Theoretical development of a thermal model for the reheater of a power plant boiler

Energy Technology Data Exchange (ETDEWEB)

Prieto, M.M. [Oviedo University, Energy Department, Campus de Viesques, 33204 GIJON. Asturias (Spain)]. E-mail: manuelap@uniovi.es; Suarez, I. [Oviedo University, Energy Department, Campus de Viesques, 33204 GIJON. Asturias (Spain); Fernandez, F.J. [Oviedo University, Energy Department, Campus de Viesques, 33204 GIJON. Asturias (Spain); Sanchez, H. [Central Termica de Soto de Ribera, Ribera de Arriba, Asturias (Spain); Mateos, M. [Central Termica de Soto de Ribera, Ribera de Arriba, Asturias (Spain)

2007-02-15

A three-dimensional numerical model for simulating flow and heat transfer in the reheater of a boiler is presented. The aim is to describe, as well as possible, the geometry of the reheater and to be able to perform different mass flows of steam along each of the tube serpentines. The model thus makes it possible to calculate the temperature of the tube surfaces along the reheater. The porosity concept is employed, along with empirical correlations for the convective heat transfer coefficient and the radiation heat transfer coefficients. The radiation equations consider most of the radiative effects of the gas: ash content, triatomic gases, type of fuel and temperatures, tube layout and distances and temperatures of other radiative surfaces. The model is proposed with a view to using the measured values of velocities, temperatures and gas composition in the reheater as boundary conditions. The equations are solved using a general purpose computational fluid dynamics (CFD) code in conjunction with specific calculations for the source terms.

Oxidation of zircaloy-2 in high temperature steam

International Nuclear Information System (INIS)

Ikeda, Seiichi; Ito, Goro; Ohashi, Shigeo

1975-01-01

Oxidation tests were conducted for zircaloy-2 in steam at temperature ranging from 900 to 1300 0 C to clarify its oxidation kinetics as a nuclear fuel cladding materials in case of a loss-of-coolant accident. The influence of maximum temperature and heating rate of the specimen on its oxidation rate in steam was investigated. The changes in mechanical properties of the specimens after oxidation tests are also studied. The results obtained were summarized as follows: (1) The weight of the specimen after oxidation in steam increased two times as the time required to reach the maximum temperature increased from 1 to 10 mins. (2) The kinetics of oxidation of zircaloy-2 in steam were not affected by the difference in the surface condition before test such as chemical polishing or pre-oxidation in steam. (3) The dominant growth of oxide film on the surface of zircaloy-2 was observed at the initial stage of oxidation in steam. However, the thickness of oxygen-rich solid solution layer under the film increased gradually with the progress of oxidation and the ratio of oxygen in oxide to that in solid solution has a constant value of 8:2. (4) The breakaway took place only in the specimen subjected to 900 0 C repeated heating. This penomenon was caused by the local growth of the oxide below a crack of the oxide film resulting from the reheating of the specimen. (5) The results of bending tests showed that the deflection until fracture of the specimen was smaller for the one heated at a higher temperature even if the weight increase was of the same order of magnitude for both specimens. (6) It was concluded that the ductility of zircaloy-2 decreased remarkably at a heating temperature in excess of 1100 0 C for more than 5 min. (auth.)

Steam turbines for the future

International Nuclear Information System (INIS)

Trassl, W.

1988-01-01

Approximately 75% of the electrical energy produced in the world is generated in power plants with steam turbines (fossil and nuclear). Although gas turbines are increasingly applied in combined cycle power plants, not much will change in this matter in the future. As far as the steam parameters and the maximum unit output are concerned, a certain consolidation was noted during the past decades. The standard of development and mathematical penetration of the various steam turbine components is very high today and is applied in the entire field: For saturated steam turbines in nuclear power plants and for steam turbines without reheat, with reheat and with double reheat in fossil-fired power plants and for steam turbines with and without reheat in combined cycle power plants. (orig.) [de

CFD analysis of temperature imbalance in superheater/reheater region of tangentially coal-fired boiler

Science.gov (United States)

Zainudin, A. F.; Hasini, H.; Fadhil, S. S. A.

2017-10-01

This paper presents a CFD analysis of the flow, velocity and temperature distribution in a 700 MW tangentially coal-fired boiler operating in Malaysia. The main objective of the analysis is to gain insights on the occurrences in the boiler so as to understand the inherent steam temperature imbalance problem. The results show that the root cause of the problem comes from the residual swirl in the horizontal pass. The deflection of the residual swirl due to the sudden reduction and expansion of the flow cross-sectional area causes velocity deviation between the left and right side of the boiler. This consequently results in flue gas temperature imbalance which has often caused tube leaks in the superheater/reheater region. Therefore, eliminating the residual swirl or restraining it from being diverted might help to alleviate the problem.

Numerical analysis method for reheater performance of moisture separator reheater for Nuclear Power Plants

International Nuclear Information System (INIS)

Oda, Tsuyoshi; Fujisawa, Kyosuke; Akamatsu, Hiroshi

2014-01-01

Nuclear power generation uses saturated steam of 6 MPa and 275degC level due to the restrictions imposed by the materials used in the nuclear reactor, and its efficiency, approximately 33-35%, is not high compared with fossil fuel power generation. Therefore, thermal engineers working on nuclear power generation have the important responsibility toward society of achieving the highest efficiency under the given restrictions. The use of a moisture separator reheater (MSR) is one of the measures we can take to achieve higher efficiency. Because the bottom of the MSR tube bundle making contact with the cycle steam at its lowest temperature is subcooled and inadequate drainage of the condensate inside the tubes causes cyclic flooding and temperature oscillations in some cases, it is necessary to have a minimum flow rate of excess heating steam slightly beyond the demand of/what is required for the heat transfer, and the consequent subcooling must be kept below a certain level. This report describes the numerical analysis method developed for the design of heat transfer performance and evaluation of the tube bundle integrity of MSRs. (author)

Thermodynamic and economic analysis of a partially-underground tower-type boiler design for advanced double reheat power plants

International Nuclear Information System (INIS)

Xu, Gang; Xu, Cheng; Yang, Yongping; Fang, Yaxiong; Zhou, Luyao; Yang, Zhiping

2015-01-01

An increasing number of tower-type boilers have been selected for advanced double reheat power plants, due to the uniform flue gas profile and the smooth steam temperature increase. The tall height and long steam pipelines lengths will however, result in dramatic increases in the difficulty of construction, as well as increased power plant investment cost. Given these factors, a novel partially-underground tower-type boiler design has been proposed in this study, which has nearly half of the boiler embedded underground, thereby significantly reducing the boiler height and steam pipeline lengths. Thermodynamic and economic analyses were quantitatively conducted on a 1000 MW advanced double reheat steam cycle. Results showed that compared to the reference power plant, the power plant with the proposed tower-type boiler design could reduce the net heat rate by 18.3 kJ/kWh and could reduce the cost of electricity (COE) by $0.60/MWh. The study also investigated the effects of price fluctuations on the cost-effectiveness of the reference power plant, for both the conventional and the proposed tower-type boilers designs, and found that the double reheat power plant with the proposed tower-type boiler design would be even more competitive and price-effective when the coal price and the investment costs increase. The research of this paper may provide a promising tower-type boiler design for advanced double reheat power plants with lower construction complexity and better cost-effectiveness. - Highlights: • A partially-underground tower-type boiler in double reheat power plants is proposed. for double reheat power plants is proposed. • Thermodynamic and economic analyses are quantitatively conducted. • Better energetic efficiency and greater economic benefits are achieved. • The impacts of price fluctuations on the economic feasibility are discussed

Dual turbine power plant and method of operating such plant, especially one having an HTGR steam supply

International Nuclear Information System (INIS)

Braytenbah, A.S.; Jaegtnes, K.O.

1977-01-01

A power plant including dual steam turbine-generators connected to pass superheat and reheat steam from a steam generator which derives heat from the coolant gas of a high temperature gas-cooled nuclear reactor is described. Associated with each turbine is a bypass line to conduct superheat steam in parallel with a high pressure turbine portion, and a bypass line to conduct superheat steam in parallel with a lower pressure turbine portion. Auxiliary steam turbines pass a portion of the steam flow to the reheater of the steam generator and drive gas blowers which circulate the coolant gas through the reactor and the steam source. Apparatus and method are disclosed for loading or unloading a turbine-generator while the other produces a steady power output. During such loading or unloading, the steam flows through the turbine portions are coordinated with the steam flows through the bypass lines for protection of the steam generator, and the pressure of reheated steam is regulated for improved performance of the gas blowers. 33 claims, 5 figures

Steam turbine installations

International Nuclear Information System (INIS)

Bainbridge, A.

1976-01-01

The object of the arrangement described is to enable raising steam for driving steam turbines in a way suited to operating with liquid metals, such as Na, as heat transfer medium. A preheated water feed, in heat transfer relationship with the liquid metals, is passed through evaporator and superheater stages, and the superheated steam is supplied to the highest pressure stage of the steam turbine arrangement. Steam extracted intermediate the evaporator and superheater stages is employed to provide reheat for the lower pressure stage of the steam turbine. Only a major portion of the preheated water feed may be evaporated and this portion separated and supplied to the superheater stage. The feature of 'steam to steam' reheat avoids a second liquid metal heat transfer and hence represents a simplification. It also reduces the hazard associated with possible steam-liquid metal contact. (U.K.)

Power plant and system for accelerating a cross compound turbine in such plant, especially one having an HTGR steam supply

International Nuclear Information System (INIS)

Jaegtnes, K.O.; Braytenbah, A.S.

1977-01-01

An electric power plant having a cross compound steam turbine and a steam source that includes a high temperature gas-cooled nuclear reactor is described. The steam turbine includes high and intermediate-pressure portions which drive a first generating means, and a low-pressure portion which drives a second generating means. The steam source supplies superheat steam to the high-pressure turbine portion, and an associated bypass permits the superheat steam to flow from the source to the exhaust of the high-pressure portion. The intermediate and low-pressure portions use reheat steam; an associated bypass permits reheat steam to flow from the source to the low-pressure exhaust. An auxiliary turbine driven by steam exhausted from the high-pressure portion and its bypass drives a gas blower to propel the coolant gas through the reactor. While the bypass flow of reheat steam is varied to maintain an elevated pressure of reheat steam upon its discharge from the source, both the first and second generating means and their associated turbines are accelerated initially by admitting steam to the intermediate and low-pressure portions. The electrical speed of the second generating means is equalized with that of the first generating means, whereupon the generating means are connected and acceleration proceeds under control of the flow through the high-pressure portion. 29 claims, 2 figures

STYLE, Steam Cycle Heat Balance for Turbine Blade Design in Marine Operation

International Nuclear Information System (INIS)

Love, J.B.; Dines, W.R.

1970-01-01

1 - Nature of physical problem solved: The programme carries out iterative steam cycle heat balance calculations for a wide variety of steam cycles including single reheat, live steam reheat and multistage moisture separation. Facilities are also available for including the steam-consuming auxiliaries associated with a marine installation. Though no attempt is made to carry out a detailed turbine blading design the programme is capable of automatically varying the blading efficiency from stage to stage according to local steam volume flow rate, dryness fraction and shaft speed. 2 - Method of solution: 3 - Restrictions on the complexity of the problem: Steam pressures to lie within range 0.2 to 5,000 lb/square inch abs steam temperatures to lie within range 50 to 1600 degrees F. Not more than 40 points per turbine expansion line; Not more than 10 expansion lines; Not more than 15 feed heaters. UNIVAC 1108 version received from FIAT Energia Nucleare, Torino, Italy

Constraining curvatonic reheating

Energy Technology Data Exchange (ETDEWEB)

Hardwick, Robert J.; Vennin, Vincent; Koyama, Kazuya; Wands, David, E-mail: robert.hardwick@port.ac.uk, E-mail: vincent.vennin@port.ac.uk, E-mail: kazuya.koyama@port.ac.uk, E-mail: david.wands@port.ac.uk [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX (United Kingdom)

2016-08-01

We derive the first systematic observational constraints on reheating in models of inflation where an additional light scalar field contributes to primordial density perturbations and affects the expansion history during reheating. This encompasses the original curvaton model but also covers a larger class of scenarios. We find that, compared to the single-field case, lower values of the energy density at the end of inflation and of the reheating temperature are preferred when an additional scalar field is introduced. For instance, if inflation is driven by a quartic potential, which is one of the most favoured models when a light scalar field is added, the upper bound T {sub reh} < 5 × 10{sup 4} GeV on the reheating temperature T {sub reh} is derived, and the implications of this value on post-inflationary physics are discussed. The information gained about reheating is also quantified and it is found that it remains modest in plateau inflation (though still larger than in the single-field version of the model) but can become substantial in quartic inflation. The role played by the vev of the additional scalar field at the end of inflation is highlighted, and opens interesting possibilities for exploring stochastic inflation effects that could determine its distribution.

Design and stability limits of the HPLWR re-heater

International Nuclear Information System (INIS)

Herbell, H.; Class, A.; Starflinger, J.; Schulenberg, T.

2010-01-01

The High Performance Light Water Reactor (HPLWR) is a particular design study of a supercritical water cooled reactor. A heat exchanger design has been proposed for the re-heater as a shell-and-tube heat exchanger. Inside the tubes fluid undergoes pseudo-condensing, e.g. it changes its density from steam-like to liquid-like properties (from 80 kg/m 3 to 582 kg/m 3 ) at supercritical pressure, whereas the shell side superheats intermediate pressure steam. For sub-critical pressures an instability has been reported by Goodykoontz and Dorsch (19679. The experiment exhibits unstable steam condensation in case of downward flow inside a tube of 7.4 mm diameter and 2.42 m length in some specific cases. The counter-current condenser was cooled with water flowing in an annulus surrounding the condenser tube. This experiment motivates the current investigation of instabilities for supercritical pseudo-condensation. The study includes static instabilities, i.e. Ledingegg instability and flow maldistribution of the parallel tubes, as well as pressure drop oscillations. At the present stage, no instabilities are predicted for the specific operation conditions of the HPLWR. The commercial system code APROS is used to perform one dimensional transient simulations of the described experiment to understand the physical mechanism. These simulations show that choking flow initiates the pressure oscillations. These periodically change steam temperatures, and consequently the condensation rate. In turn, this modifies the sound speed which is responsible for choking. Condensate reverse flow at choked conditions triggers the pressure waves. APROS simulations and experimental results agree well both in pressure amplitude and frequency. APROS simulations at supercritical pressure conditions did not exhibit any instability as the fluid velocity is clearly sub-sonic in the entire HPLWR re-heater. (authors)

Reheating of the Universe as holographic thermalization

Energy Technology Data Exchange (ETDEWEB)

Kawai, Shinsuke, E-mail: shinsuke.kawai@gmail.com [Department of Physics, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Nakayama, Yu [California Institute of Technology, 452-48, Pasadena, CA 91125 (United States); Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, Kashiwa, Chiba 277-8583 (Japan)

2016-08-10

Assuming gauge/gravity correspondence we study reheating of the Universe using its holographic dual. Inflaton decay and thermalisation of the decay products correspond to collapse of a spherical shell and formation of a blackhole in the dual anti-de Sitter (AdS) spacetime. The reheating temperature is computed as the Hawking temperature of the developed blackhole probed by a dynamical boundary, and is determined by the inflaton energy density and the AdS radius, with corrections from the dynamics of the shell collapse. For given initial energy density of the inflaton field the holographic model typically gives lower reheating temperature than the instant reheating scenario, while it is shown to be safely within phenomenological bounds.

Reheating of the Universe as holographic thermalization

Directory of Open Access Journals (Sweden)

Shinsuke Kawai

2016-08-01

Full Text Available Assuming gauge/gravity correspondence we study reheating of the Universe using its holographic dual. Inflaton decay and thermalisation of the decay products correspond to collapse of a spherical shell and formation of a blackhole in the dual anti-de Sitter (AdS spacetime. The reheating temperature is computed as the Hawking temperature of the developed blackhole probed by a dynamical boundary, and is determined by the inflaton energy density and the AdS radius, with corrections from the dynamics of the shell collapse. For given initial energy density of the inflaton field the holographic model typically gives lower reheating temperature than the instant reheating scenario, while it is shown to be safely within phenomenological bounds.

The Higgs boson can delay reheating after inflation

Science.gov (United States)

Freese, Katherine; Sfakianakis, Evangelos I.; Stengel, Patrick; Visinelli, Luca

2018-05-01

The Standard Model Higgs boson, which has previously been shown to develop an effective vacuum expectation value during inflation, can give rise to large particle masses during inflation and reheating, leading to temporary blocking of the reheating process and a lower reheat temperature after inflation. We study the effects on the multiple stages of reheating: resonant particle production (preheating) as well as perturbative decays from coherent oscillations of the inflaton field. Specifically, we study both the cases of the inflaton coupling to Standard Model fermions through Yukawa interactions as well as to Abelian gauge fields through a Chern-Simons term. We find that, in the case of perturbative inflaton decay to SM fermions, reheating can be delayed due to Higgs blocking and the reheat temperature can decrease by up to an order of magnitude. In the case of gauge-reheating, Higgs-generated masses of the gauge fields can suppress preheating even for large inflaton-gauge couplings. In extreme cases, preheating can be shut down completely and must be substituted by perturbative decay as the dominant reheating channel. Finally, we discuss the distribution of reheat temperatures in different Hubble patches, arising from the stochastic nature of the Higgs VEV during inflation and its implications for the generation of both adiabatic and isocurvature fluctuations.

PFC Performance Improvement of Ultra-supercritical Secondary Reheat Unit

Directory of Open Access Journals (Sweden)

Li Jun

2018-01-01

Full Text Available Ultra-supercritical secondary reheat unit has been widely used in the world because of its advantages of large capacity, low consumption and high efficiency etc., but rapid load change ability of the turbines to be weakened which caused by its system organization, cannot meet the requirements of power grid frequency modulation. Based on the analysis of the control characteristics of ultra-supercritical once-through reheat unit, the primary frequency control based on feed-water flow overshoot compensation is proposed. The main steam pressure generated by the feed-water is changed to improve the primary frequency control capability. The relevant control strategy has been applied to the 1000MW secondary reheating unit. The results show that the technology is feasible and has high economical efficiency.

Steam power plant

International Nuclear Information System (INIS)

Campbell, J.W.E.

1981-01-01

This invention relates to power plant forced flow boilers operating with water letdown. The letdown water is arranged to deliver heat to partly expanded steam passing through a steam reheater connected between two stages of the prime mover. (U.K.)

Device for starting a steam generator by heating sodium in a reactor

International Nuclear Information System (INIS)

Nakano, Hisao.

1975-01-01

Object: To enhance cooperation between ventilation and steam conditions of turbine and ventilation condition relative to a superheater at the time of starting a plant using a fast breeder, and to enhance safety with respect to failure of heat transmission tubes at the time of start. Structure: In a device in which steam generated in an evaporator is fed to a high pressure turbine through a super-heater and an outlet steam of high pressure turbine is reheated by means of a re-heater and fed into a turbine on the side of low pressure to drive the turbine for power generation, opening and closing valves are mounted on outlet and inlet pipes, respectively, of the heat transmission pipe in the super heater, said outlet and inlet pipes being connected by a bypass pipe. Upstream side of the opening and closing valve on the inlet pipe and the downstream side of the opening and closing valve on the outlet pipe and connected by a bypass pipe in the re-heater and said bypass pipe in the re-heater is provided with a steam heat exchanger to be heated by steam in the outlet of the superheater, and a steam line in an auxiliary boiler is connected to the side of re-heater from the opening and closing valve on the heat transmission pipe in the re-heater. (Hanada, M.)

Critical review of use of high pressure saturated steam turbine economizers in nuclear power plants

International Nuclear Information System (INIS)

Urbanek, J.

1981-01-01

In the high-pressure part of the turbine drops of moisture condensate, which causes erosion and has negative impact on the service-life of the turbine and on its thermodynamic efficiency. Various designs have been put forward to eliminate moisture. A good combination is moisture separation combined with the offtake of steam for the regeneration of feed water or for the steam re-heater. As concerns the high-pressure component of the turbine it is best to offtake steam for the feed water heater and for heating the steam between the high- and low-pressure components of the turbine. The connections of the heater and re-heater in diagrams of various manufacturers are evaluated and compared. It appears to be uneconomical to use the heater in cases where feed water would be heated to temperature considerably below its optimal value. (M.D.)

Reheating the D-brane universe via instant preheating

International Nuclear Information System (INIS)

Panda, Sudhakar; Sami, M.; Thongkool, I.

2010-01-01

We investigate a possibility of reheating in a scenario of D-brane inflation in a warped deformed conifold background which includes perturbative corrections to throat geometry sourced by a chiral operator of dimension 3/2 in the conformal field theory. The effective D-brane potential, in this case, belongs to the class of nonoscillatory models of inflation for which the conventional reheating mechanism does not work. We find that gravitational particle production is inefficient and leads to reheating temperature of the order of 10 8 GeV. We show that instant preheating is quite suitable to the present scenario and can easily reheat the universe to a temperature which is higher by about 3 orders of magnitude than its counterpart associated with gravitational particle production. The reheating temperature is shown to be insensitive to a particular choice of inflationary parameters suitable to observations.

Optimization of advanced high-temperature Brayton cycles with multiple reheat stages

International Nuclear Information System (INIS)

Haihua Zhao; Per F Peterson

2005-01-01

Full text of publication follows: This paper presents an overview and a few point designs for multiple-reheat Brayton cycle power conversion systems using high temperature molten salts (or liquid metals). All designs are derived from the General Atomics GT-MHR power conversion unit (PCU). The GT-MHR PCU is currently the only closed helium cycle system that has undergone detailed engineering design analysis, and that has turbomachinery which is sufficiently large to extrapolate to a >1000 MW(e) multiple reheat gas cycle power conversion system. Analysis shows that, with relatively small engineering modifications, multiple GT-MHR PCU's can be connected together to create a power conversion system in the >1000 MW(e) class. The resulting power conversion system is quite compact, and results in what is likely the minimum gas duct volume possible for a multiple-reheat system. To realize this, compact offset fin plate type liquid-to-gas heat exchangers (power densities from 10 to 120 MW/m 3 ) are needed. Both metal and non-metal heat exchangers are being investigated for high-temperature, gas-cooled reactors for temperatures to 1000 deg. C. Recent high temperature heat exchanger studies for nuclear hydrogen production has suggested that carbon-coated composite materials such as liquid silicon infiltrated chopped fiber carbon-carbon preformed material potentially could be used to fabricate plate fin heat exchangers with reasonable price. Different fluids such as helium, nitrogen and helium mixture, and supercritical CO 2 are compared for these multiple reheat Brayton cycles. Nitrogen and helium mixture cycle need about 40% more total PCU volume than helium cycle while keeping the same net cycle efficiency. Supercritical CO 2 needs very high pressure to optimize. Due to relatively detailed design for components such as heat exchangers, turbomachinery, and duct system, relatively accurate total pressure loss can be obtained, which results in more credible net efficiency

Evolution of design of steam generator for sodium cooled reactors

International Nuclear Information System (INIS)

Chetal, S.C.; Vaidyanathan

1997-01-01

The first sodium cooled reactor was the experimental breeder reactor (EBR-I) in usa which was commissioned in 1951 and was incidentally the first nuclear reactor to generate electrical energy. This was followed by fast breeder reactors in USSR, UK, france, USA, japan, germany and India. The use of sodium as a coolant is due to its low moderation which helps in breeding fissile fuel from fertile materials and also its high heat transfer coefficient at comparatively low velocities. The good heat transfer properties introduce thermal stresses when there are rapid changes in the sodium temperatures. Also sodium has a chemical affinity with air and water. The steam generators for sodium cooled reactors have to allow for these novel conditions and in addition, unlike other components. Choices have to be made whether it is a recirculation type as in most fossil plants or an once through unit, the power rating, shape of the tube (straight, helical, U-tube), materials (Ferritic or austenitic), with free level of sodium or not, sodium on tube side or shell side and so on. With higher pressures and steam temperatures reheating steam after partial expansion in the turbine becomes essential as in conventional turbines. For this purpose the choice of reheating fluid viz sodium or live main steam has to be made. This paper traces the evolution of steam generator designs in the different sodium cooled reactors (chronologically) and the operation experience. 16 figs., 1 tab

Reheating temperature and gauge mediation models of supersymmetry breaking

International Nuclear Information System (INIS)

Olechowski, Marek; Pokorski, Stefan; Turzynski, Krzysztof; Wells, James D.

2009-01-01

For supersymmetric theories with gravitino dark matter, the maximal reheating temperature consistent with big bang nucleosynthesis bounds arises when the physical gaugino masses are degenerate. We consider the cases of a stau or sneutrino next-to-lightest superpartner, which have relatively less constraint from big bang nucleosynthesis. The resulting parameter space is consistent with leptogenesis requirements, and can be reached in generalized gauge mediation models. Such models illustrate a class of theories that overcome the well-known tension between big bang nucleosynthesis and leptogenesis.

A system to control low pressure turbine temperatures

International Nuclear Information System (INIS)

1980-01-01

An improved system to control low pressure turbine cycle steam and metal temperatures by governing the heat transfer operation in a moisture separator-reheater is described. The use of the present invention in a pressurized water reactor or a boiling water reactor steam turbine system is demonstrated. (UK)

Operating results of 220 MW SKODA saturated steam turbines

International Nuclear Information System (INIS)

Drahy, J.

