Structural Materials for Generation IV Nuclear Reactors

Pascal Yvon

• Publisher: Woodhead Publishing
• Year: 2016
• ISBN:
  9780081009123
• Topic: Technology & Engineering
• Subtopic: Industrial Health & Safety
• Index: Technology & Engineering

Operating at a high level of fuel efficiency, safety, proliferation-resistance, sustainability and cost, generation IV nuclear reactors promise enhanced features to an energy resource which is already seen as an outstanding source of reliable base load power. The performance and reliability of materials when subjected to the higher neutron doses and extremely corrosive higher temperature environments that will be found in generation IV nuclear reactors are essential areas of study, as key considerations for the successful development of generation IV reactors are suitable structural materials for both in-core and out-of-core applications. Structural Materials for Generation IV Nuclear Reactors explores the current state-of-the art in these areas. Part One reviews the materials, requirements and challenges in generation IV systems. Part Two presents the core materials with chapters on irradiation resistant austenitic steels, ODS/FM steels and refractory metals amongst others. Part Three looks at out-of-core materials.

Structural Materials for Generation IV Nuclear Reactors is an essential reference text for professional scientists, engineers and postgraduate researchers involved in the development of generation IV nuclear reactors.

• Introduces the higher neutron doses and extremely corrosive higher temperature environments that will be found in generation IV nuclear reactors and implications for structural materials
• Contains chapters on the key core and out-of-core materials, from steels to advanced micro-laminates
• Written by an expert in that particular area

1

Introduction to Generation IV nuclear reactors

D. Buckthorpe The University of Manchester, Manchester, United Kingdom

Abstract

The next generation (Generaton IV) of fission reactor systems will impose significant challenges on materials and component development because of the need to look at new material options, properties, and manufacturing capabilities to meet the needs of these new reactors. This chapter summarizes the six Generation IV reactor systems and their requirements and technical challenges with respect to materials. These include the gas-cooled, liquid metal-cooled, water-cooled, and molten salt-cooled systems. Demand over the last few decades for the development of higher temperature and alternative material solutions for these systems has been low and needs to be accelerated. A clearly defined target application for each reactor systems needs to be developed, with specific manufacturers invited and supported and encouraged to work alongside researchers to provide industrially developed solutions for these future reactor needs.

Keywords

Competetiveness; Cooling system; Fission; Generation IV nuclear reactors; Materials; Nuclear; Reliability; Safety

1.1. Introduction: the need for new nuclear systems

Nuclear energy is an important contributor to the global objective of developing low-carbon energy technologies for current and future generations. As the Earth's population continues to grow, so will the demand for energy and the benefits that it brings: improved standards of living, better health and longer life expectancy, improved literacy and opportunity. Faced with a need to change the world energy technology mix to respond to the challenges of greenhouse gases, decarbonization and security of energy supply, and of limiting growing world temperature changes to lower levels, new-generation reactors will be needed that are cleaner and more efficient, cost-competitive, and capable of providing a future energy supply that can satisfy and adjust to the growing and changing needs of populations. Such technologies will need to have favorable and improved safety characteristics, be capable of operating with improved resource utilization and have a whole-life capability, including reduced impact of waste, which takes full benefit from the design, development, and experiences of past prototype and commercial nuclear systems providing an effective alternative to the current range of energy-developing devices. The safe, reliable, and economic operation of nuclear reactors also depends upon the reliable operation of the reactor shutdown and regulation systems and its materials. In liquid metal-cooled fast reactors (LMFRs) for example, these consist of control assemblies, drive mechanisms, guide tubes, and other structural components. The safe shutdown of the reactor under all probable circumstances is an important requirement to ensure the prevention of core melt accidents and provide safe controlled shutdown behavior in all situations.

Reactor developments have evolved since the construction of the first-generation reactors (from the 1950s) to the present-day generation II and III systems. Within Europe and elsewhere this has involved the design and construction of commercial gas-cooled and water-cooled nuclear power stations many of which contribute to the national electricity supply. In the future, as the world's population continues to grow, and energy demands increase, with the proportion supplied by electricity growing ever faster, it is likely that electricity demand in the larger populated areas will continue to be served predominantly by extensive grid systems. In places where such grid systems have not yet developed, such as parts of China, India, and Africa, there could also be a strong trend toward distributed generation (i.e., generation close to the points of use) either as an intermediate development or as an alternative with the introduction of multimodular systems. Nuclear energy could also be used more extensively for cogeneration of heat and power (CHP) or delivering heat to industrial processes (e.g., paper factories) and to district heating. With gas or steam as the heat transfer medium, such reactors can achieve attractive conditions, which can compete with modern or conventional cogeneration plants which are in use in many industrial CHP applications.

Currently, nuclear power plants operating around the world produce a significant proportion of the world's electricity and provide the largest share of today's nongreenhouse-gas-emitting power source. These existing nuclear systems therefore provide a major reduction in the environmental impact of today's electric generation. To continue and expand this benefit, new next-generation systems will need to be designed and developed to replace and supersede plants as they retire providing less and less pollution and waste to the environment. Such new nuclear systems, called Generation IV systems [1], are being examined and developed as part of a technology roadmap [2] within an international forum, called the Generation IV International Forum (GIF) with the work focusing on the nuclear reactor and its energy conversion systems as well as the facilities associated with the fuel cycle and its extraction and waste disposal which are important for whole-life capability and performance.

