View source for Beznau Nuclear Power Plant

{{Short description|Nuclear power plant in Canton of Aargau, Switzerland}}
{{Use dmy dates|date=March 2020}}
{{Infobox power station
| name                    = Beznau Nuclear Power Plant
| image                   = Kkw_beznau.jpg
| image_caption           = Beznau Nuclear Power Plant
| coordinates             = {{coord|47.552107|8.228492|type:landmark_region:CH-AG|display=inline,title}}
| name_official           = Kernkraftwerk Beznau
| country                 = [[Switzerland]]
| location                = [[Döttingen, Switzerland|Döttingen AG]], [[Zurzach District|Zurzach]]
| status                  = Operational
| construction_began      = 1965
| commissioned            = {{start date|1969|09|01|df=y}}
| decommissioned          = 
| cost                    = 
| owner                   = [[Axpo Holding]]
| operator                = 
| ps_units_operational    = 2 × 365&nbsp;MW
| ps_units_uc             = 
| ps_units_planned        = 
| ps_units_decommissioned = 
| np_reactor_type         = PWR
| np_reactor_supplier     = [[Westinghouse Electric Corporation|Westinghouse Electric]]
| ps_cogeneration         = Yes (150 GW·h<sub>t</sub>/y)
| ps_cooling_source       = [[Aare]]
| ps_electrical_capacity  = 730
| ps_electrical_cap_fac   = 91.8%
| ps_annual_generation    = 5,826
| website                 = {{URL|http://www.axpo.com/axpo/ch/en/axpo-erleben/kraftwerke/kernenergie.html}}
}}
{{Switzerland nuke plant map|float=right|width=260}}
The '''Beznau nuclear power plant''' ({{langx|de|'''Kernkraftwerk Beznau'''}} ['''KKB''']) is a [[nuclear power plant]] of the Swiss energy utility [[Axpo Holding|Axpo]], located in the municipality [[Döttingen, Switzerland|Döttingen]], [[Canton of Aargau]], Switzerland, on an artificial island in the [[Aare river]]. The plant has been operating since September 1969.

== History ==

=== 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.<ref name="FOE2006">{{citation |url=http://www.bfe.admin.ch/themen/00511/index.html?lang=de&dossier_id=00748 |title=Authorizations for nuclear installations |access-date=2010-10-28 |author=Swiss Federal Office of Energy |author-link=Swiss Federal Office of Energy |date=2006-01-23 |archive-url=https://web.archive.org/web/20081003115256/http://www.bfe.admin.ch/themen/00511/index.html?lang=de&dossier_id=00748 |archive-date=3 October 2008 |url-status=dead }}. In German.</ref>

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.<ref name="FOE2006"/>

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.<ref>{{cite press release | title = The Federal Council issues authorizations regarding the Nuclear Energy Act | publisher = [[Swiss Federal Office of Energy]] | date = 2004-12-03 | url = http://www.bfe.admin.ch/energie/00588/00589/00644/index.html?lang=de&msg-id=13878 | access-date = 2010-10-28 | archive-url = https://web.archive.org/web/20110520195605/http://www.bfe.admin.ch/energie/00588/00589/00644/index.html?lang=de&msg-id=13878 | archive-date = 20 May 2011 | url-status = dead }} In German.</ref>

