Добірка наукової літератури з теми "High-temperature steam generator"

Research and development work on high-temperature and high-pressure (up to 1500°F TIT and 4500 psia) topping steam turbines and associated steam generators for steam power plants as well as combined cycle plants is being carried forward by DOE, EPRI, and independent companies. Aeroderivative gas turbines and heavy-duty gas turbines both will require exhaust gas supplementary firing to achieve high throttle temperatures. This paper presents an analysis and examples of a split stream boiler arrangement for high-temperature and high-pressure topping steam turbine combined cycles. A portion of the gas turbine exhaust flow is run in parallel with a conventional heat recovery steam generator (HRSG). This side stream is supplementary fired opposed to the current practice of full exhaust flow firing. Chemical fuel gas recuperation can be incorporated in the side stream as an option. A significant combined cycle efficiency gain of 2 to 4 percentage points can be realized using this split stream approach. Calculations and graphs show how the DOE goal of 60 percent combined cycle efficiency burning natural gas fuel can be exceeded. The boiler concept is equally applicable to the integrated coal gas fuel combined cycle (IGCC).

After a postulated design basis accident leads high temperature gas cooled reactor to emergency shutdown, steam generator still remains with high temperature level and needs to be cooled down by a precooling before reactor restarts with clearing of fault. For the large difference of coolant temperature between inlet and outlet of steam generator in normal operation, the temperature distribution on the components of steam generator is very complicated. Therefore, the temperature descending rate of the components in steam generator needs to be limited to avoid the potential damage during the precooling stage. In this paper, a pebble-bed high temperature gas cooled reactor is modeled by thermal-hydraulic system analysis code and several postulated precooling injection transients are simulated and compared to evaluate their effects, which will provide support for the precooling design. The analysis results show that enough precooling injection is necessary to satisfy the precooling requirements, and larger mass flow rate of precooling water injection will accelerate the precooling process. The temperature decrease of steam generator is related to the precooling injection scenarios, and the maximal mass flow rate of the precooling injection should be limited to avoid the excessively quick temperature change of the structures in steam generator.

A device which could produce high-temperature steam quickly was designed. The overall structure of the heating device and the heating pipe of key components were introduced mainly, and the working process of the heating device was analyzed and discussed. This high-temperature steam device with high heating efficiency, produces steam fast and could realize precise temperature control. This device could expand application research of polymer materials and composite materials and provide key guide parameters in the process of technical research.

After emergency shutdown of high-temperature-gas-cooled reactor, the residual heat of the reactor core should be removed. As the natural circulation process spends too long period of time to be utilized, an active residual heat removal procedure is needed, which makes use of steam generator and start-up loop. During this procedure, the structure of steam generator may suffer cold/heat shock because of the sudden load of coolant or hot helium at the first few minutes. Transient analysis was carried out based on a one-dimensional mathematical model for steam generator and steam pipe of start-up loop to achieve safety and reliability. The results show that steam generator should be discharged and precooled; otherwise, boiling will arise and introduce a cold shock to the boiling tubes and tube sheet when coolant began to circulate prior to the helium. Additionally, in avoiding heat shock caused by the sudden load of helium, the helium circulation should be restricted to start with an extreme low flow rate; meanwhile, the coolant of steam generator (water) should have flow rate as large as possible. Finally, a four-step procedure with precooling process of steam generator was recommended; sensitive study for the main parameters was conducted.

In nuclear power plant, fretting wear due to a combination of impact and sliding motions of the U-tubes against the supports and/or foreign objects caused by flow induced vibration, can make a serious problem in steam generator. A test rig, fretting wear simulator, is developed to elucidate fretting wear mechanism qualitatively and quantitatively. The realistic condition of steam generator of high temperature up to 320°C, high pressure up to 15 MPa, and water environment could be achieved by a test rig. The fretting wear simulator consists of main frame, water loop system, and control unit. Actual contact region under a realistic condition of steam generator was isolated using autoclave. Effects of various parameters such as the amounts of impact and sliding motions, applied loads and initial gaps and so forth are considered in this research. After the experiment, wear damage was measured by a three-dimensional profiler and the surface was also studied by SEM microscopically. Initial results were also presented.

In nuclear power plant, fretting wear caused by flow induced vibration (FIV) accompanied with impact force can make serious problems between U -tubes and egg-crates which are located in steam generators. In order to guarantee the reliability of the steam generator, design based on consideration of the damage due to the fretting wear of the U -tube is inevitable. The purpose of this study is to elucidate fretting wear mechanism qualitatively and quantitatively. First, finite element models are developed to analyze the dynamic characteristics and estimate the impact force in steam generators. Based on the numerical results, fretting wear simulation is performed according to the environment to which the actual steam generators in nuclear power plant are exposed. Initial experimental results are obtained for various experimental parameters and the effect of work rate and temperature on fretting wear is evaluated.

For future high temperature reactor projects, e. g., for electricity production or nuclear process heat applications, the steam generator is a crucial component. A typical design is a helical coil steam generator consisting of several tubes connected in parallel forming cylinders of different diameters. This type of steam generator was a significant component used at the thorium high temperature reactor. In the work presented the temperature profile is being analyzed by the nodal thermal hydraulics code TRACE for the thorium high temperature reactor steam generator. The influence of the nodalization is being investigated within the scope of this study and compared to experimental results from the past. The results of the standard TRACE code are compared to results using a modified Nusselt number for the primary side. The implemented heat transfer correlation was developed within the past German HTR program. This study shows that both TRACE versions are stable and provides a discussion of the nodalization requirements.

