Dungeness A Nuclear Power Station
Dungeness A
Location of Dungeness A Nuclear Power Station
Country	England
Location	Kent, South East England
Coordinates	50°54′50″N 0°57′50″E / 50.913889°N 0.963889°E / 50.913889; 0.963889Coordinates: 50°54′50″N 0°57′50″E / 50.913889°N 0.963889°E / 50.913889; 0.963889
Commission date	1965
Decommission date	2006
Operator(s)	NDA
Power station information
Primary fuel	Nuclear
grid reference TR0832016959

Dungeness B Nuclear Power Station
Dungeness B
Location of Dungeness B Nuclear Power Station
Country	England
Location	Kent, South East England
Coordinates	50°54′50″N 0°57′50″E / 50.913889°N 0.963889°E / 50.913889; 0.963889Coordinates: 50°54′50″N 0°57′50″E / 50.913889°N 0.963889°E / 50.913889; 0.963889
Commission date	1983
Operator(s)	EDF Energy
Power station information
Primary fuel	Nuclear
grid reference TR0832016959

Dungeness nuclear power station comprises a pair of nuclear power stations located on the Dungeness headland in the south east of Kent, England.

Dungeness A[link]

Dungeness A is a legacy Magnox power station, that was connected to the National Grid in 1965 and has reached the end of its life. It possessed two nuclear reactors producing 219 MW of electricity each, with a total capacity of 438 MW.^[1] The construction was undertaken by a consortium known as the Nuclear Power Group ('TNPG').^[2] The reactors were supplied by TNPG and the turbines by C. A. Parsons & Co.^[1]

On 31 December 2006 the A station ceased power generation. It is anticipated that defuelling will be completed by 2009, the turbine hall demolished in 2010 to be replaced by an intermediate level waste store in 2014. The waste store and reactor building will then be placed on a care and maintenance basis until 2103, with final site clearance and closure by 2111. Decommissioning is estimated to cost £1.2 billion. An alternative proposal has been made to accelerate cleanup for completion by 2030.

Dungeness B[link]

Dungeness B is an advanced gas-cooled reactor (AGR) power station consisting of two 615 MW reactors, which began operations in 1983 and 1985 respectively. Dungeness B was the first commercial scale AGR power station to be constructed, the design being based on the much smaller Windscale AGR prototype; the WAGR. The £89 million contract was awarded in August 1965 to Atomic Power Construction ('APC'),^[3] a consortium backed by Crompton Parkinson, Fairey Engineering, International Combustion and Richardsons Westgarth.^[2] The completion date was set as 1970.

During construction, many problems were encountered in scaling up the WAGR design. Problems with the construction of the pressure vessel liner had distorted it such that the boilers, which were to fit in an annular space between the reactor and the pressure vessel, could not be installed, and the liner had to be partially dismantled and re-built. Although the cost of this work was relatively minor at about £200,000, the cost of financing for an extra 18 unproductive months a power station costing around £100 million of which some 60 per cent was already on the ground, was massive.^[4] Serious problems with the design of the boilers, which had to withstand the pounding of hot carbon dioxide (CO₂), pressurised to 600psi and pumped around the reactor coolant circuit by massive gas circulators, were also discovered, and the casings, hangers and tube supports all had to be redesigned. The cost of these modifications, and financing during the delays, caused severe financial pressures to the consortium and its backers, and in 1969 APC collapsed into administration.

The CEGB took over project management, issued light penalties in order not to cripple Fairey and International Combustion, and appointed British Nuclear Design and Construction (BNDC) as main contractor. In 1971, problems with corrosion of mild steel components in the first generation Magnox reactors gave the designers cause for concern. The Dungeness B restraint couplings - mechanical linkages that held the graphite core in place whilst allowing it to expand and contract in response to temperature changes - were made of mild steel and could be subject to the same corrosion. A decision was made to replace them with components made from a new material.^[5] In 1972, problems with the use of galvanised wire that was used to attach thermocouples to stainless steel boiler tubes were discovered. During heat treatment of the tubes at temperatures up to 1,050^oC, the galvanising zinc diffused into the tubes and made them brittle. The cost had by then risen to £170 million.^[6] By 1975, the CEGB was reporting that the power station would not be completed until 1977 and that its cost had risen to £280 million.^[7] By 1979 the cost had risen further to £410 million.^[8] Reactor 1 first generated power on 3 April 1983, some 13 years behind schedule and at a cost of £685 million, four times the initial estimate in inflation adjusted terms.^[9]

