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115-459: The SLOWPOKE-2 reactors (most numerous of SLOWPOKE-family reactors) originally used 93% highly enriched uranium in the form of 28% uranium - aluminium alloy with aluminium cladding, and then in 1985 a new low enriched uranium design (~19.9 % enriched) was commissioned using ceramic UO 2 fuel . The core is an assembly of about 200-300 fuel pins , only 22 centimetres (8.7 in) diameter and 23 centimetres (9.1 in) high, surrounded by

230-417: A laser enrichment process known as SILEX ( separation of isotopes by laser excitation ), which it intends to pursue through financial investment in a U.S. commercial venture by General Electric, Although SILEX has been granted a license to build a plant, the development is still in its early stages as laser enrichment has yet to be proven to be economically viable, and there is a petition being filed to review

345-418: A socialist economy (such as in the former Eastern Bloc ) which lacked heat metering and means to adjust the heat delivery to each apartment. This led to great inefficiencies – users had to simply open windows when too hot – wasting energy and minimising the numbers of connectable customers. District heating systems can vary in size. Some systems cover entire cities such as Stockholm or Flensburg , using

460-480: A 20% or higher concentration of U. This high enrichment level is essential for nuclear weapons and certain specialized reactor designs. The fissile uranium in nuclear weapon primaries usually contains 85% or more of U known as weapons grade , though theoretically for an implosion design , a minimum of 20% could be sufficient (called weapon-usable) although it would require hundreds of kilograms of material and "would not be practical to design"; even lower enrichment

575-425: A SLOWPOKE nuclear reactor to continuously recharge the ship's batteries during submerged operations. A good deal of work had been done on potential marine applications of the reactor at Royal Military College of Canada . SLOWPOKE reactors are used mainly for neutron activation analysis (NAA), in research and as a commercial service, but also for teaching, training, irradiation studies, neutron radiography (only at

690-773: A blendstock to dilute the unwanted byproducts that may be contained in the HEU feed. Concentrations of these isotopes in the LEU product in some cases could exceed ASTM specifications for nuclear fuel if NU or DU were used. So, the HEU downblending generally cannot contribute to the waste management problem posed by the existing large stockpiles of depleted uranium. Effective management and disposition strategies for depleted uranium are crucial to ensure long-term safety and environmental protection. Innovative approaches such as reprocessing and recycling of depleted uranium could offer sustainable solutions to minimize waste and optimize resource utilization in

805-513: A consistent heat output day to day and between summer and winter. Good examples are in Vojens at 50 MW, Dronninglund at 27 MW and Marstal at 13 MW in Denmark. These systems have been incrementally expanded to supply 10% to 40% of their villages' annual space heating needs. The solar-thermal panels are ground-mounted in fields. The heat storage is pit storage, borehole cluster and

920-481: A district-heating system based on SDR technology were estimated to be competitive with that of conventional fossil fuels . However, the market for this technology did not materialize, and the proposed SES-10 ( SLOWPOKE-4 based on SDR experience) was never built, and the SDR shutdown for decommissioning in 1989. During the mid-1980s Canada briefly considered converting its Oberon -class submarines to nuclear power using

1035-500: A fixed beryllium annulus and a bottom beryllium slab. Criticality is maintained as the fuel burns up by adding beryllium plates in a tray on top of the core. The reactor core sits in a pool of regular light-water, 2.5 metres (8 ft 2 in) diameter by 6 metres (20 ft) deep, which provides cooling via natural convection. In addition to passive cooling, the reactor has a high degree of inherent safety ; that is, it can regulate itself through passive, natural means, such as

1150-712: A hot water resource outside of Boise, Idaho. In 1892, after routing the water to homes and businesses in the area via a wooden pipeline, the first geothermal district heating system was created. As of a 2007 study, there were 22 geothermal district heating systems (GDHS) in the United States. As of 2010, two of those systems have shut down. The table below describes the 20 GDHS currently operational in America. Use of solar heat for district heating has been increasing in Denmark and Germany in recent years. The systems usually include inter seasonal thermal energy storage for

1265-522: A low-temperature internal heat distribution system can install an efficient heat pump delivering heat output at 45 °C. An older building with a higher-temperature internal distribution system e.g. using radiators will require a high-temperature heat pump to deliver heat output. A larger example of a fifth generation heating and cooling grid is Mijnwater in Heerlen, the Netherlands. In this case

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1380-409: A mix of ions . France developed its own version of PSP, which it called RCI. Funding for RCI was drastically reduced in 1986, and the program was suspended around 1990, although RCI is still used for stable isotope separation. "Separative work"—the amount of separation done by an enrichment process—is a function of the concentrations of the feedstock, the enriched output, and the depleted tailings; and

1495-525: A negatively charged plate and collected. Molecular laser isotope separation uses an infrared laser directed at UF 6 , exciting molecules that contain a U atom. A second laser frees a fluorine atom, leaving uranium pentafluoride , which then precipitates out of the gas. Separation of isotopes by laser excitation is an Australian development that also uses UF 6 . After a protracted development process involving U.S. enrichment company USEC acquiring and then relinquishing commercialization rights to

1610-500: A particular vortex tube separator design, and both embodied in industrial plant. A demonstration plant was built in Brazil by NUCLEI, a consortium led by Industrias Nucleares do Brasil that used the separation nozzle process. However, all methods have high energy consumption and substantial requirements for removal of waste heat; none is currently still in use. In the electromagnetic isotope separation process (EMIS), metallic uranium