1992-01-01

One of the steam turbines produced by the SKODA Works, the 220 MW steam turbine for saturated admission steam of a speed of 3000 r.p.m. is described; it is used in nuclear power plants with 400 MW PWR type reactors. 16 units of 8 turbines each have been in operation in the Jaslovske Bohunice and Dukovany power plants with the total period of operation of all machines exceeding 750,000 hours. The 220 MW steam turbine consists of a two-flow high-pressure section and of two identical two-flow low-pressure sections. The pressure of saturated steam at the inlet of the high-pressure section is 4.32 MPa (the corresponding temperature of the saturation limit being 255 degC) and during the expansion in the high-pressure section it drops to 0.6 MPa; steam moisture reaches 12%. In a separator and two-stage reheater using blend steam, the steam is freed of the moisture and is reheated to a temperature of 217 degC. Some operational problems are discussed, as are the loss of the material of the stator parts of the high-pressure section due to corrosion-erosion wear and corrosion-erosion wear of the guide wheels of the high-pressure section, and measures are presented carried out for the reduction of the corrosion-erosion effects of wet steam. One of the serious problems were the fatigue fractures of the blades of the 4th high-pressure stage, which appeared after 20 000 to 24 000 hours of operation in the dented tee-root. The guide wheels of the 4th stage were substituted by new guide wheels with uniform pitch of the channels and with increased number of guide blades. Also discussed are the dynamic behavior of the low-pressure section of the bridge structure, the operating reliability and the heat off-take for water heating of long-distance heating systems. (Z.S.) 9 figs

A review of temperature measurement in the steel reheat furnace

International Nuclear Information System (INIS)

Martocci, A.P.; Mihalow, F.A.

1985-01-01

The incentive for conducting research and development on reheat furnaces is substantial; the domestic steel industry spent approximately one billion dollars on fuel in reheat furnaces in 1981. Bethlehem Steel Corp. spent /145 million of that total, and neither figure includes fuel consumed in soaking pits or annealing furnaces. If the authors set a goal to save 10% of these annual fuel costs, that translates into /100 million for the domestic steel industry and /14.5 million for Bethlehem Steel. These large sums of money are significant incentives. The purpose of this paper is to review the historical heating practices and equipment at steel reheat furnaces along with current practices and instrumentation

Magnetic reheating

Science.gov (United States)

Saga, Shohei; Tashiro, Hiroyuki; Yokoyama, Shuichiro

2018-02-01

We provide a new bound on the amplitude of primordial magnetic fields (PMFs) by using a novel mechanism, magnetic reheating. The damping of the magnetohydrodynamics fluid motions in a primordial plasma brings the dissipation of the PMFs. In the early Universe with z ≳ 2 × 106, cosmic microwave background (CMB) photons are quickly thermalized with the dissipated energy and shift to a different Planck distribution with a new temperature. In other words, the PMF dissipation changes the baryon-to-photon number ratio, and we name such a process magnetic reheating. From the current baryon-to-photon number ratio obtained from the big bang nucleosynthesis and CMB observations, we put the strongest constraint on the PMFs on small scales which CMB observations cannot access, B0 ≲ 1.0 μG at the scales 104 generation mechanisms of PMFs in the early Universe.

Steam turbines for nuclear power plants

International Nuclear Information System (INIS)

Stastny, M.

1983-01-01

A three-cylinder 220 MW saturated steam turbine was developed for WWER reactors by the Skoda concern. Twenty four of these turbines are currently in operation, in production or have been ordered. A 1000 MW four-cylinder turbine is being developed. The disign of the turbines has had to overcome difficulties connected with the unfavourable effects of wet steam at extreme power values. Great attention had to be devoted to the aerodynamics of control valves and to the prevention of flow separation areas. The problem of corrosion-erosion in guide wheels and the high pressure section was resolved by the use of ferritic stainless steels. For the low pressure section it was necessary to separate the moisture and to reheat the steam in the separator-reheater. Difficulties caused by the generation of wet steam in the low pressure section by spontaneous condensation were removed. Also limited was the erosion caused by droplets resulting from the disintegration of water films on the trailing edges. (A.K.)

Steam turbine generators for Sizewell 'B' nuclear power station

International Nuclear Information System (INIS)

Hesketh, J.A.; Muscroft, J.

1990-01-01

The thermodynamic cycle of the modern 3000 r/min steam turbine as applied at Sizewell 'B' is presented. Review is made of the factors affecting thermal efficiency including the special nature of the wet steam cycle and the use of moisture separation and steam reheating. Consideration is given to the optimization of the machine and cycle parameters, including particular attention to reheating and to the provision of feedheating, in order to achieve a high overall level of performance. A modular design approach has made available a family of machines suitable for the output range 600-1300 MW. The constructional features of the 630 MW Sizewell 'B' turbine generators from this range are described in detail. The importance of service experience with wet steam turbines and its influence on the design of modern turbines for pressurized water reactor (PWR) applications is discussed. (author)

Steel billet reheat simulation with growth of oxide layer and investigation on zone temperature sensitivity

International Nuclear Information System (INIS)

Dubey, Satish Kumar; Srinivasan, P.

2014-01-01

This paper presents a three-dimensional heat conduction numerical model and simulation of steel billet reheating in a reheat furnace. The model considers the growth of oxide scale on the billet surfaces. Control-volume approach and implicit scheme of finite difference method are used to discretize the transient heat conduction equation. The model is validated with analytical results subject to limited conditions. Simulations are carried out for predictions of three-dimensional temperature filed in the billet and oxide scale growth on the billet surfaces. The model predictions are in agreement with expected trends. It was found that the effect of oxide scale on billet heating is considerable. In order to investigate the effect of zone temperatures on the responses, a parametric sensitivity subject to six responses of interest are carried out using analysis of mean approach. The simulation approach and parametric study presented will be useful and applicable to the steel industry.

Cycle improvement for nuclear steam power plant

International Nuclear Information System (INIS)

Silvestri, G.J. Jr.

1976-01-01

A pressure-increasig ejector element is disposed in an extraction line intermediate to a high pressure turbine element and a feedwater heater. The ejector utilizes high pressure fluid from a reheater drain as the motive fluid to increase the pressure at which the extraction steam is introduced into the feedwater heater. The increase in pressure of the extraction steam entering the feedwater heater due to the steam passage through the ejector increases the heat exchange capability of the extraction steam thus increasing the overall steam power plant efficiency

LMFBR steam generators in the United Kingdom

International Nuclear Information System (INIS)

Anderson, R.; Hayden, O.

2002-01-01

Experience has been gained in the UK on the operation of LMFBR Steam Generator Units (SGU) over a period of 20 years from the Dounreay Fast Reactor (DFR) and the Prototype Fast Reactor (PFR). The DFR steam generator featured a double barrier and therefore did not represent a commercial design. PFR, however, faced the challenge of a single wall design and it is experience from this which is most valuable. The PFR reactor went critical in March 1974 and the plant operating history since then has been dominated by experience with leaks in the tube to tube plate welds of the high performance U-tubes SGU's. Operation at high power using the full complement of three secondary sodium circuits was delayed until July 1976 by the occurrence of leaks in the tube to tube plate welds of the superheater and reheater units which are fabricated in stainless steel. Repairs were carried out to the two superheaters and they were returned to service. The reheater tube bundle was removed from circuit after sodium was found to have entered the steam side. When the sodium had been removed and inspection carried out it was decided not to recover the unit. Since 1976 the remaining five stainless steel units have operated satisfactorily. This year a replacement reheater unit has been installed. This is of a new design in 9-Cr-Mo ferritic steel using a sleeve through which the steam tube passes to eliminate the tube to tube plate weld. Despite a few early leaks in evaporator tube to tube plate welds up to 1979, these failures did not initially present a major problem. However, in 1980 the rate of evaporator weld failures increased and despite the successful application of a shot peening process to eliminate stress corrosion failures from the water side of the weld, failures traced to the sodium side continued. A sleeving process was developed for application to complete evaporator units on a production basis with the objective of bypassing the welds at each end of the 500 tubes. The decision

Design of a high-temperature first wall/blanket for a d-d compact Reversed-Field-Pinch reactor (CRFPR)

International Nuclear Information System (INIS)

Dabiri, A.E.; Glancy, J.E.

1983-05-01

A high-temperature first wall/blanket which would take full advantage of the absence of tritium breeding in a d-d reactor was designed. This design which produces steam at p = 7 MPa and T = 538 0 C at the blanket exit eliminates the requirement for a separate steam generator. A steam cycle with steam-to-steam reheat yielding about 37.5 percent efficiency is compatible with this design

Design of PFBR steam generator

International Nuclear Information System (INIS)

Chetal, S.C.; Bhoje, S.B.; Mitra, T.K.; Paranjpe, S.R.; Vaidyanathan, G.

1990-01-01

Vertical straight tube with an expansion bend in sodium path is the design selected for the steam generators of 500 MWe Prototype Fast Breeder Reactor (PFBR). There are 4 secondary loops with each loop consisting of 3 modules. With sodium reheat incorporated each module comprises of one evaporator, superheater and reheater. Material of construction is 2.25Cr-1Mo for evaporator and 9Cr-1Mo for superheater and reheater. The tube to tubesheet weld is internal bore butt weld with tubesheet having raised spigot. Aim is to have reliable design with higher plant availability. Design considerations leading to the choice of design features selected are discussed in the paper and a ''reference'' design has been described. (author). 2 figs, 1 tab

Reheating after inflation

International Nuclear Information System (INIS)

Kripfganz, Jochen; Karl-Marx-Universitaet, Leipzig; Ilgenfritz, E.M.

1986-01-01

A numerical analysis of reheating is performed for a classical scalar field with exponentially flat potential. An operational definition of the reheating time is given involving the gradient contribution to the inflation field energy. For the parameter range studied the product of reheating time and Hubble constant H is found to be of order one, being approximately independent of the value of H. (author)

Reheating after inflation

International Nuclear Information System (INIS)

Kripfganz, J.; Ilgenfritz, E.M.

1985-07-01

A numerical analysis of reheating is performed for a classical scalar field with exponentially flat potential. An operational definition of the reheating time is given involving the gradient contribution to the inflation field energy. For the parameter range studied the product of reheating time and Hubble constant H is found to be of order one, being approximately independent of the value of H. (author)

Steam plant for pressurized water reactors

International Nuclear Information System (INIS)

Anon.

1983-01-01

This book discusses the research and development organisations and users to highlight those aspects of the steam turbine and associated plant which are particularly related to the PWR system. The contents include: Characteristics of the steam system (including feed train, dump system and safety aspects); overall design aspects of high and half speed turbines; design aspects of the steam generator and seismic considerations; moisture separators and reheaters; feed pumps and their drives; water treatment; safety related valves; operational experience; availability and performance

Design, development and operating experience with wet steam turbines

International Nuclear Information System (INIS)

Bolter, J.R.

1989-01-01

The paper first describes the special characteristics of wet steam units. It then goes on to discuss the principal features of the units manufactured by the author's company, the considerations on which the designs were based, and the development work carried out to validate them. Some of the design features such as the separator/reheater units and the arrangements for water extraction in the high pressure turbine are unconventional. An important characteristic of all nuclear plant is the combination of high capital cost and low fuel cost, and the consequent emphasis placed on high availability. The paper describes some service problems experienced with wet steam plant and how these were overcome with minimum loss of generation. The paper also describes a number of the developments for future wet steam plant which have evolved from these experiences, and from research and development programmes aimed at increasing the efficiency and reliability of both conventional and wet steam units. Blading, rotor construction and separator/reheater units are considered. (author)

Coupling of Modular High-Temperature Gas-Cooled Reactor with Supercritical Rankine Cycle

Directory of Open Access Journals (Sweden)

Shutang Zhu

2008-01-01

Full Text Available This paper presents investigations on the possible combination of modular high-temperature gas-cooled reactor (MHTGR technology with the supercritical (SC steam turbine technology and the prospective deployments of the MHTGR SC power plant. Energy conversion efficiency of steam turbine cycle can be improved by increasing the main steam pressure and temperature. Investigations on SC water reactor (SCWR reveal that the development of SCWR power plants still needs further research and development. The MHTGR SC plant coupling the existing technologies of current MHTGR module design with operation experiences of SC FPP will achieve high cycle efficiency in addition to its inherent safety. The standard once-reheat SC steam turbine cycle and the once-reheat steam cycle with life-steam have been studied and corresponding parameters were computed. Efficiencies of thermodynamic processes of MHTGR SC plants were analyzed, while comparisons were made between an MHTGR SC plant and a designed advanced passive PWR - AP1000. It was shown that the net plant efficiency of an MHTGR SC plant can reach 45% or above, 30% higher than that of AP1000 (35% net efficiency. Furthermore, an MHTGR SC plant has higher environmental competitiveness without emission of greenhouse gases and other pollutants.

Power plant and system for accelerating a cross compound turbine in such plant, especially one having an HTGR steam supply

International Nuclear Information System (INIS)

Jaegtnes, K.O.; Braytenbah, A.S.

1979-01-01

In accordance with the present invention, a power plant includes a steam source to generate superheat and reheat steam which flows through a turbine-generator and an associated bypass system. A high-pressure and an intermediate-pressure turbine portion drive a first electrical generating means, and a low-pressure turbine portion drives a second electrical generating means. A first flow of superheat steam flows through the high-pressure portion, while a second flow of reheat steam flows through the intermediate and low-pressure portions in succession. Provision is made for bypassing steam around the turbine portions; in particular, one bypass means permits a flow of superheat steam from the steam source to the exhaust of the high-pressure portion, and another bypass means allows reheated steam to pass from the source to the exhaust of the low-pressure portion. The first and second steam flows are governed independently. While one of such flows is varied for purposes of controlling the rotational speed of the first generating means according to a desired speed, the other flow is varied to regulate a power plant variable at its desired level. (author)

Hemispherical power asymmetry from scale-dependent modulated reheating

International Nuclear Information System (INIS)

McDonald, John

2013-01-01

We propose a new model for the hemispherical power asymmetry of the CMB based on modulated reheating. Non-Gaussianity from modulated reheating can be small enough to satisfy the bound from Planck if the dominant modulation of the inflaton decay rate is linear in the modulating field σ. σ must then acquire a spatially-modulated power spectrum with a red scale-dependence. This can be achieved if the primordial perturbation of σ is generated via tachyonic growth of a complex scalar field. Modulated reheating due to σ then produces a spatially modulated and scale-dependent sub-dominant contribution to the adiabatic density perturbation. We show that it is possible to account for the observed asymmetry while remaining consistent with bounds from quasar number counts, non-Gaussianity and the CMB temperature quadupole. The model predicts that the adiabatic perturbation spectral index and its running will be modified by the modulated reheating component

LMFBR steam generator development: duplex bayonet tube steam generator. Volume II

International Nuclear Information System (INIS)

DeFur, D.D.

1975-04-01

This report represents the culmination of work performed in fulfillment of ERDA Contract AT(11-1)-2426, Task Agreement 2, in which alternate steam generator designs were developed and studied. The basic bayonet tube generator design previously developed by C-E under AEC Contract AT(11-1)-3031 was expanded by incorporating duplex heat transfer tubes to enhance the unit's overall safety and reliability. The effort consisted of providing and evaluating conceptual designs of the evaporator, superheater and reheater components for a large plant LMFBR steam generator (950 MWt per heat transport loop)

Reheating experiment in the 35-ton pile

International Nuclear Information System (INIS)

Cherot, J.; Girard, Y.

1957-01-01

When the 35-ton pile was started up it was necessary for us, in order to study certain effects (xenon for example), to know the anti reactivity value of the rods as a function of their dimensions. We have made use of the possibility, in the reheating experiment, of raising the temperature of the graphite-uranium block by simple heating, in order to determine the anti reactivity curves of the rods, and from that the overall temperature coefficient. For the latter we have considered two solutions: first, one in which the average temperature of the pile is defined as our arithmetical mean of the different values given by the 28 thermocouples distributed throughout the pile; a second in which the temperature in likened to a poisoning and is balanced by the square of the flux. The way in which the measurements have been made is indicated, and the different instruments used are described. The method of reheating does not permit the separation of the temperature coefficients of uranium and of graphite. The precision obtained is only moderate, and suffers from the changes of various parameters necessary to other manipulations carried out simultaneously (life time modulators for example), and finally it is a function of the comparatively restricted time allowed. It is evident of course that more careful stabilisation at the different plateaux chosen would have necessitated long periods of reheating. (author) [fr

CMB constraints on the inflaton couplings and reheating temperature in α-attractor inflation

Science.gov (United States)

Drewes, Marco; Kang, Jin U.; Mun, Ui Ri

2017-11-01

We study reheating in α-attractor models of inflation in which the inflaton couples to other scalars or fermions. We show that the parameter space contains viable regions in which the inflaton couplings to radiation can be determined from the properties of CMB temperature fluctuations, in particular the spectral index. This may be the only way to measure these fundamental microphysical parameters, which shaped the universe by setting the initial temperature of the hot big bang and contain important information about the embedding of a given model of inflation into a more fundamental theory of physics. The method can be applied to other models of single field inflation.

Fireside corrosion of superheaters/reheaters in advanced power plants

Energy Technology Data Exchange (ETDEWEB)

Syed, A.U.; Simms, N.J.; Oakey, J.E. [Cranfield Univ. (United Kingdom). Energy Technology Centre

2010-07-01

The generation of increasing amounts of electricity while simultaneously reducing environmental emissions (CO{sub 2}, SO{sub 2}, NO{sub x} particles, etc) has become a goal for the power industry worldwide. Co-firing biomass and coal in new advanced pulverised fuel power plants is one route to address this issue, since biomass is regarded as a CO{sub 2} neutral fuel (i.e. CO{sub 2} uptake during its growth equals the CO{sub 2} emissions produced during its combustion) and such new advanced power plants operate at higher efficiencies than current plants as a result of using steam systems with high temperatures and pressures. However, co-firing has the potential to cause significant operational challenges for such power plants as amongst other issues, it will significantly change the chemistry of the deposits on the heat exchanger surfaces and the surrounding gas compositions. As a result these critical components can experience higher corrosion rates, and so shorter lives, causing increased operational costs, unless the most appropriate materials are selected for their construction. This paper reports the results of a series of 1000 hour laboratory corrosion tests that have been carried out in controlled atmosphere furnaces, to assess the effect of biomass/coal co-firing on the fireside corrosion of superheaters/reheaters. The materials used for the tests were one ferritic alloy (T92), two austenitic alloys (347HFG and HR3C) and one nickel based alloy (alloy 625). Temperatures of 600 and 650 C were used to represent the metal temperatures in advanced power plants. During these exposures, traditional mass change data were recorded as the samples were recoated with the simulated deposits. After these exposures, cross-sections through samples were prepared using standard metallographic techniques and then analysed using SEM/EDX. Pre-exposure micrometer and post-exposure image analyser measurements were used so that the metal wastage could be calculated. These data are

Thermo-economic optimization of heat recovery steam generator for a range of gas turbine exhaust temperatures

International Nuclear Information System (INIS)

Nadir, Mahmoud; Ghenaiet, Adel; Carcasci, Carlo

2016-01-01

Highlights: • Thermo-economic optimization of HRSG configurations. • The maximum value of the net present value was targeted for the economic optimization. • Three level HRSG is the best option in respect of power output and high priced medium. • Two level HRSG is the best for net benefit in low and intermediate priced mediums. - Abstract: This paper illustrates the effect of selling price on the optimum design parameters of a heat recovery steam generator (HRSG) and the selection of its ideal configuration for an outlet temperature range of 350–650 °C. The Particle Swarm Optimization (PSO) method was used, considering the steam cycle specific work as an objective to be maximized, the net present value as another objective to be maximized for the economic optimization and a combination of both. Three configurations of heat recovery steam generators are considered with one, two and three pressure levels and a reheat. The results show that, the three pressure level system is the best configuration from a thermodynamic point of view, but with respect to the economical aspect the two pressure levels is the best configuration for the low and medium selling prices (0.04 $/kW h, 0.08 $/kW h and 0.2 $/kW h), whereas the three pressure level configuration would only be interesting for a high selling price of 0.3 $/kW h and a temperature range 450–600 °C. For a temperature of 650 °C, the high cost of the three level system leads to a decrease in the net present value. As the selling price increases the optimized design parameters of the three pressure level HRSG based on economic or thermodynamic optimization are similar. The obtained results are used to elaborate a new correlation relating the net present value with the gas turbine outlet temperature, gas mass flow rate, number of levels of HRSG and selling price.

On ultraviolet freeze-in dark matter during reheating

Science.gov (United States)

Chen, Shao-Long; Kang, Zhaofeng

2018-05-01

The absence of any confirmative signals from extensive DM searching motivates us to go beyond the conventional WIMPs scenario. The feebly interacting massive particles (FIMPs) paradigm provides a good alternative which, despite of its feebly interaction with the thermal particles, still could correctly produce relic abundance without conventional DM signals. The Infrared-FIMP based on the renormalizable operators is usually suffering the very tiny coupling drawback, which can be overcome in the UltraViolet-FIMP scenario based on high dimensional effective operators. However, it is sensitive to the history of the very early Universe. The previous works terminates this sensitivity at the reheating temperature TRH. We, motivated by its UV-sensitivity, investigate the effects from the even earlier Universe, reheating era. We find that in the usual case with TRHgg mDM, the production rate during reheating is very small as long as the effective operators dimension d study the situation when TRH is even lower than mDM and DM can be directly produced during reheating if its mass does not exceed TMAX.

Estimation of Temperature Influence on Creep Rate of High-Temperature Elements in Steam Turbines and Steam Pipelines

Directory of Open Access Journals (Sweden)

A. G. Gerasimova

2011-01-01

Full Text Available The paper considers a high temperature influence on strength characteristics of steam pipelines and steam turbine parts of high and medium pressure. The charts showing a decisive temperature importance in diffuse creep have been presented in the paper. The paper contains a calculation of steel self-diffusion coefficient. Dependence Dsd = f(t for more accurate assessment of  resource characteristics of the applied steel has been proposed in the paper.

High-temperature oxidation of Zircaloy in hydrogen-steam mixtures

International Nuclear Information System (INIS)

Chung, H.M.; Thomas, G.R.

1982-09-01

Oxidation rates of Zircaloy-4 cladding tubes have been measured in hydrogen-steam mixtures at 1200 to 1700 0 C. For a given isothermal oxidation temperature, the oxide layer thicknesses have been measured as a function of time, steam supply rate, and hydrogen overpressure. The oxidation rates in the mixtures were compared with similar data obtained in pure steam and helium-steam environments under otherwise identical conditions. The rates in pure steam and helium-steam mixtures were equivalent and comparable to the parabolic rates obtained under steam-saturated conditions and reported in the literature. However, when the helium was replaced with hydrogen of equivalent partial pressure, a significantly smaller oxidation rate was observed. For high steam-supply rates, the oxidation kinetics in a hydrogen-steam mixture were parabolic, but the rate was smaller than for pure steam or helium-steam mixtures. Under otherwise identical conditions, the ratio of the parabolic rate for hydrogen-steam to that for pure steam decreased with increasing temperature and decreasing steam-supply rate

Cogeneration steam turbines from Siemens: New solutions

Science.gov (United States)

Kasilov, V. F.; Kholodkov, S. V.

2017-03-01

The Enhanced Platform system intended for the design and manufacture of Siemens AG turbines is presented. It combines organizational and production measures allowing the production of various types of steam-turbine units with a power of up to 250 MWel from standard components. The Enhanced Platform designs feature higher efficiency, improved reliability, better flexibility, longer overhaul intervals, and lower production costs. The design features of SST-700 and SST-900 steam turbines are outlined. The SST-700 turbine is used in backpressure steam-turbine units (STU) or as a high-pressure cylinder in a two-cylinder condensing turbine with steam reheat. The design of an SST-700 single-cylinder turbine with a casing without horizontal split featuring better flexibility of the turbine unit is presented. An SST-900 turbine can be used as a combined IP and LP cylinder (IPLPC) in steam-turbine or combined-cycle power units with steam reheat. The arrangements of a turbine unit based on a combination of SST-700 and SST-900 turbines or SST-500 and SST-800 turbines are presented. Examples of this combination include, respectively, PGU-410 combinedcycle units (CCU) with a condensing turbine and PGU-420 CCUs with a cogeneration turbine. The main equipment items of a PGU-410 CCU comprise an SGT5-4000F gas-turbine unit (GTU) and STU consisting of SST-700 and SST-900RH steam turbines. The steam-turbine section of a PGU-420 cogeneration power unit has a single-shaft turbine unit with two SST-800 turbines and one SST-500 turbine giving a power output of N el. STU = 150 MW under condensing conditions.

Probing the reheating temperature of the universe with a gravitational wave background

International Nuclear Information System (INIS)

Nakayama, Kazunori; Saito, Shun; Suwa, Yudai; Yokoyama, Jun'ichi

2008-01-01

The thermal history of the universe after big bang nucleosynthesis (BBN) is well understood both theoretically and observationally, and recent cosmological observations also begin to reveal the inflationary dynamics. However, the epoch between inflation and BBN is scarcely known. In this paper we show that the detection of the stochastic gravitational wave background around 1 Hz provides useful information about thermal history well before BBN. In particular, the reheating temperature of the universe may be determined by future space-based laser interferometer experiments such as DECIGO and/or BBO if it is around 10 6−9 GeV, depending on the tensor-to-scalar ratio r and dilution factor F

Correlation Between Microstructure and Low-Temperature Impact Toughness of Simulated Reheated Zones in the Multi-pass Weld Metal of High-Strength Steel

Science.gov (United States)

Kang, Yongjoon; Park, Gitae; Jeong, Seonghoon; Lee, Changhee

2018-01-01

A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal.

Reheating mechanism of the curvaton with nonminimal derivative coupling to gravity

Energy Technology Data Exchange (ETDEWEB)

Qiu, Taotao [Central China Normal University, Institute of Astrophysics, Wuhan (China); Central China Normal University, Key Laboratory of Quark and Lepton Physics (MOE) and College of Physical Science and Technology, Wuhan (China); Feng, Kaixi [Chinese Academy of Sciences, Institute of Theoretical Physics, Beijing (China)

2017-10-15

In this paper, we continue our study of the curvaton model with nonminimal derivative coupling (NDC) to Einstein gravity proposed in our previous work (Feng in Phys Lett B 729:99, 2014; Feng and Qiu in Phys Rev D 90(12):123508, 2014), focusing on the reheating mechanism. We found that according to whether the curvaton has or has not dominated the background after the end of inflation, it will have two different behaviors of evolution, which should be the general property of the curvaton with nonminimal couplings. This will cause two different parts of reheating, which goes on via the parametric resonance process. The reheating temperature is estimated for both cases in which reheating completes before and after curvaton domination, and the constraints are quite loose compared to that of overproduction of gravitinos. Finally we investigated the evolution of curvature perturbation during reheating. We have shown both analytically and numerically that the curvature perturbation will not blow up during the resonance process. (orig.)

