Beznau Nuclear Power Plant

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Beznau Nuclear Power Plant
Kkw beznau.jpg
Beznau Nuclear Power Plant
Beznau Nuclear Power Plant is located in Switzerland
Beznau Nuclear Power Plant
Location of Beznau Nuclear Power Plant in Switzerland
Official name Kernkraftwerk Beznau
Country Switzerland
Location Döttingen AG
Coordinates 47°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
Status Operational
Construction began 1965
Commission date 24 December 1969 (1969-12-24)
Owner(s) Axpo Holding
Nuclear power station
Reactor type PWR
Reactor supplier Westinghouse Electric
Power generation
Units operational 2 × 365 MW
Nameplate capacity 730 MW
Capacity factor 91.8 %
Annual generation 5826 GW·h
Official website
Switzerland Nuclear power plants (view)
Location dot red.svg Active plants
Location dot purple.svg Closed plants

The Beznau nuclear power plant (in German: Kernkraftwerk Beznau, abbreviated 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. Producing energy since 1969, it can claim to be the world's oldest operating nuclear power plant (though by date of start of construction, Wylfa in Wales holds that title).


Beznau 1 and 2[edit]

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 received 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 2008 no date for a definitive shutdown of the KKB has been set. From a technical point of view, it is expected to become necessary in the 2020s, when the two reactors will be 50–60 years old.[citation needed] After the decommissioning of Oldbury Nuclear Power Station's Reactor 1 on 29 February 2012, Beznau 1 is the oldest operating nuclear power station in the world.[6]

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 scaled 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[edit]

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.[7] 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 an hybrid tower.[8][9]

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[edit]

Reactors and generators[edit]

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. As for October 2008 (39th operational cycle) Beznau 1 hosted 12 bars out of 121 contain MOX, while for Beznau 2 this ratio increased to 32 of 121 (37th cycle).[10]

Characterized by a thermal power of 1130 MW, each unit produces 365 MW net electricity through two Brown Boveri steam 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.[11] 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, that provides eleven surrounding municipalities with 150 GW·h/y.

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

Safety measures[edit]

The emergency switch-off button at Beznau.

Since the commissioning of the two reactors numerous upgrades have been carried out to improve safety.[12][13] In the 1990s the steam generators and the control technology of the reactor protecting system have been replaced. The control rooms were consequently adapted and new turbine controls installed. Furthermore each reactor block 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 generator. They are heavily protected from external hazards and, if needed, are able to cool and shut down the power plant without human intervention.

The Beznau power plant includes a 'Notstand' hardened building designed to support all of the power plants systems for 72 hours if in the event an earthquake or severe flooding hit the power plant.[14][15]

The at least 1.5 m thick concrete-steel housings protect the critical systems from external agents like earthquakes or plane crashes.[16] Each unit of the KKB has a large dry type containment in steel.

The core emergency cooling 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(a type of ESWS), with 200% decay heat removal capacity or one of the two emergency feedwater systems,(a type of ECCS) one of which is part of the 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 thorough 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 flood 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 electricity for at least 2 h of normal operation.

Waste management[edit]

The KKB possesses 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). These two deposits are to ensure the storage of the plant's waste until at least 2020.[13]

Nuclear events[edit]

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 three level 1 events.

Year INES level Total
0 1 2 3 4 5 6 7
2014 n.a.
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 81 4 1 86
Sources: 2013[17] · 2012[18] · others[19]

Level 2 events[edit]


  • On 31 July 2009, during the yearly revision of Beznau 2, two workers were exposed to too high levels of radiation because of a series of organizational errors and a wrong manipulation by another revision team. These lead to a sudden increase of the radiation level in the room where the two technicians were working. They absorbed a dose of 37.8 and 25.4 mSv, respectively (see examples for radiation doses). Incorrect settings of the personal dosimeters prevented a timely warning.[20]

Level 1 events[edit]


  • A Beznau-operator Axpo announcement came on 18 June 2012 evening: During the annual inspection in Block 1 an "irregularity in a welded seam in the inner part of the reactor lid" had been found. They would fix the problem by "additional welding". The annual inspection report quotes: 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.[18]
  • On 23 March 2012 at 19:05, the Beznau 2 reactor was manually switched off. This was due to a malfunction in one of its two major reactor pumps.[21] After three weeks it went in service on the quiet again.[22]


  • In August, during the annual audit 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 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 flood. 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).[23]


  • 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 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).[24]


  • 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).[25]

Significant events before 1995[edit]

  • 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.[26]

See also[edit]


