Muehleberg (Switzerland)

Map of Muehleberg

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BWR 320 MW, constructed by Getsco, in operation since 1971.

Facilities in Muehleberg

plantreactor typconstruction startoperation startshut down

Complaint Mühleberg

In a joint complaint after the nuclear accident in Japan in March 2011 the temporary/permanent shut-down of NPP Muehleberg is demanded.

Reasons for the request:
- the reactor in Mühleberg is of the same design as the reactor Fukushima-Daiichi
- Cracks in the reactor pressure vessel have been known since the 1990s
- The NPP is said to have safety issues concerning floods and earthquakes

14 notifiable incidents in 2010

2010 14 notifiable incidents occurred in Mühleberg, classified as INES 0, in comparison
- Beznau: 4 incidents
- Gösgen: 11 incidents
- Leibstadt: 5 incidents

In comparison: 2009 27 notifiable incidents occured in Switzerland.
The Swiss nuclear regulatory authority ENSI states that the higher number of incidents in Mühleberg was due to malfunctions during the bringing into service of new equipment after modernization of some parts of the plant.



Today morning an emergency shutdown took place in Mühleberg. The shutdown happend during the performance of tests, where problems with the control rods appeared. No additional radiation was released.


At 10:50 a safety shutdown of the Mühleberg-reactor took place. During maintenance works on a cleaning station chemical substances reached the reactor cooling circuit. The activity of the vapour shortly increased, what caused the safety shutdown.


Reactor trip following main heat sink. This event was rated INES level 0.


Leakage of a gasket at a reactor recirculation pump. This event was rated INES level 0.


Leakage at a reactor pressure vessel nozzle of the control rod drive return system. This event was rates INES level 0.


Leakage on the flow measurement of a feedwater line. This event was rated INES level 0.


Failure to start of an emergency diesel generator during a functionality test. This event was rated INES level 0.


Failure to start of a corespray system during a functionality test. This event was rated INES level 0.


British Nuclear Fuels plc (BNFL) had completed all spent fuel shipments from Muehleberg to Sellafield. Since 1995, 29 metric tons of spent fuel has been transported from Muehleberg for reprocessing in BNFL's Thorp plant under contract with Muehleberg owner BKW.
The transports were suspended from 1998 to May 2001 because of Europe-wide concerns, which have been resolved, about contamination of transport casks. Since the suspension was lifted, the final nine transports have taken place at a rapid pace "before the onset of winter weather in Switzerland," said BNFL. Other Swiss utilities still have spent fuel for Thorp, and a further 28 transports remain, said BNFL. Their completion will mark the end of Swiss spent fuel shipments to Thorp.


The reactor was switched off automatically because of the failure of a feedwater pump and the afterwards connected spare pump. The spare pump failed because of a loose current connection. It withdrew no radioactivity.


Reactor scram due to the loss of two feedwater pumps. This event was rated INES level 0.


Reactor scram due to high pressure caused by trip of both turbines (loss of heat sink). This event was rated INES level 0.


Deviation from the technical specification concerning the closing time of containment isolation valves. This event was rated INES level 0.


Loss of emergency power supply from a hydro-electric plant. This event was rated INES level 0.


Greenpeace blocks Swiss SF transport:
Greenpeace activists today blockaded two trucks carrying SF from Switzerland's Muehleberg NP station for reprocessing abroad.
The demonstrators, calling for an end to reprocessing of nuclear fuel as part of the organisations's ongoing campaign against NP, stopped the trucks on a main road in Val de Travers.
Each truck was carrying a specially-constructed SF container, measuring 5 meters by 1,9 meters and weighing 35 tons. The SF from Muehleberg had been sent for reprocessing in France or Britain on a regular basis for the past 22 years.
The transport has now continued on its way into France, following intervention by the Swiss police.



Refueling outage included strengthening of the core shroud. A GE crew installed a tie-rod system (costs 5,8 million $). Cracks detected last year had extended by a few mm, but a new crack some 50 mm long was detected. Cracks are shallow and not considered to be safety relevant; Because cracking is related to neutron embritlement a new GE neutron measuring system was added.


Core shroud corrosion inhibitor hydrogen is being injected into feedwater to test its effectiveness in protecting against core shroud cracks. The latest inspection indicated that corrosion-induced small cracks continue to appear on the shroud, but these have been deemed not safety-relevant.
The system aims to change water chemistry to reduce the shroud's vulnerability to corrosion. The Muehleberg tests will cost US$ 530,000.
A side effect of the hydrogen injection is that the radioactive isotope nitrogen-16 is augmented in the steam in the turbine building, resulting in slightly higher doses to workers and surroundings. This concentration is being measured at Muehleberg both by staff and by the Swiss Nuclear Safety Inspectorate HSK. The Swiss limit of 0.1 milliSievert per week has not been exceeded but, if used on a permanent basis, the system would require addtitional shielding in steam-piping and the turbine building.


The owner of the plant has told the swiss government in a report that the plant is technically able to operate for 50-60 years. The GE unit came on line in 1972 and is licensed to 2002. The Owner (BWK Energie AG) has invested 150 million Swiss francs ( 130 million US$) in modifications & upgrade.
BWK indicated they will work to keep the plant on line well past its 40 year design life. BWK called Muehleberg economical with yearly operating costs of SF 215 million ( $ 186 million) - not including depereciation, taxes, interest and fuel. Of the total SF 62 million ($ 54 million) goes into a decom. fund. The basis cost for electricity production is 0,07 SF