Reheating mechanism of the curvaton with nonminimal derivative coupling to gravity

International Nuclear Information System (INIS)

Qiu, Taotao; Feng, Kaixi

2017-01-01

In this paper, we continue our study of the curvaton model with nonminimal derivative coupling (NDC) to Einstein gravity proposed in our previous work (Feng in Phys Lett B 729:99, 2014; Feng and Qiu in Phys Rev D 90(12):123508, 2014), focusing on the reheating mechanism. We found that according to whether the curvaton has or has not dominated the background after the end of inflation, it will have two different behaviors of evolution, which should be the general property of the curvaton with nonminimal couplings. This will cause two different parts of reheating, which goes on via the parametric resonance process. The reheating temperature is estimated for both cases in which reheating completes before and after curvaton domination, and the constraints are quite loose compared to that of overproduction of gravitinos. Finally we investigated the evolution of curvature perturbation during reheating. We have shown both analytically and numerically that the curvature perturbation will not blow up during the resonance process. (orig.)

ORTURB, HTGR Steam Turbine Dynamic for FSV Reactor

International Nuclear Information System (INIS)

Conklin, J.C.

2001-01-01

1 - Description of program or function: ORTURB was written specifically to calculate the dynamic behavior of the Fort St. Vrain (FSV) High- Temperature Gas-Cooled Reactor (HTGR) steam turbines. The program is divided into three main parts: the driver subroutine; turbine subroutines to calculate the pressure-flow balance of the high-, intermediate-, and low-pressure turbines; and feedwater heater subroutines. 2 - Method of solution: The program uses a relationship derived for ideal gas flow in an iterative fashion that minimizes computational time to determine the pressure and flow in the FSV steam turbines as a function of plant transient operating conditions. An important computer modeling characteristic, unique to FSV, is that the high-pressure turbine exhaust steam is used to drive the reactor core coolant circulators prior to entering the reheater. A feedwater heater dynamic simulation model utilizing seven state variables for each of the five heaters is included in the ORTURB computer simulation of the regenerative Rankine cycle steam turbines. The seven temperature differential equations are solved at each time- step using a matrix exponential method. 3 - Restrictions on the complexity of the problem: The turbine shaft is assumed to rotate at a constant (rated) speed of 3600 rpm. Energy and mass storage of steam in the high-, intermediate-, and low-pressure turbines is assumed to be negligible. These limitations exclude the use of ORTURB during a turbine transient such as startup from zero power or very low turbine flows

One-dimensional simulation for attemperator based on commissioning data of coal-fired steam power plant

International Nuclear Information System (INIS)

Cho, Baekhyun; Choi, Geunwon; Uruno, Yumi; Kim, Hyunseo; Chung, Jaewon; Kim, Hyojun; Lee, Kihyun

2017-01-01

Highlights: • An attemperator is a device to spray water into the superheated steam. • The evaporation was analyzed using the enthalpy balance from the commissioning data. • The spray atomization and its concurrent evaporation in an attemperator were physically modeled. • A simple one-dimensional simulation was conducted to verify the commissioning results. - Abstract: An attemperator is a device that is used to spray water into the superheated steam between the primary, platen, and final superheaters and the reheat lines. The goal of the attemperator is to control the temperature of the superheated steam in accordance with desired turbine-inlet temperature during both steady-state and transient operation. Because the thermowell installed at the attemperator outlet is tied back to the feedback control of the spray water, the spray water should evaporate ahead of the thermowell for accurate control of the steam temperature. In this work, the completion of the evaporation ahead of the thermowell was analyzed using the enthalpy balance from the start-up commissioning data of an 800-MW coal-fired steam power plant. In addition, the phenomena of the spray atomization and its concurrent evaporation in an attemperator were physically modeled, and a simple one-dimensional simulation was conducted to verify the analysis of the commissioning data.

Wet steam turbines for nuclear generating stations -design and operating experience

International Nuclear Information System (INIS)

Usher, J.

1977-01-01

Lecture to the Institution of Nuclear Engineers, 11 Jan. 1977. The object of this lecture was to give an account of some design features of large wet steam turbines and to show by describing some recent operational experience how their design concepts were fulfilled. Headings are as follows: effects of wet steam cycle on turbine layout and operation (H.P. turbine, L.P. turbine); turbine control and operation; water separators; and steam reheaters. (U.K.)

Steam temperature variation behind a turbine steam separator-superheater during NPP start-up

International Nuclear Information System (INIS)

Lejzerovich, A.Sh.; Melamed, A.D.

1979-01-01

To determine necessary parameters of the steam temperature automatic regulator behind the steam separator-rheater supe (SSS) of an NPP turbine the static and dynamic characteristics of the temperature change behind the SSS were studied experimentally. The measurements were carried out at the K-220-44 turbine of the Kolskaja NPP in the case of both varying turbine loads and the flow rate of the heating vapor. Disturbances caused by the opening of the regulating valve at the inlet of the heating vapor are investigated as well. It is found that due to a relatively high inertiality of the SSS a rather simple structure of the start-up steam temperature regulators behind the SSS in composition with automatated driving systems of the turbine start-up without regard for the change of the dynamic characteristics can be used

Simulation of main steam and feedwater system of full scope simulator for Qinshan 300 MW Nuclear Power Unit

International Nuclear Information System (INIS)

Zhao Xiaoyu

1996-01-01

The simulation of main steam and feedwater system is the most important and maximal part in secondary circuit model, including all of main steam and feedwater's thermal-hydraulic properties, except heat-exchange of secondary side of steam generator. It simulates main steam header, steam power in each stage of turbine, moisture separator-reheater, deaerator, condenser, high pressure and low pressure heater, auxiliary feedwater and main steam bypass in full scope

The steam pressure effect on high temperature corrosion of zircaloy-4

International Nuclear Information System (INIS)

Kim, K. P.; Park, G. H.

1998-01-01

To find the effect of pressure on the high temperature oxidation of zircaloy-4, an autoclave capable of measuring the degree of oxidation at high temperatures and high pressure was manufactured. The degree of high temperature oxidation of zircaloy-4 was measured at three different conditions, high pressure steam, high pressure Ar gas with small amount of steam, and 1 atm steam. All the measurements were done at 750 deg C. The oxide thickness is much thicker in high pressure steam, comparing to that in the 1 atm steam. And, the higher is the steam pressure, the thicker becomes the oxide. No effect was observed in the case of high pressure Ar containing small amount of steam. Many cracks exist on the surface of specimens oxidized at high pressure steam, which come from the enhanced tetragonal to monoclinic phase transformation due to high pressure steam. The enhanced oxidation seems to oxide cracking

ORTAP: a nuclear steam supply system simulation for the dynamic analysis of high temperature gas cooled reactor transients

International Nuclear Information System (INIS)

Cleveland, J.C.; Hedrick, R.A.; Ball, S.J.; Delene, J.G.

1977-01-01

ORTAP was developed to predict the dynamic behavior of the high temperature gas cooled reactor (HTGR) Nuclear Steam Supply System for normal operational transients and postulated accident conditions. It was developed for the Nuclear Regulatory Commission (NRC) as an independent means of obtaining conservative predictions of the transient response of HTGRs over a wide range of conditions. The approach has been to build sufficient detail into the component models so that the coupling between the primary and secondary systems can be accurately represented and so that transients which cover a wide range of conditions can be simulated. System components which are modeled in ORTAP include the reactor core, a typical reheater and steam generator module, a typical helium circulator and circulator turbine and the turbine generator plant. The major plant control systems are also modeled. Normal operational transients which can be analyzed with ORTAP include reactor start-up and shutdown, normal and rapid load changes. Upset transients which can be analyzed with ORTAP include reactor trip, turbine trip and sudden reduction in feedwater flow. ORTAP has also been used to predict plant response to emergency or faulted conditions such as primary system depressurization, loss of primary coolant flow and uncontrolled removal of control poison from the reactor core

IMPROVEMENT OF SLAB REHEATING PROCESS AT USIMINAS THROUGH MATHEMATICAL SIMULATION

Directory of Open Access Journals (Sweden)

Antônio Adel dos Santos

2012-09-01

Full Text Available Basic characteristics and application examples of the mathematical simulator for reheating process in walking-beam type furnaces, that has been developed and applied to Usiminas plate mill line at Ipatinga, are shown in this paper. This is a bi-dimensional mathematical model solved by the finite volume method, validated by temperature measurements inside the slab during heating and coded as a visual tool. Among these applications, the following can be highlighted: (i determination of suitable furnace zone temperatures and residence times for processing steels by accelerated cooling technology; (ii determination of slab average temperature at discharging as well as at each zone exit, supplying data to be fed to the automation system at the comissioning stage; (iii analyses of slab thermal distribution through the reheating process, enabling operational optimization

A study on different thermodynamic cycle schemes coupled with a high temperature gas-cooled reactor

International Nuclear Information System (INIS)

Qu, Xinhe; Yang, Xiaoyong; Wang, Jie

2017-01-01

Highlights: • The features of three different power generation schemes, including closed Brayton cycle, non-reheating combined cycle and reheating combined cycle, coupled with high temperature gas-cooled reactor (HTGR) were investigated and compared. • The effects and mechanism of reactor core outlet temperature, compression ratio and other key parameters over cycle characteristics were analyzed by the thermodynamic models.. • It is found that reheated combined cycle has the highest efficiency. Reactor outlet temperature and main steam parameters are key factors to improve the cycle’s performance. - Abstract: With gradual increase in reactor outlet temperature, the efficient power conversion technology has become one of developing trends of (very) high temperature gas-cooled reactors (HTGRs). In this paper, different cycle power generation schemes for HTGRs were systematically studied. Physical and mathematical models were established for these three cycle schemes: closed Brayton cycle, simple combined cycle, and reheated combined cycle. The effects and mechanism of key parameters such as reactor core outlet temperature, reactor core inlet temperature and compression ratio on the features of these cycles were analyzed. Then, optimization results were given with engineering restrictive conditions, including pinch point temperature differences. Results revealed that within the temperature range of HTGRs (700–900 °C), the reheated combined cycle had the highest efficiency, while the simple combined cycle had the lowest efficiency (900 °C). The efficiencies of the closed Brayton cycle, simple combined cycle and reheated combined cycle are 49.5%, 46.6% and 50.1%, respectively. These results provide insights on the different schemes of these cycles, and reveal the effects of key parameters on performance of these cycles. It could be helpful to understand and develop a combined cycle coupled with a high temperature reactor in the future.

Curvaton reheating in a logamediate inflationary model

International Nuclear Information System (INIS)

Campo, Sergio del; Herrera, Ramon; Saavedra, Joel; Campuzano, Cuauhtemoc; Rojas, Efrain

2009-01-01

In a logamediate inflationary universe model we introduce the curvaton field in order to bring this inflationary model to an end. In this approach we determine the reheating temperature. We also outline some interesting constraints on the parameters that describe our models. Thus, we give the parameter space in this scenario.

Pressure effects on high temperature steam oxidation of Zircaloy-4

International Nuclear Information System (INIS)

Park, Kwangheon; Kim, Kwangpyo; Ryu, Taegeun

2000-01-01

The pressure effects on Zircaloy-4 (Zry-4) cladding in high temperature steam have been analyzed. A double layer autoclave was made for the high pressure, high temperature oxidation tests. The experimental test temperature range was 700 - 900 deg C, and pressures were 0.1 - 15 MPa. Steam partial pressure turns out to be an important one rather than total pressure. Steam pressure enhances the oxidation rate of Zry-4 exponentially. The enhancement depends on the temperature, and the maximum exists between 750 - 800 deg C. Pre-existing oxide layer decreases the enhancement about 40 - 60%. The acceleration of oxidation rate by high pressure team seems to be originated from the formation of cracks by abrupt transformation of tetragonal phase in oxide, where the un-stability of tetragonal phase comes from the reduction of surface energy by steam. (author)

What can the CMB tell about the microphysics of cosmic reheating?

International Nuclear Information System (INIS)

Drewes, Marco

2016-01-01

In inflationary cosmology, cosmic reheating after inflation sets the initial conditions for the hot big bang. We investigate how CMB data can be used to study the effective potential and couplings of the inflaton during reheating to constrain the underlying microphysics. If there is a phase of preheating that is driven by a parametric resonance or other instability, then the thermal history and expansion history during the reheating era depend on a large number of microphysical parameters in a complicated way. In this case the connection between CMB observables and microphysical parameters can only established with intense numerical studies. Such studies can help to improve CMB constraints on the effective inflaton potential in specific models, but parameter degeneracies usually make it impossible to extract meaningful best-fit values for individual microphysical parameters. If, on the other hand, reheating is driven by perturbative processes, then it can be possible to constrain the inflaton couplings and the reheating temperature from CMB data. This provides an indirect probe of fundamental microphysical parameters that most likely can never be measured directly in the laboratory, but have an immense impact on the evolution of the cosmos by setting the stage for the hot big bang

Results of Steam-Water-Oxygen Treatment of the Inside of Heating Surfaces in Heat-Recovery Steam Generators of the PGU-800 Power Unit at the Perm' District Thermal Power Station

Science.gov (United States)

Ovechkina, O. V.; Zhuravlev, L. S.; Drozdov, A. A.; Solomeina, S. V.

2018-05-01

Prestarting, postinstallation steam-water-oxygen treatment (SWOT) of the natural circulation/steam reheat heat-recovery steam generators (HRSG) manufactured by OAO Krasny Kotelshchik was performed at the PGU-800 power unit of the Perm District Thermal Power Station (GRES). Prior to SWOT, steam-oxygen cleaning, passivation, and preservation of gas condensate heaters (GCH) of HRSGs were performed for 10 h using 1.3MPa/260°C/70 t/h external steam. After that, test specimens were cut out that demonstrated high strength of the passivating film. SWOT of the inside of the heating surfaces was carried out during no-load operation of the gas turbine unit with an exhaust temperature of 280-300°C at the HRSG inlet. The steam turbine was shutdown, and the generated steam was discharged into the atmosphere. Oxygen was metered into the discharge pipeline of the electricity-driven feed pumps and downcomers of the evaporators. The behavior of the concentration by weight of iron compounds and the results of investigation of cutout specimens by the drop or potentiometric method indicate that the steam-water-oxygen process makes it possible to remove corrosion products and reduce the time required to put a boiler into operation. Unlike other processes, SWOT does not require metal-intensive cleaning systems, temporary metering stations, and structures for collection of the waste solution.

Temperature control of a steam generator by means of an hybrid system PID-RLC; Control de las temperaturas de un generador de vapor mediante un sistema hibrido PID-RLC

Energy Technology Data Exchange (ETDEWEB)

Palomares Gonzalez, Daniel; Garcia Mendoza, Raul [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1991-12-31

A description is made of the design and evaluation of an hybrid control system, formed by a quadratic gaussian linear regulator (QLR) and proportional integral derivative (PID) type regulators. This scheme is used to control the reheater and secondary superheater steam temperatures of a steam generator model with a maximum capacity of 2,150,000 pounds per hour. Once applied to the model of a 300 MW steam power plant, this system showed better results than the traditional schemes and inclusively better than some modern control schemes. This fact characterizes it as a high potential system to be applied to steam power plants. [Espanol] Se describe el diseno y la evaluacion de un sistema de control hibrido, formado por un regulador lineal cuadratico gaussiano (RLC) y reguladores tipo proporcional integral derivativo (PID). Este esquema se utiliza para controlar las temperaturas de vapor del recalentador y sobrecalentador secundario del modelo de un generador de vapor con capacidad maxima de 2,150,000 libras por hora. Una vez aplicado al modelo de una unidad termoelectrica de 300 MW, este sistema produjo mejores resultados que los esquemas tradicionales e incluso mejores que algunos esquemas de control moderno. Esto lo caracteriza como un sistema con un alto potencial para aplicarse a unidades termoelectricas.

Temperature control of a steam generator by means of an hybrid system PID-RLC; Control de las temperaturas de un generador de vapor mediante un sistema hibrido PID-RLC

Energy Technology Data Exchange (ETDEWEB)

Palomares Gonzalez, Daniel; Garcia Mendoza, Raul [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1990-12-31

A description is made of the design and evaluation of an hybrid control system, formed by a quadratic gaussian linear regulator (QLR) and proportional integral derivative (PID) type regulators. This scheme is used to control the reheater and secondary superheater steam temperatures of a steam generator model with a maximum capacity of 2,150,000 pounds per hour. Once applied to the model of a 300 MW steam power plant, this system showed better results than the traditional schemes and inclusively better than some modern control schemes. This fact characterizes it as a high potential system to be applied to steam power plants. [Espanol] Se describe el diseno y la evaluacion de un sistema de control hibrido, formado por un regulador lineal cuadratico gaussiano (RLC) y reguladores tipo proporcional integral derivativo (PID). Este esquema se utiliza para controlar las temperaturas de vapor del recalentador y sobrecalentador secundario del modelo de un generador de vapor con capacidad maxima de 2,150,000 libras por hora. Una vez aplicado al modelo de una unidad termoelectrica de 300 MW, este sistema produjo mejores resultados que los esquemas tradicionales e incluso mejores que algunos esquemas de control moderno. Esto lo caracteriza como un sistema con un alto potencial para aplicarse a unidades termoelectricas.

Reheating effects in the matter power spectrum and implications for substructure

International Nuclear Information System (INIS)

Erickcek, Adrienne L.; Sigurdson, Kris

2011-01-01

The thermal and expansion history of the Universe before big bang nucleosynthesis is unknown. We investigate the evolution of cosmological perturbations through the transition from an early matter era to radiation domination. We treat reheating as the perturbative decay of an oscillating scalar field into relativistic plasma and cold dark matter. After reheating, we find that subhorizon perturbations in the decay-produced dark matter density are significantly enhanced, while subhorizon radiation perturbations are instead suppressed. If dark matter originates in the radiation bath after reheating, this suppression may be the primary cutoff in the matter power spectrum. Conversely, for dark matter produced nonthermally from scalar decay, enhanced perturbations can drive structure formation during the cosmic dark ages and dramatically increase the abundance of compact substructures. For low reheat temperatures, we find that as much as 50% of all dark matter is in microhalos with M > or approx. 0.1M + at z≅100, compared to a fraction of ∼10 -10 in the standard case. In this scenario, ultradense substructures may constitute a large fraction of dark matter in galaxies today.

Standard test method for determination of "microwave safe for reheating" for ceramicware

CERN Document Server

American Society for Testing and Materials. Philadelphia

2006-01-01

1.1 This test method determines the suitability of ceramicware for use in microwave re-heating applications. Microwave ovens are mainly used for reheating and defrosting frozen foods. Severe thermal conditions can occur while reheating foods. Typical reheating of foods requires one to five min. in the microwave at the highest power settings. Longer periods than five minutes are considered cooking. Cooking test methods and standards are not addressed in this test method. Most ceramicware is minimally absorbing of the microwave energy and will not heat up significantly. Unfortunately there are some products that absorb microwave energy to a greater extent and can become very hot in the microwave and pose a serious hazard. Additionally, the nature of microwave heating introduces radiation in a non-uniform manner producing temperature differentials in the food being cooked as well as the ceramic container holding it. The differential may become great enough to thermal shock the ware and create dangerous condition...

Temperature conditions in an LMFBR power plant from primary sodium to steam circuits

International Nuclear Information System (INIS)

Aubert, M.; Chaumont, J.M.; Mougniot, J.C.; Recolin, J.; Acket.

1977-01-01

The optimization analysis which is presented is based on an evaluation of the tender prior to contracting Super Phenix. Process constraints are reviewed: fuel limitations, turbine, steam generators; parameter selection involves major temperatures (primary ΔT 0 , steam generator water inlet temperature, turbine steam inlet temperature) or minor temperature (secondary sodium); countervailing mechanisms include upward and downward tendencies. The optimum values obtained by the method represent a coherent balanced set of parameters. So, the most significant tendency revealed by an optimization of investment costs involves the advantages of a hot system with a steam temperature above 515 0 C, but the hot temperature range is very limited (3 0 C between the hot primary sodium temperature and the steam temperature) while the cold temperatures cover a much wide range. The tolerance range within which each critical temperature may be selected without exceeding a certain cost margin per KWh is given

Assessment of uniform temperature assumption in zoning on the numerical simulation of a walking beam reheating furnace

International Nuclear Information System (INIS)

Morgado, Tiago; Coelho, Pedro J.; Talukdar, Prabal

2015-01-01

The numerical simulation of the heating process of steel slabs in a walking beam reheating furnace is reported using two different models. In one model, the turbulent reactive flow in the furnace is simulated together with the heat conduction in the slabs. The calculations are performed using a commercial code and a user-defined function is used to simulate the periodic movement of the slabs by the walking beams in the furnace. Unsteady calculations are performed until a periodic transient solution is achieved. In the second model, the furnace is divided into a small number of zones and the average temperature and chemical composition are prescribed in every zone based on the results of the first model. The unsteady heating process of the slabs is modeled using the same software and accounting for radiative transfer in the furnace and heat conduction in the slabs. The results of the first model are taken as a benchmark for the second one. It is shown that the first model predicts radiative heat fluxes and temperatures of the slabs that are consistent with previous work. The two models yield volume average temperatures of the slabs leaving the furnace that differ by less than 3%, provided that accurate values of the temperature of the gases and walls are used. The second model is computationally more economical, requiring only about 5% of the computational time of the first one. - Highlights: • The heating process of steel slabs in a reheating furnace is numerically simulated. • Unsteady calculations accounting for the periodic movement of the slabs are reported. • We compare two models differing on how the thermochemical composition is obtained. • The models predict mean slab temperatures at the exit that differ by less than 3%. • The computational time of the fastest model is only about 5% of the slowest one

Tube tightness survey during Phenix steam generator operation

International Nuclear Information System (INIS)

Cambillard, E.

1976-01-01

Phenix steam generators are once-through vessels with single-wall heat-exchange tubes. This design means that any leakage of water into the sodium must be detected as quickly as possible so that the installation can be shut down before extensive damage occurs. The detection of water leaks in Phenix steam generators is based on measurement of the concentration in the sodium, of hydrogen produced by the sodium-water reaction. Since the various modules--evaporators, superheaters, and reheaters--have no free sodium surfaces, detection of hydrogen in argon is not used in Phenix steam generators. The measurement systems employ a probe made of nickel tubes 0.3 mm thick. Hydrogen in the sodium diffuses into a chamber kept under vacuum by an ion pump. The hydrogen pressure in the chamber is measured by a quadrupole mass spectrometer. The nine measurement systems (three per steam generator) are calibrated by injecting hydrogen into the sodium of the secondary circuits. The data-processing computer calculates the hydrogen concentration in the sodium from the spectrometer signals and the probe temperatures, which are not regulated in Phenix; it generates instructions that enable the operator to act if a leak appears. So far, no leaks have been detected. These systems also make it possible to determine rates of hydrogen diffusion caused by corrosion of the steel walls on the water side

Investigation on steam oxidation behaviour of TP347H FG Part I Exposure at 256 bar

DEFF Research Database (Denmark)

Jianmin, J; Montgomery, Melanie; Larsen, OH

2005-01-01

with the aforementioned steel in coal-fired boilers and this paper focuses on the steam oxidation behaviour for specimens tested at various metal temperatures for exposure times of 7700, 23000 and 30000 hours as investigated by light optical and scanning electron microscopy. The oxide present on the specimens is a duplex......The stainless steel TP347H FG is a candidate material for the final stage tubing of superheater and reheater sections of ultra supercritical boilers operated at steam temperatures up to 620C in the mild corrosion environments of coal-firing. A series of field tests has been conducted...... oxide, where the outer layer consists of two sub-layers, an iron oxide layer and an iron-nickel oxide layer; the inner layer is chromium rich chromium-iron-nickel oxide. Microstructure examination showed that for all these samples the varying grain size of subsurface metal affected the oxide thickness...

Chilly dark sectors and asymmetric reheating

International Nuclear Information System (INIS)

Adshead, Peter; Cui, Yanou; Shelton, Jessie

2016-01-01

In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N eff , we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

Chilly dark sectors and asymmetric reheating

Energy Technology Data Exchange (ETDEWEB)

Adshead, Peter [Department of Physics, University of Illinois at Urbana-Champaign,Urbana, IL 61801 (United States); Cui, Yanou [Perimeter Institute for Theoretical Physics,Waterloo, Ontario N2L 2Y5 (Canada); Maryland Center for Fundamental Physics, University of Maryland,College Park, MD 20742 (United States); Shelton, Jessie [Department of Physics, University of Illinois at Urbana-Champaign,Urbana, IL 61801 (United States)

2016-06-06

In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N{sub eff}, we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

Chilly dark sectors and asymmetric reheating

Science.gov (United States)

Adshead, Peter; Cui, Yanou; Shelton, Jessie

2016-06-01

In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N eff , we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

Vaporization of tungsten-metal in steam at high temperatures

International Nuclear Information System (INIS)

Greene, G.A.; Finfrock, C.C.

