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News Article | May 4, 2017

Nuclear fusion has long held out the promise of clean, safe energy but dealing with the extremely high temperatures generated in the reactors is no easy task. Now the UK’s nuclear fusion experiment MAST Upgrade, at Culham in Oxfordshire, is to receive £21m to investigate new technology to cool the extremely hot plasma exhaust produced by the reaction. Inside a fusion reactor, light atomic nuclei are fused together to form larger ones, releasing a huge amount of energy in the process. This is achieved by confining the gas within a magnetic field and then heating it to temperatures of around 150 million Celsius, according to Dr James Harrison, Tokamak science programme delivery manager at Culham Centre for Fusion Energy. The hot fusion plasma exhaust is then passed through an area of the reactor known as a “divertor” to allow it to dissipate some of this excess heat. However, the extremely high temperatures involved mean the exhaust particles would damage the surfaces of a conventional divertor, meaning components would require regular replacement, which adds to the cost of the electricity produced. “As the super-heated gas is gradually transported away from the hot fusion producing part of the machine into the area where it is exhausted, it comes into contact with solid surfaces of either tungsten or carbon, which are typically much closer to room temperature,” said Harrison. “The super-heated plasma can heat the surfaces, leading to gradual melting or erosion of the material over time.” So the fusion researchers are investigating the use of a new “Super X” divertor, which is designed to cool particles down by sending them on a longer exhaust path out of the plasma. “The Super X divertor aims to take the exhaust plasma, which has a very high density, and expand that into a much larger volume,” said Harrison. This allows heat to be radiated away before it reaches solid material surfaces, he said. The funding, from the European fusion research consortium EUROfusion and the EPSRC, will allow the researchers to improve their understanding of plasma exhaust physics, and to carry out better predictive modelling for the proposed prototype commercial fusion power plant, known as DEMO.

Frosi P.,ENEA | Bachmann C.,EUROfusion | Di Gironimo G.,University of Naples Federico II | Mazzone G.,ENEA | And 2 more authors.
Fusion Engineering and Design | Year: 2017

This paper refers to the activity of structural design of DEMO Divertor in the framework of the EUROfusion Consortium. The structural analysis and its preparatory assessments were carried on since a year and the first results were published in a previous paper. The Cassette Body has been examined considering the most conservatives loads (e.g. coolant pressure, volumetric nuclear heating and electro-magnetic loads) according to their latest estimates. This work is based on the design-by-analysis approach adopted in the conceptual design phase of the DEMO Divertor. This design activity has been focused on some key parameters e.g. loads, main geometric dimensions, positions of the Cassette attachments on the vacuum vessel, way of loads application to characterize the structural behavior of the Divertor Cassette. In addition to the existing 3D solid element model, a shell element model has also been developed: with this new model a parametric analysis can be done for a fast optimization. The structural assessment was done according to the Design and Construction Rules for Mechanical Components of Nuclear Installation (RCC-MRx). © 2017 Elsevier B.V.

Ciattaglia S.,EUROfusion | Federici G.,EUROfusion | Barucca L.,Ansaldo Energia | Lampasi A.,ENEA | And 2 more authors.
Conference Proceedings - 2017 17th IEEE International Conference on Environment and Electrical Engineering and 2017 1st IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2017 | Year: 2017

DEMO initial conceptual design studies are being conducted in Europe as part of the European Union Roadmap to Fusion Electricity, which aims to demonstrate the feasibility of electricity produced by nuclear fusion reactors around the middle of this century. The aim of this paper is to provide an overview of the DEMO project, highlighting its main characteristics and challenges in terms of design, integration, and operation. Particular emphasis is given on some important systems of the Balance of Plant (BoP), such as the primary heat transfer systems, the related power conversion systems, and the electrical power plant. The relevance of such systems is due to the need of a continuous reanalysis at any significant design change because of their huge dimensions, technical complexity, and strong impact on design integration, maintenance, and safety. © 2017 IEEE.

Konovalov V.G.,Institute of Plasma Physics of Ukraine | Voitsenya V.S.,Institute of Plasma Physics of Ukraine | Makhov M.N.,Institute of Plasma Physics of Ukraine | Ryzhkov I.V.,Institute of Plasma Physics of Ukraine | And 8 more authors.
Review of Scientific Instruments | Year: 2016

The plasma-facing (first) mirrors in ITER will be subject to sputtering and/or contamination with rates that will depend on the precise mirror locations. The resulting influence of both these factors can reduce the mirror reflectance (R) and worsen the transmitted image quality (IQ). This implies that monitoring the mirror quality in situ is an actual desire, and the present work is an attempt towards a solution. The method we propose is able to elucidate the reason for degradation of the mirror reflectance: sputtering by charge exchange atoms or deposition of contaminated layers. In case of deposition of contaminants, the mirror can be cleaned in situ, but a rough mirror (due to sputtering) cannot be used anymore and has to be replaced. To demonstrate the feasibility of the IQ method, it was applied to mirror specimens coated with carbon film in laboratory conditions and to mirrors coated with contaminants during exposure in fusion devices (TRIAM-1M and Tore Supra), as well as to mirrors of different materials exposed to sputtering by plasma ions in the DSM-2 plasma stand (in IPP NSC KIPT). © 2016 Author(s).

Bertinetti A.,Polytechnic University of Turin | Avramidis K.A.,Karlsruhe Institute of Technology | Albajar F.,Fusion for Energy F4E | Cau F.,Fusion for Energy F4E | And 4 more authors.
Fusion Engineering and Design | Year: 2016

The interaction cavity of the European 170GHz, 1MW Continuous Wave (CW) gyrotron for ITER, which could also be water-cooled using mini-channels as recently proposed, experiences during operation a very large heat load (>15MW/m2) localized on a very short (<1cm) axial length. Such heat loads are typical for high power gyrotrons.As the thermal deformation of the cavity influences the electromagnetic field structure and consequently the gyrotron operation, the analysis of the cavity performance requires the simultaneous solution of the coupled thermal-hydraulic, thermo-mechanic and electro-magnetic fields. In this paper, the thermal behaviour of the cavity under nominal heat load is computed first by CFD. Then a 3D thermo-mechanical model of the cavity is developed, based on the temperature maps computed by CFD, to evaluate the resulting deformation of the inner cavity surface. Finally the deformation is used to compute the updated heat load coming from the electromagnetic field generated by the electron beam in the deformed cavity, which becomes the input for a new iteration of the thermal-hydraulic, thermal-mechanical and electromagnetic analyses. It is shown that this iterative procedure converges to a self-consistent heat-load/temperature-field/deformation-field picture in nominal operating conditions, without exceeding a temperature of ∼230. °C on the inner surface of the cavity. © 2017 Elsevier B.V.

Marzullo D.,University of Naples Federico II | Bachmann C.,EUROfusion | Coccorese D.,University of Naples Federico II | Di Gironimo G.,University of Naples Federico II | And 2 more authors.
Fusion Engineering and Design | Year: 2017

This paper presents the pre-conceptual design activities conducted for the European DEMO divertor, focusing on cassette design and Plasma Facing Components (PFC) integration. Following the systems engineering principles, a systematic design method, the Iterative and Participative Axiomatic Design Process (IPADeP), has been adopted. Basing on Axiomatic Design, IPADeP supports the early conceptual design of complex systems. The work moved from the geometrical and interface constraints imposed by the 2015 DEMO configuration model. Then, since different materials will be used for cassette and PFCs, the divertor geometry has been developed taking into account the cooling parameters of the cassette Eurofer steel and the integration of PFCs cooling system. Accordingly, the design process led to a double wall cassette structure with internal reinforcing ribs to withstand cassette coolant pressure and three different kinds of piping schemes for PFCs with dual circuits. These three solutions differs in the feeding pipes layouts and target manifold protection and they have been proposed and evaluated considering heat flux issues, shielding problems, interface requirements with blanket and vacuum vessel and remote maintenance needs. A cassette parametric shell model has been used to perform first structural analyses of the cassette body against coolant pressure. Taking advantages of the parametric surface modelling and its linkage with Finite Element (FE) code, the cassette ribs layout and thickness has been evaluated and optimized, considering at the same time the structural strength needed to withstand the coolant parameters and the maximum stiffness required for cassette preloading and locking needs. © 2017 The Author(s).

