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On 21 May 2021, an Mw 6.1 earthquake, causing considerable seismic damage, occurred in Yangbi County, Yunnan Province of China. To better understand the surface deformation pattern, source characteristics, seismic effect on nearby faults, and strong ground motion, we processed the ascending and descending SAR images using the interferometric synthetic aperture radar (InSAR) technique to capture the radar line-of-sight (LOS) directional and 2.5-dimensional deformation. The source model was inverted from the LOS deformation observations. We further analyzed the Coulomb failure stress (CFS) transfer and peak ground acceleration (PGA) simulation based on the preferred source model. The results suggest that the 2021 Yangbi earthquake was dextral faulting with the maximum slip of 0.9 m on an unknown blind shallow fault, and the total geodetic moment was 1.4 × 1018 Nm (Mw 6.06). Comprehensive analysis of the CFS transfer and geological tectonics suggests that the Dian–Xibei pull-apart basin is still suffering high seismic hazards. The PGA result demonstrates that the seismic intensity of this event reached up to VIII. The entire process from InSAR deformation to source modeling and strong ground motion simulation suggests that the InSAR technique will play an important role in the assessment of earthquake disasters in the case of the shortening of the SAR imaging interval.

In the hypothetical liquid metal reactor SGTR (Steam Generator Tube Rupture) accident, the high-pressure water in steam generator tube will be injected into the high-temperature liquid metal. During the water-liquid metal interaction, water vaporized and vapor bubbles migrated into liquid metal, which could be resulting a sharp pressure raise and threatening the safety of the reactor. This multi-phase system can be abstracted as a system in which a high-pressure subcooled fluid (overheating state at atmospheric pressure) is injected into another higher temperature fluid (normal pressure) to form a two-component (water and liquid metal) system in which multiphase (fluid and vapor) were existed. There are two effect could cause bubbles expansion which lead to overall system pressure increase, they are flash evaporation of pressurized water since the depressurization and high-temperature glycerin heating the water/vapor. In this paper, the theoretical analysis of the single bubble expansion model is used to evaluate the effect of these two phenomena on the system pressure rise. First of all, this paper uses the force balance point of view to derive the single bubble expansion equation inside the inviscid fluid, and obtain the relationship between bubble expansion speed and bubble internal pressure. Secondly, through conservative assumptions, the bubble expansion speed caused by the heating effect of the high temperature fluid on the bubble is evaluated. Finally, this paper compares the strength of these two effects in the expansion of a single bubble, and theoretically explains the driving force of the pressure increase in the simulation experiment and the potential flow pattern.

The critical heat flux (CHF) experiment for the reactor fuel assemblies (FAs) is the most difficult and important one in the reactor thermo-hydraulic study. The FA CHF experiments are performed on the large scale thermo-hydraulic test facilities with large DC power suppliers, complicated test sections and rigid test process. The results are analyzed with subchannel codes to obtain the parameters at the CHF point. Based on the experimental data, the CHF correlation is derived as the tool for the reactor safety analysis and design. After many years’ work, the common understanding of the FA CHF was established and the method of the FA CHF experiment becomes similar. This paper reviewed the progress of the FA CHF experiments, analyzed the modeling of the test sections, introduced requirement of the test facilities, and discussed the hypothesis in the modelling. The benchmark qualification test adopted to verify the test method and test section used in the experiment are discussed in the paper, too.

For the design verification and licensing of newly pressurized water reactors (PWRs), many integral test facilities were conducted. From the above integral test facilities, the obtained experimental results were adopted in the assessment and development of safety analysis codes. In this study, scaling analysis and design parameters of integral test facilities were summarized from the perspective of scaling method, basic scaling choice, equipment design, test matrix and application. The scaling method is the guideline for establishing scaling ratios of integral test facilities and different scaling methods were proposed. With the basic scaling choices of system pressure, geometrical parameters, working medium and equipment material, the design parameters of equipment were discussed. The test matrix and application of different integral test facilities were compared. This work is expected to sum up experience and provide guidance for the design and application of newly integral test facilities.

