Within the European Power Plant Conceptual Study (PPCS) four fusion power plant “models” have been developed. Two of these models were developed considering limited extrapolations both in physics and ...in technology. For the two other models, advanced physics scenarios have been identified and combined with advanced blanket concepts that allow higher thermodynamic efficiencies of the power conversion systems. For all the PPCS models, systems analyses were used to integrate the plasma physics and technology constraints to produce self-consistent plant parameter sets. The broad features of the conclusions of previous studies on safety, environmental impact and economics have been confirmed for the new models and demonstrated with increased confidence. The PPCS also helps in the definition of the objectives and in the identification of the design drivers of DEMO, i.e. the device between the next step (ITER) and a first-of-a-kind reactor. These will constitute the basis of the European DEMO Conceptual Study that has recently started.
Developing a divertor concept for fusion power plants to be built after ITER is deemed to be an urgent task to meet the EU Fast Track scenario. This task is particularly challenging because of the ...wide range of requirements to be met, namely, the high incident peak heat flux, the blanket design with which the divertor has to be integrated, sputtering erosion of the plasma-facing material caused by the incident particles from the plasma, radiation effects on the properties of structural materials, and efficient recovery and conversion of the considerable fraction (∼15%) of the total fusion thermal power incident on the divertor.
This paper provides an overview of the development of different conceptual divertor designs (water-cooled, liquid metal-cooled, and helium-cooled types); their advantages and disadvantages and expected performance are outlined and discussed. Emphasis is placed on summarizing the status and progress of R&D associated with He-cooled divertor designs which have been proposed in most of conceptual plant models in Europe and USA.
The dual-coolant (DC) blanket—characterised by its simple construction, simple function, and high thermal efficiency—is one of the EU advanced blanket concepts to be investigated in the frame of the ...long-term power plant conceptual study (PPCS). Its basic concept is based on the use of helium-cooled ferritic steel structure, the self-cooled Pb–17Li breeding zone, and SiC/SiC flow channel inserts, serving as electrical and thermal insulators. The present work on PPCS is drawn extensively on the preparatory study on plant availability carried out in 1999 with an objective to perform the conceptual design of the DC blanket concept where some details are to be selected in accordance with the overall strategy, which allows an extrapolation of the present knowledge between the near-term solutions (helium-cooled pebble bed (HCPB), water-cooled lead–lithium (WCLL) blanket concepts), and the very advanced self-cooled Pb–17Li SiC/SiC (SCLL) blanket concept. In the PPCS the reactor power is adapted to a typical size of commercial reactors of 1500 MWe which requires iterative calculations between the blanket layout and the system code analysis. The results of the first iteration are reported. This work is under the coordination of FZK in co-operation with CEA, EFET, IBERTEF, UKAEA, VTT Processes and VR.
Nuclear fusion is considered as a future source of sustainable energy supply. Since the H-mode discovery in ASDEX experiment ""Divertor I"" in 1982, the divertor has been an integral part of all ...modern tokamaks and stellarators. The major goal of this thesis is to develop a feasible divertor design for a fusion power plant to be built after ITER. The thesis describes the approach in the conceptual development of a helium-cooled divertor and the methods of verification and validation of the design.
The dual-coolant lead-lithium (DCLL) blanket concept, which is considered as a candidate for fusion power plants and possibly for a demonstration reactor (DEMO), is being investigated within the ...framework of the European Power Plant Physics and Technology (PPPT) study. One of major issues of the DCLL concept development is the design of the flow channel inserts (FCIs), which are essential for the reduction of magneto-hydrodynamic (MHD) pressure losses. Due to the tight schedule for the short-term PPPT DEMO, a low-temperature DCLL concept with a liquid metal outlet temperature below 500 °C has been proposed. This allows the use of a simpler type of FCI (taking into account the LM corrosion issues), e.g. Eurofer-Alumina-Eurofer sandwich FCI, instead of the SiCf/SiC version for high temperature case, the production thereof is challenging. This paper discusses the technological study on manufacturing of some FCI design variants and post-examination of the samples.
The use of impinging jets for divertor cooling in the conceptual fusion power plant is attracting much attention due to its very high heat removal capability and moderate pumping power requirement. ...The latest and the most advanced divertor concept is based on modular design cooled by helium impinging jets. To reduce the thermal stresses, the plasma-facing side of the divertor is build up of numerous small cooling fingers cooled by an array of helium jets. In this study the influence of nozzle sizes on the heat transfer and flow characteristics of such cooling finger is investigated numerically. The main objective is to find an optimal size and distribution of nozzle diameters in the jet array in which the heat transfer would be the highest possible at an acceptable pressure drop through the cooling finger. Prior to nozzle diameters modification, the simulation results for the reference finger geometry were validated against high heat flux experiments. A good agreement was obtained. The nozzle diameters were then modified at two different mass flow rates (13.5
g/s and 6.8
g/s per cooling finger). The most critical design parameter of interest was the maximum thimble temperature, which is limited by the melting temperature of the filler material in the brazed finger joint. It has been found that an optimal jet arrangement should have equal nozzle diameters to reach the highest thimble temperature decrease, while keeping the pressure drop within reasonable limits.
