Chernobyl Nuclear Power Plant
Chernobyl Nuclear Power Station, viewed from the roof of a building in Prypiat, Ukraine
Location of Chernobyl Nuclear Power Plant
Country	Ukraine
Coordinates	51°23′22.39″N 30°05′56.93″E / 51.3895528°N 30.0991472°E / 51.3895528; 30.0991472Coordinates: 51°23′22.39″N 30°05′56.93″E / 51.3895528°N 30.0991472°E / 51.3895528; 30.0991472
Status	Not operating, still is monitored as it still contains radioactive material.
Commission date	1977
Decommission date	2000
Reactor information
Reactors operational	0 MW
Reactors decom.	4 x 1,000 MW
Reactors cancelled	2 x 1,000 MW
Power generation information
Installed capacity	4,000 MW
Annual generation	0 GW·h
Net generation	0 GW·h
Website Russian: http://www.chnpp.gov.ua/ English: http://new.chnpp.gov.ua/eng/

Chernobyl's location in the Ukraine.

The fourth reactor.

The Chernobyl Nuclear Power Plant or Chornobyl Nuclear Power Plant (Ukrainian: Чорнобильська атомна електростанція , Russian: Чернобыльская АЭС) is a decommissioned nuclear power station near the city of Pripyat, Ukraine, 18 km (11 mi) northwest of the city of Chernobyl, 16 km (9.9 mi) from the Ukraine–Belarus border, and about 110 km (68 mi) north of Kiev. Reactor 4 was the site of the Chernobyl disaster in 1986 and the power plant is now within a large restricted area known as the Chernobyl Exclusion Zone.

The nuclear power plant site is to be cleared by 2065. On January 3, 2010, a Ukrainian law stipulating a "programme" toward this objective came into effect.^[1]

Construction[link]

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The V.I. Lenin Nuclear Power Station (Russian: Чернобыльская АЭС им. В.И.Ленина) as it was known during the Soviet times, consisted of four reactors of type RBMK-1000, each capable of producing 1,000 megawatts (MW) of electric power (3.2 GW of thermal power), and the four together produced about 10% of Ukraine's electricity at the time of the accident.^[2]

The Chernobyl station is 18 km (11 mi) northwest of the city of Chernobyl, 16 km (9.9 mi) from the border of Ukraine and Belarus and about 100 km (62 mi) north of Kiev. Construction of the plant and the nearby city of Prypiat, Ukraine to house workers and their families began in 1970, with reactor No. 1 commissioned in 1977. It was the third nuclear power station in the Soviet Union of the RBMK-type (after Leningrad and Kursk), and the first ever nuclear power plant on Ukrainian soil.

The completion of the first reactor in 1977 was followed by reactor No. 2 (1978), No. 3 (1981), and No. 4 (1983). Two more reactors, nos. 5 and 6, capable of producing 1,000 MW each, were under construction at the time of the accident. Reactor No. 5 was about 70% complete at the time of the accident and was scheduled to start operating in November 7, 1986. However, the works were halted on January 1, 1988 leaving most of the machinery behind.

Units 3 and 4 were second generation units, whereas units 1 and 2 were first-generation units (like those in operation at Kursk Nuclear Power Plant). Second-generation RBMK designs were fitted with a more secure accident localization system, as can be seen in pictures. It is fortunate that the accident happened in a second-generation unit; if it had happened in a first-generation unit, it could have been even more devastating. Today, many countries that were in the Soviet Union have been paid money from the European Union to shut down such first-generation units, as they pose a threat to the environment.

Electrical systems[link]

The power plant is connected to the 330 kV and 750 kV electrical grid. The block has two electrical generators connected to the 750 kV grid by a single generator transformer. The generators are connected to their common transformer by two switches in series. Between them, the unit transformers are connected to supply power to the power plant's own systems; each generator can therefore be connected to the unit transformer to power the plant, or to the unit transformer and the generator transformer to also feed power to the grid.^[3]

The 330 kV line is normally not used, and serves as an external power supply, connected by a station transformer to the power plant's electrical systems. The plant can be powered by its own generators, or get power from the 750 kV grid through the generator transformer, or from the 330 kV grid via the station transformer, or from the other power plant block via two reserve busbars. In case of total external power loss, the essential systems can be powered by diesel generators. Each unit transformer is connected to two 6 kV main power boards, A and B (e.g. 7A, 7B, 8A, 8B for generators 7 and 8), powering principal non-essential drivers and connected to transformers for the 4 kV main power and the 4 kV reserve busbar.^[3]

The 7A, 7B, and 8B boards are also connected to the three essential power lines (namely for the coolant pumps), each also having its own diesel generator. In case of a coolant circuit failure with simultaneous loss of external power, the essential power can be supplied by the spinning down turbogenerators for about 45–50 seconds, during which time the diesel generators should start up. The generators are started automatically within 15 seconds at loss of off-site power.^[3]

Turbo generators[link]

The electrical energy is generated by a pair of 500 MW hydrogen-cooled turbo generators. These are located in the 600 m (1,969 ft)-long machine hall, adjacent to the reactor building. The turbines—the venerable five-cylinder K-500-65/3000—are supplied by the Kharkiv turbine plant; the electrical generators are the TBB-500. The turbine and the generator rotors are mounted on the same shaft; the combined weight of the rotors is almost 200 t (220 short tons) and their nominal rotational speed is 3000 rpm.^[4]

The turbo generator is 39 m (128 ft) long and its total weight is 1,200 t (1,300 short tons). The coolant flow for each turbine is 82,880 t/h. The generator produces 20 kV 50 Hz AC power. The generator's stator is cooled by water while its rotor is cooled by hydrogen. The hydrogen for the generators is manufactured on-site by electrolysis.^[4] The design and reliability of the turbines earned them the State Prize of Ukraine for 1979.