The thermal diffusion coefficient (TDC) is a dimensionless characteristic parameter to reflect the overall mixing characteristics in bundle channels. The effects of bundle geometries and spacer grids axial arrangement on TDC have not been systematically studied. Experimental study on the mixing characteristics of fuel assembly with 5×5 full-length bundles were carried out in two structural forms. The geometric parameters, mainly are the bundles radial power distribution and the form of spacer grids axial arrangement, which influence on the TDC of fuel assembly has been emphatically analysed. The experimental results show that the current FLLICA subchannel software cannot accurately simulate the transverse macroscopic flow in the subchannel matrix space. Without further optimization of subchannel software, the hot-cold bundles radial power distribution has a great influence on the TDC value of fuel assembly. The TDC value of fuel assembly is closer to true value when the hot-cold rods are centrally symmetrical. The mid-span mixing grid (MSMG) has a small enhancement effect on the thermal diffusion coefficient, and its contribution to the pressure drop of bundles is very low.

Safety systems play a key role in the nuclear industry. In the past decades, various safety systems have been designed and built to enhance safety level in nuclear power plants. The advanced secondary passive residual heat removal system (ASP) is one of several passive safety systems designed to ensure the safety of the reactor core. Experimental study on transient and steady-state characteristics as well as relevant influence factors of ASP system were conducted by using the high temperature high pressure thermal-hydraulic test facility. The results showed that the C-type heat exchanger could effectively remove the residual heat, and get stronger with the increase of loop pressure. The results also showed natural circulation could be set up with good stability, and get little influence from movement of isolating valves, relief valve as well as water volume in steam generator. Besides, to certificate the reasonability and reliability of the ASP system directly, an integral test was conducted.

The experimental investigation on transient heat transfer of supercritical water during depressurization in 2 × 2 bundle with wire wraps has been performed on the SWAMUP-II co-constructed by CGNPC and SJTU. The test section consists of two channels separated by a square steel assembly box with round corners. Water flows downward in the first channel and then turns upward in the second channel to cool the 2 × 2 bundle with wire wraps installed inside the assembly box. The bundle consists of four heater rods of 10 mm in O.D. arranged with pitch-to-diameter ratio of 1.18. Experimental parameter ranges cover pressure from 16 to 26 MPa, mass flux from 850 to 1450 kg/m 2 s, heat flux from 250 to 650 kW/m 2 , inlet fluid temperature from 345 to 365 °C, and depressurization rate of 1 and 2 MPa/min. The experimental data are obtained and heat transfer characteristics during depressurization from supercritical to sub-critical conditions are discussed. The fraction of heat transfer from inner channel to outer channel is lower than 15% under the test conditions. Four different transient heat transfer phenomena during depressurization are observed. The boiling crisis is likely to occur in SCWR during depressurization as the operating condition of SCWR is compared with the test condition. The boiling crisis is less likely to occur with the increase of mass flux, and more likely to occur with the increase of heat flux or inlet fluid temperature. The wall temperature increment during boiling crisis is smaller with higher mass flux, and larger with higher heat flux or inlet fluid temperature. The depressurization rate affects the transient heat transfer itself trivially.

