Beznau Nuclear Power Plant


Beznau Nuclear Power Plant
Kkw beznau.jpg
Beznau Nuclear Power Plant
Official nameKernkraftwerk Beznau
LocationDöttingen AG, Zurzach
Coordinates47°33′08″N 8°13′43″E / 47.552107°N 8.228492°E / 47.552107; 8.228492Coordinates: 47°33′08″N 8°13′43″E / 47.552107°N 8.228492°E / 47.552107; 8.228492
Construction began1965
Commission date1 September 1969 (1969-09-01)
Owner(s)Axpo Holding
Nuclear power station
Reactor typePWR
Reactor supplierWestinghouse Electric
Cooling sourceAare
Cogeneration?Yes (150 GW·ht/y)
Power generation
Units operational2 × 365 MW
Nameplate capacity730 MW
Capacity factor91.8%
Annual net output5,826 GW·h
External links
CommonsRelated media on Commons
Switzerland Nuclear power plants (view)
Location dot red.svg Active plants
Location dot purple.svg Closed plants

The Beznau nuclear power plant (German: Kernkraftwerk Beznau [KKB]) is a nuclear power plant of the Swiss energy utility Axpo, located in the municipality Döttingen, Canton of Aargau, Switzerland, on an artificial island in the Aar river. The plant has been operating since September 1969.


Beznau 1 and 2

Beznau 1 is the first commercial nuclear power reactor in Switzerland.

Putting an end to the traditional predilection of the Swiss power utilities for hydroelectric power, in the beginning of the 1960s the then Nordostschweizerische Kraftwerke AG (NOK, now part of Axpo Holding) started to take into account the construction of a nuclear power plant. On 23 December 1964 the Swiss Federal Office of Energy recognized the artificial island in Beznau as potential location for a reactor. The corresponding construction permit was issued on 2 November 1965 and, after only four years, on 12 May 1969 commissioning was authorized. On 24 December 1969 Beznau 1 started commercial operation.[1]

In the meantime the procedure for the construction of the identical reactor Beznau 2 had begun. The location and a first construction permit were approved on 17 November 1967, followed on 21 September 1970 by the final one. The commissioning started on 16 July 1971 and the reactor finally entered the commercial operation phase on 15 March 1972.[1]

Beznau 1 obtained an unlimited operating license already on 30 October 1970. On the contrary Beznau 2 operated under temporary licenses until 3 December 2004, when the Swiss Federal Council removed the limitation.[2]

The power plant was built in the 1960s, when little opposition to nuclear projects was present. Over the years Beznau has been the scene of some anti-nuclear protests,[3] but such opposition never widespread among the majority of the local population. The cantonal citizens systematically rejected all votes on early shutdown of existing plants and on building suspension of new ones.[4] Finally, in 2007 the cantonal parliament entrusted the government to act in order to promote the building of a new reactor.[5]

As of 2018 no date for a definitive shutdown of the KKB has been set. From a technical point of view, similar types of reactors can probably operate safely to at least 60 years and probably until 80 years.[6] Beznau's Unit 1 is among the oldest nuclear power plants still in operations as of 31 January 2016.[7]

Newspaper Tages Anzeiger commented in October 2015 that two independent sources have confirmed that the reactor 1 pressure vessel contains around 1,000 cavities of half a centimetre in diameter.[8] Similar cavities, although smaller in number, size and extension,[9] were first discovered in the Belgian Doel 3 reactor, consequently the Swiss Federal Nuclear Safety Inspectorate (ENSI) asked Beznau and Gösgen NPPs to perform adequate testing on their reactor pressure vessel. It must be said that the flaw indications in the Belgian NPPs (Doel-3 and Tihange-2) did not cause the definitive shut down of the reactors. Indeed, both reactors resumed operations once all the needed tests were passed. Unit 1 has been shut down since the discovery of such material defects. A restart was expected in 2016 in case of positive test results, but since April 2017 no deadline for a restart was announced.[10]

Greenpeace protest

At dawn on 5 March 2014, Greenpeace activists broke into Beznau, urging European governments to close down the reactors on safety grounds. Some 100 protesters dressed in orange jumpsuits climbed over the boundary fence and hoisted large banners with images of cracking reactors and announcing "The End" of nuclear power at the 45-year-old Beznau nuclear plant.