The design of fusion plasma-facing components is challenging, as their materials have to meet rigorous requirements in terms of low activation and high-temperature strength. At the same time, ...sufficient ductility is required even in the low-temperature range. Unfortunately, these properties are not found in conventional materials. To solve this problem, a hybrid material that combines the high strength of one material with the high ductility of the other material was developed. This paper presents the hybrid material, which consists of thin tungsten and vanadium layers. This hybrid material was produced by means of diffusion bonding at relatively low temperature in a vacuum chamber. Microstructural investigations and nanoindentation tests indicated no cracks, no delamination, and no brittle intermetallic phases along the bond interfaces. Investigations of the mechanical properties of the hybrid material by instrumented Charpy impact tests revealed a relatively low ductile-to-brittle transition temperature (DBTT) at 124°C (compared to the DBTT of polycrystalline tungsten of >441°C) with an absorbed Charpy impact energy of 4.53 J kleinst (KLST)-specimen. Additionally, the tested Charpy impact specimens were found to be not fractured thoroughly even at room temperature.
At Karlsruhe Institute of Technology (KIT), a He-cooled divertor design for future fusion power plants has been developed. This concept is based on the use of modular cooling fingers made from ...tungsten and tungsten alloy, which are presently considered the most promising divertor materials to withstand the specific heat load of 10
MW/m
2. Since a large number of the finger modules (
n
>
250,000) are needed for the whole reactor, developing a mass-oriented manufacturing method is indispensable. In this regard, an innovative manufacturing technology, Powder Injection Molding (PIM), has been adapted to W processing at KIT since a couple of years. This production method is deemed promising in view of large-scale production of tungsten parts with high near-net-shape precision, hence, offering an advantage of cost-saving process compared to conventional machining.
The complete technological PIM process for tungsten materials and its application on manufacturing of real divertor components, including the design of a new PIM tool is outlined and, results of the examination of the finished product after heat-treatment are discussed. A binary tungsten powder feedstock with a solid load of 50
vol.% was developed and successfully tested in molding experiments. After design, simulation and manufacturing of a new PIM tool, real divertor parts are produced. After heat-treatment (pre-sintering and HIP) the successful finished samples showed a sintered density of approximately 99%, a hardness of 457 HV0.1, a grain size of approximately 5
μm and a microstructure without cracks and porosity.
At present, a He-cooled divertor design for future fusion power plants is being developed at Forschungszentrum Karlsruhe. The divertor has to withstand high heat loads as well as sputtering, so that ...tungsten is considered to be the most promising material. Due to its high hardness, processing by standard shaping technologies, such as milling, is either difficult or even impossible. Consequently, powder injection moulding (PIM) as a method for cost-effective net shape fabrication has been adapted to tungsten.
The key steps in injection moulding, such as feedstock formulation, the injection moulding process itself as well as debinding and sintering were studied. A tungsten feedstock with an optimised solid load of 55
vol.% was developed and successfully tested in moulding experiments applying complex shaped cavities. Thermal consolidation of injection-moulded components leads to a sintered density of approximately 96% and a grain size of approximately 18
μm. For final densification and grain size reduction, hot isostatic pressing (HIP) was investigated.
•CFD analysis of alternative cooling fingers was performed.•Cooling efficiency is evaluated by comparing the maximum tile temperatures.•Besides hexagonal shape, the square one shows the best ...performance.
In support of shadowing of the divertor target plate edges in toroidal direction against damage caused by the incident particles, the fingers at the boundary of the target plate should ideally form a flat surface. The reference cooling fingers are of hexagonal shape and when assembled together, their edge boundary cannot be flat. Therefore, the boundary segments need to be designed in a different way. Three possible designs are investigated: non-symmetric pentagonal fingers and two square-shaped fingers of different sizes, all cooled by the same type of concentric cartridge as in the reference design. Their heat transfer performance is analyzed from the point of view of maximum allowable temperature of the thimble structure. The computational fluid dynamics (CFD) analysis is performed to obtain the minimum mass flow rate of the coolant which is necessary to keep the structure's temperature below the permissible limit at an acceptable pressure loss.
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