Results 1 - 10 of 249
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[en] The SPACE code offers several options for critical flow model. One of the option is Henry/Fauske-Moody model. When using this model, Henry-Fauske critical flow model is used for single phase liquid and Moody model is used for 2-phase flow. For Henry-Fauske model, SPACE code assumes non-equilibrium (NE) factor of 0.14. In previous OPRlO00 SBLOCA analysis methodology based on RELAPS code, non-equilibrium factor of 1.0 was used to get more conservative break flow. To develop SBLOCA analysis methodology for OPRlO00 using SPACE code, it was necessary to use different non-equilibrium factor from SPACE default values for Henry-Fauske model. The SPACE code was improved by adding additional option for Henry/Moody-Moody model, which uses user input non-equilibrium factor. To accept user input equilibrium factor, the SPACE code is improved by expanding lookup table used in Henry/Fauske-Moody model. To verify the new model, we perform verification calculations on LOFT L9-3 which is a represenrative integral effect test (IET).
[en] The quasilinear mixing-length approach to efficient prediction of transport in fusion devices is improved to account for the ‘Dimits’ upshift between linear and nonlinear critical pressure gradients in zonal-flow-saturated turbulence regimes. This modification uses the frequency mismatch between modes interacting turbulently to track changes in saturation efficiency. Near criticality, energy is transferred exclusively to stable eigenmodes, rapidly increasing the efficacy of the nonlinearity. The modified quasilinear model is able to predict below-threshold turbulent ion-temperature-gradient-driven transport accurately and also yields significantly improved predictions for trapped-electron-mode transport. (letter)
[en] We report the synthesis and physical properties of the single crystals of TaC, which are proposed to hold topological band structure as a topological superconductor (TSC) candidate. Magnetization, resistivity and specific heat measurements are performed and indicate that TaC is bulk superconductor with critical temperature of 10.3 K. TaC is a strongly coupled type-II superconductor and the superconducting state can be well described by s-wave Bardeen–Cooper–Schrieffer theory with a single gap. The upper critical field (H c2) of TaC shows linear temperature dependence, which is quite different from most conventional superconductors and isostructural NbC, which is proposed to manifest topological nodal-loops or type-II Dirac points as well as superconductivity. Our results suggest that TaC would be a new candidate for further research of TSCs. (paper)
[en] The (1 + 1)-dimensional classical φ 4 theory contains stable, topological excitations in the form of solitary waves or kinks, as well as a non-topological one, such as the oscillon. Both are used in effective descriptions of excitations throughout myriad fields of physics. The oscillon is well-known to be a coherent, particle-like structure when introduced as an ansatz in the φ 4 theory. Here, we show that oscillons also arise naturally in the dynamics of the theory, in particular as the result of kink–antikink collisions in the presence of an impurity. We show that in addition to the scattering of kinks and the formation of a breather, both bound oscillon pairs and propagating oscillons may emerge from the collision. We discuss their resonances and critical velocity as a function of impurity strength and highlight the role played by the impurity in the scattering process. (paper)
[en] In recent decades, hydrogen-rich compounds are promising candidates for room-temperature superconductors under extremely high pressure. Remarkably, the theory-oriented finding of covalent hydride HS and a class of clathrate hydrides, such as YH and LaH, with high superconducting critical temperature (T) above 240 K, which give rise to the hope of searching for room-temperature superconductivity among hydrogen-rich compounds under high pressure. In this paper, we focus on the research progress of binary and ternary hydrides, provide the introduction of conventional phonon-mediated superconductivity theory and the physical mechanism of high-temperature superconductivity briefly, and offer an outlook on the challenge of discovering room-temperature superconductors among hydrogen-rich compounds in the future.
