A low wall-loading DEMO reactor design with high priority for early and reliable realization of a tokamak fusion reactor over the cost performance

Based on scientific databases adopted for designing ITER plasmas and on the advancement of fusion nuclear technology from the recent R&D program, a low wall-loading DEMO fusion reactor has been designed, where high priority has been given to the early and reliable realization of a tokamak fusion plasma over the cost performance. Since the major radius of this DEMO reactor is chosen to be 10 m, plasma ignition is achievable with a low fusion power of 0.8 GW and an operation period of 4–5 hours is available only with inductive current drive. The low ignition power makes it possible to adopt a first wall with an austenitic stainless steel, for which significant databases and operating experience exists, due to its use in the presence of neutron irradiation in fission reactors. In step with development of advanced materials, a step-wise increase of the fusion power seems to be feasible and realistic, because this DEMO reactor has the potential to produce a fusion power of 5 GW.     

Non-destructive examination of the bonding interface in DEMO divertor fingers

Plasma facing components (PFCs) with tungsten (W) armor materials for DEMO divertor require a high heat flux removal capability (at least 10 MW/m² in steady-state conditions). The reference divertor PFC concept is a finger with a tungsten tile as a protection and sacrificial layer brazed to a thimble made of tungsten alloy W – 1% La₂O₃ (WL10). Defects may be located at the W thimble to W tile interface. As the number of fingers is considerable (>250,000), it is then a major issue to develop a reliable control procedure in order to control with a non-destructive examination the fabrication processes. The feasibility for detecting defect with infrared thermography SATIR test bed is presented. SATIR is based on the heat transient method and is used as an inspection tool in order to assess component heat transfer capability. SATIR tests were performed on fingers integrating or not the complex He cooling system (steel cartridge with jet holes). Millimeter size artificial defects were manufactured and their detectability was evaluated. Results of this study demonstrate that the SATIR method can be considered as a relevant non-destructive technique examination for the defect detection of DEMO divertor fingers.     

Thermo-hydraulic analyses associated with a CEA design proposal for a DEMO TF conductor

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 × 392 m long) wound in 10 turns. The conductor is a square-shaped Nb₃Sn double channel conductor with a central spiral, carrying a nominal current of 95.5 kA. 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.     

Neutronic analyses of the HCPB DEMO reactor using a consistent integral approach

This work is devoted to nuclear design analyses of the new HCPB-type DEMO reactor developed in the frame of the EFDA PPPT program. The neutronic simulations were carried out with the MCNP5 code using a full scale 3D torus sector model of the DEMO reactor. The model was generated with the McCad conversion tool from available CAD models using a consistent integral approach. The neutronic analyses addressed the tritium breeding performance, the nuclear power generation and the shielding capabilities of the reactor. Although tritium self-sufficiency was shown, the tritium breeding performance of the current design calls for further design improvements to arrive at a higher uncertainty margin. The shielding performance of the reactor is close to the limit. Sufficient shielding can be easily provided by a slight increase of the inboard shield thickness.     

Conceptual design study of fusion DEMO plant at SWIP

The basic definition and development strategy of the DEMO plant based on the Chinese fusion power plant (FPP) program are presented briefly. A conceptual design study of fusion HCSB-DEMO reactor with a fusion power of 2550 MW and a neutron wall loading of 2.3 MW/m² is performed recently. Three sets parameters of core plasma for different DEMO design objectives are proposed. A helium-cooled blanket system with ceramic breeder (Li₄SiO₄), the structure material of low-activation ferritic steel (LAF/M) and Be neutron multiplier based on Chinese ITER HCSB-TBM design foundation are considered. The design parameters, preliminary analyses and the basic structure as well as development strategy of HCSB-DEMO reactor are introduced.     

Language/Action Meets Organisational Semiotics: Situating Conversations with Norms

Virtual professional communities require a strong co-evolution of their social and information systems. To ensure that the evolutionary process of their socio-technical systems is viable, a legitimate user-driven specification process is required. Such a process helps to ensure the meaningfulness and acceptability of specification changes. A specification method supporting this process should be grounded in the neo-humanist paradigm so that subjectivist and conflict aspects receive proper attention. Two related subfields of information science that have roots in this paradigm are the Language/Action Perspective (LAP) and organisational semiotics (OS). The RENISYS method for specification of the socio-technical systems of virtual professional communities is presented. It combines aspects from both LAP and OS, by building on work done in the DEMO (LAP) and MEASUR (OS) methodologies. It thus provides an operationalization of neo-humanist ideals that can help to extend theoretical and empirical research.     

水库多目标优化调度技术比较研究

多目标智能优化算法种类繁多,不断涌现,在水库优化调度中得到了广泛应用,但多目标智能优化技术仍然是目前水库群综合利用优化调度研究中的热点和难点之一。已有的研究算法大多是关于水库优化调度中适用性的应用研究,且实际问题简化多,在算法算子的选择、算法性能的探讨和比较、特别是多目标优化等方面还不够深入。为此,选择应用较为广泛的NSGA-Ⅱ和DEMO算法,从变量规模、约束处理技术等方面,对其在水库多目标优化调度中的应用效果进行初步分析、比较和评估,为水库多目标优化调度算法的选择提供了参考。     

High heat flux components—Readiness to proceed from near term fusion systems to power plants

A present topic of high interest in magnetic fusion is the “gap” between near-term and long-term concepts for high heat flux components (HHFC), and in particular for divertors. This paper focuses on this issue with the aim of characterizing the international status of current HHFC design concepts for ITER and describing the different technologies needed in the designs being developed for fusion power plants. Critical material and physics aspects are highlighted while evaluating the current readiness level of long-term concepts, identifying the design and R&D gaps, and discussing ways to bridge them.     

国产高性能通用数字信号处理器的DEMO板设计

为了向用户演示高性能芯片BWDSP100,设计了一款DEMO板。通过该板可以向用户演示芯片的功能、性能等。板卡采用经典FPGA+DSP结构,处理功能强大,控制灵活。在设计过程中,贯彻以用户为中心的设计思想,不仅做到让用户使用方便,还要全面演示芯片。     

Japanese contribution to the DEMO-R&D program under the Broader Approach activities

Several technical R&D activities mainly related to the blanket materials are newly launched as a part of the Broader Approach (BA) activities, which was initiated by the EU and Japan. According to the common interests for these parties in DEMO, R&Ds on reduced activation ferritic/martensitic (RAFM) steels as structural material, SiC_f/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology are carried out through the BA DEMO R&D program, in order to establish the technical bases on the blanket materials and the tritium technology required for DEMO design. This paper describes overall schedule of those R&D activities and recent progress in Japan carried out by JAEA as the domestic implementing agency on BA, collaborating with Japanese universities and other research institutes.