1725-464: A prototype unit called SLOWPOKE (both the name of the reactor and of the prototype reactor class of 2 reactors it was a member of; especially later when further generations of SLOWPOKE reactors had appeared, these type of reactors were named SLOWPOKE-1 ), was designed and built at Chalk River Laboratories . It was primarily intended for Canadian universities, providing a higher neutron flux than available from small commercial accelerators, while avoiding

1840-433: A significant contributor to global energy security and environmental sustainability, effectively repurposing material once intended for destructive purposes into a resource for peaceful energy production. The United States Enrichment Corporation has been involved in the disposition of a portion of the 174.3 tonnes of highly enriched uranium (HEU) that the U.S. government declared as surplus military material in 1996. Through

1955-499: A steel heat service pipe, an insulating layer ( polyurethane foam) and a polyethylene (PE) casing, which are bonded by the insulating material. While polyurethane has outstanding mechanical and thermal properties, the high toxicity of the diisocyanates required for its manufacturing has caused a restriction on their use. This has triggered research on alternative insulating foam fitting the application, which include polyethylene terephthalate (PET) and polybutylene (PB-1). Within

2070-750: A suburb of the country's capital between 1964 and 1974. The Beznau Nuclear Power Plant in Switzerland has been generating electricity since 1969 and supplying district heating since 1984. The Haiyang Nuclear Power Plant in China started operating in 2018 and started supplying small scale heat to the Haiyang city area in 2020. By November 2022, the plant used 345 MW-thermal effect to heat 200,000 homes, replacing 12 coal heating plants. Recent years have seen renewed interest in small modular reactors (SMRs) and their potential to supply district heating. Speaking on

2185-433: Is fissile with thermal neutrons . Enriched uranium is a critical component for both civil nuclear power generation and military nuclear weapons . There are about 2,000  tonnes of highly enriched uranium in the world, produced mostly for nuclear power , nuclear weapons, naval propulsion , and smaller quantities for research reactors . The U remaining after enrichment is known as depleted uranium (DU), and

2300-410: Is a minor isotope contained in natural uranium (primarily as a product of alpha decay of U —because the half-life of U is much larger than that of U , it is be produced and destroyed at the same rate in a constant steady state equilibrium, bringing any sample with sufficient U content to a stable ratio of U to U over long enough timescales); during

2415-520: Is a product of nuclear fuel cycles involving nuclear reprocessing of spent fuel . RepU recovered from light water reactor (LWR) spent fuel typically contains slightly more U than natural uranium , and therefore could be used to fuel reactors that customarily use natural uranium as fuel, such as CANDU reactors . It also contains the undesirable isotope uranium-236 , which undergoes neutron capture , wasting neutrons (and requiring higher U enrichment) and creating neptunium-237 , which would be one of

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2530-679: Is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating . The heat is often obtained from a cogeneration plant burning fossil fuels or biomass , but heat-only boiler stations , geothermal heating , heat pumps and central solar heating are also used, as well as heat waste from factories and nuclear power electricity generation. District heating plants can provide higher efficiencies and better pollution control than localized boilers. According to some research, district heating with combined heat and power (CHPDH)

2645-534: Is a very effective and cheap method of uranium separation, able to be done in small facilities requiring much less energy and space than previous separation techniques. The cost of uranium enrichment using laser enrichment technologies is approximately $ 30 per SWU which is less than a third of the price of gas centrifuges, the current standard of enrichment. Separation of isotopes by laser excitation could be done in facilities virtually undetectable by satellites. More than 20 countries have worked with laser separation over

2760-440: Is approximately 100 dollars per Separative Work Units (SWU), making it about 40% cheaper than standard gaseous diffusion techniques. The Zippe-type centrifuge is an improvement on the standard gas centrifuge, the primary difference being the use of heat. The bottom of the rotating cylinder is heated, producing convection currents that move the U up the cylinder, where it can be collected by scoops. This improved centrifuge design

2875-404: Is being done that would use nuclear resonance ; however, there is no reliable evidence that any nuclear resonance processes have been scaled up to production. Gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride ( hex ) through semi-permeable membranes . This produces a slight separation between the molecules containing U and U. Throughout

2990-437: Is compressed by the primary nuclear explosion often uses HEU with enrichment between 40% and 80% along with the fusion fuel lithium deuteride . This multi-stage design enhances the efficiency and effectiveness of nuclear weapons, allowing for greater control over the release of energy during detonation. For the secondary of a large nuclear weapon, the higher critical mass of less-enriched uranium can be an advantage as it allows

3105-495: Is considerably less radioactive than even natural uranium, though still very dense. Depleted uranium is used as a radiation shielding material and for armor-penetrating weapons . Uranium as it is taken directly from the Earth is not suitable as fuel for most nuclear reactors and requires additional processes to make it usable ( CANDU design is a notable exception). Uranium is mined either underground or in an open pit depending on

3220-408: Is crucial for optimizing the economic and operational performance of uranium enrichment facilities. In addition to the separative work units provided by an enrichment facility, the other important parameter to be considered is the mass of natural uranium (NU) that is needed to yield a desired mass of enriched uranium. As with the number of SWUs, the amount of feed material required will also depend on

3335-452: Is expected to be able to cover approximately 20% of the district heating demand in Aarhus. United States Direct use geothermal district heating systems, which tap geothermal reservoirs and distribute the hot water to multiple buildings for a variety of uses, are uncommon in the United States, but have existed in America for over a century. In 1890, the first wells were drilled to access