Магістерська дисертація складається зі вступу, трьох розділів, висновків. Загальний об’єм дисертації становить 101 сторінку, з них 88 сторінок основного тексту, 31 рисунок, 4 таблиці, список джерел з 37 найменувань. Актуальність теми. Розвиток ядерної енергетики в даний час направлено на створення АЕС на базі екологічно чистих реакторів 4-го покоління. Однією з можливих концепцій таких реакторів є модульний гелієвий реактор, в якому в якості теплоносія використовується гелій. В даний час розробляються перспективні проекти створення газоохолоджувальних ЯЕУ 4-го покоління, які поєднують в собі виробництво електроенергії та водню методом високотемпературного електролізу пари, що здійснюється в високотемпературних парогенераторах. Найбільший інтерес у питанні моделювання парогенератора ЯЕУ представляє собою течія киплячої рідини в вертикальному каналі довільної форми. Тому пошук максимально можливої компактності конструкції при достатньому рівні міцності та високих теплогідравлічних характеристиках є актуальною проблемою. Зв'язок роботи з науковими програмами, планами, темами. Науково-дослідна робота по темі дисертації проводилася по програмі спільних робіт з «Відділенням Цільової Підготовки «КПІ ім. Ігоря Сікорського» для НАНУ за напрямком №1.7.1.АХ.2 «Термогазодинаміка турбулентних потоків в обертових каналах високотемпературних енергетичних установок» від 02.01.2018 р., реєстраційний номер 0118Г000006. Мета даної роботи − дослідження теплогідравлічних та геометричних параметрів парогенератора ГТ-МГР для виробництва електроенергії та водню, а також моделювання процесу теплообміну при кипінні рідини в вертикальній трубі. Досягнення мети передбачає виконання таких завдань: – Розробити математичну модель високотемпературного парогенератора ЯЕУ четвертого покоління з використанням гелію в якості первинного теплоносія з гвинтовими закрученими (змієвиковими) трубами. – Змоделювати процес теплообміну при кипінні рідини. – Дослідити структуру потоку та характерні режими теплообміну в вертикальній трубі. – Реалізувати п'ять різних методів розрахунку теплообміну при кипінні у вертикальній трубі, заснованих на експериментальних кореляційних залежностях. Об’єктом дослідження є теплогідравлічні процеси в парогенераторі ядерної енергетичної установки ГТ-МГР з гелієвим реактором для виробництва електроенергії та водню. Предметом дослідження є закономірності та показники впливу на теплообмін і гідродинаміку від температури і тиску при кипінні рідини в теплообмінному елементі парогенератора. Методи дослідження: При досліджуванні використовувався метод математичного моделювання за допомогою спеціалізованої програми «STEAMG» для теплового та гідравлічного розрахунку парогенератора. Наукова новизна одержаних автором результатів полягає у наступному: 1. За допомогою спеціалізованої програми «STEAMG» було змодельовано процес теплообміну при кипінні рідини в вертикальній трубі. 2. Було визначено найбільш коректний з фізичної точки зору метод Чена для розрахунку теплообміну при русі двофазного потоку в каналі довільної форми. 3. Було отримано, що з ростом діаметра зовнішнього кожуха парогенератора в діапазоні D = 2,2…3,6 м відносні втрати тиску в холодному тракті парогенератора зростають на 7 % і знижуються зі збільшенням числа труб в трубному пучку на 11 %. 4. Відносні втрати тиску в гарячому тракті парогенератора невеликі і зменшуються з ростом діаметра зовнішнього кожуха і збільшенням числа труб в трубному пучку на 5 %. 5. З ростом діаметра зовнішнього кожуха парогенератора маса і об’єм теплопередавальних поверхонь парогенератора зростають на 10 % через зниження середньої швидкості первинного теплоносія, зниження значень коефіцієнта тепловіддачі і зростання потрібної довжини труб парогенератора. 6. В гарячому тракті значення коефіцієнта тепловіддачі при ηT = 0,925 на 15 % вище, ніж при ηT = 0,85. Практичне значення даної роботи полягає в отриманні початкових даних для створення компактних високотемпературних теплообмінників ядерної енергетичної установки з гелієвим реактором по виробництву електроенергії та водню. Апробація результатів роботи. Основні положення і результати роботи доповідались і обговорювались на конференції: – ХVІ Науково практична конференція студентів аспірантів та молодих вчених «Теоретичні і прикладні проблеми фізики, математики та інформатики.», м. Київ, 2018 р
The Master's thesis consists of an introduction, three chapters, and conclusions. The total volume of the thesis is 101 pages, including 88 pages of the basic text, 31 figures, 4 tables, a list of references of 37 titles. Importance of scientific problem. The development of nuclear energy is currently aimed at the creation of a nuclear power plant based on the 4th generation environmentally friendly reactors. One of the possible concepts for such reactors is a modular helium reactor, in which helium is used as a coolant. Currently promising projects for the creation of gas-cooled UES of the 4th generation are being developed, which combine the production of electricity and hydrogen by high-temperature steam electrolysis, which is carried out in high-temperature steam generators. The greatest interest in the modeling of the steam generator EIEU is the flow of boiling fluid in a vertical channel of arbitrary shape. Therefore, finding the maximum possible compactness of the structure with sufficient strength and high thermo-hydraulic characteristics is an urgent problem. Relationship to scientific programs, plans and themes. The research work on the topic of the dissertation was conducted on the program of joint work with the "Department of Target Preparation" KPI them. Igor Sikorsky for the National Academy of Sciences of Ukraine in the direction №.1.7.1.AX.2 "Thermogasodynamics of turbulent flows in the rotary canals of high-temperature power plants" dated January 2, 2018, registration number 0118Г000006. The aim of this work is to study the thermohydraulic and geometrical parameters of the GT-MGG steam generator for the production of electricity and hydrogen, as well as to simulate the process of heat exchange during boiling liquid in a vertical pipe. Achieving the goal involves performing the following tasks: - To develop a mathematical model of the high-temperature steam generator EIEA of the fourth generation using helium as a primary coolant with spiral twisted (snake) pipes. - Modify the process of heat exchange with boiling liquids. - Explore the flow structure and characteristic heat transfer modes in the vertical pipe. - Realize five different methods of calculating heat transfer when boiling in a vertical pipe, based on experimental correlation dependencies. The object of research is the thermal-hydraulic processes in the steam generator of the nuclear power plant GT-MGR with a helium reactor for the production of electricity and hydrogen. The subject of research is the patterns and indicators of the effect on heat transfer and hydrodynamics from temperature and pressure at boiling liquid in the heat-exchange element of the steam generator. Research methodology: In the study, the method of mathematical modeling was used with the help of a specialized program "STEAMG" for thermal and hydraulic calculation of the steam generator. The scientific novelty of the results obtained by the author is as follows: 1. With the use of the STEAMG specialized program, the process of heat exchange during boiling liquid in a vertical pipe was simulated. 2. It was determined that the most correct from the physical point of view is the Chen method for calculating heat transfer in the movement of two-phase flow in a channel of arbitrary form. 3. It was found that with increasing diameter of the outer casing of the steam generator in the range D = 2,2…3,6 m relative pressure losses in the cold tract of the steam generator increase by 7% and decrease with an increase in the number of pipes in the tube bundle by 11%. 4. Relative pressure losses in the hot path of the steam generator are small and diminish with the growth of the diameter of the outer casing and the increase in the number of pipes in the tube bundle by 5%. 5. With the growth of the diameter of the outer casing of the steam generator, the mass and volume of the heat transfer surfaces of the steam generator increase by 10% due to the decrease in the average speed of the primary coolant, the decrease in the values of the coefficient of heat transfer and the growth of the required length of steam of the steam generator. 6. In the hot path, the value of the coefficient of heat transfer at ηT = 0,925 is 15% higher than at ηT = 0,85. The importance for practice of this work is to obtain the initial data for the creation of compact high-temperature heat exchangers of a nuclear power plant with a helium reactor for the production of electricity and hydrogen. Conferences. The main provisions and results of work were reported and discussed at the conference: - XVI Scientific and Practical Conference of Students of Postgraduate Students and Young Scientists "Theoretical and Applied Problems of Physics, Mathematics and Informatics.", Kyiv, 2018