Like the "A" station, its turbines were built by C.A. Parsons & Company^[1] and it has two 600 MWe turbo-alternator sets, producing a maximum output of 1200 MWe, though net output is 1090 MWe after the effects of house load, and downrating the reactor output due to corrosion and vibration concerns.^[10]

In March 2009 Unit B21 was brought down for maintenance; serious problems were found and the reactor was shut down for almost 18 months.^[11][12] On 24 November 2009 a small fire in the boiler annexe of Unit B22 caused the second reactor to also be shut down. Subsequently Unit B22 has been intermittently offlined for periods of up to several months. Unit B21 was restarted in August 2010.^[13][14][15] Unplanned shutdowns continued into 2011,^[16][17] with B21 down for repairs from November 2011 to March 2012.^[18]

The station's accounting closure date is 2018, 35 years after first power generation. Life-extension options may be considered prior to this date.^[19]

Consideration of Dungeness C[link]

On 15 April 2009 Dungeness was included in a list of 11 potential sites for new nuclear power stations, at the request of EDF Energy, which owns and operates Dungeness B.^[20] The government did not include Dungeness C in its draft National Policy Statement published on 9 November 2009, citing environmental reasons and concerns about coastal erosion and associated flood risk.^[21] The site was ruled out by Secretary of State for Energy and Climate Change Chris Huhne in October 2010 with the former government's list of eleven potential sites reduced to eight.^[22] Despite these environmental concerns local Conservative MP Damien Collins, supported by some local residents, has lobbied Parliament to reconsider this position. Although with the occurrence of the Fukushima nuclear disaster in Japan this seems unlikely to happen.

HVDC station[link]

From 1961 to 1984, Dungeness power station also housed the mercury arc valves of the static inverter plant converting AC into DC for transmission on HVDC Cross-Channel, the high-voltage direct current power cable carrying electric power across the English Channel to France. In 1983, a more powerful new inverter at Sellindge replaced this facility.

Ownership[link]

Both stations were originally built, owned, and operated by the Central Electricity Generating Board (CEGB). Following privatisation of the electricity supply industry and the later part-privatisation of the nuclear power generating industry they are now owned by two different companies: station A by Sellafield Ltd, part of the government-owned BNFL and station B by EDF through British subsidiary EDF Energy.

Location[link]

The stations are built on the largest area of open shingle in Europe, measuring 12 km by 6 km, which has been deposited by the sea and built up over thousands of years. The entire area is moving slowly north and east as the sea moves the shingle from one side of the ness to the other. It is surrounded by a nature reserve Site of Special Scientific Interest (SSSI). A fleet of lorries is used to continuously maintain shingle sea defences for the plant as coastal erosion would otherwise move shingle away at an estimated rate of 6 m per year. Around 30,000 cubic metres of shingle are moved each year. It seems that deposition on the north shore of the ness does not keep pace with demand. In all 90,000 cubic metres are moved each year along parts of the coast between Pett Level and Hythe. This is necessary for the safety of the entire area including the power stations. Approximately 100 million litres of cooling water are extracted and returned to the sea each hour, after being heated 12° Celsius (22 °F).

The relationship of the power stations with the ness in time is important. Geological history places the beginning of the promontory, some 3000 years ago, as shingle deposits offshore from Pett Level. From there the evidence suggests that the ness enlarged and migrated up Channel to its present position.

Importantly the ness and the coastline between Pett Level and Hythe are volatile. In recorded history Walland Marsh to the west of the power stations has been flooded.^[23] In the space of sixty years severe inundation occurred bringing the sea inland to Appledore and the original mouth of the River Rother from north of the ness at Romney to the south at Rye Harbour. The site is a few metres above Mean Sea Level and would be isolated in the event of flooding of the magnitude that submerged big areas of East Anglia and the Netherlands in 1953. Conjecture says that the ‘hurricane’ of 1987 did not bring the sea to the stations because there was a low tide at the time. It is claimed that Climate Change may cause more frequent and powerful storms (though this is unlikely) and that associated waves and surges are possible, though not probable and might increase the instability of the ness.^[23]

In the media[link]

The station was used in the filming of the British Science Fiction program Doctor Who serial The Claws of Axos in 1970.

