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69-521: The AP600 is a model of relatively small, 600 MWe nuclear power plant designed by Westinghouse Electric Company . The AP600 has passive safety features characteristic of the Generation III reactor concept. The projected core damage frequency is nearly 1000 times less than today's Nuclear Regulatory Commission (NRC) requirements, on par with plants currently being considered for construction. The design has been scaled up and improved with

138-602: A nuclear power station ( NPS ), nuclear generating station ( NGS ) or atomic power station ( APS ) is a thermal power station in which the heat source is a nuclear reactor . As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a generator that produces electricity . As of September 2023 , the International Atomic Energy Agency reported that there were 410 nuclear power reactors in operation in 32 countries around

207-537: A "demonstration PWR reactor" and consider that the "first fully commercial PWR" in the US was Yankee Rowe . Criticism centers on the fact that the Shippingport plant had not been built to commercial specifications. Consequently, the construction cost per kilowatt at Shippingport was about ten times those for a conventional power plant. In 1953, US President Dwight D. Eisenhower gave his Atoms for Peace speech to

276-465: A condenser. The condenser is a heat exchanger which is connected to a secondary side such as a river or a cooling tower . The water is then pumped back into the steam generator and the cycle begins again. The water-steam cycle corresponds to the Rankine cycle . The nuclear reactor is the heart of the station. In its central part, the reactor's core produces heat due to nuclear fission. With this heat,

345-442: A coolant is heated as it is pumped through the reactor and thereby removes the energy from the reactor. The heat from nuclear fission is used to raise steam, which runs through turbines , which in turn power the electrical generators. Nuclear reactors usually rely on uranium to fuel the chain reaction. Uranium is a very heavy metal that is abundant on Earth and is found in sea water as well as most rocks. Naturally occurring uranium

414-402: A facility has been completely decommissioned it is released from regulatory control, and the licensee of the station no longer has responsibility for its nuclear safety. Generally speaking, nuclear stations were originally designed for a life of about 30 years. Newer stations are designed for a 40 to 60-year operating life. The Centurion Reactor is a future class of nuclear reactor that

483-404: A nuclear reactor heats the reactor coolant. The coolant may be water or gas, or even liquid metal, depending on the type of reactor. The reactor coolant then goes to a steam generator and heats water to produce steam. The pressurized steam is then usually fed to a multi-stage steam turbine . After the steam turbine has expanded and partially condensed the steam, the remaining vapor is condensed in

552-683: A nuclear reactor was used to generate electricity was on December 21, 1951, at the Experimental Breeder Reactor I , powering four light bulbs. On June 27, 1954, the world's first nuclear power station to generate electricity for a power grid , the Obninsk Nuclear Power Plant , commenced operations in Obninsk , in the Soviet Union . The world's first full scale power station, Calder Hall in

621-483: A nuclear station is smaller than the fuel cost for operation of coal or gas plants. Since most of the cost of nuclear power plant is capital cost, there is almost no cost saving by running it at less than full capacity. Nuclear power plants are routinely used in load following mode on a large scale in France, although "it is generally accepted that this is not an ideal economic situation for nuclear stations". Unit A at

690-516: A number of long-established projects are struggling to find financing, notably Belene in Bulgaria and the additional reactors at Cernavodă in Romania , and some potential backers have pulled out. Where cheap gas is available and its future supply relatively secure, this also poses a major problem for nuclear projects. Analysis of the economics of nuclear power must take into account who bears

759-444: A previous goal aimed to reduce nuclear electricity generation share to lower than fifty percent by 2025, this target was postponed to 2035 in 2019 and ultimately discarded in 2023. Russia continues to export the most nuclear power plants in the world, with projects across various countries: as of July 2023, Russia was constructing 19 out of 22 reactors constructed by foreign vendors; however, some exporting projects were canceled due to

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828-523: A reactor to demonstrate the production of electricity" with Rickover "having a going organization and a reactor project under way that now had no specific use to justify it". This was accepted by Lewis Strauss and the Commission in January 1954. The acceptance of Duquesne Light as the utility partner was announced on 11 March. The ground-breaking ceremony was initiated by Eisenhower from Denver where he

