Spent Nuclear Fuel and HLW Storage towards Disposal - Challenges and Perspectives of an Integrated Approach -

The safe and secure interim storage of spent nuclear fuel and high-level waste (HLW) from nuclear power reactors is a major issue in the long term. Due to the lack of repositories for final disposal of high-level and mostly heat generating nuclear wastes and significant delays of related siting procedures throughout the world, safe interim storage for up to 80 years or even longer is inevitable from today’s perspective. For this purpose dry cask storage is increasingly favoured. Thus, efficient strategies - whether technically, economically or politically - are requested to cover (extended) interim storage, subsequent transportation, and final disposal in an integrated approach.This paper describes and discusses the major challenges of spent fuel management in Germany after the phase-out of nuclear electricity generation was decided in 2011 and a new repository siting procedure was implemented in 2013. Consequences from those decisions which were legally founded by amendments of the German Atomic Energy Act (AtG) result in the need to transfer all remaining spent fuel from limited reactor operation (last reactor shutdown until the end of 2022) into casks for subsequent dry interim storage on-site. Storage licenses are generally issued site-specific considering specific dual purpose casks (DPC) and their inventories and they are generally limited to 40 years so far. But the need for extending the interim storage period in the future has become obvious. Even though, this may not be an issue to be solved already today questions about additional safety demonstrations will arise as soon as licenses need to be extended. Certainly, these questions will ask for reliable data about the long term performance and safety of structures, systems, and components, e. g. the long term performance of cask components and materials like bolted closure systems including metal seals, or fuel rod behaviour concerning cladding materials under stress and temperature conditions. In case of dual purpose casks for storage and transportation this includes aspects on how to demonstrate transportability during or after several decades of interim storage. Long term investigations often require plenty of time and therefore need to be initiated timely.Ongoing R&D programs addressing those issues and major findings of the German disposal commission concerning the upcoming disposal site selection procedure and requirements are mentioned including aspects regarding retrievability or recovery of potential disposal canisters (including the existing dual purpose casks) from a deep geological repository.