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The KKM is at the moment the only Swiss nuclear power plant not having an unlimited operating license. Due to the problems noticed during the commissioning and to some ongoing tests on the emergency cooling systems performed in the [[United States]], until 1980 it received a series of six months license extensions, then increased to one year.<ref name=BR1992>{{citation |url=http://www.bfe.admin.ch/php/modules/publikationen/stream.php?extlang=de&name=de_664561999.pdf&endung=Entscheid%20des%20Bundesrates%20vom%2014.%20Dezember%201992%20zum%20Gesuch%20der%20Bernischen%20Kraftwerke%20AG%20vom%209.%20November%201990%20um%20Erteilung%20einer%20unbefristeten%20Betriebsbewilligung%20und%20um%20Leistungserh%F6hung%20von%2010%%20f%FCr%20das%20Kernkraftwerk%20M%FChleberg%20(KKM)
The KKM is at the moment the only Swiss nuclear power plant not having an unlimited operating license. Due to the problems noticed during the commissioning and to some ongoing tests on the emergency cooling systems performed in the [[United States]], until 1980 it received a series of six months license extensions, then increased to one year.<ref name=BR1992>{{citation |url=http://www.bfe.admin.ch/php/modules/publikationen/stream.php?extlang=de&name=de_664561999.pdf&endung=Entscheid%20des%20Bundesrates%20vom%2014.%20Dezember%201992%20zum%20Gesuch%20der%20Bernischen%20Kraftwerke%20AG%20vom%209.%20November%201990%20um%20Erteilung%20einer%20unbefristeten%20Betriebsbewilligung%20und%20um%20Leistungserh%F6hung%20von%2010%%20f%FCr%20das%20Kernkraftwerk%20M%FChleberg%20(KKM)
|title=Decision of the Federal Council on the request for an unlimited operating license |accessdate=2009-02-11|author=[[Swiss Federal Council]] |date=1992-12-14}}. In German.</ref> They were followed by a 5 years, a 7 years, and a 10 years one. The limitations were justified by technical improvements the operator was ordered to perform.<ref name="BR1992" /> The operating license has been extended again in 1998 and will expire on Retrieved on {{Citation/fixdate|2012-12-31}}.<ref name="FOE2006" />
|title=Decision of the Federal Council on the request for an unlimited operating license |accessdate=2009-02-11|author=[[Swiss Federal Council]] |date=1992-12-14}}. In German.</ref> They were followed by a 5 years, a 7 years, and a 10 years one. The limitations were justified by technical improvements the operator was ordered to perform.<ref name="BR1992" /> The operating license has been extended again in 1998 and will expire on {{Citation/fixdate|2012-12-31}}.<ref name="FOE2006" />
The plant requested a limitation removal in 1990 and again in 1996, but they were both rejected by the [[Swiss Federal Council]] on the basis of political and technical reasons.<ref name="BR1992" /><ref>{{citation |url=http://www.bfe.admin.ch/php/modules/publikationen/stream.php?extlang=de&name=de_435243295.pdf&endung=Entscheid%20des%20Bundesrates%20vom%2028.%20Oktober%201998%20zum%20Gesuch%20der%20BKW%20Energie%20AG%20vom%208.%20Mai%201996%20um%20Aufhebung%20der%20Befristung%20der%20Betriebsbewilligung%20vom%2014.%20Dezember%201992%20f%FCr%20das%20Kernkraftwerk%20M%FChleberg |title=Decision of the Federal Council on the request for an unlimited operating license |accessdate=2009-02-11 |author=[[Swiss Federal Council]] |date=1998-10-28}}. In German.</ref> Since 2005 a third request is pending at the SFOE.<ref>{{cite press | publisher = [[Swiss Federal Office of Energy]] | title = Public consultation on the request of the Mühleberg Nuclear Power Plant for an unlimited operating license | date = 2008-05-06 | url = http://www.bfe.admin.ch/energie/00588/00589/00644/index.html?lang=de&msg-id=19150 | accessdate = 2009-02-11 }} In German.</ref>
The plant requested a limitation removal in 1990 and again in 1996, but they were both rejected by the [[Swiss Federal Council]] on the basis of political and technical reasons.<ref name="BR1992" /><ref>{{citation |url=http://www.bfe.admin.ch/php/modules/publikationen/stream.php?extlang=de&name=de_435243295.pdf&endung=Entscheid%20des%20Bundesrates%20vom%2028.%20Oktober%201998%20zum%20Gesuch%20der%20BKW%20Energie%20AG%20vom%208.%20Mai%201996%20um%20Aufhebung%20der%20Befristung%20der%20Betriebsbewilligung%20vom%2014.%20Dezember%201992%20f%FCr%20das%20Kernkraftwerk%20M%FChleberg |title=Decision of the Federal Council on the request for an unlimited operating license |accessdate=2009-02-11 |author=[[Swiss Federal Council]] |date=1998-10-28}}. In German.</ref> Since 2005 a third request is pending at the SFOE.<ref>{{cite press | publisher = [[Swiss Federal Office of Energy]] | title = Public consultation on the request of the Mühleberg Nuclear Power Plant for an unlimited operating license | date = 2008-05-06 | url = http://www.bfe.admin.ch/energie/00588/00589/00644/index.html?lang=de&msg-id=19150 | accessdate = 2009-02-11 }} In German.</ref>