2000-01-01

The vaporization of tungsten from the APT spallation target dominates the radiological source term for unmitigated target overheating accidents. Chemical reactions of tungsten with steam which persist to tungsten temperatures as low as 800 C result in the formation of a hydrated tungsten-oxide which has a high vapor pressure and is readily convected in a flowing atmosphere. This low-temperature vaporization reaction essentially removes the oxide film that forms on the tungsten-metal surface as soon as it forms, leaving behind a fresh metallic surface for continued oxidation and vaporization. Experiments were conducted to measure the oxidative vaporization rates of tungsten in steam as part of the effort to quantify the MT radiological source term for severe target accidents. Tests were conducted with tungsten rods (1/8 inch diameter, six inches long) heated to temperatures from approximately 700 C to 1350 C in flowing steam which was superheated to 140 C. A total of 19 experiments was conducted. Fifteen tests were conducted by RF induction heating of single tungsten rods held vertical in a quartz glass retort. Four tests were conducted in a vertically-mounted tube furnace for the low temperature range of the test series. The aerosol which was generated and transported downstream from the tungsten rods was collected by passing the discharged steam through a condenser. This procedure insured total collection of the steam along with the aerosol from the vaporization of the rods. The results of these experiments revealed a threshold temperature for tungsten vaporization in steam. For the two tests at the lowest temperatures which were tested, approximately 700 C, the tungsten rods were observed to oxidize without vaporization. The remainder of the tests was conducted over the temperature range of 800 C to 1350 C. In these tests, the rods were found to have lost weight due to vaporization of the tungsten and the missing weight was collected in the downstream condensate

Stein industrie moisture separator reheaters in 900 MW and 1300 MW PWR units behaviour and feedback

International Nuclear Information System (INIS)

Guignard, S.; Gabrel, J.; Marceau, J.; Gauchet, J.P.

1990-01-01

Various metallurgical investigations were carried out with a view to making technological modifications to the Stein Industrie designed moisture separator reheaters of the 900 MW CP0/CP1 and 1300 MW P4/P'4 plant series. Dismantling and assessment of four reheater bundles from the CP0/CP1 plants revealed tube leaks at the bends and in the straight part of the bundle due chiefly to erosion-corrosion. In addition, thickness losses due to the same phenomenon were observed on the inner walls of the vessels and internal hardware in contact with wet steam. The assessments and inspections carried out in the field on the MSR bundles of the CP0 and CP1 plants confirmed the presence of erosion-corrosion, virtually stabilized to date, and revealed fouling of bends by sequestration of particles in the circuit with presence of some pitting. Fatigue cracking of the last support plate of certain MSRs of the CP0 series was also revealed. Adoption of finned tubes of 18% chrome ferritic stainless steel (Z 2 CT 18) for spare bundles and new MSRs, protection of vessels by austenitic and/or martensitic stainless steel internal hardware, modification of water conditioning in the steam-water circuit, and implementation of some technological modifications should guarantee the longterm resistance of the MSRs [fr

Effect of inter-critically reheating temperature on microstructure and properties of simulated inter-critically reheated coarse grained heat affected zone in X70 steel

International Nuclear Information System (INIS)

Zhu, Zhixiong; Kuzmikova, Lenka; Li, Huijun; Barbaro, Frank

2014-01-01

This study investigated the influence of the inter-critical reheating temperature on the microstructure and mechanical properties of a coarse grained heat affected zone (CGHAZ) in an API 5L grade X70 pipeline steel seam weld. A Gleeble 3500 thermo-mechanical simulator was employed to duplicate particular weld thermal cycles in order to accurately assess specific regions of the weld HAZ. Detailed microstructural analysis, including investigation of the martensite–austenite (M–A) constituent, was performed using optical microscope (OM), scanning electron microscope (SEM) and selective etching techniques. It is shown that the fracture toughness of the CGHAZ is significantly reduced following exposure to a subsequent inter-critical thermal cycle. Fracture toughness gradually improves as the inter-critical temperature is increased, but does not return to the value of the original CGHAZ due to the presence of isolated large M–A particles and coarse microstructure. Significance of M–A particles to the HAZ fracture toughness is first related to the location of particles along prior austenite grain boundaries, followed by the size of individual M–A particles

Viability study for application of combined reheater cycle (CRC) to fluidized bed combustion plants; Estudio de Viabilidad para la Aplicacion del Ciclo de Recalentamiento Combinado (CRC) a Plantas de Combustion de Lecho Fuido Atmosferico

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-12-01

Basically, the project try to analyze the application viability of a first reheating in steam cycles of little power plants, useful mainly for biomass and wastes, in our case with coal blends; and a second reheating of the steam in conventional and fluidized bed combustion plants. Using in both cases the thermic energy of the exhaust gases from one gas turbine. The advantages of the CRC cycle are: (1) Reduction of the moisture in the turbine, increasing the energy efficiency and blade protection. (2) To take advantage of the waste gas energy from the gas turbine in optimum way. (3) Great operation flexibility under good efficiency results. In general, the system can use the synergy between gas, coal and waste energies with the highest global efficiency. (Author)

On finite density effects on cosmic reheating and moduli decay and implications for Dark Matter production

International Nuclear Information System (INIS)

Drewes, Marco

2014-01-01

We study the damping of an oscillating scalar field in a Friedmann-Robertson-Walker spacetime by perturbative processes, taking into account the back-reaction of the plasma of decay products on the damping rate. The scalar field may be identified with the inflaton, in which case this process resembles the reheating of the universe after inflation. It can also model a modulus that dominates the energy density of the universe at later times. We find that the finite density corrections to the damping rate can have a drastic effect on the thermal history and considerably increase both, the maximal temperature in the early universe and the reheating temperature at the onset of the radiation dominated era. As a result the abundance of some Dark Matter candidates may be considerably larger than previously estimated. We give improved analytic estimates for the maximal and the reheating temperatures and confirm them numerically in a simple model

Toward an effective field theory approach to reheating

Science.gov (United States)

Özsoy, Ogan; Giblin, John T.; Nesbit, Eva; Şengör, Gizem; Watson, Scott

2017-12-01

We investigate whether effective field theory (EFT) approaches, which have been useful in examining inflation and dark energy, can also be used to establish a systematic approach to inflationary reheating. We consider two methods. First, we extend Weinberg's background EFT to the end of inflation and reheating. We establish when parametric resonance and decay of the inflaton occurs, but also find intrinsic theoretical limitations, which make it difficult to capture some reheating models. This motivates us to next consider Cheung et al.'s EFT approach, which instead focuses on perturbations and the symmetry breaking induced by the cosmological background. Adapting the latter approach to reheating implies some new and important differences compared to the EFT of inflation. In particular, there are new hierarchical scales, and we must account for inflaton oscillations during reheating, which lead to discrete symmetry breaking. Guided by the fundamental symmetries, we construct the EFT of reheating, and as an example of its usefulness we establish a new class of reheating models and the corresponding predictions for gravity wave observations. In this paper we primarily focus on the first stages of preheating. We conclude by discussing challenges for the approach and future directions. This paper builds on ideas first proposed in the paper [O. Ozsoy, G. Sengor, K. Sinha, and S. Watson, arXiv:1507.06651.].

3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

OpenAIRE

J. Y. Jang; Y. W. Lee; C. N. Lin; C. H. Wang

2015-01-01

The reheating furnace is used to reheat the steel slabs before the hot-rolling process. The supported system includes the stationary/moving beams, and the skid buttons which block some thermal radiation transmitted to the bottom of the slabs. Therefore, it is important to analyze the steel slab temperature distribution during the heating period. A three-dimensional mathematical transient heat transfer model for the prediction of temperature distribution within the slab ha...

Effect of Scale on Slab Heat Transfer in a Walking Beam Type Reheating Furnace

OpenAIRE

Man Young Kim

2013-01-01

In this work, the effects of scale on thermal behavior of the slab in a walking-beam type reheating furnace is studied by considering scale formation and growth in a furnace environment. Also, mathematical heat transfer model to predict the thermal radiation in a complex shaped reheating furnace with slab and skid buttons is developed with combined nongray WSGGM and blocked-off solution procedure. The model can attack the heat flux distribution within the furnace and the temperature distribut...

Analysis of Precooling Injection Transient of Steam Generator for High Temperature Gas Cooled Reactor

Directory of Open Access Journals (Sweden)

Yan Wang

2017-01-01

Full Text Available 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.

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

Science.gov (United States)

Parker, Stephen S.; White, Josh; Hosemann, Peter; Nelson, Andrew

2018-02-01

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. The oxidation kinetic constant ( k) was measured as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3-5 orders of magnitude lower across the experimental temperature range. The results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

Erosion corrosion in wet steam

International Nuclear Information System (INIS)

Tavast, J.

1988-03-01

The effect of different remedies against erosion corrosion in wet steam has been studied in Barsebaeck 1. Accessible steam systems were inspected in 1984, 1985 and 1986. The effect of hydrogen peroxide injection of the transport of corrosion products in the condensate and feed water systems has also been followed through chemical analyses. The most important results of the project are: - Low alloy chromium steels with a chromium content of 1-2% have shown excellent resistance to erosion corrosion in wet steam. - A thermally sprayed coating has shown good resistance to erosion corrosion in wet steam. In a few areas with restricted accessibility minor attacks have been found. A thermally sprayed aluminium oxide coating has given poor results. - Large areas in the moisture separator/reheater and in steam extraction no. 3 have been passivated by injection of 20 ppb hydrogen peroxide to the high pressure steam. In other inspected systems no significant effect was found. Measurements of the wall thickness in steam extraction no. 3 showed a reduced rate of attack. - The injection of 20 ppb hydrogen peroxide has not resulted in any significant reduction of the iron level result is contrary to that of earlier tests. An increase to 40 ppb resulted in a slight decrease of the iron level. - None of the feared disadvantages with hydrogen peroxide injection has been observed. The chromium and cobalt levels did not increase during the injection. Neither did the lifetime of the precoat condensate filters decrease. (author)

High-temperature oxidation of Zircaloy-2 and Zircaloy-4 in steam

International Nuclear Information System (INIS)

Urbanic, V.F.; Heidrick, T.R.

1978-01-01

At temperatures above the (α + β)/β transformation temperature for zirconium alloys, steam reacts with β-Zr to form a superficial layer of zirconium oxide (ZrO 2 ) and an intermediate layer of oxygen-stabilized α-Zr. Reaction kinetics and the rate of growth of the combined (ZrO 2 + α-Zr) layer for Zircaloy-2 and Zircaloy-4 oxidation in steam were measured over the temperature range 1050-1850 o C. The reaction rates for both alloys were similar, obeyed parabolic kinetics and were not limited by gas phase diffusion. The parabolic rate constants were consistently less than those given by the Baker and Just correlation for zirconium oxidation in steam. A discontinuity was found in the temperature dependence of both the reaction rate and the rate of growth of the combined (ZrO 2 + α-Zr) layer. The discontinuity is attributed to a change in the oxide microstructure at the discontinuity temperature, an observation which is consistent with the zirconium-oxygen phase diagram. (author)

Detonation cell size measurements in high-temperature hydrogen-air-steam mixtures at the BNL high-temperature combustion facility

International Nuclear Information System (INIS)

Ciccarelli, G.; Ginsberg, T.; Boccio, J.L.

1997-11-01

The High-Temperature Combustion Facility (HTCF) was designed and constructed with the objective of studying detonation phenomena in mixtures of hydrogen-air-steam at initially high temperatures. The central element of the HTCF is a 27-cm inner-diameter, 21.3-m long cylindrical test vessel capable of being heating to 700K ± 14K. A unique feature of the HTCF is the 'diaphragmless' acetylene-oxygen gas driver which is used to initiate the detonation in the test gas. Cell size measurements have shown that for any hydrogen-air-steam mixture, increasing the initial mixture temperature, in the range of 300K to 650K, while maintaining the initial pressure of 0.1 MPa, decreases the cell size and thus makes the mixture more detonable. The effect of steam dilution on cell size was tested in stoichiometric and off-stoichiometric (e.g., equivalence ratio of 0.5) hydrogen-air mixtures. Increasing the steam dilution in hydrogen-air mixtures at 0.1 MPa initial pressure increases the cell size, irrespective of initial temperature. It is also observed that the desensitizing effect of steam diminished with increased initial temperature. A 1-dimensional, steady-state Zel'dovich, von Neumann, Doring (ZND) model, with full chemical kinetics, has been used to predict cell size for hydrogen-air-steam mixtures at different initial conditions. Qualitatively the model predicts the overall trends observed in the measured cell size versus mixture composition and initial temperature and pressure. It was found that the proportionality constant used to predict detonation cell size from the calculated ZND model reaction zone varies between 10 and 100 depending on the mixture composition and initial temperature. 32 refs., 35 figs

Nb effect on Zr-alloy oxidation under high pressure steam at high temperatures

International Nuclear Information System (INIS)

Park, Kwangheon; Yang, Sungwoo; Kim, Kyutae

2005-01-01

The high-pressure steam effects on the oxidation of Zircaloy-4 (Zry-4) and Zirlo (Zry-1%Nb) claddings at high temperature have been analyzed. Test temperature range was 700-900degC, and pressures were 1-150 bars. High pressure-steam enhances oxidation of Zry-4, and the dependency of enhancement looks exponential to steam pressure. The origin of the oxidation enhancement turned out to be the formation of cracks in oxide. The loss of tetragonal phase by high-pressure steam seems related to the crack formation. Addition of Nb as an alloying element to Zr alloy reduces significantly the steam pressure effects on oxidation. The higher compressive stresses and the smaller fraction of tetragonal oxides in Zry-1%Nb seem to be the diminished effect of high-pressure steam on oxidation. (author)

Hydrogen production from biomass pyrolysis gas via high temperature steam reforming process

International Nuclear Information System (INIS)

Wongchang, Thawatchai; Patumsawad, Suthum

2010-01-01

Full text: The aim of this work has been undertaken as part of the design of continuous hydrogen production using the high temperature steam reforming process. The steady-state test condition was carried out using syngas from biomass pyrolysis, whilst operating at high temperatures between 600 and 1200 degree Celsius. The main reformer operating parameters (e.g. temperature, resident time and steam to biomass ratio (S/B)) have been examined in order to optimize the performance of the reformer. The operating temperature is a key factor in determining the extent to which hydrogen production is increased at higher temperatures (900 -1200 degree Celsius) whilst maintaining the same as resident time and S/B ratio. The effects of exhaust gas composition on heating value were also investigated. The steam reforming process produced methane (CH 4 ) and ethylene (C 2 H 4 ) between 600 to 800 degree Celsius and enhanced production ethane (C 2 H 6 ) at 700 degree Celsius. However carbon monoxide (CO) emission was slightly increased for higher temperatures all conditions. The results show that the use of biomass pyrolysis gas can produce higher hydrogen production from high temperature steam reforming. In addition the increasing reformer efficiency needs to be optimized for different operating conditions. (author)

Advanced steel reheat furnace

Energy Technology Data Exchange (ETDEWEB)

Moyeda, D.; Sheldon, M.; Koppang, R. [Energy and Environmental Research Corp., Irvine, CA (United States); Lanyi, M.; Li, X.; Eleazer, B. [Air Products and Chemicals, Inc., Allentown, PA (United States)

1997-10-01

Energy and Environmental Research Corp. (EER) under a contract from the Department of Energy is pursuing the development and demonstration of an Advanced Steel Reheating Furnace. This paper reports the results of Phase 1, Research, which has evaluated an advanced furnace concept incorporating two proven and commercialized technologies previously applied to other high temperature combustion applications: EER`s gas reburn technology (GR) for post combustion NOx control; and Air Product`s oxy-fuel enrichment air (OEA) for improved flame heat transfer in the heating zones of the furnace. The combined technologies feature greater production throughput with associated furnace efficiency improvements; lowered NOx emissions; and better control over the furnace atmosphere, whether oxidizing or reducing, leading to better control over surface finish.

AUTOMATIC CONTROL SYSTEM OF THE DRUM BOILER SUPERHEATED STEAM TEMPERATURE.

Directory of Open Access Journals (Sweden)

Juravliov A.A.

2006-04-01

Full Text Available The control system of the temperature of the superheated steam of the drum boiler is examined. Main features of the system are the PI-controller in the external control loop and introduction of the functional component of the error signal of the external control loop with the negative feedback of the error signal between the prescribed value of steam flowrate and the signal of the steam flowrate in the exit of the boiler in the internal control loop.

Design of large steam turbines for PWR power stations

International Nuclear Information System (INIS)

Hobson, G.; Muscroft, J.

1983-01-01

The thermodynamic cycle requirements for use with pressurized water reactors are reviewed and the manner in which thermal efficiency is maximised is outlined. The special nature of the wet steam cycle associated with turbines for this type of reactor is discussed. Machine and cycle parameters are optimised to achieve high thermal efficiency, particular attention being given to arrangements for water separation and steam reheating and to provisions for feedwater heating. Principles and details of mechanical design are considered for a range of both full-speed turbines running at 3000 rpm on 50 Hz systems and half-speed turbines running at 1800 rpm on 60 Hz systems. The importance of service experience with nuclear wet steam turbines and its relevance to the design of modern turbines for pressurized water reactor applications is discussed. (author)

Corrosion behaviour of construction materials for high temperature steam electrolysers

DEFF Research Database (Denmark)

Nikiforov, Aleksey; Petrushina, Irina; Christensen, Erik

2011-01-01

temperature proton exchange membrane (PEM) steam electrolysers. Steady-state voltammetry was used in combination with scanning electron microscopy and energy-dispersive X-ray spectroscopy to evaluate the stability of the mentioned materials. It was found that stainless steels were the least resistant...... to corrosion under strong anodic polarisation. Among alloys, Ni-based showed the highest corrosion resistance in the simulated PEM electrolyser medium. In particular, Inconel 625 was the most promising among the tested corrosion-resistant alloys for the anodic compartment in high temperature steam electrolysis...

Optimization of a slab heating pattern for minimum energy consumption in a walking-beam type reheating furnace

International Nuclear Information System (INIS)

Jang, Jiin-Yuh; Huang, Jun-Bo

2015-01-01

A two-dimensional mathematical heat transfer model for the prediction of the temperature history of steel slabs was performed in order to obtain the optimal heating pattern of these slabs with minimum energy consumption in a walking-beam type reheating furnace. An algorithm developed with a simplified conjugated-gradient method combined with a shooting method, was used as an optimizer to design the furnace temperature distribution, including the preheating zone, heating zone and soaking zone temperatures. Comparison with the in-situ experimental data indicated that the present heat transfer model works well for the prediction of the thermal behavior of a slab in the reheating furnace. The effect of the furnace temperature distribution on the design requirements, such as energy required for heating a slab, slab temperature uniformity at the furnace exit and slab discharging temperature, were investigated. The parametric study results indicated that energy consumption significantly decreases with reductions in the preheating zone temperature. The optimal design also resulted in lower energy consumption for heating a slab as compared to the original operational conditions in the steel plant. - Highlights: • The heating process of steel slabs in a reheating furnace is numerically simulated. • An algorithm is developed to search for the optimal heating pattern of a slab. • Energy consumption decreases with reductions in the preheating zone temperature

Optimized Application of MSR and Steam Turbine Retrofits in Nuclear Power Plants

Energy Technology Data Exchange (ETDEWEB)

Crossland, Robert; McCoach, John [ALSTOM Power, Willans Works, Newbold Road, Rugby, Warwickshire CV21 2NH (United Kingdom); Gagelin, Jean-Philippe [ALSTOM Power Heat Exchange, 19-21 avenue Morane-Saulnier, BP 65, 78143 Velizy Cedex (France)

2004-07-01

The benefit to a nuclear power plant from a steam turbine retrofit has often been clearly demonstrated in recent years but, for light water nuclear plants, the Moisture Separator Reheaters (MSRs) are also of prime importance. This paper describes how refurbishment of these crucial components can only provide full potential performance benefit when made in conjunction with a steam turbine retrofit (although in practice these activities are frequently separated). Examples are given to show how combined application is best handled within a single organization to ensure optimized integration into the thermal cycle. (authors)

Optimized Application of MSR and Steam Turbine Retrofits in Nuclear Power Plants

International Nuclear Information System (INIS)

Crossland, Robert; McCoach, John; Gagelin, Jean-Philippe

2004-01-01

The benefit to a nuclear power plant from a steam turbine retrofit has often been clearly demonstrated in recent years but, for light water nuclear plants, the Moisture Separator Reheaters (MSRs) are also of prime importance. This paper describes how refurbishment of these crucial components can only provide full potential performance benefit when made in conjunction with a steam turbine retrofit (although in practice these activities are frequently separated). Examples are given to show how combined application is best handled within a single organization to ensure optimized integration into the thermal cycle. (authors)

Reheating, multifield inflation and the fate of the primordial observables

International Nuclear Information System (INIS)

Leung, Godfrey; Tarrant, Ewan R.M.; Copeland, Edmund J.; Byrnes, Christian T.

2012-01-01

We study the effects of perturbative reheating on the evolution of the curvature perturbation ζ, in two-field inflation models. We use numerical methods to explore the sensitivity of f NL , n ζ and r to the reheating process, and present simple qualitative arguments to explain our results. In general, if a large non-Gaussian signal exists at the start of reheating, it will remain non-zero at the end of reheating. Unless all isocurvature modes have completely decayed before the start of reheating, we find that the non-linearity parameter, f NL , can be sensitive to the reheating timescale, and that this dependence is most appreciable for 'runaway' inflationary potentials that only have a minimum in one direction. For potentials with a minimum in both directions, f NL can also be sensitive to reheating if a mild hierarchy exists between the decay rates of each field. Within the class of models studied, we find that the spectral index n ζ , is fairly insensitive to large changes in the field decay rates, indicating that n ζ is a more robust inflationary observable, unlike the non-linearity parameter f NL . Our results imply that the statistics of ζ, especially f NL , can only be reliably used to discriminate between models of two-field inflation if the physics of reheating are properly accounted for

Thermodynamic evaluation of supercritical oxy-type power plant with high-temperature three-end membrane for air separation

Directory of Open Access Journals (Sweden)

Kotowicz Janusz

2014-09-01

Full Text Available Among the technologies which allow to reduce greenhouse gas emissions, mainly of carbon dioxide, special attention deserves the idea of ‘zero-emission’ technology based on boilers working in oxy-combustion technology. In the paper a thermodynamic analysis of supercritical power plant fed by lignite was made. Power plant consists of: 600 MW steam power unit with live steam parameters of 650 °C/30 MPa and reheated steam parameters of 670 °C/6 MPa; circulating fluidized bed boiler working in oxy-combustion technology; air separation unit and installation of the carbon dioxide compression. Air separation unit is based on high temperature membrane working in three-end technology. Models of steam cycle, circulation fluidized bed boiler, air separation unit and carbon capture installation were made using commercial software. After integration of these models the net electricity generation efficiency as a function of the degree of oxygen recovery in high temperature membrane was analyzed.

Estimation of water level and steam temperature using ensemble Kalman filter square root (EnKF-SR)

Science.gov (United States)

Herlambang, T.; Mufarrikoh, Z.; Karya, D. F.; Rahmalia, D.

2018-04-01

The equipment unit which has the most vital role in the steam-powered electric power plant is boiler. Steam drum boiler is a tank functioning to separate fluida into has phase and liquid phase. The existence in boiler system has a vital role. The controlled variables in the steam drum boiler are water level and the steam temperature. If the water level is higher than the determined level, then the gas phase resulted will contain steam endangering the following process and making the resulted steam going to turbine get less, and the by causing damages to pipes in the boiler. On the contrary, if less than the height of determined water level, the resulted height will result in dry steam likely to endanger steam drum. Thus an error was observed between the determined. This paper studied the implementation of the Ensemble Kalman Filter Square Root (EnKF-SR) method in nonlinear model of the steam drum boiler equation. The computation to estimate the height of water level and the temperature of steam was by simulation using Matlab software. Thus an error was observed between the determined water level and the steam temperature, and that of estimated water level and steam temperature. The result of simulation by Ensemble Kalman Filter Square Root (EnKF-SR) on the nonlinear model of steam drum boiler showed that the error was less than 2%. The implementation of EnKF-SR on the steam drum boiler r model comprises of three simulations, each of which generates 200, 300 and 400 ensembles. The best simulation exhibited the error between the real condition and the estimated result, by generating 400 ensemble. The simulation in water level in order of 0.00002145 m, whereas in the steam temperature was some 0.00002121 kelvin.

Linear parameter-varying modeling and control of the steam temperature in a Canadian SCWR

Energy Technology Data Exchange (ETDEWEB)

Sun, Peiwei, E-mail: sunpeiwei@mail.xjtu.edu.cn; Zhang, Jianmin; Su, Guanghui

2017-03-15

Highlights: • Nonlinearity of Canadian SCWR is analyzed based on step responses and Nyquist plots. • LPV model is derived through Jacobian linearization and curve fitting. • An output feedback H{sub ∞} controller is synthesized for the steam temperature. • The control performance is evaluated by step disturbances and wide range operation. • The controller can stabilize the system and reject the reactor power disturbance. - Abstract: The Canadian direct-cycle Supercritical Water-cooled Reactor (SCWR) is a pressure-tube type SCWR under development in Canada. The dynamics of the steam temperature have a high degree of nonlinearity and are highly sensitive to reactor power disturbances. Traditional gain scheduling control cannot theoretically guarantee stability for all operating regions. The control performance can also be deteriorated when the controllers are switched. In this paper, a linear parameter-varying (LPV) strategy is proposed to solve such problems. Jacobian linearization and curve fitting are applied to derive the LPV model, which is verified using a nonlinear dynamic model and determined to be sufficiently accurate for control studies. An output feedback H{sub ∞} controller is synthesized to stabilize the steam temperature system and reject reactor power disturbances. The LPV steam temperature controller is implemented using a nonlinear dynamic model, and step changes in the setpoints and typical load patterns are carried out in the testing process. It is demonstrated through numerical simulation that the LPV controller not only stabilizes the steam temperature under different disturbances but also efficiently rejects reactor power disturbances and suppresses the steam temperature variation at different power levels. The LPV approach is effective in solving control problems of the steam temperature in the Canadian SCWR.

