The International Atomic Energy Agency’s (IAEA’s) International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO) was established in 2000 with the goal to ensure a sustainable nuclear energy supply to meet the global energy needs in the 21st century. The INPRO activities on global and regional nuclear energy scenarios provide newcomers and mature nuclear countries alike with better understanding of options for making a collaborative transition to future sustainable nuclear energy systems. Collaborative project GAINS (Global Architecture of Innovative Nuclear Energy Systems Based on Thermal and Fast Reactors Including a Closed Fuel Cycle) developed an internationally verified analytical framework for assessing such transition scenarios. The framework (hereafter, GAINS framework) is a part of the integrated services provided by IAEA to Member States considering initial development or expansion of their nuclear energy programmes. The paper presents major elements of the analytical framework and selected results of its application, including:
• Long-term nuclear energy demand scenarios based on the IAEA Member States’ high and low estimations of nuclear power deployment until 2030 and expected trends until 2050 and on forecasts of competent international energy organizations;
• Heterogeneous world model comprised of groups of non-personified non-geographical countries (NGs) with different policy regarding nuclear fuel cycle back end;
• Architectures of nuclear energy systems;
• Metrics and tools for the assessment of dynamic nuclear energy system evolution scenarios regarding sustainability, including a set of key indicators and evaluation parameters;
• An internationally verified database with best estimate material flow and economic characteristics of existing and advanced nuclear reactors and associated nuclear fuel cycles needed for material flow analysis and comparative economic analysis, extending the previously developed IAEA databases and taking into account preferences of different countries;
• Selected results of sample analysis for scenarios involving transition from the present fleets of nuclear reactors and fuel cycles to future sustainable nuclear energy system architectures involving innovative technological solutions.