One of the key issues in nuclear energy is to elaborate acceptable and safe solutions for the radioactive waste produced during the various stages of the nuclear fuel cycle. The worldwide option, as recommended by international organisations such as the IAEA (International Atomic Energy Agency) is to concentrate and contain the radioactive waste, and to isolate it from human activities.
Thus, radioactive waste should be reduced to minimal volumes, and be contained, for instance within metallic, corrosion resistant containers. These waste packages will then be disposed in either a surface disposal site in case of short-lived radioactive waste, or in a geological repository in case of long-lived or high-level radioactive waste.
Since a few years our research is focused on the surface disposal facility for short-lived waste to be constructed in Dessel and on a candidate geological disposal repository in Boom Clay.
Figure: Multibarrier system for geological disposal of radioactive waste
Figure: Artist's impression of the future Belgian surface disposal facility for short-lived radioactive waste in Dessel (source: NIRAS/ONDRAF)
At SCK•CEN various multi-disciplinary teams are carrying out research through experimental laboratory studies, modelling studies, and demonstration tests in the exploratory underground laboratory in Boom Clay located on the SCK•CEN site.
Taking geological disposal as an example, we investigate the durability of the candidate waste forms (glass, spent fuel, cement, bitumen) and container materials (Carbon steel, stainless steel). We also study the behaviour (migration, sorption, speciation) of the radionuclides in or through the engineered (buffer material) and natural barrier (clay), and the transfer of these radionuclides through the overlying natural layers.
Both "simple" interaction systems considering one material, or complex systems or processes are studied. The parameter "time" is extremely important in our research, as a surface disposal site must be safe for hundreds of years, whereas a geological disposal site must assure isolation for hundreds of thousands of years!
We also perform safety assessment studies for both surface and geological disposal projects. Here the integration is done of the entire transfer chain from the radioactivity leaching from the waste form till the uptake by man. These studies use data generated from the various studies mentioned above, consider various parameters and conditions, and lead to the calculation of the dose-to-man due to the various radionuclides a function of time after disposal.
These safety assessments will be a key element in the safety case for a candidate geological disposal site that will be established by the Belgian radioactive waste management agency NIRAS/ONDRAF.
Most of our R&D fits into the Belgian programme for disposal of radioactive waste, managed by NIRAS/ONDRAF. We also participate in many EC projects, and collaborate with other national and international institutes or organisations.
Contact: Christophe Bruggeman