An experimental study on transient heat transfer of supercritical water during pressure variation across critical pressure in a 2 × 2 rod bundle has been carried out on the Supercritical WAter MUltiPurpose test loop II (SWAMUP-II). The bundle consists of four heated rods with an Outer Diameter (O.D.) of 10 mm and a pitch-to-diameter ratio of 1.18. The 2 × 2 rod bundle with wire wrap is installed into a square assembly box. The experimental conditions are as follows: pressure ranging from 16 to 26 MPa, mass flux ranging from 850 to 1450 kg/m 2 s, heat flux ranging from 250 to 650 kW/m 2 , inlet fluid temperature ranging from 345 to 365 °C, and depressurization/pressurization rate of 1 MPa/min. The experimental data are obtained and the transient heat transfer characteristics during pressure variation across critical pressure are discussed. The heat transfer near the critical pressure is unstable as the physical properties of water changes fiercely, and the boiling crisis is likely to occur during both pressurization and depressurization, so the pressure range from 21 MPa to critical pressure is defined as a transition pressure section. The thermal-hydraulic parameters affect the transient heat transfer alike during both pressurization and depressurization, and obviously within the transition pressure section. The boiling crisis is more remarkable and the wall temperature increment is bigger with lower mass flux, higher heat flux or higher inlet fluid temperature. In order to avoid boiling crisis within the transition pressure section, the mass flux should be increase to or kept at higher level, the heat flux should be kept at or reduced fast to lower level, and the flow boiling should be kept at subcooled boiling.

Integral test plays essential role to assess the design of the emergency cooling system of nuclear reactors. Different from full height integral test facilities, reduced height integral test facilities have new problems on the pressure drop scaling. This paper mainly focuses on scaling of pressure drop across the core as it is the major pressure drop in primary loop. The analysis of pressure drop across the core has been divided into three terms and each term has been discussed separately based on two conditions: the normal operation condition and natural circulation condition. After that, the total pressure drop ratios under these two conditions have been discussed.

Both experimental and theoretical works had been done to study the effects of mixture parameters on the performance of corrugated plate (CP) dryer. A water-air experimental branch had been established to simulate water-steam separation in a CP dryer. The effect of ambient relative humidity on the dryer experiment is analyzed. The diameter distribution of water droplets in air-water mixture at (CP) dryer entrance was measured by laser particle size analyzer. The effects of droplet diameter, moisture content and mixture flow velocity on the separation efficiency, pressure drop and the re-entrainment were studied. At the same time, a theoretical model for trajectory tracking of water particle in CP channel was established to illustrate experimental results. The conclusion shows that: 1) this effect of ambient relative humidity cannot be ignored or error could be introduced to experimental results. 2) The separation efficiency increases with the increase of inlet particle size, increases with the increase of inlet moisture content and increases first and then decreases with the increase of inlet velocity. 3) Critical airflow speed of re-entrainment decreases as the inlet moisture content increases. 4) The pressure drop is exponentially increasing with inlet airflow speed.

The newly designed advanced secondary passive heat removal system (ASP) was one of the most important cooling systems to cope with station blackout (SBO) accident in the generation II + 1000 MWe PWR nuclear power plant (NPP). Advanced secondary passive heat removal system test facility (ASPTF) was constructed to obtain the operation performance of ASP under SBO conditions. The geometrical scaling ratio of ASPTF is 1/4 in the height and 1/208 in the volume with respect to the generation II + 1000 MWe PWR. The drag coefficient experiments were conducted to match the prototypical resistance characteristics of ASP in this paper firstly. Then, a prolonged SBO accident sequence was experimentally investigated in ASPTF. The experimental results reveal that the secondary side pressure of steam generator (SG) maintained at the set value in the early stage with the reciprocating opening of vapor discharge to atmosphere valve (VDA). After the startup of ASP, the secondary side pressure of SG decreased and heat generated in core simulator was effectively removed by natural circulation through ASP within 3 h (h) of the design value. Three hours later, the flow rate of ASP became unstable with the baring of heat exchanger (HX) tube. The stable natural circulation of ASP was recovered after the injection of water in the water tank (WT) after 4 h. A sensitivity investigation on operation performance of ASP also was performed based on RELAP5 code. This study not only helps to improve the understanding of important thermal hydraulic phenomena in ASP, but also sheds some lights on operation optimization for the PWRs with ASP.