1.2. Generation IV requirements and technical challenges

The GIF identified four areas important for the long-term deployment and operation of nuclear systems. An important conclusion was that the next generation of nuclear designs and developments should specifically address four areas of technology to help and ensure that nuclear energy plays an important and essential role in the world's future energy generation. The four priority areas of technology or requirements to focus on are:

• development of sustainable nuclear energy

• maintaining or increasing competitiveness

• improving and enhancing safety and reliability

• ensuring proliferation resistance and physical protection.

These are discussed further in the following sections.

1.2.1. Development of sustainable nuclear energy

At one time, sustainability was thought of only in terms of the efficient utilization of resources, in other words, high availability relative to the rate of fuel and operational use. Today, in the context of concerns about global warming, other aspects are also considered important. Within the Generation IV roadmap [3], sustainability goals are also defined with a focus on waste management and minimizing environmental effects. Other issues of importance include safety, energy security, the affordability of the electricity produced and maximizing options available to future generations. Sustainability is about meeting the needs of the present generation while enhancing the ability of future generations to meet society's needs into the future. The benefits of meeting sustainability goals include:

• Extending the nuclear fuel supply by recycling used fuel to recover its energy content;

• Enabling waste repositories to accept the nuclear waste from many more plant-years of operation through a substantial reduction in the amount of wastes and their decay heat produced;

• Greatly simplifying the scientific analysis and demonstrating safe repository performance for very long time periods by significantly reducing the lifetime and toxicity of the residual radioactive wastes sent to repositories for final disposal.

Disposing of discharged fuel or other high-level radioactive residues in a geological repository is the preferred choice of most countries, and good technical progress has been made in this area. Long-term retrievable surface or subsurface repositories are also being assessed. However, the extensive use of nuclear energy in the future requires the optimal use of repository space and the consideration of closing the fuel cycle. Most countries use a once-through fuel cycle, whereas others close the fuel cycle by recycling. Recycling (using either single or multiple passes) recovers uranium and plutonium from the spent fuel and uses it to make new fuel, producing more power and reducing the need for enrichment and uranium mining. Recycling in a manner that does not produce separated plutonium can further avoid proliferation risks. Recycling is not economical at present because there are plentiful supplies of uranium at low and stable prices. This could change, and closing the fuel cycle will be favored when the cost of maintaining an open cycle exceeds that of a closed cycle. With recycling, other benefits are also realized: the high-level radioactive residues occupy a much-reduced volume, can be made less toxic, and can be processed into a more suitable form for disposal. In addition, reactors can be designed to transmute troublesome long-lived heavy elements. Achieving these benefits, however, will require significant research and development (R&D) on the fuel cycle technology.

1.2.2. Maintaining or increasing competitiveness

Nuclear energy should strive to remain competitive against other forms of energy generation. Each energy system has its own set of benefits, costs, and risks (e.g., economic, environmental, and proliferation-related) and it is this set of attributes that will make a particular system competitive in relation to others. When considering new construction, the economic competitiveness of nuclear power is not obvious and will depend on the market structure and available alternatives, regulatory and investment climate and the overall electricity demand and its rate of growth. For future plant new developments can give rise to significant benefits in terms of competitiveness, plant operation, and in design and construction and operation:

• Achieving economic life-cycle and energy production costs through a number of innovative advances in plant and fuel cycle efficiency, design simplifications, and plant sizes;

• Reducing economic risk to nuclear projects through the development of plants built using innovative fabrication and construction techniques, and possibly modular designs;

• Allowing the distributed production of hydrogen, fresh water, district heating, and other energy products to be produced where they are needed.

In the past the economic performance of nuclear power has been mixed: on the positive side, the cost of nuclear power generation in many countries has been the same as or less than the cost of producing electricity from coal, oil, or natural gas. On the other hand, construction of advanced nuclear energy systems must address their economics in a variety of changing markets and overcome their traditionally high construction costs. While the current generation of plants generates electricity at competitive costs, construction costs are not competitive enough, and licensing needs to be mo...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Woodhead Publishing Series in Energy
• Introduction
• 1. Introduction to Generation IV nuclear reactors
• 2. Corrosion phenomena induced by liquid metals in Generation IV reactors
• 3. Corrosion phenomena induced by gases in Generation IV nuclear reactors
• 4. Corrosion phenomena induced by supercritical water in Generation IV nuclear reactors
• 5. Corrosion phenomena induced by molten salts in Generation IV nuclear reactors
• 6. Mechanical behavior of structural materials for Generation IV reactors
• 7. Irradiation effects in Generation IV nuclear reactor materials
• 8. Irradiation-resistant austenitic steels as core materials for Generation IV nuclear reactors
• 9. Irradiation-resistant ferritic and martensitic steels as core materials for Generation IV nuclear reactors
• 10. Oxide dispersion-strengthened/ferrite-martensite steels as core materials for Generation IV nuclear reactors
• 11. Refractory metals as core materials for Generation IV nuclear reactors
• 12. SiCf/SiC composites as core materials for Generation IV nuclear reactors
• 13. Carbon/carbon materials for Generation IV nuclear reactors
• 14. Graphite as a core material for Generation IV nuclear reactors
• 15. Absorber materials for Generation IV reactors
• 16. Advanced irradiation-resistant materials for Generation IV nuclear reactors
• 17. Conventional austenitic steels as out-of-core materials for Generation IV nuclear reactors
• 18. Conventional ferritic and martensitic steels as out-of-core materials for Generation IV nuclear reactors
• Index