See also[link]

• Nuclear power in the United Kingdom
• Energy policy of the United Kingdom
• Energy use and conservation in the United Kingdom

References[link]

Other sources[link]

1. Eddison, J (2000). Romney Marsh Survival on a Frontier. Tempus. ISBN 0-7524-1486-0.  Page 139 also reports the 1990 flooding mentioned above. Page 139 also reports the 1990 flooding mentioned above.
2. "Romney Marsh". http://www.romneymarsh.net.. Retrieved 5 February 2006. 
3. "Kent Against a Radioactive Environment". http://www.kare-uk.org. Retrieved 20 March 2006. 
4. "British Energy". http://british-energy.com/pagetemplate.php?pid=91.. Retrieved 16 April 2006. 
5. "industcards". http://www.industcards.com/nuclear-uk.htm.. Retrieved 16 April 2006. 
6. "Going Critical" (PDF). http://www.foe.co.uk/resource/reports/going_critical.pdf. Retrieved 16 April 2006. 

External links[link]

Wikimedia Commons has media related to: Dungeness Nuclear Power Station

• Dungeness A information pages On the BNG's Nuclear Sites web page.
• Dungeness B information page From British Energy.
• Kent Against a Radioactive Environment Local web site opposing the power stations.
• Photographs of Dungeness A From the British Nuclear Group image asset library.

v t e Electricity generation in South East England Power stations Biomass Active Didcot A (co-fires) Kingsnorth (co-fires) Slough Coal Active Didcot A Kingsnorth Closed Brighton A + B Cowes Earley Eastbourne Hastings Littlebrook A, B + C Northfleet Osney Richborough Slough Gas Active Cowes Damhead Creek Didcot B Humbly Grove Hythe Marchwood Medway Sevington Shoreham Storrington Closed Hastings Slough Proposed/Future Grain Incinerators/Waste Active Allington Quarry Basingstoke Isle of Wight Marchwood Portsmouth Slough Proposed/Future Newhaven Nuclear Active Dungeness B Closed Dungeness A Refused/Cancelled Dungeness C Oil Active Fawley Grain Kingsnorth (co-fires) Littlebrook D Closed Littlebrook A, B + C Northfleet Richborough Wind Active Green Park Kentish Flats Thanet Romney Marsh Proposed/Future London Array Southern Array (Hastings) Organisations Brighton Electric Light Company Centrica Expro International Group Hammond Electric Light Company Pre-nationalisation electric power companies SEEBOARD Southern Electric Westmill Wind Farm Co-operative

v t e Nuclear power in the United Kingdom Energy in the United Kingdom · Nuclear power Companies Current EDF Energy · Magnox Ltd · Sellafield Ltd · Urenco New build Horizon Nuclear Power · NNB Generation Company · NuGeneration Defunct British Energy · British Nuclear Fuels · British Nuclear Group · Magnox Electric · Nuclear Electric · Scottish Nuclear Organisations Civil Nuclear Constabulary · National Nuclear Laboratory · Nuclear Decommissioning Authority · Nuclear Industry Association · Nuclear Institute · Nuclear Liabilities Fund · Office for Nuclear Regulation · United Kingdom Atomic Energy Authority Reactors AGR Dungeness B · Hartlepool · Heysham 1 · Heysham 2 · Hinkley Point B · Hunterston B · Torness Magnox Active Wylfa Closed Berkeley · Bradwell · Calder Hall · Chapelcross · Dungeness A · Hinkley Point A · Hunterston A · Oldbury · Sizewell A · Trawsfynydd PWR | FBR Sizewell B  |  Dounreay Non-reactor sites Capenhurst (uranium enrichment) · Sellafield (reprocessing) · Springfields (fuel manufacture) · Winfrith (research and development) Other Anti-nuclear movement in the United Kingdom · Franco-British Nuclear Forum · Nuclear power in Scotland · Tier 1 – UK Nuclear Site Management & Licensing Category

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.

All thermal power plants produce waste heat energy as a byproduct of the useful electrical energy produced. The amount of waste heat energy equals or exceeds the amount of energy converted into useful electricity . Gas-fired power plants can achieve 50% conversion efficiency while coal and oil plants achieve around 30–49%. The waste heat produces a temperature rise in the atmosphere which is small compared to that produced by greenhouse-gas emissions from the same power plant. Natural draft wet cooling towers at many nuclear power plants and large fossil fuel-fired power plants use large hyperboloid chimney-like structures (as seen in the image at the left) that release the waste heat to the ambient atmosphere by the evaporation of water.

