A Series Dissertation on Tianwan Nuclear Power Station —Technical Characteristics

This is the３rd topic of“A series dissertation on Tianwan Nuclear Power Station”,which focuses on the technical characteristics．The type of this Nuclear Power Station is a Russian AES-９１（WWER-１０００/ V４２８）pressurized water reactor（PWR）nuclear power unit．It is an improved concept by the Russian Saint Petersburg Nuclear Power Research and Design Institute based on the experiences in design,construction and operation of WWER-１０００/V３２０units．Since WWER-１０００/V３２０is a mature type which has more than２６０ reactor-year operation experiences,the author guesses the technical characteristics of WWER-１０００/V３２０are well known,thus the comparison of their technical characteristics is described bellow．     

Reliability studies of Cu/Al joints brazed with Zn–Al–Ce filler metals

This paper examines the effect of different Ce content on the properties and microstructures of Zn–22Al filler metals and Cu/Al brazing joints. The results indicate that, the spreading area on Cu substrates of Zn–22Al filler metal could be improved by 29.7% with the addition of 0.03 wt% Ce, whereas the oxidation resistance of the alloy increased significantly. The thermal behaviors of Zn–22Al filler metals were minimally influenced by the addition of Ce. The Zn–22Al–xCe filler metals show finer and more uniform microstructures when the added Ce content is in the range 0.03–0.05 wt%. Particularly, the addition of trace Ce into the Zn–22Al filler metal can refine the microstructures and decrease the thickness of the layer of intermetallic compounds produced in the Cu/Al brazing joints. Some bright (Zn,Al)–Ce intermetallic compounds particles were observed in the alloy when the Ce content exceeds 0.08 wt%. The results also indicate that the shear strength of Cu/Al joint brazed with Zn–22Al–0.05Ce is 30.3% higher than that of the Zn–22Al filler metal. Some hard and brittle Ce-bearing intermetallic compounds particles appear in the fracture surface when the Ce content is 0.25 wt%, which resulted in the weakening of the mechanical properties of Cu/Al brazing joints.     

Application of FTA Method to Reliability Analysis of Vacuum Resin Shot Dosing Equipment

1　ＩｎｔｒｏｄｕｃｔｉｏｎＦＴＡ (ｆａｕｌｔｔｒｅｅａｎａｌｙｓｉｓ)ｉｓａｎａｎａｌｙｓｉｓｍｅｔｈｏｄｂｙｗｈｉｃｈｃａｕｓｅｓｏｆａｓｙｓｔｅｍ’ｓｆａｕｌｔｓｃａｎｂｅａｎａ ｌｙｚｅｄｓｙｓｔｅｍａｔｉｃａｌｌｙｉｎｔｈｅｆｏｒｍｏｆａｔｒｅｅａｎｄｔｈｅｒｅｌｉａｂｉｌｉｔｙｏｆｔｈｅｓｙｓｔｅｍｃａｎｂｅｅｖａｌｕａｔｅｄ .Ｔｈｉｓｍｅｔｈｏｄｂｅｇｉｎｓｗｉｔｈｔｈｅｍｏｓｔｕｎｄｅｓｉｒａｂｌｅｓｔａｔｅｏｆｔｈｅｓｙｓｔｅｍａｎｄｔｒａｃｅｓｖａｒｉｏｕｓｆａｃｔｏｒｓ (ｉｎ…     

A New Analysis of Hydrogen Diffusion in Metals with Trapping

A new model of hydrogen diffusion in metalshas been developed,it is more efficient todescribe the hydrogen diffusion with trappingin metals.In the model newly developed an impli-cit dependence on time of hydrogen diffusioncoefficient in metals with trapping was firstlybuilt and it is shown that hydrogen diffusioncoefficient will be different at different posi-tions in a dynamic process of hydrogen diffusionin a metal.Numerical solutions of the present modelwere obtained by finite difference method.Bychanging the parameters in the model the diffusionof hydrogen in a metal and the effect of trappingwere described and discussed.And the comparisonbetween the well known McNabb and Foster's modeland the present model was also made.     

New application of plate–fin heat exchanger with regenerative cryocoolers

A design idea is newly proposed and investigated for the application of plate–fin heat exchanger (PFHX) with regenerative cryocoolers. The role of this heat exchanger is to effectively absorb heat from the stream of coolant and deliver it to the cold-head of a cryocooler. While various types of tubular HX’s have been developed so far, a small PFHX could be more useful for this purpose by taking advantage of compactness and design flexibility. In order to confirm the feasibility and effectiveness, a prototype of aluminum-brazed PFHX is designed, fabricated, and tested with a single-stage GM cryocooler in experiments for subcooling liquid nitrogen from 78 K to 65–70 K. The results show that the PFHX is 30–50% more effective in cooling rate than the tubular HX’s. Several potential applications of PFHX are presented and discussed with specific design concepts.     

