Beznau Nuclear Power Plant

Beznau Nuclear Power Plant

Infobox Nuclear power plant
name = Beznau Nuclear Power Plant

caption = Beznau Nuclear Power Plant
country = Switzerland
location = Döttingen (AG)
coords = coord|47.552107|N|8.228492|E|display=inline
owner =
operator = Nordostschweizerische Kraftwerke AG
built = 1965
start = December 24, 1969
end =
r_supplier = Westinghouse Electric
r_type = PWR
r_active = 2
r_active_mw = 730
r_shutdown =
r_shutdown_mw =
r_construction =
r_construction_mw =
r_canceled =
r_canceled_mw =
r_planned =
r_planned_mw =
capacity =
generation = 5939
for_year = 2007
av_annual_gen = 5920
net_gen = 195871
status = O
generators = 4 (Brown Boveri)
architect = Brown Boveri, Gibbs & Hill
cost =
constructors = Zschokke
expires = unlimited
nrc_region =
website = [ Official website]
as_of = June 11, 2008

The Beznau Nuclear Power Plant (German "Kernkraftwerk Beznau", abbreviated KKB) is located in the municipality Döttingen (canton Aargau, Switzerland) on an artificial island in the Aar river. It is operated by the Nordostschweizerische Kraftwerke AG (NOK).


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

Putting an end to the traditional predilection of the swiss power companies for the hydroelectric power, in the beginning of the 1960s the NOK started to take into account the construction of a nuclear power plant. On December 23, 1964 the Federal Office of Energy (FOE) recognized the artificial island in Beznau as potential location for a reactor. The corresponding construction permit was issued on November 2, 1965 and, after only four years, on May 12, 1969 commissioning was authorized. On December 24, 1969 Beznau 1 started the commercial operation. [ FOE - Authorizations for Nuclear Installations] , 2006 (in German)]

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

Beznau 1 obtained an unlimited operating license already on October 30, 1970. On the contrary Beznau 2 received temporary licenses until December 3, 2004, when the Federal Council removed the limitation. [ [ The Federal Council Issues Authorizations Regarding the Nuclear Energy Act] (press release, in German)]

As of 2008 no date for a definitive shutdown of the KKB has been set. This should nevertheless lie in the 2020s, when the two reactors will become 50-60 years old. In view of their substitution, in December 2007 Axpo (of which NOK is a subsidiary) and BKW established the Resun AG, a company which task is to submit before end 2008 an application to the FOE for the construction of two new nuclear reactors. [ [ Axpo and BKW Plan Together Successors for Beznau and Mühleberg] (press release, in German)]

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. As for October 2008 (37th operational cycle) Beznau 1 hosts 16 bars out of 121 contain MOX, while for Beznau 2 this ratio increases to 24 of 121 (35th cycle). [ [ Authorization for starting the 37th operational cycle of Beznau 1] and [ Authorization for starting the 35th operational cycle of Beznau 2] (press releases, in German)] 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 September 30, 1996 and 357 MW until January 2, 2000. [ [ FOE - Swiss Electricity Statistic 2007] (in German)]

The plant is cooled using the water of the Aar river and trough the district heating system REFUNA, that provides eleven surrounding municipalities with 150 GW·h/y.

Security measures

Since the commissioning of the two reactors numerous upgrades have been carried out to improve security. [ [ KKW Beznau I: Safety-Related Statement of the HSK on the Periodic Security Inspection] , 2004 (in German)] [ KKW Beznau II: Report Regarding the Request of the NOK for the Removal of the Operating License Limitation] , 2004 (in German)] 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 were installed. Furthermore each reactor block has been equipped with an emergency building (NANO, "NAchrüstung NOtstandsystem"). These contain additional security 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 all heavily protected from external hazards and, if needed, they are able to cool and shut down the power plant without human intervention.

The at least 1.5 m thick concrete-steel housings protect the critical system from external agents like earthquakes or plane crashes. [ [ 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] , 2003] 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 with 200% after-heat removal capacity or one of the two emergency feedwater systems, one if which is part of the NANO.

The power plant is connected thorough five strands to the external power grid. Two of them (one every reactor) are mainly used to deliver the power plant output to a 220 kV line. They are nevertheless equipped with an emergency diesel generator each. Two other strands provide emergency power and are connected the 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 further generator. The plant main UPS system can provide electricity for at least 2 h of normal operation.

Waste Management

The KKB possesses since 1993 a separate interim radioactive waste storage facility (ZWIBEZ). It is composed by an 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 should ensure the storage of the plant's waste until at least 2020.

Nuclear events

As of September 2008 no event with INES level 2 or above ever occurred. Since 1995 three anomalies took place, but none of them involved radioactive material release.

Level 1 events


* In August, during the yearly revision of Beznau 2, the 50 kV emergency power line was deactivated. 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 run at higher load because of technical reasons, but it eventually failed due to a defective relay. It was therefore to assume that while the 50 kV line was not active the generator would not have been able to run at full loading. Since also the unit 2 generator was not available due to the planned revision, the emergency power could be provided only by the hydroelectric plant or some reserve generators that are activated in case of flood. The decrease in redundancy comported a deviation from the normal operation parameters and was therefore classified as a level 1 event (swiss scale level B). [ [ HSK Annual Report 2007] (in German)]


* 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). [ [ HSK Annual Report 1997] ]


* 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). [ [ HSK Annual Report 1996] ]


* [ Power Reactor Information System - Beznau 1]
* [ Power Reactor Information System - Beznau 2]
* [ International Nuclear Safety Center - Beznau 1]
* [ International Nuclear Safety Center - Beznau 2]

See also

* Nuclear power in Switzerland

External links

* [ Official website]

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