Revision as of 16:28, 15 February 2009

Template:Infobox Nuclear power plant

The Mühleberg Nuclear Power Plant (in German Kernkraftwerk Mühleberg, abbreviated in KKM) is located in the Mühleberg municipality (Canton of Berne, Switzerland) north of the village near the homonym hydroelectric plant. It is operated by the BKW FMB Energie AG.

History

Mühleberg 1

In parallel with the planning of Beznau 1, the then Bernische Kraftwerke AG decided to build a second nuclear power plant in the canton of Berne. Mühleberg was identified as possible location and the Swiss Federal Office of Energy (SFOE) approved this choice on Template:Citation/fixdate. Two years later, on Template:Citation/fixdate, a first partial construction permit was issued, followed on Template:Citation/fixdate by the final one.

The reactor entered criticality in March 1971 but due to a fire in one of the turbine houses the plant had to be shut down for repairs. It eventually started the commercial operation on Template:Citation/fixdate.[1]

The KKM is at the moment the only Swiss nuclear power plant not having an unlimited operating license. Due to the problems noticed during the commissioning and to some ongoing tests on the emergency cooling systems performed in the United States, until 1980 it received a series of six months license extensions, then increased to one year.[2] They were followed by a 5 years, a 7 years, and a 10 years one. The limitations were justified by technical improvements the operator was ordered to perform.[2] The operating license has been extended again in 1998 and will expire on Template:Citation/fixdate.[1] The plant requested a limitation removal in 1990 and again in 1996, but they were both rejected by the Swiss Federal Council on the basis of political and technical reasons.[2][3] Since 2005 a third request is pending at the SFOE.[4]

The acceptance by the population has been alternating. The KKM was built in years were practically no opposition to nuclear energy was present, but the situation rapidly changed after the Chernobyl disaster. In 1992 the population of the canton of Berne expressed itself in a consultive vote with a majority of 51% against the concession of the unlimited license.[2] In 2003, however, 68% of the population rejected the initiative Strom ohne Atom, that proposed the plant shutdown in 2005.[5] A similar proposal at cantonal level had already been rejected in 2000 with a 64% majority.[6] In 2006 the Bernese government put forward a medium-term energy strategy including the renunciation to nuclear power.[7] The parliament, however, took notice of this without approval, and delegated any decision on an eventual shutdown to the federal authorities.[8] The same organ in 2007 assigned to the Bernese government the task to exert itself for the granting of an unlimited operating license. [9]

No decision has been made about a definitive shutdown date.

Mühleberg 2

Axpo and BKW have announced thought they subsidiary Resun AG on Template:Citation/fixdate that they have submitted to the competent federal authorities a framework permit application for building two new nuclear reactors, one of which should be located in Mühleberg.[10]. Although the technical specifications will be defined in a second time, the reactor of choice should be of 3rd generation light water type with a net electric power between 1200 and 1600 MW. The cooling should be ensured by an hybrid tower.[11]

Technical specifications

Reactor and generators

The KKM consists of a single boiling water reactor (BWR) of type 4 provided by General Electric Technical Services Company (GETSCO), a then subsidiary of General Electric specialized in nuclear power plants. All the 240 assemblies contain uranium oxide rods. The pressurized vessel has a diameter of 4.04 m and is 19 m high, has a wall thickness of 10.2 cm and operates at 288 °C and 72 bar.[12]

The thermal power of 1097 MW is converted into 355 MW of net electrical power by two Brown Boveri steam generators connected to the 220 kV and 50 kV grids. The power output was increased in 1990 from the original 320 MW.[13]

The system is cooled with water pumped from the Aar. This in average increases the river temperature by 1.3 °C.[14] To prevent damages to the fish population the plant activity has to be reduced when the river temperature exceeds 18 °C.

