Y. D. Li

Characterization of core microturbulence in L-mode and H-mode regimes on the EAST superconducting tokamak

The core microturbulence (, ) provided by a tangential CO2 laser collective scattering system on the EAST tokamak, in low (L) and high (H) confinement mode regimes respectively, are presented. We report the change of core microturbulence characteristics from L-mode to H-mode: firstly, the spectrograms of the core microturbulence show the redistribution of microturbulence in the frequency domain after the L–H transition; secondly, the time evolution of the integrated spectral power displays that the amplitude of the core microturbulence in H-mode is much larger than that in L-mode; thirdly, the cross-correlation time-frequency spectrum analysis indicates that the structural characteristics of the core microturbulence in L-mode and H-mode are very different. These results suggest that both the amplitude and the structural characteristics of the core microturbulence change significantly from L-mode to H-mode, although the spatial extent of the transport barrier in H-mode is at the edge, which could be closely related to the changes of the profiles of basic plasma parameters.

The dynamics of short-scale turbulent fluctuations across low-intermediate-high-confinement transition with lower hybrid current drive in the EAST superconducting tokamak

Two different confinement transition discharges, the low-intermediate-high (L-I-H) and the low-intermediate-low (L-I-L) confinement transitions, respectively, have been obtained by lower hybrid current drive with lithium wall conditioning in the EAST superconducting tokamak. The dynamic features of short-scale turbulent fluctuations in the two discharges are investigated by a tangential CO2 laser collective scattering system. It is found that the great changes of broadband fluctuations in amplitude and structure characteristics are closely related to the choice of the final transition to H-mode. These results could shed light on the understanding of the L-H transition mechanism.

Development and Application of a Risk Monitor for Nuclear Power Plant

Risk monitor, which has been widely used in the progress of RID (Risk Informed Decision) in a NPP (Nuclear Power Plant), is a plant specific real-time analysis tool to determine the instantaneous risk based on actual plant configuration. Based on wide investigation of challenges and technical issues during the development of a risk monitor, a prototype named Risk Angel has been designed by FDS Team in collaboration with several institutes and universities. An overview of the architecture and main functions of Risk Angel were introduced in this paper, as well as the quantitative approach, the calculating engine and the model development. Risk Angel has been applied in a nuclear power plant in P.R. China.Copyright

The effects of plasma shape control on the edge collisionless ion orbit loss

Double null magnetic configurations with different elongation κ and triangularity δ are constructed by using an analytical solution of the Grad–Shafranov equation. The ion orbit losses in plasma edge region are calculated by solving the ion guiding center orbit equation for different values of κ and δ. It is found that the ion orbit loss is larger for a smaller value of κ or δ. The variation of the ion orbit loss fraction on the magnetic surface is also studied.

A Variable Ordering Heuristic Based on Zero-Suppressed Binary Decision Diagrams

Two approaches have been proposed to solve the large-scale fault trees or event trees for Probabilistic Safety Assessment in a nuclear power plant. The first one consists in MCS/ZBDD, which uses ZBDDs (Zero-suppressed Binary Decision Diagrams) to implement classical MCS (Minimal Cut Sets) algorithm. The second consists in designing heuristics and strategies to reduce the complexity of the BDDs (Binary Decision Diagrams) construction. This paper was motivated to combine the MCS/ZBDD and designing heuristics for ZBDDs together. A heuristic, which took the failure rate of basic event into account and utilized that truncation could be implemented on ZBDDs during the calculating process, was proposed. This heuristic accelerated the analysis progress by bringing forward the truncation and reducing the complexity of the intermediate ZBDDs. RiskA, a Zero-suppressed Binary Decision Diagram package extended to safety and reliability analysis, has adopted this heuristic. RiskA’s truncation strategies, which had some relations with the ordering scheme, were also introduced. The correctness and efficiency of this new heuristic were verified by some practical models’ analyses.Copyright

Experimental observation of (intermediate, high)-k micro-turbulence in different type H mode plasmas in EAST

Both k1 = 12 cm−1 (intermediate-k) and k2 = 22 cm−1 (high-k) micro-turbulence (k⊥ρs ∼ 1–4) in gradient region plasmas were measured simultaneously by the EAST poloidal CO2 laser collective scattering system. Their behaviors have been studied in detail in both ELM-free/type III ELMy and enhanced Da (EDA) H mode plasma discharges. Compared with that in the previous L mode phase, it can be seen obviously that the mean frequency of lower-k (k1) micro-turbulence increases and that of higher-k (k2) decreases during the ELM-free or type III ELMy H mode phase, while frequency-integrated spectral power (Stot) of both k1 and k2 micro-turbulence seems almost the same. On the other hand, both Stot and mean frequency of k1/k2 micro-turbulence show continuous increase during the EDA H mode phase. These results imply that the response of (intermediate, high)-k micro-turbulence on different type H mode is different. Further cross-correlation analysis between k1 and k2 micro-turbulence shows that their cross-correlation value is a little lower in H mode phase than the previous L mode phase. It can also be found that the cross-correlation value decreases gradually during the ELM-free and subsequent type-III ELMy phases, and it is almost zero in the EDA H mode phase. These new results could shed some light on the comprehensive understanding of mechanisms under H mode physics.Both k1 = 12 cm−1 (intermediate-k) and k2 = 22 cm−1 (high-k) micro-turbulence (k⊥ρs ∼ 1–4) in gradient region plasmas were measured simultaneously by the EAST poloidal CO2 laser collective scattering system. Their behaviors have been studied in detail in both ELM-free/type III ELMy and enhanced Da (EDA) H mode plasma discharges. Compared with that in the previous L mode phase, it can be seen obviously that the mean frequency of lower-k (k1) micro-turbulence increases and that of higher-k (k2) decreases during the ELM-free or type III ELMy H mode phase, while frequency-integrated spectral power (Stot) of both k1 and k2 micro-turbulence seems almost the same. On the other hand, both Stot and mean frequency of k1/k2 micro-turbulence show continuous increase during the EDA H mode phase. These results imply that the response of (intermediate, high)-k micro-turbulence on different type H m...

The response of short-scale density fluctuations to the activity of beta-induced Alfvén eigenmodes during strong tearing modes on EAST tokamak

Beta-induced Alfven eigenmodes (BAEs) during strong tearing modes (TMs) have been frequently observed in fast-electron plasmas of EAST tokamak. The dynamics of the short-scale ( density fluctuations during the activity of BAEs with strong TMs has been preliminarily investigated by a tangential CO2 laser collective scattering system. The results suggest the active, but different, response of short-scale density fluctuations to the TMs and BAEs. In the low-frequency (0–10 kHz) part of density fluctuations, there are harmonic oscillations totally corresponding to those of TMs. In the medium-high frequency (10–250 kHz) part of density fluctuations, with the appearance of the BAEs, the medium-high frequency density fluctuations begin to be dominated by several quasi-coherent (QC) modes, and the frequencies of the QC modes seem to be related to the changes of both TMs and BAEs. These results would shed some light on the understanding of the multi-scale interaction physics.

Notice of Retraction A nuclear power plant risk monitor based on cloud computing

Risk monitor is a plant specific real-time analysis tool used to determine the instantaneous risk based on the actual status of the systems and components. And the tool can also be used to optimize the maintenance plan. So how to keep real-time is one of the important problems to be solved. It may be lack of computing resources when there are many users or large-scale maintenance plans because the risk monitors server is a single computer and has high concurrency. Cloud computing can meet the requirement of risk monitor. In this paper the cloud platform is built, and the maintenance plan computing is taken as an example to verify the advantages of using cloud computing.