Evaluating the impact of decay heat on repository footprint in nuclear fuel cycle scenarios: Introducing the BADGER code

The management of high-level nuclear waste (HLW) and spent nuclear fuel (SNF) is an important aspect when considering any nuclear fuel cycle scenario. To address the challenges of nuclear waste disposal, tools are essential for assessing the thermal characteristics of geological disposal facilities (GDFs) across different nuclear fuel cycles, as often strict temperature limitations are in place that ultimately dictate repository footprint. This paper provides a comprehensive overview of BADGER, a code designed for modelling the thermal behaviour of repositories containing HLW and SNF. BADGER has unique capabilities in efficient thermal modelling and the ability to model the accommodation of diverse waste types within a single repository. It can also model how the evolution in time of different waste streams impact repository footprint. Notably, BADGER assesses the repository impact of different fuel cycles when coupled with a fuel cycle analysis code like ORION, calculating peak temperatures, optimal canister spacing and repository footprint. In our analysis, we demonstrate BADGER's capabilities with two illustrative UK fuel cycle scenarios: one open and one closed. For the open cycle, the repository footprint was found to be 14.32 km2, whereas for the closed cycle, it was 5.53 km2. This paper explores the features, underlying theory, verification and two illustrative UK fuel cycle scenarios, to highlight BADGER's capabilities in evaluating various fuel cycles' impact on repositories.