Mühleberg Nuclear Power Plant

F1

Active reactors ( gross ):

The nuclear power plant Muhlenberg ( KKM ) is located in the municipality of Muhlenberg in the Canton of Bern, Switzerland. It is about 2 km north of Muhlenberg on the Aare River just below the well- Lake, 14 km west of Bern.

The nuclear power plant is equipped with a boiling water reactor ( BWR4 ) from General Electric with 373 MW of electric power. The nuclear power plant produced 2.6 billion kilowatt hours of electricity in 2011. It is operated by the BKW FMB Energy.

Due to its proximity to the federal capital of Bern and the relatively advanced age of both the system and the underlying technology, the power plant is controversial. According to daily news on 6 May 2011 was the operator is not clear whether required by the ENSI fixes the technical defects worthwhile. After a retrofit on the occasion of an extended revision, the power plant end of September 2011 went on line again.

Type of reactor and cooling

The inner containment vessel (primary containment ) of type Mark- I is equipped with a pear-shaped steel pressure vessel and a toroidal pressure reduction chamber (condenser). In contrast to the standard design of General Electric, the reactor building of the nuclear power plant Muhlenberg takes over the function of an external security container. This is under negative pressure and has an exhaust air system with filters that retain dust and foreign particles. In addition, the nuclear power plant Muhlenberg has an additional capacitor, the outer torus so-called, which can reduce any possible pressure buildup in the outer containment. The nuclear reactor is operating bar at a nominal pressure of 72.3 and contains 240 fuel assemblies. The KKM used exclusively as uranium dioxide nuclear fuel. The reactor power is primarily about 57 cruciform control rods and secondarily controlled continuously via an additional device. In 1989, the nuclear power plant Muhlenberg the special, independent system for decay heat removal ( SUSAN ) in operation. There is an additional, independent heat sink and is able to shut down the reactor automatically and autonomously and in the " cold parked state " (→ cold shutdown) to transfer and to keep this about 100 days.

Because of the relatively small capacity of the KKM, the facility has no cooling tower, but is directly cooled by Aarewasser. In the river water cooling the cooling water is taken from a river, warmed by a maximum of three degrees Celsius in the condenser and fed back into the river. Legal requirements compel reduce the operator 's performance on hot summer days with a Aarewasser temperature of over 18 degrees Celsius, in order to conserve the fish population.

History

Safety concerns

Cracks in the core shroud

The cracks in the core shroud are known since 1990. 1996 four tie rods were installed to stabilize, which have been confirmed by the Department for Nuclear Safety Inspectorate (HSK ) only provisional character. In the opinion of TÜV Nord from 2006 they are unfit.

• Between 1999 and 2005, the cracks in a weld seam grew by 1.1 meters to 2.5 meters. Thus, a quarter of the weld seam is damaged. The crack depth is up to 90 % of the wall thickness.
• At least three other welds have also cracked.
• The prediction of the growth of cracks is subject to large uncertainties: Five years ago, two new cracks of each 9 centimeters in length were discovered. For comparison: in 1995 the longest mass, five years earlier discovered crack only 7.4 centimeters.

By the end of 2010, the BKW had to ENSI submit a maintenance concept for the core shroud. The observer reports that the state of the core shroud has deteriorated further: Firstly, the plans are now totally 3.5 meters long, while the technician on the other hand at the weld seam number 4 found in the years 2009 revision for the first time a crack of the wall core shroud completely penetrates. In the year 2011 revision of the BKW will now first examine all welds - 21 years after the discovery of the first crack. End of June 2011, the power plant shut down prematurely, to gain an extra month for the necessary measures, in addition to the scheduled revision in August. The audit was completed on September 25, 2011.

Internal flooding risk

In KKM almost all security-related pumps ( emergency cooling, Toruskühlung, etc.) are housed in the so-called torus. As the only nuclear power plant this Mark 1 type of General Electric, it also has a so-called outer torus ( water trap ) and, in place of a Hausdorff space in which these pumps are the world in all other Mark 1 plants. That these pumps could fail due to a large water loss due to disturbance of flooding all in one fell swoop ( CCF ), the Institute has shown in 1990 in a report and referred to the related core damage potential. Meanwhile, so-called fire sections were installed in the torus, which are able to reduce the widespread flooding risk of the room. In an edition of 2008, the Inspectorate ENSI (formerly HSK ) called to December 2009 the operator to additional evidence that do not interfere in floors above the reactor building liberated masses of water security pump crucial.

External flooding risk

The power plant is less than equal to more dams ( hydropower plant Muhlenberg, Schiffenen and Rossens ), with that of the hydroelectric power plant Muhlenberg ( Wohlensee ) is only 2 km away. This might break in a strong earthquake. Such a dam break can cause a reaching to power plants, tidal wave and thus lead to disastrous consequences.

At the security check for new construction application, it turned out that the new plant would be built on a pedestal, because " make the results of flooding calculations ... transparent ... that the (now ) KKM is flooded depending on the scenario. " The latest earthquake study of the ENSI got now but concluded that the Wohlensee dam would withstand all 10,000 years once expected strong earthquake, which makes such a tidal wave rather unlikely.

According to the mission Einstein and the news of Swiss Television The Aare was the only cooling option for the nuclear power plant. Not only a direct flooding of the power plant but also a spillage of all water intakes by sediment posed a hazard and the water points were added in 2011, additional facilities were created with which the supply of water is possible by pumping.

Emissions

In July 2013 it was announced that increased from Lake Biel cesium -137 levels had been detected in sediment samples. The increased values ​​are due to emissions from the years 1998 and 1999, already in 2000, increased values ​​were measured in the water of Lake Biel. According to the ENSI the radioactive discharges on the water are far below the legal limit, compared to the other nuclear facilities, the charges were but still too high.

New Muhlenberg 2

BKW has filed a general license application for the replacement of the existing power plant on December 4, 2008. It is intended a reactor equipped with a maximum power of 1600 MW, and a hybrid cooling tower. In question reactors of the type EPR or KERENA ( to March 2009 referred to as SWR 1000) Areva, an AP -1000, or the ESBWR from Mitsubishi. The party and joined overarching alliance stop atomic announced immediately after the announcement of the filing of a referendum against the planned buildings. On 13 February 2011, the voters of the canton of Bern approved in an advisory vote with a majority of 51.2 % ( 51.7 % turnout ) that the Grand Council decision, which advocates the replacement of the power plant is passed to the federal on. In the Grand Council of the 91 favorable votes were against 56 Negative.

On March 14, during the series of accidents at the Japanese nuclear power plant in Fukushima I, the UVEK decided to freeze all approval process for new nuclear power stations on Swiss soil indefinitely.

Reactor data

The nuclear power plant Muhlenberg has a block: