Investigation of a reactor coolant pump seal from Indian Point Unit No. 2

A failure investigation was performed on a Westinghouse reactor coolant pump seal from the Indian Point No. 2 Nuclear Power Station. The investigation consisted of visual inspection and SEM/EDS evaluation of the rubber seals associated with the main seal. No operating/leakage history was available for the seal evaluated. The conclusions drawn from the investigation were that the only damage to sealing surfaces appeared to be associated with the rubber products (no obvious metal wear) which had their effective cross-sections severely worn. The report recommends the feasibility of only replacing the rubber components and the minimization or elimination of dry starts on the seals.     

Thermal modeling and operating tests for the gas engine-driven heat pump systems

Gas engine-driven heat pump (GEHP) is a heating and cooling system with the advantage of reducing the electric power in both heating and cooling modes of operation.     

Solar powered induction motor-driven water pump operating on a desert well, simulation and field tests

A photovoltaic-powered water pumping system, employing an induction motor pump, capable of supplying a daily average of 50 m³ at 37-m head has been developed. The system was installed on a desert well in Jordan, where: the average solar radiation amount to 5.5 kW h/m³/day, to provide the Bedouins living in the well area with drinking water.A mathematical model to enable testing the system performance by computer simulation was developed. This model allows the representation of motor torque in function of speed (and slip) at different supply frequencies, as well as the flow rate and efficiency of the system in function of supply frequency and pumping head.Prior to its installation on the desert well, the system performance, in accordance with frequency and head, was thoroughly tested in the laboratory. As illustrated in this paper, simulation and laboratory testing results are well matched. At constant pumping head, the flow rate is proportional to the supply frequency of the motor. At constant flow rate, the pumping head is proportional to the supply frequency squared only in the range below the peak efficiency of the pump. For higher flow rate values, a special algorithm based on the experimental results could be developed.Higher system efficiency is achievable at higher frequency. It is advisable to operate the motor pump at the nominal frequency, flow rate and head corresponding to maximum efficiency.Long-term field testing of the system shows that it is reliable and has an overall efficiency exceeding 3%, which is comparable to the highest efficiencies reported elsewhere for solar powered pumps.     

Production of synthesis gas by co-gasifying coke and natural gas in a fixed bed reactor

The production of synthesis gas has gained increasing importance because of its use as raw material for various industrial syntheses. In this paper synthesis gas generation during the reaction of a coal/methane with steam and oxygen, which is called the co-gasification of coal and natural gas, was investigated using a laboratory scale fixed bed reactor. It is found that about 95% methane conversion and 80% steam decomposition have been achieved when the space velocity of input gas (oxygen and methane) is less than 200 h⁻¹ and reaction temperature about 1000 °C. The product gas contains about 95% carbon monoxide and hydrogen. The reaction system is near the equilibrium when leaving the reactor.     

Characterization of an ammonia decomposition process by means of a multifunctional catalytic membrane reactor

Ammonia decomposition was studied in a multifunctional catalytic membrane reactor filled with Ruthenium catalyst and equipped with palladium-coated membranes. To characterize the system we measured NH₃ conversion, H₂ yield and its partial pressure, the internal and external temperatures of the reactor shell and the electric consumption under several NH₃ flow and pressure conditions. Experimental results showed that the combined effect of Ruthenium catalyst and palladium membranes allowed the reaction to reach the equilibrium in all the conditions we tested. At 450 °C the ammonia conversion resulted the most stationary, while at 7 bar the hydrogen yield was almost independent of both the ammonia flow and temperature. In addition, the experimental system used in this work showed high values of NH₃ conversion and H₂ permeation also without heating the ammonia tank and therefore renouncing to control the feeding gas pressure. When ultra-pure hydrogen is needed at a distal site, a reactor like this can be considered for in situ hydrogen production.     

