Cooling by turbulent gas jets is one of the efficient methods that is also proposed for cooling the divertor in fusion reactor. By high-fidelity numerical simulations using the Large Eddy Simulation (LES) method, we studied and explained the influence of jet flow dynamics on the local heat transfer. In this paper, the accuracy of simulated velocity, temperature field, and turbulent stress has been analyzed in detail. We evaluated the accuracy of the averaged values as a function of the sampling frequency of transient simulations, the numerical mesh, and the model constants of the sub-grid turbulence model. The largest relative error occurs at evaluating the average Nusselt number. Accurate but computationally very demanding simulations enable to understand the influence of jet flow dynamics on the heat transferred from cooled surfaces. The results of simulations equipped with computational accuracy are an important complement to experiments and a key source of information for the development and validation of engineering numerical models used in the search of efficient technological solutions in industry.
COBISS.SI-ID: 31988007
The dispersion-strengthening of fusion-relevant tungsten through the incorporation of tungsten sub-carbide W2C particles at the grain boundaries is demonstrated as an effective way of eliminating the detrimental W oxide, enhancing densification and stabilising the composite’s microstructure and flexural strength at room and high temperatures. The W2C particles are formed in situ during the sintering by carbon diffusion from WC nanoparticles added as a precursor to the W matrix. Even in an extremely fast sintering process using Field-Assisted Sintering Technology (FAST, 1900°C, 5 min), the added WC completely transforms to W2C, resulting in a W-W2C composite. While at least 5 vol. % of WC nanoparticles are needed to eliminate the oxide, approximately 10 vol. % result in a W-W2C composition with favourable characteristics.
COBISS.SI-ID: 32869927
The article presents the effect of deuterium (D) on the annealing of radiation damage. Tungsten (W) samples were sequentially irradiated with 20 MeV W ions at room temperature and loaded with a low-temperature D plasma at 370 K to decorate the created defects. To study the evolution of the created defects with D being present, samples were annealed by heating them to a desired temperature and held there for 2 h. The surviving displacement damage was decorated by re-exposing the samples to the same D plasma as before. A macroscopic rate equation model was used to recreate the experimental results. Three different defect types were identified being present in the material due to the W ion irradiation and that trap D. From the study we could determine the individual defect evolution with temperature. This study represents an example in our series of research studying the influence of displacement damage on hydrogen isotope retention, COBISS.SI-ID: 32394023, 57558787, 29341187, 57619203.
COBISS.SI-ID: 29342467
Understanding the physics of fast ions in a fusion plasma is widely considered as one of the crucial tasks for the reliable operation of fusion tokamak reactors. Measurements on tokamaks have shown that gamma rays are produced when fast ions react with either plasma fuel ions or with the plasma impurities such as beryllium, carbon and oxygen. The spectroscopy of these gamma rays can be used for measurements of fusion rates in a plasma or behavior and confinement of fusion reaction products, such as the alpha particles. To computationally support experiments a methodology has been developed for creation of a realistic plasma gamma ray source for Monte Carlo simulations. The methodology consists of several steps, the generation of realistic plasma parameters, generation of sampling distribution functions on the basis of calculated plasma parameters and the creation of realistic plasma gamma ray source for the Monte Carlo calculation. For example, the source position distribution function is based on calculated reaction rate densities for the gamma ray emitting reactions. All necessary distribution functions and plasma parameters are combined into an input file for the developed MCNP source subroutine. In the source subroutine the direction of gamma ray emission and the energy of the gamma rays are determined on the basis of parameters of the nuclear reaction and the direction of gamma ray emission. The developed methodology was analyzed on a MCNP tokamak model to demonstrate that the methodology generates a realistic plasma gamma ray source for Monte Carlo simulations.
COBISS.SI-ID: 43921411
This article presents an integrated environment for simulations of particle tracing in Scape-off layer (SOL) and heat loads in tokamak. A comprehensive simulation computer environment developed for the analysis and constriation of blankets inside the ITER fusion reactor, as well as other tokamak. The environment contains CAD core, meshing, simulation of fast particles (ions) that heat water-cooled panels hiting surface at a sharp angles, FEM thermal analysis of panels, and visualization and connections to other simulation codes.
COBISS.SI-ID: 16530203