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    Sanjeev GUPTA, Martin FREITAG, Gerhard POSS

    In the defense-in-depth concept employed for the safety of nuclear installations, maintaining integrity of containment as the last barrier is of high importance to limit the release of radioactivity to the environment in case of a severe accident. The active and passive safety systems implemented in containments of light water reactors (LWRs) are designed to limit the consequences of such accidents. Assessing the performance and reliability of such systems under accident conditions is critical to the safety of nuclear installations.

    In the aftermath of the Fukushima accident, there has been focus on re-examining the existing safety systems to demonstrate their capabilities for a broader range of boundary conditions comprising both the early as well as the late phases of an accident. In addition to the performance testing of safety systems, their interaction with containment atmosphere needs detailed investigations to evaluate the effects of operation of safety systems on H2 risk and fission product (FP) behavior in containment, which may ultimately have an impact on the source term to the environment.

    In this context, an extensive containment safety related experimental research has been conducted in a thermal-hydraulics, hydrogen, aerosols, and iodine test facility (THAI, 60 m3, single vessel)/(THAI+, 80 m3, two interconnected vessels). Related to the subject of this paper, experimental investigations covered performance testing of various safety and mitigation systems, i.e., containment spray, passive autocatalytic recombiner (PAR), pressure suppression pool (water pools), and effects of their operation on H2 risk and in-containment FP behavior. The experimental results have provided a better phenomenological understanding and database for validation and further improvement of a safety analysis tool based on computation fluid dynamic (CFD) and lumped parameter (LP) modeling approach. This paper summarizes the main insights obtained from the aforesaid THAI experimental research covering safety systems installed in containments of LWRs. The relevance of experimental outcomes for reactor safety purpose is also discussed.

    Xu CHENG
    Puzhe LAN, Dong HAN, Ruimin ZHANG, Xiaoyuan XU, Zheng YAN

    With the continuous development of the spot market, in the multi-stage power market environment with the day-ahead market and right market, the study associated with the portfolio of energy storage devices requires that attention should be paid to transmission congestion and power congestion. To maximize the profit of energy storage and avoid the imbalance of power supply and consumption and the risk of node price fluctuation caused by transmission congestion, this paper presents a portfolio strategy of energy storage devices with financial/physical contracts. First, the concepts of financial/physical transmission rights and financial/physical storage rights are proposed. Then, the portfolio models of financial contract and physical contract are established with the conditional value-at-risk to measure the risks. Finally, the portfolio models are verified through the test data of the Pennsylvania-New Jersey-Maryland (PJM) electric power spot market, and the comparison between the risk aversion of portfolios based on financial/physical contract with the portfolio of the market without rights. The simulation results show that the portfolio models proposed in this paper can effectively avoid the risk of market price fluctuations.

    Xiaojun XUE, Yuting WANG, Heng CHEN, Gang XU

    A promising scheme for coal-fired power plants in which biomass co-firing and carbon dioxide capture technologies are adopted and the low-temperature waste heat from the CO2 capture process is recycled to heat the condensed water to achieve zero carbon emission is proposed in this paper. Based on a 660 MW supercritical coal-fired power plant, the thermal performance, emission performance, and economic performance of the proposed scheme are evaluated. In addition, a sensitivity analysis is conducted to show the effects of several key parameters on the performance of the proposed system. The results show that when the biomass mass mixing ratio is 15.40% and the CO2 capture rate is 90%, the CO2 emission of the coal-fired power plant can reach zero, indicating that the technical route proposed in this paper can indeed achieve zero carbon emission in coal-fired power plants. The net thermal efficiency decreases by 10.31%, due to the huge energy consumption of the CO2 capture unit. Besides, the cost of electricity (COE) and the cost of CO2 avoided (COA) of the proposed system are 80.37 $/MWh and 41.63 $/tCO2, respectively. The sensitivity analysis demonstrates that with the energy consumption of the reboiler decreasing from 3.22 GJ/tCO2 to 2.40 GJ/ tCO2, the efficiency penalty is reduced to 8.67%. This paper may provide reference for promoting the early realization of carbon neutrality in the power generation industry.

    Geyuan YIN, Chaojun WANG, Meng ZHOU, Yajie ZHOU, Erjiang HU, Zuohua HUANG

    The laminar flame speeds of ammonia mixed with syngas at a high pressure, temperature, and different syngas ratios were measured. The data obtained were fitted at different pressures, temperatures, syngas ratios, and equivalence ratios. Four kinetic models (the Glarborg model, Shrestha model, Mei model, and Han model) were compared and validated with experimental data. Pathway, sensitivity and radical pool analysis are conducted to find out the deep kinetic insight on ammonia oxidation and NO formation. The pathway analysis shows that H abstraction reactions and NHi combination reactions play important roles in ammonia oxidation. NO formation is closely related to H, OH, the O radical produced, and formation reactions. NO is mainly formed from reaction, HNO+ H= NO+ H2. Furthermore, both ammonia oxidation and NO formation are sensitive to small radical reactions and ammonia related reactions.

    Yue FU, Yongliang ZHAO, Ming LIU, Jinshi WANG, Junjie YAN

    Cold-end systems are heat sinks of thermal power cycles, which have an essential effect on the overall performance of thermal power plants. To enhance the efficiency of thermal power plants, multi-pressure condensers have been applied in some large-capacity thermal power plants. However, little attention has been paid to the optimization of the cold-end system with multi-pressure condensers which have multiple parameters to be identified. Therefore, the design optimization methods of cold-end systems with single- and multi-pressure condensers are developed based on the entropy generation rate, and the genetic algorithm (GA) is used to optimize multiple parameters. Multiple parameters, including heat transfer area of multi-pressure condensers, steam distribution in condensers, and cooling water mass flow rate, are optimized while considering detailed entropy generation rate of the cold-end systems. The results show that the entropy generation rate of the multi-pressure cold-end system is less than that of the single-pressure cold-end system when the total condenser area is constant. Moreover, the economic performance can be improved with the adoption of the multi-pressure cold-end system. When compared with the single-pressure cold-end system, the excess revenues gained by using dual- and quadruple-pressure cold-end systems are 575 and 580 k$/a, respectively.