However, the mechanical induced-draft or forced-draft wet cooling towers in many large thermal power plants, nuclear power plants, fossil-fired power plants, petroleum refineries, petrochemical plants, geothermal, biomass and waste-to-energy plants use fans to provide air movement upward through downcoming water, and are not hyperboloid chimney-like structures. The induced or forced-draft cooling towers are typically rectangular, box-like structures filled with a material that enhances the mixing of the upflowing air and the downflowing water.^[9][10]

In areas with restricted water use, a dry cooling tower or directly air-cooled radiators may be necessary, since the cost or environmental consequences of obtaining make-up water for evaporative cooling would be prohibitive. These coolers have lower efficiency and higher energy consumption to drive fans, compared to a typical wet, evaporative cooling tower.

Where economically and environmentally possible, electric companies prefer to use cooling water from the ocean, a lake, or a river, or a cooling pond, instead of a cooling tower. This type of cooling can save the cost of a cooling tower and may have lower energy costs for pumping cooling water through the plant's heat exchangers. However, the waste heat can cause the temperature of the water to rise detectably. Power plants using natural bodies of water for cooling must be designed to prevent intake of organisms into the cooling machinery. A further environmental impact is that aquatic organisms which adapt to the warmer discharge water may be injured if the plant shuts down in cold weather.

Water consumption by power stations is a developing issue.^[11]

In recent years, recycled wastewater, or grey water, has been used in cooling towers. The Calpine Riverside and the Calpine Fox power stations in Wisconsin as well as the Calpine Mankato power station in Minnesota are among these facilities.

Other sources of energy[link]

Other power stations use the energy from wave or tidal motion, wind, sunlight or the energy of falling water, hydroelectricity. These types of energy sources are called renewable energy.

A hydroelectric dam and plant on the Muskegon river in Michigan, United States.

Hydroelectricity[link]

Dams built to produce hydroelectricity impound a reservoir of water and release it through one or more water turbines, connected to generators, and generate electricity, from the energy provided by difference in water level upstream and downstream.

Pumped storage[link]

A pumped-storage hydroelectric power plant is a net consumer of energy but can be used to smooth peaks and troughs in overall electricity demand. Pumped storage plants typically use "spare" electricity during off peak periods to pump water from a lower reservoir or dam to an upper reservoir. Because the electricity is consumed "off peak" it is typically cheaper than power at peak times. This is because the "base load" power stations, which are typically coal fired, cannot be switched on and off quickly so remain in service even when demand is low. During hours of peak demand, when the electricity price is high, the water pumped to the high reservoir is allowed to flow back to the lower reservoir through a water turbine connected to an electricity generator. Unlike coal power stations, which can take more than 12 hours to start up from cold, the hydroelectric plant can be brought into service in a few minutes, ideal to meet a peak load demand. Two substantial pumped storage schemes are in South Africa, one to the East of Cape Town (Palmiet) and one in the Drakensberg, Natal

Solar[link]

Solar energy can be turned into electricity either directly in solar cells, or in a concentrating solar power plant by focusing the light to run a heat engine.

Nellis Solar Power Plant in the United States.

A solar photovoltaic power plant converts sunlight into direct current electricity using the photoelectric effect. Inverters change the direct current into alternating current for connection to the electrical grid. This type of plant does not use rotating machines for energy conversion.

Solar thermal power plants are another type of solar power plant. They use either parabolic troughs or heliostats to direct sunlight onto a pipe containing a heat transfer fluid, such as oil. The heated oil is then used to boil water into steam, which turns a turbine that drives an electrical generator. The central tower type of solar thermal power plant uses hundreds or thousands of mirrors, depending on size, to direct sunlight onto a receiver on top of a tower. Again, the heat is used to produce steam to turn turbines that drive electrical generators.

Wind[link]

Wind turbine in front of a thermal power station in Amsterdam, the Netherlands.

Wind turbines can be used to generate electricity in areas with strong, steady winds, sometimes offshore. Many different designs have been used in the past, but almost all modern turbines being produced today use a three-bladed, upwind design. Grid-connected wind turbines now being built are much larger than the units installed during the 1970s, and so produce power more cheaply and reliably than earlier models. With larger turbines (on the order of one megawatt), the blades move more slowly than older, smaller, units, which makes them less visually distracting and safer for airborne animals.

