This paper presents a radiation embrittlement model applicable to polycrystalline BCC tungsten, in the context of fusion reactor technology. BCC tungsten fracture response is temperature and dose-dependent, due to critical sub-grain plasticity mechanisms and their interaction with brittle fracture initiators. Mesoscale plasticity effects are treated using a comprehensive, close-form analytical expression, accounting for thermally activated slip and cross-slip influences. In practice, the number of slip bands generated in all the grains of a macroscopic grain aggregate is calculated first, for a given plastic strain increment. The results associated with different temperature and dose conditions are then side-by-side compared with corresponding experimental fracture toughness data up to 1100 degrees C. To demonstrate the predictive model capability, we successfully apply our methodology to the case of tungsten irradiated by neutrons up to 1 dpa. The proposed approach to predict the embrittlement does not use any data adjustment, is based on the SEM-EBDS microstructure of the investigated material, possesses distinctive predictive capacities and is directly applicable in support of advanced design rules to ensure safety during nuclear operation of fusion reactors.
The reconstruction of three-dimensional (3D) multiphase microstructures is essential for understanding the physical properties of porous materials. In this study, we evaluate the performance of Denoising Diffusion Probabilistic Models (DDPMs) and Generative Adversarial Networks (GANs), specifically WGAN-GP and iWGAN, in generating 3D representations of multiphase materials with varying degrees of heterogeneity: homogeneous illite clay, heterogeneous Boom Clay, and highly complex concrete. Our findings demonstrate that DDPMs outperform GANs in capturing the intricate spatial statistics and multiphase structures of these materials. While GAN-generated samples exhibit mode collapse and structures that do not resemble the ground truth, DDPMs produce microstructures that better preserve phase distributions and morphological characteristics. These results highlight the potential of diffusion models for realistic 3D microstructure synthesis, paving the way for improved simulations in subsurface and construction material applications.
Four well known 8–-9 Δσ_γ(Φ_dpa) trend curve, while the T91-trend curve is clearly higher, in particular in the early stage of irradiation, below 0.2 dpa. The plastic instability stress, σPIS, increases monotonically with neutron exposure. Contrary to what is reported in the literature for low-temperature irradiation, the true stress–true strain curves do not superimpose when shifted with respect to the unirradiated flow curve, indicating that the post-yield mechanisms are different. Further detailed microstructural investigations are required to better understand the behavior of these steels under irradiation.
This study examines the microstructural and hardening response of two ITER-grade pure tungsten materials, which were exposed to neutron irradiation at 600 degrees C and 1000 degrees C up to a dose of similar to 1 dpa. Two major types of defects, dislocation loops and nanovoids, are observed for both grades and analyzed with transmission electron microscopy. While the general morphology and subgrain structure remained stable under irradiation, the number density of defects decreased, and average defect size increased at the higher irradiation temperature. Nanovoids exhibited greater thermal stability than dislocation loops, which led to their predominance in the radiationinduced hardening, particularly at 1000 degrees C. Hardening contributions were assessed using the dispersed barrier model, which showed that voids contributed more significantly to hardening than loops at any irradiation temperature. Various superposition rules are applied for the total hardening effect and the best fit is provided by squared summation with the size-dependent coefficient of barrier strength. The findings highlight the importance of void control and defect sink engineering in optimizing tungsten for fusion applications. This research aims to provide insights for designing radiation-resistant tungsten microstructure for advanced fusion reactor applications by linking defect behavior with mechanical properties under neutron irradiation.
Following the motivation for an Accelerator Driven System (ADS), the requirements on the accelerator are derived. Using the MYRRHA project as example, the beam optics/dynamics design and operational concept of such an accelerator are discussed and the main technology choices and challenges are presented.