  1. ^ a b Swiss Federal Office of Energy (2006-01-23), Authorizations for nuclear installations, retrieved 2010-10-28 . In German.
  2. ^ "The Federal Council issues authorizations regarding the Nuclear Energy Act" (Press release). Swiss Federal Office of Energy. 2004-12-03. Retrieved 2010-10-28.  In German.
  3. ^ Nuklearforum Schweiz. "Chronic of nuclear energy in Switzerland". Retrieved 2010-10-28.  In German.
  4. ^ "Results of the initiative Für eine Zukunft ohne weitere Atomkraftwerke". 1984-09-23. Retrieved 2010-10-28.  "Results of the initiative Für den Ausstieg aus der Atomenergie". 1990-09-23. Retrieved 2010-10-28.  "Results of the initiative Stopp dem Atomkraftwerkbau (Moratorium)". 1990-09-23. Retrieved 2010-10-28.  "Results of the initiative Strom ohne Atom – Für eine Energiewende und schrittweise Stilllegung der Atomkraftwerke (Strom ohne Atom)". 2003-05-18. Retrieved 2010-10-28.  "Results of the initiative Moratorium Plus – Für die Verlängerung des Atomkraftwerk-Baustopps und die Begrenzung des Atomrisikos (MoratoriumPlus)". 2003-05-18. Retrieved 2010-10-28.  In German, French, or Italian.
  5. ^ Grand Council of Aargau (2007-03-13), Parliamentary mandate for the promotion of a replacement of Beznau 1 and 2, retrieved 2010-10-28 . In German.
  6. ^ "Bald läuft das älteste AKW der Welt in der Schweiz". Badische Zeitung (in German). 23 February 2012. Retrieved 7 March 2012. 
  7. ^ "Axpo und BKW reichen Rahmenbewilligungsgesuche für Ersatz-Kernkraftwerke in Beznau und Mühleberg ein" (Press release). Axpo AG. 2008-12-04. Retrieved 2010-10-28. 
  8. ^ "Operation Beznau replacement nuclear power plant". Axpo AG. Retrieved 2010-10-28. 
  9. ^ "Adaptation of the spacial plan: decision on the nuclear power plats". Canton of Aargau. Retrieved 2010-11-01. 
  10. ^ "Authorization for starting the 39th operational cycle of Beznau 1" (Press release). Swiss Federal Nuclear Safety Inspectorate. 2010-07-20. Retrieved 2010-10-28. ; "Authorization for starting the 37th operational cycle of Beznau 2" (Press release). Swiss Federal Nuclear Safety Inspectorate. 2010-09-24. Retrieved 2010-10-28.  In German.
  11. ^ Swiss Federal Office of Energy (2008-06-01), Swiss electricity statistic 2007 (PDF), retrieved 2010-10-28 . In German.
  12. ^ Swiss Federal Nuclear Safety Inspectorate (2004-11-30), KKW Beznau I: Safety-related statement of the HSK on the periodic security inspection (PDF), retrieved 2010-10-28 . In German.
  13. ^ a b Swiss Federal Nuclear Safety Inspectorate (2004-03-01), KKW Beznau II: Opinion regarding the request of the NOK for the removal of the operating license limitation (PDF), retrieved 2010-10-28 . In German.
  14. ^ The Notstand building, a bunkered facility which could support all of the plant systems for at least 72 hours given a severe flood or earthquake which could take out the normal power and cooling facilities. 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.”
  15. ^ "A PRA Practioner Looks at the Fukushima Daiichi Accident (learns lessons from Beznau)" (PDF). 
  16. ^ Swiss Federal Nuclear Safety Inspectorate (2003-04-03), 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 2010-10-28 . In German.
  17. ^ "2013 ENSI Oversight Report – ENSI-AN-8800". Swiss Federal Nuclear Safety Inspectorate ENSI. 30 June 2014. 
  18. ^ 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 
  19. ^ "Annual reports". Swiss Federal Nuclear Safety Inspectorate. Retrieved 2010-10-28.  In German.
  20. ^ Swiss Federal Nuclear Safety Inspectorate (2010-05-05), ENSI annual report 2009 (PDF), retrieved 2010-10-28 . In German.
  21. ^ SDA (2012-03-24), Atomkraftwerk Reaktorblock 2 im Atomkraftwerk Beznau abgeschaltet – Aargau – Blick, retrieved 2012-03-24 . In German.
  22. ^ axpo (2012-04-13), Medien - Kernkraftwerk Beznau - Block 2 geht wieder ans Netz, retrieved 2012-04-14 . In German.
  23. ^ Swiss Federal Nuclear Safety Inspectorate (2008-05-08), ENSI annual report 2007 (PDF), retrieved 2010-10-28 . In German.
  24. ^ Swiss Federal Nuclear Safety Inspectorate (1998-04-01), ENSI annual report 1997 (PDF), retrieved 2010-10-28 . In German.
  25. ^ Swiss Federal Nuclear Safety Inspectorate (1997-04-01), ENSI annual report 1996 (PDF), retrieved 2010-10-28 . In German.
  26. ^ Aargauer Tagblatt, 1992-07-18  Missing or empty |title= (help)

External links[edit]