The Kharkiv turbine plant (now Turboatom) later developed a new version of the turbine, K-500-65/3000-2, in an attempt to reduce use of valuable metal. The Chernobyl plant was equipped with both types of turbines; Block 4 had the newer ones. The newer turbines, however, turned out to be more sensitive to their operating parameters, and their bearings had frequent problems with vibrations.^[5]

Accidents[link]

1982[link]

In 1982, a partial core meltdown occurred in reactor No. 1 at the Chernobyl plant. The extent of the accident was not made public until years later, in 1985. The reactor was repaired and put back into operation within months.

1986[link]

Reactor No. 4 with its enclosing sarcophagus.

On Saturday, April 26, 1986, a disaster occurred at reactor No. 4, which has been widely regarded as the worst accident in the history of nuclear power. As a result, reactor No. 4 was completely destroyed and has since been enclosed in a concrete and lead sarcophagus to prevent further escape of radiation. Large areas of Europe were affected by the accident. The radiation cloud spread as far away as Norway, in Scandinavia.

1991 fire[link]

The Chernobyl Nuclear Plant utilized one large, open turbine hall for all four reactors without any separating walls.^{[citation needed]} Each reactor had two turbines. On October 11, 1991, a fire broke out in the turbine hall of Reactor 2.^{[citation needed]} The fire began in Reactor 2's Turbine 4 (ТГ-4 in Russian) due to a hydrogen leak, causing damage to the turbine and the turbine hall roof. The adjacent reactor hall and reactor were unaffected.

Ukraine's 1991 independence from the Soviet Union generated further discussion on the Chernobyl topic, because the Rada, Ukraine's new parliament, was composed largely of young reformers. Discussions about the future of nuclear energy in Ukraine helped move the government toward the political decision to cancel the operation of Reactor 2.^{[citation needed]}

Decommissioning[link]

After the explosion at reactor four, the remaining three reactors at the power plant continued to operate. In 1991, reactor two suffered a major fire, and was subsequently decommissioned.^[6] In November 1996, reactor one was shut down, followed by reactor three on December 15, 2000, making good on a promise by Ukrainian president Leonid Kuchma that the entire plant would be closed.^[6]

Even after the last reactor shutdown, people continue to work at the Chernobyl plant until reactor units 1, 2, and 3 are totally decommissioned, which is expected to take years. The first stage of decommissioning is the removal of the highly radioactive spent nuclear fuel, which is placed in deep water cooling ponds. However, storage facilities for this are not suitable for long term containment, and those on site do not have the capacity for all the spent fuel from units 1, 2 and 3. A second facility is planned for construction that will use dry storage technology suitable for long term storage and have the required capacity.^[7]

Removal of uncontaminated equipment has begun at unit 1 and this work could be complete by 2020–2022.^[8]

The remains of reactor unit 4 will remain radioactive for some time. The isotope responsible for the majority of the external gamma radiation dose at the site is Caesium-137 which has a half-life of about 30 years. It is likely that with no further decontamination work the gamma ray dosage at the site will return to background levels in about 300 years. However, as most of the alpha emitters are longer lived, the soil and many surfaces in and around the plant are likely to be contaminated with transuranic metals such as plutonium and americium, which have much longer half-lives. It is planned that the reactor buildings will be disassembled as soon as it is radiologically safe to do so.

Sarcophagus replacement[link]

Originally announced in June of 2003, a new steel containment structure named the New Safe Confinement (NSC) would be built to replace the aging and hastily-built sarcophagus that currently protects reactor unit 4. Though the project's development has been delayed several times, construction officially began in September 2010. The New Safe Confinement is financed by an international fund managed by the European Bank for Reconstruction and Development (EBRD), is being designed and built by the French-led consortium Novarka, which includes the companies Bouygues and Vinci. Novarka is building a giant arch-shaped structure out of steel, 190 m (623 ft) wide and 200 m (656 ft) long to cover the old crumbling concrete dome that is currently in use.

This steel casing project is expected to cost $1.4 billion (£700 million, €1 billion), and expected to be completed in 2015.^[9] A separate deal has also been made with the American firm Holtec to build a storage facility within the exclusion zone for nuclear waste produced by Chernobyl.

