Journal of Fusion Energy最新文献

Stellarators as compact fusion power sources have incredible potential to help combat climate change. However, the task of making that a reality faces many challenges. This work uses Bayesian optimization, (BO) which is a method that is well suited to black-box optimizations, to address the complicated optimization problem inherent by stellarator design. In particular it focuses on the mechanical optimization necessary to withstand the Lorentz forces generated by the magnetic coils. This work leverages surrogate models that are constructed to integrate as much information as possible from the available data points, significantly reducing the number of required model evaluations. It showcases the efficacy of Bayesian optimization as a versatile tool for enhancing both magneto-static and mechanical properties within stellarator winding packs. Employing a suite of Bayesian optimization algorithms, we iteratively refine 2D and 3D models of solenoid and stellarator configurations, and demonstrate a 15% increase in optimization speed using multi-fidelity Bayesian optimization. For fusion technology to progresses from experimental stages to commercial viability, precise and efficient design methodologies will be essential. By emphasizing its modularity and transferability, our approach lays the foundation for streamlining optimization processes, facilitating the integration of fusion power into a sustainable energy infrastructure.

Capillary porous structure (CPS) based liquid metal divertors are currently being investigated as a possible alternative to the tungsten based solid plasma facing components (PFCs). The ability of CPS based technologies to withstand high heat fluxes (> 20 MW/m²) has been already demonstrated in linear devices as well as tokamaks. One of the key aspects of a liquid metal divertor is the erosion of the liquid metal with the subsequent contamination of the plasma. The liquid can be eroded by physical sputtering, evaporation and thermally enhanced sputtering. The absence of a theoretical model or detailed empirical data of Sn thermally enhanced sputtering prohibits reliable predictions of Sn erosion by fusion plasma. Especially in high density tokamak plasmas, thermally enhanced sputtering appears to be the dominant contributor to total erosion. To empirically evaluate the thermally enhanced sputtering yields an experimental campaign was conducted at the Nano-PSI device (T_e = 0.3–0.8 eV, (Gamma_{i} = 5 times 10^{18} {text{ m}}^{ - 2} ;{text{s}}^{ - 1})) with Sn surfaces exposed to homogeneous plasma of various ion species (Ar, Ne, H, He). The effect of ion impact energy on the sputtering yields was studied as well by biasing of the the liquid surface in range of − 10 to − 80 V. In case of Ar, Ne and He the Sn was exposed as a free-flowing surface and for H it was exposed in a stainless-steel capillary porous structure (CPS) to negate the observed H spitting of the free liquid surface. This work presents the measured thermally enhanced sputtering yields, with focus on the observed phenomena, such as plasma species and impact energy dependency.

A liquid Lithium (Li) Tungsten (W)-based divertor, which combines the advantages of both W and liquid Li, is a promising solution for the divertor of future fusion reactors. The 3D printing technology, which has advantages such as the ability to process complex structures based on 3D models and high energy density suitable for the manufacturing of high-melting-point metals, will play an important role in the manufacturing of divertor components. To address the corrosion behavior of target materials in liquid Li under operational conditions, we investigated the corrosion behavior of 3D-printing W and WZrC in static liquid Li at 550 °C for 500 h. After being exposed to liquid Li, the samples exhibited mass loss, grain boundary corrosion, and pitting corrosion. The mass loss rates of W and WZrC in liquid Li were 3.3 × 10^–2 and 1.76 × 10^–2 g/(m²·h), respectively. The XPS and XRD results of the samples did not show significant changes before and after the test. Corrosion of liquid Li has a greater effect on the thermal conductivity of W than that of WZrC. In this study, adding ZrC to W may be an effective way to improve the liquid Li corrosion resistance of W. Reducing surface cracks may improve the resistance of 3D-printing W alloys to liquid Li corrosion.

The purpose of this study is to design and analysis a neutronic experimental mock-up for supercritical carbon dioxide cooled Lithium-Lead (COOL) blanket of CFETR. The protype of mock-up is the equatorial outboard breeding unit (3# unit) of COOL blanket, which have the largest neutron wall loading. To verify the reliability of neutronic design of COOL blanket, the neutronic property of mock-up should be designed to be consistent with the protype. To facilitate detector layout and component installation, simplifications in radial arrangement of mock-up are necessary. The determined radial layout is arranged as Plasma Facing Component, First Wall, Gap 1, Flow Channel Insert 1 (FCI 1), Breeding Zone (BZ), Flow Channel Insert 2 (FCI 2), Gap 2 and Manifold (MF). And the dimensions of toroidal and poloidal were determined by the extent of neutrons leaking from the edge of mock-up. The determined size of the experimental mock-up is 500 mm (Toroidal)×500 mm (Poloidal)×326 mm (Radial). Ultimately, neutronic property and activation property of the mock-up is analyzed. The calculation results showed that the designed mock-up can be used to carry out neutronic experiment. This work will provide a guideline for design of next stage experiment.

