Journal of Fusion Energy最新文献

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.

The effects of B powder injection on plasma detachment about EAST discharge were studied by using SOLPS-ITER code package with the effects of E × B drifts considered. The simulation results show that plasma detachment occurs at the inner target in favourable toroidal magnetic field (B_t) direction at a relatively low B powder flow rate, one order of magnitude lower than that at the outer target. In a similar scenario with unfavourable B_t, it is found that the detachment thresholds of B flow rate for both the inner and outer targets are close and of the same order as that for the outer target with favourable B_t. In favourable B_t direction at B powder flow rate of 1.2 × 10²¹ atoms/s, a localized, broadened high-density region is formed near the inner target benefitted by the injection location and the E × B drift, and a radiation-intensified zone, mostly contributed by B¹⁺ and B²⁺, occurs there. The E × B drift facilitates plasma detachment at the inner target and simultaneously amplifies the in–out divertor asymmetry. In addition, the simulation results with three different injection locations show that the injection from outer strike point leads to the lowest Z_eff inside the separatrix and has an intermediate flow rate for detachment at the outer target, comparing with the X-point and upstream locations.