Nuclear fusion has the potential of becoming a practically inexhaustible and almost clean energy source. The world’s efforts, in which Italy and Europe play a major role, focus on the confinement of a burning D-T plasma in devices based on superconducting magnets: the multi-billion ITER project, under construction at Cadarache in France, a few hundred kilometres from Torino, is scheduled to start operating in the late 20’s, while the EU is strongly pursuing the next step, i.e. a DEMO program, aiming at providing the first kWh from fusion.
This course gives an introduction to both the physics and the engineering of a nuclear fusion reactor of tokamak type. Some emphasis is put on the modelling aspects, at both the component and system level.
The course, mandatory for nuclear engineering students, could also be of interest for students who simply desire to get a somewhat more precise idea of the enormous potential of the fusion energy source.
Nuclear fusion has the potential of becoming a practically inexhaustible and almost clean energy source. Most of the world’s efforts, in which Italy and Europe play a major role, focus on the confinement of a burning D-T plasma in so-called tokamak devices, using superconducting magnets like: the multi-billion ITER project, under construction at Cadarache in France, a few hundred kilometres from Torino; the EU DEMO, aiming at providing kWh from fusion; the Divertor Tokamak Test (DTT) facility under construction at ENEA Frascati.
This course introduces the key engineering aspects of a nuclear fusion reactor of tokamak type, with a strong emphasis on the modelling of the main components and systems. The latter is also put in practice by including in the course an introduction to the Modelica language, used to model key tokamak sub-systems thanks to its flexibility, and then asking the students to use Modelica to develop simple engineering models of those sub-systems.
A few lectures will be dedicated to seminars held by renowned international experts in the field.
Visits to experimental facilities and factories are also foreseen.
The course, mandatory for nuclear engineering students, could also be of interest for students who simply desire to learn about the enormous potential of the fusion energy source.
The student should acquire a basic knowledge of the physics of magnetically confined plasmas in a tokamak-type fusion reactor, from an engineering point of view, as well as of the structure and functions of the main reactor components and of their integration in a consistent design.
The student should also acquire a critical perception of the main open issues and related perspectives of research and development in the field of fusion technology.
The students will acquire a basic knowledge of the structure and functions of the main reactor components, with special emphasis on the divertor, the blanket and the superconducting magnets, and of their integration in a consistent tokamak design.
The students will also acquire a critical perception of the main open issues and related perspectives of research and development in the field of fusion technology.
The students will also learn the fundamentals of the Modelica object-oriented programming language that, starting from the simple problems dealt with during the course, will allow them to model the main plant systems at different complexity levels.
The essential pre-requisite of the course is a good knowledge of the topics presented in the first two years of any Engineering BSc program.
An introduction to nuclear engineering (like that provided, e.g., in the course “Fondamenti di ingegneria nucleare”) could be helpful, but is not mandatory.
A useful pre-requisite is the course Nuclear Fusion Reactor Physics (or other introductory plasma/fusion physics course). It is also important to have a good knowledge of the topics presented in the first two years of any Engineering BSc program. Finally, an introduction to nuclear engineering (like that provided, e.g., in the course “Elementi di ingegneria nucleare” at Politecnico di Torino) could be helpful, but is not mandatory.
- Nuclear fusion in a nutshell
- The European roadmap on fusion electricity
- The course roadmap
- The key parameters and constraints for a 1 GWe fusion reactor of tokamak type:
- tau_E~ 1 s plasma confinement:
* motion of a single charged particle in the electromagnetic field
* definition of a plasma: Debye length, plasma frequency, quasi-neutrality
* MHD equilibrium and stability
* collisions in a plasma
* particle and energy transport
* performance of present tokamaks vs future reactors
# the superconducting magnet system and its cryogenics.
- T ~ 10-20 keV plasma heating:
* Ohmic; need for auxiliary heating (NNBI, RF); alpha.
- n ~ 1020-1021 m-3 plasma fueling:
# the fuel cycle the blanket (part 1) neutronics, choice of breeder/multiplier ITER TBM vs EU DEMO BB
# vacuum technology.
- limitations on heat flux q (MW/m2), and core plasma contamination (Z_eff) plasma-wall interactions:
* Debye sheath and Bohm criterion; impurities; Scrape-Off Layer, 2-point model
# limiter, first wall, divertor; engineering of power exhaust.
- Practical experience of small tokamak plasma operation (GOLEM)
- Power extraction and conversion the blanket (part 2) choice of coolant; storage; BoP
- Wrap-up
# ubiquitous/enabling technologies
- materials ( DONES/IFMIF)
- safety.
