The European XFEL is a safe facility and its construction and operation below and in densely populated areas bears no risk. There is no danger for the environment, not even in the event of an incident.
The facility creates neither noise nor noxious fumes and it cannot explode. When in operation, however, it does generate ionizing radiation and for this reason, no one is allowed to stay inside the tunnels and close to the experimental stations when the facility is running.
Reliable access control systems such as the ones that have been in use at DESY for years make sure that nobody can enter the areas that are closed during operation.
As the tunnels are located sufficiently deep below the ground, the amount of radiation reaching the surface is negligibly small compared to the natural background radiation. The European XFEL poses no threat for soil, water and air either: Even in the immediate vicinity of the tunnel walls, the amount of radioactivity generated in the soil in 20 years of operation is smaller than the radioactivity that is present in the earth by nature, and the activation of groundwater and tunnel air lies well below the legal limits.
During normal operation, after the X-ray flashes have been generated, the electrons needed for the European XFEL are directed into electron absorbers in which they are slowed down and their energy is transformed into heat. These electron absorbers are located in specially shielded shafts deep below ground, so that here again the amount of radiation reaching the surface is negligibly small compared to the radiation normally present in nature. As for the X-ray flashes, these can be eliminated directly behind the experiments in lead absorbers. Each experiment station is installed behind appropriate shielding walls and in inaccessible areas, which makes it possible to work in the experiment hall outside of these areas even when the facility is running.
Even in the event of an operation incident, the facility constitutes no danger for the environment: A technically serious incident occurs when the electron beam leaves its trajectory in the accelerator. Due to its concentrated high energy, it would then destroy parts of the facility, thereby causing a long interruption of the operation of the whole facility. From its design principle already, the European XFEL is therefore constructed in such a way that in a case like that, the particle beams are instantly directed into the corresponding electron absorbers and the whole facility is shut down at once.
The impact on nature and the environment
The impact of the European XFEL has been assessed in an environmental impact study. The plans comprise extensive compensation measures.
As every other construction project that entails large surfaces, the European XFEL and its construction influence the environment in areas affecting man, animals, plants, and the countryside as a whole. The planning for the facility aims to keep these effects as small as possible, while at the same time keeping construction costs to a minimum. The plans comprise extensive measures to avoid or reduce these repercussions and compensate for them, as well as measures that guarantee the safety of the environment.
For the public planning approval procedure, DESY commissioned the engineering firm Planungsgruppe Ökologie + Umwelt Nord to carry out an environmental impact study. This study is completed by a countryside conservation plan (Landschaftspflegerischer Begleitplan), in which various measures for the reduction and compensation of the environmental effects of the European XFEL are investigated. Both are part of the document drawn up by DESY for the public planning approval procedure. In preparation of the environmental impact study, a “scoping” hearing was held on 22 March 2004, in which the concerned local authorities and associations expressed their environmental and conservational concerns and thus created a framework for the impact study.
The European XFEL brings about temporary and permanent changes of the habitat of animals and plants, of the landscape and its recreational use in Hamburg in the Bahrenfeld and Osdorf districts and in Schenefeld. Negative repercussions on climate, air, groundwater and surface water can be ruled out. The temporary effects during the construction phase are mostly caused by noise pollution and construction site traffic, as well as disruptions of recreational functions, for example due to the momentary restriction of use of the Lise Meitner park and of parts of the Osdorfer Feldmark.
A permanent loss of landscape elements occurs at the site DESY-Bahrenfeld due to the reduction of the Lise Meitner park, which loses an area of about one hectare. In the Schenefeld area and the Osdorfer Feldmark, the planned research campus brings about changes of the habitat of animals and plants, of the landscape and its recreational use. Here landscape elements such as typical hedges (”Knicks”) are lost, and the appearance of the landscape will be altered by the buildings of the European XFEL. Existing paths and ways that have to be interrupted will be re-routed or constructed anew.
As a matter of principle, construction work for the European XFEL will be carried out in such a way as to preserve high-quality structures such as large trees, typical hedges and other near-natural copses. This will noticeably lessen the total environmental impact on animals and plants, as well as on soil and landscape. As compensation measures, it is planned to increase the value of the European XFEL sites with regard to environmental aspects, restore neighbouring areas and increase their value by laying out screening plantations, near-natural green spaces, hedges, groves, and areas that remain left to nature. A central element of these measures is the taking over of part of the large-area restoration of the Düpenau creek on the Schenefeld site and in its vicinity.