Chernobyl Nuclear Power Plant

Chernobyl Nuclear Power Plant

Chernobyl Nuclear Power Station, viewed from the roof of a building in Pripyat, Ukraine
Location of Chernobyl Nuclear Power Plant in Ukraine
Location Prypiat
Coordinates 51°23′23.47″N 30°5′38.57″E / 51.3898528°N 30.0940472°E / 51.3898528; 30.0940472Coordinates: 51°23′23.47″N 30°5′38.57″E / 51.3898528°N 30.0940472°E / 51.3898528; 30.0940472
Status Decommissioned
Construction began 15 August 1972
Commission date 1977
Decommission date ongoing since 2000
Owner(s) Government of Ukraine
Operator(s) State Agency in Administration of Exclusion Zone
Power generation
Units operational 0
Units decommissioned 4 x 1,000 MW
Nameplate capacity 4,000 MW
Average generation 0 GWh
Website
www.chnpp.gov.ua (Ukrainian)
www.chnpp.gov.ua/en/ (English)

Reactor status:

  • Reactor number 1 shutdown (1996)
  • Reactor number 2 shutdown (1991)
  • Reactor number 3 shutdown (2000)
  • Reactor number 4 destroyed in Chernobyl Disaster (1986)
  • Reactor number 5 never completed
  • Reactor number 6 never completed
Chernobyl's location in Ukraine.
Monument and the fourth reactor.

The Chernobyl Nuclear Power Plant or Chernobyl Nuclear Power Station (Ukrainian: Чорнобильська атомна електростанція, Russian: Чернобыльская АЭС) is a nuclear power station under decommissioning near the city of Pripyat, Ukraine, 14.5 km (9.0 mi) northwest of the city of Chornobyl, 16 km (9.9 mi) from the Belarus–Ukraine border, and about 110 km (68 mi) north of Kiev. Reactor No. 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. Both the zone and the former power plant are administered by the State Agency in Administration of Exclusion Zone (Ministry of Ecology and Natural Resources).

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

Construction

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 Pripyat, 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 blocks, numbered 5 and 6, of more or less the same reactor design, were planned at a site roughly a kilometer's distance from the contiguous buildings of the four older blocks. Reactor No. 5 was around 70 % complete at the time of block 4's accident and was scheduled to come online roughly six months later, on 7 November 1986. In the aftermath of the accident, the construction on No.5 and No. 6 was suspended, and eventually cancelled in April 1989, just days before the third anniversary of the 1986 explosion.[3] Reactor Nos. 3 and 4 were second generation units, whereas Nos. 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 containment structure visible in photos of the facility.[4]

Electrical systems

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.[5]

The 330 kV line is normally not used, and serves as an external power supply, connected to a station's transformer - meaning to the power plant's electrical systems. The plant is powered by its own generators, or at an event gets power from the 750 kV national grid through the main grid backup feed in transformer, or from the 330 kV level feed in grid transformer 2, or from the other power plant blocks via two reserve busbars. In case of total external power loss, the essential systems can be powered by diesel generators. Each unit's transformer is therefore connected to two 6 kV main powerline switchboards, A and B (e.g. 7A, 7B, 8A, 8B for generators 7 and 8), powering principal essential systems and connected to even another transformers at voltage 4 kV which is backed up twice (4 kV reserve busbar).[5]

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.[5]

Turbo generators

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.[6]

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.[6] 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.[7]

Reactor fleet

Four RBMK reactors were at Chernobyl Nuclear Power Plant, No. 1-4. There were two partially completed reactors, No. 5 and 6, that were cancelled in 1989 after construction was suspended for 3 years due to reactor No. 4's accident. Reactors No. 1-3 continued to operate after the accident. Reactor No. 2 was permanently shut down in 1991 after a fire broke out due to a faulty switch in a turbine.

