Criteria for the restoration of mining residues in Germany

Residues from uranium mines and mills and from the mining of silver, tin, cobalt, nickel and other ores, as well as of coal mineralized with uranium, are situated in densely populated regions of Germany. Social and political pressure required an urgent investigation and evaluation of these residues in order to identify relevant residues which could not be disregarded from the radiation protection point of view. There were two categories of residues. First, for huge former uranium mining and milling sites, the original owner could be made liable for restoration. A large Federal rehabilitation programme for the Wismut sites was started immediately after the political change in the former East Germany in 1990 and was based on radiological as well as on social and economic concerns. Secondly, for a large number of smaller residues, sometimes dating back to the middle ages, an evaluation of their radiological relevance was necessary before decisions could be taken on the justification of a restoration. This was the objective of a Federal programme on registration, investigation and evaluation of mining residues. Up to now only minor remedial activities have been carried out in cases where an urgent need had been detected. Criteria developed by the German Commission on radiological protection (SSK) were applied for the evaluation of the residues. The primary criterion for the justification of a restoration was an annual individual effective dose of 1 mSv for all exposure pathways except for the inhalation of radon. For inhalation of radon, the primary criterion for justification was a long term average outdoor radon concentration of 50 Bq/m3 caused by the residues. Both levels were taken in addition to the natural background radiation level at a given site. These criteria were based on the upper end of the 'normal' range of naturally occurring exposure or concentration levels. SSK established reference levels in measurable quantities (activity concentration in soil, water, air and dose rate level) to identify the relevant residues through simple measurements. If the reference levels were exceeded, a site specific analysis was to be carried out to determine whether the primary criteria had been exceeded, in which case the restoration would be justified. The relevant authorities then developed exposure scenarios to be considered and calculation models for analyses specific to each site. Decisions as to restoration of sites are based on optimization. Using the SSK criteria and levels in an appropriate way, rapid decisions on a large number of similar residues under different ownership are possible, as exemplified by the Federal Project on registration, investigation and evaluation of mining residues. For the rehabilitation programme of the huge and complex Wismut sites, another approach was used. Cost-benefit analysis taking into account chemical pollutants, mechanical impacts and radiation detriment was undertaken to aid in selecting the optimum restoration option. The pros and cons of both optimization approaches are discussed in the light of future regulations concerning mining and industrial residues. Although German legislation did not require the involvement of interested parties in the decision making process, many attempts were made to inform the public on planned restoration activities and to involve the affected communities in the selection of the restoration option. (author)