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,<ref>{{cite web | title = Chronic of nuclear energy in Switzerland | url = http://www.nuklearforum.ch/117327714764-de-index.html | access-date = 2010-10-28 | author = Nuklearforum Schweiz | author-link = Nuklearforum Schweiz | archive-url = https://web.archive.org/web/20081228003032/http://www.nuklearforum.ch/117327714764-de-index.html | archive-date = 28 December 2008 | url-status = dead }} In German.</ref> 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.<ref>{{cite web | title = Results of the initiative ''Für eine Zukunft ohne weitere Atomkraftwerke'' | url=http://www.admin.ch/ch/d//pore/va/19840923/can321.html | access-date = 2010-10-28 | date = 1984-09-23}} {{cite web | title = Results of the initiative ''Für den Ausstieg aus der Atomenergie'' | url=http://www.admin.ch/ch/d//pore/va/19900923/can365.html | access-date = 2010-10-28 | date = 1990-09-23}} {{cite web | title = Results of the initiative ''Stopp dem Atomkraftwerkbau'' (''Moratorium'') | url=http://www.admin.ch/ch/d//pore/va/19900923/can366.html | access-date = 2010-10-28 | date = 1990-09-23}} {{cite web | title = Results of the initiative ''Strom ohne Atom – Für eine Energiewende und schrittweise Stilllegung der Atomkraftwerke'' (''Strom ohne Atom'') | url=http://www.admin.ch/ch/d//pore/va/20030518/can501.html | access-date = 2010-10-28 | date = 2003-05-18}} {{cite web | title = Results of the initiative ''Moratorium Plus – Für die Verlängerung des Atomkraftwerk-Baustopps und die Begrenzung des Atomrisikos'' (''MoratoriumPlus'') | url=http://www.admin.ch/ch/d//pore/va/20030518/can502.html | access-date = 2010-10-28 | date = 2003-05-18}} In German, French, or Italian.</ref> Finally, in 2007 the cantonal parliament entrusted the government to act in order to promote the building of a new reactor.<ref>{{citation | url = http://www.ag.ch/grossrat/iga_grw_ges.php?GesNr=673933&AbfDetailNew=1 | title = Parliamentary mandate for the promotion of a replacement of Beznau 1 and 2 | access-date = 2010-10-28 | author = Grand Council of Aargau | date = 2007-03-13 | author-link = List of legislative and executive councils of the Cantons of Switzerland | archive-url = https://web.archive.org/web/20110726151135/http://www.ag.ch/grossrat/iga_grw_ges.php?GesNr=673933&AbfDetailNew=1 | archive-date = 26 July 2011 | url-status = dead }}. In German.</ref>

No date for a definitive shutdown of the KKB had 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.<ref>{{Cite web|url=https://www.insurancejournal.com/news/national/2015/11/29/390222.htm |title = Aging U.S. Nuclear Plants Pushing Limits of Life Expectancy|date = 30 November 2015}}</ref> Beznau's Unit 1 is among the oldest commercial nuclear power plants still in operations as of<ref>{{Cite web|last=IAEA|date=2017|title=Nuclear Power Reactors in the World|url=https://www-pub.iaea.org/books/IAEABooks/12237/Nuclear-Power-Reactors-in-the-World-2017-Edition |language=English}}</ref> 2024.

==== 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.

==== 2015 Unit 1 shutdown ====
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.<ref>{{Cite web|url=http://www.thelocal.ch/20151008/worlds-oldest-nuclear-reactor-like-emmental |title=World's oldest nuclear reactor 'like Emmental'|date=8 October 2015}}</ref> Similar cavities, although smaller in number, size and extension,<ref>{{cite web|url=https://www.ensi.ch/en/wp-content/uploads/sites/5/2015/08/reactor_pressure_vessel_beznau_1_geschwaerzt.pdf |title=Letter from ENSI to WENRA "Reactor Pressure Vessel in Swiss NPP Beznau 1: Detection of flaw indications similar to those identified in Belgium"}}</ref> were first discovered in the [[Doel Nuclear Power Station#2012 Doel 3 hydrogen damage|Belgian Doel 3 reactor]], consequently the Swiss Federal Nuclear Safety Inspectorate (ENSI) asked Beznau and [[Gösgen Nuclear Power Plant|Gösgen]] NPPs to perform adequate testing on their reactor pressure vessel. It must be said that the [[wikt:flaw|flaw]] indications in the Belgian NPPs ([[Doel Nuclear Power Station|Doel-3]] and [[Tihange Nuclear Power Station|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 was shut down upon the discovery of material defects.<ref>[http://www.luzernerzeitung.ch/nachrichten/wirtschaft/Kein-Termin-fuer-Hochfahren-von-AKW-Beznau-1;art46442,1012237 Kein Termin für Hochfahren von AKW Beznau 1] {{Webarchive|url=https://web.archive.org/web/20170421100729/http://www.luzernerzeitung.ch/nachrichten/wirtschaft/Kein-Termin-fuer-Hochfahren-von-AKW-Beznau-1;art46442,1012237 |date=21 April 2017 }}, [[Luzerner Zeitung]], 20 April 2017</ref>

