This publication is the result of an IAEA technical meeting and reports on Member States’ capabilities in modelling, predicting and improving their understanding of the behaviour of nuclear fuel under accident conditions. The main results and outcomes of a coordinated research project (CRP) on this topic are also presented.

This publication draws on the work carried out during an IAEA coordinated research project to benchmark computational fluid dynamics (CFD) codes used in fuel assembly design and model options and methods against ‘CFD quality’ experimental data under single phase flow conditions. It presents the results obtained by seven participating institutes from six Member States, all with currently operating water cooled reactors. The publication provides a description of the omni flow experimental loop test facility used for benchmark experiments related to the phenomena of fuel assembly spacer grid induced flow mixing. The focus of the benchmark was on the downstream region after the spacer grid. The comparisons between the experimental measurements and the CFD calculations are hence focused on the average velocity, the fluctuating velocity (turbulence), and local cladding temperatures in this region.

This publication presents a set of examples of different approaches for estimating potential exposures in different countries based on participants’ experience and considering the IAEA Safety Standard on a generic framework for consideration of radiological environmental impact, including potential exposures. It is intended to support the development of a common understanding in assessing the population health risks from potential accident scenarios in a nuclear power plant. This publication will contribute to further improvement of the INPRO (International Project on Innovative Nuclear Reactors and Fuel Cycles) methodology for sustainability assessment of nuclear energy systems (NESs) and can help Member States applying this methodology to perform a NES assessment in the areas of safety and environment. The publication is intended for use by organizations involved in development and deployment of NESs including planning, design, modification, technical support and operation of nuclear power plants.

This publication provides a description of the Rossendorf coolant mixing (ROCOM) test facility, used to provide benchmark experiments related to the phenomena of pressurized thermal shock (PTS) and boron dilution, the calculation results using computational fluid dynamics (CFD) codes and methods, and the conclusions drawn from comparison of CFD results with experimental measurements. The aim of this benchmarking was to provide CFD practitioners with two high quality datasets of relevance to reactor transients inside a pressurized water reactor pressure vessel with different configurations and involving mixed convection, stratification, jet impingement and unsteady (inverse) plumes. The focus of the benchmarking was on the three main regions of the cold domain of the primary circuit, i.e. the cold leg, the downcomer and the core entry region. The work was carried out within the framework of an IAEA coordinated research project on application of computational fluid dynamics codes to nuclear power plant design.

This publication describes the general concept of using quantitative and qualitative information to be integrated in making safety related decisions. By following this approach, the balanced decision option could be selected in a systematic and traceable manner. The publication also provides practical insights on the selection of the various factors that could be included in the integrated risk informed decision making (IRIDM) process and provides suggestions on how the integration of the factors can be performed. Practical issues and challenges that need to be addressed in adopting an IRIDM approach are also discussed. Some examples of decision making are reviewed against the IRIDM framework to show how the process has been used or can be used.

This publication provides guidance and recommendations to nuclear organizations by offering a practical approach to assessing the behavioural competencies for safe, secure and effective performance across the nuclear workforce. It outlines a variety of tools and approaches that can aid the behavioural assessment processes and provides both general and role-specific recommendations to improve the quality of selection, promotion, training and development decisions. Also addressed in the publication are challenges, key issues and critical considerations for assessment practices. This guidance can be used by Member States as a foundation upon which to develop or improve a comprehensive behavioural competency assessment programme and contribute to building a sustainable nuclear workforce comprised of high performing nuclear professionals.

This publication results from a technical meeting on phenomenology and technologies relevant to in-vessel melt retention (IVMR) and ex-vessel corium cooling (EVCC). The purpose of the publication is to capture the state of knowledge, at the time of that meeting, related to phenomenology and technologies as well as the challenges and pending issues relevant to IVMR and EVCC for water cooled reactors by summarizing the information provided by the meeting participants in a form useful to practitioners in Member States.

This publication elaborates the technical basis for the use of seismic isolation systems in nuclear installations. There are many benefits of seismic isolation in design and construction of new facilities and in the retrofitting of existing nuclear installations. Observations of well-designed, installed and maintained isolated structures show a no damage behaviour that corresponds to expectations. This publication presents the current status of practice and use of seismic isolation systems for nuclear installations. Since it relates to a number of IAEA Safety Standards, it complements these on the technical aspects related to usage of seismically isolation for structures, systems and components in nuclear installations. It will be of interest to all those concerned with seismic analysis, seismic design, and seismic safety evaluation for such installations

This publication presents the outcome of an IAEA coordinated research project titled Pathways to Energy from Inertial Fusion: Materials beyond Ignition, and reports on the research work accomplished within the framework of the project. The main objective was to provide an assessment of the material requirements, consequences and characteristic behaviours in pulsed, repetitively cycled inertial fusion energy systems. Focusing on materials characterization, physics and target design for direct drive operation, and experimental infrastructure development, the publication contains additional relevant technical details and includes conclusions regarding future research activities and a review of past and ongoing efforts.

This publication evaluates the different coolant options considered for nuclear applications with a fast neutron spectrum (i.e. fusion, fission and accelerators), compiles the latest information in the field and identifies research needs. In this study, systems cooled by light and heavy liquid metals, molten salts, as well as gas and water choices are analysed and discussed. This TECDOC documents the present state of knowledge in the area of fusion, fission and accelerator applications, and the major progress in methods and approaches made in the past years based on observations, experimental findings and operational experience. Moreover, it identifies knowledge gaps and addresses near term research and development efforts required to overcome them.

This publication describes and summarizes the work of the MODARIA (modelling and data for radiological impact assessments) Programme Working Group 6. MODARIA was set up to continue the IAEA's activities in the field of testing, comparing and developing guidance on the application of models to assess radiation exposures to humans and radiological impacts on the environment. Different aspects of the MODARIA programme were addressed by ten working groups. MODARIA WG 6 had the remit of developing a common framework for addressing climate and environmental change in post-closure radiological assessments of solid radioactive waste disposal. The intention was to include a wide range of disposal facility types. An additional goal of WG 6 was to further develop the understanding of how the biosphere may develop from the present into the far future in a wide range of regional and local contexts relevant to the disposal of solid radioactive wastes. While the focus of MODARIA is dose assessment, the methodology and results of WG 6 may be valuable in a wider safety assessment context, for example for other types of facilities and sites.

This publication provides guidance for assessing the sustainability of a nuclear energy system (NES) in the area of nuclear fuel cycle facility (NFCF) safety. It deals with NFCFs that may be potentially involved in the NES such as, mining, milling, refining, conversion, enrichment, fuel fabrication, spent fuel storage, and spent fuel reprocessing facilities. It augments the information presented in the earlier INPRO publications on the methodology for sustainability assessments. The publication is intended for use by organizations involved in the development and deployment of a NES, including planning, design, modification and technical support for NFCFs.