Socio-technical boundary conditions of advanced spent nuclear fuel management: ASOF Deliverable 4.4

The long-term management of radioactive waste and spent nuclear fuel (SNF) offers a significant challenge. SNF is mostly composed of unused uranium, but also a range of other radioactive isotopes, such as plutonium, strontium, cesium, technetium or americium. Because of the long half-lives of some of the isotopes contained in SNF, and its overall radioactivity content, the aim of radioactive waste management organizations is to safely contain and isolate SNF from the biosphere for extensive periods of time, up to one million years. In this light, geological disposal is nowadays internationally being considered as a preferable option. Geological disposal includes the deposition of wastes in an engineered disposal facility excavated several hundreds of meters underground in a suitable rock formation. Geological disposal facilities (GDFs) are based on a multi-barrier system where several engineered barriers together with the host rock are expected to safely isolate and contain radioactive wastes for the necessary timeframes. Depending on country level policies, however, SNF can be treated as radioactive waste to be directly disposed of or it can be reprocessed to extract uranium and plutonium (together over 95% of the nuclide inventory) for reuse. Reprocessing generates vitrified long-lived highly radioactive waste containing the minor actinides and fission products originally contained within SNF. This high-level waste needs to be managed in the same manner as SNF. Thus, both the direct disposal of SNF and its reprocessing currently result in a need to deal with materials that pose a radiological risk for very long periods of time (Baetslé, Wakabayashi, and Sakurai, 1999). The development and implementation of geological disposal has proven to be very challenging, and is at varied stages across various countries, due to differences in geology, policy frameworks, historic and current trajectories of research efforts, involvement of stakeholder groups, socio-cultural contexts, and nuclear programs. In Belgium, the federal government has taken a decision in principle in November 2022 to develop a deep repository for its highly active and/or long-living radioactive waste. This is however but a first step, as many important decisions still have to be taken, also leaving room for the optimization of the geological repository. With the eye on repository optimization, the ASOF project (Advanced Separation for Optimal management of spent Fuel) targets the development of new, innovative processes for the separation, conversion and conditioning of SNF elements. As an overall aim, the project conducts research within the Belgian national framework in view of a clear optimization of the final disposal project. By separating some particularly long-lived and/or radiotoxic isotopes from the SNF, and either conditioning these or transmuting them in less long-lived and/or radiotoxic elements, the amount of high-level waste (HLW) that requires geological disposal might be minimized. In this light, WP1 of the ASOF project is focused on researching advanced separation processes for different minor actinides, WP2 looks into the development of americium-containing transmutation targets, WP3 takes an interest in conditioning of the separated elements and waste streams, and WP4 studies the effects of separation and conditioning on the disposal concept. Most of the work conducted in the project hence focuses on what could be termed the ‘technical’ aspects of SNF management. However, a dedicated task in WP4 aimed to gain a better understanding of the socio-technical nature of the SNF management strategies under consideration. More particularly, an interest is taken in the socio-technical character of SNF partitioning, conditioning and/or transmutation, to reflect on the socio-technical impacts and entwinements of advanced fuel cycle research. These socio-technical entwinements are the focus of this report.