==== 2018 Unit 1 restart ====
Unit 1 was expected to restart in 2016, but various delays pushed the restart to 2018 once Axpo had proved that the inclusions found in the reactor pressure vessel steel did not have a negative effect on safety.<ref>{{cite web |url=https://www.ensi.ch/en/2018/03/08/beznau-1-aluminium-oxide-inclusions-not-negative-impact-reactor-pressure-vessel-safety/ |title=Beznau 1: Aluminium oxide inclusions do not have a negative impact on reactor pressure vessel safety |date=8 March 2018 | publisher= [[Swiss Federal Nuclear Safety Inspectorate]] |url-status=live |archive-url=https://web.archive.org/web/20180330043110/https://www.ensi.ch/en/2018/03/08/beznau-1-aluminium-oxide-inclusions-not-negative-impact-reactor-pressure-vessel-safety/ |archive-date=30 March 2018 |access-date=4 April 2024 }}</ref><ref>{{cite web |url=https://www.swissinfo.ch/eng/society/beznau-controversy_complaint-filed-against-restart-of-world-s-oldest-nuclear-reactor/43958210 |title=Complaint filed against restart of world’s oldest nuclear reactor |date=9 March 2018 | publisher=[[Swiss Broadcasting Corporation]] |url-status=live |archive-url=https://web.archive.org/web/20190514193822/https://www.swissinfo.ch/eng/society/beznau-controversy_complaint-filed-against-restart-of-world-s-oldest-nuclear-reactor/43958210 |archive-date=14 May 2019 |access-date=4 April 2024 }}</ref>

==== Assessing 80 years operation ====
In 2024 Axpo began assessing the technical feasibility of operating the Beznau nuclear power plant beyond the planned 60 years, beyond 2030.<ref>{{cite web |url=https://www.neimagazine.com/news/newsaxpo-considers-extended-operation-of-beznau-npp-11658913 |title=Axpo considers extended operation of Beznau NPP |date=4 April 2018 | website=www.neimagazine.com |url-status=live |archive-url=https://web.archive.org/web/20240404173032/https://www.neimagazine.com/news/newsaxpo-considers-extended-operation-of-beznau-npp-11658913 |archive-date=4 April 2024 |access-date=4 April 2024 }}</ref> In December 2024, Axpo announced a CHF 350m investment to keep Beznau Unit 2 operational until 2032, and Unit 1 until 2033.<ref>{{cite web |title=Beznau to operate beyond 60 years |url=https://www.world-nuclear-news.org/articles/beznau-to-operate-beyond-60-years |website=World Nuclear News |language=en |date=6 December 2024}}</ref>

=== 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.<ref>{{cite press release | title = Axpo und BKW reichen Rahmenbewilligungsgesuche für Ersatz-Kernkraftwerke in Beznau und Mühleberg ein | publisher = Axpo AG | date = 2008-12-04 | url = http://www.axpo.ch/axpo/de/kernenergie_multi/medien/medienmitteilungen/2008/dezember_2008/axpo_und_bkw_reichenrahmenbewilligungsgesuchefuerersatz-kernkraf.html | access-date = 2010-10-28 | archive-url = https://web.archive.org/web/20110706221835/http://www.axpo.ch/axpo/de/kernenergie_multi/medien/medienmitteilungen/2008/dezember_2008/axpo_und_bkw_reichenrahmenbewilligungsgesuchefuerersatz-kernkraf.html | archive-date = 6 July 2011 | url-status = dead }}</ref> 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 [[cooling tower|tower]].<ref>{{cite web | title = Operation Beznau replacement nuclear power plant | publisher = [[Axpo AG]] | url = http://www.axpo.ch/axpo/en/kernenergie/wissen/ersatzkernkraftwerkbeznau/betrieb.html | access-date = 2010-10-28 | archive-url = https://web.archive.org/web/20101031202516/http://axpo.ch/axpo/en/kernenergie/wissen/ersatzkernkraftwerkbeznau/betrieb.html | archive-date = 31 October 2010 | url-status = dead }}</ref><ref>{{cite web | title = Adaptation of the structure plan; Decisions on the nuclear power plants | publisher = [[Canton of Aargau]] | url = http://www.ag.ch/grossrat/iga_grw_ges.php?GesNr=791078 | access-date = 2010-11-01 | archive-url = https://web.archive.org/web/20110726151826/http://www.ag.ch/grossrat/iga_grw_ges.php?GesNr=791078 | archive-date = 26 July 2011 | url-status = dead }}</ref>