The Department of Energy and the Idaho National Laboratory are developing a Next Generation Nuclear Plant (NGNP) to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is two fold: 1) efficient low cost energy generation and 2) hydrogen production. Although a next generation plant could be developed as a single-purpose facility, early designs are expected to be dual-purpose. While hydrogen production and advanced energy cycles are still in their early stages of development, research towards coupling a high temperature reactor, electrical generation and hydrogen production is under way. Many aspects of the NGNP must be researched and developed to make recommendations on the final design of the plant. Parameters such as working conditions, cycle components, working fluids, and power conversion unit configurations must be understood. Three configurations of the power conversion unit were modeled using the process code HYSYS; a three-shaft design with 3 turbines and 4 compressors, a combined cycle with a Brayton top cycle and a Rankine bottoming cycle, and a reheated cycle with 3 stages of reheat were investigated. A high temperature steam electrolysis hydrogen production plant was coupled to the reactor and power conversion unit by means of an intermediate heat transport loop. Helium, CO2, and an 80% nitrogen, 20% helium mixture (by weight) were studied to determine the best working fluid in terms cycle efficiency and development cost. In each of these configurations the relative heat exchanger size and turbomachinery work were estimated for the different working fluids. Parametric studies away from the baseline values of the three-shaft and combined cycles were performed to determine the effect of varying conditions in the cycle. Recommendations on the optimal working fluid for each configuration were made. The helium working fluid produced the highest overall plant efficiency for the three-shaft and reheat cycle; however, the nitrogen-helium mixture produced similar efficiency with smaller component sizes. The CO2 working fluid is recommend in the combined cycle configuration.

