Politecnico di Torino
Anno Accademico 2017/18
Nuclear Technologies
Corso di Laurea Magistrale in Ingegneria Energetica E Nucleare - Torino
Docente Qualifica Settore Lez Es Lab Tut Anni incarico
Zucchetti Massimo ORARIO RICEVIMENTO PO ING-IND/19 48 12 0 0 2
SSD CFU Attivita' formative Ambiti disciplinari
ING-IND/19 6 D - A scelta dello studente A scelta dello studente
The aim of course is provide students with the knowledge to understand the issues of manufacturing and choice of materials in the design of components and systems found in nuclear energy systems.
Properties of materials used in fission and fusion energy systems and radiation damage in nuclear fuels and structural materials.
Risultati di apprendimento attesi
The student will get the capability of assessing the materials and technology issues of nuclear systems. The student will know facts about nuclear materials; will know the functions they perform, the mechanisms of radiation damage, and criteria for materials selection in nuclear engineering design.
Prerequisiti / Conoscenze pregresse
Basic knowledge of nuclear facilities and of science and technology of materials.
Key technologies for present-day and future advanced nuclear energy reactor systems encompass high temperature structural materials, fast neutron resistant core materials, and specific reactor and power conversion technologies (intermediate heat exchanger, turbo-machinery, high temperature electrolytic or thermo-chemical water splitting processes, etc.). Beyond the commercialization of best available nuclear reactor technologies now, it is essential to start now the development of breakthrough technologies that will be needed to prepare the longer term future for nuclear power:. These innovative systems include fast neutron reactors with a closed fuel cycle, high temperature reactors that could be used for process heat applications and fusion experimental and demonstration devices.
Contents are divided in 5 units (see below for details).
1. Review of present-day and advanced nuclear energy reactor systems and the main requirements for the materials to be used.
2. Basic and advanced theoretical and modeling principles, dealing with nuclear materials issues.
3. Conventional nuclear materials and their main issues.
4. Materials for advanced nuclear energy systems
5. Radiation damage to fission and fusion structural materials

Unit 1.
Unit 1 will briefly review present-day and advanced nuclear energy reactor systems and the main requirements for the materials to be used. Generation II and III nuclear power reactors. Generation IV nuclear reactors (fast neutron reactors - sodium, gas or lead cooled - with a closed fuel cycle, high temperature reactors, etc.). Other innovative systems (thermal or fast neutron spectrum supercritical water reactors and thorium fueled molten salt reactors). Accelerator Driven Systems (ADS). Fusion reactors, both experimental – ITER – and Demonstration – DEMO – projects and designs.The main requirements for the materials to be used include the follwing. Dimensional stability under irradiation, whether under stress (irradiation creep or relaxation) or without stress (swelling, growth). Acceptable evolution under ageing of the mechanical properties (tensile strength, ductility, creep resistance, fracture toughness, resilience). Good behavior in corrosive environments (reactor coolant or process fluid). Other criteria for the materials are their cost to fabricate and to assemble, and their composition could be optimized in order for instance to present low-activation (or rapid desactivation) features which facilitate maintenance and disposal. These requirements have to be met under normal operating conditions, as well as in incidental and accidental conditions.

Unit 2.
Basic and advanced theoretical and modeling principles, dealing with nuclear materials issues, will be reviewed in Unit 2. Crystal structure of solids; point defect types and structures. Equilibrium concentrations of point defects in crystals. Diffusion in solids: Fick’s law; atomic mechanisms. Dislocations in solids. Mechanical properties of metals. Cavities in solids: pores, bubbles, and voids. Fission product behavior in nuclear fuel; swelling and release. Polycrystalline solids; sintering and grain growth. Radiation damage in metals. Fast-neutron irradiation effects in metals. Irradiation creep. Aqueous corrosion (uniform corrosion, boric acid corrosion, flow accelerated corrosion, and/or erosion corrosion). Localized corrosion (crevice corrosion, pitting, galvanic corrosion, and microbiologically influenced corrosion). Environmentally assisted cracking (intergranular stress-corrosion cracking, transgranular stress corrosion cracking, primary water stress corrosion cracking, irradiation-assisted stress corrosion cracking (IASCC) and low-temperature crack propagation). Introduction of a nanoscale particles for designing high-performance radiation-resistant materials, to provide good high temperature strength and neutron radiation damage resistance.

Unit 3.
Conventional nuclear materials and their main issues are reviewed in Unit 3. The safe and economical operation of any nuclear power system relies to a great extent, on the success of the fuel and the materials of construction. For instance, a typical Light Water Reactor (LWR) contains numerous types of materials (Fig. 1) that must all perform successfully. During the lifetime of a nuclear power system the materials are subject to high temperature, a corrosive environment, and damage from high-energy particles released during fission. Fuel has a short life but is subject to the same types of harsh environments. Fuel cladding (zirconium alloys), with key concerns that include oxidation, hydriding, build-up of low thermal conductivity corrosion deposits, and effect of hydrogen on cracking and corrosion. Structural internals: austenitic stainless steel and Ni-base alloys (X-750). Pressure vessel (quenched and tempered Mn-Mo-Ni low-alloy steel), where key concern is loss of fracture toughness due to radiation-induced defect cluster hardening and radiation-induced precipitation, and embrittlement. Piping and heat exchanger materials (ferritic steels and Ni-base alloys such as Alloy 600 and 690), where key concerns include thermal aging and complex water chemistry issues that may induce corrosion or stress corrosion cracking. Many GEN II and III reactors are extending their operating licenses from 40 to 60 years, or even more, implying higher and unprecedented radiation exposures that can be an issue.

