Assessing nuclear energy transition scenarios requires appropriate modelling tools. The IAEA tool Model for Energy Supply System Alternatives and their General Environmental Impacts (MESSAGE) is described in this publication. The tool simulates the development of a complete energy system and provides a convenient platform for modelling and analysing nuclear energy systems (NES), as it can efficiently model nuclear technologies with their specific features. Among other things, the tool can help produce a description of an entire NES with time dependent parameters for long-term planning; confirm the feasibility of a NES through correlation and consistency of all NES components, taking into account all constraints and boundary conditions imposed on the system; balance fissile material in a close fuel cycle and determine fuel cycle requirements. In addition, it assists the user in the choice of alternatives by comparison of different options relating to fuel requirements and volume and toxicity of waste. The publication provides a detailed guidance on how to build mathematical models representing complex nuclear energy systems within the framework of the MESSAGE tool.

Member States have recognized the increasing need to model future nuclear power scenarios in order to develop strategies for sustainable nuclear energy systems. The IAEA model for energy supply strategy alternatives and their general environmental impacts (MESSAGE) code is a tool that supports energy analysis and planning in Member States. This publication documents the experience gained on modelling and scenario analysis of nuclear energy systems (NES) using the MESSAGE code through various case studies performed by the participating Member States on evaluation and planning for nuclear energy sustainability at the regional or national level. The publication also elaborates on experience gained in modelling of global nuclear energy systems with a focus on specific aspects of collaboration among technology holder and technology user countries and the introduction of innovative nuclear technologies. It presents country case studies covering a variety of nuclear energy systems based on a once-through fuel cycle and a closed fuel cycle for thermal reactors, fast reactors and advanced systems. The feedback from case studies proves the analytical capabilities of the MESSAGE model and highlight the path forward for further advancements in the MESSAGE code and NES modelling.

This book is intended as an introductory exposition of those nuclear energy systems concepts which are characterized by an integrated utiliz ation of complementary nuclear processes. Basic to such systems is the notion of synergism, which herein implies the cooperative interaction of selected nuclear reactions and system components so as to provide overall advantages not possible otherwise. While the concept of nuclear energy synergism has in recent years become the focus of an increasing number of conferences, scientific papers, and institutional in-house reports, no text which encompasses the major topics of the subject at a conceptual and analytical level has appeared. It is our aim to present a systematic characterization of these emerging nuclear energy concepts suitable for the senior university student of nuclear science and engineering as well for the active pro fessional involved in nuclear energy systems planning and analysis. In addressing the subject of nuclear energy synergism we have become most conscious of the tension between realism and vision in nuclear energy technology. As developed here, our perception of nuclear energy synergism is firmly rooted in the present and then seeks to proceed toward a heightened degree of compatibility and efficacy based on an enhanced integration of relevant nuclear processes. It is our view that such conceptual considerations must assume a greater role in the emerging techological orientation of nuclear energy systems planning.

Modelling of Nuclear Reactor Multiphysics: From Local Balance Equations to Macroscopic Models in Neutronics and Thermal-Hydraulics is an accessible guide to the advanced methods used to model nuclear reactor systems. The book addresses the frontier discipline of neutronic/thermal-hydraulic modelling of nuclear reactor cores, presenting the main techniques in a generic manner and for practical reactor calculations.The modelling of nuclear reactor systems is one of the most challenging tasks in complex system modelling, due to the many different scales and intertwined physical phenomena involved. The nuclear industry as well as the research institutes and universities heavily rely on the use of complex numerical codes. All the commercial codes are based on using different numerical tools for resolving the various physical fields, and to some extent the different scales, whereas the latest research platforms attempt to adopt a more integrated approach in resolving multiple scales and fields of physics. The book presents the main algorithms used in such codes for neutronic and thermal-hydraulic modelling, providing the details of the underlying methods, together with their assumptions and limitations. Because of the rapidly expanding use of coupled calculations for performing safety analyses, the analysists should be equally knowledgeable in all fields (i.e. neutron transport, fluid dynamics, heat transfer).The first chapter introduces the book's subject matter and explains how to use its digital resources and interactive features. The following chapter derives the governing equations for neutron transport, fluid transport, and heat transfer, so that readers not familiar with any of these fields can comprehend the book without difficulty. The book thereafter examines the peculiarities of nuclear reactor systems and provides an overview of the relevant modelling strategies. Computational methods for neutron transport, first at the cell and assembly levels, then at the core level, and for one-/two-phase flow transport and heat transfer are treated in depth in respective chapters. The coupling between neutron transport solvers and thermal-hydraulic solvers for coarse mesh macroscopic models is given particular attention in a dedicated chapter. The final chapter summarizes the main techniques presented in the book and their interrelation, then explores beyond state-of-the-art modelling techniques relying on more integrated approaches. - Covers neutron transport, fluid dynamics, and heat transfer, and their interdependence, in one reference - Analyses the emerging area of multi-physics and multi-scale reactor modelling - Contains 71 short videos explaining the key concepts and 77 interactive quizzes allowing the readers to test their understanding

Long-term energy system models - including electric sector capacity expansion models - are widely used tools for informing planning, technology assessment, and policy analysis. Recent decarbonization goals and rapid technological change have increased the need to appropriately represent economic characteristics and technical details of energy system resources, including variable renewable energy, energy storage technologies, carbon-capture-equipped capacity, and nuclear energy. Nuclear power represents about 20% of electricity generation and 50% of carbon-free electricity in the United States as of 2021. However, there are many perspectives on the role of existing and new nuclear in the future U.S. energy system, which is reflected in the broad range of potential contributions reported in the literature. This project aims to understand how issues central to nuclear energy are represented in long-term energy models. Building on earlier collaborations that focused on variable renewable energy and energy storage, this project convenes four modeling teams that use national-scale long-term energy system models from the Electric Power Research Institute, the National Renewable Energy Laboratory, the U.S. Energy Information Administration, and the U.S. Environmental Protection Agency to share methods and data, update models, run coordinated scenarios, and identify research needs. Improving tools can provide more insightful analyses and ensure that methods are more transparent.