Tanigawa H.,National Institutes for Quantum and Radiological Science and Technology | Gaganidze E.,Karlsruhe Institute of Technology | Hirose T.,National Institutes for Quantum and Radiological Science and Technology | Ando M.,National Institutes for Quantum and Radiological Science and Technology | And 3 more authors.
Nuclear Fusion | Year: 2017

Reduced-activation ferritic/martensitic (RAFM) steel is the benchmark structural material for in-vessel components of fusion reactor. The current status of RAFM developments and evaluations is reviewed based on two leading RAFM steels, F82H and EUROFER-97. The applicability of various joining technologies for fabrication of fusion first wall and blanket structures, such as weld or diffusion bonding, is overviewed as well. The technical challenges and potential risks of utilizing RAFM steels as the structural material of in-vessel components are discussed, and possible mitigation methodology is introduced. The discussion suggests that deuterium-tritium fusion neutron irradiation effects currently need to be treated as an ambiguity factor which could be incorporated within the safety factor. The safety factor will be defined by the engineering design criteria which are not yet developed with regard to irradiation effects and some high temperature process, and the operating time condition of the in-vessel component will be defined by the condition at which those ambiguities due to neutron irradiation become too large to be acceptable, or by the critical condition at which 14 MeV fusion neutron irradiation effects is expected to become different from fission neutron irradiation effects. © 2017 IAEA, Vienna.

Muraoka K.,Plazwire Co. | Wagner F.,Max Planck Institute for Plasma Physics (Greifswald) | Yamagata Y.,Kyushu University | Donne A.J.H.,EUROfusion
Journal of Instrumentation | Year: 2016

The accident at the Fukushima Dai-ichi nuclear power station in 2011 has caused profound effects on energy policies in Japan and worldwide. This is particularly because it occurred at the time of the growing awareness of global warming forcing measures towards decarbonised energy production, namely the use of fossil fuels has to be drastically reduced from the present level of more than 80% by 2050. A dilemma has now emerged because nuclear power, a CO2-free technology with proven large-scale energy production capability, lost confidence in many societies, especially in Japan and Germany. As a consequence, there is a world-wide effort now to expand renewable energies (REs), specifically photo-voltaic (PV) and wind power. However, the authors conjecture that PV and wind power can provide only up to a 40% share of the electricity production as long as sufficient storage is not available. Beyond this level, the technological (high grid power) and economic problems (large surplus production) grow. This is the result of the analysis of the growing use of REs in the electricity systems for Germany and Japan. The key element to overcome this situation is to develop suitable energy storage technologies. This is particularly necessary when electricity will become the main energy source because also transportation, process heat and heating, will be supplied by it. Facing the difficulty in replacing all fossil fuels in all countries with different technology standards, a rapid development of carbon capture and storage (CCS) might also be necessary. Therefore, for the short-range strategy up to 2050, all meaningful options have to be developed. For the long-range strategy beyond 2050, new energy sources (such as thermonuclear fusion, solar fuels and nuclear power - if inherently safe concepts will gain credibility of societies again), and large-scale energy storage systems based on novel concepts (such as large-capacity batteries and hydrogen) is required. It is acknowledged that the prediction of the future is difficult; therefore, the only insurance in this situation is by intensified research into all viable options. © 2016 IOP Publishing Ltd and Sissa Medialab srl.

Vallcorba R.,CEA Saclay Nuclear Research Center | Lacroix B.,French Atomic Energy Commission | Ciazynski D.,French Atomic Energy Commission | Torre A.,French Atomic Energy Commission | And 5 more authors.
Cryogenics | Year: 2016

The future DEMO Toroidal Field (TF) magnets are likely to feature cable-in-conduit conductors (CICC) cooled by forced flow of supercritical helium. Design activities were carried out at CEA to provide a winding pack compatible with DEMO plant requirements. The CEA proposal comprises, for each of the 16 D-shaped windings, 10 double-pancakes (2×392m long) wound in 10 turns. The conductor is a square-shaped Nb3Sn double channel conductor with a central spiral, carrying a nominal current of 95.5kA. We present a thermo-hydraulic analyses focused on the central, most critical pancake, where the maximum field is reached, aiming at evaluating the integrity of the proposed conductor design. Both normal and off-normal simulations were performed using detailed electromagnetic and neutron heating load maps as input, and evaluating operational quantities such as the temperature margin in burn conditions, and the hot spot temperature in quench conditions. We assessed the sensitivity of these quantities to some driving parameters, notably mass flow rate and the choice of friction factor correlation for the temperature margin, and quench initiation features for the hot spot temperature. Furthermore, the influence of the casing cooling on the temperature margin is analyzed. The study is carried out using two thermohydraulic models. © 2016 Elsevier Ltd.

Eurofusion | Date: 2010-09-21

Drinking water.

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