897-591: A significantly different evaluation of the economics of new nuclear power stations. Following the 2011 Fukushima nuclear accident in Japan , costs are likely to go up for currently operating and new nuclear power stations, due to increased requirements for on-site spent fuel management and elevated design basis threats. However many designs, such as the currently under construction AP1000, use passive nuclear safety cooling systems, unlike those of Fukushima I which required active cooling systems, which largely eliminates

966-413: A slight decrease from the 2653 TWh produced in 2021. Thirteen countries generated at least one-quarter of their electricity from nuclear sources. Notably, France relies on nuclear energy for about 70% of its electricity needs, while Ukraine , Slovakia , Belgium , and Hungary source around half their power from nuclear. Japan , which previously depended on nuclear for over a quarter of its electricity,

1035-427: A small enough volume to become supercritical. Most reactors require continuous temperature control to prevent a core meltdown , which has occurred on a few occasions through accident or natural disaster, releasing radiation and making the surrounding area uninhabitable. Plants must be defended against theft of nuclear material and attack by enemy military planes or missiles. The most serious accidents to date have been

1104-482: A three-year research study of offshore floating nuclear power generation. In October 2022, NuScale Power and Canadian company Prodigy announced a joint project to bring a North American small modular reactor based floating plant to market. The economics of nuclear power plants is a controversial subject, and multibillion-dollar investments ride on the choice of an energy source. Nuclear power stations typically have high capital costs, but low direct fuel costs, with

1173-580: A worldwide perspective, long-term waste storage costs are uncertain. Construction, or capital cost aside, measures to mitigate global warming such as a carbon tax or carbon emissions trading , increasingly favor the economics of nuclear power. Further efficiencies are hoped to be achieved through more advanced reactor designs, Generation III reactors promise to be at least 17% more fuel efficient, and have lower capital costs, while Generation IV reactors promise further gains in fuel efficiency and significant reductions in nuclear waste. In Eastern Europe,

1242-458: Is about 1/3 of solar and 1/45 of natural gas and 1/75 of coal . Newer models, like HPR1000 , produce even less carbon dioxide during the whole operating life, as little as 1/8 of power plants using gen II reactors for 1.31g/kWh. Shippingport Atomic Power Station The reactor reached criticality on December 2, 1957, and aside from stoppages for three core changes, it remained in operation until October 1982. The first electrical power

1311-527: Is anticipated to resume similar levels of nuclear energy utilization. Over the last 15 years, the United States has seen a significant improvement in the operational performance of its nuclear power plants, enhancing their utilization and efficiency, adding the output equivalent to 19 new 1000 MWe reactors without actual construction. In France, nuclear power plants still produce over sixty percent of this country's total power generation in 2022. While

1380-503: Is being designed to last 100 years. One of the major limiting wear factors is the deterioration of the reactor's pressure vessel under the action of neutron bombardment, however in 2018 Rosatom announced it had developed a thermal annealing technique for reactor pressure vessels which ameliorates radiation damage and extends service life by between 15 and 30 years. Nuclear stations are used primarily for base load because of economic considerations. The fuel cost of operations for

1449-431: Is found in two different isotopes : uranium-238 (U-238), accounting for 99.3% and uranium-235 (U-235) accounting for about 0.7%. U-238 has 146 neutrons and U-235 has 143 neutrons. Different isotopes have different behaviors. For instance, U-235 is fissile which means that it is easily split and gives off a lot of energy making it ideal for nuclear energy. On the other hand, U-238 does not have that property despite it being

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1518-429: Is the only nuclear facility that does not use a natural body of water for cooling, instead it uses treated sewage from the greater Phoenix metropolitan area. The water coming from the cooling body of water is either pumped back to the water source at a warmer temperature or returns to a cooling tower where it either cools for more uses or evaporates into water vapor that rises out the top of the tower. The water level in

1587-632: The AP1000 . Certification testing and analysis of the AP600 and AP1000 reactor designs for Westinghouse were conducted at the APEX facility at Oregon State University . The one-quarter scale reduced pressure integral system certified the passively safe systems that cool the reactor core using gravity and natural circulation. The NRC's final design certification was received in 1999 but no orders were ever placed. A large reason Westinghouse entered development of

1656-489: The BWR , the steam is directed into the suppression chamber and condenses there. The chambers on a heat exchanger are connected to the intermediate cooling circuit. The main condenser is a large cross-flow shell and tube heat exchanger that takes wet vapor, a mixture of liquid water and steam at saturation conditions, from the turbine-generator exhaust and condenses it back into sub-cooled liquid water so it can be pumped back to