# ITER and satellites schedule; the current status of the EU DEMO design.
LECTURES
The structure and performance of present and forthcoming (under construction) tokamaks vs. future nuclear fusion reactors. The European roadmap on fusion electricity. The landscape of private fusion initiatives around the world. The course roadmap.
The three fundamental challenges of fusion engineering:
A. Managing the power and particle exhaust from the plasma, while controlling impurities at the same time
o Power balance and plasma-surface interactions in tokamaks
o The Scrape-Off Layer
o Limiter, First Wall (FW), Divertor
o Sputtering and the Lawson criterion with impurities
o Heat transfer enhancement in high heat flux tokamak components
o The divertor problem in DEMO perspective
o The Liquid Metal Divertor (LMD)
Auxiliary heating of the plasma: Neutral Beam Injection, …
B. Extracting the power deposited in the blanket by the neutrons, while breeding the tritium fuel
o The blanket and its main functions
o Load conditions on FW/blanket
o Tritium consumption and production (needs)
o Choice of breeder/multiplier, coolant, structural material, and assessment of their compatibility
o EU-DEMO Breeding Blanket (BB) designs: HCPB, WCLL
o The ITER TBM program vs. the EU-DEMO BB
o BB Maintenance and Balance of Plant (BoP)
o Advanced BB concepts
The Fusion Fuel Cycle: Vacuum Pumping, Tritium extraction, Matter Injection
C. Confining a 10^8 K plasma using powerful superconducting (SC) magnets, while keeping them at 4.5 K
o Introduction: The tokamak magnet system; Magnet electro-mechanics; Why SC magnets?; Superconductivity fundamentals; SC magnets; Cooling SC magnets. Cryogenics and thermophysical properties of materials at cryogenic conditions vs. RT; Current-sharing temperature, stability, quench
o Low-Tc vs. high-Tc superconductors
o Winding a SC magnet: strands, cable-in-conduit conductors
o Modeling SC magnets: The 4C code.
Introduction to the safety of nuclear fusion reactors.
LABORATORY
0. Introduction to the Modelica language: fundamentals; the Modelica Standard Library; the ThermoPower library.
1. Simulation of the refill circuit of a possible Liquid Metal Divertor for the EU DEMO
• Modelling the refill circuit with existing models (e.g. from the ThermoPower library)
• Development of a model of an LMD target for the EU DEMO
• Transient analysis of the LM refill circuit
2. Modelling the Breeding Blanket First Wall
• Development of a Modelica model of the solid structure in the EU DEMO FW
• Thermal-hydraulic model of the FW and its cooling channels
• Analysis of the FW cooling under different heat loads
3. Modelling the cryogenic and superconducting magnet systems
• Development of a Modelica model of a control valve
• Development of a model of the CEA HELIOS facility
• Dynamic simulation of the pulsed heat load smoothing in the HELIOS facility and comparison with experimental data
Physics
The course will consist of theoretical lectures and of the practical solution of simple numerical problems.
The students will also have the opportunity to perform an experimental session on a small tokamak.
Engineering
The course will consist of theoretical lectures and of the demonstration of dedicated software on a few specific topics (superconducting magnets, breeding blanket and power exhaust) to the students, who will also have the opportunity to use it.
About 50/80 hours will consist of theoretical lectures on the above-mentioned topics. The rest of the hours will be devoted to a course on the Modelica computer language and to the script development for and application of simple Modelica models to the three key engineering challenges A-C above.
Physics
Reference textbooks
• J.P. Freidberg, Plasma Physics and Fusion Energy, Cambridge University Press, 2007
• Peter C. Stangeby, The Plasma Boundary of Magnetic Fusion Devices, Institute of Physics Publishing, 2000
Auxiliary books
• C. Wendell Horton, Jr. and S. Benkadda, ITER Physics, World Scientific, 2015.
Engineering
A few good references are available, see e.g.
• Thomas J. Dolan (Editor), “Magnetic Fusion Technology (Lecture Notes in Energy)”, Springer; 2013 edition (February 10, 2014), ISBN 978-1447155553
• Weston M. Stacey, “Fusion: An Introduction to the Physics and Technology of Magnetic Confinement Fusion” 2nd Edition, Wiley-VCH (March 22, 2010), ISBN 978-3527409679.