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 Company|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.<ref>[[Swiss Federal Nuclear Safety Inspectorate]] (ENSI): Annual Report 2013, S. 28 (also available online under www.ensi.ch)</ref>

Characterized by a thermal power of 1130&nbsp;MW, each unit produces 365&nbsp;MW net electricity through two [[Brown, Boveri & Cie|Brown Boveri]] turbine generators. Over the years the net electric power produced has been increased twice: it was 350&nbsp;MW until 30 September 1996 and 357&nbsp;MW until 2 January 2000.<ref>{{citation | url = http://www.bfe.admin.ch/php/modules/publikationen/stream.php?extlang=de&name=de_742447706.pdf | title = Swiss electricity statistic 2007 | access-date = 2010-10-28 | author = Swiss Federal Office of Energy | author-link = Swiss Federal Office of Energy | date = 2008-06-01 | archive-url = https://web.archive.org/web/20110726051207/http://www.bfe.admin.ch/php/modules/publikationen/stream.php?extlang=de&name=de_742447706.pdf | archive-date = 26 July 2011 | url-status = dead }}. In German.</ref> The energy is delivered to the 220&nbsp;kV grid.

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

{| class="wikitable" style="text-align:center;" 
|- 
! Unit
! Type
! Net electrical power
! Gross electrical power
! Construction start
! Critical state
! Connected to electricity grid
! Commercial operation
! Shutdown
|-
| style="text-align:left;"| Beznau 1
| [[Pressurized water reactor|PWR]]
| 365&nbsp;MW
| 380&nbsp;MW
| Sep. 1965
| Jun. 1969
| Jul. 1969
| Dec. 1969
| 2033 (est)
|-
| style="text-align:left;"| Beznau 2
| [[Pressurized water reactor|PWR]]
| 365&nbsp;MW
| 380&nbsp;MW
| Jan. 1968
| Oct. 1971
| Oct. 1971
| Mar. 1972
| 2032 (est)
|}

=== Refuna nuclear district heating ===
The Beznau NPP has been supplying the [[district heating]] system '''Refuna''' since 1984. This reduces the effect of the plant on the water temperature of the [[Aar]] river, and provides eleven surrounding municipalities with up to 150 GW·h of carbon-free heat per year. Beside Döttingen, the connected municipalities are [[Bad Zurzach]], [[Klingnau]], [[Unterendingen]], [[Endingen, Switzerland|Endingen]], [[Böttstein]], [[Tegerfelden]], and in the bordering [[Baden District, Aargau|Baden District]], [[Würenlingen]] and [[Untersiggenthal]], and in the other bordering [[Brugg District]], [[Rüfenach]] and [[Villigen]]. The heat extraction, at a supply temperature from 125&nbsp;°C in winter down to 80&nbsp;°C in summer, induces a loss of electric power, but less than 18 GW·h<sub>e</sub>/year at 2 MW<sub>e</sub> 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&nbsp;[[Cubic metre|m<sup>3</sup>]] of [[natural gas]], averaging more than 5,800&nbsp;m<sup>3</sup> of natural gas consumption yearly saved for each of the 2,432 connected homes and customers.<ref>{{cite web
 | url =http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/29/067/29067739.pdf
 | title =75 MW heat extraction from Beznau nuclear power plant
 | last1 = Handl
 | first1 = K.H.
 | year = 1998
 | website = www.iaea.org
 | publisher =[[International Atomic Energy Agency]]
 | access-date = 15 September 2016
 }}</ref><ref>{{cite web
 |url=https://www.oecd-nea.org/ndd/workshops/nucogen/presentations/5_Schmidiger_Experience-Operating-Nuclear-Swi.pdf 
 |title=Experience of operating nuclear district heating in Switzerland 
 |last1=Schmidiger 
 |first1=Roland 
 |date=5 April 2013 
 |website=www.oecd-nea.org 
 |publisher=[[Axpo Holding|Axpo Power AG]] 
 |archive-url=https://web.archive.org/web/20150927070902/http://www.oecd-nea.org/ndd/workshops/nucogen/presentations/5_Schmidiger_Experience-Operating-Nuclear-Swi.pdf 
 |archive-date=27 September 2015 
 |url-status=live 
 |access-date=15 September 2016 
 |df=dmy 
}}</ref>

