Kozloduy Nuclear Power Plant

Coordinates: 43°44′46″N 23°46′14″E / 43.74611°N 23.77056°E / 43.74611; 23.77056
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Kozloduy Nuclear Power Plant
"АЕЦ Козлодуй".jpeg
Coordinates43°44′46″N 23°46′14″E / 43.74611°N 23.77056°E / 43.74611; 23.77056
Construction began1970
Commission date28 October 1974 (28 October 1974)
1974 (Unit 1)
1975 (Unit 2)
1980 (Unit 3)
1982 (Unit 4)
1987 (Unit 5)
1991 (Unit 6)
Decommission date2004 (Units 1 & 2)
2007 (Units 3 & 4)
Nuclear power station
Reactor typeVVER-440
Thermal capacity2 x 3,120 MWth
Power generation
Units operational2 x 1088 MWe (gross)
Units planned1 x 1,250 MWe[1]
Units decommissioned4 x 440 MWe (gross)
Nameplate capacity2,176 MW
Capacity factor87.2% (2014-2018)
Annual net output16,023 GW·h
External links
CommonsRelated media on Commons

The Kozloduy Nuclear Power Plant is a nuclear power plant in Bulgaria situated 180 kilometres (110 mi) north of Sofia and 5 kilometres (3.1 mi) east of Kozloduy, a town on the Danube river, near the border with Romania. It is the country's only nuclear power plant and the largest in the region. The construction of the first reactor began on 6 April 1970.[2]

Kozloduy NPP currently manages two pressurized water reactors with a total gross output of 2000 MWe and 1966 MW net. Units 5 and 6, constructed in 1987 and 1991 respectively, are VVER-1000 reactors. By 2017 Unit 5 was to be upgraded to reach a capacity of 1,100 MWe, as part of a programme to extend the life of the unit by 30 years.[3] A seventh 1,000 MW unit may be installed, using parts from the terminated Belene project for which Bulgaria has paid 600 M EUR.[4][5] An eighth unit is also under consideration.[6]

The older and smaller Units 1 to 4 were all shut down by 2007.

Two spent fuel storage facilities are part of the power plant.[7]

Reactor data[edit]

Unit Reactor type Net capacity[8] Gross capacity Thermal capacity Construction start First criticality Grid date Commercial operation Shutdown
Kozloduy 1 VVER-440 V-230 408 MWe 440 MWe 1375 MW 1 April 1970 30 June 1974 24 July 1974 28 October 1974 31 December 2002
Kozloduy 2 VVER-440 V-230 408 MWe 440 MWe 1375 MW 1 April 1970 22 August 1975 24 August 1975 10 November 1975 31 December 2002
Kozloduy 3 VVER-440 V-230 408 MWe 440 MWe 1375 MW 1 October 1973 4 December 1980 17 December 1980 20 January 1981 31 December 2006
Kozloduy 4 VVER-440 V-230 408 MWe 440 MWe 1375 MW 1 October 1973 25 April 1982 17 May 1982 20 June 1982 31 December 2006
Kozloduy 5 VVER-1000 V-320 1003 MWe 1040 MWe 3120 MW 9 July 1980 5 November 1987 29 November 1987 23 December 1988 (2047)
Kozloduy 6 VVER-1000 V-320 1003 MWe 1040 MWe 3120 MW 1 April 1982 29 May 1991 2 August 1991 30 December 1993 (2051)

Safety concerns and consequent shutdown of Units 1 to 4[edit]

Units 1-4

Kozloduy NPP previously operated four older reactors of the VVER-440/230 design, but under a 1993 agreement between the European Commission and the Bulgarian government, Units 1 and 2 were taken off-line at the beginning of 2004. An unpublished 1995 report by the United States Department of Energy had supposedly listed those units among the world's "ten most dangerous reactors".[9] On 21 October 2010, licenses for the shutdown reactors were transferred to Bulgaria state radioactive waste enterprise DP RAO, signaling the formal beginning of decommissioning work.[10]

Throughout the 1990s and early 2000s Units 3 and 4, originally licensed for operation until 2011 and 2013, respectively, underwent substantial safety improvements and, after rigorous inspections, received positive reviews from the IAEA[11] in 2002, and from the World Association of Nuclear Operators (WANO) in the following year, concluding that "no technical reasons exist for the early closure of units 3 & 4".[12] Backed by these findings, the government had hoped to convince the European Commission to allow a postponement of the agreed pre-accession shutdown; from a legal and political standpoint, however, this proved untenable. Units 3 and 4 were taken out of operation in the final hours of 2006, immediately prior to the country's accession to the European Union.

