Experiences and Lessons Learned in Managing Severely Damaged Spent Fuel and Corium

Between 1979 and 2011, three severe nuclear power plant (NPP) accidents occurred at Three Mile Island (TMI, USA), Chornobyl (ChNPP, Ukraine), and Fukushima Daiichi (IF, Japan), resulting in melted reactor cores. Additionally, PAKs NPP Unit 2 (Hungary) experienced a loss of cooling accident in 2003 during the cleaning of irradiated fuel. The accidents at TMI and PAKs have been remediated to the extent that the material is either in monitored safe storage or is packaged pending processing. ChNPP Unit 4, which was destroyed during the accident, was finally stabilized in 2016 with the installation of new safe containment. The decommissioning of IF NPP remains a major challenge as three of the first-generation reactor cores suffered meltdown. In 2015, the Coordinated Research Project on the management of severely damaged spent fuel and corium was established. This publication examines the efforts of participating Member States in the characterization, recovery, and management of fuel containing materials (fuel assemblies, fuel debris, corium and melted corium-concrete interaction products) to support future decommissioning and environmental remediation activities. It also provides an overview of the loss of cooling accidents and insights into the evolution of corium and fuel debris in storage conditions, which will support ongoing decision-making on the management of these materials.