=== Safety measures ===

Since the commissioning of the two reactors numerous upgrades have been carried out to improve safety.<ref>{{citation | url = http://www.ensi.ch/fileadmin/deutsch/files/gus_30_11_04_d.pdf | title = KKW Beznau I: Safety-related statement of the HSK on the periodic security inspection | access-date = 2010-10-28 | author=Swiss Federal Nuclear Safety Inspectorate | author-link=Swiss Federal Nuclear Safety Inspectorate | date = 2004-11-30}}. In German.</ref><ref name="HSK2004">{{citation | url = http://www.ensi.ch/fileadmin/deutsch/files/gus_01_03_04_d.pdf | title = KKW Beznau II: Opinion regarding the request of the NOK for the removal of the operating license limitation | access-date = 2010-10-28 | author=Swiss Federal Nuclear Safety Inspectorate | author-link=Swiss Federal Nuclear Safety Inspectorate | date = 2004-03-01}}. In German.</ref> 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&nbsp;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.<ref>[http://woody.com/2012/05/07/not-losing-to-the-rain/ ''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.”]</ref><ref>{{cite web|url=http://woody.com/wp-content/uploads/2012/05/The-Fukushima-Daiichi-Accident-v8b.pdf. |title=A PRA {{sic|Pract|itioner|nolink=y}} Looks at the Fukushima Daiichi Accident (learns lessons from Beznau) |archive-url=https://web.archive.org/web/20131214225420/http://woody.com/wp-content/uploads/2012/05/The-Fukushima-Daiichi-Accident-v8b.pdf |archive-date=14 December 2013 |url-status=dead |df=dmy }}</ref> The at least 1.5&nbsp;m thick concrete-steel housings protect the critical systems from external agents like earthquakes or plane crashes.<ref>{{citation | url = http://www.ensi.ch/fileadmin/deutsch/files/FLA-Bericht_maerz03.pdf | title = 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 | access-date = 2010-10-28 | author=Swiss Federal Nuclear Safety Inspectorate | author-link=Swiss Federal Nuclear Safety Inspectorate | date = 2003-04-03}}. In German.</ref> Each unit of the KKB has a ''[[Containment building|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&nbsp;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&nbsp;kV grid. Further, two diesel generators expressly equipped to be able to work in case of [[Accident management (Nuclear power)|Accident management]] are also available. The NANO is connected through the fifth strand to the 50&nbsp;kV grid and contains a fifth generator. The plant main [[Uninterruptible power supply|UPS]] system can provide direct current for at least 2&nbsp;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.<ref name="HSK2004" />