However, no single textbook really covers the scope of topics to the needed depth for this course. We shall therefore often rely on presentations from summer schools (e.g. the KIT International School on Fusion Technologies http://summerschool.fusion.kit.edu/ ) and on presentations given at international conferences, as well as on papers published on international journals like Fusion Engineering and Design, Fusion Science and Technology, etc.
A few general references are available, see e.g.
• Thomas J. Dolan (Editor), “Magnetic Fusion Technology (Lecture Notes in Energy)”, Springer; 2013 edition (February 10, 2014), ISBN 978-1447155553
• Weston M. Stacey, “Fusion: An Introduction to the Physics and Technology of Magnetic Confinement Fusion” 2nd Edition, Wiley-VCH (March 22, 2010), ISBN 978-3527409679.
However, no single textbook really covers the above-mentioned topics to the needed depth for this course. The instructors will therefore provide additional material in the form of slides used in class, as well as rely on presentations from summer schools and international conferences, as well as on papers published on international journals like Fusion Engineering and Design, Fusion Science and Technology, etc.
On-line free guides of the Modelica language are also available: https://www.modelica.org/modelicalanguage, Modelica By Examples (https://mbe.modelica.university/).
Dispense;
Lecture notes;
Modalità di esame: Prova scritta (in aula); Prova orale obbligatoria; Elaborato scritto prodotto in gruppo;
Exam: Written test; Compulsory oral exam; Group essay;
...
The exams for the two parts are separate. The final score will be the average of the two.
Physics
The final exam is in two parts, the first (mandatory) is written, the second is an oral discussion.
The written test, of duration about 1.5 h, involves a number of numerical problems and theoretical questions. It aims at verifying that the student can (i) complete successfully some simple calculations, and (ii) can critically discuss the simplest phenomena occurring in a fusion reactor. The students will be allowed to use a pocket computer, but no another material will be allowed, except what provided by the instructor. The maximum score which can be obtained from the written test is 27/30.
Students who obtained a score equal or higher than 26/30 in the written test may ask to also have an oral discussion, during which the level of comprehension of the physical processes discussed during the main lectures will be verified in depth.
Engineering
For all students, an oral exam about the different topics treated in the course, will lead to a maximum mark of 24/30.
For those students who aim at a maximum mark above 24/30, the oral will be followed by a presentation (in ppt form), of the estimated duration of ~ 10 minutes, on the results of a small project, based on the application of the software presented in class, in either of the following three fields at the students’ choice: 1) superconducting magnets; 2) breeding blanket; 3) power exhaust. The presentation will be valued up to an additional 6 points and will be considered for a possible final mark of 30 cum laude.
Gli studenti e le studentesse con disabilità o con Disturbi Specifici di Apprendimento (DSA), oltre alla segnalazione tramite procedura informatizzata, sono invitati a comunicare anche direttamente al/la docente titolare dell'insegnamento, con un preavviso non inferiore ad una settimana dall'avvio della sessione d'esame, gli strumenti compensativi concordati con l'Unità Special Needs, al fine di permettere al/la docente la declinazione più idonea in riferimento alla specifica tipologia di esame.
Exam: Written test; Compulsory oral exam; Group essay;
The exam is in three parts:
1) A computational laboratory part, consisting of the preparation of a brief report ($) on the application of the above-mentioned Modelica script (to be prepared in self-organized groups of 2 students)
2) A written part, consisting of two open questions on the course topics
3a) If (1/3 * Modelica + 2/3 * written) < 27/30 --> final mark = 1/3 * Modelica + 2/3 * written
3b) If (1/3 * Modelica+ 2/3 * written) ≥ 27/30, an oral exam will follow --> final mark = max {(25% * Modelica+ 50% * written + 25%*oral), 26/30}
($) The Modelica report must be submitted at least 3 days before the written exam
In addition to the message sent by the online system, students with disabilities or Specific Learning Disorders (SLD) are invited to directly inform the professor in charge of the course about the special arrangements for the exam that have been agreed with the Special Needs Unit. The professor has to be informed at least one week before the beginning of the examination session in order to provide students with the most suitable arrangements for each specific type of exam.