Decommissioning of the nuclear facilities at the Risoe National Laboratory in Denmark

After 40 years of nuclear research, Denmark has decided to close down all nuclear facilities except the Waste Management Plant at the Risoe National Laboratory, namely the DR 1, DR 2 and DR 3 research reactors and the Hot Cells. At a later stage it will be decided to decommission these facilities of which the Waste Management Plant will be decommissioned last.The DR 2 reactor was closed in 1975, the Hot Cells in 1993 and the DR 1 and DR 3 reactors in 2000.The selection of an optimum decommissioning strategy depends on many factors, e.g. the national policy, the characteristics of the facilities, environmental protection, radioactive waste management, future use of the site, and the cost and availability of funds for decommissioning. Two overall strategies have been considered: (1) an irreversible entombment, where the nuclear facility is entombed in concrete and thereby transformed into a final repository for low and medium level waste, and (2) decommissioning to 'green field' condition, where all buildings, equipment and materials that cannot be decontaminated below established clearance levels are removed. Entombment has been rejected and three different decommissioning scenarios with green fields as the end point are being considered.The total duration of the scenarios is 20, 35 and 50 years, respectively. The paper describes the national policy on decommissioning and the organization responsible for the decommissioning is presented. The decommissioning scenarios are described with special emphasis on safety implications and costs. Management of the decommissioning waste and its characterization in terms of activity content are presented, including the construction of standard concrete containers and temporary storage facilities at the site. A large amount of inactive or very low active waste will be created during decommissioning, and clearance of this waste from regulatory control is discussed with regard to both methodology and clearance criteria. Finally, the impact of the decommissioning on the environment is briefly addressed. (author)