Hydrogen yield from low temperature steam reforming of ethanol

Energy Technology Data Exchange (ETDEWEB)

Das, N.K.; Dalai, A.K. [Saskatchewan Univ., Saskatoon, SK (Canada). Dept. of Chemical Engineering, Catalysis and Chemical Reaction Engineering Laboratories; Ranganathan, R. [Saskatchewan Research Council, Saskatoon, SK (Canada)

2007-02-15

Interest in the use of ethanol for fuel cell hydrogen production was discussed with particular reference to a study in which the production of hydrogen was maximized through low temperature steam reforming of ethanol in the temperature range of 200 to 360 degrees C. The primary objective of this study was to determine the effect of Mn concentration on a Cu/Al{sub 2}O{sub 3} catalyst for steam reforming of ethanol to produce hydrogen. The purpose was to maximize ethanol conversion and hydrogen selectivity in the lowest possible reaction temperature for the ideal catalyst activity. The optimum reaction conditions in the presence of a suitable catalyst can produce the desired products of hydrogen and carbon dioxide. Cu/Al{sub 2}O{sub 3} catalysts with six different concentrations ranging from 0 to 10 weight per cent Mn, were prepared, characterized and studied for the ethanol-steam reforming reaction. The effects of different process variables were studied, including water-to-ethanol feed ratio, space time and catalyst reduction temperatures on ethanol conversion and hydrogen yield. Maximum ethanol conversion of 60.7 per cent and hydrogen yield of 3.74 (mol of hydrogen per mol of ethanol converted) were observed at 360 degrees C for a catalyst with 2.5 weight per cent Mn loading. 29 refs., 3 tabs., 12 figs.

Detection and evaluation of corrosion zones at high temperature in steam generators; Deteccion y evaluacion de zonas de corrosion en alta temperatura de generadoras de vapor

Energy Technology Data Exchange (ETDEWEB)

Martinez Villafane, Alberto; Chacon Nava, Jose G; Huerta Espino, Mario; Mojica Calderon, Cecilio; Castillo Viveros, Antonio [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1991-12-31

This paper presents the methodology for the detection and evaluation of high corrosion zones at high temperature. The results found up to now, show a critical zone in the Babcock Hitachi design, specifically in the high temperature reheater in the zone nearby the outlet header. In the normalized design CE (Mitsubishi) of 300 MW and CE (Canada) of 300 MW, the results found in recent years show small thickness reduction, therefore a good operation of these steam generators is recognized. [Espanol] En este trabajo se presenta la metodologia para la deteccion y evaluacion de zonas de corrosion en alta temperatura. Los resultados encontrados hasta el momento muestran una zona critica en el diseno Babcock Hitachi, especificamente en el recalentador de alta temperatura en la zona cercana al cabezal de salida. En el diseno normalizado CE (Mitsubishi) de 300 MW y CE (Canada) de 300 MW, los resultados encontrados en anos recientes muestran poca disminucion de espesor, por lo que se considera una buena operacion de estos generadores de vapor.

Detection and evaluation of corrosion zones at high temperature in steam generators; Deteccion y evaluacion de zonas de corrosion en alta temperatura de generadoras de vapor

Energy Technology Data Exchange (ETDEWEB)

Martinez Villafane, Alberto; Chacon Nava, Jose G.; Huerta Espino, Mario; Mojica Calderon, Cecilio; Castillo Viveros, Antonio [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1990-12-31

This paper presents the methodology for the detection and evaluation of high corrosion zones at high temperature. The results found up to now, show a critical zone in the Babcock Hitachi design, specifically in the high temperature reheater in the zone nearby the outlet header. In the normalized design CE (Mitsubishi) of 300 MW and CE (Canada) of 300 MW, the results found in recent years show small thickness reduction, therefore a good operation of these steam generators is recognized. [Espanol] En este trabajo se presenta la metodologia para la deteccion y evaluacion de zonas de corrosion en alta temperatura. Los resultados encontrados hasta el momento muestran una zona critica en el diseno Babcock Hitachi, especificamente en el recalentador de alta temperatura en la zona cercana al cabezal de salida. En el diseno normalizado CE (Mitsubishi) de 300 MW y CE (Canada) de 300 MW, los resultados encontrados en anos recientes muestran poca disminucion de espesor, por lo que se considera una buena operacion de estos generadores de vapor.

Higgs Inflation, Reheating and Gravitino Production in No-Scale Supersymmetric GUTs

CERN Document Server

Ellis, John; Xianyu, Zhong-Zhi

2016-08-30

We extend our previous study of supersymmetric Higgs inflation in the context of no-scale supergravity and grand unification, to include models based on the flipped SU(5) and the Pati-Salam group. Like the previous SU(5) GUT model, these yield a class of inflation models whose inflation predictions interpolate between those of the quadratic chaotic inflation and Starobinsky-like inflation, while also avoiding tension with proton decay limits. We further analyse the reheating process in these models, and derive the number of $e$-folds, which is independent of the reheating temperature. We derive the corresponding predictions for the scalar tilt and the tensor-to-scalar ratio in cosmic microwave background perturbations, and also discuss gravitino production following inflation.

Higgs inflation, reheating and gravitino production in no-scale Supersymmetric GUTs

Energy Technology Data Exchange (ETDEWEB)

Ellis, John [Theoretical Particle Physics and Cosmology Group,Department of Physics, King’s College London,London WC2R 2LS (United Kingdom); Theoretical Physics Department, CERN,CH-1211 Geneva 23 (Switzerland); He, Hong-Jian [Institute of Modern Physics and Center for High Energy Physics, Tsinghua University,Beijing 100084 (China); Center for High Energy Physics, Peking University,Beijing 100871 (China); Xianyu, Zhong-Zhi [Center of Mathematical Sciences and Applications andDepartment of Physics, Harvard University,Massachusetts 02138 (United States)

2016-08-30

We extend our previous study of supersymmetric Higgs inflation in the context of no-scale supergravity and grand unification, to include models based on the flipped SU(5) and the Pati-Salam group. Like the previous SU(5) GUT model, these yield a class of inflation models whose inflation predictions interpolate between those of the quadratic chaotic inflation and Starobinsky-like inflation, while avoiding tension with proton decay limits. We further analyse the reheating process in these models, and derive the number of e-folds, which is independent of the reheating temperature. We derive the corresponding predictions for the scalar tilt and the tensor-to-scalar ratio in cosmic microwave background perturbations, as well as discussing the gravitino production following inflation.

Development of Next Generation Heating System for Scale Free Steel Reheating

Energy Technology Data Exchange (ETDEWEB)

Dr. Arvind C. Thekdi

2011-01-27

The work carried out under this project includes development and design of components, controls, and economic modeling tools that would enable the steel industry to reduce energy intensity through reduction of scale formation during the steel reheating process. Application of scale free reheating offers savings in energy used for production of steel that is lost as scale, and increase in product yield for the global steel industry. The technology can be applied to a new furnace application as well as retrofit design for conversion of existing steel reheating furnaces. The development work has resulted in the knowledge base that will enable the steel industry and steel forging industry us to reheat steel with 75% to 95% reduction in scale formation and associated energy savings during the reheating process. Scale reduction also results in additional energy savings associated with higher yield from reheat furnaces. Energy used for steel production ranges from 9 MM Btu/ton to 16.6 MM Btu/ton or the industry average of approximately 13 MM Btu/ton. Hence, reduction in scale at reheating stage would represent a substantial energy reduction for the steel industry. Potential energy savings for the US steel industry could be in excess of 25 Trillion Btu/year when the technology is applied to all reheating processes. The development work has resulted in new design of reheating process and the required burners and control systems that would allow use of this technology for steel reheating in steel as well as steel forging industries.

Detection of leaks in steam lines by distributed fibre-optic temperature sensing (DTS)

Energy Technology Data Exchange (ETDEWEB)

Craik, N G [Maritime Nuclear, Fredericton, N.B. (Canada)

1997-12-31

This paper describes an instrumentation system concept which should be capable of early detection of a leak-before-break in main steam lines. Distributed fibre-optic Temperature Sensing (DTS) systems have been used in commercial application for a few years now, but in other industries and applications. DTS uses very long fibre optical cable both as a temperature sensor and as a means of bringing the information back from the sensor to the terminal equipment. The entire length of the fibre is sensitive to temperature and each resolvable section of fibre is equivalent to a point sensor. This commercially available DTS system could be adapted to indicate leaks in steam lines. The fibre-optic cable could either be run either just underneath the aluminium sheathing covering the installation over a steam line, or between the two layers of insulation. This would detect an increase in the temperature of the insulation due to a steam leak. 1 ref., 4 figs.

Detection of leaks in steam lines by distributed fibre-optic temperature sensing (DTS)

International Nuclear Information System (INIS)

Craik, N.G.

1996-01-01

This paper describes an instrumentation system concept which should be capable of early detection of a leak-before-break in main steam lines. Distributed fibre-optic Temperature Sensing (DTS) systems have been used in commercial application for a few years now, but in other industries and applications. DTS uses very long fibre optical cable both as a temperature sensor and as a means of bringing the information back from the sensor to the terminal equipment. The entire length of the fibre is sensitive to temperature and each resolvable section of fibre is equivalent to a point sensor. This commercially available DTS system could be adapted to indicate leaks in steam lines. The fibre-optic cable could either be run either just underneath the aluminium sheathing covering the installation over a steam line, or between the two layers of insulation. This would detect an increase in the temperature of the insulation due to a steam leak. 1 ref., 4 figs

Investigations to the potential of the high temperature reactor for steam power processes with highest steam conditions and comparison with according conventional power plants

International Nuclear Information System (INIS)

Mondry, M.

1988-04-01

Already in the fifties conventional power plants with high parameters of the live steam were built to improve the total efficiency. The power plant with the highest steam conditions in the Federal Republic of Germany has 300 bar pressure and 600deg C temperature. Because of high material costs and other problems power plants with such high conditions were not continued to be built. Standard conditions of today's power plants are in the order of 180-250 bar pressure and 535deg C temperature. As the high temperature reactor is partly built up in another way than a conventional power plant, the results regarding the high steam parameters are not transferable. Possibilities for the technical realization of determined HTR-specific components are introduced and discussed. Then different HTR-power plants with steam conditions up to 350 bar pressure and 650deg C temperature are projected. Economical considerations show that an HTR with higher steam parameters brings financial profits. Further efficiency increase, which is possible by the high steam conditions, is shortly presented. The work ends with a technical and economical comparison of corresponding conventional power plants. (orig./UA) [de

On the evaluation of lifetime of evaporative tubes of once-through steam generators at steam-generating surface temperature oscillations in the burnout region

International Nuclear Information System (INIS)

Vorob'ev, V.A.; Loshchinin, V.M.; Remizov, O.V.

1978-01-01

Suggested is a method for evaluation of a stressed state of evaporation tubes of once-through steam generators at temperature oscillations in the burnout region. Calculated is the amplitude of steam-generating surface temperature oscillations in the burnout region depending on the frequency of a liquid-steam boundary transfer and on this basis determined are thermal stresses in a tube wall. Knowing a fatigue curve gives the possibility to evaluate a heat transfer tube lifetime

The temperature control and water quality regulation for steam generator secondary side hydrostatic test

International Nuclear Information System (INIS)

Xiao Bo; Liu Dongyong

2014-01-01

The secondary side hydrostatic test for the steam generator of M310 unit is to verify the pressure tightness of steam generator secondary side tube sheet and related systems. As for the importance of the steam generator, the water temperature and water quality of hydrostatic test has strict requirements. The discussion on the water temperature control and water quality regulation for the secondary loop hydrostatic test of Fuqing Unit 1 contribute greatly to the guiding work for the preparation of the steam generator pressure test for M310 unit. (authors)

Reheat cracking in 1/2 CrMoV steel. Heat affected zones

International Nuclear Information System (INIS)

Batte, A.D.; Miller, R.C.; Murphy, M.C.

1976-01-01

Low alloy creep resisting steels are inherently susceptible to cracking during stress relief heat treatment (reheat cracking) though few welds give rise to problems in manufacture or service. Mechanical tests on simulated affected zone structures in CrMoV forgings have shown that cracking occurs when the high temperature ductility is inadequate to accommodate the residual welding strain. Differences in susceptibility result from differences in heat affected zone grain size if the purity level is sufficiently high; reheat cracking may then be avoided by ensuring complete grain refinement during welding. The susceptibility of a lower purity forging was insensitive to grain size; heat affected zone refinement is unlikely to eliminate cracking in such steel. (orig.) [de

Stress corrosion cracking in superheater and reheater austenitic tubing

Energy Technology Data Exchange (ETDEWEB)

Dooley, R. Barry [Structural Integrity Associates, Inc., Charlotte, NC (United States); Bursik, Albert [PowerPlant Chemistry GmbH, Neulussheim (Germany)

2011-02-15

University 101 courses are typically designed to help incoming first-year undergraduate students to adjust to the university, develop a better understanding of the college environment, and acquire essential academic success skills. Why are we offering a special Boiler and HRSG Tube Failures PPChem 101? The answer is simple, yet very conclusive: - There is a lack of knowledge on the identification of tube failure mechanisms and for the implementation of adequate counteractions in many power plants, particularly at industrial power and steam generators. - There is a lack of knowledge to prevent repeat tube failures. The vast majority of BTF/HTF have been, and continue to be, repeat failures. It is hoped that the information about the failure mechanisms of BTF supplied in this course will help to put plant engineers and chemists on the right track. The major goal of this course is the avoidance of repeat BTF. This eights lesson is focused on Stress Corrosion Cracking in Superheater and Reheater Austenitic Tubing. (orig.)

ANALISIS KEHILANGAN STEAM DAN PENURUNAN TEMPERATUR PADA JARINGAN DISTRIBUSI STEAM DARI PT. KDM KE PT. KNI

Directory of Open Access Journals (Sweden)

Ahmad Yani

2017-12-01

• Perlu pengecekan dan perbaikan berkala sehingga setiap kerusakan yang terjadi dapat diketahui secara dini.    Kata Kunci: kehilangan uap (steam loss, penurunan temperatur, dan jaringan distribusi.

Mathematical modelling of steam generator and design of temperature regulator

Energy Technology Data Exchange (ETDEWEB)

Bogdanovic, S.S. [EE Institute Nikola Tesla, Belgrade (Yugoslavia)

1999-07-01

The paper considers mathematical modelling of once-through power station boiler and numerical algorithm for simulation of the model. Fast and numerically stable algorithm based on the linearisation of model equations and on the simultaneous solving of differential and algebraic equations is proposed. The paper also presents the design of steam temperature regulator by using the method of projective controls. Dynamic behaviour of the system closed with optimal linear quadratic regulator is taken as the reference system. The desired proprieties of the reference system are retained and solutions for superheated steam temperature regulator are determined. (author)

Thermodynamic analysis of SCW NPP cycles with thermo-chemical co-generation of hydrogen

International Nuclear Information System (INIS)

Naidin, N.; Mokry, S.; Monichan, R.; Chophla, K.; Pioro, I.; Naterer, G.; Gabriel, K.

2009-01-01

Research activities are currently conducted worldwide to develop Generation IV nuclear reactor concepts with the objective of improving thermal efficiency and increasing economic competitiveness of Generation IV Nuclear Power Plants (NPPs) compared to modern thermal power plants. The Super-Critical Water-cooled Reactor (SCWR) concept is one of the six Generation IV options chosen for further investigation and development in several countries including Canada and Russia. Water-cooled reactors operating at subcritical pressures (10 - 16 MPa) have provided a significant amount of electricity production for the past 50 years. However, the thermal efficiency of the current NPPs is not very high (30 - 35%). As such, more competitive designs, with higher thermal efficiencies, which will be close to that of modern thermal power plants (45 - 50%), need to be developed and implemented. Super-Critical Water (SCW) NPPs will have much higher operating parameters compared to current NPPs (i.e., steam pressures of about 25 MPa and steam outlet temperatures up to 625 o C). Furthermore, SCWRs operating at higher temperatures can facilitate an economical co-generation of hydrogen through thermochemical cycles (particularly, the copper-chlorine cycle) or direct high-temperature electrolysis. The two SCW NPP cycles proposed by this paper are based on direct, regenerative, no-reheat and single-reheat configurations. As such, the main parameters and performance in terms of thermal efficiency of the SCW NPP concepts mentioned above are being analyzed. The cycles are generally comprised of: an SCWR, a SC turbine, one deaerator, ten feedwater heaters, and pumps. The SC turbine of the no-reheat cycle consists of one High-Pressure (HP) cylinder and two Low-Pressure (LP) cylinders. Alternatively, the SC turbine for the single-reheat cycle is comprised of one High-Pressure (HP) cylinder, one Intermediate-Pressure (IP) cylinder and two Low-Pressure (LP) cylinders. Since the single-reheat option

High-temperature hydrogen-air-steam detonation experiments in the BNL small-scale development apparatus

International Nuclear Information System (INIS)

Ciccarelli, G.; Ginsburg, T.; Boccio, J.; Economos, C.; Finfrock, C.; Gerlach, L.; Sato, K.; Kinoshita, M.

1994-08-01

The Small-Scale Development Apparatus (SSDA) was constructed to provide a preliminary set of experimental data to characterize the effect of temperature on the ability of hydrogen-air-steam mixtures to undergo detonations and, equally important, to support design of the larger scale High-Temperature Combustion Facility (HTCF) by providing a test bed for solution of a number of high-temperature design and operational problems. The SSDA, the central element of which is a 10-cm inside diameter, 6.1-m long tubular test vessel designed to permit detonation experiments at temperatures up to 700K, was employed to study self-sustained detonations in gaseous mixtures of hydrogen, air, and steam at temperatures between 300K and 650K at a fixed initial pressure of 0.1 MPa. Hydrogen-air mixtures with hydrogen composition from 9 to 60 percent by volume and steam fractions up to 35 percent by volume were studied for stoichiometric hydrogen-air-steam mixtures. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air gas mixture temperature, in the range 300K-650K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm inside diameter SSDA test vessel, based upon the onset of single-head spin, decreased from 15 percent hydrogen at 300K down to between 9 and 10 percent hydrogen at 650K. The one-dimensional ZND model does a very good job at predicting the overall trends in the cell size data over the range of hydrogen-air-steam mixture compositions and temperature studied in the experiments

Steam generator materials performance in high temperature gas-cooled reactors

International Nuclear Information System (INIS)

Chafey, J.E.; Roberts, D.I.

1980-11-01

This paper reviews the materials technology aspects of steam generators for HTGRs which feature a graphite-moderated, uranium-thorium, all-ceramic core and utilizes high-pressure helium as the primary coolant. The steam generators are exposed to gas-side temperatures approaching 760 0 C and produce superheated steam at 538 0 C and 16.5 MPa (2400 psi). The prototype Peach Bottom I 40-MW(e) HTGR was operated for 1349 EFPD over 7 years. Examination after decommissioning of the U-tube steam generators and other components showed the steam generators to be in very satisfactory condition. The 330-MW(e) Fort St. Vrain HTGR, now in the final stages of startup, has achieved 70% power and generated more than 1.5 x 10 6 MWh of electricity. The steam generators in this reactor are once-through units of helical configuration, requiring a number of new materials factors including creep-fatigue and water chemistry control. Current designs of larger HTGRs also feature steam generators of helical once-through design. Materials issues that are important in these designs include detailed consideration of time-dependent behavior of both base metals and welds, as required by current American Society of Mechanical Engineers (ASME) Code rules, evaluation of bimetallic weld behavior, evaluation of the properties of large forgings, etc

Creep performance of oxide ceramic fiber materials at elevated temperature in air and in steam

Science.gov (United States)

Armani, Clinton J.

Structural aerospace components that operate in severe conditions, such as extreme temperatures and detrimental environments, require structural materials that have superior long-term mechanical properties and that are thermochemically stable over a broad range of service temperatures and environments. Ceramic matrix composites (CMCs) capable of excellent mechanical performance in harsh environments are prime candidates for such applications. Oxide ceramic materials have been used as constituents in CMCs. However, recent studies have shown that high-temperature mechanical performance of oxide-oxide CMCs deteriorate in a steam-rich environment. The degradation of strength at elevated temperature in steam has been attributed to the environmentally assisted subcritical crack growth in the oxide fibers. Furthermore, oxide-oxide CMCs have shown significant increases in steady-state creep rates in steam. The present research investigated the effects of steam on the high-temperature creep and monotonic tension performance of several oxide ceramic materials. Experimental facilities were designed and configured, and experimental methods were developed to explore the influence of steam on the mechanical behaviors of ceramic fiber tows and of ceramic bulk materials under temperatures in the 1100--1300°C range. The effects of steam on creep behavior of Nextel(TM)610 and Nextel(TM)720 fiber tows were examined. Creep rates at elevated temperatures in air and in steam were obtained for both types of fibers. Relationships between creep rates and applied stresses were modeled and underlying creep mechanisms were identified. For both types of fiber tows, a creep life prediction analysis was performed using linear elastic fracture mechanics and a power-law crack velocity model. These results have not been previously reported and have critical design implications for CMC components operating in steam or near the recommended design limits. Predictions were assessed and validated via

Steam temperature control of essential oil extraction system using ...

African Journals Online (AJOL)

This research proposed a closed-loop temperature control using a self-tuning fuzzy fractional-order PI (FOPI) controller to overcome the problem. The controller will regulate the steam temperature at a desired level to protect the oil from excessive heat. Self capability of fuzzy rules was found to facilitate the tuning using only ...

Effect of reheating on predictions following multiple-field inflation

Science.gov (United States)

Hotinli, Selim C.; Frazer, Jonathan; Jaffe, Andrew H.; Meyers, Joel; Price, Layne C.; Tarrant, Ewan R. M.

2018-01-01

We study the sensitivity of cosmological observables to the reheating phase following inflation driven by many scalar fields. We describe a method which allows semianalytic treatment of the impact of perturbative reheating on cosmological perturbations using the sudden decay approximation. Focusing on N -quadratic inflation, we show how the scalar spectral index and tensor-to-scalar ratio are affected by the rates at which the scalar fields decay into radiation. We find that for certain choices of decay rates, reheating following multiple-field inflation can have a significant impact on the prediction of cosmological observables.

Energy conservation in reheating furnaces by reducing scrap and scale formation; Kuumamuokkauksen energiasaeaestoet romun maeaeraeae ja hilseilyae vaehentaemaellae

Energy Technology Data Exchange (ETDEWEB)

Kivivuori, S.; Savolainen, P.; Fredriksson, J.; Paavola, J. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Materials Processing and Powder Metallurgy

1996-12-31

The main objective of the project `Energy Savings in Reheating Furnaces by Reducing Scrap and Scale Formation` is to reduce energy consumption and environmental harms in reheating and rolling of steel. This was done by analysing the different atmospheres in reheating furnaces of the steel companies participating in this project. These atmospheres were then simulated in a laboratory furnace. Scale formation tests with different steel grades were then carried out in these atmospheres. Scale removal tests were done to some steel grades too. The results showed that lower oxygen content - as expected - decreases oxidation despite the even higher carbondioxide content in the atmosphere. Lower oxygen content may cause difficulties in scale removal. This however is highly dependent on the steel grade. Heat treatment tests showed the effect of increased temperature and furnace time on decarburization. Some energy savings was obtained in fuel consumption by optimising the operation parameters and the atmosphere steadier in different reheating furnaces. (orig.)

Energy conservation in reheating furnaces by reducing scrap and scale formation; Kuumamuokkauksen energiasaeaestoet romun maeaeraeae ja hilseilyae vaehentaemaellae

Energy Technology Data Exchange (ETDEWEB)

Kivivuori, S; Savolainen, P; Fredriksson, J; Paavola, J [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Materials Processing and Powder Metallurgy

1997-12-31

The main objective of the project `Energy Savings in Reheating Furnaces by Reducing Scrap and Scale Formation` is to reduce energy consumption and environmental harms in reheating and rolling of steel. This was done by analysing the different atmospheres in reheating furnaces of the steel companies participating in this project. These atmospheres were then simulated in a laboratory furnace. Scale formation tests with different steel grades were then carried out in these atmospheres. Scale removal tests were done to some steel grades too. The results showed that lower oxygen content - as expected - decreases oxidation despite the even higher carbondioxide content in the atmosphere. Lower oxygen content may cause difficulties in scale removal. This however is highly dependent on the steel grade. Heat treatment tests showed the effect of increased temperature and furnace time on decarburization. Some energy savings was obtained in fuel consumption by optimising the operation parameters and the atmosphere steadier in different reheating furnaces. (orig.)

Primary collector wall local temperature fluctuations in the area of water-steam phase boundary

Energy Technology Data Exchange (ETDEWEB)

Matal, O.; Klinga, J.; Simo, T. [Energovyzkum Ltd., Brno (Switzerland)

1995-12-31

A limited number of temperature sensors could be installed at the primary collector surface in the area of water - steam phase boundary. The surface temperatures as well WWER 440 steam generator process data were measured and stored for a long time and off-line evaluated. Selected results are presented in the paper. (orig.). 2 refs.

Primary collector wall local temperature fluctuations in the area of water-steam phase boundary

Energy Technology Data Exchange (ETDEWEB)

Matal, O; Klinga, J; Simo, T [Energovyzkum Ltd., Brno (Switzerland)

1996-12-31

A limited number of temperature sensors could be installed at the primary collector surface in the area of water - steam phase boundary. The surface temperatures as well WWER 440 steam generator process data were measured and stored for a long time and off-line evaluated. Selected results are presented in the paper. (orig.). 2 refs.

Detonation cell size measurements and predictions in hydrogen-air-steam mixtures at elevated temperatures

International Nuclear Information System (INIS)

Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Economos, C.