82 metric tons of its spent fuel were sent to a repository in Zheleznogorsk, Krasnoyarsk Krai during 2001 and 2002.[13] In 2008, officials at the power plant announced their intention to use CONSTOR storage casks for this purpose.[14]

Prior to the shutdown of units 3 and 4, Kozloduy NPP produced 44% of Bulgaria's electricity supply; as of March 2006, Bulgaria exported about 14% of its electricity production.

Pressure to restart[edit]

In January 2009, during the 2008 Bulgarian energy crisis, Bulgaria's president Georgi Parvanov suggested that Unit 3 be restarted.[15] However, this was never pursued as an option. In principle, under the conditions of its Accession Treaty Bulgaria could request temporary derogation from its commitments in the event of serious economic difficulties arising within the first three years of membership in the union.[16]

Units 5 and 6[edit]

Inside the control room of Unit 5

Units 5 and 6 are VVER-1000 reactors, construction of which finished in 1987 and 1991 respectively. By 2017 Unit 5 was to be upgraded to reach a capacity of 1,100 MWe, as part of a programme to extend the life of the unit by 30 years.[3]

In 2021 an alternative secondary fuel supply agreement was made with Westinghouse Electric Company, for supply diversification.[6]

On 30 December 2022, an agreement was made with Framatome to supply fuel and fuel assemblies for Unit 6 of the Bulgarian Nuclear Power Plant.[17][18]


Kozloduy Nuclear Power Plant is a subsidiary of Bulgarian Energy Holding EAD.[19][20]

Future expansion[edit]

In 2012 Bulgaria's government decided to start the construction of a new reactor in Kozloduy after it gave up on the construction of what was supposed to be the country's second nuclear power plant in Belene. Thus, the Bulgarian government decided to install in Kozloduy the 1000 MW reactor that the Russian state company Atomstroyexport already produced for the Belene NPP.[21] The Belene Nuclear Power Plant project was terminated in late March 2012.

In October 2013, the Ministry of Environment and Water approved the environmental impact assessment report on the investment proposal for Unit 7, thereby giving a green light for its construction.[22] A month later it was announced that construction of the reactor could begin in 2019 if full approval is granted by the Council of Ministers in 2014.[23] The Bulgarian Energy Holding (short BEH) propose to construct a Westinghouse AP1000. Negotiations between the BEH and Westinghouse already started.[24]

In 2013 the Austrian Environment Agency prepared a report on the Bulgarian Ministry for the Environment's Environmental Impact Assessment (EIA) on the proposed 7th unit of the Kozloduy Nuclear Power Plant. It assesses whether the EIA-Report allows for making reliable conclusions about the potential trans-boundary impacts on Austria. The Austrian report considers the assumption, that the Kozloduy NPP site is flood-proof, to be well-founded and the seismic hazard at the site to be low (but points out that the seismic hazard study needs updating as it was performed 20 years ago). It also highlights a number of unsubstantiated claims and some failings in the Bulgarian EIA report. These include:

  • shortcomings in the safety analyses of the reactors being considered, including a lack of the consideration of post-Fukushima lessons learned and, as far as applicable, the use of the concept of practical elimination (pgs 60-61);
  • serious gaps in the assessment of the impact of external human induced events such as crashes, leaks etc. (pgs 72-73);
  • contrary to IAEA (2002) analysis requirements, the EIA report does not contain considerations about the formation of pressure shock waves and their possible impact on buildings of the NNU due to explosions outside the perimeter of the NPP (pg 73)
  • no comprehensible technical basis provided for an evaluation of design basis accidents and severe accidents (pg 84)
  • only three (insufficient) “typical” dry case weather conditions were used for the calculations of the trans-boundary impacts on the Austrian territory, not worse case scenarios.[25]