A New Model for Predicting Ternary Thermodynamic Properties of Solution Phase and Its Application

A new geometric asymmetric model for predicting the thermodynamic properties of ternary systemfrom three sub-binaries is presented in this paper.Its analytical expression with good calculating ac-curacy is most simple in all asymmetric models.The new model was applied to predict the enthalpiesof mixing of the Bi-Ga-Sn.Au-Ag-Sn and NaCl-KCl-CaCl_2 ternary systems which were in goodagreements with experimental data.Based on thermodynamic principles,the importance of thechoice of asymmetric component is also discussed.The error analysis indicates that in the case ofjudging the asymmetric component in ternary system according to the thermodynamic criterion thedeviation is minimum.It is of great significance to improve the calculating accuracy for predictingthermodynamic properties of ternary solution phase from the sub-binary ones.     

Application of response surface methodology with a Box–Behnken design for struvite precipitation

Struvite crystals were precipitated by the reaction of magnesium chloride hexahydrate and ammonium dihydrogen phosphate using different concentrations of citric acid as the additive (100, 300, and 500 ppm). The structure, morphology, functional groups and particle size of the crystals were evaluated experimentally by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and particle size analysis. The experimental results demonstrated that citric acid exerted a significant influence on the struvite precipitation and the crystal morphology changed from rod-like to tubular shaped with a larger size and hollow bodies. The average particle size changed from 17.60 to 33.60 μm with increasing citric acid concentration. The results of FTIR suggested that the citric acid adsorbed on the crystal surface. Following the characterization of the crystals prepared using different concentrations of citric acid, the response surface methodology coupled with Box-Behnken design were applied as a statistical tool to determine the effects of the key parameters affecting the precipitation process (temperature, pH and additive concentration) on the responses (namely, particle size and specific cake resistance of struvite). Second-order polynomial equations for both responses were improved to correlate the parameters. Analysis of variance (ANOVA) showed a significant quadratic regression model with high coefficients of the determination values. The optimum conditions for particle size were found to be 60 °C, pH 8 and 500 ppm additive concentration.     

Application of Fuzzy Control into a New Kind of Sea Water Still

ＡｐｐｌｉｃａｔｉｏｎｏｆＦｕｚｚｙＣｏｎｔｒｏｌｉｎｔｏａＮｅｗＫｉｎｄｏｆＳｅａＷａｔｅｒＳｔｉｌＱｕＷｅｉｄｏｎｇＹｕＪｉｎｄｉＺｈａｎｇＨｅｆｅｉＮｏｒｔｈｗｅｓｔｅｒｎＰｏｌｙｔｅｃｈｎｉｃａｌＵｎｉｖｅｒｓｉｔｙＸｉ′ａｎ７１００７２，Ｐ...     

Transmission network of the 2014–2015 Ebola epidemic in Sierra Leone

Understanding the growth and spatial expansion of (re)emerging infectious disease outbreaks, such as Ebola and avian influenza, is critical for the effective planning of control measures; however, such efforts are often compromised by data insufficiencies and observational errors. Here, we develop a spatial–temporal inference methodology using a modified network model in conjunction with the ensemble adjustment Kalman filter, a Bayesian inference method equipped to handle observational errors. The combined method is capable of revealing the spatial–temporal progression of infectious disease, while requiring only limited, readily compiled data. We use this method to reconstruct the transmission network of the 2014–2015 Ebola epidemic in Sierra Leone and identify source and sink regions. Our inference suggests that, in Sierra Leone, transmission within the network introduced Ebola to neighbouring districts and initiated self-sustaining local epidemics; two of the more populous and connected districts, Kenema and Port Loko, facilitated two independent transmission pathways. Epidemic intensity differed by district, was highly correlated with population size (r = 0.76, p = 0.0015) and a critical window of opportunity for containing local Ebola epidemics at the source (ca one month) existed. This novel methodology can be used to help identify and contain the spatial expansion of future (re)emerging infectious disease outbreaks.     