1725-496: The Russian invasion of Ukraine . Meanwhile, China continues to advance in nuclear energy: having 25 reactors under construction by late 2023, China is the country with the most reactors being built at one time in the world. Nuclear decommissioning is the dismantling of a nuclear power station and decontamination of the site to a state no longer requiring protection from radiation for the general public. The main difference from

1794-678: The UAE launched the Arab region's first-ever nuclear energy plant. Unit 1 of the Barakah plant in the Al Dhafrah region of Abu Dhabi commenced generating heat on the first day of its launch, while the remaining 3 Units are being built. However, Nuclear Consulting Group head, Paul Dorfman, warned the Gulf nation's investment into the plant as a risk "further destabilizing the volatile Gulf region, damaging

1863-657: The United Kingdom , opened on October 17, 1956 and was also meant to produce plutonium . The world's first full scale power station solely devoted to electricity production was the Shippingport Atomic Power Station in Pennsylvania , United States, which was connected to the grid on December 18, 1957. The conversion to electrical energy takes place indirectly, as in conventional thermal power stations. The fission in

1932-623: The United Nations . Commercial nuclear power generation was cornerstone of his plan. A proposal by Duquesne Light Company was accepted by Admiral Rickover and the plans for the Shippingport Atomic Power Station started. Ground was broken on Labor Day, September 6, 1954. President Eisenhower remotely initiated the first scoop of dirt at the ceremony. The reactor achieved first criticality at 4:30 AM on December 2, 1957. Sixteen days later, on December 18,

2001-424: The 1970s and 1980s, when it "reached an intensity unprecedented in the history of technology controversies," in some countries. Proponents argue that nuclear power is a sustainable energy source which reduces carbon emissions and can increase energy security if its use supplants a dependence on imported fuels. Proponents advance the notion that nuclear power produces virtually no air pollution, in contrast to

2070-485: The 1979 Three Mile Island accident , the 1986 Chernobyl disaster , and the 2011 Fukushima Daiichi nuclear disaster , corresponding to the beginning of the operation of generation II reactors . Professor of sociology Charles Perrow states that multiple and unexpected failures are built into society's complex and tightly coupled nuclear reactor systems. Such accidents are unavoidable and cannot be designed around. An interdisciplinary team from MIT has estimated that given

2139-492: The AP1000 was to improve the economies of scale that come with larger MWe plants. The more powerful AP1000 was designed to have a similar footprint but a taller containment and a power output of 1000 MWe or greater. This article about nuclear power and nuclear reactors for power generation is a stub . You can help Misplaced Pages by expanding it . Nuclear power plant A nuclear power plant ( NPP ), also known as

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2208-572: The Brussels supplementary convention, and the Vienna Convention on Civil Liability for Nuclear Damage . However states with a majority of the world's nuclear power stations, including the U.S., Russia, China and Japan, are not party to international nuclear liability conventions. The nuclear power debate about the deployment and use of nuclear fission reactors to generate electricity from nuclear fuel for civilian purposes peaked during

2277-557: The chief viable alternative of fossil fuel. Proponents also believe that nuclear power is the only viable course to achieve energy independence for most Western countries. They emphasize that the risks of storing waste are small and can be further reduced by using the latest technology in newer reactors, and the operational safety record in the Western world is excellent when compared to the other major kinds of power plants. Opponents say that nuclear power poses many threats to people and

2346-587: The construction of a reactor integrated into the utility grid. The only suitable reactor available at the time was the one that was intended for the nuclear-powered aircraft carrier desired by the Navy, but which Eisenhower had just vetoed. Kenneth Nichols of the AEC said it "became obvious" that the Rickover-Westinghouse pressurised-water reactor intended for an aircraft carrier was "the best choice for

2415-543: The core was removed and found to contain nearly 1.4% more fissile material than when it was installed, demonstrating that breeding had occurred. On October 1, 1982, the reactor ceased operations after 25 years. Dismantlement of the facility began in September 1985. In December 1988, the 956-ton (870-T) reactor pressure vessel/neutron shield tank assembly was lifted out of the containment building and loaded onto land transportation equipment in preparation for removal from