The formation and control method of the coolant free surface is one of the key technologies for the design of windowless targets in the Accelerator Driven Systems (ADSs). In this work, a new design of windowless target for ADS based on upward swirling flow is proposed to form a stable free surface without recirculation zones. Experimental and numerical investigations on the free surface flow have been performed in a prototypical windowless target using water as working fluid. The experimental results show that a stable free surface is achieved when the mass flow rate is higher than 4.0 m3/h and the shape of free surface profile greatly depends on the inlet flow rate. CFD simulations have been carried out using VOF method with different turbulent models. The numerical results show that the prediction of BSL Reynolds stress model agrees qualitatively well with the experimental results. The free surface profile of Lead–Bismuth-Eutectic (LBE) in the windowless target is very similar to that of water according to the simulation results. The feasibility of the new windowless target for ADS based on upward swirling flow is preliminary validated.

Through the analysis of monitoring data with a time interval of 10 min during the rainy season of 2012, for three points of G37, zk8 and zk7 which are located on the main conduit of Zhaidi karst underground river system, the variation features of water level and hydraulic gradient are studied and the relations are established between gradient and water level or amplitude. (1) It is first discovered that there are different function relations such as linear, parabola and inverse parabola between the G37’s water level and the hydraulic gradients of different conduit part. (2) The peak delay times for water level curves are

The effects of Y2O3 on the microstructure, phase composition of the coatings, microhardness and wear resistance of cobalt-based composite coatings prepared by laser cladding were investigated. The TA15 titanium alloy was selected as substrate which the cobalt-based composite powder with different content of Y2O3 was cladded on. The microstructure of the coatings was observed by scanning electron microscope (SEM) and metallurgical microscope. The phase structure of the coatings was determined by X-ray diffraction (XRD), and the microhardness and wear resistance of the coatings were measured by hardness tester and wear testing machine. The results show that the rare earth oxide Y2O3 can refine and purify the microstructure of the coatings, reduce the porosities and cracks and improve compactness of the coatings. Moreover the addition of Y2O3 improves the microhardness of the coatings and reduces the friction coefficient, thus improving the wear property of the coatings. And the wear resistance of the coating with Y2O3 has improved about 50 times; the highest value of microhardness in the coating is HV1181.1. And 0.8 wt% content of Y2O3 in the coating is the best choice for improving the microhardness and wear resistance of the coating. It is feasible to improve the microstructure and tribological properties of laser cladding coatings by adding of Y2O3. Copyright © 2014 John Wiley & Sons, Ltd.

Experimental investigation was performed on the critical heat flux (CHF) in thin rectangular channels with very wide mass velocity range at low pressures. Different test sections were adopted with the different heated length and heated width. Both the vertical upward flow and downward flow were tested during the experiment. The results prove that the effect of the heated length on the CHF exists in the high mass velocity test but it is not very strong. The CHF rises with shorter heated length. At low mass velocities, the CHF at downward flow is much lower than that at upward flow. Empirical correlations were compared with the experimental data both from present and others’ studies. Empirical correlations provided by Katto and Gambill gave out good prediction for the low upflow and the high downflow respectively. The Sudo correlation had wide flow range but it overestimated at low mass velocity and underestimated at high mass velocity. A new CHF correlation for the large flow rate shows good agreement with the present and others’ studies. High pressure drop was found in the experiment at high flow rate conditions. It was analyzed and discussed in the paper.

Separated heat pipe is an efficient passive heat transfer device. It is widely used in chemical and aerospace industry. In this paper, the heat transfer characteristics of the separated heat pipes which applied to containment cooling system were studied. According to the experimental data, the influences of the system pressure, the initial vacuum degree of the system, and the system resistance coefficient on the heat transfer capability of the separated heat pipes were analyzed. Based on the theoretical analysis, the correlation for the natural circulation flow rate of the system was obtained. Relative errors of experimental test data were less than ±20 %. Comparing the experimental data with the calculated results, it shows that main parameters that affect the heat transfer capability of the heat pipe loop are system state parameters (including system pressure, the temperature difference between heat source and heat sink as well as the resistance coefficient) and system boundary conditions (including noncondensable gas percentage and system boundary pressure). Natural circulation flow rate increases with the increase of the system pressure and the initial vacuum degree of the system.