An investigation into the performance of several combined gas-steam power generating plants’ cycles was undertaken at the School of Engineering and Technology at the University of Hertfordshire and it is predominantly analytical in nature. The investigation covered in principle the aspect of the fundamentals and the performance parameters of the following cycles: gas turbine, steam turbine, ammonia-water, partial oxidation and the absorption chiller. Complete thermal analysis of the individual cycles was undertaken initially. Subsequently, these were linked to generate a comprehensive computer model which was employed to predict the performance and characteristics of the optimized combination. The developed model was run using various input parameters to test the performance of the cycle’s combination with respect to the combined cycle’s efficiency, power output, specific fuel consumption and the temperature of the stack gases. In addition, the impact of the optimized cycles on the generation of CO2 and NOX was also investigated. This research goes over the thermal power stations of which most of the world electrical energy is currently generated by. Through which, to meet the increase in the electricity consumption and the environmental pollution associated with its production as well as the limitation of the natural hydrocarbon resources necessitated. By making use of the progressive increase of high temperature gases in recent decades, the advent of high temperature material and the use of large compression ratios and generating electricity from high temperature of gas turbine discharge, which is otherwise lost to the environment, a better electrical power is generated by such plant, which depends on a variety of influencing factors. This thesis deals with an investigation undertaken to optimize the performance of the combined Brayton-Rankine power cycles' performance. This work includes a comprehensive review of the previous work reported in the literature on the combined cycles is presented. An evaluation of the performance of combined cycle power plant and its enhancements is detailed to provide: A full understanding of the operational behaviour of the combined power plants, and demonstration of the relevance between power generations and environmental impact. A basic analytical model was constructed for the combined gas (Brayton) and the steam (Rankine) and used in a parametric study to reveal the optimization parameters, and its results were discussed. The role of the parameters of each cycle on the overall performance of the combined power cycle is revealed by assessing the effect of the operating parameters in each individual cycle on the performance of the CCPP. P impacts on the environment were assessed through changes in the fuel consumption and the temperature of stack gases. A comprehensive and detailed analytical model was created for the operation of hypothetical combined cycle power and power plant. Details of the operation of each component in the cycle was modelled and integrated in the overall all combined cycle/plant operation. The cycle/plant simulation and matching as well as the modelling results and their analysis were presented. Two advanced configurations of gas turbine cycle for the combined cycle power plants are selected, investigated, modelled and optimized as a part of combined cycle power plant. Both configurations work on fuel rich combustion, therefore, the combustor model for rich fuel atmosphere was established. Additionally, models were created for the other components of the turbine which work on the same gases. Another model was created for the components of two configurations of ammonia water mixture (kalina) cycle. As integrated to the combined cycle power plant, the optimization strategy considered for these configurations is for them to be powered by the exhaust gases from either the gas turbine or the gases leaving the Rankine boiler (HRSG). This included ChGT regarding its performance and its environmental characteristics. The previously considered combined configuration is integrated by as single and double effect configurations of an ammonia water absorption cooling system (AWACS) for compressor inlet air cooling. Both were investigated and designed for optimizing the triple combination power cycle described above. During this research, tens of functions were constructed using VBA to look up tables linked to either estimating fluids' thermodynamic properties, or to determine a number of parameters regarding the performance of several components. New and very interesting results were obtained, which show the impact of the input parameters of the individual cycles on the performance parameters of a certain combined plant’s cycle. The optimized parameters are of a great practical influence on the application and running condition of the real combined plants. Such influence manifested itself in higher rate of heat recovery, higher combined plant thermal efficiency from those of the individual plants, less harmful emission, better fuel economy and higher power output. Lastly, it could be claimed that various concluding remarks drawn from the current study could help to improve the understanding of the behaviour of the combined cycle and help power plant designers to reduce the time, effort and cost of prototyping.

Nearly all electrical power is generated by rotating a coil in a magnetic field. In most cases, the coil is turned by a steam turbine operating according to the Rankine cycle. Water is boiled and heated to make high-pressure steam, which drives the turbine. The thermal efficiency is about 30–35%, and is limited by the highest steam temperature tolerated by the turbine blades. Alternatively, a gas turbine operating according to the Brayton cycle can be used. Much higher turbine inlet temperatures are possible, and the thermal efficiency is higher, typically 40%. Combined cycle generation, in which the hot exhaust from a gas turbine drives a Rankine cycle, can achieve thermal efficiencies of almost 60%. Substitution of coal-fired by combined cycle natural gas power plants can result in significant reductions in CO2 emissions.

