Abstract ：

Heat pipe cooled reactor (HPR) has broad application prospects in deep space exploration, deep-sea submarine exploration, and other scenarios due to the small size, high inherent safety, and easy modularization and expansion. However, the HPR conducts thermal energy through evaporation and condensation of the working fluid inside the heat pipe. This feature makes the HPR a large time-delay system. If the power control system adopts the conventional PID algorithm, there will be a long settling time. Therefore, the model predictive control algorithm is proposed for the power control system to improve the control performance. The HPR linear model, which is developed by linearization of its nonlinear model, is chosen as the predictive model. The optimal control value is obtained by solving the optimization problem based on the predictive model and the electric power feedback value. The discrepancy between the predive model and the actual system response results in the presence of steady-state error. To solve this problem, an integral controller is added to eliminate the error. The appropriate control system parameters are tuned by the trial and error method. The proposed control system has satisfactory control performance, which can significantly shorten the settling time. The model predictive control can effectively overcome the influence of the large time-delay characteristic.

Keyword ：

heat pipe cooled reactor linearization model predictive control online optimization power control

Cite：

Copy from the list or Export to your reference management。

Abstract ：

In order to explore the core corrosion characteristics of horizontal lead-bismuth reactor in oxygen-controlled environment, a liquid lead-bismuth eutectic (LBE) corrosion model including the growth and removal process of oxide layer was established in this paper. The coupling method of double-layered oxidation model and computational fluid dynamics (CFD) was used to simulate the long-term oxidation corrosion of horizontal LBE reactor core numerically. The results show that the average total oxide layer thickness of fuel rod surface is 1.59 μm, and the thickest oxide layer is 3.48 μm on the fuel rod surface at the core outlet after 20,000 h. The fuel rods maintain a double-layer oxide layer structure. The growth rate and removal rate of the oxide layer on fuel rod surface increase with the increase of inlet temperature and the decrease of inlet flow rate. The growth rate of the oxide layer on fuel rod surface increases with the increase of inlet oxygen concentration, while the removal rate decreases. At higher temperature above 420, lower flow velocity below 0.25 m/s and lower oxygen concentration below 2 × 10−8wt%, the magnetite layer will first be completely removed from the surface of the fuel rods at the core outlet. The liquid LBE oxidation corrosion model and coupled CFD method presented in this paper can be used for numerical simulation of oxidation corrosion in different units of LBE cooling system. © 2022

Keyword ：

Bismuth compounds Computational fluid dynamics Corrosion rate Flow velocity Magnetite Numerical methods Numerical models Oxidation Oxygen

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Sodium boiling will occur in some hypothetical accident cases (such as additional reactivity introduction and heat discharge capacity deterioration, and Local fault propagation). Thus sodium boiling experiments are necessary for the safety analysis and the development of serious accident programs in sodium-cooled fast re-actors. In the present study, the boiling two-phase heat transfer experiments of liquid sodium were carried out on the boiling liquid sodium test loop. The experimental results showed that the entire boiling process can be divided into four stages. The heat transfer coefficient of the boiling two phases in the rod bundle channel in-creases gradually with the increase of heat flux and grows very slowly with the increase of system pressure. Based on the 54 groups of rod channels obtained, the new correlation of transfer heat coefficient of boiling two-phase liquid sodium was developed in a 7-rod bundle. The new correlation can well predict the experimental data of boiling two-phase liquid sodium obtained by other scholars, and the prediction error is within +/- 50\% . Finally, mean relative deviation (MRD), absolute mean relative deviation (MARD), and root mean square deviation (RMSRD) were introduced to evaluate the accuracy of the correlation quantitatively.

Keyword ：

Boiling two-phase Correlation developed Heat transfer Liquid sodium Rod bundle

Cite：

Copy from the list or Export to your reference management。

Abstract ：

The two-phase pressure drop characteristics of liquid sodium are very significant for the safety and serious incident program development analysis of sodium-cooled fast reactor (SFR). In this paper, the boiling two-phase pressure drop experiments of liquid sodium were conducted in a 7-rod bundle with the mass flux range of 80 -390 kg/(m2.s), heat flux up to 120 kW/m2 and the absolute pressure range of 7.5 -100 kPa. The experimental results show that the frictional multiplier of boiling two-phase liquid sodium in the rod bundle channel decreases with the increase ofXLM. Some existing two-phase pressure drop correlations in the literatures were assessed and compared with the experimental data obtained in the present study. Results showed that these correlations could not predict the current experiments well because of the different geometries and measurements of high tem-perature environment. The new correlation for the two-phase friction multiplier of liquid sodium was developed in the 7 rod bundle. The predicted value of the new correlation was within 30 % of the experimental data in the rod bundle, which sufficiently demonstrates that the new correlation developed in this paper can well predict the boiling two-phase frictional pressure drop of liquid sodium in the rod bundle.

Keyword ：

Boiling two-phase Liquid sodium Pressure drop Rod bundle Two-phase friction multiplier

Cite：

Copy from the list or Export to your reference management。

Abstract ：

To improve the economy and safety of small pressurized water reactors (SPWRs) with flexible operating characteristics, the reactor power control system should process excellent robustness to provide satisfactory control performances at different operating conditions. This paper proposes four control strategies for reactor power control of SPWRs based on the linear quadratic Gaussian with loop transfer recovery (LQG/LTR) robust control method, including the single-loop reactor power feedback control (RPFC), single-loop average temperature feedback control, dual-loop feedback control, and modified dual-loop feedback control (MDFC) strategies. The corresponding LQG/LTR controllers in the reactor power control system of a SPWR were designed to assess the performance of the four control strategies. The simulation results show that the LQG/LTR controller with the MDFC strategy can provide good control performances for both reactor power and average coolant temperature among the four control strategies while the controller-based single-loop feedback control shows poor control of the reactor power or average coolant temperature. Meanwhile, compared with the existing conventional reactor power control system, the designed robust control system employing the MDFC strategy can provide better control performance for the reactor power and average coolant temperature in full-power operation of 100% to 90% rated power and low-power operation of 25% to 35% rated power with the differential control rod worth taken as 4 pcm/step and 24 pcm/step, indicating its effectiveness and superiority.

Keyword ：

LQG LTR reactor power control system robust control small pressurized water reactor

Cite：

Copy from the list or Export to your reference management。

Abstract ：

As a highly developmental potential propulsion technology, nuclear thermal propulsion (NTP) technology has characteristics of high power and high specific impulse. A large number of relevant studies for NTP reactor have been carried out, but most studies only focused on the overall reactor performance parameters, ignoring the core reactivity safety and local assembly behavior safety. In this study, a cross-scale neutronics, thermal hydraulic and mechanics coupling model of the core-assembly is established by using three-dimensional Monte Carlo code and commercial CFD program to analyze three aspects: reactor control response security characteristics, heat release homogeneity of reactor and thermal hydraulic parameters. By means of value comparison of control system, three-dimensional power flattening and sensitivity analysis of single variable thermal–hydraulic parameter, the thermal hydraulic temperature safety and mechanical thermal stress safety of assemblies are significantly improved under control safety and inherent safety, which proves the importance of the neutronics, thermal hydraulic and mechanics characteristic balance.This paper can provide a theoretical basis for study on the assembly multi-physics behavior and safety characteristics of NTP reactors. © 2022 Elsevier B.V.

Keyword ：

Control response security; Heat release homogeneity; Neutronics, thermal hydraulic and mechanics coupling model; Nuclear thermal propulsion; Thermal hydraulic parameters

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Solar interfacial evaporation is an attractive phenomenon for water treatment using renewable energy without further environmental contamination. However, the existing researches mainly focus on improving water evaporation rate with diversified interfacial and porous materials for solar absorption and water transport. The oil/water separation from emulsion under solar interfacial evaporation is rarely investigated. Under these cir-cumstances, a wood-melamine/calcium alginate composite structure with hydrophilic and oleophobic charac-teristics is designed and fabricated in the current work to realize solar interfacial evaporation based oil/water separation from emulsion. The corresponding oil/water separation process is experimentally analyzed under different material composite structures, solar intensities, and oil volume fractions. The wood-melamine/calcium alginate composite structure exhibits outstanding oil/water separation capability from emulsion under solar interfacial evaporation in comparison to the pure wood and wood-calcium alginate membrane structures owing to its fantastic oil resistance and water permeation properties. Through optimizing the thickness and aperture of hollow wood cylinder, a maximum interfacial water evaporation rate of 5.74 kg center dot m- 2 center dot h-1 is achieved under 5 sun solar intensity for oil/water separation. Besides, an outdoor experiment under natural sunlight (622 W center dot m- 2 to 769 W center dot m- 2) in summer time is also carried out for oil/water separation from emulsion using designed wood-melamine/calcium alginate composite under interfacial evaporation, and an average water evaporation rate of 0.965 kg center dot m- 2 center dot h-1 is obtained with condensed water on the hydrophobic glass cover for recovery. The current research paves an effective route for handling oil-in-water emulsion using renewable solar energy, contributing to the water resource protection and environmental sustainable development.

Keyword ：

calcium alginate composite Hydrophilic Oil Oleophobic Solar interfacial evaporation water separation from emulsion Wood-melamine

Cite：

Copy from the list or Export to your reference management。

Keyword ：

爆炸容器 粗糙度 丁腈橡胶 氟橡胶 高温性能 加工精度 压缩率

Cite：

Copy from the list or Export to your reference management。

Keyword ：

Yb:YAG晶体 发光光谱 空间分辨 时间宽度 衰减时间 相对发光效率

Cite：

Copy from the list or Export to your reference management。

Keyword ：

爆炸容器 粗糙度 丁腈橡胶 氟橡胶 高温性能 加工精度 压缩率

Cite：

Copy from the list or Export to your reference management。