Management of the radioactive waste of European Spallation Source within the Swedish waste disposal system

The European Spallation Source AB (ESS) is the European common effort in designing and building a next generation large-scale user facility for studies of the structure and dynamics of materials. The proposed schematic layout of the ESS facility is based on a linear driver (linac) directing the proton beam (5 MW of 2.5 GeV) of 2.8 ms long pulses with a 20 Hz on a tungsten target where neutrons are produced via spallation reactions. Further the neutrons will be moderated to thermal and sub-thermal energies in a couple of moderators placed around the target. The moderators feed 22 beam-lines guiding the neutrons to the scattering instruments, mainly for neutron scattering research, as has been previously mentioned. The ESS will generate specific types of radioactive waste. This waste should be handled and disposed of within the Swedish radioactive waste management system, which is owned and operated by Svensk Kaernbraenslehantering AB, (SKB). The main objectives of this work are: i) To estimate types and quantities of waste that the ESS project will generate at different stages: commission, operation, decommissioning; ii) To allocate the waste to specific disposal route; iii) To assess the disposal volumes needed and to ensure that the ESS waste may safely be accommodated within the Swedish disposal system, SKB The amounts of ESS waste and classifications were derived using: i) precise Monte Carlo calculations ii) scaling the activity from the operation experience of the existing spallation source installations for waste such it is difficult to predict level of activation or for components of the facility in stage of the pre-conceptual model. Associated waste treatment/conditioning options were further analyzed in order to define the waste type and packet descriptions in agreement with Swedish regulations and policy. The potential final disposal routes for high activated components were decided via the comparison of the activity levels of the isotopes inside the waste with the maximum total activity limits of SKB existing and planned disposal facilities. It resulted from this analysis that the ESS waste will take up a substantial part, about 15 %, of the planned disposal volume for the Swedish radioactive waste management system. It was found also that the compilation of completely new waste type descriptions for qualification of the ESS waste for disposal will be necessary. Particular attention was devoted to 'problematic waste' as Beryllium reflector, C-14 from graphite used as core zone of the beam-dump or waste arising from the purification systems of both Helium and water cooling circuits. (authors)