Tours to Chernobyl[link]

The Emergency Situations Ministry of Ukraine allowed tourists to go on special tours of the plant in 2011.^[10]

See also[link]

Chernobyl articles:

• Chernobyl compared to other radioactivity releases
• Chernobyl disaster
• Chernobyl disaster effects
• Chernobyl Heart
• Cultural impact of the Chernobyl disaster
• List of Chernobyl-related articles
• List of Chernobyl-related charities
• Zone of alienation

Other accidents:

• List of civilian nuclear accidents
• List of military nuclear accidents
• Three Mile Island accident

Nuclear safety:

• International Nuclear Event Scale
• Loss-of-coolant accident
• Nuclear meltdown
• Radioactive contamination

General:

• List of nuclear reactors
• Nuclear power
• Radiotrophic fungus

References[link]

External links[link]

Wikimedia Commons has media related to: Chernobyl Nuclear Power Plant

• Chernobyl Nuclear Power Plant – official website (English)
• Chernobyl Nuclear Power Plant – official website (Ukrainian)
• Chernobyl Nuclear Power Plant at Google Maps
• Construction of the Chernobyl Nuclear Power Plant – video (Russian)
• Shut down of reactor no. 3 in December 2000 – video (Russian)
• Slide show of a visit to the Chernobyl reactor in April 2006 by a German TV team joint by Research Center Juelich
• Steel Sarcophagus Announcement.
• «Zone – virtual walk with comments» (Russian) by Nataliya Monastirnaya
• 25 years of satellite imagery over Chernobyl

A nuclear power station. The nuclear reactor is contained inside the cylindrical containment buildings to the right - left is a cooling tower venting water vapor from the non-radioactive side of the plant.

A nuclear power plant (NPP) is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity. As of February 2nd, 2012, there were 439 nuclear power plants in operation through the world.^[1]

Nuclear power plants are usually considered to be base load stations, which are best suited to constant power output.

History[link]

The control room at a U.S. nuclear power plant.

For more history, see nuclear reactor, nuclear power and nuclear fission.

Electricity was generated by a nuclear reactor for the first time ever on December 20, 1951 at the EBR-I experimental station near Arco, Idaho in the United States. On June 27, 1954, the world's first nuclear power plant to generate electricity for a power grid started operations at Obninsk, USSR.^[2] The world's first commercial scale power station, Calder Hall in England opened in October 17, 1956.^[3]

Systems[link]

BWR schematic.

Pressurised water reactor

This section has recently been translated from the German Wikipedia.

The conversion to electrical energy takes place indirectly, as in conventional thermal power plants. The heat is produced by fission in a nuclear reactor (a light water reactor). Directly or indirectly, water vapor (steam) is produced. The pressurized steam is then usually fed to a multi-stage steam turbine. Steam turbines in Western nuclear power plants are among the largest steam turbines ever. After the steam turbine has expanded and partially condensed the steam, the remaining vapor is condensed in a condenser. The condenser is a heat exchanger which is connected to secondary side such as a river or a cooling tower. The water is then pumped back into the nuclear reactor and the cycle begins again. The water-steam cycle corresponds to the Rankine cycle.

Nuclear reactors[link]

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. The most common use of nuclear reactors is for the generation of electric energy and for the propulsion of ships.

The nuclear reactor is the heart of the plant. In its central part, the reactor core's heat is generated by controlled nuclear fission. With this heat, a coolant is heated as it is pumped through the reactor and thereby removes the energy from the reactor. Heat from nuclear fission is used to raise steam, which runs through turbines, which in turn powers either ship's propellers or electrical generators.

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 the environment. In addition, many reactors are equipped with a dome of concrete to protect the reactor against external impacts.

In nuclear power plants, different types of reactors, nuclear fuels, and cooling circuits and moderators are sometimes used.

Steam turbine[link]

The object 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 to prevent debris from the destruction of a turbine in operation from flying towards the reactor.^{[citation needed]}

In the case of a pressurized water reactor, the steam turbine hermetically separated from the nuclear system. To detect a leak in the steam generator and thus the passage of radioactive water at an early stage is the outlet steam of the steam generator mounted an activity meter. In contrast, boiling water reactors and the steam turbine with radioactive water applied and therefore part of the control area of ​​the nuclear power plant.

Generator[link]

The generator converts kinetic energy supplied by the turbine into electrical energy. Low-pole AC synchronous generators of high rated power are used.

Cooling system[link]

A cooling system removes heat from the reactor core and transports it to another area of the plant, where the thermal energy can be harnessed to produce electricity or to do other useful work. Typically the hot coolant is used as a heat source for a boiler, and the pressurized steam from that boiler powers one or more steam turbine driven electrical generators.^[4]

Safety valves[link]

In the event of an emergency, two independent 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 the BWR, the steam is directed into the condensate chamber and condenses there. The chambers on a heat exchanger are connected to the intermediate cooling circuit.

This section may require cleanup to meet Wikipedia's quality standards. No cleanup reason has been specified. Please help improve this section if you can; the talk page may contain suggestions. (July 2011)

Feedwater pump[link]

The water level in the steam generator and 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 (Pressurized Water Reactor) or directly into the reactor vessel (Boiling Water Reactor).

Emergency power supply[link]

The emergency power supplies of a nuclear power plant are built up by several layers of redundancy, such as diesel generators, gas turbine generators and battery buffers. The battery backup provides uninterrupted coupling of the diesel/gas turbine units to the power supply network. If necessary, the emergency power supply allows the safe shut down of the nuclear reactor. Less important auxiliary systems such as, for example, heat tracing of pipelines are not supplied by these back ups. The majority of the required power is used to supply the feed pumps in order to cool the reactor and remove the decay heat after shut down.