3450-640: Is expressed in units that are so calculated as to be proportional to the total input (energy / machine operation time) and to the mass processed. Separative work is not energy. The same amount of separative work will require different amounts of energy depending on the efficiency of the separation technology. Separative work is measured in Separative work units SWU, kg SW, or kg UTA (from the German Urantrennarbeit – literally uranium separation work ). Efficient utilization of separative work

3565-593: Is extracted from seawater (from 60-foot (18 m) depth) that is 8 to 9 °C all year round, giving an average coefficient of performance (COP) of about 3.15. In the process the seawater is chilled to 4 °C; however, this resource is not used. In a district system where the chilled water could be used for air conditioning, the effective COP would be considerably higher. In the future, industrial heat pumps will be further de-carbonised by using, on one side, excess renewable electrical energy (otherwise spilled due to meeting of grid demand) from wind, solar, etc. and, on

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3680-514: Is first vaporized, and then ionized to positively charged ions. The cations are then accelerated and subsequently deflected by magnetic fields onto their respective collection targets. A production-scale mass spectrometer named the Calutron was developed during World War II that provided some of the U used for the Little Boy nuclear bomb, which was dropped over Hiroshima in 1945. Properly

3795-457: Is further processed to obtain the desired form of uranium suitable for nuclear fuel production. After the milling process is complete, the uranium must next undergo a process of conversion, "to either uranium dioxide , which can be used as the fuel for those types of reactors that do not require enriched uranium, or into uranium hexafluoride , which can be enriched to produce fuel for the majority of types of reactors". Naturally occurring uranium

3910-485: Is generally regarded as the first real district heating system. It used geothermal energy to provide heat for about 30 houses and started operation in the 14th century. The U.S. Naval Academy in Annapolis began steam district heating service in 1853. MIT began coal -fired steam district heating in 1916 when it moved to Cambridge, Massachusetts . Although these and numerous other systems have operated over

4025-419: Is generally reported to be relatively low, such as 1% (compared to 25% for supermarket cooling systems). A 30-megawatt heatpump could therefore leak (annually) around 75 kg of R134a or other working fluid. However, recent technical advances allow the use of natural heat pump refrigerants that have very low global warming potential (GWP). CO 2 refrigerant (R744, GWP=1) or ammonia (R717, GWP=0) also have

4140-518: Is hypothetically possible, but as the enrichment percentage decreases the critical mass for unmoderated fast neutrons rapidly increases, with for example, an infinite mass of 5.4% U being required. For criticality experiments, enrichment of uranium to over 97% has been accomplished. The first uranium bomb, Little Boy , dropped by the United States on Hiroshima in 1945, used 64 kilograms (141 lb) of 80% enriched uranium. Wrapping

4255-435: Is lost during manufacturing. The opposite of enriching is downblending; surplus HEU can be downblended to LEU to make it suitable for use in commercial nuclear fuel. Downblending is a key process in nuclear non-proliferation efforts, as it reduces the amount of highly enriched uranium available for potential weaponization while repurposing it for peaceful purposes. The HEU feedstock can contain unwanted uranium isotopes: U

4370-399: Is made of a mixture of U and U. The U is fissile , meaning it is easily split with neutrons while the remainder is U, but in nature, more than 99% of the extracted ore is U. Most nuclear reactors require enriched uranium, which is uranium with higher concentrations of U ranging between 3.5% and 4.5% (although a few reactor designs using a graphite or heavy water moderator , such as

4485-498: Is much wind energy or providing electricity from biomass plants when back-up power is needed. Therefore, large scale heat pumps are regarded as a key technology for smart energy systems with high shares of renewable energy up to 100% and advanced fourth generation district heating systems. A fifth generation district heating and cooling network (5GDHC), also called cold district heating , distributes heat at near ambient ground temperature: this in principle minimizes heat losses to

4600-606: Is not usable in thermal neutron reactors but can be chemically separated from spent fuel to be disposed of as waste or to be transmutated into Pu (for use in nuclear batteries ) in special reactors. Understanding and managing the isotopic composition of uranium during downblending processes is essential to ensure the quality and safety of the resulting nuclear fuel, as well as to mitigate potential radiological and proliferation risks associated with unwanted isotopes. The blendstock can be NU or DU; however, depending on feedstock quality, SEU at typically 1.5 wt% U may be used as

4715-690: Is only 1.26% lighter than U.) This problem is compounded because uranium is rarely separated in its atomic form, but instead as a compound ( UF 6 is only 0.852% lighter than UF 6 ). A cascade of identical stages produces successively higher concentrations of U. Each stage passes a slightly more concentrated product to the next stage and returns a slightly less concentrated residue to the previous stage. There are currently two generic commercial methods employed internationally for enrichment: gaseous diffusion (referred to as first generation) and gas centrifuge ( second generation), which consumes only 2% to 2.5% as much energy as gaseous diffusion. Some work

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4830-566: Is the Drammen Fjernvarme District Heating project in Norway which produces 14 MW from water at just 8 °C, industrial heat pumps are demonstrated heat sources for district heating networks. Among the ways that industrial heat pumps can be used are: Concerns have existed about the use of hydrofluorocarbons as the working fluid (refrigerant) for large heat pumps. Whilst leakage is not usually measured, it

4945-447: Is the burning of hydrocarbons . As the supply of renewable fuels is insufficient, the fossil fuels coal and gas are massively used for district heating. This burning of fossil hydrocarbons usually contributes to climate change , as the use of systems to capture and store the CO 2 instead of releasing it into the atmosphere is rare. In the case of a cogeneration plant, the heat output