Hydrogen enrichment and separation from synthesis gas by the use of a membrane reactor

One of the objectives of the CHRISGAS project was to study innovative gas separation and gas upgrading systems that have not been developed sufficiently yet to be tested at a demonstration scale within the time frame of the project, but which show some attractive merits and features for further development. In this framework CIEMAT studied, at bench scale, hydrogen enrichment and separation from syngas by the use of membranes and membrane catalytic reactors.In this paper results about hydrogen separation from synthesis gas by means of selective membranes are presented. Studies dealt with the evaluation of permeation and selectivity to hydrogen of prepared and pre-commercial Pd-based membranes. Whereas prepared membranes turned out to be non-selective, due to discontinuities of the palladium layer, studies conducted with the pre-commercial membrane showed that by means of a membrane reactor it is possible to completely separate hydrogen from the other gas components and produce pure hydrogen as a permeate stream, even in the case of complex reaction system (H₂/CO/CO₂/H₂O) under WGS conditions gas mixtures.The advantages of using a water-gas shift membrane reactor (MR) over a traditional fixed bed reactor (TR) have also been studied. The experimental device included the pre-commercial Pd-based membrane and a commercial high temperature Fe–Cr-based, WGS catalyst, which was packed in the annulus between the membrane and the reactor outer shell. Results show that in the MR concept, removal of H₂ from the reaction side has a positive effect on WGS reaction, reaching higher CO conversion than in a traditional packed bed reactor at a given temperature. On increasing pressure on the reaction side permeation is enhanced and hence carbon monoxide conversion increases.     

Transient flow and heat transfer of liquid sodium coolant in the outlet plenum of a fast nuclear reactor

A calculation procedure for axisymmetric elliptic flows is applied to predict the transient velocity and temperature fields of a heavy fluid jet issuing vertically into a volume of relatively light fluid. This situation arises in the outlet plenum of a Liquid-Metal-Cooled Fast Breeder Reactor (LMFBR) during reactor transients. The time averaged conservation equations for momenta and heat transfer were solved on a CDC 6600 digital computer for various plenum inlet transients, along with a two-equation model of turbulence and proper modelling of the buoyancy terms. Predictions are presented of flow and heat transfer in the form of velocity vector plots and temperature contours. Predictions are in qualitative agreement with expectations, invariably establishing that the flow by-passes the outlet plenum.     

Dynamic analysis of a primary reactor coolant system subjected to seismic and LOCA loads,including shield building interaction

This paper is intended to describe the development of a unique method of analysis for a primary reactor coolant piping system to evaluate its adequacy and the need for structural support system optimisation under hypothetical seismic and loss-of-coolant-accident loading conditions. An integrated approach is presented for a linear three-dimensional dynamic analysis of a typical 900 MWe PWR nuclear reactor coolant loop, accommodating dynamic coupling and interaction effects of shield building, including soil-foundation springs and damping parameters. Also included are major influences on sensitive equipment due to their variable support boundary conditions and rigid restraints. Due to the vital nature of reactor coolant systems, important dynamic design criteria have to be established in order to estimate natural frequencies, damping characteristics and overall system behaviour during LOCA and strong motion earthquakes as well as to optimise the structural design of various components.     

基于可调谐半导体激光吸收光谱技术的甲烷遥测方法的研究

介绍了一种基于TDLAS技术的望远镜收发系统的设计原理,通过对吸收池内标准浓度CH4的测量,标定了测量的准确性。在此基础上,对40 m的开放光程下CH4进行不同工况测量,验证了系统具有良好的时间响应性。系统的最小可探测极限约为5.48×10-5m/m。研究证明,该系统可以满足工业气体的在线监测需求。此外,该系统还可以方便用于远程监测H2S、CO、NH3等危险性气体的泄露。     

Lab and field tests of a self-tuning power system stabilizer

Digital power system stabilizers have opened new avenues for applying innovative control strategies to damp generator rotor oscillations at steam and hydroelectric power plants. This paper describes test results from simulation studies and field tests where a self-tuning control algorithm was tested using a digital stabilizer. The simulation studies indicated a marked improvement in local mode damping and a contribution to damping at the inter-area mode while initial tests at power plants gave promising results     