People in a nuclear power plant[link]

Nuclear power plants typically employ just under a thousand people per reactor (including security guards and engineers associated with the plant but possibly working elsewhere).^{[citation needed]}

• Nuclear engineers
• Reactor operators
• Health physicists
• Emergency response team personnel
• Nuclear Regulatory Commission Resident Inspectors

In the United States and Canada, workers except for management, professional (such as engineers) and security personnel are likely to be members of either the International Brotherhood of Electrical Workers (IBEW) or the Utility Workers Union of America (UWUA), or one of the various trades and labor unions representing Machinist, laborers, boilermakers, millwrights, iron workers (etc).

Economics[link]

The economics of new nuclear power plants is a controversial subject, and multi-billion dollar investments ride on the choice of an energy source. Nuclear power plants typically have high capital costs, but low direct fuel costs (with much of the costs of fuel extraction, processing, use and long term storage externalized). Therefore, comparison with other power generation methods is strongly dependent on assumptions about construction timescales and capital financing for nuclear plants. Cost estimates also need to take into account plant decommissioning and nuclear waste storage costs. On the other hand measures to mitigate global warming, such as a carbon tax or carbon emissions trading, may favor the economics of nuclear power.

In recent years there has been a slowdown of electricity demand growth and financing has become more difficult, which has an impact on large projects such as nuclear reactors, with very large upfront costs and long project cycles which carry a large variety of risks.^[5] In Eastern Europe, a number of long-established projects are struggling to find finance, notably Belene in Bulgaria and the additional reactors at Cernavoda in Romania, and some potential backers have pulled out.^[5] Where cheap gas is available and its future supply relatively secure, this also poses a major problem for nuclear projects.^[5]

Analysis of the economics of nuclear power must take into account who bears the risks of future uncertainties. To date all operating nuclear power plants were developed by state-owned or regulated utility monopolies^[6] 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 plant suppliers and operators rather than consumers, which leads to a significantly different evaluation of the economics of new nuclear power plants.^[7]

Following the 2011 Fukushima I nuclear accidents, costs are likely to go up for currently operating and new nuclear power plants, due to increased requirements for on-site spent fuel management and elevated design basis threats.^[8]

Safety[link]

There are trades to be made between safety, economic and technical properties of different reactor designs for particular applications. Historically these decisions were often made in private by scientists, regulators and engineers, but this may be considered problematic, and since Chernobyl and Three Mile Island, many involved now consider informed consent and morality should be primary considerations.^[9]

[edit] Complexity

Nuclear power plants are some of the most sophisticated and complex energy systems ever designed.^[10] Any complex system, no matter how well it is designed and engineered, cannot be deemed failure-proof.^[11] Stephanie Cooke has said that:

The reactors themselves were enormously complex machines with an incalculable number of things that could go wrong. When that happened at Three Mile Island in 1979, another fault line in the nuclear world was exposed. One malfunction led to another, and then to a series of others, until the core of the reactor itself began to melt, and even the world's most highly trained nuclear engineers did not know how to respond. The accident revealed serious deficiencies in a system that was meant to protect public health and safety.^[12]

The 1979 Three Mile Island accident inspired Perrow's book Normal Accidents, where a nuclear accident occurs, resulting from an unanticipated interaction of multiple failures in a complex system. TMI was an example of a normal accident because it was "unexpected, incomprehensible, uncontrollable and unavoidable".^[13]

Perrow concluded that the failure at Three Mile Island was a consequence of the system's immense complexity. Such modern high-risk systems, he realized, were prone to failures however well they were managed. It was inevitable that they would eventually suffer what he termed a 'normal accident'. Therefore, he suggested, we might do better to contemplate a radical redesign, or if that was not possible, to abandon such technology entirely.^[14]

A fundamental issue related to complexity is that nuclear power systems have exceedingly long lifetimes. The timeframe involved from the start of construction of a commercial nuclear power station, through to the safe disposal of its last radioactive waste, may be 100 to 150 years.^[10]

[edit] Failure modes of nuclear power plants

There are concerns that a combination of human and mechanical error at a nuclear facility could result in significant harm to people and the environment:^[15]

Operating nuclear reactors contain large amounts of radioactive fission products which, if dispersed, can pose a direct radiation hazard, contaminate soil and vegetation, and be ingested by humans and animals. Human exposure at high enough levels can cause both short-term illness and death and longer-term death by cancer and other diseases.^[16]

It is impossible for a commercial nuclear reactor to explode like a nuclear bomb since the fuel is never sufficiently enriched for this to occur.^[17]

Nuclear reactors can fail in a variety of ways. Should the instability of the nuclear material generate unexpected behavior, it may result in an uncontrolled power excursion. Normally, the cooling system in a reactor is designed to be able to handle the excess heat this causes; however, should the reactor also experience a loss-of-coolant accident, then the fuel may melt or cause the vessel in which it is contained to overheat and melt. This event is called a nuclear meltdown.

After shutting down, for some time the reactor still needs external energy to power its cooling systems. Normally this energy is provided by the power grid to which that plant is connected, or by emergency diesel generators. Failure to provide power for the cooling systems, as happened in Fukushima I, can cause serious accidents.

Nuclear safety rules in the United States "do not adequately weigh the risk of a single event that would knock out electricity from the grid and from emergency generators, as a quake and tsunami recently did in Japan", Nuclear Regulatory Commission officials said in June 2011.^[18]

Intentional cause of such failures may be the result of nuclear terrorism.

