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UKAEA-CCFE-PR(25)3522023
High-shear methods have long been used in experiments to refine grain structures in metals, yet the underlying mechanisms remain elusive. We demonstrate a refinement process using molecular dynamic simulations, wherein nanocrystalline structures are generated from initially perfect lattices under high-shear strain. The simulation cells undergo a hi…
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UKAEA-CCFE-CP(25)102023
Fusion power is a critical part of the future energy landscape yet is all too often depicted with the focus on the fusion reaction itself with little attention on supporting systems. In practice of course a real power plant will have the tokamak surrounded by a plethora of ancillaries: the fuel cycle, cooling systems, diagnostics, radiation mana…
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UKAEA-CCFE-CP(25)062023
The EU-DEMO baseline design for the vacuum vessel (VV) currently provides for 48 openings – the so-called VV ports. These are foreseen to accommodate port plugs containing components, such as front ends for diagnostics and heating systems, first wall protection limiters and the first stages of the VV vacuum system. During the operation …
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UKAEA-CCFE-PR(24)2542023
Conventional crystal plasticity (CP) solvers are based on a Newton-Raphson (NR) approach which use an initial guess for the free variables (often stress) to be solved. These solvers are limited by a finite interval of convergence and often fail when the free variable falls outside this interval. Solution failure results in the reduction of the t…
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UKAEA-CCFE-PR(24)2252023
JET’s frequency-modulated continuous wave (FMCW) reflectometers have been operating well with the current design since 2005 and density profiles are being automatically calculated intershot since then. However, the calculated profiles had long suffered from several shortcomings – poor agreement with other diagnostics; sometimes inappropriate…
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UKAEA-CCFE-PR(24)2102023
This work addresses in-situ synergistic irradiation and thermomechanical loading of nuclear reactor components by linking new mechanistic understanding with crystal plasticity finite element modelling to describe the formation and thermal and mechanical annihilation of dislocation loops. A model of pressurised reactor cladding is constructed to …
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UKAEA-CCFE-PR(23)1872023
Solution reconstruction from limited number of measurements is useful in many areas of heat transfer applications. Unlike the standard problems, such reconstruction problems are ill-posed; thus, the non-uniqueness of solution and inherent instability severely complicates the modelling process. Consequently, more conventional inverse analysis method…
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UKAEA-RACE-CP(23)092023
When transferring a Deep Reinforcement Learning (DRL) model from simulation to the real world, the performance could be unsatisfactory since the simulation cannot imitate the real world well in many circumstances. This results in a long period of fine-tuning in the real world. This paper proposes a self-supervised vision-based DRL method that al…
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UKAEA-CCFE-PR(23)1592023
Fusion power output from spherical tokamaks would benefit from increased confined plasma density, but there exists a limit on the density before confinement is lost and the plasma current is disrupted. This density limit has long been characterized by a simple, global Greenwald limit proportional to the plasma current and inversely proportional …
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UKAEA-CCFE-PR(23)1582023
We propose a resistivity-beta driving mechanism aimed at explaining the appearance of free boundary long wavelength global instabilities in high-beta diverted tokamaks. These perturbations resemble very closely the RWM (resistive wall mode) phenomenon. Performing a proper toroidal analysis, we show that the magnetohydrodynamic stability is worsened…
Showing 11 - 20 of 107 UKAEA Paper Results