The European DISCO project: deep geological disposal of modern spent nuclear fuel

Abstract

Abstract. Direct disposal of spent nuclear fuel (SNF) in a deep-mined geological repository is foreseen in various countries. Several decades of research (incl. various European projects such as SFS, NF-PRO, MICADO, REDUPP and FIRST-Nuclides) have shown that SNF shows a number of favourable properties as a waste form. Based on this background, the scientific collaborative DISCO project (2017–2021) aims to improve the understanding of the scientific basis of the safety cases for SNF under repository conditions – specifically for modern fuels. It comprises 16 project partners from eight EU countries consisting of large research institutions and small and medium enterprises (SME's), as well as an end-user group. It is supported by the European Union's Horizon 2020 Framework Programme for Research and Innovation with about 4 million euro (EU contribution). The project concept and implementation were initiated via the Exchange Forum of the Implementation of Geological Disposal – Technology Platform (IGD-TP) based on discussions among various actors, namely waste management organisations and the research community. The specific scientific issue of the DISCO project is whether the kinetics of the SNF dissolution process are affected by the composition and characteristics of the SNF itself, with a focus on modern Cr-doped and mixed oxide (MOX) fuels, which have been developed in recent years. The effect of dopants in the fuel matrix with regard to redox reactivity of the irradiated fuel needs to be evaluated, since this may affect the dissolution behaviour of and radionuclide release from these modern fuels. The overall objectives of the DISCO project are (1) to enhance our understanding of SNF matrix dissolution under conditions representative of failed containers in reducing repository environments and (2) to assess whether novel types of fuel (MOX, doped fuels) behave in a similar manner to conventional fuels. Experimental and modelling tasks have been defined to achieve the project objectives. The expected knowledge gain is essential for waste management organisations and will provide new insights into factors affecting their safety cases as fuel systems have evolved.