Fading out of the landscape

The last kilowatt hour has been fed into the grid. What happens now? Unlike Berlin’s Tegel Airport or the Gasometer in Oberhausen, finding an alternative use for disused nuclear power plants is not an appealing prospect. Decommissioning is therefore the only option and is already under way at several sites. It’s a complex process, costing around three quarters of a billion euros for each reactor, and it takes time – 20 years and more from planning to completion. The expertise of power plant staff and external consultants has a vital role to play in this context, along with effective technical supervision by the relevant authorities.

A nuclear power plant is dismantled piece by piece. Radiation levels are considerably reduced when the fuel elements are removed from the storage pond and contaminated primary circuit piping is cleaned. Nonetheless, some radiation remains in every reactor. In some parts of the reactor, it is highly concentrated; in others, there are various levels of contamination across systems and surfaces. “That’s why it’s important to plan and carry out decommissioning operations with great care; otherwise, inadvertent contamination can occur, which means that radiation is dispersed in dust or liquids to previously uncontaminated areas,” explains Christian Küppers, Deputy Head of the Nuclear Engineering and Facility Safety Division at the Oeko-Institut. So what happens to the individual components of a decommissioned nuclear power plant? Stringent rules apply: “Decommissioning a reactor produces various types of waste, and of course some of it is so highly radioactive that it has to be sent to an interim and later a final storage facility,” Küppers explains. “This applies mainly to the reactor pressure vessel and its components.” However, some materials and surfaces can be decontaminated during decommissioning operations, “for instance by ablation or sandblasting”. Below certain contamination thresholds, known as clearance levels, the materials no longer qualify as radioactive and can be disposed of by conventional methods. Most of the waste produced during decommissioning falls into this category. In order to minimise possible radiation exposure and risks as far as possible, various clearance categories are defined. “One is unrestricted safety clearance for building rubble, which can be re-used in road construction, for example,” says Christian Küppers. For some types of waste, the Radiological Protection Ordinance allows limited safety clearance, which means that it is subject to certain conditions. This applies to scrap metal, which can be melted down, and disposal of some solid and liquid waste. “For example, some of these materials can be disposed of at landfill sites which meet certain criteria as regards size and the sealing of the base of the landfill facility.”

Oeko-Institut researchers are currently working on a project on behalf of AWN, the waste management company in Neckar-Odenwald county, which focuses on the clearance of waste produced in the decommissioning of Obrigheim nuclear power plant and its disposal at the Buchen-Sansenhecken landfill facility. “AWN commissioned us to produce an expert opinion on clearance issues and to conduct follow-up checks at the nuclear plant itself,” Christian Küppers explains. The expert opinion deals with basic clearance criteria, analyses the rules applicable to the plant, and discusses monitoring of the clearance process. It also reviews and evaluates the disposal strategy. “Buchen-Sansenhecken landfill site complies with the criteria defined by the Radiological Protection Ordinance for landfill facilities that dispose of waste which has undergone clearance,” says Christian Küppers. And as he explains, the clearance levels are based on pessimistic assumptions that overestimate the expected radiological impacts. “The guidance issued by the Association of Counties in Baden-Württemberg for waste producers and landfill operators further reduces possible radiation exposure,” says Christian Küppers. As soon as disposal at Buchen-Sansenhecken begins, the Oeko-Institut’s experts will carry out checks at the Obrigheim nuclear site. “It is essential to ensure that the only materials disposed of at the landfill facility are those which have been cleared for this purpose,” he says.

What does decommissioning mean for people and the environment? Oeko-Institut experts are investigating this question as part of their many environmental impact assessments (EIAs) for decommissioning programmes, including the Jülich experimental reactor in 2008. On behalf of the Ministry of Economic Affairs, Energy and Industry of the State of North Rhine-Westphalia, the Oeko-Institut investigated the possible impacts of radioactive substances and wastewater, air pollution and noise on human health, fauna and flora, water resources and soil, etc. As part of the EIA, the researchers proposed criteria for the decommissioning of the plant, which aimed, for example, to minimise dust and noise during demolition of the buildings. “Demolition rarely forms part of the decommissioning application, because the operator argues that the buildings may ultimately be used for other purposes,” explains Christian Küppers. “But as a rule, there is no interest in any post-use of these buildings. But unless the application includes demolition, there is no scope, legally speaking, to include an assessment of its impacts in an EIA.”

The researchers are currently conducting two EIAs on the decommissioning of Philippsburg 1 and Neckarwestheim 1 nuclear plants on behalf of TÜV Süd safety standards authority. “In summer 2015, various public consultations will be held on the two decommissioning programmes, which we will attend as experts in order to answer questions about environmental impacts,” says Christian Küppers. At present, five preliminary environmental impact assessments are also being conducted. “They are needed because new facilities for waste storage and treatment, for example, are due to be constructed as part of the decommissioning process.” The preliminary assessment investigates whether an EIA is needed in these specific cases.

At least another 25 years

The decommissioning of nuclear plants is an issue which is likely to preoccupy Germany for a long time to come. Germany’s last reactor is due to be shut down in 2022, but according to Christian Küppers, it will take at least another 25 years to complete all the decommissioning programmes. “But that only applies to nuclear power plants whose decommissioning starts immediately after shutdown,” he explains. “There is also the Hamm-Uentrop reactor, which is undergoing a procedure known as safe enclosure: the fuel elements are removed, the radioactive components are gathered together in one area, and as many of the non-radioactive materials and buildings are disposed of as possible.” Christian Küppers is critical of this procedure. “Safe enclosure can last up to 40 years. By then, there will no longer be any staff available who are familiar with the plant. But time and again, experience has shown that knowledge of the plant, acquired during construction and operation, is extremely important when planning and carrying out decommissioning,” he says. So once the last kilowatt hour has been fed into the grid, decommissioning – in Christian Küppers’ view – should start as soon as possible. “Any other option simply delays the process and is likely to add to the problems.” Christiane Weihe