40 activists were arrested by cantonal police before noon and the others in the evening. 58 activists were reported to the Public Prosecutor for trespassing. The nuclear operator Axpo submitted a criminal complaint for trespassing.

Beznau 3 plans

In view of the substitution of the plant, Resun AG submitted a framework permit application for a third reactor to the federal authorities on 4 December 2008, designated "EKKB" (Ersatzkernkraftwerk Beznau, Beznau replacement nuclear power plant) or Beznau 3.[11] Although the technical specifications are to be defined later, the reactor of choice is to be a light water type Generation III reactor with an electrical power of 1450 MW. The cooling is to be ensured by a hybrid tower.[12][13]

The project is on indefinite hold following decisions by the Swiss federal authorities after the Fukushima Daiichi nuclear disaster in 2011 to cease constructing new nuclear power plants.

Technical specifications

Reactors and generators

The KKB is composed of two identical pressurized water reactors units (Beznau 1 and 2) delivered by Westinghouse Electric.

Both reactors are certified for the use of MOX fuel. Since 2013, no more MOX fuel elements are used in both Beznau units.[14]

Characterized by a thermal power of 1130 MW, each unit produces 365 MW net electricity through two Brown Boveri turbine generators. Over the years the net electric power produced has been increased twice: it was 350 MW until 30 September 1996 and 357 MW until 2 January 2000.[15] The energy is delivered to the 220 kV grid.

The plant is cooled using the water of the Aar river and through the district heating system Refuna.

Unit Type Net electrical power Gross electrical power Construction start Critical state Connected to electricity grid Commercial operation Shutdown
Beznau 1 PWR 365 MW 380 MW Sep. 1965 Jun. 1969 Jul. 1969 Dec. 1969
Beznau 2 PWR 365 MW 380 MW Jan. 1968 Oct. 1971 Oct. 1971 Mar. 1972

Refuna nuclear district heating

The cooling water load on the Aar river is reduced by the district heating system Refuna, that provides eleven surrounding municipalities with up to 150 GW·h/y. Beside Döttingen, the connected municipalities are Bad Zurzach, Klingnau, Unterendingen, Endingen, Böttstein, Tegerfelden, and in the bordering Baden District, Würenlingen and Untersiggenthal, and in the other bordering Brugg District, Rüfenach and Villigen. The heat extraction, at a supply temperature from 125 °C in winter down to 80 °C in summer, induces a loss of electric power, but less than 18 GW·he/year at 2 MWe average electric power loss. The energy content of the average 142 GW·h/y provided heat, is about the same as of 14,200,000 m3 of natural gas, averaging more than 5,800 m3 of natural gas consumption yearly saved for each of the 2,432 connected homes and customers.[16][17]

Safety measures

An emergency switch-off button at Beznau.

Since the commissioning of the two reactors numerous upgrades have been carried out to improve safety.[18][19] In the 1990s, the steam generators and the control technology of the reactor protection system were replaced. The control rooms were consequently adapted and new turbine controls installed.

Furthermore, each reactor unit has been equipped with an emergency building (NANO, NAchrüstung NOtstandsystem). These contain additional safety systems for the reactor emergency shutdown and for the feeding of the steam generators, a 50 kV emergency power line, and a diesel electricity generator. They are heavily protected (bunkerised) from external hazards and, if needed, are able to cool and shut down the power plant without human intervention for 72 hours.[20][21] The at least 1.5 m thick concrete-steel housings protect the critical systems from external agents like earthquakes or plane crashes.[22] Each unit of the KKB has a large dry type containment in steel and concrete.

The emergency core cooling (ECCS) is performed by a redundant high-pressure safety injection system with a total of three strands (one in the NANO). The two steam generators are provided with water by two main feeding pumps. If they fail, feeding is taken over by one of the security systems: a double-stranded auxiliary feedwater system or one of the two emergency feedwater systems, one of which part of the bunkerised NANO. Finally, in case of problems with the cooling, two containment spray systems are entrusted with the removal of excessive heat and pressure by condensation of the resulting steam.