生物质热解气重整试验平台设计与试验

针对热解气焦油含量高、热值低的问题,文章基于焦油催化裂解和热解气气化重整原理,提出了生物质热解气重整工艺路线,并设计、搭建了生物质热解气重整试验平台,该试验平台主要由热解、催化重整、产品收集、控制系统等组成。以玉米秸秆为原料,在该试验平台上开展了热解气重整试验,试验结果表明:在以石英砂作为惰性材料的条件(高温裂解)下,热解气产率为33.8%,焦油转化率为64.3%;在玉米秸秆炭催化裂解条件下,热解气产率为37.8%,焦油转化率72.6%;高温裂解和催化裂解条件下生成的热解气的热值均达到了17MJ/m3以上。热解气重整试验平台达到了设计目的,为热解气重整研究提供了理论支持和技术支撑。     

Summary of theoretical and experiment development of a novelelectromagnetic technique for remote repositioning of coolant tubespaces in CANDU nuclear reactors

The authors describe the experimental and theoretical development of a novel electromagnetic method to reposition the spacers used between the pressure and calandria tubes in a CANDU nuclear reactor without dismantling the fuel channels. The method was successfully developed and implemented to reposition the dislocation spacers in five CANDU reactors in Ontario,. The savings in reactor repair costs, interest charges, and replacement energy costs were on the order of hundreds of millions of dollars. There are a number of other applications of the electromagnetic technique which may also benefit from the analysis and experimental development, especially for pulse power, electromagnetic metal forming, and fusion technologies     

Analysis of a 2-D model of a packed bed reactor for methanol production by means of CO2 hydrogenation

In recent years, methanol received the attention of many researchers as a building block of the circular economy, because of its diversified applications in different areas. Generally, methanol is produced by syngas, however recent studies are dealing with its production via carbon dioxide hydrogenation. With the aim to predict conversions, efficiencies as well as concentration, pressure and temperature profiles inside the packed bed methanol reactor, mathematical models are developed in one- (1-D) and two- (2-D) dimensions. However, a deep study about a 2-D mathematical model and conditions where its use is advisable to get reliable predictions is missing in the literature. In this research, a two dimensional model for methanol reactor via carbon dioxide hydrogenation is suggested, comparing a structured catalytic packing with a more common packed bed of catalyst pellets, which differ mainly for the respective thermal conductivity. The system of partial differential equations is solved in MATLAB® and the same operating conditions set in a previous work about a one dimensional model are considered. Results show that the 2-D model is useful for both reactor typologies under the examined operating conditions, although definitely more important for the non-structured reactor, where higher temperature and concentration differences on tube cross sections are calculated because of a stronger resistance to radial heat transfer. In addition, a higher efficiency is predicted for a structured reactor in terms of carbon dioxide selectivity to methanol and methanol yield, then a lower recycle flow rate is required in this case. A sensitivity analysis is also developed for the two reactor typologies, changing feed inlet temperature, wall heat transfer coefficient and tube diameter. Conditions are investigated, for which 2-D model results tend to corresponding outputs of a 1-D model.     

A chemical heat pump using hydration of mgo particles in a three-phase reactor

A chemical heat pump using hydration of magnesium oxide in a three-phase reactor is proposed. Magnesium oxide particles suspended in the triethylene glycol are hydrated exothermally by introducing water vapour. The hydration rate was measured under the temperatures ranging from 383 K to 523 K. It was found that the reaction rate was proportional to the amount of adsorbed water molecules, and correlated in an equation.     

The field performance of a remote 10 kW wind turbine

The collection and analysis of 15 months of continuously recorded field data from a small remote wind–diesel power system at a coastal farm site are reported. The paper focuses on the available wind data and the performance of the 10 kW Bergey wind turbine.     