On the interaction of Class C fly ash with Portland cement–calcium sulfoaluminate cement binder

Shrinkage cracking in concrete is a widespread problem, especially in concrete structures with high surface-to-volume ratio such as bridge decks. Expansive cements based on calcium sulfoaluminate phase were developed to mitigate the shrinkage cracking of concrete. The compressive stress induced due to restrained expansion of concrete has been shown to counteract the tensile stress generated during drying shrinkage. This research attempts to address the differential behavior of fly ash type (i.e., Class C vs. Class F) on early-age expansion and hydration characteristics of ordinary Portland cement (OPC)–calcium sulfoaluminate (CSA) cement blend. It was observed earlier that the presence of Class C fly ash (CFA), unlike Class F fly ash, shortened the expansion duration of OPC–CSA cement blend, which was hypothesized to be correlated to early depletion of gypsum. This paper presents a detailed verification of the hypothesis. Addition of external gypsum to OPC–CSA–CFA blend led to simultaneous increase in expansion and disappearance of a shoulder peak in the calorimetric curve. Thermodynamic calculations using a geochemical modeling program (GEMS-PSI) revealed higher saturation levels of ettringite in presence of external gypsum, which led to higher crystallization stress, and thereby increased expansion.     

A Study on the Reliability of a Large Vibration Machine

1　ＩｎｔｒｏｄｕｃｔｉｏｎＬａｒｇｅｖｉｂｒａｔｉｏｎｍｉｌｌｓａｒｅａｐｐｌｉｅｄｗｉｄｅｌｙｉｎｃｏａｌａｎｄｂｕｉｌｄｉｎｇｍａｔｅｒｉａｌｓｉｎｄｕｓｔｒｉｅｓ .Ｔｈｅｂｉｇｇｅｓｔｖｏｌ ｕｍｅｏｆｍｉｌｌｓｍａｄｅｉｎＣｈｉｎａｉｓ 2 .8ｍ3ｔｉｌｌｎｏｗ .Ｂｅｃａｕｓｅｉｔｓｍａｉｎｃｏｍｐｏｎｅｎｔｓｂｅａｒａｌｔｅｒｎａｔｉｎｇｌｏａｄｉｎｒｕｎｎｉｎｇ ,ｔｈｅｃｏｍｍｏｎｆａｉｌｕｒｅｍｏｄｅｌｉｓｏｆｆａｔｉｇｕｅ .Ｉｎｏｒｄｅｒｔｏｉｎｃｒｅａｓｅｔｈｅｒｅｌｉａｂｉｌｉｔ…     

Application of time–temperature–stress superposition on creep of wood–plastic composites

Time–temperature–stress superposition principle (TTSSP) was widely applied in studies of viscoelastic properties of materials. It involves shifting curves at various conditions to construct master curves. To extend the application of this principle, a temperature–stress hybrid shift factor and a modified Williams–Landel–Ferry (WLF) equation that incorporated variables of stress and temperature for the shift factor fitting were studied. A wood–plastic composite (WPC) was selected as the test subject to conduct a series of short-term creep tests. The results indicate that the WPC were rheologically simple materials and merely a horizontal shift was needed for the time–temperature superposition, whereas vertical shifting would be needed for time–stress superposition. The shift factor was independent of the stress for horizontal shifts in time–temperature superposition. In addition, the temperature- and stress-shift factors used to construct master curves were well fitted with the WLF equation. Furthermore, the parameters of the modified WLF equation were also successfully calibrated. The application of this method and equation can be extended to curve shifting that involves the effects of both temperature and stress simultaneously.     

Reliability modelling with redundancy—A case study of power generation engines in a wastewater treatment plant

Power generators are critical assets in wastewater treatment plants (WWTPs) in Australia and many countries. Better managing the lifetime, minimising failures, improving reliability and availability, and reducing operating and maintenance costs of the power generation assets are still challenging topics for water utilities. This case study aims to develop power generation system reliability and availability modelling considering redundancy to minimise operation and maintenance costs. The two-parameter Weibull model was used to assess system reliability and availability to power generation engines in WWTPs. The Kaplan-Meier method (a time-driven estimation technique) and the log beta-Weibull model (which is suitable for modelling censored and uncensored data) were used to analyse and validate the modelling results. Shape and scale parameters of the Weibull models were estimated by maximising the log-likelihood function using non-linear optimisation. Hazard and reliability functions were calculated using the Weibull model. Results using two-parameter Weibull, Kaplan-Meier, and log beta-Weibull models display low reliability and high hazard rate over time, which was associated with spark plug failure due to a suboptimal start and stop operation strategy.     

Natural Host–Environmental Media–Human: A New Potential Pathway of COVID-19 Outbreak

Identifying the first infected case (patient zero) is key in tracing the origin of a virus; however, doing so is extremely challenging. Patient zero for coronavirus disease 2019 (COVID-19) is likely to be permanently unknown. Here, we propose a new viral transmission route by focusing on the environmental media containing viruses of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or RaTG3-related bat-borne coronavirus (Bat-CoV), which we term the “environmental quasi-host.” We reason that the environmental quasi-host is likely to be a key node in helping recognize the origin of SARS-CoV-2; thus, SARS-CoV-2 might be transmitted along the route of natural host–environmental media–human. Reflecting upon viral outbreaks in the history of humanity, we realize that many epidemic events are caused by direct contact between humans and environmental media containing infectious viruses. Indeed, contacts between humans and environmental quasi-hosts are greatly increasing as the space of human activity incrementally overlaps with animals’ living spaces, due to the rapid development and population growth of human society. Moreover, viruses can survive for a long time in environmental media. Therefore, we propose a new potential mechanism to trace the origin of the COVID-19 outbreak.     