  1. ^ Bulgaria quits Belene Nuclear Power Plant project Archived 2012-04-17 at the Wayback Machine, Novinite, 28 March 2012
  2. ^ "Kozloduy NPP Plc - History". Kznpp.org. Archived from the original on 2011-07-27. Retrieved 2011-03-16.
  3. ^ a b "Russia contracted to upgrade Bulgarian reactors". Nuclear Engineering International. 22 October 2015. Archived from the original on 26 October 2015. Retrieved 27 October 2015.
  4. ^ "Bulgaria weighs merits of Belene NPP or Kozloduy extension". Neimagazine.com. Archived from the original on 31 July 2017. Retrieved 29 March 2017.
  5. ^ "Bulgaria to pay up to 601.6 mln euro to Atomstroyexport for scrapped Belene project by Dec 25". Seenews.com. Archived from the original on 30 March 2017. Retrieved 29 March 2017.
  6. ^ a b "Westinghouse signs VVER fuel licensing contract". World Nuclear News. 5 February 2021. Retrieved 10 February 2021.
  7. ^ "Kozloduy NPP EAD 2016 Annual Report" (PDF). Kznpp.org. p. 9. Archived (PDF) from the original on 15 June 2018. Retrieved 15 June 2018.
  8. ^ "Nuclear Reactors in Bulgaria". World Nuclear Association. Retrieved 2 December 2022.
  9. ^ Broad, William J. (1995-07-23). "U.S. Lists 10 Soviet-Built Nuclear Reactors as High Risk". The New York Times. Archived from the original on 2011-03-23. Retrieved 2009-01-07.
  10. ^ "All change at shut-down Bulgarian reactors". World Nuclear News. 2010-10-21. Archived from the original on 2012-04-01. Retrieved 2010-10-27.
  11. ^ "IAEA Experts Review Safety of Kozloduy Units 3 and 4". IAEA. 2002-07-09. Archived from the original on 2009-02-14. Retrieved 2009-01-08.
  12. ^ "Nuclear Power in Bulgaria". World Nuclear Association. 2008-12-01. Archived from the original on 2009-01-21. Retrieved 2009-01-08.
  13. ^ Glenn E. Schweitzer; A. Chelsea Sharber; et al. (2005). An international spent nuclear fuel storage facility: exploring a Russian site as a prototype : proceedings of an international workshop. US National Research Council, Committee on the Scientific Aspects of an International Spent Nuclear Fuel Storage Facility in Russia. National Academies Press. pp. 145, 146. ISBN 978-0-309-09688-1.
  14. ^ "The English Language Bulletin of Kozloduy Nuclear Power Plant" (PDF). Kznpp.org. 2008. Archived (PDF) from the original on 2011-07-16. Retrieved 2010-10-09.
  15. ^ "Bulgaria urges return to nuclear". BBC. 2009-01-06. Archived from the original on 2009-01-07. Retrieved 2009-01-07.
  16. ^ "Act concerning the conditions of accession of the Republic of Bulgaria and Romania and the adjustments to the Treaties on which the European Union is founded". Official Journal of the European Union. 2005-06-01. Archived from the original on 2011-05-22. Retrieved 2009-01-07.
  17. ^ "Kozloduy and Framatome sign nuclear fuel agreement". World Nuclear News. 4 January 2023. Retrieved 5 January 2023.
  18. ^ "Nucléaire: la Bulgarie signe un accord inédit avec Framatome pour s'affranchir du combustible russe". World Nuclear News. 30 December 2022. Retrieved 5 January 2023.
  19. ^ "Bulgaria Consolidates Five Energy Companies into Holding". Sofia News Agency. 2008-02-13. Archived from the original on 2008-02-14. Retrieved 2008-02-24.
  20. ^ "Bulgaria announces birth of energy giant with new holding company". Power Engineering. 2008-02-14. Archived from the original on 2008-10-18. Retrieved 2008-02-24.
  21. ^ "Bulgaria to Set Up Project Company for New Kozloduy N-Plant Unit - Novinite.com - Sofia News Agency". Novinite.com. Archived from the original on 29 December 2018. Retrieved 29 December 2018.
  22. ^ "Bulgaria's Environment Ministry OKs EIA Report on Unit 7 of Kozloduy NPP". Novinite.com. 3 October 2013. Archived from the original on 4 October 2013. Retrieved 3 October 2013.
  23. ^ "Business.dir.bg - бизнес новините на Dir.bg". Business.dir.bg. Archived from the original on 29 December 2018. Retrieved 29 December 2018.
  24. ^ "Bulgaria to begin talks with Westinghouse on new Kozloduy nuclear reactor". Sofiaglobe.com. 11 December 2013. Archived from the original on 12 June 2019. Retrieved 29 December 2018.
  25. ^ "Kozloduy NPP – Construction of unit 7: Expert Statement to the Environmental Impact Assessment Report" Archived 2014-02-27 at the Wayback Machine Andrea Wallner, Helmut Hirsch Adhipati Y. Indradiningrat, Oda Becker, Mathias Brettner, Environment Agency Austria, 2013

External links[edit]