5060-586: Is the cheapest method of cutting carbon emissions, and has one of the lowest carbon footprints of all fossil generation plants. District heating is ranked number 27 in Project Drawdown 's 100 solutions to global warming . District heating traces its roots to the hot water-heated baths and greenhouses of the ancient Roman Empire . A hot water distribution system in Chaudes-Aigues in France

5175-406: Is typically sized to meet half of the peak winter heat load, but over the year will provide 90% of the heat supplied. Much of the heat produced in summer will generally be wasted. The boiler capacity will be able to meet the entire heat demand unaided and can cover for breakdowns in the cogeneration plant. It is not economic to size the cogeneration plant alone to be able to meet the full heat load. In

5290-487: Is used commercially by Urenco to produce nuclear fuel and was used by Pakistan in their nuclear weapons program. Laser processes promise lower energy inputs, lower capital costs and lower tails assays, hence significant economic advantages. Several laser processes have been investigated or are under development. Separation of isotopes by laser excitation (SILEX) is well developed and is licensed for commercial operation as of 2012. Separation of isotopes by laser excitation

5405-616: The American Physical Society filed a petition with the NRC, asking that before any laser excitation plants are built that they undergo a formal review of proliferation risks. The APS even went as far as calling the technology a "game changer" due to the ability for it to be hidden from any type of detection. Aerodynamic enrichment processes include the Becker jet nozzle techniques developed by E. W. Becker and associates using

5520-556: The Cold War , gaseous diffusion played a major role as a uranium enrichment technique, and as of 2008 accounted for about 33% of enriched uranium production, but in 2011 was deemed an obsolete technology that is steadily being replaced by the later generations of technology as the diffusion plants reach their ends of life. In 2013, the Paducah facility in the U.S. ceased operating, it was the last commercial U gaseous diffusion plant in

5635-471: The Energy Impact Center 's (EIC) podcast, Titans of Nuclear , principal engineer at GE Hitachi Nuclear Energy Christer Dahlgren noted that district heating could be the impetus for the construction of new nuclear power plants in the future. EIC's own open-source SMR blueprint design, OPEN100 , could be incorporated into a district heating system. History Geothermal district heating

5750-472: The LIGA process and the vortex tube separation process. These aerodynamic separation processes depend upon diffusion driven by pressure gradients, as does the gas centrifuge. They in general have the disadvantage of requiring complex systems of cascading of individual separating elements to minimize energy consumption. In effect, aerodynamic processes can be considered as non-rotating centrifuges. Enhancement of

5865-629: The New York City steam system , that is around 2.5 GW. Germany has the largest amount of CHP in Europe. A simple thermal power station can be 20–35% efficient, whereas a more advanced facility with the ability to recover waste heat can reach total energy efficiency of nearly 80%. Some may approach 100% based on the lower heating value by condensing the flue gas as well. The heat produced by nuclear chain reactions can be injected into district heating networks. This does not contaminate

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5980-465: The RBMK and CANDU , are capable of operating with natural uranium as fuel). There are two commercial enrichment processes: gaseous diffusion and gas centrifugation . Both enrichment processes involve the use of uranium hexafluoride and produce enriched uranium oxide. Reprocessed uranium (RepU) undergoes a series of chemical and physical treatments to extract usable uranium from spent nuclear fuel. RepU

6095-534: The Royal Military College of Canada ), and the production of radioactive tracers . The main advantages are the reliability and ease of use of this design of reactor and the reproducibility of the neutron flux. Since the fuel is not modified at all for at least 20 years, the neutron spectrum in the irradiation sites does not change and the neutron flux is reproducible to about 1%. Three of the original reactors are still in operation. Although all of

6210-409: The U isotope inhibits the runaway nuclear chain reaction that is responsible for the weapon's power. The critical mass for 85% highly enriched uranium is about 50 kilograms (110 lb), which at normal density would be a sphere about 17 centimetres (6.7 in) in diameter. Later U.S. nuclear weapons usually use plutonium-239 in the primary stage, but the jacket or tamper secondary stage, which

6325-579: The chain reaction slowing down if the water heats up or forms bubbles . These characteristics are so dominant, in fact, that the SLOWPOKE-2 reactor is licensed to operate unattended overnight (but monitored remotely). Most SLOWPOKES are rated at a nominal 20 kW, although operation at higher power for shorter durations is possible. The SLOWPOKE research reactor was conceived in 1967 at the Whiteshell Laboratories of AECL. In 1970

6440-421: The thermal efficiency of cogeneration plants is significantly lower if the cooling medium is high-temperature steam, reducing electric power generation. Heat transfer oils are generally not used for district heating, although they have higher heat capacities than water, as they are expensive and have environmental issues. At customer level the heat network is usually connected to the central heating system of

6555-491: The 1930s and was built until the 1970s. It burned coal and oil, and the energy was transmitted through pressurized hot water as the heat carrier. The systems usually had supply temperatures above 100 °C, and used water pipes in concrete ducts, mostly assembled on site, and heavy equipment. A main reason for these systems was the primary energy savings, which arose from using combined heat and power plants. While also used in other countries, typical systems of this generation were

6670-580: The Netherlands, North Korea, Pakistan, Russia, the United Kingdom, and the United States. Belgium, Iran, Italy, and Spain hold an investment interest in the French Eurodif enrichment plant, with Iran's holding entitling it to 10% of the enriched uranium output. Countries that had enrichment programs in the past include Libya and South Africa, although Libya's facility was never operational. The Australian company Silex Systems has developed

6785-681: The Soviet-style district heating systems that were built after WW2 in several countries in Eastern Europe. In the 1970s the third generation was developed and was subsequently used in most of the following systems all over the world. This generation is also called the "Scandinavian district heating technology", because many of the district heating component manufacturers are based in Scandinavia. The third generation uses prefabricated, pre-insulated pipes, which are directly buried into