[edit] Vulnerability of nuclear plants to attack

Nuclear reactors become preferred targets during military conflict and, over the past three decades, have been repeatedly attacked during military air strikes, occupations, invasions and campaigns:^[19]

• In September 1980, Iran bombed the Al Tuwaitha nuclear complex in Iraq.
• In June 1981, an Israeli air strike completely destroyed Iraq’s Osirak nuclear research facility.
• Between 1984 and 1987, Iraq bombed Iran’s Bushehr nuclear plant six times.
• In Iraq in 1991, the U.S. bombed three nuclear reactors and an enrichment pilot facility.
• In 1991, Iraq launched Scud missiles at Israel’s Dimona nuclear power plant.
• In September 2007, Israel bombed a Syrian reactor under construction.^[19]

In the U.S., plants are surrounded by a double row of tall fences which are electronically monitored. The plant grounds are patrolled by a sizeable force of armed guards.^[20] The NRC's "Design Basis Threat" criteria for plants is a secret, and so what size of attacking force the plants are able to protect against is unknown. However, to scram (make an emergency shutdown) a plant takes fewer than 5 seconds while unimpeded restart takes hours, severely hampering a terrorist force in a goal to release radioactivity.

Attack from the air is an issue that has been highlighted since the September 11 attacks in the U.S. However, it was in 1972 when three hijackers took control of a domestic passenger flight along the east coast of the U.S. and threatened to crash the plane into a U.S. nuclear weapons plant in Oak Ridge, Tennessee. The plane got as close as 8,000 feet above the site before the hijackers’ demands were met.^[21][22]

The most important barrier against the release of radioactivity in the event of an aircraft strike on a nuclear power plant is the containment building and its missile shield. Current NRC Chairman Dale Klein has said "Nuclear power plants are inherently robust structures that our studies show provide adequate protection in a hypothetical attack by an airplane. The NRC has also taken actions that require nuclear power plant operators to be able to manage large fires or explosions—no matter what has caused them."^[23]

In addition, supporters point to large studies carried out by the U.S. Electric Power Research Institute that tested the robustness of both reactor and waste fuel storage and found that they should be able to sustain a terrorist attack comparable to the September 11 terrorist attacks in the U.S. Spent fuel is usually housed inside the plant's "protected zone"^[24] or a spent nuclear fuel shipping cask; stealing it for use in a "dirty bomb" is extremely difficult. Exposure to the intense radiation would almost certainly quickly incapacitate or kill anyone who attempts to do so.^[25]

[edit] Plant location

Fort Calhoun Nuclear Generating Station surrounded by the 2011 Missouri River Floods on June 16, 2011

In many countries, plants are often located on the coast, in order to provide a ready source of cooling water for the essential service water system. As a consequence the design needs to take the risk of flooding and tsunamis into account. The World Energy Council (WEC) argues disaster risks are changing and increasing the likelihood of disasters such as earthquakes, cyclones, hurricanes, typhoons, flooding.^[26] Climate change and increased temperatures, lower precipitation levels and an increase in the frequency and severity of droughts may lead to fresh water shortages.^[26] Seawater is corrosive and so nuclear energy supply is likely to be negatively affected by the fresh water shortage.^[26] This generic problem may become increasingly significant over time.^[26] Failure to calculate the risk of flooding correctly lead to a Level 2 event on the International Nuclear Event Scale during the 1999 Blayais Nuclear Power Plant flood,^[27] while flooding caused by the 2011 Tōhoku earthquake and tsunami lead to the Fukushima I nuclear accidents.^[28]

The design of plants located in seismically active zones also requires the risk of earthquakes and tsunamis to be taken into account. Japan, India, China and the USA are among the countries to have plants in earthquake-prone regions. Damage caused to Japan's Kashiwazaki-Kariwa Nuclear Power Plant during the 2007 Chūetsu offshore earthquake^[29][30] underlined concerns expressed by experts in Japan prior to the Fukushima accidents, who have warned of a genpatsu-shinsai (domino-effect nuclear power plant earthquake disaster).^[31]

[edit] Multiple reactors

The Fukushima nuclear disaster illustrated the dangers of building multiple nuclear reactor units close to one another. This proximity triggered the parallel, chain-reaction accidents that led to hydrogen explosions damaging reactor buildings and water draining from open-air spent fuel pools -- a situation that was potentially more dangerous than the loss of reactor cooling itself. Because of the closeness of the reactors, Plant Director Masao Yoshida "was put in the position of trying to cope simultaneously with core meltdowns at three reactors and exposed fuel pools at three units".^[32]

[edit] Nuclear safety systems

The three primary objectives of nuclear safety systems as defined by the Nuclear Regulatory Commission are to shut down the reactor, maintain it in a shutdown condition, and prevent the release of radioactive material during events and accidents.^[33] These objectives are accomplished using a variety of equipment, which is part of different systems, of which each performs specific functions.