[en] The Comprehensive Research Facility for Fusion Technology (CRAFT) project has been launched in 2019, for developing the essential engineering technologies for Chinese Fusion Engineering Testing Reactor (CFETR). Within this project, a full-size toroidal field (TF) coil will be built as the prototype coil for CFETR. Based on design of CFETR magnet system, the TF coil will operate at 95.6 kA in a peak field of 14.5 T. The high-J c Nb3Sn strand is taken into consideration due to the critical current density of ITER-grade Nb3Sn is too low at 14.5 T. Considering that it will be the first time to apply the high-J c Nb3Sn strand in the large-scale cable-in-conduit conductor (CICC) for fusion magnet, a conductor sample made of high-J c Nb3Sn strand with short twist pitch (STP) cable pattern was manufactured in ASIPP and tested in SULTAN facility, to investigate the feasibility. The test campaign focuses on the impact of cyclic electromagnetic (EM) loading and warm-up cool-down (WUCD) to the performance of the conductor, the strain distribution of the conductor before and after EM cycles was measured by inductive method to make a deeper insight of the conductor performance evolution. AC losses tests have also been carried out, providing relevant information for further coil design. (paper)
[en] Ternary noncentrosymmetric superconductors TaXSi (X = Re, Ru) investigated by magnetization, resistivity, and specific heat measurements. It crystallize in the orthorhombic TiFeSi-type structure with superconducting transition = 5.32 K and 3.91 K for TaReSi and TaRuSi, respectively. A low value of specific heat jump and the upper critical field concave nature suggests a nontrivial superconducting gap. (paper)
[en] Over the last 20 years, technologies for manufacturing rare-earth barium copper oxide (REBCO)-coated conductors have undergone a steady development. Currently, the properties of these conductors are reasonably stable owing to the intensive efforts of the manufacturers. However, for high-field magnet applications, such as the magnets used in nuclear magnetic resonance instruments, accelerators, and fusion reactors, further enhancements in the current-carrying capabilities and/or the current densities of the conductors under a high magnetic field are necessary. Recently, several conductors doped with artificial pinning centers (APCs) have become commercially available, primarily from four manufacturers: Fujikura, Shanghai ST, SuperOx, and SuperPower. In this study, we characterized these relatively new conductors from the viewpoint of a magnet designer. We measured the critical currents (I c) of full-size 4 mm wide conductors in a wide field range at 4.2 K and 77 K; we also measured the critical temperatures. The measurement results showed that the I c values at 4.2 K under perpendicular fields for these conductors are significantly greater than those of non-APC conductors; for the 4 mm wide conductors, the I c values are in the range of 300–740 A and 450–1000 A at 18 T and 12 T, respectively. Furthermore, we clarified that the non-Cu current density (J c) at 4.2 K for some of the investigated conductors is more than twice the J c of the recent Nb3Sn conductors in fields exceeding 15 T. In the investigated commercial REBCO-APC conductors, the highest layer J c of ∼60 kA mm−2 (at 18 T and 4.2 K) was noted. We also investigated the I c–B relationship at 4.2 K for the recent REBCO-APC conductors. (paper)
[en] The shape of the temperature nano-probes is a significant factor to evaluate the temperature measurement accuracy in the nanoscale temperature detection. Based on the finite element numerical simulation method, the temperature nano-probe model is established for nano-devices with variable powers. The temperature nano-probes with different shapes of sphere, rod, tube and disk are designed and studied. It is found that the heat transfer process between the nano-device and the temperature nano-probes is affected by the shape of nano-probes. Additionally it is dependent on the size of the device and the gap distance between the nano-device and nano-probes. The high stability and accuracy in the temperature measurement process is obtained in case of the nano-probe with the shape of nano-disk. The temperature error can be minimized through controlling the side length of the disk. (author)
[en] As part of an effective regulatory regime, regulators must ensure their inspectors are suitably qualified and experienced to undertake their regulatory roles. IAEA provides a number of guides on this topic, which include; Managing Regulatory Body Competence (No.79, 2013), Methodology for the Systematic Assessment of the Regulatory Competence Needs (IAEA-TECDOC-1757, 2015) and Building Competence in Radiation Protection and the Safe Use of Radiation Sources (RS-G-1.4, 2001). A significant proportion of this focus is on the regulatory skills; however, regulators also need individuals with specific technical competencies. Over time regulators also need to assess how their skills profile is developing and manage specific deficits introduced by changing work or movement of staff by aiding the targeting of either retraining, providing experience, recruiting or employing the use of a technical support contractor to close these deficits. This poster discusses the development of technical skills and behavioural competency framework and its deployment in supporting UK team of Radiological Protection & Criticality Safety inspectors in the assessment of the regulator’s skills profile.