Fusion energy has potential to contribute to meeting global demand for sustainable energy Increasingly, progressive fusion enterprises are seeking new pathways for the commercialization of the technology, bringing fresh ideas and different perspectives. This publication is a summary of an IAEA Workshop on this topic, outlining the main elements for the development of alternative commercialization pathways for fusion energy systems in the coming decades, bringing together expert opinions from the diverse range of disciplines that are essential to fusion's commercial success. It highlights several critical aspects to consider for new pathways and provides an outline of a roadmap for their development.

Pressure tube deformation is an important aging issue in operating heavy water reactors (HWRs) and the R&D community continues to develop improved predictive models for in-reactor deformation. To progress research on this topic, a coordinated research project on prediction of axial and radial creep in pressure tubes was conducted to investigate predictive model biases when applied to different reactor units and to gain new insights into the effects of operating conditions as well as microstructure/manufacturing effects. This publication documents the work performed and the results obtained by six participating Member States’ institutes, all with currently operating HWRs. The publication summarizes various modelling and predictive approaches considered for utilization within the nuclear industry in support of operating reactors. The findings offer some direction for incorporating the intrinsic material properties into the predictive models needed for pressure tube service life management.

This publication highlights the importance of mentoring and coaching for knowledge transfer across the generations of the workforce. It captures successful mentoring and coaching practices and approaches being followed by different types of nuclear organizations including at nuclear power plants, technical support organizations, national nuclear organizations and regulatory bodies. The publication also includes case studies from Member State organizations that have used mentoring and coaching as an effective tool for knowledge transfer, skill building and performance improvement.

Fusion neutron sources have many important practical uses, such as irradiation testing of materials and components, facilitating the production of various isotopes such as tritium, driving subcritical cores, characterizing spent nuclear fuel, and manufacturing medical isotopes. All these applications can be potentially improved by achieving higher neutron yields and fluxes in compact fusion neutron sources (CFNSs). This publication is a compilation arising from an IAEA coordinated research project on this topic and presents the project's main results and findings with the aim of supporting stakeholders in the development of CFNSs in the transition from conceptual to engineering design.

As an integral part of the International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO), several collaborative projects were established by its members. The IAEA/INPRO Collaborative Project on Environmental Impact Benchmarking Applicable for Nuclear Energy Systems under Normal Operation (ENV) was one of them. This publication is the outcome of the ENV summarising results developed under this project by the groups of national experts. It presents a set of examples of different approaches for estimating environmental impact from nuclear power plants (NPPs) under normal operation conditions in different countries based on participants’ experience and considering the IAEA Safety Standard on a generic framework for consideration of radiological environmental impact. It also contributes to the development of a common understanding in assessing releases from new NPPs and associated activities in terms of the radiation dose to members of the public. This publication will contribute to further improvement of the INPRO methodology and can help Member States applying it to perform a nuclear energy system assessment in the area of environmental impact of stressors.

Engaging in a nuclear power programme is a major undertaking with long term implications for at least hundred years. Key factors that may influence decision makers in their commitment to a nuclear power programme are of different nature, including political, socio-economic, financial, environmental, technical, or public acceptance. In line with the guidelines of the IAEA Milestones Approach, a comprehensive report corresponds to the attainment of Milestone I (ready to make a knowledgeable commitment to a nuclear power programme) and provides the rationale and strategy for pursuing a nuclear power programme, supporting the development of a national position. This publication intends to support Member States that are developing comprehensive reports by sharing the experience of the ones that have already completed this process or are well advanced on this path. The publication highlights similarities and differences in the approaches adopted, recognizing that there are several different ways and formats for developing such a report.

The design, operation, safety and decommissioning of research reactors involves complex processes that can be understood and improved through numerical analysis and benchmarking. This publication provides the final consolidated results of an IAEA coordinated research project (CRP). It comprises the benchmark studies, details of the calculations in the annexes and individual reports of the CRP participants in the on-line supplementary files. This publication is intended for operating organizations, researchers, regulatory bodies, reactor designers, technical support organizations and other parties interested in benchmarking the computer codes and models they use for research reactor operation and safety analysis.

The IAEA organizes International Collaborative Standard Problems (ICSPs) to facilitate co-operation on advancing reactor technology related activities. These activities include the development, assessment and validation of computer codes for design and safety analysis of nuclear power plants. The objective of this ICSP was to develop and facilitate open access to a set of standardized numerical test problems for selected postulated transients in pressurized heavy water reactors (PHWRs). These manufactured test problems are different from typical benchmark problems in that the specification is designed for a stylized model of a generic CANDU-6 PHWR and a reference solution is not postulated. The set of standardized numerical test problems supports the development of simulation codes, methods, and coupling frameworks. This publication provides a description of four numerical test problems, the participants' individual multi-physics methodologies applied, and simulations carried out, an independent synthesis of the results, and the lessons learned from the exercise.

In recent years there has been an evolution in numerical models used to compute tsunami propagation and run-up. Many models currently available offer a wide array of choices to the users. In parallel with the development of such numerical models, it is important that the user only applies the verified and validated numerical models that have undergone a benchmark analysis. This publication provides information and benchmark problems to enable engineers and regulators to select the most appropriate tsunami analysis software and modelling for the evaluation of tsunami hazards for nuclear installations to ensure their safety against those events. In addition, the benchmark problems will enable such users to become familiar with the limitations of the tsunami analysis modelling available in research and commercial software.

The response of a nuclear installation’s structure during an earthquake depends on the characteristics of the ground motion, the surrounding soil and the structure itself. Soil– structure interaction (SSI) analysis is used to evaluate the effects of seismic ground motion on an installation’s structure, system and components, to ensure it is designed to withstand the effects of earthquakes, without loss of safety functions. This publication presents SSI phenomena and current practices in SSI modelling, simulation methodology and analysis methods for the design and assessment of nuclear installations. It complements IAEA Safety Standards Series No. SSG-67, Seismic Design for Nuclear Installations, and No. NS-G-2.13, Evaluation of Seismic Safety for Existing Nuclear Installations.

This publication has been produced as part of the IAEA’s Modelling and Data for Radiological Impact Assessments (MODARIA) programme. It summarizes the activities of Working Group 7, which was one of ten working groups within MODARIA, and focused on the harmonization and intercomparison of models for the accidental release of tritium to the atmosphere. It addresses the modelling of tritium into the atmosphere and the subsequent terrestrial processes that determine the dynamic transfer of tritium in the environment. The first half of the report contains a literature review regarding state-of-the-art modelling of tritium in the terrestrial environment. The second half summarizes the results of an intercomparison exercise undertaken using four models to inform the direction of future research.

This publication describes the practices and challenges related to risk aggregation for various hazards, various operational states, and considering all sources of potential radioactive releases at a nuclear installation site. It provides a methodology and technical basis for risk aggregation and describes the good practices and practical examples of risk aggregation developed by IAEA Member States. The description of practices is supplemented by the detailed discussion on risk communication and use of aggregated risk results to support decision making processes.