[edit] Routine emissions of radioactive materials

During everyday routine operations, emissions of radioactive materials from nuclear plants are released to the outside of the plants although they are quite slight amounts.^{[34][35][36][37]} The daily emissions go into the air, water and soil.^[35][36]

NRC says, "nuclear power plants sometimes release radioactive gases and liquids into the environment under controlled, monitored conditions to ensure that they pose no danger to the public or the environment",^[38] and "routine emissions during normal operation of a nuclear power plant are never lethal".^[39]

According to the United Nations (UNSCEAR), regular nuclear power plant operation including the nuclear fuel cycle amounts to 0.0002 mSv (milli-Sievert) annually in average public radiation exposure; the legacy of the Chernobyl disaster is 0.002 mSv/yr as a global average as of a 2008 report; and natural radiation exposure averages 2.4 mSv annually although frequently varying depending on an individual's location from 1 to 13 mSv.^[40]

[edit] The myth of absolute safety

The nuclear industry, particularly in Japan, has felt a need to tell the public that nuclear power is safe in some absolute way.^[41] Many government agencies and nuclear companies have promoted a public myth of "absolute safety" that nuclear power proponents had nurtured over decades. The tsunami that began the Fukushima nuclear disaster could and should have been anticipated^{[42][verification needed]} and in March 2012, Prime Minister Yoshihiko Noda acknowledged that the Japanese government shared the blame for the Fukushima disaster, saying that officials had been blinded to the country's "technological infallibility", and were all too steeped in a "safety myth".^[43]

In Japan, a national program to develop robots for use in nuclear emergencies was terminated in midstream because it "smacked too much of underlying danger". Japan, supposedly a major power in robotics, had none to send in to Fukushima during the disaster. Similarly, Japan’s Nuclear Safety Commission stipulated in its safety guidelines for light-water nuclear facilities that “the potential for extended loss of power need not be considered.” But such an extended loss of power contributed to the meltdown at the Fukushima nuclear facilities.^[44]

Controversy[link]

The abandoned city of Prypiat, Ukraine, following the Chernobyl disaster. The Chernobyl nuclear power plant is in the background.

The nuclear power debate is about the controversy^{[45][46][47][48]} which has surrounded the deployment and use of nuclear fission reactors to generate electricity from nuclear fuel for civilian purposes. The debate about nuclear power peaked during the 1970s and 1980s, when it "reached an intensity unprecedented in the history of technology controversies", in some countries.^[49][50]

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.^[51] Proponents advance the notion that nuclear power produces virtually no air pollution, in contrast to 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.^[52]

Opponents say that nuclear power poses many threats to people and the environment. These threats include health risks and environmental damage from uranium mining, processing and transport, the risk of nuclear weapons proliferation or sabotage, and the unsolved problem of radioactive nuclear waste.^[53][54][55] 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.^[56][57] Critics do not believe that these risks can be reduced through new technology.^[58] They argue that when all 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.^[59][60][61]

Reprocessing[link]

Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel.^[62] Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing nuclear weapons. With the commercialization of nuclear power, the reprocessed plutonium was recycled back into MOX nuclear fuel for thermal reactors.^[63] The reprocessed uranium, which constitutes the bulk of the spent fuel material, can in principle also be re-used as fuel, but that is only economic when uranium prices are high. Finally, the breeder reactor can employ not only the recycled plutonium and uranium in spent fuel, but all the actinides, closing the nuclear fuel cycle and potentially multiplying the energy extracted from natural uranium by more than 60 times.^[64]

Nuclear reprocessing reduces the volume of high-level waste, but by itself does not reduce radioactivity or heat generation and therefore does not eliminate the need for a geological waste repository. Reprocessing has been politically controversial because of the potential to contribute to nuclear proliferation, the potential vulnerability to nuclear terrorism, the political challenges of repository siting (a problem that applies equally to direct disposal of spent fuel), and because of its high cost compared to the once-through fuel cycle.^[65] The Obama administration stepped back from President Bush's plans for commercial-scale reprocessing and reverted to a program focused on reprocessing-related scientific research.^[66]

Accident indemnification[link]

The Vienna Convention on Civil Liability for Nuclear Damage puts in place an international framework for nuclear liability.^[67] However states with a majority of the world's nuclear power plants, including the U.S., Russia, China and Japan, are not party to international nuclear liability conventions.

In the U.S., insurance for nuclear or radiological incidents is covered (for facilities licensed through 2025) by the Price-Anderson Nuclear Industries Indemnity Act.

Under the Energy policy of the United Kingdom through its Nuclear Installations Act of 1965, liability is governed for nuclear damage for which a UK nuclear licensee is responsible. The Act requires compensation to be paid for damage up to a limit of £150 million by the liable operator for ten years after the incident. Between ten and thirty years afterwards, the Government meets this obligation. The Government is also liable for additional limited cross-border liability (about £300 million) under international conventions (Paris Convention on Third Party Liability in the Field of Nuclear Energy and Brussels Convention supplementary to the Paris Convention).^[68]

Decommissioning[link]

Nuclear decommissioning is the dismantling of a nuclear power plant and decontamination of the site to a state no longer requiring protection from radiation for the general public. The main difference from the dismantling of other power plants is the presence of radioactive material that requires special precautions.

Generally speaking, nuclear plants were designed for a life of about 30 years.^{[citation needed]} Newer plants are designed for a 40 to 60-year operating life.^{[citation needed]}

Decommissioning involves many administrative and technical actions. It includes all clean-up of radioactivity and progressive demolition of the plant. Once a facility is decommissioned, there should no longer be any danger of a radioactive accident or to any persons visiting it. After a facility has been completely decommissioned it is released from regulatory control, and the licensee of the plant no longer has responsibility for its nuclear safety.