1994-01-01

The present research reports on the effect of initial mixture temperature on the experimentally measured detonation cell size for hydrogen-air-steam mixtures. Experimental and theoretical research related to combustion phenomena in hydrogen-air-steam mixtures has been ongoing for many years. However, detonation cell size data currently exists or hydrogen-air-steam mixtures up to a temperature of only 400K. Sever accident scenarios have been identified for light water reactors (LWRs) where hydrogen-air mixture temperatures in excess of 400K could be generated within containment. The experiments in this report focus on extending the cell size data base for initial mixture temperatures in excess of 400K. The experiments were carried out in a 10-cm inner-diameter, 6.1-m long heated detonation tube with a maximum operating temperature of 700K and spatial temperature uniformity of ±14K. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air initial gas mixture temperature, in the range 300K--650K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm inside-diameter test vessel, based upon the onset of single-head spin, decreased from 15 percent by hydrogen at 300K down to about 9 percent hydrogen at 650K. The one-dimensional ZND model does a very good job at predicting the overall trends in the cell size data over the range of hydrogen-air-steam mixture compositions and temperature studied in the experiments

Dynamic performances of wet turbine and steam-separator-superheater and their mathematical simulation as objects of temperature control

International Nuclear Information System (INIS)

Golovach, E.A.

1985-01-01

A mathematical model of a turbine and steam-separator-superheater (SSS) as applied to solution of the tasks of steam temperature regulaton after SSS has been developed. SSS as objects of steam temperature control are considerably less inertial, than intermediate superheaters (IS) of power units in thermal power plants, since for typical SSS and IS considered the duration of transition process according to steam temperature after SSS is 5-10 times loweA than for IS

Fluid distribution network and steam generators and method for nuclear power plant training simulator

International Nuclear Information System (INIS)

Alliston, W.H.; Johnson, S.J.; Mutafelija, B.A.

1975-01-01

A description is given of a training simulator for the real-time dynamic operation of a nuclear power plant which utilizes apparatus that includes control consoles having manual and automatic devices corresponding to simulated plant components and indicating devices for monitoring physical values in the simulated plant. A digital computer configuration is connected to the control consoles to calculate the dynamic real-time simulated operation of the plant in accordance with the simulated plant components to provide output data including data for operating the control console indicating devices. In the method and system for simulating a fluid distribution network of the power plant, such as that which includes, for example, a main steam system which distributes steam from steam generators to high pressure turbine steam reheaters, steam dump valves, and feedwater heaters, the simultaneous solution of linearized non-linear algebraic equations is used to calculate all the flows throughout the simulated system. A plurality of parallel connected steam generators that supply steam to the system are simulated individually, and include the simulation of shrink-swell characteristics

Hydrogen-rich gas production from waste plastics by pyrolysis and low-temperature steam reforming over a ruthenium catalyst

International Nuclear Information System (INIS)

Namioka, Tomoaki; Saito, Atsushi; Inoue, Yukiharu; Park, Yeongsu; Min, Tai-jin; Roh, Seon-ah; Yoshikawa, Kunio

2011-01-01

Operating conditions for low-temperature pyrolysis and steam reforming of plastics over a ruthenium catalyst were investigated. In the range studied, the highest gas and lowest coke fractions for polystyrene (PS) with a 60 g h -1 scale, continuous-feed, two-stage gasifier were obtained with a pyrolyzer temperature of 673 K, steam reforming temperature of 903 K, and weight hourly space velocity (WHSV) of 0.10 g-sample g-catalyst -1 h -1 . These operating conditions are consistent with optimum conditions reported previously for polypropylene. Our results indicate that at around 903 K, the activity of the ruthenium catalyst was high enough to minimize the difference between the rates of the steam reforming reactions of the pyrolysates from polystyrene and polypropylene. The proposed system thus has the flexibility to compensate for differences in chemical structures of municipal waste plastics. In addition, the steam reforming temperature was about 200 K lower than the temperature used in a conventional Ni-catalyzed process for the production of hydrogen. Low-temperature steam reforming allows for lower thermal input to the steam reformer, which results in an increase in thermal efficiency in the proposed process employing a Ru catalyst. Because low-temperature steam reforming can be also expected to reduce thermal degradation rates of the catalyst, the pyrolysis-steam reforming process with a Ru catalyst has the potential for use in small-scale production of hydrogen-rich gas from waste plastics that can be used for power generation.

Fabrication of cathode supported tubular solid oxide electrolysis cell for high temperature steam electrolysis

Energy Technology Data Exchange (ETDEWEB)

Shao, Le; Wang, Shaorong; Qian, Jiqin; Xue, Yanjie; Liu, Renzhu

2011-01-15

In recent years, hydrogen has been identified as a potential alternative fuel and energy carrier for the future energy supply. Water electrolysis is one of the important hydrogen production technologies which do not emit carbon dioxide. High temperature steam electrolysis (HTSE) consumes even less electrical energy than low temperature water electrolysis. Theoretically, HTSE using solid oxide electrolysis cells (SOEC) can efficiently utilize renewable energy to produce hydrogen, and it is also possible to operate the SOEC in reverse mode as the solid oxide fuel cell (SOFC) to produce electricity. Tubular SOFC have been widely investigated. In this study, tubular solid oxide cells were fabricated by dip-coating and cosintering techniques. In SOEC mode, results suggested that steam ratio had a strong impact on the performance of the tubular cell; the tubular SOEC preferred to be operated at high steam ratio in order to avoid concentration polarization. The microstructure of the tubular SOEC should therefore be optimized for high temperature steam electrolysis.

Steam Distillation with Induction Heating System: Analysis of Kaffir Lime Oil Compound and Production Yield at Various Temperatures

International Nuclear Information System (INIS)

Zuraida Muhammad; Zakiah Mohd Yusoff; Mohd Noor Nasriq Nordin

2013-01-01

The steam temperature during the extraction process has a great influence on the essential oil quality. .This study was conducted to analyze the compound of kaffir-lime oil during extracting at different steam temperature using GC-MS analysis. The extraction was carried out by using steam distillation based on induction heating system at different extraction temperature such as 90, 95 and 100 degree Celsius, the power of the induction heating system is fixed at 1.6 kW. Increment of the steam temperature will increase the oil yield. In terms of oil composition, extraction at lower temperature resulted high concentration for four marker compounds of kaffir-lime oil which are α-pinene, sabinene, limonene, β-pinene. (author)

High-temperature steam oxidation kinetics of the E110G cladding alloy

International Nuclear Information System (INIS)

Király, Márton; Kulacsy, Katalin; Hózer, Zoltán; Perez-Feró, Erzsébet; Novotny, Tamás

2016-01-01

In the course of recent years, several experiments were performed at MTA EK (Centre for Energy Research, Hungarian Academy of Sciences) on the isothermal high-temperature oxidation of the improved Russian cladding alloy E110G in steam/argon atmosphere. Using these data and designing additional supporting experiments, the oxidation kinetics of the E110G alloy was investigated in a wide temperature range, between 600 °C and 1200 °C. For short durations (below 500 s) or high temperatures (above 1065 °C) the oxidation kinetics was found to follow a square-root-of-time dependence, while for longer durations and in the intermediate temperature range (800–1000 °C) it was found to approach a cube-root-of-time dependence rather than a square-root one. Based on the results a new best-estimate and a conservative oxidation kinetics model were created. - Highlights: • Steam oxidation kinetics of E110G was studied at MTA EK based on old and new data. • New best-estimate and conservative steam oxidation kinetics were proposed for E110G. • The exponent of oxidation time changed depending on oxidation temperature. • A simple exponential curve was used instead of Arrhenius-type curve for the factor.

Reheat cracking susceptibility of P23 (7CrWVMoNb9-6) steel welds made using matching and mis-matching filler metals

Energy Technology Data Exchange (ETDEWEB)

Nevasmaa, Pekka; Salonen, Jorma; Auerkari, Pertti; Rantala, Juhani; Holmstroem, Stefan [VTT Technical Research Centre of Finland, Espoo (Finland)

2010-07-01

Reheat cracking sensitivity of 7CrWVMoNb9-6 (P23) thick-section multipass welds has been investigated by Gleeble simulation, mechanical testing, fractography and metallography. The results demonstrate that the experimental weld metal made using a high-Nb-W-Ti-B type filler metal was sensitive to reheat cracking, with a reduction of area no more than 2-3% in the BWI reheat cracking (RC) test. Welds made using a high-W -low-Ti type filler metal with Nb content similar to the parent steel, as well as welds make using a Ni-Nb-Ti-free-(W-free) type filler metal with the chemical composition closer to P24 grade material, were more ductile and crack-resistant, though with reduced cross-weld creep strength. Fractography of RC test specimens showed evidence of pronounced localisation of damage at the prior austenite grain boundaries of the thermally reheated, experimental P23 weld metal. The reheat cracking susceptibility of the less ductile weld metal was apparently related both to the chemical composition (higher B, Nb and Ti content) and sub-structural features of the coarse-grained reheated weld metal microstructure. Appropriate single- and multi-cycle thermal Gleeble simulations to produce representative HAY and reheated weld metal microstructures (as function of peak temperature), in conjunction with the BWI RC test were successfully applied to characterise the reheat cracking sensitivity of the candidate weld metals and parent steel HAZ. (orig.)

Design of large steam turbines for PWR power stations

International Nuclear Information System (INIS)

Hobson, G.

1984-01-01

The authors review the thermodynamic cycle requirements for use with pressurized-water reactors, outline the way thermal efficiency is maximized, and discuss the special nature of the wet-steam cycle associated with turbines for this type of reactor. Machine and cycle parameters are optimized to achieve high thermal efficiency, particular attention being given to arrangements for water separation and steam reheating and to provisions for feedwater heating. Principles and details of mechanical design are considered for a range both of full-speed turbines running at 3000 rev/min on 50 Hz systems and of half-speed turbines running at 1800 rev/min on 60 Hz systems. The importance of service experience with nuclear wet-stream turbines, and its relevance to the design of modern turbines for PWR applications, is discussed. (author)

Proposal of a combined heat and power plant hybridized with regeneration organic Rankine cycle: Energy-Exergy evaluation

International Nuclear Information System (INIS)

Anvari, Simin; Jafarmadar, Samad; Khalilarya, Shahram

2016-01-01

Highlights: • A new thermodynamic cogeneration system is proposed. • Energy and exergy analysis of the considered cycle were performed. • An enhancement of 2.6% in exergy efficiency compared to that of baseline cycle. - Abstract: Among Rankine cycles (simple, reheat and regeneration), regeneration organic Rankine cycle demonstrates higher efficiencies compared to other cases. Consequently, in the present work a regeneration organic Rankine cycle has been utilized to recuperate gas turbine’s heat using heat recovery steam generator. At first, this cogeneration system was subjected to energy and exergy analysis and the obtained results were compared with that of investigated cogeneration found in literature (a cogeneration system in which a reheat organic Rankine cycle for heat recuperation of gas turbine cycle was used with the aid of heat recovery steam generator). Results indicated that the first and second thermodynamic efficiencies in present cycle utilizing regeneration cycle instead of reheat cycle has increased 2.62% and 2.6%, respectively. In addition, the effect of thermodynamic parameters such as combustion chamber’s inlet temperature, gas turbine inlet temperature, evaporator and condenser temperature on the energetic and exergetic efficiencies of gas turbine-heat recovery steam generator cycle and gas turbine-heat recovery steam generator cycle with regeneration organic Rankine cycle was surveyed. Besides, parametric analysis shows that as gas turbine and combustion chamber inlet temperatures increase, energetic and exergetic efficiencies tend to increase. Moreover, once condenser and evaporator temperature raise, a slight decrement in energetic and exergetic efficiency is expected.

Thermal analysis of heat and power plant with high temperature reactor and intermediate steam cycle

Directory of Open Access Journals (Sweden)

Fic Adam

2015-03-01

Full Text Available Thermal analysis of a heat and power plant with a high temperature gas cooled nuclear reactor is presented. The main aim of the considered system is to supply a technological process with the heat at suitably high temperature level. The considered unit is also used to produce electricity. The high temperature helium cooled nuclear reactor is the primary heat source in the system, which consists of: the reactor cooling cycle, the steam cycle and the gas heat pump cycle. Helium used as a carrier in the first cycle (classic Brayton cycle, which includes the reactor, delivers heat in a steam generator to produce superheated steam with required parameters of the intermediate cycle. The intermediate cycle is provided to transport energy from the reactor installation to the process installation requiring a high temperature heat. The distance between reactor and the process installation is assumed short and negligable, or alternatively equal to 1 km in the analysis. The system is also equipped with a high temperature argon heat pump to obtain the temperature level of a heat carrier required by a high temperature process. Thus, the steam of the intermediate cycle supplies a lower heat exchanger of the heat pump, a process heat exchanger at the medium temperature level and a classical steam turbine system (Rankine cycle. The main purpose of the research was to evaluate the effectiveness of the system considered and to assess whether such a three cycle cogeneration system is reasonable. Multivariant calculations have been carried out employing the developed mathematical model. The results have been presented in a form of the energy efficiency and exergy efficiency of the system as a function of the temperature drop in the high temperature process heat exchanger and the reactor pressure.

High-temperature hydrogen-air-steam detonation experiments in the BNL small-scale development apparatus

International Nuclear Information System (INIS)

Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Economos, C.; Finfrock, C.; Gerlach, L.; Sato, K.

1994-01-01

The Small-Scale Development Apparatus (SSDA) was constructed to provide a preliminary set of experimental data to characterize the effect of temperature on the ability of hydrogen-air-steam-mixtures to undergo detonations and, equally important, to support design of the larger-scale High-Temperature Combustion Facility (HTCF) by providing a test bed for solution of a number of high-temperature design and operational problems. The SSDA, the central element of which is 10-cm inside diameter, 6.1-m long tubular test vessel designed to permit detonation experiments at temperatures up to 700K, was employed to study self-sustained detonations in gaseous mixtures of hydrogen, air, and steam at temperature between 300K and 650K at a fixed pressure of 0.1 MPa. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air gas mixture temperature, in the range 300K to 650K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The one-dimensional ZND model does a very good job at predicting the overall trends in the cell size data over the range of hydrogen-air-steam mixture compositions and temperature studied in the experiments. Experiments were conducted to measure the rate of hydrogen oxidation in the absence of ignition sources at temperatures of 500K and 650K, for hydrogen-air mixtures of 15% and 50%, and for a mixture of equimolar hydrogen-air and 30% steam at 650K. The rate of hydrogen oxidation was found to be significant at 650K. Reduction of hydrogen concentration by chemical reaction from 50 to 44% hydrogen, and from 15 to 11% hydrogen, were observed on a time frame of minutes. The DeSoete rate equation predicts the 50% experiment very well, but greatly underestimates the reaction rate of the lean mixtures

Observational status of Tachyon Natural Inflation and reheating

Science.gov (United States)

Rashidi, Narges; Nozari, Kourosh; Grøn, Øyvind

2018-05-01

We study observational viability of Natural Inflation with a tachyon field as inflaton. By obtaining the main perturbation parameters in this model, we perform a numerical analysis on the parameter space of the model and in confrontation with 68% and 95% CL regions of Planck2015 data. By adopting a warped background geometry, we find some new constraints on the width of the potential in terms of its height and the warp factor. We show that the Tachyon Natural Inflation in the large width limit recovers the tachyon model with a phi2 potential which is consistent with Planck2015 observational data. Then we focus on the reheating era after inflation by treating the number of e-folds, temperature and the effective equation of state parameter in this era. Since it is likely that the value of the effective equation of state parameter during the reheating era to be in the range 0Inflation model. In particular, we show that a prediction of this model is r<=8/3 δns, where δns is the scalar spectral tilt, δns=1‑ns. In this regard, given that from the Planck2015 data we have δns=0.032 (corresponding to ns=0.968), we get r<= 0.085.

Creep of Sylramic-iBN Fiber Tows at Elevated Temperature in Air and in Silicic Acid-Saturated Steam

Science.gov (United States)

2015-06-01

CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM ...protection in the United States. AFIT-ENY-15-J-46 CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM ...DISTRIBUTION UNLIMITED. AFIT-ENY-15-J-46 CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM

Nuclear power plant

International Nuclear Information System (INIS)

Schabert, H.P.

1976-01-01

A nuclear power plant is described which includes a steam generator supplied via an input inlet with feedwater heated by reactor coolant to generate steam, the steam being conducted to a steam engine having a high pressure stage to which the steam is supplied, and which exhausts the steam through a reheater to a low pressure stage. The reheater is a heat exchanger requiring a supply of hot fluid. To avoid the extra load that would be placed on the steam generator by using a portion of its steam output as such heating fluid, a portion of the water in the steam generator is removed and passed through the reheater, this water having received at least adequate heating in the steam generator to make the reheater effective, but not at the time of its removal being in a boiling condition

Study of the Apparent Kinetics of Biomass Gasification Using High-Temperature Steam

Energy Technology Data Exchange (ETDEWEB)

Alevanau, Aliaksandr

2010-10-15

Among the latest achievements in gasification technology, one may list the development of a method to preheat gasification agents using switched ceramic honey combs. The best output from this technology is achieved with use of water steam as a gasification agent, which is heated up to 1600 deg C. The application of these temperatures with steam as a gasification agent provides a cleaner syngas (no nitrogen from air, cracked tars) and the ash melts into easily utilised glass-like sludge. High hydrogen content in output gas is also favourable for end-user applications.Among the other advantages of this technology is the presumable application of fixed-bed-type reactors fed by separately produced and preheated steam. This construction assumes relatively high steam flow rates to deliver the heat needed for endothermic reactions involving biomass. The biomass is to be heated uniformly and evenly in the volume of the whole reactor, providing easier and simpler control and operation in comparison to other types of reactors. To provide potential constructors and exploiters of these reactors with the kinetic data needed for the calculations of vital parameters for both reactor construction and exploitation, basic experimental research of high-temperature steam gasification of four types of industrially produced biomass has been conducted.Kinetic data have been obtained for straw and wood pellets, wood-chip charcoal and compressed charcoal of mixed origin

Brown Boveri moves to fourth generation MSRs [moisture separator reheaters

International Nuclear Information System (INIS)

Boeckh, P. von

1987-01-01

The fourth, space saving, generation of moisture separator reheaters from Brown Boveri and Cie (BBC) consists of two types of high velocity moisture separators, 'Mops' and 'Scrups', and the small size reheater, 'Road' . The design of the unit is described, together with operational experience. (author)

An investigation of reheat cracking in the weld heat affected zone of type 347 stainless steel

Science.gov (United States)

Phung-On, Isaratat

2007-12-01

Reheat cracking has been a persistent problem for welding of many alloys such as the stabilized stainless steels: Types 321 and 347 as well as Cr-Mo-V steels. Similar problem occurs in Ni-base superalloys termed "strain-age cracking". Cracking occurs during the post weld heat treatment. The HAZ is the most susceptible area due to metallurgical reactions in solid state during both heating and cooling thermal cycle. Many investigations have been conducted to understand the RHC mechanism. There is still no comprehensive mechanism to explain its underlying mechanism. In this study, there were two proposed cracking mechanisms. The first is the formation of a PFZ resulting in local weakening and strain localization. The second is the creep-like grain boundary sliding that causes microvoid formation at the grain boundaries and the triple point junctions. Cracking occurs due to the coalescence of the microvoids that form. In this study, stabilized grade stainless steel, Type 347, was selected for investigation of reheat cracking mechanism due to the simplicity of its microstructure and understanding of its metallurgical behavior. The Gleeble(TM) 3800 system was employed due to its capability for precise control of both thermal and mechanical simulation. Cylindrical samples were subjected to thermal cycles for the HAZ simulation followed by PWHT as the reheat cracking test. "Susceptibility C-curves" were plotted as a function of PWHT temperatures and time to failure at applied stress levels of 70% and 80% yield strength. These C-curves show the possible relationship of the reheat cracking susceptibility and carbide precipitation behavior. To identify the mechanism, the sample shape was modified containing two flat surfaces at the center section. These flat surfaces were electro-polished and subjected to the HAZ simulation followed by the placement of the micro-indentation arrays. Then, the reheat cracking test was performed. The cracking mechanism was identified by tracing

High-temperature gas-cooled reactor steam cycle/cogeneration application study update

International Nuclear Information System (INIS)

1981-09-01

Since publication of a report on the application of a High Temperature Gas-Cooled Reactor Steam Cycle/Cogeneration (HTGR-SC/C) plant in December of 1980, progress has continued on application related activities. In particular, a reference plant and an application identification effort has been performed, a variable cogeneration cycle balance-of-plant design was developed and an updated economic analysis was prepared. A reference HTGR-SC/C plant size of 2240 MW(t) was selected, primarily on the basis of 2240 MW(t) being in the mid-range of anticipated application needs and the availability of the design data from the 2240 MW(t) Steam Cycle/Electric generation plant design. A variable cogeneration cycle plant design was developed having the capability of operating at a range of process steam loads between the reference design load (full cogeneration) and the no process steam load condition

Investigation of the high temperature steam oxidation of Zircaloy 4 cladding tubes

International Nuclear Information System (INIS)

Leistikow, S.; Berg, H. v.; Kraft, R.; Pott, E.; Schanz, G.

1979-01-01

Also for the ORNL Zircaloy 4 cladding material, an intermediate decrease of the proportion of the ZrO 2 /α-phase layer was found, followed by an drastic increase when the breakaway of the ZrO 2 -scale occurred. Other reasons for small divergencies were evaluated, for instance temperature and time measurements, metallographic evaluation of layer thicknesses, consequences of one-sided (ORNL) and double-sided (KfK) oxidation. The so-called anomalous effect of steam oxidation during temperature transients was reproduced qualitatively and-in case that a reduced gain of oxygen was observed-explained by the predominant existence of the monoclinic oxide phase. The creep-rupture tests below 800 0 C showed a moderate prolongation of time-to-rupture when the tests were performed in steam (or after preoxidation in steam) instead of argon. Also slightly reduced maximum circumferential strain could be measured. (orig./RW) [de

Economic evaluation of the steam-cycle high-temperature gas-cooled reactor

International Nuclear Information System (INIS)

1983-07-01

The High Temperature Gas-Cooled Reactor is unique among current nuclear technologies in its ability to generate energy in temperature regimes previously limited to fossil fuels. As a result, it can offer commercial benefits in the production of electricity, and at the same time, expand the role of nuclear energy to the production of process heat. This report provides an evaluation of the HTGR-Steam Cycle (SC) system for the production of baseloaded electricity, as well as cogenerated electricity and process steam. In each case the HTGR-SC system has been evaluated against appropriate competing technologies. The computer code which was developed for this evaluation can be used to present the analyses on a cost of production or cash flow basis; thereby, presenting consistent results to a utility, interested in production costs, or an industrial steam user or third party investor, interested in returns on equity. Basically, there are two economic evaluation methodologies which can be used in the analysis of a project: (1) minimum revenue requirements, and (2) discounted cash flow

Preliminary design study of removable integral steam generator units of the multiple helically wound tube type for a 1250 MW(th) H.T.G.C. reactor

International Nuclear Information System (INIS)

Gilli, P.V.; Fritz, K.; Lippitsch, J.; Sandri, A.H.; Weiss, B.

1965-11-01

The possibilities of designing a multiple steam generator for a 1250 MW(th) High Temperature Gas-Cooled Reactor, consisting of 18 units which are able to pass through 5 ft diam. holes in the integral prestressed concrete pressure vessel are investigated. A lay-out and design with bundles of multi-start helical tubes is evolved, particular attention being paid to the questions of tube blanking and removal of the unit, and of selection of materials for superheater and reheater tubes. Thermal and stress calculations have been carried out, using the Waagner-Biro Computer Code ADURHELIX. (author)

Reheating for closed string inflation

Energy Technology Data Exchange (ETDEWEB)

Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Mazumdar, Anupam [Lancaster Univ. (United Kingdom). Physics Dept.; Copenhagen Univ. (Denmark). Niels Bohr Institute

2010-05-15

We point out some of the outstanding challenges for embedding inflationary cosmology within string theory studying the process of reheating for models where the inflaton is a closed string mode parameterising the size of an internal cycle of the compactification manifold. A realistic model of inflation must explain the tiny perturbations in the cosmic microwave background radiation and also how to excite the ordinary matter degrees of freedom after inflation, required for the success of Big Bang Nucleosynthesis. We study these issues focusing on two promising inflationary models embedded in LARGE volume type IIB flux compactifications. We show that phenomenological requirements and consistency of the effective field theory treatment imply the presence at low energies of a hidden sector together with a visible sector, where the Minimal Supersymmetric Standard Model fields are residing. A detailed calculation of the inflaton coupling to the fields of the hidden sector, visible sector, and moduli sector, reveals that the inflaton fails to excite primarily the visible sector fields, instead hidden sector fields are excited copiously after the end of inflation. This sets severe constraints on hidden sector model building where the most promising scenario emerges as a pure N=1 SYM theory, forbidding the kinematical decay of the inflaton to the hidden sector. In this case it is possible to reheat the Universe with the visible degrees of freedom even though in some cases we discover a new tension between TeV scale SUSY and reheating on top of the well-known tension between TeV scale SUSY and inflation. (orig.)

Reheating for closed string inflation

International Nuclear Information System (INIS)

Cicoli, Michele; Mazumdar, Anupam; Copenhagen Univ.

2010-05-01

We point out some of the outstanding challenges for embedding inflationary cosmology within string theory studying the process of reheating for models where the inflaton is a closed string mode parameterising the size of an internal cycle of the compactification manifold. A realistic model of inflation must explain the tiny perturbations in the cosmic microwave background radiation and also how to excite the ordinary matter degrees of freedom after inflation, required for the success of Big Bang Nucleosynthesis. We study these issues focusing on two promising inflationary models embedded in LARGE volume type IIB flux compactifications. We show that phenomenological requirements and consistency of the effective field theory treatment imply the presence at low energies of a hidden sector together with a visible sector, where the Minimal Supersymmetric Standard Model fields are residing. A detailed calculation of the inflaton coupling to the fields of the hidden sector, visible sector, and moduli sector, reveals that the inflaton fails to excite primarily the visible sector fields, instead hidden sector fields are excited copiously after the end of inflation. This sets severe constraints on hidden sector model building where the most promising scenario emerges as a pure N=1 SYM theory, forbidding the kinematical decay of the inflaton to the hidden sector. In this case it is possible to reheat the Universe with the visible degrees of freedom even though in some cases we discover a new tension between TeV scale SUSY and reheating on top of the well-known tension between TeV scale SUSY and inflation. (orig.)