Reactors No. 1 and 3 were eventually closed due to an agreement Ukraine made with the EU in 1995. Ukraine agreed to close the remaining units in exchange for EU assistance in modernizing the shelter over reactor No. 4 and improving the energy sector of the country, including the completion of two new nuclear reactors, Khmelnitski 2 and Rovno 4. Reactor No. 1 was shut down in 1996 with No. 3 following in 2000.[8]

Accidents

1982: Reactor No. 1 partial meltdown

On September 9, 1982, a partial core meltdown occurred in Reactor No. 1 at the Chernobyl plant. The extent of the damage was minor, but the accident was not made public until several years later. The reactor was repaired and put back into operation within a few months.[9] [10]

1986: Reactor No. 4 disaster

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 in the world. As a result, Reactor No. 4 was completely destroyed and is being enclosed in a concrete and lead sarcophagus to prevent further escape of radioactivity. Large areas of Europe were affected by the accident. The radioactive cloud spread as far away as Norway.

1991: Reactor No. 2 fire

The Chernobyl Nuclear Plant utilized one large, open turbine hall for all four reactors without any separating walls. Each reactor had two turbines. On October 11, 1991, a fire broke out in the turbine hall of Reactor No. 2.[11] The fire began in Reactor No. 2's Turbine 4 (ТГ-4 in Russian) while the turbine was being idled for repairs. A faulty switch caused a surge of current to the turbine, igniting insulating material on some electrical wiring.[12] This subsequently led to hydrogen, used as a turbine coolant, being leaked into the turbine hall "which apparently created the conditions for fire to start in the roof and for one of the trusses supporting the roof to collapse."[13] 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 No. 2.

2013 collapse

On February 13, 2013, a 600-square-metre (6,500-square-foot) portion of the roof and wall adjacent to the covered part of the turbine hall collapsed into the entombed area of the turbine hall. The collapse did not affect any other part of the Object Shelter or the New Safe Confinement. No variances in radiation levels as a result of the incident were detected.[14] The roof which collapsed was built after the Chernobyl disaster. It was later repaired.[15]

Plant shutdown and decommissioning

After the explosion at Reactor No. 4, the remaining three reactors at the power plant continued to operate. In October 1991, Reactor No. 2 caught fire, and was subsequently shut down.[16] In November 1996, Reactor No. 1 was shut down, followed by Reactor No. 3 in December 2000. The schedule for plant decommissioning is intimately wrapped with the dismantling of Reactor No. 4 and the decontamination of its environs. The Chernobyl New Safe Confinement will have equipment which will make decommissioning relatively incidental to, yet an integral part of, the cleanup of the exploded reactor. Removal of uncontaminated equipment has begun at Reactor No. 1 and this work could be complete by 2020–2022.[17]

On April 9, 2015, units 1–3 entered the decommissioning phase.[18]

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. As of 2016, the radiation exposure from that radionuclide has declined by half since the 1986 accident.

Sarcophagus replacement

Main article: New Safe Confinement
New Safe Confinement construction in 2015

Originally announced in June 2003, a new steel containment structure named the New Safe Confinement would be built to replace the aging and hastily built sarcophagus that currently protects Reactor No. 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, 240 m (787 ft) wide, 110 m (361 ft) high 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 by 2017.[19] A separate deal has been made with the American firm Holtec to build a storage facility within the exclusion zone for nuclear waste produced by Chernobyl.[20][21][22]

The shelter replacement required demolition of the recognisable 75 m (246 ft) tall exhaust chimney which was used for both Reactors No. 3 and 4. A shorter stack has been constructed adjacent to it that will be used to ventilate the new shelter. On 14 November 2016, the arch began its expected five day journey over the existing sarcophagus,[23] however, it ended up taking fifteen days and arrived at its final resting place on 29 November 2016.[24]