The Barents Sea is a region of the Arctic Ocean named after one of its first known explorers (1594–1597), Willem Barentsz from the Netherlands, although there are accounts of earlier explorations: the Norwegian seafarer Ottar rounded the northern tip of Europe and explored the Barents and White Seas between 870 and 890 ce, a journey followed by a number of Norsemen; Pomors hunted seals and walruses in the region; and Novgorodian merchants engaged in the fur trade. These seafarers were probably the first to accumulate knowledge about the nature of sea ice in the Barents region; however, scientific expeditions and the exploration of the climate of the region had to wait until the invention and employment of scientific instruments such as the thermometer and barometer. Most of the early exploration involved mapping the land and the sea ice and making geographical observations. There were also many unsuccessful attempts to use the Northeast Passage to reach the Bering Strait. The first scientific expeditions involved F. P. Litke (1821±1824), P. K. Pakhtusov (1834±1835), A. K. Tsivol’ka (1837±1839), and Henrik Mohn (1876–1878), who recorded oceanographic, ice, and meteorological conditions.The scientific study of the Barents region and its climate has been spearheaded by a number of campaigns. There were four generations of the International Polar Year (IPY): 1882–1883, 1932–1933, 1957–1958, and 2007–2008. A British polar campaign was launched in July 1945 with Antarctic operations administered by the Colonial Office, renamed as the Falkland Islands Dependencies Survey (FIDS); it included a scientific bureau by 1950. It was rebranded as the British Antarctic Survey (BAS) in 1962 (British Antarctic Survey History leaflet). While BAS had its initial emphasis on the Antarctic, it has also been involved in science projects in the Barents region. The most dedicated mission to the Arctic and the Barents region has been the Arctic Monitoring and Assessment Programme (AMAP), which has commissioned a series of reports on the Arctic climate: the Arctic Climate Impact Assessment (ACIA) report, the Snow Water Ice and Permafrost in the Arctic (SWIPA) report, and the Adaptive Actions in a Changing Arctic (AACA) report.The climate of the Barents Sea is strongly influenced by the warm waters from the Norwegian current bringing heat from the subtropical North Atlantic. The region is 10°C–15°C warmer than the average temperature on the same latitude, and a large part of the Barents Sea is open water even in winter. It is roughly bounded by the Svalbard archipelago, northern Fennoscandia, the Kanin Peninsula, Kolguyev Island, Novaya Zemlya, and Franz Josef Land, and is a shallow ocean basin which constrains physical processes such as currents and convection. To the west, the Greenland Sea forms a buffer region with some of the strongest temperature gradients on earth between Iceland and Greenland. The combination of a strong temperature gradient and westerlies influences air pressure, wind patterns, and storm tracks. The strong temperature contrast between sea ice and open water in the northern part sets the stage for polar lows, as well as heat and moisture exchange between ocean and atmosphere. Glaciers on the Arctic islands generate icebergs, which may drift in the Barents Sea subject to wind and ocean currents.The land encircling the Barents Sea includes regions with permafrost and tundra. Precipitation comes mainly from synoptic storms and weather fronts; it falls as snow in the winter and rain in the summer. The land area is snow-covered in winter, and rivers in the region drain the rainwater and meltwater into the Barents Sea. Pronounced natural variations in the seasonal weather statistics can be linked to variations in the polar jet stream and Rossby waves, which result in a clustering of storm activity, blocking high-pressure systems. The Barents region is subject to rapid climate change due to a “polar amplification,” and observations from Svalbard suggest that the past warming trend ranks among the strongest recorded on earth. The regional change is reinforced by a number of feedback effects, such as receding sea-ice cover and influx of mild moist air from the south.

SuperCritical Fluids (SCFs) have unique thermophyscial properties and heat-transfer characteristics, which make them very attractive for use in power industry. In this chapter, specifics of thermophysical properties and heat transfer of SCFs such as water, carbon dioxide and helium are considered and discussed. Also, particularities of heat transfer at SuperCritical Pressures (SCPs) are presented, and the most accurate heat-transfer correlations are listed. SuperCritical Water (SCW) is widely used as the working fluid in the SCP Rankine “steam”-turbine cycle in fossil-fuel thermal power plants. This increase in thermal efficiency is possible by application of high-temperature reactors and power cycles. Currently, six concepts of Generation-IV reactors are being developed, with coolant outlet temperatures of 500°C~1000°C. SCFs will be used as coolants (helium in GFRs and VHTRs; and SCW in SCWRs) and/or working fluids in power cycles (helium; mixture of nitrogen (80%) and helium [20%]; nitrogen, and carbon dioxide in Brayton gas-turbine cycles; and SCW “steam” in Rankine cycle).

Supercritical Fluids (SCFs) have unique thermophyscial properties and heat-transfer characteristics, which make them very attractive for use in power industry. In this chapter, specifics of thermophysical properties and heat transfer of SCFs such as water, carbon dioxide, and helium are considered and discussed. Also, particularities of heat transfer at Supercritical Pressures (SCPs) are presented, and the most accurate heat-transfer correlations are listed. Supercritical Water (SCW) is widely used as the working fluid in the SCP Rankine “steam”-turbine cycle in fossil-fuel thermal power plants. This increase in thermal efficiency is possible by application of high-temperature reactors and power cycles. Currently, six concepts of Generation-IV reactors are being developed, with coolant outlet temperatures of 500°C~1000°C. SCFs will be used as coolants (helium in GFRs and VHTRs, and SCW in SCWRs) and/or working fluids in power cycles (helium, mixture of nitrogen (80%) and helium (20%), nitrogen and carbon dioxide in Brayton gas-turbine cycles, and SCW/“steam” in Rankine cycle).

Direct stress and sub-stress caused by fire, temperature variation and external loading in a structure are most important for the development of cracks. The chemical reactions of natural healing in the matrix was not been established conclusively. The most significant factor that influences the self-healing is the precipitation of calcium carbonate crystals on the crack surface. The mechanism which contribute autogenic healing are: (a) Continued hydration of cement at cracked surface as well as continued hydration of already formed gel and also inter-crystallization of fractured crystals; (b) blocking of flow path by water impurities and concrete particles broken from the crack surface due to cracking; (c) expansion of concrete in the crack flank (swelling) and closing of cracks by spalling of loose concrete particle are also reported as the sealing mechanism by researchers. The recovery of mechanical as well as physical property was discussed by different researchers. An experimental investigation was carried out to study the autogenic healing of fire damaged fly ash and conventional cementitious mortar samples subjected to steam followed by water curing at normal atmospheric pressure. The micro cracks are generated artificially by heating the 28 days aged mortar samples at 800 Deg. C. The effect of fly-ash replacing ordinary Portland cement by 0 and 20% was studied. Recovery of compressive strength and physical properties i.e. apparent porosity, water absorption, ultrasonic pulse velocity and rapid chloride ion penetration test confirm the self-healing of micro cracks. Such healing is more prominent for fly ash mortar mix. Optical as well as scanning electron microscopy With EDAX analysis and X-ray diffraction study of the white crystalline material formed in the crack, confirms formation of calcium carbonate.