6900-635: The U.S. HEU Downblending Program, this HEU material, taken primarily from dismantled U.S. nuclear warheads, was recycled into low-enriched uranium (LEU) fuel, used by nuclear power plants to generate electricity. This innovative program not only facilitated the safe and secure elimination of excess weapons-grade uranium but also contributed to the sustainable operation of civilian nuclear power plants, reducing reliance on newly enriched uranium and promoting non-proliferation efforts globally The following countries are known to operate enrichment facilities: Argentina, Brazil, China, France, Germany, India, Iran, Japan,

7015-860: The West Indies and Royal Military College of Canada ). All in all, eight SLOWPOKE-2 reactors were built, seven in Canada and one in Jamaica. As of 2022, of the eight, three are operational (the ones using/converted for LEU) and five have been decommissioned. AECL also designed and built (start of construction 1985, start of operation 1987) a scaled-up version (2-10 MWth) called the SLOWPOKE Demonstration Reactor ( SDR , SLOWPOKE-3 ) for district heating at its Whiteshell Nuclear Research Establishment in Manitoba . The economics of

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7130-430: The ambient circuit is preferably controlled by heat exchange with an aquifer or another low temperature water source to remain within a temperature range from 10 °C to 25 °C. While network piping for ambient ground temperature networks is less expensive to install per pipe diameter than in earlier generations, as it does not need the same degree of insulation for the piping circuits, it has to be kept in mind that

7245-468: The amount of NU required and the number of SWUs required during enrichment change in opposite directions, if NU is cheap and enrichment services are more expensive, then the operators will typically choose to allow more U to be left in the DU stream whereas if NU is more expensive and enrichment is less so, then they would choose the opposite. When converting uranium ( hexafluoride , hex for short) to metal, 0.3%

7360-454: The benefit, depending on operating conditions, of resulting in higher heat pump efficiency than conventional refrigerants. An example is a 14 MW(thermal) district heating network in Drammen , Norway, which is supplied by seawater-source heatpumps that use R717 refrigerant, and has been operating since 2011. 90 °C water is delivered to the district loop (and returns at 65 °C). Heat

7475-788: The beryllium reflector and five sites stationed outside the reflector. Between 1976 and 1985, further seven SLOWPOKE-2 reactors with Highly Enriched Uranium (HEU) fuel were commissioned in six Canadian cities and in Kingston, Jamaica . In 1985 the first Low-Enriched Uranium (LEU) fuelled SLOWPOKE-2 reactor was commissioned at the Royal Military College of Canada (RMC) in Kingston, Ontario . Since then five SLOWPOKE-2 reactors have been decommissioned (Saskatchewan Research Council, University of Toronto, University of Alberta, Dalhousie University, and AECL / MDS Nordion reactor in Kanata ), and three converted to LEU ( Polytechnique Montreal , University of

7590-416: The blended LEU product. U is a neutron poison ; therefore the actual U concentration in the LEU product must be raised accordingly to compensate for the presence of U. While U also absorbs neutrons, it is a fertile material that is turned into fissile U upon neutron absorption . If U absorbs a neutron, the resulting short-lived U beta decays to Np , which

7705-489: The centrifugal forces is achieved by dilution of UF 6 with hydrogen or helium as a carrier gas achieving a much higher flow velocity for the gas than could be obtained using pure uranium hexafluoride. The Uranium Enrichment Corporation of South Africa (UCOR) developed and deployed the continuous Helikon vortex separation cascade for high production rate low-enrichment and the substantially different semi-batch Pelsakon low production rate high enrichment cascade both using

7820-493: The centuries, the first commercially successful district heating system was launched in Lockport , New York , in 1877 by American hydraulic engineer Birdsill Holly , considered the founder of modern district heating. Generally, all modern district heating systems are demand driven, meaning that the heat supplier reacts to the demand from the consumers and ensures that there is sufficient temperature and water pressure to deliver

7935-549: The combustion of fossil hydrocarbons. However, only a small minority of the nuclear reactors currently in operation around the world are connected to a district heating network. These reactors are in Bulgaria, China, Hungary, Romania, Russia, Slovakia, Slovenia, Switzerland and Ukraine. The Ågesta Nuclear Power Plant in Sweden was an early example of nuclear cogeneration, providing small quantities of both heat and electricity to

8050-461: The complexity and high operating costs of existing nuclear reactors. The Chalk River prototype went critical in 1970, and was moved to the University of Toronto in 1971. It had one sample site in the beryllium reflector and operated at a power level of 5 kW. In 1973 the power was increased to 20 kW and the period of unattended operation was increased from 4 hours to 18 hours. The reactor

8165-809: The core at explosion time to contain a larger amount of fuel. This design strategy optimizes the explosive yield and performance of advanced nuclear weapons systems. The U is not said to be fissile but still is fissionable by fast neutrons (>2 MeV) such as the ones produced during D–T fusion . HEU is also used in fast neutron reactors , whose cores require about 20% or more of fissile material, as well as in naval reactors , where it often contains at least 50% U, but typically does not exceed 90%. These specialized reactor systems rely on highly enriched uranium for their unique operational requirements, including high neutron flux and precise control over reactor dynamics. The Fermi-1 commercial fast reactor prototype used HEU with 26.5% U. Significant quantities of HEU are used in