General Directors

See also

References

  1. ↑ "Chernobyl nuclear power plant site to be cleared by 2065". Kyiv Post. 3 January 2010. Archived from the original on October 5, 2012.
  2. ↑ library.thinkquest.org Archived May 4, 2009, at the Wayback Machine. – All four of the reactors at the Chernobyl nuclear power station were of the RBMK-type
  3. ↑ "Soviets Cancel Plans for 2 New Reactors at Chernobyl". Los Angeles Times. 21 April 1989.
  4. ↑ "Early Soviet Reactors and EU Accession". Retrieved March 10, 2016.
  5. 1 2 3 British Nuclear Energy Society (1987). Chernobyl: a technical appraisal: proceedings of the seminar organized by the British Nuclear Energy Society held in London on 3 October 1986. London: Thomas Telford Ltd. ISBN 978-0-7277-0394-1. Retrieved June 27, 2010.
  6. 1 2 "Energoatom Concern OJSC Smolensk NPP About the Plant Generation" (in Russian). Snpp.rosenergoatom.ru. April 30, 2008. Retrieved March 22, 2010.
  7. ↑ "Последняя командировка - Архив - Forum on pripyat.com". Forum.pripyat.com. Retrieved March 22, 2010.
  8. ↑ http://www.world-nuclear.org/information-library/safety-and-security/safety-of-plants/appendices/early-soviet-reactors-and-eu-accession.aspx Early Soviet Reactors and EU Accession Appendix to Safety of Nuclear Power Reactors (Updated July 2013) WNA]
  9. ↑ http://www.sbu.gov.ua/sbu/control/ru/publish/article?art_id=43297&cat_id=39895 "З архівів ВУЧК-ГПУ-НКВД-КГБ" No. 1 (16) 2001 Чорнобильська трагедія в документах та матеріалах
  10. ↑ http://www.rri.kyoto-u.ac.jp/NSRG/reports/kr139/pdf/tykhyy-2.pdf pp. 252-263
  11. ↑ "Fire Reported in Generator Area At the Chernobyl Nuclear Plant". The New York Times. October 12, 1991. Retrieved March 10, 2016.
  12. ↑ Roof fire at Chernobyl intensifies Ukrainian calls to close nuclear plant Baltimore Sun (October 13, 1991)
  13. ↑ Soviets Assure Safety at A-Plant Damaged by Fire New York Times (October 13, 1991)
  14. ↑ "Chernobyl radiation unaffected after heavy snow causes partial roof collapse, Ukrainian officials say". New York Daily press. Associated Press. February 13, 2013. Retrieved February 15, 2013.
  15. ↑ "Chernobyl roof collapses under snow". New Zealand Herald. AFP. February 14, 2013. Retrieved February 15, 2013.
  16. ↑ "Backgrounder on Chernobyl Nuclear Power Plant Accident". US Nuclear Regulatory Commission. Retrieved January 16, 2011.
  17. ↑ "Decommissioning at Chernobyl". Archived from the original on February 2, 2009. Retrieved March 10, 2016.
  18. ↑ "Chernobyl 1-3 enter decommissioning phase". Retrieved March 10, 2016.
  19. ↑ "NOVARKA and Chernobyl Project Management Unit confirm cost and time schedule for Chernobyl New Safe Confinement". European Bank. April 8, 2011. Retrieved April 22, 2012.
  20. ↑ "Chernobyl 25". Retrieved March 10, 2016.
  21. ↑ Holtec International Press Release (December 31, 2007)
  22. ↑ "New licence for Chernobyl used fuel facility". World Nuclear News. March 28, 2013. Retrieved April 2, 2013.
  23. ↑ http://www.bbc.co.uk/news/world-europe-37978482?SThisFB BBC news article
  24. ↑ http://www.ebrd.com/news/2016/unique-engineering-feat-concluded-as-chernobyl-arch-has-reached-resting-place.html
Wikimedia Commons has media related to Chernobyl Nuclear Power Plant.

News media

This article is issued from Wikipedia - version of the 12/1/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.