Ecological disturbances at Long-Term Ecological Research (LTER) sites are often the result of extreme meteorological events. Among the events of significance are tropical storms, including hurricanes, and extratropical cyclones. Extratropical storms are low-pressure systems of the middle and high latitudes with their attendant cold and warm fronts. These fronts are associated with strong, horizontal thermal gradients in surface temperatures, strong winds, and a vigorous jet stream aloft. These storms and their attendant fronts generate most of the annual precipitation in the continental United States and provide the lifting mechanisms for thunderstorms that, on occasion, spawn tornadoes. Off the United States West and East Coasts, extratropical storms generate winds, wind waves, wind tides, and long-shore currents that rework coastal sediments, alter landscape morphology, and change the regional patterns of coastal erosion and accretion (Dolan et al. 1988). Although extratropical storms do not match hurricanes in either precipitation intensity or in the strength of the winds generated, they are much larger in size and have a more extensive geographic impact. On occasion, extratropical storms will intensify at an extraordinary rate of 1 millibar (mb) per hour for 24 hours or more. Such storms are classed as “bomb” and are comparable to hurricanes. Extratropical storms occur in all months of the year but are most frequent and more intense in winter when the north-south temperature contrast is large and dynamic support for storm intensification from the stronger jet stream aloft is great. In this chapter, we will explore the history of storminess for those LTER sites in the continental United States at which more than a century of data on storms and their storm tracks are readily available. Specifically, we will look at the record of changes in storminess at both the regional and national scales. During the 1990s, significant storms along the U.S. West Coast and droughts and fires in Florida in an El Niño year led to a hypothesis that El Niño and La Niña conditions were associated with a modulation in the frequency of storms. In addition, it has been suggested that the frequency of El Niño and La Niña events and, by inference, storminess, has increased during the past century.

A control and operation method of a High Temperature Gas Cooled Reactor (HTGR) power plant with Steam Cycle has been investigated, and an adequacy of the method has been examined by plant dynamics analyses. In this plant, the steam cycle system with regenerative and reheat cycle is employed, where the heat generated in the reactor is transferred to the secondary coolant (water and steam) through the steam generator (SG), which has the steam turbine and generator, is installed in the secondary system. The reactor and steam cycle system control methods were evaluated. Analytical results through system modeling concluded that the reactor power changes could be effectively achieved by utilizing primary system helium flow rate control, and overall plant system responsiveness and control could be achieved by employing feed water flow control system and turbine governor control system. The plant dynamics analysis code ASURA, which was developed by MHI, can simulate the major components and systems of this plant. It was used for this examination. In order to adequate of the control and operation method, some cases of plant dynamics analysis by ASURA was conducted in this study.

Research and Development work on high temperature and high pressure (up to 1500 °F TIT and 4500 psia)1 topping steam turbines and associated steam generators for steam power plants as well as combined cycle plants is being carried forward by DOE, EPRI and independent companies. Aero Derivative gas turbines and Heavy Duty gas turbines both will require exhaust gas supplementary firing to achieve high throttle temperatures. This paper presents an analysis and examples of a split stream boiler arrangement for high temperature and high pressure topping steam turbine combined cycles. A portion of the gas turbine exhaust flow is run in parallel with a conventional heat recovery steam generator (HRSG). This side stream is supplementary fired opposed to current practice of full exhaust flow firing. Chemical fuel gas recuperation can be incorporated in the side stream as an option. A significant combined cycle efficiency gain of 2 to 4 percentage points can be realized using this split stream approach. Calculations and graphs show how the DOE goal of 60 % combined cycle efficiency burning natural gas fuel can be exceeded. The boiler concept is equally applicable to the integrated coal gas fuel combined cycle (IGCC).

After a supposed accident lead the reactor to shutdown, the residual heat generated from the decay will be removed out by the cooling system. A cooling water flow will be pumped into the steam generator for cooling the reactor after the pressure of the secondary side of the steam generator is decreased to a lower design value with opening of the pressure relief valve which is installed on the live-steam pipeline. But the temperature of the heat-exchange tubes and the tube plate at the outlet of the steam generator whose temperature in the steady-state operation is 570° high, need to be cooled down to about 200° for the material limitation before the cooling water is injected, to avoid the cold-shock damage on the components. In this paper, exampled as the 200MWe high temperature gas cooled reactor (HTR-PM), a general thermal-hydraulic system analysis code is used for modeling and simulating numerically the pressure relief transient after the accident. The results show the structure components of the steam generator will be cooled down effectively to mitigate the cold-shock damage from the cooling water during the transient with the designed pressure value of 1MPa where the pressure relief valve in 30mm diameter will be closed. It provides supports for the evaluation on the feasibility of cooling water injection and also for the material stress analysis on some relevant components in the steam generator design.