Calculation of a steam generating tube stressed state under temperature oscillations in burnout zone

International Nuclear Information System (INIS)

Vorob'ev, V.A.; Loshchinin, V.M.; Remizov, O.V.

1982-01-01

The technique for evaluating the steam generating tube stressed state under the wall temperature oscillations in the burnout zone is described. The technique is based on analytical solutions for transfer functions connecting the amplitude of surface temperature oscillation with the amplitude and frequency of heat transfer coefficient oscillation and amplitude of thermoelastic stress oscillation with that of temperature oscillation. The results of calculations according to considered technique are compared with that of the problem numerical solution. The conclusion is made that the technique under consideration may be applied for evaluation of steam generator evaporating tube lifetime [ru

Parametric Amplification of Gravitational Fluctuations during Reheating

International Nuclear Information System (INIS)

Finelli, F.; Brandenberger, R.; Finelli, F.

1999-01-01

Cosmological perturbations can undergo amplification by parametric resonance during preheating even on scales larger than the Hubble radius, without violating causality. A unified description of gravitational and matter fluctuations is crucial to determine the strength of the instability. To extract specific signatures of the oscillating inflaton field during reheating, it is essential to focus on a variable describing metric fluctuations which is constant in the standard analyses of inflation. For a massive inflaton without self-coupling, we find no additional growth of superhorizon modes during reheating beyond the usual predictions. For a massless self-coupled inflaton, there is a sub-Hubble scale resonance. copyright 1999 The American Physical Society

Mechanical properties of Ni-base superalloys in high temperature steam environments

International Nuclear Information System (INIS)

Jang, Changheui; Kim, Donghoon; Sah, Injin; Lee, Ho Jung

2015-01-01

The effects of environmental damages on the mechanical properties of Ni-base superalloys, Alloy 617 and Haynes 230, were evaluated for VHTR-HTSE applications. Tensile tests were carried out at room temperature after ageing at 900 deg. C in vacuum, steam, and steam + 20 vol.% H2 environments up to 3 000 h. Also, creep rupture test were performed in air, steam, and steam + 20 vol.% H2 environments. The degradations such as oxidation, decarburization, and redistribution of carbides were studied in view of the interaction of materials with the environment. During the long-term ageing at 900 deg. C in vacuum, secondary phases such as M23C6 and M6C were precipitated and coarsened, which caused increase in tensile strength and decrease in ductility. For the specimens aged in steam environments, surface and internal oxides acted as preferential sites for crack initiation and consequently, decreased the tensile and creep strength. Also, the formation of decarburization region resulted in glide plane failure during tensile test and reduction in creep rupture life due to grain boundary migration and recrystallisation. During creep tests, tensile stress caused the crack and void formation in oxide layer. Consequently, fast diffusion of oxidant occurred and environmental damage were accelerated. Among the test conditions, such environmental damage was much severe in steam environments. (authors)

A three-dimensional laboratory steam injection model allowing in situ saturation measurements. [Comparing steam injection and steam foam injection with nitrogen and without nitrogen

Energy Technology Data Exchange (ETDEWEB)

Demiral, B.M.R.; Pettit, P.A.; Castanier, L.M.; Brigham, W.E.

1992-08-01

The CT imaging technique together with temperature and pressure measurements were used to follow the steam propagation during steam and steam foam injection experiments in a three dimensional laboratory steam injection model. The advantages and disadvantages of different geometries were examined to find out which could best represent radial and gravity override flows and also fit the dimensions of the scanning field of the CT scanner. During experiments, steam was injected continuously at a constant rate into the water saturated model and CT scans were taken at six different cross sections of the model. Pressure and temperature data were collected with time at three different levels in the model. During steam injection experiments, the saturations obtained by CT matched well with the temperature data. That is, the steam override as observed by temperature data was also clearly seen on the CT pictures. During the runs where foam was present, the saturation distributions obtained from CT pictures showed a piston like displacement. However, the temperature distributions were different depending on the type of steam foam process used. The results clearly show that the pressure/temperature data alone are not sufficient to study steam foam in the presence of non-condensible gas.

Temperature condition in decreasing heat transfer zone for NPP steam generators

International Nuclear Information System (INIS)

Kudryavtsev, I.S.; Paskar', B.L.; Sudakov, A.V.

1985-01-01

An experimental set-up is described and the results of temperature pulsation investigation are presented for coil steam generating channel surfaces of the NPP helium and sodium cooled HTGR. The investigations are carried out at the heat flux density of 350-900 kW/m 3 , the mass rate of 350-2000 kg/(m 2 Xs), the pressUre of 15 MPa. Temperature pulsations occur due to instability of heat transfer in the near-wall region. The results show that the critical region of burnout has a local character. Pulsation dependences on operating conditions are given. The required resource for the steam generating channel may be provided by chosing the ratio of heat flux to the mass rate, the ratio being equal to 0.5 kJ/kg for the channel with the internal diameter of 19 mm, made of the 12Kh2M steel, the wall thickness of 3 mm. In this case the maximum span of temperature pulsations doesn't exceed 25-30 K

Reheating via Gravitational Particle Production in Simple Models of Quintessence or ΛCDM Inflation

Directory of Open Access Journals (Sweden)

Jaume de Haro

2017-11-01

Full Text Available We have tested some simple Λ CDM (the same test is also valid for quintessence inflation models, imposing that they match with the recent observational data provided by the BICEP and Planck’s team and leading to a reheating temperature, which is obtained via gravitational particle production after inflation, supporting the nucleosynthesis success.

Calculations of Inflaton Decays and Reheating: with Applications to No-Scale Inflation Models

CERN Document Server

Ellis, John; Nanopoulos, Dimitri V; Olive, Keith A

2015-01-01

We discuss inflaton decays and reheating in no-scale Starobinsky-like models of inflation, calculating the effective equation-of-state parameter, $w$, during the epoch of inflaton decay, the reheating temperature, $T_{\\rm reh}$, and the number of inflationary e-folds, $N_*$, comparing analytical approximations with numerical calculations. We then illustrate these results with applications to models based on no-scale supergravity and motivated by generic string compactifications, including scenarios where the inflaton is identified as an untwisted-sector matter field with direct Yukawa couplings to MSSM fields, and where the inflaton decays via gravitational-strength interactions. Finally, we use our results to discuss the constraints on these models imposed by present measurements of the scalar spectral index $n_s$ and the tensor-to-scalar perturbation ratio $r$, converting them into constraints on $N_*$, the inflaton decay rate and other parameters of specific no-scale inflationary models.

Effects of Re-heating Tissue Samples to Core Body Temperature on High-Velocity Ballistic Projectile-tissue Interactions.

Science.gov (United States)

Humphrey, Caitlin; Henneberg, Maciej; Wachsberger, Christian; Maiden, Nicholas; Kumaratilake, Jaliya

2017-11-01

Damage produced by high-speed projectiles on organic tissue will depend on the physical properties of the tissues. Conditioning organic tissue samples to human core body temperature (37°C) prior to conducting ballistic experiments enables their behavior to closely mimic that of living tissues. To minimize autolytic changes after death, the tissues are refrigerated soon after their removal from the body and re-heated to 37°C prior to testing. This research investigates whether heating 50-mm-cube samples of porcine liver, kidney, and heart to 37°C for varying durations (maximum 7 h) can affect the penetration response of a high-speed, steel sphere projectile. Longer conditioning times for heart and liver resulted in a slight loss of velocity/energy of the projectile, but the reverse effect occurred for the kidney. Possible reasons for these trends include autolytic changes causing softening (heart and liver) and dehydration causing an increase in density (kidney). © 2017 American Academy of Forensic Sciences.

High temperature technological heat exchangers and steam generators with helical coil assembly tube bundle

International Nuclear Information System (INIS)

Korotaev, O.J.; Mizonov, N.V.; Nikolaevsky, V.B.; Nazarov, E.K.

1990-01-01

Analysis of thermal hydraulics characteristics of nuclear steam generators with different tube bundle arrangements and waste heat boilers for ammonia production units was performed on the basis of operating experience results and research and development data. The present report involves the obtained information. The estimations of steam generator performances and repair-ability are given. The significant temperature profile of the primary and secondary coolant flows are attributed to all steam generator designs. The intermediate mixing is found to be an effective means of temperature profile overcoming. At present the only means to provide an effective mixing in heat exchangers of the following types: straight tubes, field tubes, platen tubes and multibank helical coil tubes (with complicated bend distribution along their length) are section arrangements in series in conjunction with forced and natural mixing in connecting lines. Development of the unificated system from mini helical coil assemblies allows to design and manufacture heat exchangers and steam generators within the wide range of operating conditions without additional expenses on the research and development work

Tube sheet design for PFBR steam generator

International Nuclear Information System (INIS)

Chellapandi, P.; Chetal, S.C.; Bhoje, S.B.

1991-01-01

Top and bottom tube sheets of PFBR Steam Generators have been analysed with 3D and axisymmetric models using CASTEM Programs. Analysis indicates that the effects of piping reactions at the inlet/outlet nozzles on the primary stresses in the tube sheets are negligible and the asymmetricity of the deformation pattern introduced in the tube sheet by the presence of inlet/outlet and manhole nozzles is insignificant. The minimum tube sheet thicknesses for evaporator and reheater are 135 mm and 75 mm respectively. Further analysis has indicated the minimum fillet radius at the junction of tube sheet and dished end should be 20 mm. Simplified methodology has been developed to arrive at the number of thermal baffles required to protect the tube sheet against fatigue damage due to thermal transient. This method has been applied to PFBR steam generators to determine the required number of thermal baffles. For protecting the bottom tube sheet of evaporator against the thermal shock due to feed water and secondary pump trip, one thermal shield is found to be sufficient. Further analysis is required to decide upon the actual number to take care of the severe thermal transient, following the event of sudden dumping of water/steam, immediately after the sodium-water reaction. (author)

Optimising residual stresses at a repair in a steam header to tubeplate weld

International Nuclear Information System (INIS)

Soanes, T.P.T.; Bell, W.; Vibert, A.J.

2005-01-01

Following the discovery of incorrect weld metal in the steam side shell to tubeplate weld in a type 316H stainless steel superheater steam header, a repair strategy had to be determined. The strategy adopted was to remove the incorrect weld material, which extended around the full circumference, by machining from the inside of the header, followed by rewelding from the inside using an automatic welding process and localised post-weld heat treatment. Due to concern over potential reheat cracking of the repair after return to service, a considerable amount of residual stress modelling was carried out to support the development and optimisation of a successful repair and heat treatment strategy and thus underwrite the safety case for return to service

Dark matter from gravitational particle production at reheating

Energy Technology Data Exchange (ETDEWEB)

Markkanen, Tommi [Department of Physics, King' s College London, Strand, London WC2R 2LS (United Kingdom); Nurmi, Sami, E-mail: tommi.markkanen@kcl.ac.uk, E-mail: sami.t.nurmi@jyu.fi [Department of Physics, University of Jyväskylä, P.O. Box 35, FI-40014 University of Jyväskylä (Finland)

2017-02-01

We show that curvature induced particle production at reheating generates adiabatic dark matter if there are non-minimally coupled spectator scalars weakly coupled to visible matter. The observed dark matter abundance implies an upper bound on spectator masses m and non-minimal coupling values ξ. For example, assuming quadratic inflation, instant reheating and a single spectator scalar with only gravitational couplings, the observed dark matter abundance is obtained for m ∼ 0.1 GeV and ξ ∼ 1. Larger mass and coupling values of the spectator are excluded as they would lead to overproduction of dark matter.

Dark matter from gravitational particle production at reheating

International Nuclear Information System (INIS)

Markkanen, Tommi; Nurmi, Sami

2017-01-01

We show that curvature induced particle production at reheating generates adiabatic dark matter if there are non-minimally coupled spectator scalars weakly coupled to visible matter. The observed dark matter abundance implies an upper bound on spectator masses m and non-minimal coupling values ξ. For example, assuming quadratic inflation, instant reheating and a single spectator scalar with only gravitational couplings, the observed dark matter abundance is obtained for m ∼ 0.1 GeV and ξ ∼ 1. Larger mass and coupling values of the spectator are excluded as they would lead to overproduction of dark matter.

Steam sterilization does not require saturated steam

NARCIS (Netherlands)

van Doornmalen Gomez Hoyos, J. P.C.M.; Paunovic, A.; Kopinga, K.

2017-01-01

The most commonly applied method to sterilize re-usable medical devices in hospitals is steam sterilization. The essential conditions for steam sterilization are derived from sterilization in water. Microbiological experiments in aqueous solutions have been used to calculate various time–temperature

Temperature conditions in an LMFBR power plant from primary sodium to steam circuits

International Nuclear Information System (INIS)

Aubert, M.; Chaumont, M.; Mougniot, M.; Recolin, M.; Acket, M.

1978-01-01

The subject is discussed under the headings: introduction; method and procedure (optimization program, review of process constraints - fuel limitations, turbine, steam generators, parameter selection - core parameters, temperatures, counterbalancing forces affecting temperatures); optimum values of parameters, with effect on costs; conclusion, (U.K.)

An Improved Steam Injection Model with the Consideration of Steam Override

OpenAIRE

He , Congge; Mu , Longxin; Fan , Zifei; Xu , Anzhu; Zeng , Baoquan; Ji , Zhongyuan; Han , Haishui

2017-01-01

International audience; The great difference in density between steam and liquid during wet steam injection always results in steam override, that is, steam gathers on the top of the pay zone. In this article, the equation for steam override coefficient was firstly established based on van Lookeren’s steam override theory and then radius of steam zone and hot fluid zone were derived according to a more realistic temperature distribution and an energy balance in the pay zone. On this basis, th...

Radiation heat transfer within and from high temperature plumes composed of steam and molten nuclear debris

International Nuclear Information System (INIS)

Condiff, D.W.

1987-03-01

The Differential Approximation of Radiation Heat Transfer which includes anisotropic scattering is formulated to account for multiple source and temperature fields of multiphase flow. The formulation is applied to a simplified model of a plume consisting of high temperature emissive particles in steam at parametrically variable lower temperatures. Parametric model calculations are presented which account for spectral emission and absorption by steam using a band approximation as well as emission, absorption and scattering by the debris. The results are found to be far more sensitive to emission properties of individual particles, than to their scattering properties at high temperatures

Design of the steam reformer for the HTR-10 high temperature process heat application

International Nuclear Information System (INIS)

Ju Huaiming; Xu Yuanhui; Jia Haijun

2000-01-01

The 10 MW High Temperature Reactor Test Module (HTR-10) is being constructed now and planned to be operational in 2000. One of the objectives is to develop the high temperature process heat application. The methane steam reformer is one of the key-facilities for the nuclear process heat application system. The paper describes the conceptual design of the HTR-10 Steam Reformer with He heating, and the design optimization computer code. It can be used to perform sensitivity analysis for parameters, and to improve the design. Principal parameters and construction features of the HTR-10 reformer heated by He are introduced. (author)

Future steam generator designs. Single wall designs

International Nuclear Information System (INIS)

Hayden, O.

1978-01-01

The easily removable 'U' tube design style adopted in the UK for the existing PFR Steam Generators, the Replacement Units now in production and for the future CDFR, gives the operator an extremely valuable option in the event of a water/steam leak occurring inside the Steam Generator. He can choose to shut-down, attempt to find the leak, assess damage, repair, revalidate and return to service in situ, or he can elect to remove the defect unit and replace with a 'proven' spare before returning the circuit to power. With the latter approach the resultant outage time is a known entity of about two weeks. If a repair is attempted in situ, predictions of outage time can become a matter of guesswork since one has no 'guaranteed' method of leak location and the assessment of secondary damage may be very time consuming, depending on the size and type of the original leak together with the particular design style of the Steam Generator. A further significant advantage of the removable 'U' tube design concept is that periodic interchanging of bundles with a spare enables routine chemical cleaning and thorough scheduled tube inspections, with specimen tube sample removal if required for monitoring purposes. If necessary, bundle decontamination can be undertaken to assess engineering deterioration to various degrees of thoroughness ranging from 100% equivalent factory final assembly inspection, to partial decontamination operating via a glovebox type of maintenance bag arrangement, examining local points of both shell and tube areas of the bundle. Many lessons from the last five years' experience of PFR will be incorporated into the design of the CDFR and PFR Steam Generators have two very good examples of how the designer can ease or severely handicap the operator in coping with sodium/water leakages. Good, quick access to tube ends is achieved in the existing PFR Evaporator by simply unbolting the steam/water closure head, but on the superheater and reheater hand-caps have

Future steam generator designs. Single wall designs

Energy Technology Data Exchange (ETDEWEB)

Hayden, O [Nuclear Power Company Ltd, Warrington, Cheshire (United Kingdom)

1978-10-01

The easily removable 'U' tube design style adopted in the UK for the existing PFR Steam Generators, the Replacement Units now in production and for the future CDFR, gives the operator an extremely valuable option in the event of a water/steam leak occurring inside the Steam Generator. He can choose to shut-down, attempt to find the leak, assess damage, repair, revalidate and return to service in situ, or he can elect to remove the defect unit and replace with a 'proven' spare before returning the circuit to power. With the latter approach the resultant outage time is a known entity of about two weeks. If a repair is attempted in situ, predictions of outage time can become a matter of guesswork since one has no 'guaranteed' method of leak location and the assessment of secondary damage may be very time consuming, depending on the size and type of the original leak together with the particular design style of the Steam Generator. A further significant advantage of the removable 'U' tube design concept is that periodic interchanging of bundles with a spare enables routine chemical cleaning and thorough scheduled tube inspections, with specimen tube sample removal if required for monitoring purposes. If necessary, bundle decontamination can be undertaken to assess engineering deterioration to various degrees of thoroughness ranging from 100% equivalent factory final assembly inspection, to partial decontamination operating via a glovebox type of maintenance bag arrangement, examining local points of both shell and tube areas of the bundle. Many lessons from the last five years' experience of PFR will be incorporated into the design of the CDFR and PFR Steam Generators have two very good examples of how the designer can ease or severely handicap the operator in coping with sodium/water leakages. Good, quick access to tube ends is achieved in the existing PFR Evaporator by simply unbolting the steam/water closure head, but on the superheater and reheater hand-caps have

Reheating signature in the gravitational wave spectrum from self-ordering scalar fields

Energy Technology Data Exchange (ETDEWEB)

Kuroyanagi, Sachiko [Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk, 790-784 (Korea, Republic of); Hiramatsu, Takashi [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, 606-8502 Japan (Japan); Yokoyama, Jun' ichi, E-mail: skuro@nagoya-u.jp, E-mail: hiramatz@yukawa.kyoto-u.ac.jp, E-mail: yokoyama@resceu.s.u-tokyo.ac.jp [Research Center for the Early Universe (RESCEU), School of Science, The University of Tokyo, Tokyo, 113-0033 Japan (Japan)

2016-02-01

We investigate the imprint of reheating on the gravitational wave spectrum produced by self-ordering of multi-component scalar fields after a global phase transition. The equation of state of the Universe during reheating, which usually has different behaviour from that of a radiation-dominated Universe, affects the evolution of gravitational waves through the Hubble expansion term in the equations of motion. This gives rise to a different power-law behavior of frequency in the gravitational wave spectrum. The reheating history is therefore imprinted in the shape of the spectrum. We perform 512{sup 3} lattice simulations to investigate how the ordering scalar field reacts to the change of the Hubble expansion and how the reheating effect arises in the spectrum. We also compare the result with inflation-produced gravitational waves, which has a similar spectral shape, and discuss whether it is possible to distinguish the origin between inflation and global phase transition by detecting the shape with future direct detection gravitational wave experiments such as DECIGO.

Numerical analysis of performance of steam reformer of methane reforming hydrogen production system connected with high-temperature gas-cooled reactor

International Nuclear Information System (INIS)

Yin Huaqiang; Jiang Shengyao; Zhang Youjie

2007-01-01

Methane conversion rate and hydrogen output are important performance indexes of the steam reformer. The paper presents numerical analysis of performance of the reformer connected with high-temperature gas-cooled reactor HTR-10. Setting helium inlet flow rate fixed, performance of the reformer was examined with different helium inlet temperature, pressure, different process gas temperature, pressure, flow rate, and different steam to carbon ratio. As the range concerned, helium inlet temperature has remarkable influence on the performance, and helium inlet temperature, process gas temperature and pressure have little influence on the performance, and improving process gas flow rate, methane conversion rate decreases and hydrogen output increases, however improving steam to carbon ratio has reverse influence on the performance. (authors)

3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

Science.gov (United States)

Jang, J. Y.; Lee, Y. W.; Lin, C. N.; Wang, C. H.

2016-05-01

A three-dimensional mathematical transient heat transfer model for the prediction of temperature distribution within the slab has been developed by considering the thermal radiation in the walking-beam-type reheating furnace chamber. The steel slabs are heated up through the non-firing, preheating, 1st-heating, 2nd-heating, and soaking zones in the furnace, respectively, where the furnace wall temperature is function of time. Comparison with the in-situ experimental data from Steel Company in Taiwan shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace. The effects of different skid button height (H=60mm, 90mm, and 120mm) and different gap distance between two slabs (S=50mm, 75mm, and 100mm) on the slab skid mark formation and temperature profiles are investigated. It is found that the skid mark severity decreases with an increase in the skid button height. The effect of gap distance is important only for the slab edge planes, while it is insignificant for the slab central planes.

Furan formation during storage and reheating of sterilised vegetable purées.

Science.gov (United States)

Palmers, Stijn; Grauwet, Tara; Buvé, Carolien; Van de Vondel, Lore; Kebede, Biniam T; Hendrickx, Marc E; Van Loey, Ann

2015-01-01

To this day, research for furan mitigation has mostly targeted the levels of food production and handling of prepared foods by the consumer. However, part of the furan concentrations found in commercially available food products might originate from chemical deterioration reactions during storage. A range of individual vegetable purées was stored at two different temperatures to investigate the effects of storage on the furan concentrations of shelf-stable, vegetable-based foods. After 5 months of storage at 35°C (temperature-abuse conditions), a general increase in furan concentrations was observed. The furan formation during storage could be reduced by storing the vegetable purées at a refrigerated temperature of 4°C, at which the furan concentrations remained approximately constant for at least 5 months. Following storage, the vegetable purées were briefly reheated to 90°C to simulate the effect of the final preparation step before consumption. Contrary to storage, furan concentrations decreased as a result of evaporative losses. Both refrigerated storage and the reheating step prior to consumption showed the potential of mitigation measures for furan formation in vegetable-based foods (e.g. canned vegetables, ready-to-eat soups, sauces or baby foods). Next to furan, the vegetable purées were analysed for 2- and 3-methylfuran. Tomato was very susceptible to the formation of both alkylated derivatives of furan, as opposed to the other vegetables in this study. Methylfuran concentrations rapidly decreased during storage, which was contrary to the results observed for furan.

Coupling of high temperature nuclear reactor with chemical plant by means of steam loop with heat pump

Directory of Open Access Journals (Sweden)

Kopeć Mariusz

2017-01-01

Full Text Available High temperature nuclear reactors (HTR can be used as an excellent, emission-free source of technological heat for various industrial applications. Their outlet helium temperature (700°-900°C allows not only for heat supply to all processes below 600°C (referred to as “steam class”, but also enables development of clean nuclear-assisted hydrogen production or coal liquefaction technologies with required temperatures up to 900°C (referred to as “chemical class”. This paper presents the results of analyses done for various configurations of the steam transport loop coupled with the high-temperature heat pump designed for “chemical class” applications. The advantages and disadvantages as well as the key issues are discussed in comparison with alternative solutions, trying to answer the question whether the system with the steam loop and the hightemperature heat pump is viable and economically justified.

A system for regulating the pressure of resuperheated steam in high temperature gas-cooled reactor power stations

International Nuclear Information System (INIS)

Braytenbah, A.S.; Jaegines, K.O.

1975-01-01

The invention relates to a system for regulating steam-pressure in the re-superheating portion of a steam-boiler receiving heat from a gas-cooled high temperature nuclear reactor, provided with gas distributing pumps driven by steam-turbines. The system comprises means for generating a pressure signal of desired magnitude for the re-superheating portion, and means for providing a real pressure in the re-superheating portion, means (including a by-passing device) for generating steam-flow rate signal of desired magnitude, a turbine by-pass device comprising a by-pass tapping means for regulating the steam-flow-rate in said turbine according to the desired steam-flow rate signal and means for controlling said by-pass tapping means according to said desired steam-flow-rate signal [fr

Design and field operation of 1175 MW steam turbine for Ohi Nuclear Power Station

International Nuclear Information System (INIS)

Hirota, Yoshio; Nakagami, Yasuo; Fujii, Hisashi; Shibanai, Hirooki.

1980-01-01

Two 1175 MW steam turbine and generator units have been successfully in commercial operation since March 1979 and December 1979 respectively at Ohi Nuclear Power Station of the Kansai Electric Power Company. Those units, the largest in their respective outputs in Japan, have also such remarkable design features as two-stage reheat, nozzle governing turbine, water cooled generator stator and turbine-driven feedwater pumps. This paper covers design features and some topics of various pre-operational tests of the above-mentioned units. (author)

Molten salt steam generator subsystem research experiment. Volume I. Phase 1 - Final report

Energy Technology Data Exchange (ETDEWEB)

None

1984-10-01

A study was conducted for Phase 1 of a two-phase project whose objectives were to develop a reliable, cost-effective molten salt steam generating subsystem for solar thermal plants, minimize uncertainty in capital, operating, and maintenance costs, and demonstrate the ability of molten salt to generate high-pressure, high-temperature steam. The Phase 1 study involved the conceptual design of molten salt steam generating subsystems for a nominal 100-MWe net stand-alone solar central receiver electric generating plant, and a nominal 100-MWe net hybrid fossil-fueled electric power generating plant that is 50% repowered by a solar central receiver system. As part of Phase 1, a proposal was prepared for Phase 2, which involves the design, construction, testing and evaluation of a Subsystem Research Experiment of sufficient size to ensure successful operation of the full-size subsystem designed in Phase 1. Evaluation of several concepts resulted in the selection of a four-component (preheater, evaporator, superheater, reheater), natural circulation, vertically oriented, shell and tube (straight) heat exchanger arrangement. Thermal hydraulic analysis of the system included full and part load performance, circulation requirements, stability, and critical heat flux analysis. Flow-induced tube vibration, tube buckling, fatigue evaluation of tubesheet junctions, steady-state tubesheet analysis, and a simplified transient analysis were included in the structural analysis of the system. Operating modes and system dynamic response to load changes were identified. Auxiliary equipment, fabrication, erection, and maintenance requirements were also defined. Installed capital costs and a project schedule were prepared for each design.