Unit 4
The challenging requirements for innovative energy systems imply that in most cases, the use of conventional nuclear materials is excluded, since they anticipate operation at radiation exposures and temperatures, again beyond current nuclear industry experience, as well as most previous experience with developmental systems. Unit 4 gives a brief overview of various materials that are essential to establish advanced systems feasibility and performance, such as ferritic/martensitic steels (9–12% Cr), nickel based alloys (Haynes 230, Inconel 617, etc.), oxide dispersion strengthened ferritic/martensitic steels, and ceramics (SiC, TiC, etc.). Innovative materials for ITER: first wall, blanket, breeders, divertor, magnets. High-performance structural materials for DEMO fusion reactor, are subject to unprecedented fluxes of high-energy neutrons along with intense thermomechanical stresses and high temperature coolants that may induce corrosion; steady-state heat fluxes for first-wall and divertor components in proposed magnetically-confined fusion energy reactors are substantially higher than the highest heat flux for structural materials in fission reactors. The design lifetime doses for the first wall and blanket structural materials are about five times higher than the core internal structures for existing fission reactors. In addition, the high average neutron energy associated with the deuterium-tritium fusion reaction compared to fission tends to produce much higher levels of transmutant solutes such as H and He in the structural materials that generally magnify radiation-induced degradation processes. A key additional constraint for fusion structural materials is the international mandate for intrinsic safety (i.e., no public evacuation in case of a loss of coolant accident) and minimal long-term environmental impact (i.e., no long-lived radioisotopes that would require deep geologic burial or equivalent sequestration) for the fusion reactor structures Consideration of this reduced-activation mandate, along with the requirement for high performance, leads to three major options for fusion structural materials. Ferritic/martensitic steel (where high activation solutes such as Mo and Nb in commercial steels are replaced by W and V), refractory alloys based on either vanadium or tungsten, SiC/SiC ceramic composites. Numerous issues including structural engineering design rules, how to achieve leak-tight boundaries for gas cooled systems, joining and other fabrication issues, radiation stability uncertainties, improvement of thermal conductivity (and minimization of radiation-induced degradation), and fabrication cost need further research and development to enable this materials system to achieve its full potential.

Unit 5.
Radiation damage to structural materials in fission and fusion reactors will be reviewed in Unit 5. Dimensional instabilities above a few percent generally cannot be tolerated in large-scale engineering structures and future reactor designs call for structural materials that will be exposed to damage levels in excess of 100 dpa (displacement per atom). Recombination of defects: vacancies and SIAs (self-interstitial atoms, SIAs). Engineered "self-healing" defect recombination. Radiation damage poses five main threats to the operation of structural materials, emerging at different operating temperatures and damage levels. At low temperatures (below 0.3–0.4 TM, absolute melting temperature), radiation-induced defect clusters (predominantly created directly in displacement cascades) serve as strong obstacles to dislocation motion. At intermediate temperatures, three distinct radiation effects phenomena are of potential significance for doses above ∼1 to 10 dpa: radiation-induced segregation and precipitation (0.3–0.6 TM) that can lead to localized corrosion or mechanical property degradation such as grain boundary embrittlement, void swelling from vacancy accumulation (0.3–0.6 TM) that can create unacceptable volumetric expansion, and radiation induced creep and/or anisotropic growth (0.2–0.6 TM) that can produce dimensional expansion along directions of high stress and/or specific crystallographic directions. At very high temperatures (>0.5 TM) and under applied mechanical stress, helium produced by neutron transmutation reactions in the structural material may migrate to grain boundaries and form cavities, thereby causing intergranular fracture with limited ductility in stressed materials. This high temperature helium embrittlement of grain boundaries typically emerges for helium concentrations above 10 to 100 appm (∼1 to 100 dpa depending on material and neutron spectrum) and becomes increasingly severe with increasing temperature and applied stress and decreasing deformation rate.
Organizzazione dell'insegnamento
For each unit of the course, presentations, self-teaching and reading materials are available online.
Attending the class is recommended, but not strictly necessary.
Testi richiesti o raccomandati: letture, dispense, altro materiale didattico
Presentations and reading materials available online.

D. R,. Olander, Fundamental Aspects of Nuclear Reactor Fuel Elements, TID-26711-P1, 1976, Technical Information Center, Office of Public Affaire, Energy Research and Development Administration
J. Gittus, Irradiation Effects in Crystalline Solids, Appl. Sci. Pub. Ltd., London (1978)
Criteri, regole e procedure per l'esame
Discuss a report relating to a class of materials used in nuclear power plants with characterization of thermo- physical properties, thermo-mechanical, technological, uses, operating conditions, the effects of irradiation, the method of processing or preparation of the components in the preparation of material for use in the nuclear field.
Numerical exercises for the evaluation of the properties of materials and / or for the study of radiation damage
Orario delle lezioni
Statistiche superamento esami

Programma definitivo per l'A.A.2017/18

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