TECHNOLOGY FAREWELL TO ATOMIC ENERGY
Germany’s nuclear power plants are being cleared away bit by bit in a process that requires no excavators, wrecking balls or dynamite. Machines and robots are used, but a lot of the work is still done by hand. It’s a task for specialists.
In 2000 the German government signed an agreement with the utilities to regulate the country’s phaseout of nuclear energy. Back then, 19 nuclear power plants supplied around one third of Germany’s electricity. In 2022, none of these power plants will be in operation. Only seven are still running. The others have already been closed down and decommissioned or are being dismantled. This is a job for the engineer Jürgen-Werner Imhof, the Senior Site Manager of HOCHTIEF’s Nuclear division. He is currently managing parts of the decommissioning of eight nuclear power plants throughout Germany. HOCHTIEF has permanent teams at four of these sites; flexible teams are assigned to the other locations. Like Imhof, most of these people have worked here for decades. “One of our employees built the plant that he will now be dismantling—probably until he retires,” says Imhof. The man’s working life is also the power plant’s.The engineers identify strongly with the technology and with “their” power plants. They are specialists, and are hard to replace. “We can hardly find any new people with the right qualifications,” Imhof says. There’s still a lot of work to do, but the up- and-coming generations aren’t interested in a technology with an expiration date. That’s why the clients are following a strategy of immediate decommissioning, while workers with the requisite skills and experience are still available.
NO STANDARD CONCEPT
It is estimated that the decommissioning process will occupy HOCHTIEF engineers for at least 20 years. Although HOCHTIEF also has many experts for planning decommissioning, it took several years just to draw up the plans and obtain the dismantling approvals, says Mark Kritzmann, who heads this planning group. “There’s no standard concept,” he says. Even if two power plants or reactor buildings were originally built to be the same, their details differ because changes were made during construction and operation. According to Imhof, “the people who work here begin to question the effects of every tiny detail.” This means that no wrecking balls are used for decommissioning. Instead, the employees work with extensive and verifiable measurements, calculations, and documentation. Decommissioning proceeds from the inside out. First the reactor pressure vessel of approximately 25-centimeter-thick steel is dealt with, then the biological shield and the safety containment, each of which is made of concrete that is several meters thick. Most of the components are cut into pieces that can fit into a one-cubic-meter pallet cage. This sounds easy, but it’s actually hard to do because of the sheer volume of the material. The biological shield, for example, is a hollow cylinder with concrete walls around two and a half meters thick. Working in very tight conditions and wearing special protective suits, the employees use diamond tools to cut the cylinder apart. “It takes them about a year,” says Imhof. Another challenge is posed by the radioactivity of some of the parts, which requires very laborious and careful work. All the parts are measured for radioactivity and radiologically sampled. Every surface and seam is examined and every screw is scrutinized in pallet cage after pallet cage to find out if there were any leaks or contamination during operation. The results determine the measures, working processes, time, and money needed. Each pallet cage is then measured again. If the radioactivity is below the permitted value, the construction materials can be returned to the resource cycle. “We refer to it as ‘release measurement,’” says Imhof. Depending on the radiation levels, parts that exceed the limit are brought to an approved landfill or sealed in huge containers and put into an interim storage facility.
» THERE'S NO STANDARD CONCEPT. «
MARK KRITZMANN, HEAD OF THE DECOMMISSIONING PLANNING GROUP
AT THEIR PHYSICAL LIMITS
Although the decommissioning of a nuclear power plant is invisible and quiet from the outside, the workers on the inside drill, cut, grind, and clean the parts under laboratory conditions in a very confined space over several years. The aim is to clean contaminated material and reduce the radioactive waste to a minimum. The complicated conditions sometimes push even experienced engineers and technicians to their physical limits, despite modern technology such as the DECON surface decontamination system and the heavy-duty undercut anchor system, both of which were developed by HOCHTIEF. Remotely controlled machines and even robots are used in certain areas. It’s a meeting of the two big technologies of the future and the past: robotics and nuclear fission. In about 20 years, all that will be left at most of the sites will be halls made of meter-thick concrete: the interim storage facilities for radioactive waste. These will eventually disappear as well once Germany finds a site for the final storage of its nuclear waste. But Jürgen-Werner Imhof, Mark Kritzmann, and their colleagues will probably have retired by then.