8280-471: The demanded heat to the users. The five generations have defining features that sets them apart from the prior generations. The feature of each generation can be used to give an indication of the development status of an existing district heating system. The first generation was a steam-based system fueled by coal and was first introduced in the US in the 1880s and became popular in some European countries, too. It

8395-410: The depth at which it is found. After the uranium ore is mined, it must go through a milling process to extract the uranium from the ore. This is accomplished by a combination of chemical processes with the end product being concentrated uranium oxide, which is known as " yellowcake ", contains roughly 80% uranium whereas the original ore typically contains as little as 0.1% uranium. This yellowcake

8510-670: The distinguishing feature is a unique access to an abandoned water-filled coal mine within the city boundary that provides a stable heat source for the system. A fifth generation network ("Balanced Energy Network", BEN) was installed in 2016 at two large buildings of the London South Bank University as a research and development project. District heating networks exploit various energy sources, sometimes indirectly through multipurpose infrastructure such as combined heat and power plants (CHP, also called co-generation). The most used energy source for district heating

8625-966: The district heating by providing high flexibility to the electricity system. According to the review by Lund et al. those systems have to have the following abilities: Compared to the previous generations the temperature levels have been reduced to increase the energy efficiency of the system, with supply side temperatures of 70 °C and lower. Potential heat sources are waste heat from industry, CHP plants burning waste, biomass power plants , geothermal and solar thermal energy (central solar heating), large scale heat pumps , waste heat from cooling purposes and data centers and other sustainable energy sources. With those energy sources and large scale thermal energy storage , including seasonal thermal energy storage , fourth generation district heating systems are expected to provide flexibility for balancing wind and solar power generation, for example by using heat pumps to integrate surplus electric power as heat when there

8740-497: The district pipes with radioactive elements, as the heat is transferred to the network through heat exchangers . It is not technically necessary for the nuclear reactor to be very close to the district heating network, as heat can be transported over significant distances (exceeding 200 km) with affordable losses, using insulated pipes . Since nuclear reactors do not significantly contribute to either air pollution or global warming , they can be an advantageous alternative to

8855-484: The dwellings via heat exchangers (heat substations): the working fluids of both networks (generally water or steam) do not mix. However, direct connection is used in the Odense system. Typical annual loss of thermal energy through distribution is around 10%, as seen in Norway's district heating network. The amount of heat provided to customers is often recorded with a heat meter to encourage conservation and maximize

8970-734: The electrical production having much higher rates of return than heat production, whilst storing the excess heat production. It also allows solar heat to be collected in summer and redistributed off season in very large but relatively low-cost in-ground insulated reservoirs or borehole systems. The expected heat loss at the 203,000m³ insulated pond in Vojens is about 8%. With European countries such as Germany and Denmark moving to very high levels (80% and 100% respectively by 2050) of renewable energy for all energy uses there will be increasing periods of excess production of renewable electrical energy. Heat pumps can take advantage of this surplus of cheap electricity to store heat for later use. Such coupling of

9085-540: The electricity sector with the heating sector ( Power-to-X ) is regarded as a key factor for energy systems with high shares of renewable energy. After generation, the heat is distributed to the customer via a network of insulated pipes. District heating systems consist of feed and return lines. Usually the pipes are installed underground but there are also systems with overground pipes. The DH system's start-up and shut downs, as well as fluctuations on heat demand and ambient temperature, induce thermal and mechanical cycling on

9200-473: The energy mix. For example, Paris has been using geothermal heating from a 55–70 °C source 1–2 km below the surface for domestic heating since the 1970s. Currently, the fourth generation is being developed, with the transition to fourth generation already in process in Denmark . The fourth generation is designed to combat climate change and integrate high shares of variable renewable energy into

9315-468: The enriched stream to contain 3.6% U (as compared to 0.7% in NU) while the depleted stream contains 0.2% to 0.3% U. In order to produce one kilogram of this LEU it would require approximately 8 kilograms of NU and 4.5 SWU if the DU stream was allowed to have 0.3% U. On the other hand, if the depleted stream had only 0.2% U, then it would require just 6.7 kilograms of NU, but nearly 5.7 SWU of enrichment. Because

9430-621: The enrichment process, its concentration increases but remains well below 1%. High concentrations of U are a byproduct from irradiation in a reactor and may be contained in the HEU, depending on its manufacturing history. U is produced primarily when U absorbs a neutron and does not fission. The production of U is thus unavoidable in any thermal neutron reactor with U fuel. HEU reprocessed from nuclear weapons material production reactors (with an U assay of approximately 50%) may contain U concentrations as high as 25%, resulting in concentrations of approximately 1.5% in

9545-442: The exact figure is classified. In August, 2011 Global Laser Enrichment, a subsidiary of GEH, applied to the U.S. Nuclear Regulatory Commission (NRC) for a permit to build a commercial plant. In September 2012, the NRC issued a license for GEH to build and operate a commercial SILEX enrichment plant, although the company had not yet decided whether the project would be profitable enough to begin construction, and despite concerns that

9660-421: The ground and operates with lower temperatures, usually below 100 °C. A primary motivation for building these systems was security of supply by improving the energy efficiency after the two oil crises led to disruption of the oil supply. Therefore, those systems usually used coal, biomass and waste as energy sources, in preference to oil. In some systems, geothermal energy and solar energy are also used in

9775-450: The ground and reduces the need for extensive insulation. Each building on the network uses a heat pump in its own plant room to extract heat from the ambient circuit when it needs heat, and uses the same heat pump in reverse to reject heat when it needs cooling. In periods of simultaneous cooling and heating demands this allows waste heat from cooling to be used in heat pumps at those buildings which need heating. The overall temperature within