Typical power output[link]

The power generated by a power station is measured in multiples of the watt, typically megawatts (10⁶ watts) or gigawatts (10⁹ watts). Power stations vary greatly in capacity depending on the type of power plant and on historical, geographical and economic factors. The following examples offer a sense of the scale.

Many of the largest operational onshore wind farms are located in the USA. As of 2011, the Roscoe Wind Farm is the largest onshore wind farm in the world, producing 781.5 MW of power, followed by the Horse Hollow Wind Energy Center (735.5 MW). As of November 2010, the Thanet Offshore Wind Project in United Kingdom is the largest offshore wind farm in the world at 300 MW, followed by Horns Rev II (209 MW) in Denmark.

As of April 2012, the largest photovoltaic (PV) power plants in the world are led by India's Gujarat Solar Park rated at 605 megawatts. A planned installation in China will produce 2000 megawatts at peak.^[12]

Solar thermal power stations in the U.S. have the following output:

The country's largest solar facility at Kramer Junction has an output of 354 MW

The planned Blythe Solar Power Project will produce an estimated 968 MW

Large coal-fired, nuclear, and hydroelectric power stations can generate hundreds of Megawatts to multiple Gigawatts. Some examples:

The Three Mile Island Nuclear Generating Station in the USA has a rated capacity of 802 megawatts.

The coal-fired Ratcliffe-on-Soar Power Station in the UK has a rated capacity of 2 gigawatts.

The Aswan Dam hydro-electric plant in Egypt has a capacity of 2.1 gigawatts.

The Three Gorges Dam hydro-electric plant in China will have a capacity of 22.5 gigawatts when complete; 18.2 gigawatts capacity is operating as of 2010.

Gas turbine power plants can generate tens to hundreds of megawatts. Some examples:

The Indian Queens simple-cycle peaking power station in Cornwall UK, with a single gas turbine is rated 140 megawatts.

The Medway Power Station, a combined-cycle power station in Kent, UK with two gas turbines and one steam turbine, is rated 700 megawatts.^[13]

The rated capacity of a power station is nearly the maximum electrical power that that power station can produce. Some power plants are run at almost exactly their rated capacity all the time, as a non-load-following base load power plant, except at times of scheduled or unscheduled maintenance.

However, many power plants usually produce much less power than their rated capacity.

In some cases a power plant produces much less power than its rated capacity because it uses an intermittent energy source. Operators try to pull maximum available power from such power plants, because their marginal cost is practically zero, but the available power varies widely—in particular, it may be zero during heavy storms at night.

In some cases operators deliberately produce less power for economic reasons. The cost of fuel to run a load following power plant may be relatively high, and the cost of fuel to run a peaking power plant is even higher—they have relatively high marginal costs. Operators keep power plants turned off ("operational reserve") or running at minimum fuel consumption^{[citation needed]} ("spinning reserve") most of the time. Operators feed more fuel into load following power plants only when the demand rises above what lower-cost plants (i.e., intermittent and base load plants) can produce, and then feed more fuel into peaking power plants only when the demand rises faster than the load following power plants can follow.

Operations[link]

The power station operator has several duties in the electricity-generating facility. Operators are responsible for the safety of the work crews that frequently do repairs on the mechanical and electrical equipment. They maintain the equipment with periodic inspections and log temperatures, pressures and other important information at regular intervals. Operators are responsible for starting and stopping the generators depending on need. They are able to synchronize and adjust the voltage output of the added generation with the running electrical system without upsetting the system. They must know the electrical and mechanical systems in order to troubleshoot problems in the facility and add to the reliability of the facility. Operators must be able to respond to an emergency and know the procedures in place to deal with it.

See also[link]

Energy portal

Wikimedia Commons has media related to: Power plants

• Battery-to-grid mini-power plants
• Combined heat and power
• List of thermal power station failures
• Cooling tower system
• District heating
• Electricity generation
• Environmental concerns with electricity generation
• Flue gas stacks
• Fossil fuel power station
• Geothermal power
• Relative cost of electricity generated by different sources
• Plant efficiency
• Virtual power plant

References[link]

External links[link]

• Identification System for Power Stations (KKS)
• Power station diagram
• Mechanicville Hydroelectric Power Station Tour Video
• Largest Power Plants in the World
• Power Plant Operators, Distributors, and Dispatchers (Occupational Outlook Handbook)
• Database of carbon emissions of power plants worldwide (Carbon Monitoring For Action: CARMA)