    Tongbin ZHAO, Zhe REN, Kai YANG, Tao SUN, Lei SHI, Zhen HUANG, Dong HAN

    The combustion characteristics and emission behaviors of RP-3 jet fuel were studied and compared to commercial diesel fuel in a single-cylinder compression ignition (CI) engine. Engine operational parameters, including engine load (0.6, 0.7, and 0.8 MPa indicating the mean effective pressure (IMEP)), the exhaust gas recirculation (EGR) rate (0%, 10%, 20%, and 30%), and the fuel injection timing (−20, −15, −10, and −5 ° crank angle (CA) after top dead center (ATDC)) were adjusted to evaluate the engine performances of RP-3 jet fuel under changed operation conditions. In comparison to diesel fuel, RP-3 jet fuel shows a retarded heat release and lagged combustion phase, which is more obvious under heavy EGR rate conditions. In addition, the higher premixed combustion fraction of RP-3 jet fuel leads to a higher first-stage heat release peak than diesel fuel under all testing conditions. As a result, RP-3 jet fuel features a longer ignition delay (ID) time, a shorter combustion duration (CD), and an earlier CA50 than diesel fuel. The experimental results manifest that RP-3 jet fuel has a slightly lower indicated thermal efficiency (ITE) compared to diesel fuel, but the ITE difference becomes less noticeable under large EGR rate conditions. Compared with diesel fuel, the nitrogen oxides (NOx) emissions of RP-3 jet fuel are higher while its soot emissions are lower. The NOx emissions of RP-3 can be effectively reduced with the increased EGR rate and delayed injection timing.

    Jing SUN, Guanqun YU, Kui AN, Wenlong WANG, Biao WANG, Zhenyu JIANG, Chenggong SUN, Yanpeng MAO, Xiqiang ZHAO, Zhanlong SONG

    Diverse interactions between microwaves and irradiated media provide a solid foundation for identifying novel organization pathways for energy flow. In this study, a high-energy-site phenomenon and targeted-energy transition mechanism were identified in a particular microwave heating (MH) process. Intense discharges were observed when microwaves were imposed on irregularly sized SiC particles, producing tremendous heat that was 8-fold the amount generated in the discharge-free case. Energy efficiency was thereby greatly improved in the electricity-microwaves-effective heat transition. Meanwhile, the dispersed microwave field energy concentrated in small sites, where local temperatures could reach 2000°C–4000°C, with the energy density reaching up to 4.0 × 105 W/kg. This can be called a high-energy site phenomenon which could induce further processes or reactions enhancement by coupling effects of heat, light, and plasma. The whole process, including microwave energy concentration and intense site-energy release, shapes a targeted-energy transition mechanism that can be optimized in a controlled manner through morphology design. In particular, the discharge intensity, frequency, and high-energy sites were strengthened through the fabrication of sharp nano/microstructures, conferring twice the energy efficiency of untreated metal wires. The microwave-induced high-energy sites and targeted energy transition provide an important pathway for high-efficiency energy deployment and may lead to promising applications.

    Jialiang CHEN, Xiaoyuan XU, Zheng YAN, Han WANG

    This paper proposes a data-driven topology identification method for distribution systems with distributed energy resources (DERs). First, a neural network is trained to depict the relationship between nodal power injections and voltage magnitude measurements, and then it is used to generate synthetic measurements under independent nodal power injections, thus eliminating the influence of correlated nodal power injections on topology identification. Second, a maximal information coefficient-based maximum spanning tree algorithm is developed to obtain the network topology by evaluating the dependence among the synthetic measurements. The proposed method is tested on different distribution networks and the simulation results are compared with those of other methods to validate the effectiveness of the proposed method.

    Xin LYU, Qingping LI, Yang GE, Min OUYANG, Hexing LIU, Qiang FU, Junlong ZHU, Shouwei ZHOU

    Marine natural gas hydrate has recently attracted global attention as a potential new clean energy source. Laboratory measurements of various physical properties of gas hydrate-bearing marine sediments can provide valuable information for developing efficient and safe extraction technology of natural gas hydrates. This study presents comprehensive measurement results and analysis of drilled hydrate-bearing sediments samples recovered from Qiongdongnan Basin in the South China Sea. The results show that the gas hydrate in the core samples is mainly methane hydrate with a methane content of approximately 95%, and the other components are ethane and carbon dioxide. The saturation of the samples fluctuates from 2%–60%, the porosity is approximately 38%–43%, and the water content is approximately 30%–50%, which indicate that high water saturation means that timely drainage should be paid attention to during hydrate extraction. In addition, the median diameter of the sediment samples is mainly distributed in the range of 15 to 34 μm, and attention should be paid to the prevention and control of sand production in the mining process. Moreover, the thermal conductivity is distributed in the range of 0.75 to 0.96 W/(m∙K) as measured by the flat plate heat source method. The relatively low thermal conductivity of hydrates at this study site indicates that a combined approach is encouraged for natural gas production technologies. It is also found that clay flakes and fine particles are attached to the surface of large particles in large numbers. Such characteristics will lead to insufficient permeability during the production process.