The power plant is connected through five strands to the external power grid. Two of them are mainly used to deliver the power plant output to the 220 kV grid. They are nevertheless equipped with an emergency diesel generator each. Two other strands provide emergency power and are connected to the nearby hydroelectric power plant and the 50 kV grid. Further, two diesel generators expressly equipped to be able to work in case of Accident management are also available. The NANO is connected through the fifth strand to the 50 kV grid and contains a fifth generator. The plant main UPS system can provide direct current for at least 2 h of normal operation.

Waste management

The KKB operates, since 1993, a separate interim radioactive waste storage facility (ZWIBEZ). It is composed of a hall for low level operational waste and a second one for the dry storage of spent fuel. The waste needing conditioning is stored in the central interim storage facility (ZZL) in Würenlingen. These two deposits are to ensure the storage of the plant's waste until at least 2020.[19]

Safety events

The following is an overview of nuclear security incidents at Beznau graded on the International Nuclear Event Scale (INES), which ranges from 0 (least severe) to 7 (most severe). In the plant's history there has been one level 2 event and four level 1 events.

Year INES level Total
0 1 2 3 4 5 6 7
2020 2 2
2019 7 7
2018 4 4
2017 7 7
2016 6 6
2015 6 7
2014 10 10
2013 7 7
2012 13 1 14
2009 10 1 11
2008 4 4
2007 7 1 8
2006 2 2
2005 2 2
2004 2 2
2003 4 4
2002 2 2
2001 5 5
2000 4 4
1999 5 5
1998 2 2
1997 6 1 7
1996 3 1 4
1995 3 3
Total 123 4 1 128
Sources: 2020[23] 2019[24] 2018[25] 2017[26] 2016[27] 2015[28] 2014[29] · 2013[30] · 2012[31] · others[32]

Level 2 events


  • On 31 July 2009, during the yearly revision of Beznau 2, two workers were exposed to excessive levels of radiation because of a series of organizational flaws and uncoordinated handling by another revision team. These lead to a sudden increase in radiation levels in the room where the two technicians were working. They absorbed an equivalent dose of 37.8 and 25.4 mSv, respectively (see examples for radiation doses). Incorrect settings of personal dosimeters prevented a timely warning.[33]

Level 1 events


  • An emergency diesel generator of unit 2 failed to start during a regular function test of this emergency electrical power generator.[31]


  • In August, during the annual shutdown for revisions of Beznau 2, the 50 kV emergency power line was inactivated. Consequently, the diesel generator of Beznau 1 was switched on at low regime as prescribed by the security regulations. After the reconnection of the 50 kV line, the generator ran at a higher load because of technical reasons, but it eventually failed due to a defective relay. It was therefore assumed that while the 50 kV line was not active the generator would not have been able to run at full loading. Since the unit 2 generator was also unavailable due to the planned audit, the emergency power could be provided only by the hydroelectric plant or backup generators activated in case of flooding. The decrease in redundancy caused a deviation from the normal operation parameters and was therefore classified as a level 1 event (Swiss scale level B).[34]


  • In the course of a periodic inspection carried out by the operating personnel, a manually operated valve, which should have been open, was found to be closed. As a result of the false position, one of three emergency cooling systems of Beznau 1 was not ready for immediate use over a period of two weeks. This breach of the technical specifications led to the incident being assessed as level 1 (Swiss scale level B).[35]


  • After the revision outage, at 1 to 2% of reactor power, the new protection system for Beznau 1 and its internal power supply was to be started up with a test program. During synchronization with the new protection equipment, one of the two turbo groups inadvertently increased the load, and this caused a rise in reactor power to 12.6%. Since only the auxiliary feedwater pumps are in operation during low power, the amount of water supplied was insufficient to feed the steam generator, leading to an automatic reactor scram. The inadvertent demand on the turbo group was caused by an unforeseen reaction of the automatic turbine controller. Besides, the reactor already went critical at 251 °C instead of at the prescribed minimum temperature of 276 °C. The deviation from the operation specifications led to a level 1 assessment (Swiss scale level B).[36]