Unit Type Net electrical capacity Gross electrical capacity Construction start Critical state Connected to electricity grid Commercial operation Shutdown
Mühleberg BWR 355 MW 372 MW Mar. 1967 Mar. 1971 Jul. 1971 Nov. 1972 -

Safety measures

As all Swiss nuclear power plants, the KKM is subjected to a periodic complete safety assessment. The most recent one took place in 2007.[15]

The reactor is hosted in a five floor concrete-steel building. The walls have a thickness of 60 cm, the roof of 20-30 cm. In its lowest, partially underground part is located the 1.7-1.8 m thick steel pressure suppression drywell. The structure is able to withstand an earthquake. In case of a plane crash, however, the building could be seriously damaged. Calculations predict that at certain impact angles the crash could open a breach in the outer wall of the uppermost floor. The reactor would nevertheless remain intact due to the five 30-50 cm thick insoles and the massive drywell.[16]

The reactor is fed with water through two loops, each provided with its own pump. A third pump serves as reserve.

The emergency cooling of the nucleus is entrusted to three independent systems. A doubly redundant low pressure core spray with a 2·100% heat removal capacity is activated in case of leaks any size in the coolant system. Small leaks may be compensated by the redundant high pressure reactor core isolation cooling system (RCIC) or the redundant alternate low pressure system (ALPS).

By loss of cooling agent in the drywell, the excessive steam will spread into a torus-shaped pressure-suppression pool, where it will condense decreasing the pressure. The 4000 m3 big torus is filled with 2000 m3 water[17] and is in turn cooled by a redundant torus cooling system and a redundant shutdown and torus cooling system with a total of 4·100% residual heat removal capacity. In the extreme case of a meltdown a further system is entrusted with the integrity of the primary containment by spraying and flooding the drywell.

Emergency power is provided through two connections with the nearby Mühleberg Hydroelectric Power Plant and three diesel generators.

In 1989 the SUSAN (Spezielle Unabhängige System zur Abfuhr der Nachzerfallswärme) emergency building started operation. Bunkerized and partially underground, its function is to ensure an emergency shutdown of the reactor even in case of extreme external agents like plane crashes or simultaneous downfall of the dams upstream the plant with resulting submergence of the structures. Amongst others it contains the RCIC, the ALPS, the TCS, some systems for pressure reduction and two of the three emergency diesel generators.

Waste management

The KKM yearly produces around 35-38 m3 of radioactive waste. They are compressed in situ and transferred to the Central Interim Storage Facility (ZZL) for conditioning. After this procedure they are returned to the interim storage facility of the Mühleberg plant. KKM estimates its storage capabilities to last at least until 2022. Due to the 2006 moratorium on the recycling of spent fuel, the entire stock of exhausted rods is now transferred to the ZZL for storage.[15]

Cracks in the pressure vessel

Major concerns on the security of the reactor arise from the formation since the 1990s of some cracks in the shell of the primary containment. This is due to steel corrosion by the coolant. Notwithstanding the countermeasures (reinforcements of the shell, chemical additives in the coolant), the cracks are increasing in length year after year. The longest one are one third of the limit allowed by the security specifications and it is expected that by 2012 they should still be less than half this value. The situation is continuously monitored and other chemical measures for its stabilization are being tested.[18]

In 1986, due to the presence of similar cracks, many components of the cooling water circulation loop had to be exchanged. A substitution of the pressure vessel is however not considered necessary by the Swiss Federal Nuclear Safety Inspectorate (ENSI) that confirms that the power plant is able to operate in security at least until 2012, when the license will expire. Further technical improvements are nevertheless needed for an extension until 2032, as desired by the operator.[15]

Nuclear events

Year[19] INES level Total
0 1 2 3 4 5 6 7
2008 1 0 0 0 0 0 0 0 1
2007 1 0 0 0 0 0 0 0 1
2006 2 0 0 0 0 0 0 0 2
2005 1 0 0 0 0 0 0 0 1
2004 1 0 0 0 0 0 0 0 1
2003 4 0 0 0 0 0 0 0 4
2002 2 0 0 0 0 0 0 0 2
2001 1 0 0 0 0 0 0 0 1
2000 0 0 0 0 0 0 0 0 0
1999 3 0 0 0 0 0 0 0 3
1998 0 1 0 0 0 0 0 0 1
1997 3 0 0 0 0 0 0 0 3
1996 2 0 0 0 0 0 0 0 2
1995 1 0 0 0 0 0 0 0 1
Total 22 1 0 0 0 0 0 0 23

As of February 2009 no operative nuclear event (INES level 2 or above) ever occurred. Since 1995 only one anomaly took place.