Transient flow field and performance analysis of a claw pump for FCVs

The claw-type hydrogen pump has been applied in fuel cell vehicles (FCVs) because of its compact structure, high reliability, and oil-free quality. In this study, a three-dimensional transient computational fluid dynamics (CFD) modelling of a claw-type hydrogen pump used in FCVs was established. Hexahedral structured grids were generated and updated at an increment of 3° in rotating angle to ensure the mesh quality of the whole solving process. The leakage of radial clearance (RC) and axial clearance (AC) was considered. The presented modelling and simulation methods were validated by operating a claw pump at different pressure ratios. The pressure and velocity vector fields in both AC and middle plane, along with the mechanism of the fluid field distribution were analyzed in detail. The in-depth relationship amongst the fluctuation of discharge pressure, outlet mass flow rate and discharge area during the whole working process was revealed. P-θ and V-θ diagram of the whole operating cycle were analyzed. The influence of AC and RCs respectively on the volumetric efficiency of a claw pump was compared and evaluated. It is concluded that back flow in suction pipe happened near 360° as part of the discharge chamber was cut off from the exhaust port and high pressure gas from carryover flowed back into the inlet pipe. The pressure increase during the displacement process, theoretically zero, is actually significant and even comparable to the pressure increase during the compression and discharge process. In addition, volumetric efficiency is most sensitive to axial clearance, followed by radial clearance between rotor and casing, while radial clearance between the rotors has the least influence.     

Thermal performance of a packed bed reactor for a high‐temperature chemical heat pump

The thermal performance of a chemical heat pump that uses the reaction system of calcium oxide/lead oxide/carbon dioxide, which is developed for utilization of high‐temperature heat above 800°C, is studied experimentally. The thermal performance of a packed‐bed reactor of a calcium oxide/carbon dioxide reaction system, which stores and transforms a high‐temperature heat source in the heat pump operation, is examined under various heat pump operation conditions. The energy analysis based on the experiment shows that it is possible to utilize high‐temperature heat with this heat pump. This heat pump can store heat above 850°C and then transform it into a heat above 900°C under an approximate atmospheric pressure. An applied system that combines the heat pump and a high‐temperature process is proposed for high‐efficiency heat utilization. The scale of the heat pump in the combined system is estimated from the experimental results. Copyright © 2001 John Wiley & Sons, Ltd.     

Nonlinear identification of a brushless excitation system via field tests

In this paper, nonlinear identification of the excitation system (EXS) in the gas unit #2 of Rajaee power plant in Iran is presented. Two methods of modeling, i.e., grey-box and black-box modeling are used and compared. In the grey-box (classical) approach, first a block-diagram for the EXS is suggested, then a test procedure for identification of its parameters is outlined. The input-output data corresponding to each block of the system is obtained through field tests. In this approach, the only nonlinearities considered in the block diagram are the limits. The other nonlinearities are reflected in the change of parameters in the linear transfer functions at different operating conditions. In the black-box approach, identification of the system is carried out using discrete wavelet transform. A variable structure wavelet was tried to cope with system changes at different operating conditions, but a wavelet with fixed number of scaling functions or wavelet functions proved to be quite adequate. The simulation results and their comparison, show the good accuracy of both derived models. Although the model obtained through the black-box approach shows a better fit when its output is compared with the measured variables, the model obtained through the grey-box approach reflects the physical properties of the system and may be more useful for power engineers.     

Application of catalytic membrane reactor for pure hydrogen production by flare gas recovery as a novel approach

In the present study, application of catalytic membrane reactor as a novel approach for the flare gas recovery is proposed. A comprehensive two-dimensional non-isothermal model has been constructed to evaluate the performance of flare gas recovery process in the membrane reactor. The model is developed by taking into accounts the main chemical kinetics, heat and mass transfer phenomena and hydrogen permeation in the radial direction across a Pd–Ag membrane. The model predictions are validated based on different experimental results reported in literature. The impact of reactor operating conditions on the recovery process such as temperature and pressure, feed molar ratio and sweep gas ratio are investigated and discussed. The modeling results confirm that the flare gas conversion and hydrogen recovery improves with increasing the operating temperature, pressure and sweep ratio as a consequence of increasing the driving force for H₂ permeation through membrane. The environmental consideration revealed that by application of catalytic membrane reactor for the flare gas recovery of Asalouyeh gas processing plant (Iran), not only the equivalent mass of greenhouse gases emission reduces from 2179 kg/s to 36 kg/s, but also, 12.7 kg/s pure hydrogen will be produced by flare gas recovery at 750 K, 5 bar, sweep ratio of 5 and feed molar ratio of 4.