Significant events before 1995

  • In July 1992, during a revision of Beznau 1, two technicians working in the reactor sump died by suffocation. This was caused by an excessive atmospheric concentration of the argon used for welding. This accident was not due to the nuclear nature of the plant and therefore didn't receive an INES assessment.[37][38]

See also


  1. ^ a b Swiss Federal Office of Energy (23 January 2006), Authorizations for nuclear installations, archived from the original on 3 October 2008, retrieved 28 October 2010. In German.
  2. ^ "The Federal Council issues authorizations regarding the Nuclear Energy Act" (Press release). Swiss Federal Office of Energy. 3 December 2004. Archived from the original on 20 May 2011. Retrieved 28 October 2010. In German.
  3. ^ Nuklearforum Schweiz. "Chronic of nuclear energy in Switzerland". Archived from the original on 28 December 2008. Retrieved 28 October 2010. In German.
  4. ^ "Results of the initiative Für eine Zukunft ohne weitere Atomkraftwerke". 23 September 1984. Retrieved 28 October 2010. "Results of the initiative Für den Ausstieg aus der Atomenergie". 23 September 1990. Retrieved 28 October 2010. "Results of the initiative Stopp dem Atomkraftwerkbau (Moratorium)". 23 September 1990. Retrieved 28 October 2010. "Results of the initiative Strom ohne Atom – Für eine Energiewende und schrittweise Stilllegung der Atomkraftwerke (Strom ohne Atom)". 18 May 2003. Retrieved 28 October 2010. "Results of the initiative Moratorium Plus – Für die Verlängerung des Atomkraftwerk-Baustopps und die Begrenzung des Atomrisikos (MoratoriumPlus)". 18 May 2003. Retrieved 28 October 2010. In German, French, or Italian.
  5. ^ Grand Council of Aargau (13 March 2007), Parliamentary mandate for the promotion of a replacement of Beznau 1 and 2, archived from the original on 26 July 2011, retrieved 28 October 2010. In German.
  6. ^ "Aging U.S. Nuclear Plants Pushing Limits of Life Expectancy". 30 November 2015.
  7. ^ IAEA (2017). "Nuclear Power Reactors in the World". {{cite journal}}: Cite journal requires |journal= (help)
  8. ^ "World's oldest nuclear reactor 'like Emmental'". 8 October 2015.
  9. ^ "Letter from ENSI to WENRA "Reactor Pressure Vessel in Swiss NPP Beznau 1: Detection of flaw indications similar to those identified in Belgium"" (PDF).
  10. ^ Kein Termin für Hochfahren von AKW Beznau 1 Archived 21 April 2017 at the Wayback Machine, Luzerner Zeitung, 20 April 2017
  11. ^ "Axpo und BKW reichen Rahmenbewilligungsgesuche für Ersatz-Kernkraftwerke in Beznau und Mühleberg ein" (Press release). Axpo AG. 4 December 2008. Archived from the original on 6 July 2011. Retrieved 28 October 2010.
  12. ^ "Operation Beznau replacement nuclear power plant". Axpo AG. Archived from the original on 31 October 2010. Retrieved 28 October 2010.
  13. ^ "Adaptation of the structure plan; Decisions on the nuclear power plants". Canton of Aargau. Archived from the original on 26 July 2011. Retrieved 1 November 2010.
  14. ^ Swiss Federal Nuclear Safety Inspectorate (ENSI): Annual Report 2013, S. 28 (also available online under
  15. ^ Swiss Federal Office of Energy (1 June 2008), Swiss electricity statistic 2007 (PDF), archived from the original (PDF) on 26 July 2011, retrieved 28 October 2010. In German.
  16. ^ Handl, K.H. (1998). "75 MW heat extraction from Beznau nuclear power plant" (PDF). International Atomic Energy Agency. Retrieved 15 September 2016.
  17. ^ Schmidiger, Roland (5 April 2013). "Experience of operating nuclear district heating in Switzerland" (PDF). Axpo Power AG. Archived (PDF) from the original on 27 September 2015. Retrieved 15 September 2016.