2484-493: The costs of fuel extraction, processing, use and spent fuel storage internalized costs. Therefore, comparison with other power generation methods is strongly dependent on assumptions about construction timescales and capital financing for nuclear stations. Cost estimates take into account station decommissioning and nuclear waste storage or recycling costs in the United States due to the Price Anderson Act . With

2553-424: The destruction of a turbine in operation from flying towards the reactor. In the case of a pressurized water reactor, the steam turbine is separated from the nuclear system. To detect a leak in the steam generator and thus the passage of radioactive water at an early stage, an activity meter is mounted to track the outlet steam of the steam generator. In contrast, boiling water reactors pass radioactive water through

2622-458: The dismantling of other power stations is the presence of radioactive material that requires special precautions to remove and safely relocate to a waste repository. Decommissioning involves many administrative and technical actions. It includes all clean-up of radioactivity and progressive demolition of the station. Once a facility is decommissioned, there should no longer be any danger of a radioactive accident or to any persons visiting it. After

2691-534: The energy-intensive stages of the nuclear fuel chain are considered, from uranium mining to nuclear decommissioning , nuclear power is not a low-carbon electricity source despite the possibility of refinement and long-term storage being powered by a nuclear facility. Those countries that do not contain uranium mines cannot achieve energy independence through existing nuclear power technologies. Actual construction costs often exceed estimates, and spent fuel management costs are difficult to define. On 1 August 2020,

2760-402: The environment and raising the possibility of nuclear proliferation." Nuclear power plants do not produce greenhouse gases during operation. Older nuclear power plants, like ones using second-generation reactors , produce approximately the same amount of carbon dioxide during the whole life cycle of nuclear power plants for an average of about 11g/kWh, as much power generated by wind , which

2829-775: The environment, and that costs do not justify benefits. Threats include health risks and environmental damage from uranium mining , processing and transport, the risk of nuclear weapons proliferation or sabotage, and the problem of radioactive nuclear waste . Another environmental issue is discharge of hot water into the sea. The hot water modifies the environmental conditions for marine flora and fauna. They also contend that reactors themselves are enormously complex machines where many things can and do go wrong, and there have been many serious nuclear accidents . Critics do not believe that these risks can be reduced through new technology , despite rapid advancements in containment procedures and storage methods. Opponents argue that when all

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2898-411: The environment. In addition, many reactors are equipped with a dome of concrete to protect the reactor against both internal casualties and external impacts. The purpose of the steam turbine is to convert the heat contained in steam into mechanical energy. The engine house with the steam turbine is usually structurally separated from the main reactor building. It is aligned so as to prevent debris from

2967-525: The expected growth of nuclear power from 2005 to 2055, at least four serious nuclear accidents would be expected in that period. The MIT study does not take into account improvements in safety since 1970. Nuclear power works under an insurance framework that limits or structures accident liabilities in accordance with the Paris Convention on Third Party Liability in the Field of Nuclear Energy ,

3036-431: The first electrical power was generated and full power was achieved on December 23, 1957, although the station remained in test mode. Eisenhower opened the Shippingport Atomic Power Station on May 26, 1958. The plant was built in 32 months at a cost of $ 72.5 million (equivalent to $ 786,504,739 in 2023). The type of reactor used at Shippingport was a matter of expediency. The Atomic Energy Commission urged

3105-406: The hot coolant is used as a heat source for a boiler, and the pressurized steam from that drives one or more steam turbine driven electrical generators . In the event of an emergency, safety valves can be used to prevent pipes from bursting or the reactor from exploding. The valves are designed so that they can derive all of the supplied flow rates with little increase in pressure. In the case of

3174-426: The hours over which the fixed cost of construction can be amortized. Nuclear power plants have a carbon footprint comparable to that of renewable energy such as solar farms and wind farms , and much lower than fossil fuels such as natural gas and coal . Nuclear power plants are among the safest modes of electricity generation, comparable to solar and wind power plants. The first time that heat from

3243-607: The need to spend more on redundant back up safety equipment. According to the World Nuclear Association , as of March 2020: The Russian state nuclear company Rosatom is the largest player in international nuclear power market, building nuclear plants around the world. Whereas Russian oil and gas were subject to international sanctions after the Russian full-scale invasion of Ukraine in February 2022, Rosatom