9890-466: The individualization of the heat generation. This critical system has a significant impact when comparing the efficiencies between the different generations, as the individualization of the heat generation moves the comparison from being a simple distribution system efficiency comparison to a supply system efficiency comparison, where both the heat generation efficiency as well as the distribution system efficiency needs to be included. A modern building with

10005-408: The level of enrichment desired and upon the amount of U that ends up in the depleted uranium. However, unlike the number of SWUs required during enrichment, which increases with decreasing levels of U in the depleted stream, the amount of NU needed will decrease with decreasing levels of U that end up in the DU. For example, in the enrichment of LEU for use in a light water reactor it is typical for

10120-550: The license given to SILEX over nuclear proliferation concerns. It has also been claimed that Israel has a uranium enrichment program housed at the Negev Nuclear Research Center site near Dimona . During the Manhattan Project , weapons-grade highly enriched uranium was given the codename oralloy , a shortened version of Oak Ridge alloy, after the location of the plants where the uranium

10235-430: The lower temperature difference of the pipe network leads to significantly larger pipe diameters than in prior generations. Due to the requirement of each connected building in the fifth generation district heating and cooling systems to have their own heat pump the system can be used both as a heat source or a heat sink for the heat pump, depending on if it is operated in a heating and cooling mode. As with prior generations

10350-435: The more mobile and troublesome radionuclides in deep geological repository disposal of nuclear waste. Reprocessed uranium often carries traces of other transuranic elements and fission products, necessitating careful monitoring and management during fuel fabrication and reactor operation. Low-enriched uranium (LEU) has a lower than 20% concentration of U; for instance, in commercial LWR, the most prevalent power reactors in

10465-655: The nuclear fuel cycle. A major downblending undertaking called the Megatons to Megawatts Program converts ex-Soviet weapons-grade HEU to fuel for U.S. commercial power reactors. From 1995 through mid-2005, 250 tonnes of high-enriched uranium (enough for 10,000 warheads) was recycled into low-enriched uranium. The goal is to recycle 500 tonnes by 2013. The decommissioning programme of Russian nuclear warheads accounted for about 13% of total world requirement for enriched uranium leading up to 2008. This ambitious initiative not only addresses nuclear disarmament goals but also serves as

10580-431: The number of customers which can be served, but such meters are expensive. Due to the expense of heat metering, an alternative approach is simply to meter the water – water meters are much cheaper than heat meters, and have the advantage of encouraging consumers to extract as much heat as possible, leading to a very low return temperature, which increases the efficiency of power generation. Many systems were installed under

10695-399: The other side, by making more of renewable heat sources (lake and ocean heat, geothermal, etc.). Furthermore, higher efficiency can be expected through operation on the high voltage network. Increasingly large heat stores are being used with district heating networks to maximise efficiency and financial returns. This allows cogeneration units to be run at times of maximum electrical tariff,

10810-455: The past two decades, the most notable of these countries being Iran and North Korea, though all countries have had very limited success up to this point. Atomic vapor laser isotope separation employs specially tuned lasers to separate isotopes of uranium using selective ionization of hyperfine transitions . The technique uses lasers tuned to frequencies that ionize U atoms and no others. The positively charged U ions are then attracted to

10925-399: The percent composition of uranium-235 (written U) has been increased through the process of isotope separation . Naturally occurring uranium is composed of three major isotopes: uranium-238 ( U with 99.2732–99.2752% natural abundance ), uranium-235 ( U, 0.7198–0.7210%), and uranium-234 ( U, 0.0049–0.0059%). U is the only nuclide existing in nature (in any appreciable amount) that

11040-414: The pipe network is an infrastructure that in principle provides an open access for various low temperature heat sources, such as ambient heat, ambient water from rivers, lakes, sea, or lagoons, and waste heat from industrial or commercial sources. Based on the above description it is clear that there is a fundamental difference between the 5GDHC and the prior generations of district heating, particularly in

11155-517: The pipes due to the thermal expansion. The axial expansion of the pipes is partially counteracted by frictional forces acting between the ground and the casing, with the shear stresses transferred through the PU foam bond. Therefore, the use of pre- insulated pipes has simplified the laying methods, employing cold laying instead of expansion facilities like compensators or U-bends, being so more cost effective. Pre-insulated pipes sandwich assembly composed of

11270-494: The production of medical isotopes , for example molybdenum-99 for technetium-99m generators . The medical industry benefits from the unique properties of highly enriched uranium, which enable the efficient production of critical isotopes essential for diagnostic imaging and therapeutic applications Isotope separation is difficult because two isotopes of the same element have nearly identical chemical properties, and can only be separated gradually using small mass differences. ( U

11385-432: The same separation than the older gaseous diffusion process, which it has largely replaced and so is the current method of choice and is termed second generation . It has a separation factor per stage of 1.3 relative to gaseous diffusion of 1.005, which translates to about one-fiftieth of the energy requirements. Gas centrifuge techniques produce close to 100% of the world's enriched uranium. The cost per separative work unit

11500-399: The system heat storage units may be installed to even out peak load demands. The common medium used for heat distribution is water or superheated water , but steam is also used. The advantage of steam is that in addition to heating purposes it can be used in industrial processes due to its higher temperature. The disadvantage of steam is a higher heat loss due to the high temperature. Also,

11615-473: The technical goals of this reactor were achieved, the lack of foreign sales was disappointing. Two of the SLOWPOKE/SLOWPOKE-1 reactors (out of 2 built), five of the SLOWPOKE-2 reactors (out of 8 built) and the single SLOWPOKE-3 reactor (out of 1 built) have been decommissioned. No SLOWPOKE-4 reactor was ever built. Enriched uranium Enriched uranium is a type of uranium in which