  18. ^ Swiss Federal Nuclear Safety Inspectorate (30 November 2004), KKW Beznau I: Safety-related statement of the HSK on the periodic security inspection (PDF), retrieved 28 October 2010. In German.
  19. ^ a b Swiss Federal Nuclear Safety Inspectorate (1 March 2004), KKW Beznau II: Opinion regarding the request of the NOK for the removal of the operating license limitation (PDF), retrieved 28 October 2010. In German.
  20. ^ The Notstand building, a bunkered facility which could support all of the plant systems for at least 72 hours. I asked Martin Richner, the head of risk assessment, why Beznau spent so much money on the Notstand building when there was no regulation or government directive to do so. Martin answered me, “Woody, we live here.”
  21. ^ "A PRA Practitioner [sic] Looks at the Fukushima Daiichi Accident (learns lessons from Beznau)" (PDF). Archived from the original on 14 December 2013.
  22. ^ Swiss Federal Nuclear Safety Inspectorate (3 April 2003), Position of the Swiss Federal Nuclear Safety Inspectorate regarding the safety of the Swiss nuclear power plants in the event of an intentional aircraft crash (PDF), retrieved 28 October 2010. In German.
  23. ^ "Aufsichtsbericht 2020" (PDF). Swiss Federal Nuclear Safety Inspectorate. June 2021. Retrieved 11 October 2021.
  24. ^ "Aufsichtsbericht 2019" (PDF). Swiss Federal Nuclear Safety Inspectorate. June 2020. Retrieved 9 December 2020.
  25. ^ "Aufsichtsbericht 2018" (PDF). Swiss Federal Nuclear Safety Inspectorate. June 2019. Retrieved 9 December 2020.
  26. ^ "Aufsichtsbericht 2017" (PDF). Swiss Federal Nuclear Safety Inspectorate. June 2018. Retrieved 9 December 2020.
  27. ^ "Aufsichtsbericht 2016" (PDF). Swiss Federal Nuclear Safety Inspectorate. June 2017. Retrieved 9 December 2020.
  28. ^ "Aufsichtsbericht 2015" (PDF). Swiss Federal Nuclear Safety Inspectorate. June 2016. Retrieved 9 December 2020.
  29. ^ "2014 ENSI Oversight Report – ENSI-AN-9252". Swiss Federal Nuclear Safety Inspectorate. 24 June 2015.
  30. ^ "2013 ENSI Oversight Report – ENSI-AN-8800". Swiss Federal Nuclear Safety Inspectorate. 30 June 2014.
  31. ^ a b "Regulatory Oversight Report 2012 concerning nuclear safety in Swiss nuclear installations" (PDF). June 2013. p. 20. ENSI rated one event as INES Level 1 – This related to an incident at Unit 2 of the Beznau nuclear power plant where a generator failed to start during a regular function test of the energy diesel generator
  32. ^ "Annual reports". Swiss Federal Nuclear Safety Inspectorate. Retrieved 28 October 2010. In German.
  33. ^ Swiss Federal Nuclear Safety Inspectorate (5 May 2010), ENSI annual report 2009 (PDF), retrieved 28 February 2017. In German.
  34. ^ Swiss Federal Nuclear Safety Inspectorate (8 May 2008), ENSI annual report 2007 (PDF), retrieved 28 October 2010. In German.
  35. ^ Swiss Federal Nuclear Safety Inspectorate (1 April 1998), ENSI annual report 1997 (PDF), retrieved 28 October 2010. In German.
  36. ^ Swiss Federal Nuclear Safety Inspectorate (1 April 1997), ENSI annual report 1996 (PDF), retrieved 28 October 2010. In German.
  37. ^ Aargauer Tagblatt, 18 July 1992 {{citation}}: Missing or empty |title= (help)
  38. ^ "ZeitungsArchiv NZZ - E-Paper".

External links

  • Official power plant website
  • Axpo AG
  • Resun AG
  • Refuna AG
  • Power Reactor Information System – Beznau 1
  • Power Reactor Information System – Beznau 2
  • International Nuclear Safety Center – Beznau 1
  • International Nuclear Safety Center – Beznau 2