After the nuclear phase-out – what next? The challenge of dismantling
Eight German nuclear power plants can now be decommissioned after they are finally shut down. In a process that began in August 2011, the operators of Brunsbüttel, Unterweser, Krümmel, Biblis A and B, Philippsburg 1, Neckarwestheim 1 and Isar 1 are preparing to remove the nuclear fuel from the plants and shut down the power stations completely. In so doing they are drawing on the technical experience acquired during the dismantling of a number of research reactors and nuclear power plants over the past 30 years.
30 years’ experience – the essentials of dismantling
Dismantling a nuclear power plant is a lengthy task that requires extreme care. About three percent of the concrete and steel in the nuclear power plant’s total mass of several hundred thousand tonnes is radioactively contaminated. During the dismantling process the radioactive parts – which include some pipework, steel parts of the reactor pressure vessel and concrete parts of the shield around the reactor pressure vessel (the biological shield) – must be removed.
To minimise the amount of material that needs to be treated as radioactive waste, workers carefully separate radioactive materials from those that pose no risk. Radioactive items must then be safely packed and stored. Protecting staff from exposure to radiation during dismantling of the building and reactor, protecting the public and the environment and disposing safely of the radioactive waste are the primary objectives of the dismantling plan that every operator must submit.
Immediate dismantling after shutdown
The Atomic Energy Act permits both immediate dismantling and “safe enclosure” of retired nuclear power plants. In “safe enclosure” the plant is “safely enclosed” for about three decades and then dismantled. However, this approach entails some risks. After several decades the staff who had detailed knowledge of the plant while it was in operation are no longer available. Know-how important for dismantling is therefore lost. Financial crises may mean that the money currently set aside by operators can no longer be accessed in full. In addition, the site remains unavailable to the local community for other uses for a long period.
By contrast, immediate dismantling using modern technology provides effective protection for workers and the public and reduces the risks to society: even highly radioactively contaminated components can be cleaned, dismantled and packed using the equipment and know-how now available, the operating personnel’s knowledge of the particular plant can be utilised, reduction of the workforce is gradual and funding by the present operator of the plant is guaranteed.
Approval process for environmentally safe dismantling
The legal framework established over the last 20 years lays down clear guidelines for the decontamination of nuclear power plant sites. They define what materials can be disposed of in conventional construction waste landfill and which hazardous substances must be placed in secure storage. As part of the approval process the operator of the nuclear facility must provide evidence that dismantling is safe and not environmentally harmful.
The Oeko-Institut has provided an expert opinion on possible environmental impacts and proposals for environmentally safe disposal in connection with the dismantling of a number of nuclear power plants and research reactors. Radioactivity is not the only issue that arises when nuclear power plants are dismantled: conventional pollutants and problems such as noise must also be considered. For example, it is not widely known that in many plants bitumen containing polyaromatic hydrocarbons (PAH) was used to provide a seal against groundwater penetration. Because of these environmental pollutants, even building foundations that are not radioactively contaminated must usually be removed as well.
Dismantling the nuclear power plant in Rheinsberg
Since 1997 Oeko-Institut scientists have been assisting with the dismantling of the former storage facility for radioactive waste at the Rheinsberg nuclear power plant. During its operational life its buildings were seriously contaminated by radioactive liquids as a result of accidents that occurred in the 1970s and 1980s. This meant that radioactivity also entered the soil and groundwater.
The most pressing concern of Oeko-Institut staff in 1997 was therefore to urge immediate dismantling to prevent further contamination of soil and groundwater by radioactive substances. Since then they have been accompanying the dismantling process as consultants and have formulated the key tasks from the point of view of soil and groundwater protection as follows:
- Rainwater and seepage must not be allowed to penetrate the dilapidated and contaminated built structures; this is to ensure that no additional radioactively contaminated liquids leave the buildings.
- Radioactivity must not be spread into the environment during removal of contaminated parts from the plant.
- Individual dismantling stages must be planned in such a way that they do not hinder or jeopardise subsequent work or overall decommissioning.
For example, dismantling of the building foundations must be carried out in stages so that the excavator always has sufficient standing space and reach to safely recover contaminated soil that has been exposed.
Know-how loss and final storage – open issues in dismantling
Maintaining skills within the workforce during the long dismantling process is currently a challenge. Complete dismantling takes on average ten to twelve years, on top of an approval process lasting around three years. In view of the turnaround in energy policy and the growing shortage of skilled workers, young people working in nuclear power plants are likely to retrain for other jobs and new staff skilled in nuclear technology will become harder to find. Through motivation, training and knowledge management steps must be taken to maintain the know-how of the workforce throughout the dismantling process.
Embarking promptly on the necessary approval procedures for dismantling and utilising existing sector and site-specific know-how are therefore just as important as drawing up plans for the use of power plant sites after dismantling. If the last German nuclear power plant is shut down at the end of December 2022 as the law envisages, the dismantling of all nuclear power plants in Germany could be completed by around 2040.
Dialogue needed on the repository issue
Before work can start on dismantling a nuclear power plant, the nuclear fuel elements must be removed. They must be transferred from the cooling pond in the reactor building to transport and storage containers and placed in interim storage elsewhere on the site. This renders active cooling unnecessary and reduces the risk of radioactivity escaping into the environment. However, keeping the fuel elements in interim storage is not a long-term solution.
Highly radioactive fuel elements need to be permanently removed from our environment. The current view is that final storage in deep geological formations is the only viable option. The Oeko-Institut therefore believes that dialogue is needed within our society to establish a transparent repository selection process and it is helping to plan and implement appropriate procedures.