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The realization of the Divertor Tokamak Test (DTT) facility is one of the key milestones of the European Roadmap, aiming to explore alternative power exhaust solutions for DEMO, the first nuclear-fusion power plant that will be connected to the European grid. For the actual implementation of the DTT and DEMO plants, it is necessary to define the structure of the internal electric power distribution system, able to supply unconventional loads with a sufficient level of reliability. The present paper reports the preliminary studies for the feasibility and realization of the electrical power systems of DTT, describing the methodology adopted to obtain a first distribution configuration and providing some simulation results. In particular, the first stage of the study deals with the survey and characterization of the electrical loads, which allows defining a general layout of the facility and size the main electrical components. To verify the correctness of the assumptions, simulation models of the grid were implemented in the DIgSILENT PowerFactory software in order to carry out power flow and fault analyses. [ABSTRACT FROM AUTHOR]

Plasma properties can be useful in a wide spectrum of applications. Experimental projects on controlled nuclear fusion are the most challenging of these applications and, at the same time, the best way to approach plasma science. Since nuclear fusion reactors can ensure a large-scale, safe, environmentally-friendly and virtually inexhaustible source of energy, several fusion-oriented megaprojects and innovative companies are appearing all over the world. PROTO-SPHERA (Spherical Plasma for HElicity Relaxation Assessment) is the first plasma project with a simply connected configuration, namely not requiring additional objects inside the plasma volume. This is obtained by a plasma arc, shaped as a screw pinch, acting as the centerpost of a spherical torus with minimal aspect ratio. Due to its intrinsic physical, engineering and economic advantages, this new approach is attractive also on an industrial scale and with several developments that still needs to be explored. This paper presents the PROTO-SPHERA basic principles, its first encouraging results and its expected and potential evolutions. [ABSTRACT FROM AUTHOR]

EU-DEMO is a European project, having the ambitious goal to be the first demonstrative power plant based on nuclear fusion. The electrical power that is expected to be produced is in the order of 700–800 MW, to be delivered via a connection to the European High Voltage electrical grid. The initiation and control of fusion processes, besides the problems related to the nuclear physics, need very complex electrical systems. Moreover, also the conversion of the output power is not trivial, especially because of the inherent discontinuity in the EU-DEMO operations. The present article concerns preliminary studies for the feasibility and realization of the nuclear fusion power plant EU-DEMO, with a special focus on the power electrical systems. In particular, the first stage of the study deals with the survey and analysis of the electrical loads, starting from the steady-state loads. Their impact is so relevant that could jeopardy the efficiency and the convenience of the plant itself. Afterwards, the loads are inserted into a preliminary internal distribution grid, sizing the main electrical components to carry out the power flow analysis, which is based on simulation models implemented in the DIgSILENT PowerFactory software. [ABSTRACT FROM AUTHOR]

Towards the middle of the current century, the DEMOnstration power plant, DEMO, will start operating as the first nuclear fusion reactor capable of supplying its own loads and of providing electrical power to the European electrical grid. The presence of such a unique and peculiar facility in the European transmission system involves many issues that have to be faced in the project phase. This work represents the first study linking the operation of the nuclear fusion power plant DEMO to the actual requirements for its correct functioning as a facility connected to the power systems. In order to build this link, the present work reports the analysis of the requirements that this unconventional power-generating facility should fulfill for the proper connection and operation in the European electrical grid. Through this analysis, the study reaches its main objectives, which are the definition of the limitations of the current design choices in terms of power-generating capability and the preliminary evaluation of advantages and disadvantages that the possible configurations for the connection of the facility to the European electrical grid can have. In reference to the second objective, the work makes possible a first attempt at defining the features of the point of connection to the European grid, whose knowledge will be useful in the future, for the choice of the real construction site. [ABSTRACT FROM AUTHOR]

The nuclear fusion project JT-60SA is presently under construction in Naka (Japan) as a joint collaboration between Europe and Japan, within the framework of the Broader Approach Agreement. According to such agreement, the various JT-60SA systems are supplied by European and Japanese institutions. In particular, the Italian Agency ENEA was in charge for the procurement of the four Switching Network Units (SNUs) for the JT-60SA Central Solenoid (CS). The main SNU function is to interrupt a DC current up to 20 kA in a short time (less than 1 ms) in order to produce an overvoltage of up to 5 kV, crucial to generate and sustain the fusion plasma. The SNU design, manufacturing and factory test activities have been completed in 2016. After the delivery in Naka, the four SNUs have been installed and successfully commissioned in 2017. After an overview on the main technical characteristics of the SNUs and the key aspects of their design, this paper describes the activities performed on-site, highlighting the results obtained during the final acceptance tests and comparing them with the design simulation and the factory test results. [ABSTRACT FROM AUTHOR]

ECRH&CD systems are extensively used on tokamak plasmas due to their capability of highly tailored power deposition, allowing very localised heating and non-inductive current drive, useful for MHD and profiles control. The high electron temperatures expected in DEMO will require ECRH systems with operating frequency in the 200–300 GHz range, equipped with a reasonable number of high power ( P ≥ 1 MW) CW RF sources, for allowing central RF power deposition. In this frame the ENEA Fusion Department (Frascati) is coordinating a task force aimed at the study and realisation of a suitable high power, high frequency reliable source. [ABSTRACT FROM AUTHOR]

• DTT is a facility under construction in ENEA research centre and its part of European nuclear fusion research. • Fast Discharge Unit is a safety key component for the protection of the Superconducting Toroidal Field Coils through a discharge on Dump Resistors. • A new study with a switched Dump Resistor has been carried out with a result of a linear discharge and better performances. • A Fault Analysis has been carried out in order to evaluate the behaviour of the system with multiple faults. The paper is focused on the optimal design of Fast Discharge Unit (FDU) for the quench protection of the Toroidal Field (TF) magnets of the Divertor Tokamak Test facility (DTT), an experimental facility under construction in ENEA Frascati Research Centre (Rome, Italy). The FDU is a safety key component that protects the superconducting magnets when a quench is detected through the fast extraction of the energy stored in the magnets by adding a discharge dump resistor (DR) in the TF magnets circuit. A comparison between a fixed DR and a switched variable DR has been implemented by changing resistor parameters and by using multiple current control of the power electronics components (IGCTs). The new configuration allows to reduce the maximum voltage and the thermal stresses both for superconducting magnets and for FDUs (Fast Discharge Units), so reducing the insulation level of all TF (Toroidal Field) coil circuits, including also the power supply, reducing the hotspot temperature on the TF coils and the specific energy through them. Another advantage of the proposed configuration is the reduction of the size of all electrical devices of TF coil circuits so achieving a more effective and reliable design, also decreasing the overall costs. [ABSTRACT FROM AUTHOR]