3312-483: The now decommissioned German Biblis Nuclear Power Plant was designed to modulate its output 15% per minute between 40% and 100% of its nominal power. Russia has led in the practical development of floating nuclear power stations , which can be transported to the desired location and occasionally relocated or moved for easier decommissioning. In 2022, the United States Department of Energy funded

3381-452: The power came from the seed. The first Shippingport core reactor turned out to be capable of an output of 60 MWe one month after its launch. The second core was similarly designed but more powerful, having a larger seed. The highly energetic seed required more refueling cycles than the blanket in these first two cores. The third and final core used at Shippingport was an experimental, light water moderated, thermal breeder reactor . It kept

3450-444: The power was generated in the seed. The seed was depleted quicker than the blanket, and it was replenished three times during the lifetime of the first core. Seven years later (when running on its fourth seed) the first core was retired, after having produced 1.8 billion kilowatt-hours of electricity. The second core had increased generating capacity (more than five times) and instrumentation to measure performance, but otherwise used

3519-474: The prospect that all spent nuclear fuel could potentially be recycled by using future reactors, generation IV reactors are being designed to completely close the nuclear fuel cycle . However, up to now, there has not been any actual bulk recycling of waste from a NPP, and on-site temporary storage is still being used at almost all plant sites due to construction problems for deep geological repositories . Only Finland has stable repository plans, therefore from

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3588-427: The reactor by the condensate and feedwater pumps. In the main condenser, the wet vapor turbine exhaust come into contact with thousands of tubes that have much colder water flowing through them on the other side. The cooling water typically come from a natural body of water such as a river or lake. Palo Verde Nuclear Generating Station , located in the desert about 97 kilometres (60 mi) west of Phoenix, Arizona,

3657-540: The risks of future uncertainties. To date all operating nuclear power stations were developed by state-owned or regulated utilities where many of the risks associated with construction costs, operating performance, fuel price, and other factors were borne by consumers rather than suppliers. Many countries have now liberalized the electricity market where these risks and the risk of cheaper competitors emerging before capital costs are recovered, are borne by station suppliers and operators rather than consumers, which leads to

3726-407: The same element. Different isotopes also have different half-lives . U-238 has a longer half-life than U-235, so it takes longer to decay over time. This also means that U-238 is less radioactive than U-235. Since nuclear fission creates radioactivity, the reactor core is surrounded by a protective shield. This containment absorbs radiation and prevents radioactive material from being released into

3795-537: The same seed-and-blanket design, but the seed was now uranium-233 and the blanket was made of thorium . Being a breeder reactor, it had the ability to transmute relatively inexpensive thorium to uranium-233 as part of its fuel cycle. The breeding ratio attained by Shippingport's third core was 1.01. Over its 25-year life, the Shippingport power plant operated for about 80,324 hours, producing about 7.4 billion kilowatt-hours of electricity. Owing to these peculiarities, some non-governmental sources label Shippingport

3864-401: The same seed-and-blanket design. For the second core, the seed volume was 21% of the total core volume. The second core thus required only one seed refueling. It began operating in 1965 and over the next nine years generated almost 3.5 billion kilowatt-hours of electricity. In 1974 the turbine-generator suffered mechanical failure, causing the plant to be shut down. The third and final core

3933-635: The site and shipment to a burial facility in Washington State. The site has been cleaned up and released for unrestricted use. While the Shippingport Reactor has been decommissioned, Beaver Valley Nuclear Generating Station Units 1 and 2 are still licensed and in operation at the site. The $ 98 million (1985 estimate) cleanup of Shippingport has been used as an example of a successful reactor decommissioning by proponents of nuclear power ; however, critics point out that Shippingport

4002-693: The steam generator and the nuclear reactor is controlled using the feedwater system. The feedwater pump has the task of taking the water from the condensate system, increasing the pressure and forcing it into either the steam generators—in the case of a pressurized water reactor — or directly into the reactor, for boiling water reactors . Continuous power supply to the plant is critical to ensure safe operation. Most nuclear stations require at least two distinct sources of offsite power for redundancy. These are usually provided by multiple transformers that are sufficiently separated and can receive power from multiple transmission lines. In addition, in some nuclear stations,