Historic accidents[link]

The 2011 Fukushima Daiichi nuclear disaster in Japan, the worst nuclear accident in 25 years, displaced 50,000 households after radiation leaked into the air, soil and sea.^[69] Radiation checks led to bans of some shipments of vegetables and fish.^[70]

The nuclear industry says that new technology and oversight have made nuclear plants much safer, but 57 accidents have occurred since the Chernobyl disaster in 1986. Two thirds of these mishaps occurred in the US.^[71] The French Atomic Energy Agency (CEA) has concluded that technical innovation cannot eliminate the risk of human errors in nuclear plant operation.

An interdisciplinary team from MIT have estimated that given the expected growth of nuclear power from 2005–2055, at least four serious nuclear power accidents would be expected in that period.^[71]

Flexibility of nuclear power plants[link]

It is often claimed that nuclear stations are inflexible in their output, implying that other forms of energy would be required to meet peak demand. While that is true for the vast majority of reactors, this is no longer true of at least some modern designs.^[72]

Nuclear plants are routinely used in load following mode on a large scale in France.^[73] Unit A at the German Biblis Nuclear Power Plant is designed to in- and decrease its output 15 % per minute between 40 and 100 % of its nominal power.^[74] Boiling water reactors normally have load-following capability, implemented by varying the recirculation water flow.^{[citation needed]}

Future power plants[link]

A number of new designs for nuclear power generation, collectively known as the Generation IV reactors, are the subject of active research and may be used for practical power generation in the future. Many of these new designs specifically attempt to make fission reactors cleaner, safer and/or less of a risk to the proliferation of nuclear weapons. Passively safe plants (such as the ESBWR) are available to be built^[75] and other designs that are believed to be nearly fool-proof are being pursued.^[76] Fusion reactors, which may be viable in the future, diminish or eliminate many of the risks associated with nuclear fission.^[77]

The 1600 MWe European Pressurized Reactor reactor is being built in Olkiluoto, Finland. A joint effort of French AREVA and German Siemens AG, it will be the largest reactor in the world. In December 2006 construction was about 18 months behind schedule so completion was expected 2010-2011.^[78][79]

As of March 2007, there are seven nuclear power plants under construction in India, and five in China.^[80]

In November 2011 Gulf Power stated that by the end of 2012 it hopes to finish buying off 4000 acres of land north of Pensacola, Florida in order to build a possible nuclear power plant. ^[81]

Russia has begun building the world’s first floating nuclear power plant. The £100 million vessel, the Lomonosov, is the first of seven plants that Moscow says will bring vital energy resources to remote Russian regions.^[82]

By 2025, Southeast Asia nations would have a total of 29 nuclear power plants, Indonesia will have 4 nuclear power plants, Malaysia 4, Thailand 5 and Vietnam 16 from nothing at all in 2011.^[83]

See also[link]

Energy portal

Wikimedia Commons has media related to: Nuclear power plant

• List of nuclear reactors
• Nuclear power by country
• Nuclear Information and Resource Service
• Fossil-fuel power station
• Gerald W. Brown, American whistleblower on passive fire protection/circuit integrity deficiencies in US and Canadian plants
• Nuclear fuel cycle
• Containment building
• Safety engineering
• SCRAM
• FEMA
• Nuclear Regulatory Commission of the USA
• Auxiliary feedwater
• Uranium market

References[link]

External links[link]

• IPPNW - International Physicians for the Prevention of Nuclear War (Nobel Peace Prize 1985)
• MAPW - Information on Australia's research reactor
• Freeview Video 'Nuclear Power Plants - What's the Problem' A Royal Institution Lecture by John Collier by the Vega Science Trust.
• Non Destructive Testing for Nuclear Power Plants
• Web-based simple nuclear power plant game
• Uranium.Info publishing uranium price since 1968.
• Information about all NPP in the world
• U.S. plants and operators
• SCK.CEN Belgian Nuclear Research Centre in Mol.
• Civil Liability for Nuclear Damage - World Nuclear Association
• Glossary of Nuclear Terms
• Protection against Sabotage of Nuclear Facilities: Using Morphological Analysis in Revising the Design Basis Threat From the Swedish Morphological Society
• Critical Hour: Three Mile Island, The Nuclear Legacy, And National Security Online book by Albert J. Fritsch, Arthur H. Purcell, and Mary Byrd Davis (2005). Updated edition June 2006
• An Interactive VR Panorama of the cooling towers at Temelin Nuclear Power Plant, Czech Republic
• Interactive map with all nuclear power plants US and worldwide (Note: missing many plants)

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2011)

The Susquehanna Steam Electric Station, a boiling water reactor nuclear power plant.

St. Clair Power Plant, a coal-fired plant in Michigan.

The Three Gorges Dam, a hydroelectric dam.

A power station (also referred to as a generating station, power plant, or powerhouse) is an industrial facility for the generation of electric power.^[1][2][3]

At the center of nearly all power stations is a generator, a rotating machine that converts mechanical power into electrical power by creating relative motion between a magnetic field and a conductor. The energy source harnessed to turn the generator varies widely. It depends chiefly on which fuels are easily available, cheap enough and on the types of technology that the power company has access to.

Central power stations produce AC power, after a brief Battle of Currents in the 19th century demonstrated the advantages of AC distribution.

History[link]

The world's first power station was built by Sigmund Schuckert in the Bavarian town of Ettal and went into operation in 1878^[4]. The station consisted of 24 dynamo electric generators which were driven by a steam engine. It was used to illuminate a grotto in the gardens of Linderhof Palace.