== Safety events ==
{{See also|Swiss Federal Nuclear Safety Inspectorate}}

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.
{| class="wikitable" style="text-align: center;"
|-
! rowspan=2 style="width: 75px;" | Year
! colspan=8 style="width: 320px;"| [[International Nuclear Event Scale|INES]] level
! rowspan=2 style="width: 75px;" | Total
|-
! style="background: #060; color: white; width: 40px;" | 0 
! style="background: #090; width: 40px;" | 1
! style="background: #3c0; width: 40px;" | 2
! style="background: #ff0; width: 40px;" | 3
! style="background: #fc3; width: 40px;" | 4
! style="background: #f90; width: 40px;" | 5
! style="background: #f60; width: 40px;" | 6
! style="background: #f00; width: 40px;" | 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
|-
! colspan=10 style="font-size: 0.85em; padding: 6px 2px 4px 4px; text-align: left; font-weight: normal;" | '''Sources''': 2020<ref>{{cite web|url=https://www.ensi.ch/en/wp-content/uploads/sites/5/2021/06/ENSI_Aufsichtsbericht_2020_web-1.pdf |title=Aufsichtsbericht 2020 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=June 2021|access-date=2021-10-11}}</ref> 2019<ref>{{cite web|url=https://www.ensi.ch/de/wp-content/uploads/sites/2/2020/06/Aufsichtsbericht_2019_WEB.pdf |title=Aufsichtsbericht 2019 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=June 2020|access-date=2020-12-09}}</ref> 2018<ref>{{cite web|url=https://www.ensi.ch/de/wp-content/uploads/sites/2/2019/06/Aufsichtsbericht_2018_web_barrierefrei.pdf |title=Aufsichtsbericht 2018 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=June 2019|access-date=2020-12-09}}</ref> 2017<ref>{{cite web|url=https://www.ensi.ch/de/wp-content/uploads/sites/2/2018/06/ENSI_Aufsichtsbericht_2017_web.pdf |title=Aufsichtsbericht 2017 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=June 2018|access-date=2020-12-09}}</ref> 2016<ref>{{cite web|url=https://www.ensi.ch/de/wp-content/uploads/sites/2/2017/06/Aufsichtsbericht_2016_WEB-1.pdf |title=Aufsichtsbericht 2016 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=June 2017|access-date=2020-12-09}}</ref> 2015<ref>{{cite web|url=https://www.ensi.ch/de/wp-content/uploads/sites/2/2016/06/ENSI_aufsichtsbericht_2015_web-1.pdf |title=Aufsichtsbericht 2015 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=June 2016|access-date=2020-12-09}}</ref> 2014<ref>{{cite web |url=http://www.ensi.ch/en/document/2014-ensi-oversight-report-ensi-an-9252/ |title=2014 ENSI Oversight Report – ENSI-AN-9252 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=24 June 2015}}</ref>{{·}} 2013<ref>{{cite web |url=http://www.ensi.ch/en/document/2013-ensi-oversight-report-ensi-an-8800/ |title=2013 ENSI Oversight Report – ENSI-AN-8800 |publisher=[[Swiss Federal Nuclear Safety Inspectorate]] |date=30 June 2014}}</ref>{{·}} 2012<ref name="regulatory-oversight-report-2012">{{cite web |url=http://static.ensi.ch/1371652379/ensi_aufsichtsbericht_2012.pdf |title=Regulatory Oversight Report 2012 concerning nuclear safety in Swiss nuclear installations |page=20 |quote=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 |date=June 2013 |access-date=9 February 2015 |archive-date=3 March 2016 |archive-url=https://web.archive.org/web/20160303214648/http://static.ensi.ch/1371652379/ensi_aufsichtsbericht_2012.pdf |url-status=dead }}</ref>{{·}} others<ref>{{cite web | publisher=[[Swiss Federal Nuclear Safety Inspectorate]] | url = http://www.ensi.ch/index.php?id=155 | access-date = 2010-10-28 | title = Annual reports}} In German.</ref>  
|}

=== Level 2 events ===

==== 2009 ====
* 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 [[Sievert|mSv]], respectively ''(see [[Sievert#Dose examples|examples for radiation doses]])''. Incorrect settings of personal dosimeters prevented a timely warning.<ref>{{citation | url = https://www.ensi.ch/de/wp-content/uploads/sites/2/2011/08/aufsichtsbericht_2009.pdf | title = ENSI annual report 2009 | access-date = 2017-02-28 | author=Swiss Federal Nuclear Safety Inspectorate | author-link=Swiss Federal Nuclear Safety Inspectorate | date = 2010-05-05}}. In German.</ref>

=== Level 1 events ===

==== 2012 ====

* An emergency diesel generator of unit 2 failed to start during a regular function test of this emergency electrical power generator.<ref name="regulatory-oversight-report-2012" />

==== 2007 ====

* 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).<ref>{{citation | url = http://www.ensi.ch/uploads/media/gebe07d.pdf | title = ENSI annual report 2007 | access-date = 2010-10-28 | author=Swiss Federal Nuclear Safety Inspectorate | author-link=Swiss Federal Nuclear Safety Inspectorate | date = 2008-05-08}}. In German.</ref>

==== 1997 ====

* 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).<ref>{{citation | url = http://www.ensi.ch/uploads/media/jabe97d_00.pdf | title = ENSI annual report 1997 | access-date = 2010-10-28 | author=Swiss Federal Nuclear Safety Inspectorate | author-link=Swiss Federal Nuclear Safety Inspectorate | date = 1998-04-01}}. In German.</ref>

==== 1996 ====

* 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&nbsp;°C instead of at the prescribed minimum temperature of 276&nbsp;°C. The deviation from the operation specifications led to a level 1 assessment (Swiss scale level B).<ref>{{citation | url = http://www.ensi.ch/uploads/media/jabe96d.pdf | title = ENSI annual report 1996 | access-date = 2010-10-28 | author=Swiss Federal Nuclear Safety Inspectorate | author-link=Swiss Federal Nuclear Safety Inspectorate | date = 1997-04-01}}. In German.</ref>

=== 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.<ref>periodical [[Aargauer Tagblatt]], 18 July 1992</ref><ref>{{Cite web|url=http://zeitungsarchiv.nzz.ch/neue-zuercher-zeitung-vom-18-07-1992-seite-a9.html?hint=76113170 |title=ZeitungsArchiv NZZ - E-Paper}}</ref>

== See also ==
* [[Nuclear power in Switzerland]]
* [[Resun AG]]

== References ==
{{Reflist}}

== External links ==
{{Commons}}

*[https://web.archive.org/web/20100220052250/http://www.axpo.ch/axpo/en/kernenergie/wissen/kernkraftwerk_beznau.html Official power plant website]
*[http://www.axpo.ch Axpo AG]
*[http://www.resun.ch Resun AG]
*[http://www.refuna.ch Refuna AG]
*[http://www.iaea.org/cgi-bin/db.page.pl/pris.prdeta.htm?country=CH&site=BEZNAU&units=&refno=1&link=HOT&sort=&sortlong=Alphabetic%20%84Switzerland%20(Swiss%20Confederation):%20Nuclear%20Power%20Reactors%93 Power Reactor Information System – Beznau 1]
*[http://www.iaea.org/cgi-bin/db.page.pl/pris.prdeta.htm?country=CH&site=BEZNAU&units=&refno=3&link=HOT&sort=&sortlong=Alphabetic%20%84Switzerland%20(Swiss%20Confederation):%20Nuclear%20Power%20Reactors%93 Power Reactor Information System – Beznau 2]
*[https://web.archive.org/web/20080430002300/http://www.insc.anl.gov/cgi-bin/sql_interface?view=rx_com_matrix&qvar=unit&qval=316 International Nuclear Safety Center – Beznau 1]
*[https://web.archive.org/web/20080430002305/http://www.insc.anl.gov/cgi-bin/sql_interface?view=rx_com_matrix&qvar=unit&qval=317 International Nuclear Safety Center – Beznau 2]

{{CHNPPlants}}
{{Europe topic|Nuclear energy in|state=expand}}
{{Portal bar|Switzerland|Energy|Nuclear technology}}
{{Authority control}}

[[Category:Nuclear power stations in Switzerland]]