information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise
18 Août 2013
August 11, 2013
The Greifswald nuclear power plant on the shore of the Baltic Sea in northern Germany is a three-hour drive from Berlin on the Autobahn.
During its operational phase when East Germany existed, the plant provided 10 percent of the electrical power consumed in the former German Democratic Republic. Today, it is entering the final stage of the decommissioning process.
Reactors No. 1 through No. 5, each once capable of generating 440,000 kilowatts of power, were shut down by 1990 due to rising concerns about the safety of Soviet-designed plants following the 1986 Chernobyl nuclear power plant accident.
Decommissioning of the plant started in 1995.
“Of the 30 steam generators, eight have been completely dismantled. We are deliberately taking our time. The work proceeds as we thoroughly sort and classify waste matter," said Gudrun Oldenburg, deputy head of the PR Department for EWN, a government-funded entity that is responsible for the cleanup.
Most of the equipment in the buildings, such as the reactors, turbines and steam generators, has been moved to an interim storage site on plant grounds. Within the expansive 20,000-square-meter storage facility, which looks like a huge warehouse, the temporarily transferred equipment has been arranged into orderly lines. Radiation levels beside the reactor parts read 50 microsieverts per hour. This is about the same reading as high-dose areas around the Fukushima No. 1 nuclear power plant.
In the work area, employees in coveralls and wearing protective masks labored to disconnect pieces of machinery, their cutting tools creating a shower of sparks. Equipment from inside the reactors is dismantled inside an isolated booth using tools that are operated remotely. In a different booth, workers in protective clothing resembling space suits sprayed equipment with water and an abrasive agent to decontaminate it.
“We have more than 20 years of accumulated experience in the decontamination and management of waste, more than any other nuclear power plant. We are happy to offer our skills and technology to anyone," said EWN's plant manager Henry Cordes.
The company has assisted with dismantling work at the Chernobyl nuclear power plant and other plants in Eastern Europe. Since 2002, it has been helping to dismantle Russian nuclear submarines.
After the accident in Chernobyl, anti-nuclear sentiment spread among the German people, and old nuclear power plants and those with poor profitability were slated for decommissioning. As Germany has been at the forefront of decommissioning nuclear reactors in Europe, it has accumulated know-how that allows it to dismantle and remove nuclear plants safely and efficiently.
After the accident at the Fukushima plant, the Merkel-led government decided to abandon nuclear power generation altogether and revoked operating licenses for eight plants. The nine remaining in operation will lose their licenses by 2022. As decommissioning increasingly spreads, companies will be looking to acquire more technology.
Next year, decommissioning will be completed on the Wurgassen nuclear power plant (670,000 kilowatts) operated by E.ON, a leading gas and power company. The work started in 1997, and 10,000 drums of waste matter are stored at a temporary facility constructed on the site's premises.
The company plans to move the drums to a disposal site that the government intends to construct by 2019. Manfred Winnefeld, the E.ON's plant manager, said: “Decommissioning was supposed to be completed in roughly 10 years. However, work did not proceed as smoothly as envisioned and in 2003 the schedule was revised substantially."
Even so, completing the work in roughly 16 years is quick when compared to other nuclear plants, he added.
In June, E.ON established a decommissioning business.
Erich Gerhards, senior vice president in charge of dismantling and disposal, said, “We would like to sell our process and management know-how, which has been built through extensive experience, including failure, to the global market."
(The first part of this article was written by Hisashi Hattori, senior staff writer of The Asahi Shimbun.)
NORWAY: PROMOTING VIRTUAL REALITY TECHNOLOGY
Wearing 3D glasses, I stood in front of a large screen roughly 2 meters high and 4 meters wide. The power generator projected onto the screen drew increasingly nearer. Using my hands, I grabbed hold of objects on the screen and moved them around. Sensors at the bottom of the screen sensed my movements.
Known as “Decommissioning Avatar," this leading-edge system, which employs virtual reality to recreate actual nuclear reactor decommissioning sites, was developed by Norway's Institute for Energy Technology (IFE).
It is used to confirm operational processes for work related to decommissioning a reactor and to investigate any associated risk in advance of carrying out actual work.
“The catalyst for development was technical cooperation with Japan," said IFE division head of software engineering, Terje Johnsen, 53. Work first began on using virtual reality technology when the institute was requested to simulate decommissioning of the Fugen advanced thermal reactor prototype located in Fukui Prefecture.
Compared to demolishing a regular building, there are a number of major differences in dismantling a nuclear power plant.
While proceeding with the dismantling, it is important to keep air conditioning and other equipment functioning right until the very end. While work progresses, wires and pipes that must be left operational need to be carefully selected from among an intricate maze of wiring and plumbing running throughout the plant.
Additionally, in order to reduce radioactive waste as much as possible, parts and rubble resulting from the dismantling must be carefully classified and sorted according to their level of contamination. To minimize exposure to workers, radiation levels at the site must be monitored and understood at all times.
Wanting “simulation technology that would ensure both safety and efficiency," the Fugen side approached Norway's IFE, with whom it already had a cooperative relationship, about developing an appropriate system.
In hindsight, Masanori Izumi, 34, who works for the Japan Atomic Energy Agency, operator of the Fugen plant, said: “At that time Japan's experience with decommissioning was minimal, we really didn't know much about it. We wanted to use virtual reality to acquire a realistic image of the work at hand."
The result was a system named VRdose. Computer graphics are used to recreate the actual site on a monitor. Avatars representing workers are made to move about the virtual site, allowing exposure doses to be calculated. It is possible to simulate a variety of movements and compare doses each time. At the time, the system was attracting global attention as a never-before-tried initiative.
Applying this technology, the IFE has created all kinds of simulation technology similar to the “Decommissioning Avatar" system.
The IFE provided a virtual reality program to the Leningrad nuclear power plant in Russia for use in the maintenance of its aging reactors. And, working cooperatively with the Norwegian army, it also built training software for dismantling retired Russian nuclear submarines. The institute is also engaged in developing software for aiding in the decommissioning of the Chernobyl nuclear power plant.
The IFE is an independent organization that is not affiliated with the government or any university.
Its mission is to develop “useful technology." István Szöke, 35, a senior researcher in software engineering at the institute, said, “Decommissioning should develop into quite a substantial business. We want to expand our range of activities going forward."
(The second part of this article was written by Norito Kunisue of GLOBE.)
The Asahi Shimbun GLOB
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