRID Both Magnox and UNGG used fuel cladding materials inappropriate for storage underwater in the medium-term that makes reprocessing a vital part of the nuclear fuel cycle. In parallel to the British Magnox design, the UNGG reactor was developed independently to meet similar requirements for electric power and plutonium generation simultaneously. 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. The arrangement of a sodium graphite reactor (SGR) is shown in Fig. In the loop type, the heat exchangers are outside the reactor tank. Water is a much stronger neutron moderator because the hydrogen atoms found in water are much lighter than metal atoms, and therefore neutrons lose more energy in collisions with hydrogen atoms. The result of this policy is the Canada Deuterium Uranium (CANDU) reactora line of natural uranium-fueled reactors moderated and cooled by heavy water. Given the The reactor was expected be sited underground and have gravity-inserted control rods. Then, it passes through boiler assemblies (steam generator) outside the core but still within the concrete pressure vessel. Each reactor has a design thermal power generation of 1,500 MW which drives a 660 MW electrical power generation set. With an increase in pressure in the Rankine cycle, the saturation temperature corresponding to that pressure increases. This change led to a greater burnup of 18,000 MW-days per fuel tonne, requiring less regular refueling. At present, gas cooled reactors account for about three percent of all reactors in commercial operations around the world. 0000015331 00000 n The name refers especially to the design done in the UK but is sometimes applied generically to any similar reactor. nuclear power plant at Dungeness Point, Kent, England. An advantage of liquid metal-cooled reactors is that they use molten metal, such as sodium, to cool the fuel rods. Together with the BN-600, one of only two commercial fast reactors in the world. For example, water cooled reactors have a possible maximum temperature limit of around 350C, which allows a conversion efficiency (the ratio of output electricity to heat) of about 3234%. 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. FCCI is eutectic melting between the fuel and the cladding; uranium, plutonium, and lanthanum (a fission product) inter-diffuse with the iron of the cladding. Do You Know Which African American Inventor Created Which Product? However, in the second generation of the gas cooled reactors, the steam generators are installed inside the concrete pressure vessel, which needs a much larger structure and, therefore, more capital costs. In the United States, strict regulation of LWRs following the Three Mile Island accident of 1979, coupled with a decrease in reactor research and development activity, made the competitive nature of new light-water installations problematic for decades. These are opposed to the first generation reactors, which refer to the early class of power reactors. University, Winter 2018. has the potential to become a prominent low-emission supplier. The heat exchanger is placed outside the concrete radiation shielding. In development. 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. generator or cause a hydrogen explosion. "The Liquid metal solution systems (in particular, solutions of uranium in bismuth) [5-12] have the following advantages over aqueous systems: Tin causes any reactor type to be unusable for normal operation. Two reactors being constructed on Changbiao Island in, Suspended for 15 years. This process has been extensively researched in recent years due to the rising prices of energy and chemicals. Thus, a capacity factor of 1.0 refers to a reactor that operates at full power 24 hours a day over the entire period of time being considered. NaK is liquid at room temperature. 0000016376 00000 n Advantages: 1. Liquid metal cooled reactors were first adapted for breeder reactor power generation. reactors including other types of fast reactors. In total, fourteen AGR reactors were built at six sites between 1976 and 1988. Furthermore, because the BWRs power density is somewhat lower than that of the PWR, the pressure vessel must be built to a larger diameter for the same reactor power. 0000010115 00000 n For example, the metal's high Furthermore, the fast neutrons Some gas cooled reactors have been constructed and operated using either carbon dioxide gas or helium for the reactor core cooling. reactors, and therefore the coolant must have very good heat transfer properties. The fact that the sodium is not pressurized implies that a much thinner reactor vessel can be used (e.g. SFRs hold several advantages over certain nuclear reactors including other types of fast reactors. It is focused on the following subjects: state of the art of liquid metal fast reactor (LMFR) development; design features and operating experience of demonstration and commercial sized nuclear power plants with sodium cooled fast reactors; lead-bismuth cooled (LBC) ship reactor operation experience and LBC fast power reactor development; Although tin today is not used as a coolant for working reactors because it builds a crust,[7] it can be a useful additional or replacement coolant at nuclear disasters or loss-of-coolant accidents. It is focused on the following subjects: state of the art of liquid metal fast reactor (LMFR) development; design features and operating experience of demonstration and commercial sized nuclear power plants with sodium cooled fast reactors; leadbismuth cooled (LBC) ship reactor operation experience and LBC fast power reactor development; treatment and disposal of spent sodium; decontamination after shutdown of the typical loop type LMFR; and an analysis of advantages and disadvantages of sodium as a coolant, giving due consideration to advances in the technology and design of sodium components. Concrete pressure vessel in recent years due to liquid metal cooled reactor advantages and disadvantages first generation reactors, which lead... Reducing the probability that the sodium is not pressurized implies that a much thinner vessel... Boiler works at pressures above the critical water point pressure with the BN-600, one of only two fast... Working on advanced High-Temperature Gas cooled reactors account for about three percent of all reactors the... Fast reactors are described briefly in Chapter 3.Some more details are discussed below [ 15-18 ] is used less.... In some cases K-27 and all seven Alfa-class submarines used reactors cooled by lead-bismuth and! The UK but is sometimes applied generically to any similar reactor, corrosion and production of products... Be both the fuel rods products are other threats the sodium is not pressurized implies that a thinner. Reactors account for about three percent of all reactors in commercial operations around the world with... Concrete pressure vessel generically to any similar reactor the core but still within the concrete radiation.! Corrosion and production of radioactive products are other threats beryllium as their propulsion plants molten metal, such sodium. A 660 MW electrical power generation set the same time in recent years due to the early class of reactors. 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