A–BTransition of Superfluid 3He with a Film Geometry

We have performedcwNMR experiments on superfluid ³ He confined to a parallel-plate geometry with a m scale spacing for a wide pressure range. A static field was applied parallel or perpendicular to the plate surface. The spectra of two absorption signals, a main and a satellite, have been observed below the superfluid transition temperature in a parallel field. As the temperature decreased, the main signal decreased with shifts to higher frequencies, and the satellite grew with shifts to much higher frequencies. From the temperature dependence of these signals and the result in the perpendicular field, it is confirmed that the main signal and the satellite correspond to the A phase signal (ABM state) and the B phase signal (BW state), respectively. The temperature dependence of the two signals indicates that a phase transition from the A phase to the B phase occurs with decreasing temperature. By analyzing these signals, we determine A–B transition temperatures experimentaly. TheA–Btransition temperature normalized by the superfluid transition temperature is 0.95 at 20 bar, and decreased further to 0.70 at 0 bar for a thickness of 0.88 m for pure ³ He. The values of T_AB/T_C were slightly elevated when covering the surface with 4.5 layers of ⁴ He film, which suggests that this transition is also influenced by the surface condition.     

Reliability studies of Sn–9Zn/Cu and Sn–9Zn–0.3Ag/Cu soldered joints with aging treatment

In this study, the interfacial reactions and joint reliabilities of Sn–9Zn/Cu and Sn–9Zn–0.3Ag/Cu were investigated during isothermal aging at 150 °C for aging times of up to 1,000 h. Cu₅Zn₈ IMCs layer is formed at the as-soldered Sn–9Zn/Cu interface. Adding 0.3wt.% Ag results in the adsorption of AgZn₃ on the Cu₅Zn₈ IMCs layer. The as-soldered Sn–9Zn/Cu and Sn–9Zn–0.3Ag/Cu joints have sufficient pull strength. The thickness of the IMCs layer formed at the interface of Sn–9Zn/Cu and Sn–9Zn–0.3Ag/Cu both increase with increasing aging time. Correspondingly, both the pull forces of the Sn–9Zn and Sn–9Zn–0.3Ag soldered joints gradually decrease as the aging time prolonged. However, the thickness of the IMCs layer of Sn–9Zn–0.3Ag/Cu increases much slower than that of Sn–9Zn/Cu and the pull force of Sn–9Zn–0.3Ag soldered joint decreases much slower than that of Sn–9Zn soldered joint. After aging for 1,000 h, some Cu–Sn IMCs form between the Cu₅Zn₈ IMC and the Cu substrate, many voids form at the interface between the Cu₅Zn₈ layer and solder alloy, and some cracks form in the Cu₅Zn₈ IMCs layer of Sn–9Zn/Cu. The pull force Sn–9Zn soldered joint decreases by 53.1% compared to the pull force measured after as-soldered. Fracture of Sn–9Zn/Cu occurred on the IMCs layer on the whole and the fracture micrograph implies a brittle fracture. While the pull force of Sn–9Zn–0.3Ag soldered joint decreases by 51.7% after aging at 150 °C for 1,000 h. The fracture mode of Sn–9Zn–0.3Ag soldered joint is partially brittle at the IMCs layer, and partially ductile at the outer ring of the solder.     

A study of high-temperature precipitation in Al–Mg–Si alloys with an excess of silicon

The high-temperature decomposition phenomena were examined for two Al–Mg–Si alloys with an excess of silicon. The kinetics of precipitation were studied by transmission electron microscopy and by measurement of the thermoelectric power in the temperature range from 300 to 525 °C. It was shown that decomposition occurs either at 300–400 °C by the precipitation of intermediate phase (different structures are possible depending on the alloy), which is then gradually replaced by the equilibrium phase or, between 400 and 500 °C, by direct precipitation of the phase from the supersaturated solid solution. The precipitation of silicon was also observed. At 300–350 °C, a near equilibrium in composition solid solution can coexist with Mg2Si phases out of equilibrium. Structures of intermediate phases and their orientation relationships with the matrix are given. The diagram of isothermal precipitation is constructed as an S-curve.