In Germany two HTR nuclear power plants had been built and operated, the AVR-15 and the THTR-300. Also various projects for different purposes in a large power range had been developed. The AVR-15, an experimental reactor with a power output of 15 MWel was operated for more than 20 years with excellent results. The THTR-300 was designed as a prototype demonstration plant with 300 MWel and should be the technological basis for the entire future reactor line. The THTR-300 was prematurely shut down and decommissioned because of political reasons. But because of the accompanying comprehensive R&D program and the operation time of about 5 years, the technology was proved and essential operational results were gained. The AVR steam generator was installed above the reactor core. The six THTR heat exchangers were arranged circularly around the reactor core. Both heat exchanger systems have been operated successfully and furthermore acted as a residual heat removal system. The technology knowledge and experience gained on these existing HTR plants is still available at Westinghouse Electric Germany GmbH since Westinghouse is one of the legal successors of the former German HTR companies. As a follow-up project of THTR, the HTR-500 was developed and designed up to the manufacturing stage. For this plant additionally to the 8 steam generators, two residual heat removal heat exchangers were foreseen. These were to be installed in a ring around the reactor core. All these HTRs were designed for the generation of electricity using a steam cycle. Extensive research work has also been done for advanced applications of HTR technology e.g. using a direct cycle within the HHT project or generating process heat within the framework of the PNP project. Because of the critical attitude of the German government to the nuclear power in the past 20 years in Germany there was only a very limited interest in the further development of the HTR technology. As a consequence of the German decision, at the beginning of the 90s, to phase out nuclear power completely, research and funding of further development of HTR reactor design was also cut down. Today’s HTR reactor designs, such as the PBMR in South Africa, use a direct cycle with a gas turbine. This technology is also based on the THTR technology and PBMR is a licensed party. For the HTR-PM in China and the future oil sand projects powered by HTR’s in Canada and Siberia however the use of steam generators is required. Westinghouse and Dresden University cooperate in the field of steam generator technology for HTR reactors. The existing know-how for HTR is based on a huge pool of knowledge gained by the past German HTR projects mentioned above and consists especially of the design methodology, the mechanical layout and material issues for helium heated steam generators. The project team consists of experienced specialists who have worked on HTR projects in the past and of young graduate engineers. Main goal of the project is to analyze the existing know-how and to adjust it to the state of the art. As a first step, the existing design and its methodology is being analyzed and the different points of improvement are identified. The final step of the program is the description of a new methodology which fulfills the severe requirements of the customer and all of the actual licensing conditions. One of the reasons why this project has been launched is that the requirements of life expectancy for HTR components increase and the material limits will be reached, especially at high temperatures. This implies that the design of helix heat exchangers has to allow inservice inspections; this was not a requirement for the previous THTR design. Methodologies for in-service inspections already had been developed, but they are not sufficient for today’s tube lengths and have to be adapted. Another example, based on operating experience, is using reheaters to increase the efficiency is not recommended today. Using supercritical steam conditions to increase the efficiency should be investigated instead. In general, the economic benefit has to be balanced against the additional costs resulting from better material and more complex manufacturing.

Traditionally nuclear reactor power plants have been optimized for electrical power generation only. In the light of the ever-rising cost of ever-dwindling fossil fuel resources as well the global polluting effects and consequences of their usage, the use of nuclear energy for process heating is becoming increasingly attractive. In this study the use of a so-called cogeneration plant in which a nuclear reactor energy source is simulated using basic equations for the simultaneous production of superheated steam for electrical power generation and process heat, is considered and analyzed. A novel heat pipe heat exchanger is used to generate superheated steam for the process heat which is, in this case, a coal-to-liquid process (CTL). Natural circulation of sodium, via a thermo-syphon, is used in the heat pipe heat exchanger to transfer heat from the hot stream to the cold. The superheated steam for power generation is generated in a separate once-through helical coil steam generator. A 750 °C, 7 MPa helium cooled high-temperature modular reactor (HTMR) has been considered to simultaneously provide steam at 540 °C, 13.5 MPa for the power unit and steam at 430 °C, 4 MPa for a CTL production plant. The simulation and dynamic control of such a cogeneration plant is considered. In particular, a theoretical model of the plant will be simulated with the aim of predicting the transient and dynamic behavior of the HTMR in order to provide guideline for the control of the plant under various operating conditions. It was found that the simulation model captured the behavior of the plant reasonably well and it is recommended that it could be used in the detailed design of plant control strategies. It was also found that using a 1500 MW-thermal HTMR the South African contribution to global pollution can be reduced by 1.58%.