Stellarators may have advantages for certain liquid metal options as Plasma Facing Components (PFC) for divertor targets and first walls due to the wide range of possible magnetic configurations, which additionally are free of disruptions and fast field variations. In a previous work (V. Queral et al., IEEE Trans. Plasma Sci. 52, 2024), a concept of stellarator reactor (ASTER-CP) based on swirling Li-molten salts and liquid lithium floating on the molten salt as PFC was presented. The divertor matters were not studied then and, thus, they are being studied and experimentally tested now.

The ASTER-CP reactor concept, the initial liquid metal experiments and potential concepts for the ASTER-CP divertor and first wall are reported. Concerning the experiments, several small scale experiments of galinstan in a small rotating cylinder under magnetic field have been produced, including one experiment with high viscosity galinstan-mixture for increased thickness of layer. An experiment of floating lithium on the molten salt LiCl-PbCl₂ gave fast volatilization/decomposition of the molten salt. Particularly for divertors, the traditional free-flow, Capillary Porous Systems and ‘divertorlets’ have been studied for application to ASTER-CP. Surface waves (hot spots), lack of enough surface fluid turbulence and excessive fluid speed are the main issues found in fast free-flow. The perhaps original concept of Distributed Divertor and Equi-power Surface is tentatively proposed and studied, taking advantage of stellarator fields and low recycling regime.

The procedure of ultrasonic testing for austenitic stainless steel welds relies heavily on the accurate assessment of actual welding faults. The research subject of this paper is a 40 mm 316L stainless steel butt weld, utilized in fusion reactors. Based on the weld acoustic performance test, sound field modeling, and reference block method, a double crystal probe S-Scan (sector scan) process is suggested. To detect the missed vertical-type groove flaws, a waveform conversion-based total focusing method (TFM) is developed. The study's findings demonstrate that the reliability of ultrasonic testing of austenitic stainless steel welds can be significantly increased by combining conventional sector scanning with cutting-edge TFM technology.

The Vacuum Vessel (VV), as the first confinement barrier of the Chinese Fusion Engineering Test Reactor (CFETR) must guarantee its integrity once the In Vacuum Vessel Loss of Coolant Accident (In-VV LOCA) happens. Enough experimental verifications are inevitable. And the data from the experimental facility should be convincing with an acceptable cost. In the present research, scaling criteria are identified for the In-VV LOCA, which can provide the direction for the design scheme of the experimental facility. The experimental facility employs the same working fluid and the equal thermal operation conditions. The volume scaling factor of 1/1000 for the VV with a toroidal structure adopted in the experimental facility is selected. The similarities of the flow at the break, flash and the flow resistance are prioritized. Through the computational simulation for the experimental facility, it has been demonstrated that the thermal hydraulic responses could be reappeared in the experimental facility within an acceptable range of distortions.

The lithium vapor divertor concept is being developed as a method to achieve detached divertor conditions in a tokamak while minimizing impurity radiation losses from the core plasma. SOLPS-ITER modeling has previously been used to identify some of the geometric constraints and required lithium evaporation rate of a lithium vapor divertor in a medium-sized tokamak during steady-state operation. Here an updated conceptual design based on these operating requirements is introduced and the thermal response of the system is modeled during cyclical operation, consistent with operation in a short-pulse tokamak. Controllability of the temperature of the lithium capillary porous system (CPS) is achieved by adopting a design where there is no line-of-sight for radiation from the plasma to reach the heated CPS surface. Operational strategies to minimize the amount of lithium evaporated between plasma discharges while achieving steady evaporation rates during plasma discharges are discussed and modeled here. The optimal feedforward control strategy demonstrated in this work is to ramp up the temperature of the evaporator as quickly as possible immediately before a plasma discharge and then reduce the heating to match the desired steady-state net evaporation rate just before the plasma discharge begins, allowing the thermal inertia of the system to stabilize the evaporation rate during the first second of the plasma discharge.