Level 1 events

1998

  • In June, during a routine check of the reactor protection system, a technician erroneously opened a steam relief valve. The escaped steam condensed in the torus, heating the water therein contained. After 14 min the excessive torus temperature caused an emergency shutdown of the reactor. This wrong manipulation and the slowness of the control room personal's reaction were assessed as a level 1 event (swiss scale level B).[20]

Significant events before 1995

  • In September 1986 a faulty filter in the reconditioning unit for low and middle-active waste leaked a small quantity of radioactive aerosol. As result the surrounding area now shows an anthropogenic average dose rate of 0.0051 mSv/y (status 2007).[21] For comparison the corresponding Swiss legal limit for population exposure is 0.3 mSv/y[22] and the natural dose in the Mühleberg region achieves 1 mSv/y[23]
  • In July 1971, during the test phase, some turbine oil ignited. The fire heavily damaged the turbine housing, including some cable powering the security systems. Thanks to the remaining ones the reactor could be shut down. The nuclear part of the plant remained intact, but the KKM needed however serious repairs. The start of the commercial operation was therefore significantly delayed.[24]

References

  1. ^ a b Swiss Federal Office of Energy (2006-01-23), Authorizations for nuclear installations, retrieved 2009-02-11. In German.
  2. ^ a b c d Swiss Federal Council (1992-12-14), Decision of the Federal Council on the request for an unlimited operating license, retrieved 2009-02-11. In German.
  3. ^ Swiss Federal Council (1998-10-28), Decision of the Federal Council on the request for an unlimited operating license, retrieved 2009-02-11. In German.
  4. ^ "Public consultation on the request of the Mühleberg Nuclear Power Plant for an unlimited operating license" (Press release). Swiss Federal Office of Energy. 2008-05-06. Retrieved 2009-02-11. In German.
  5. ^ "Vote results in canton of Berne on the initiative Strom ohne Atom". Retrieved 2009-02-11. In German.
  6. ^ "Vote results on the Bernese cantonal initiative for the shutdown of the Mühleberg Nuclear Power Plant". Retrieved 2009-02-11. In German.
  7. ^ Executive Council of Berne (2006-06-05), Energy policy 2006 (PDF), retrieved 2009-02-11. In German.
  8. ^ Grand Council of Berne (2006-11-29), Daily journal of the November 2006 session (PDF), pp. 1007–1023, retrieved 2009-02-11. In German.
  9. ^ Grand Council of Berne (2007-11-29), Daily journal of the November 2007 session (PDF), pp. 1182–1187, retrieved 2009-02-11. In German.
  10. ^ "Axpo and BKW submit framework permit applications for replacement nuclear power plants in Beznau and Mühleberg" (PDF) (Press release). Resun AG. 2008-12-04. Retrieved 2009-02-11.
  11. ^ "Technical specifications of Mühleberg 2". Resun AG. Retrieved 2009-02-11.
  12. ^ BKW FMB Energie AG, Technical specifications of the KKM (PDF), retrieved 2009-02-11. In German.
  13. ^ Swiss Federal Office of Energy (2008-06-01), Swiss electricity statistic 2007 (PDF), retrieved 2009-02-11. In German.
  14. ^ Daniel Bernet (November 2000), Problematic points for the waters of the High Aar and its fish population (PDF), retrieved 2009-02-11. In German.
  15. ^ a b c Swiss Federal Nuclear Safety Inspectorate (2007-12-12), Safety-Related Statement of the HSK on the Periodic Security Inspection of the Mühleberg Nuclear Power Plant (PDF), retrieved 2009-02-11. In German.
  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 2009-02-11. In German.
  17. ^ International Atomic Energy Agency (1979-04-27), Decontamination of operational nuclear power plants (PDF), retrieved 2009-02-11.
  18. ^ Swiss Federal Nuclear Safety Inspectorate and TÜV Energie Consult GbR (1999-11-01), Position of the HSK and the TÜV Energie Consulting on the cracks in the KKM containment vessel (PDF), retrieved 2009-02-11. In German.
  19. ^ "Nuclear events". Swiss Federal Nuclear Safety Inspectorate. Retrieved 2009-02-11. In German.
  20. ^ Swiss Federal Nuclear Safety Inspectorate (1999-04-01), ENSI Annual Report 1998 (PDF), retrieved 2009-02-11. In German.
  21. ^ Swiss Federal Nuclear Safety Inspectorate (2008-05-08), ENSI Annual Report 2007 (PDF), retrieved 2009-02-11. In German.
  22. ^ Swiss Federal Nuclear Safety Inspectorate (2003-05-01), ENSI directive R-11 (PDF), retrieved 2009-02-11. In German.
  23. ^ Swiss Federal Nuclear Safety Inspectorate. "Dose rate baseline map of Switzerland - Muhleberg region". Retrieved 2009-02-11. In German.
  24. ^ Fokus Anti-Atom. "Short History of the KKM". Retrieved 2009-02-11. In German.

See also

Wikimedia Commons has media related to Mühleberg Nuclear Power Plant.


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