The paper deals with the issue of increasing efficiency of nuclear power plants with the modular high-temperature helium reactor (HTGR) and direct gas turbine cycle. It should be noted that only this combination can highlight the advantages of the HTGR, namely the ability to heat helium to about 1000°C, in comparison with other reactor plants for electricity generation. The HTGR has never been used in the direct gas turbine cycle. At present, several designs of such commercial plants are at the stage of experimental validation of main technical features. In Russia, “OKB Mechanical Engineering” together with “General Atomics” (USA) are developing the GT-MHR project with the reactor power of 600 MW, reactor outlet helium temperature of 850 °C, and efficiency of about 45.2%; the South African Republic is developing the PBMR project with the reactor power of 400 MW, reactor outlet helium temperature of 900 °C, and efficiency of about 42%; and Japan is developing the GTHTR-300 project with the reactor power of 600 MW, reactor outlet helium temperature of 850°C, and efficiency of about 45.6%. As it has been proven by technical and economic estimations, one of the most important factors for successful promotion of reactor designs is their net efficiency, which must be not lower than 47%. A significant advantage of a reactor plant with the HTGR and gas-turbine power conversion unit over the steam cycle is considerable simplification of the power unit layout and reduction of the required equipment and systems (no steam generators, no turbine hall including steam lines, condenser, deaerator, etc.), which makes the gas-turbine power conversion unit more compact and less costly in production, operation and maintenance. However, in spite of this advantage, it seems that in the projects currently being developed, the potential of the gas-turbine cycle and high-temperature reactor to more efficiently generate electricity is not fully used. For example, in modern reactor plants with highly recuperative steam cycle with supercritical heat parameters, the net efficiency of electricity generation reaches 50–55%. There are three methods of Brayton cycle carnotization: regeneration, helium cooldown during compression, and heat supply during expansion. These methods can be used both separately and in combination, which gives a total of seven complex heat flow diagrams. Besides, there are ways to increase helium temperature at the reactor inlet and outlet, to reduce hydraulic losses in the helium path, to increase the turbomachine (TM) rotation speed in order to improve the turbine and compressor efficiency, to reduce helium leaks in the circulation path, etc. The analysis of GT-MHR, PBMR and GTHTR-300 development experience allows identification of the main ways of increasing the efficiency by selecting optimal parameters and design solutions for the reactor and power conversion unit. The paper estimates the probability of reaching the maximum electricity generation efficiency in reactor plants with the HTGR and gas turbine cycle with account of the up-to-date development status of major reactor plant components (reactor, vessels, turbocompressor (TC), generator, heat exchange equipment, and structural materials).

Digital Speckle Photogrammetry (DSP) is proving to be a very useful technique for studying, in the laboratory, the distribution of strain about cracks and other defects in stressed specimens. This non-contact technique is able to resolve strain gradients over a small physical area, for example across a weld heat affected zone. The technique has good potential for use as a condition monitoring tool for a variety of components in electrical power stations. In addition this measurement technique could also be applied to monitor the integrity of critical components of newer generation plant, such as wind turbine generator blades. There are, however, many installation problems to be overcome. For example, there is the need to have regard for the hostile environment in steam generating plant and the demanding conditions to which wind turbine blades are subjected. Ideally the outputs from individual DSP sensors would be used for continuous remote monitoring. However, DSP measurements can also be useful each time the plant is shut down during a plant outage; which would be used to complement data from existing proven rugged monitoring methods. This paper describes ongoing work to develop a ruggedised digital speckle ‘sensor’ and associated image capture system.

Abstract The primary coolant loop of the high temperature gas-cooled reactor contains trace impurities that could cause some corrosion to the materials. When the HTGR operates at a very high temperature, the impurities in the coolant have significant influence on the properties of the alloys used in steam generators. Corrosion tests were conducted on the Inconel 800H, Inconel 617 and Hastelloy X, and the alloys are commonly used in the steam generator of HTGR. They were corroded for up to 48 hours at 950 °C in a given helium atmosphere with trace impurities, and the corrosion results were observed. The SEM with EDX system was utilized for the metallographic examination and surface oxide composition analysis. The AES was used to verify the EDS analysis results. Due to severe internal oxidation and surface carbon transfer, Inconel 800H has the worst corrosion resistance, but Hastelloy X with the dense oxide layer has the best corrosion resistance. For Inconel617, the Cr element depletion occurs near the corrosion layer, which is very consistent with the theory. Since a certain amount of manganese in Hastelloy X may contribute to the formation of a dense oxide layer, thus an appropriate increase of the manganese content may enhance the alloy’s corrosion resistance.

A quasi-static model of a helical coiled Once-Through Steam Generator of High Temperature gas-cooled Reactor-Pebble Bed Module (HTR-PM) is developed based on the fundamental conservation of fluid mass, energy and momentum. The steam generator is handled with single tube concept and is divided into three regions as subcooled region, boiling region and superheated region. The equations are solved by Rung-Kutta method. The steady-state simulation results agree well with the design data. Furthermore, the results are compared with the results gotten from THERMIX/BLAST program, and the difference between them is small which shows the model and the methodology are reasonable.

A steam generator of PWR plant has moisture separators with function to separate water from two-phase flow of water and steam. Recently, corresponding to the request for power uprating of current and/or future plants with large thermal capacity, development of high performance moisture separator, which can deal with the increasing steam flow rate, has been required. Therefore, MHI has developed the moisture separator with high performance (J Model) by conducting a verification test under actual plant operating conditions (high pressure and high temperature). The developed separator’s main features are: swirl vane hub with a small diameter, horizontal slits at riser barrel, and slots with lips at the downcomer barrel. Based on the combination of the high pressure test results and thermal hydraulic analyses, value of moisture carry over (MCO) at SG outlet was evaluated. The evaluation resulted in the MCO value of less than 0.01% (our target value: 0.1%).