The dismantling of the Mühleberg nuclear power plant is progressing well
Published: Wednesday, Dec 18th 2024, 11:20
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The decommissioning of the Mühleberg nuclear power plant in the canton of Bern is well underway. Five years ago, on December 20, 2019, BKW took the nuclear power plant off the grid.
"Even if I hadn't expected it, you do get emotional when it's shut down," recalls Stefan Klute, Head of Nuclear at BKW Energie AG and Site Manager at Mühleberg, on the day of the shutdown. At the time, Switzerland was able to watch live on television as the Mühleberg nuclear power plant (KKM) was taken off the grid and see the reactions of the workforce. A visit to the site by the Keystone-SDA news agency shows the current status of the dismantling work.
The fitting with the switch-off button is covered and will be exhibited in the National Museum in Zurich in the near future. There is no longer much activity in the control room. Many displays and lights are covered and out of order. There are plenty of workstations for the three employees on duty during the visit.
Just over 300 employees still work at the Mühleberg site and are responsible for the dismantling. Around two thirds of them worked for the KKM when it was still in operation. The Mühleberg nuclear power plant was commissioned in 1972 and supplied Switzerland with electricity for 47 years.
The dismantling is progressing
Five years after the start of dismantling, 6,500 tons of just over 20,000 tons have been removed. Around 11,000 tons of this is equipment such as metals. The rest is concrete and material on the site. "We are making good progress. We have achieved all our goals so far," says Klute. Only the dismantling of the core installations is experiencing delays. Of the 97 projects currently underway, around five percent are not on target, according to the dismantling manager.
The dismantling of the reactor's control rods was recently completed by a Swedish specialist company. The control rods are used to regulate and shut down a nuclear reactor. They were dismantled in water as they had been strongly activated during operation. The water serves to shield the radioactivity.
The next milestone in the dismantling process is to empty the fuel element storage pool, in which the fuel elements and control rods were located, said Klute. The pool is twelve meters deep and has a volume of 850,000 liters.
The condenser will also be emptied by the end of the year. In the condenser, the steam that passes through the turbine - where the electricity is generated - is cooled down and converted back into a liquid state. Cooling water from the River Aare is used for this.
According to the BKW timetable, the site will be released for possible subsequent use from 2034. The site should be free of radioactive material by the end of 2030. Dismantling the nuclear power plant is a complex process. Every single screw has to be dismantled, cleaned and measured before it is allowed to leave the KKM.
Everything is cleaned
A distinction is made between activated material and contaminated material. Activated material is material that has been made radioactive by irradiation with neutrons. Activated material must be disposed of as radioactive waste.
This was also done with the control rods. After being processed under water, they were placed in barrels with thick metal shielding. The barrels were cemented and taken to the interim storage facility in Würenlingen in Aargau.
BKW also had an interim storage facility at the Mühleberg site with 4,000 drums filled with operational waste. BKW began emptying this storage facility in 2018 and completed it this year.
Contaminated material on the other hand is not radioactive itself, but is contaminated with so-called radionuclides. The impurities originate from contact between the material and liquids or gases containing radioactive particles. As they only affect the surface, they can be removed. The removed contaminants are disposed of as radioactive waste.
The material dismantled at the Mühleberg nuclear power plant - whether stainless steel, aluminum or cable - first goes to material treatment after dismantling. Once the pieces have been shredded, they go to the appropriate processing facility to remove their radioactive activation.
In wet decontamination, an employee in a yellow full protective suit works on the parts with a high-pressure cleaner with a force of 3000 bar. On a car, the cleaner would destroy the paint and tires. Alternatively, the parts are also treated with steel grit in the dry decontamination plant.
©Keystone/SDA
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