The first public power station was the Edison Electric Light Station, built in London at 57, Holborn Viaduct, which started operation in January 1882. This was an initiative of Thomas Edison that was organized and managed by his partner, Edward Johnson. A Babcock and Wilcox boiler powered a 125 horsepower steam engine that drove a 27 ton generator called Jumbo, after the celebrated elephant. This supplied electricity to premises in the area that could be reached through the culverts of the viaduct without digging up the road, which was the monopoly of the gas companies. The customers included the City Temple and the Old Bailey. Another important customer was the Telegraph Office of the General Post Office but this could not be reached though the culverts. Johnson arranged for the supply cable to be run overhead, via Holborn Tavern and Newgate.^[5]

In September 1882 in New York, the Pearl Street Station was established by Edison to provide electric lighting in the lower Manhattan Island area. The station ran until destroyed by fire in 1890. The station used reciprocating steam engines to turn direct-current generators. Because of the DC distribution, the service area was small, limited by voltage drop in the feeders. The War of Currents eventually resolved in favor of AC distribution and utilization, although some DC systems persisted to the end of the 20th century. DC systems with a service radius of a mile (kilometer) or so were necessarily smaller, less efficient of fuel consumption, and more labor intensive to operate than much larger central AC generating stations.

AC systems used a wide range of frequencies depending on the type of load; lighting load using higher frequencies, and traction systems and heavy motor load systems preferring lower frequencies. The economics of central station generation improved greatly when unified light and power systems, operating at a common frequency, were developed. The same generating plant that fed large industrial loads during the day, could feed commuter railway systems during rush hour and then serve lighting load in the evening, thus improving the system load factor and reducing the cost of electrical energy overall. Many exceptions existed, generating stations were dedicated to power or light by the choice of frequency, and rotating frequency changers and rotating converters were particularly common to feed electric railway systems from the general lighting and power network.

Throughout the first few decades of the 20th century central stations became larger, using higher steam pressures to provide greater efficiency, and relying on interconnections of multiple generating stations to improve reliability and cost. High-voltage AC transmission allowed hydroelectric power to be conveniently moved from distant waterfalls to city markets. The advent of the steam turbine in central station service, around 1906, allowed great expansion of generating capacity. Generators were no longer limited by the power transmission of belts or the relatively slow speed of reciprocating engines, and could grow to enormous sizes. For example, Sebastian Ziani de Ferranti planned what would have been the largest reciprocating steam engine ever built for a proposed new central station, but scrapped the plans when turbines became available in the necessary size. Building power systems out of central stations required combinations of engineering skill and financial acumen in equal measure. Pioneers of central station generation include George Westinghouse and Samuel Insull in the United States, Ferranti and Charles Hesterman Merz in UK, and many others.

Thermal power stations[link]

Rotor of a modern steam turbine, used in power station.

In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics. Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating, the power plant is referred to as a cogeneration power plant or CHP (combined heat-and-power) plant. In countries where district heating is common, there are dedicated heat plants called heat-only boiler stations. An important class of power stations in the Middle East uses by-product heat for the desalination of water.

The efficiency of a steam turbine is limited by the maximum temperature of the steam produced and is not directly a function of the fuel used. For the same steam conditions, coal, nuclear and gas power plants all have the same theoretical efficiency. Overall, if a system is on constantly (base load) it will be more efficient than one that is used intermittently (peak load).

Besides use of reject heat for process or district heating, one way to improve overall efficiency of a power plant is to combine two different thermodynamic cycles. Most commonly, exhaust gases from a gas turbine are used to generate steam for a boiler and steam turbine. The combination of a "top" cycle and a "bottom" cycle produces higher overall efficiency than either cycle can attain alone.

Classification[link]

CHP plant in Warsaw, Poland.

Geothermal power station in Iceland.

Coal Power Station in Tampa, United States.

Thermal power plants are classified by the type of fuel and the type of prime mover installed.

By fuel[link]

• Fossil fuelled power plants may also use a steam turbine generator or in the case of natural gas-fired plants may use a combustion turbine. A coal-fired power station produces electricity by burning coal to generate steam, and has the side-effect of producing large amounts of sulfur dioxide which pollutes air and water and carbon dioxide, which contributes to global warming. About 50% of electric generation in the USA is produced by coal-fired power plants
• Nuclear power plants^[6] use a nuclear reactor's heat to operate a steam turbine generator. About 20% of electric generation in the USA is produced by nuclear power plants.
• Geothermal power plants use steam extracted from hot underground rocks.
• Biomass-fuelled power plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.
• In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-density, fuel.
• Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.
• Solar thermal electric plants use sunlight to boil water and produce steam which turns the generator.

By prime mover[link]

• Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system. About 90% of all electric power produced in the world is by use of steam turbines.^[7]
• Gas turbine plants use the dynamic pressure from flowing gases (air and combustion products) to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants. These may be comparatively small units, and sometimes completely unmanned, being remotely operated. This type was pioneered by the UK, Princetown^[8] being the world's first, commissioned in 1959.
• Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the hot exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new baseload power plants are combined cycle plants fired by natural gas.
• Internal combustion reciprocating engines are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, natural gas, and landfill gas.
• Microturbines, Stirling engine and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.

Cooling towers[link]

Cooling towers evaporating water at Ratcliffe-on-Soar Power Station, United Kingdom.