Update of the near field temperature evolution calculations for disposal of UNE-55, MOX-50 and vitrified HLW in a supercontainer- based geological repository

In 2004-2005, right after the decision of ONDRAF/NIRAS to opt for the supercontainer for accommodating category C waste in a geological repository (ONDRAF/NIRAS, 2004), heat transport calculations have been performed in the context of the GTA (Repository Conceptual Design) working group. These calculations, reported in SCK•CEN report R-4277 (Weetjens and Sillen, 2005) aimed at calculating the evolution of the near field temperatures in a backfilled repository in order to evaluate whether these were acceptable (according to a – rather arbitrary – temperature criterion limiting the temperature in the supercontainer buffer to 100°C). The applied thermal properties of the EBS materials were at that time fairly unknown, since detailed material characterisation studies were only in an embryonic phase. Moreover, there seemed to be quite some uncertainty on the value of the thermal conductivity of the Boom Clay as well. As recently new thermal data were reported for both Boom Clay and the concrete buffer, the near field heat transport calculations are updated, taking new geometry developments (supercontainer dimensions) into account as well. Apart from an update for vitrified HLW and UOX spent fuel (UNE-55), the analysis is complemented with thermal calculations for MOX spent fuel (MOX-50), previously not yet reported.