11730-457: The technology could contribute to nuclear proliferation . The fear of nuclear proliferation arose in part due to laser separation technology requiring less than 25% of the space of typical separation techniques, as well as requiring only the energy that would power 12 typical houses, putting a laser separation plant that works by means of laser excitation well below the detection threshold of existing surveillance technologies. Due to these concerns

11845-486: The technology, GE Hitachi Nuclear Energy (GEH) signed a commercialization agreement with Silex Systems in 2006. GEH has since built a demonstration test loop and announced plans to build an initial commercial facility. Details of the process are classified and restricted by intergovernmental agreements between United States, Australia, and the commercial entities. SILEX has been projected to be an order of magnitude more efficient than existing production techniques but again,

11960-510: The term 'Calutron' applies to a multistage device arranged in a large oval around a powerful electromagnet. Electromagnetic isotope separation has been largely abandoned in favour of more effective methods. One chemical process has been demonstrated to pilot plant stage but not used for production. The French CHEMEX process exploited a very slight difference in the two isotopes' propensity to change valency in oxidation/reduction , using immiscible aqueous and organic phases. An ion-exchange process

12075-621: The traditional water tank. In Alberta, Canada the Drake Landing Solar Community has achieved a world record 97% annual solar fraction for heating needs, using solar-thermal panels on the garage roofs and thermal storage in a borehole cluster. In Stockholm, the first heat pump was installed in 1977 to deliver district heating sourced from IBM servers. Today the installed capacity is about 660 MW heat, using treated sewage water, sea water, district cooling, data centers and grocery stores as heat sources. Another example

12190-557: The weapon's fissile core in a neutron reflector (which is standard on all nuclear explosives) can dramatically reduce the critical mass. Because the core was surrounded by a good neutron reflector, at explosion it comprised almost 2.5 critical masses. Neutron reflectors, compressing the fissile core via implosion, fusion boosting , and "tamping", which slows the expansion of the fissioning core with inertia, allow nuclear weapon designs that use less than what would be one bare-sphere critical mass at normal density. The presence of too much of

12305-444: The world, uranium is enriched to 3 to 5% U. Slightly enriched uranium ( SEU ) has a concentration of under 2% U. High-assay LEU (HALEU) is enriched between 5% and 20% and is called for in many small modular reactor (SMR) designs. Fresh LEU used in research reactors is usually enriched between 12% and 19.75% U; the latter concentration is used to replace HEU fuels when converting to LEU. Highly enriched uranium (HEU) has

12420-549: The world. Thermal diffusion uses the transfer of heat across a thin liquid or gas to accomplish isotope separation. The process exploits the fact that the lighter U gas molecules will diffuse toward a hot surface, and the heavier U gas molecules will diffuse toward a cold surface. The S-50 plant at Oak Ridge, Tennessee , was used during World War II to prepare feed material for the Electromagnetic isotope separation (EMIS) process, explained later in this article. It

12535-514: Was a prototype and was shut down 1984. Two reactors of SLOWPOKE aka SLOWPOKE-1 type were built. Both reactors have been decommissioned. In 1976 a next generation commercial design, named SLOWPOKE-2 (again both the name of the reactor and reactor class, further members of which were constructed elsewhere), was installed at the University of Toronto, replacing the original SLOWPOKE-1 unit (see above). The commercial model has five sample sites in

12650-424: Was abandoned in favor of gaseous diffusion. The gas centrifuge process uses a large number of rotating cylinders in series and parallel formations. Each cylinder's rotation creates a strong centripetal force so that the heavier gas molecules containing U move tangentially toward the outside of the cylinder and the lighter gas molecules rich in U collect closer to the center. It requires much less energy to achieve

12765-535: Was developed by the Asahi Chemical Company in Japan that applies similar chemistry but effects separation on a proprietary resin ion-exchange column. Plasma separation process (PSP) describes a technique that makes use of superconducting magnets and plasma physics . In this process, the principle of ion cyclotron resonance is used to selectively energize the U isotope in a plasma containing

12880-453: Was dismantled in 1976 and replaced in University of Toronto by a next generation SLOWPOKE-2 reactor. The first commercial example started construction in 1970 and was started up 14 May 1971 at AECL's Commercial Products Division in Tunney's Pasture - 20 Goldenrod Driveway, Ottawa , Ontario . It had a power output of 20 kW (thermal) and it was of the SLOWPOKE/SLOWPOKE-1 type. The reactor

12995-491: Was enriched. This covert terminology underscores the secrecy and sensitivity surrounding the production of highly enriched uranium during World War II, highlighting the strategic importance of the Manhattan Project and its role in the development of nuclear weapons. The term oralloy is still occasionally used to refer to enriched uranium. District heating District heating (also known as heat networks )

13110-467: Was state of the art until the 1930s. These systems piped very high-temperature steam through concrete ducts, and were therefore not very efficient, reliable, or safe. Nowadays, this generation is technologically outdated. However, some of these systems are still in use, for example in New York or Paris. Other systems originally built have subsequently been upgraded. The second generation was developed in

13225-568: Was used in Pompeii , and in Chaudes-Aigues since the 14th century. Denmark Denmark has one geothermal plant in operation in Thisted since 1984. Two other plants are now closed, located in Copenhagen (2005-2019), and Sønderborg (2013-2018). Both suffered issues with fine sand and blockages The country's first large-scale plant is being developed near Aarhus, and by the end of 2030, it

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