4071-487: The steam turbine, so the turbine is kept as part of the radiologically controlled area of the nuclear power station. The electric generator converts mechanical power supplied by the turbine into electrical power. Low-pole AC synchronous generators of high rated power are used. A cooling system removes heat from the reactor core and transports it to another area of the station, where the thermal energy can be harnessed to produce electricity or to do other useful work. Typically

4140-477: The turbine generator can power the station's loads while the station is online, without requiring external power. This is achieved via station service transformers which tap power from the generator output before they reach the step-up transformer. Nuclear power plants generate approximately 10% of global electricity, sourced from around 440 reactors worldwide. They are recognized as a significant provider of low-carbon electricity , accounting for about one-quarter of

4209-717: The use of hafnium for its control rods , although these were necessary and used only in the reactor's seed. Shippingport was created and operated under the auspices of Admiral Hyman G. Rickover , whose authority included a substantial role within the United States Atomic Energy Commission (AEC). The Shippingport reactor was designed to accommodate different cores during its lifetime; three were used. The first, installed in 1957, held 14.2 tons of natural uranium (the "blanket") and 165 pounds (75 kg) of high-enriched (93% U-235) uranium (the "seed"); despite this disparity in mass, about half

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4278-714: The vessel plus the weight of a structural steel shipping skid) and was successfully shipped by waterway for burial at the Hanford Reservation . The reactor vessel from Trojan Nuclear Power Plant (located in Oregon), was also successfully shipped by waterway to the Hanford site; a much shorter trip than the Shippingport reactor. Subsequent to Shippingport's decommissioning , three other large commercial reactors have been entirely leveled: Yankee Rowe Nuclear Power Station having been entirely decommissioned in 2007 with

4347-459: The world's supply in this category. As of 2020, nuclear power stood as the second-largest source of low-carbon energy, making up 26% of the total. Nuclear power facilities are active in 32 countries or regions, and their influence extends beyond these nations through regional transmission grids, especially in Europe. In 2022, nuclear power plants generated 2545 terawatt-hours (TWh) of electricity,

4416-402: The world, and 57 nuclear power reactors under construction. Building a nuclear power plant often spans five to ten years, which can accrue significant financial costs, depending on how the initial investments are financed. Because of this high construction cost and lower operations, maintenance, and fuel costs, nuclear plants are usually used for base load generation, because this maximizes

4485-605: Was a light water breeder, which began operating in August 1977 and after testing was brought to full power by the end of that year. It used pellets made of thorium dioxide and uranium-233 oxide; initially the U233 content of the pellets was 5-6% in the seed region, 1.5-3% in the blanket region and none in the reflector region. It operated at 236 MWt, generating 60 MWe and ultimately produced over 2.1 billion kilowatt-hours of electricity. After five years (29,000 effective full power hours)

4554-454: Was giving a talk on atomic energy on Labor Day; Rickover ensured that the unmanned bulldozer pushing dirt did not dig in and stall by having the dozer blade riding along two railroad rails buried under six inches of dirt. The origin of the project explains why the Shippingport reactor used 93%-enriched uranium, unlike later commercial power reactors that do not exceed 5% enrichment. Other significant differences from commercial reactors include

4623-477: Was not targeted by sanctions. However, some countries, especially in Europe, scaled back or cancelled planned nuclear power plants that were to be built by Rosatom. Modern nuclear reactor designs have had numerous safety improvements since the first-generation nuclear reactors. A nuclear power plant cannot explode like a nuclear weapon because the fuel for uranium reactors is not enriched enough, and nuclear weapons require precision explosives to force fuel into

4692-410: Was produced on December 18, 1957 as engineers synchronized the plant with the distribution grid of Duquesne Light Company. The first core used at Shippingport originated from a cancelled nuclear-powered aircraft carrier and used highly enriched uranium (93% U-235 ) as "seed" fuel surrounded by a "blanket" of natural U-238, in a so-called seed-and-blanket design ; in the first reactor about half

4761-552: Was smaller than most commercial nuclear power plants , most reactors in the United States are about 1,000 MWe, while Shippingport was only 60 MWe. Others argue that it was an excellent test case to prove a reactor site could be safely decommissioned and a site released for unrestricted use. Shippingport, while somewhat smaller than a large commercial reactor today, was representative, with four steam generators, pressurizer and reactor. The reactor alone, when packaged for shipment, weighed in excess of 1000 tons (921 tons weight of

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