Characterization of elevated temperature properties of heat exchanger and steam generator alloys

International Nuclear Information System (INIS)

Wright, J.K.; Carroll, L.J.; Cabet, C.; Lillo, T.M.; Benz, J.K.; Simpson, J.A.; Lloyd, W.R.; Chapman, J.A.; Wright, R.N.

2012-01-01

The Next Generation Nuclear Plant project is considering Alloy 800H and Alloy 617 for steam generator and intermediate heat exchangers. It is envisioned that a steam generator would operate with reactor outlet temperatures from 750 to 800 °C, while an intermediate heat exchanger for primary to secondary helium would operate up to an outlet temperature of 950 °C. Although both alloys are of interest due in part to their technical maturity, a number of specific properties require further characterization for design of nuclear components. Strain rate sensitivity of both alloys has been characterized and is found to be significant above 600 °C. Both alloys also exhibit dynamic strain aging, characterized by serrated flow, over a wide range of temperatures and strain rates. High temperature tensile testing of Alloy 617 and Alloy 800H has been conducted over a range of temperatures. Dynamic strain aging is a concern for these materials since it is observed to result in reduced ductility for many solid solution alloys. Creep, fatigue, and creep–fatigue properties of Alloy 617 have been measured as well, with the goal of determining the influence of the temperature, strain rate and atmosphere on the creep–fatigue life of Alloy 617. Elevated temperature properties and implications for codification of the alloys will be described.

Influence of high-temperature steam on the reactivity of CaO sorbent for CO₂ capture.

Science.gov (United States)

Donat, Felix; Florin, Nicholas H; Anthony, Edward J; Fennell, Paul S

2012-01-17

Calcium looping is a high-temperature CO(2) capture technology applicable to the postcombustion capture of CO(2) from power station flue gas, or integrated with fuel conversion in precombustion CO(2) capture schemes. The capture technology uses solid CaO sorbent derived from natural limestone and takes advantage of the reversible reaction between CaO and CO(2) to form CaCO(3); that is, to achieve the separation of CO(2) from flue or fuel gas, and produce a pure stream of CO(2) suitable for geological storage. An important characteristic of the sorbent, affecting the cost-efficiency of this technology, is the decay in reactivity of the sorbent over multiple CO(2) capture-and-release cycles. This work reports on the influence of high-temperature steam, which will be present in flue (about 5-10%) and fuel (∼20%) gases, on the reactivity of CaO sorbent derived from four natural limestones. A significant increase in the reactivity of these sorbents was found for 30 cycles in the presence of steam (from 1-20%). Steam influences the sorbent reactivity in two ways. Steam present during calcination promotes sintering that produces a sorbent morphology with most of the pore volume associated with larger pores of ∼50 nm in diameter, and which appears to be relatively more stable than the pore structure that evolves when no steam is present. The presence of steam during carbonation reduces the diffusion resistance during carbonation. We observed a synergistic effect, i.e., the highest reactivity was observed when steam was present for both calcination and carbonation.

Experiment Plan of High Temperature Steam and Carbon dioxide Co-electrolysis for Synthetic Gas Production

International Nuclear Information System (INIS)

Yoon, Duk-Joo; Ko, Jae-Hwa

2008-01-01

Currently, Solid oxide fuel cells (SOFC) come into the spotlight in the middle of the energy technologies of the future for highly effective conversion of fossil fuels into electricity without carbon dioxide emission. The SOFC is a reversible cell. By applying electrical power to the cell, which is solid oxide electrolysis cell (SOEC), it is possible to produce synthetic gas (syngas) from high temperature steam and carbon dioxide. The produced syngas (hydrogen and carbon monoxide) can be used for synthetic fuels. This SOEC technology can use high temperature from VHTRs for high efficiency. This paper describes KEPRI's experiment plan of high temperature steam and carbon co-electrolysis for syngas production using SOEC technology

Modelling of steam condensation in the primary flow channel of a gas-heated steam generator

International Nuclear Information System (INIS)

Kawamura, H.; Meister, G.

1982-10-01

A new simulation code has been developed for the analysis of steam ingress accidents in high temperatures reactors which evaluates the heat transfer in a steam generator headed by a mixture of helium and water steam. Special emphasis is laid on the analysis of steam condensation in the primary circuit of the steam generator. The code takes wall and bulk condensation into account. A new method is proposed to describe the entrainment of water droplets in the primary gas flow. Some typical results are given. Steam condensation in the primary channel may have a significant effect on temperature distributions. The effect on the heat transferred by the steam generator, however, is found to be not so prominent as might be expected. The reason is discussed. A simplified code will also be described, which gives results with reasonable accuracy within much shorter execution times. This code may be used as a program module in a program simulating the total primary circuit of a high temperature reactor. (orig.) [de

Catalytic steam gasification of biomass in fluidized bed at low temperature: Conversion from livestock manure compost to hydrogen-rich syngas

International Nuclear Information System (INIS)

Xiao, Xianbin; Le, Duc Dung; Li, Liuyun; Meng, Xianliang; Cao, Jingpei; Morishita, Kayoko; Takarada, Takayuki

2010-01-01

Utilizing large amounts of animal waste as a source of renewable energy has the potential to reduce its disposal problems and associated pollution issues. Gasification characteristics of the manure compost make it possible for low temperature gasification. In this paper, an energy efficient approach to hydrogen-rich syngas from manure compost is represented at relatively low temperature, around 600 o C, in a continuous-feeding fluidized bed reactor. The effects of catalyst performance, reactor temperature, steam, and reaction type on gas yield, gas composition, and carbon conversion efficiency are discussed. The Ni-Al 2 O 3 catalyst simultaneously promotes tar cracking and steam reforming. Higher temperature contributes to higher gas yield and carbon conversion. The steam introduction increases hydrogen yield, by steam reforming and water-gas shift reaction. Two-stage gasification is also tried, showing the advantage of better catalyst utilization and enhancing the catalytic reactions to some extent.

Steam condenser

International Nuclear Information System (INIS)

Masuda, Fujio

1980-01-01

Purpose: To enable safe steam condensation by providing steam condensation blades at the end of a pipe. Constitution: When high temperature high pressure steam flows into a vent pipe having an opening under water in a pool or an exhaust pipe or the like for a main steam eacape safety valve, non-condensable gas filled beforehand in the steam exhaust pipe is compressed, and discharged into the water in the pool. The non-condensable gas thus discharged from the steam exhaust pipe is introduced into the interior of the hollow steam condensing blades, is then suitably expanded, and thereafter exhausted from a number of exhaust holes into the water in the pool. In this manner, the non-condensable gas thus discharged is not directly introduced into the water in the pool, but is suitable expanded in the space of the steam condensing blades to suppress extreme over-compression and over-expansion of the gas so as to prevent unstable pressure vibration. (Yoshihara, H.)

Listeria Infections (For Parents)

Science.gov (United States)

... ingest the bacteria by eating foods such as deli meats and cold cuts, soft-ripened cheese, undercooked ... queso fresco). Reheat precooked, prepackaged foods — such as deli meats or hot dogs — to steaming hot temperatures, ...

Design and field operation of 1175 MW steam turbine for Ohi Nuclear Power Station

International Nuclear Information System (INIS)

Hirota, Y.; Nakagami, Y.; Fujii, H.; Shibanai, H.

1980-01-01

Two 1,175 MW steam turbine and generator units have been successfully in commercial operation since March 1979 and December 1979 respectively at Ohi Nuclear Power Station of the Kansai Electric Power Company. Those units, the largest in their respective outputs in Japan, have also such remarkable design features as two-stage reheat, nozzle governing turbine, water cooled generator stator and turbine-driven feedwater pumps. This paper covers design features and some topics of various pre-operational tests of the above-mentioned units. (author)

Fundamental study on temperature estimation of steam generator tubes at sodium-water reaction

International Nuclear Information System (INIS)

Furukawa, Tomohiro; Yoshida, Eiichi

2008-11-01

In case of the tube failure in the steam generator of the sodium cooled fast breeder reactor, its adjoined tubes are rapidly heated up by the chemical reaction between sodium and water/steam. And it is known that the tubes have the damage called 'wastage' by the disclosure steam jet. This research is a fundamental study based on the metallography about temperature estimation of the damaged tubes at the sodium-water reaction for the establishment of mechanism analysis technique of the behavior. In the examination, the material which gave the rapid thermal history which imitated sodium-water reaction was produced. And it was investigated whether the thermal history (i.e. maximum temperature and the holding time) of the samples could be presumed from the metallurgical examination of the samples. The major results are as follows: (1) The microstructure of the sample which was given the rapid thermal heating has reserved the influence of the maximum temperature and the time, and the structure can explain by referring to the equilibrium diagram and the continuous cooling transformation diagram. (2) Results of the electrolytic extraction of the samples, the ratio of the remained volume to the electrolyzed volume degreased with the increase of the maximum temperature and the time. Furthermore, it was observed the correlation between the remained volume of each element (Cr, Mo, Fe, V and Nb) and the thermal history. (3) It was obtained that the thermal history of the tubes damaged by sodium-water reaction might be able to be estimated from the metallurgical examinations. (author)

Characterization of Elevated Temperature Properties of Heat Exchanger and Steam Generator Alloys

International Nuclear Information System (INIS)

Wright, J.K.; Carroll, L.J.; Benz, J.K.; Simpson, J.A.; Wright, R.N.; Lloyd, W.R.; Chapman, J.A.

2010-01-01

The Next Generation Nuclear Plant project is considering Alloy 800H and Alloy 617 for steam generator and intermediate heat exchangers. It is envisioned that a steam generator would operate with reactor outlet temperatures from 750 to 800 C, while an intermediate heat exchanger for primary to secondary helium would operate up to an outlet temperature of 950 C. Although both alloys are of interest due in part to their technical maturity, a number of specific properties require further characterization for design of nuclear components. Strain rate sensitivity of both alloys has been characterized and is found to be significant above 600 C. Both alloys also exhibit dynamic strain aging, characterized by serrated flow, over a wide range of temperatures and strain rates. In general dynamic strain aging is observed to begin at higher temperatures and serrated flow persists to higher temperatures in Alloy 617 compared to Alloy 800H. Dynamic strain aging is a concern for these materials since it is observed to result in reduced ductility for many solid solution alloys. The role of dynamic strain aging in the creep-fatigue behavior of Alloy 617 at temperatures of 800 C and above has also been examined in detail. Serrated flow is found to persist in cyclic stress-strain curves up to nearly the cycle to failure in some temperature and strain regimes. Results of those experiments and implications for creep-fatigue testing protocols will be described.

Membrane steam reforming of natural gas for hydrogen production by utilization of medium temperature nuclear reactor

International Nuclear Information System (INIS)

Djati Hoesen Salimy

2010-01-01

The assessment of steam reforming process with membrane reactor for hydrogen production by utilizing of medium temperature nuclear reactor has been carried out. Difference with the conventional process of natural gas steam reforming that operates at high temperature (800-1000°C), the process with membrane reactor operates at lower temperature (~500°C). This condition is possible because the use of perm-selective membrane that separate product simultaneously in reactor, drive the optimum conversion at the lower temperature. Besides that, membrane reactor also acts the role of separation unit, so the plant will be more compact. From the point of nuclear heat utilization, the low temperature of process opens the chance of medium temperature nuclear reactor utilization as heat source. Couple the medium temperature nuclear reactor with the process give the advantage from the point of saving fossil fuel that give direct implication of decreasing green house gas emission. (author)

Development of a water separator for steam drying in nuclear power plants

International Nuclear Information System (INIS)

Kall, H.

1979-01-01

In the wet steam of nuclear power plants with light water cooling the content of liquid phase before entering the high- and low-pressure turbine or at the inlet of the reheater connected in between is limited to a few parts per thousand. For the mechanical drying necessary to maintain this moisture limit there is suited the socalled lamellar separator, in which the vertical laminae, arranged one beside the other, confine a great number of separating ducts, bended in periodically changing sequence, through which wet steam is flowing. In the development of such a lamellar separator with internal drain channels described in this paper the droplet motion in the carrier gas stream and the discharge of the separated liquid is treated independently from each other. The mathematical and experimental study of the first-mentioned partial process leads to its complete description in a dimensionless separation diagram. During the subsequent discharge of the primarily separated droplet fluid there may be torn off droplets by the steam flow and carried away from the separator.The limit for the draining capacity reached with the occurrence of this phenomenon was determined in preliminary experiments with air and water and in experiments with wet steam carried out close to operating conditions. (orig.) 891 GL/orig. 892 RRD [de

Thermal performances of molten salt steam generator

International Nuclear Information System (INIS)

Yuan, Yibo; He, Canming; Lu, Jianfeng; Ding, Jing

2016-01-01

Highlights: • Thermal performances of molten salt steam generator were experimentally studied. • Overall heat transfer coefficient reached maximum with optimal molten salt flow rate. • Energy efficiency first rose and then decreased with salt flow rate and temperature. • Optimal molten salt flow rate and temperature existed for good thermal performance. • High inlet water temperature benefited steam generating rate and energy efficiency. - Abstract: Molten salt steam generator is the key technology for thermal energy conversion from high temperature molten salt to steam, and it is used in solar thermal power station and molten salt reactor. A shell and tube type molten salt steam generator was set up, and its thermal performance and heat transfer mechanism were studied. As a coupling heat transfer process, molten salt steam generation is mainly affected by molten salt convective heat transfer and boiling heat transfer, while its energy efficiency is also affected by the heat loss. As molten salt temperature increased, the energy efficiency first rose with the increase of heat flow absorbed by water/steam, and then slightly decreased for large heat loss as the absorbed heat flow still rising. At very high molten salt temperature, the absorbed heat flow decreased as boiling heat transfer coefficient dropping, and then the energy efficiency quickly dropped. As the inlet water temperature increased, the boiling region in the steam generator remarkably expanded, and then the steam generation rate and energy efficiency both rose with the overall heat transfer coefficient increasing. As the molten salt flow rate increased, the wall temperature rose and the boiling heat transfer coefficient first increased and then decreased according to the boiling curve, so the overall heat transfer coefficient first increased and then decreased, and then the steam generation rate and energy efficiency of steam generator both had maxima.

How to compute the power of a steam turbine with condensation, knowing the steam quality of saturated steam in the turbine discharge

Energy Technology Data Exchange (ETDEWEB)

Hernandez Albarran, Manuel Jaime; Krever, Marcos Paulo Souza [Braskem, Sao Paulo, SP (Brazil)

2009-07-01

To compute the power and the thermodynamic performance in a steam turbine with condensation, it is necessary to know the quality of the steam in the turbine discharge and, information of process variables that permit to identifying with high precision the enthalpy of saturated steam. This paper proposes to install an operational device that will expand the steam from high pressure point on the shell turbine to atmosphere, both points with measures of pressure and temperature. Arranging these values on the Mollier chart, it can be know the steam quality value and with this data one can compute the enthalpy value of saturated steam. With the support of this small instrument and using the ASME correlations to determine the equilibrium temperature and knowing the discharge pressure in the inlet of surface condenser, the absolute enthalpy of the steam discharge can be computed with high precision and used to determine the power and thermodynamic efficiency of the turbine. (author)

Analysis of experimental characteristics of multistage steam-jet electors of steam turbines

Science.gov (United States)

Aronson, K. E.; Ryabchikov, A. Yu.; Brodov, Yu. M.; Brezgin, D. V.; Zhelonkin, N. V.; Murmanskii, I. B.

2017-02-01

A series of questions for specification of physical gas dynamics model in flow range of steam-jet unit and ejector computation methodology, as well as functioning peculiarities of intercoolers, was formulated based on analysis of experimental characteristics of multistage team-jet steam turbines. It was established that coefficient defining position of critical cross-section of injected flow depends on characteristics of the "sound tube" zone. Speed of injected flow within this tube may exceed that of sound, and pressure jumps in work-steam decrease at the same time. Characteristics of the "sound tube" define optimal axial sizes of the ejector. According to measurement results, the part of steam condensing in the first-stage coolant constitutes 70-80% of steam amount supplied into coolant and is almost independent of air content in steam. Coolant efficiency depends on steam pressure defined by operation of steam-jet unit of ejector of the next stage after coolant of steam-jet stage, temperature, and condensing water flow. As a rule, steam entering content of steam-air mixture supplied to coolant is overheated with respect to saturation temperature of steam in the mixture. This should be taken into account during coolant computation. Long-term operation causes changes in roughness of walls of the ejector's mixing chamber. The influence of change of wall roughness on ejector characteristic is similar to the influence of reverse pressure of the steam-jet stage. Until some roughness value, injection coefficient of the ejector stage operating in superlimiting regime hardly changed. After reaching critical roughness, the ejector switches to prelimiting operating regime.

On effect of some thermodeformation parameters of welding cycle on tendency of pearlitic heat-resisting steels to fracture in reheating

International Nuclear Information System (INIS)

Prokhorov, N.N.; Bardokin, E.V.

1979-01-01

Studied is the inclination of the 12Kh1MF, 15Kh3M1F and N18K9M5T steels subject to thermodeformation cycle imitating a welding one, to fracture in reheating. A hot-rolled metal then subject to the same thermal treatment was used. The imitation of thermodeformation cycle of the welding permitted to vary maximum heating temperatures, the period during which the metal is kept at temperatures higher than 1100 deg C, and the cooling rate of ajacent zone metal. It is shown that the curve of the dependence of deformation ability and the tendency to fracture at the reheating of adjacent zone metal on the rate of its cooling at welding is U-shaped. Deformation ability has its maximum value at the cooling rate of 30 deg c/s in the range 1300 to 1000 deg C

Reheat cracking susceptibility of new generation 2%CrMo(W)V P23 steel multipass welds made using matching and mis-matching filler metals

Energy Technology Data Exchange (ETDEWEB)

Nevasmaa, P.; Salonen, J.; Holmstroem, S. [VTT Technical Research Centre of Finland, Espoo (Finland)

2007-06-15

In comparison with conventional creep resisting grade T/P22, the modified 2%Cr steels T/P23 and T/P24 show nearly twice the creep strength at typical service temperatures of about 520-570 deg C. The possibility of welding thin-wall boiler tubes without preheating or PWHT has promoted the use of T23 and T24 in practical boiler service. For thick-wall applications and multipass welds, welding consumables still require further development to improve creep strength and ductility. Susceptibility to reheat cracking and hydrogen cracking increase with the wall-thickness and structural rigidity of the component. Consequently, thick-wall sections generally require the use of PWHT and sometimes preheating as well. This paper is concerned with weldability of P23 pipe steel, with particular emphasis on reheat cracking sensitivity of simulated HAZ microstructures and thick-section multipass welds made using closely matching and mis-matching filler metals. The results demonstrate that the weld metal is far more critical than the parent steel HAZ, both in terms of reheat cracking sensitivity and ductility and toughness. In the as-welded condition, the weld metal exhibited excessive hardness of {approx}380 HV and only diminutive Charpy toughness at room temperature. Adoption of the PWHT (760 deg C/2h) enhanced the weldment toughness; however, it also inevitably raises risk to reheat cracking in the weld metal that showed values of reduction of area (RA) no more than 2-3% in the BWI cracking test. The results imply that thick-section multipass welds made using filler metal with the chemical composition closer to P24 grade material are much less susceptible to reheat cracking than 'matching' P23 grade welds. (orig.)

Hydrogen production by high-temperature electrolysis of water vapor steam. Test results obtained with an electrolysis tube

International Nuclear Information System (INIS)

Hino, Ryutaro; Miyamoto, Yoshiaki

1995-01-01

High-temperature electrolysis of water vapor steam is an advanced hydrogen production process decomposing high temperature steam up to 1,000degC, which applies an electro-chemical reaction reverse to the solid oxide fuel cell. At Japan Atomic Energy Research Institute, laboratory-scale experiments have been conducted using a practical electrolysis tube with 12 electrolysis cells in order to develop heat utilization systems for high-temperature gas-cooled reactors. The electrolysis cells of which electrolyte was yttria-stabilized zirconia were formed on a porous ceramic tube in series by plasma spraying. In the experiments, water steam mixed with argon carrier gas was supplied into the electrolysis tube heated at a constant temperature regulated in the range from 850degC to 950degC, and electrolysis power was supplied by a DC power source. Hydrogen production rate increased with applied voltage and electrolysis temperature; the maximum production rate was 6.9Nl/h at 950degC. Hydrogen production rate was correlated with applied current densities on the basis of experimental data. High energy efficiency was achieved under the applied current density ranging from 80 to 100 mA/cm 2 . (author)

Simulation and parametric optimisation of thermal power plant cycles

Directory of Open Access Journals (Sweden)

P. Ravindra Kumar

2016-09-01

Full Text Available The objective of the paper is to analyse parametric studies and optimum steam extraction pressures of three different (subcritical, supercritical and ultra-supercritical coal fired power plant cycles at a particular main steam temperature of 600 °C by keeping the reheat temperature at 537 °C and condenser pressure at 0.09 bar as constant. In order to maximize the heat rate gain possible with supercritical and ultra-supercritical steam conditions, eight stages of feed water heater arrangement with single reheater is considered. The system is optimized in such a way that the percentage exergetic losses are reduced for the increase of the exergetic efficiency and higher fuel utilization. The plant cycles are simulated and optimized by using Cycle Tempo 5.0 simulation software tool. From the simulation study, it is observed that the thermal efficiency of the three different power plant cycles obtained as 41.40, 42.48 and 43.03%, respectively. The specific coal consumption for three different power plant cycles are 0.56, 0.55 and 0.54 Tonnes/MWh. The improvement in feed water temperatures at the inlet of steam generator of respective cycles are 291, 305 and 316 °C.

Effect of Primary Recrystallized Microstructure and Nitriding on Secondary Recrystallization in Grain Oriented Silicon Steel by Low Temperature Slab Reheating

Directory of Open Access Journals (Sweden)

LIU Gong-tao

2018-01-01

Full Text Available Different primary recrystallized grain sizes were obtained by controlling decarburization process in grain oriented silicon steel produced by low temperature slab reheating technique. The effect of primary grain size on secondary recrystallization and magnetic properties was studied. The appropriate nitrogen content after nitriding was explored in case of very large primary grain size, and the effect of {411}〈148〉 primary recrystallized texture on the abnormal growth behavior was discussed. The results show that an increase in average primary grain size from 10μm to 15μm leads to an increase of secondary recrystallization temperature and a sharper Goss texture with higher magnetic permeability, in the condition of a very large average primary grain size of 28μm, the suitable amount of nitrogen increases to about 6×10-4. The {411}〈148〉 oriented grains in primary recrystallized microstructure can easily grow into larger sizes due to their size advantage, and thus hinder the abnormal growth of secondary grains, moreover, the hindering effect is more pronounced in the abnormal growth of Brass-oriented grains due to their misorientation with low migration rate other than Goss grains.

Molybdenum Disilicide Oxidation Kinetics in High Temperature Steam

Energy Technology Data Exchange (ETDEWEB)

Wood, Elizabeth Sooby [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Parker, Stephen Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nelson, Andrew Thomas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-09-07

The Fuel Cycle Research and Development program’s Advanced Fuels Campaign is currently supporting a range of experimental efforts aimed at the development and qualification of ‘accident tolerant’ nuclear fuel forms. One route to enhance the accident tolerance of nuclear fuel is to replace the zirconium alloy cladding, which is prone to rapid oxidation in steam at elevated temperatures, with a more oxidation-resistant cladding. Several cladding replacement solutions have been envisaged. The cladding can be completely replaced with a more oxidation resistant alloy, a layered approach can be used to optimize the strength, creep resistance, and oxidation tolerance of various materials, or the existing zirconium alloy cladding can be coated with a more oxidation-resistant material. Molybdenum is one candidate cladding material favored due to its high temperature creep resistance. However, it performs poorly under autoclave testing and suffers degradation under high temperature steam oxidation exposure. Development of composite cladding architectures consisting of a molybdenum core shielded by a molybdenum disilicide (MoSi₂) coating is hypothesized to improve the performance of a Mo-based cladding system. MoSi₂ was identified based on its high temperature oxidation resistance in O₂ atmospheres (e.g. air and “wet air”). However, its behavior in H₂O is less known. This report presents thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and x-ray diffraction (XRD) results for MoSi₂ exposed to 670-1498 K water vapor. Synthetic air (80-20%, Ar-O₂) exposures were also performed, and those results are presented here for a comparative analysis. It was determined that MoSi₂ displays drastically different oxidation behavior in water vapor than in dry air. In the 670-1498 K temperature range, four distinct behaviors are observed. Parabolic oxidation is exhibited in only 670

Comparative Study of Micro- and Nano-structured Coatings for High-Temperature Oxidation in Steam Atmospheres

OpenAIRE

Pérez, F.J.; Castañeda, I.; Hierro, M.P.; Escobar Galindo, R.; Sánchez-López, J.C.; Mato, S.

2014-01-01

For many high-temperature applications, coatings are applied in order to protect structural materials against a wide range of different environments: oxidation, metal dusting, sulphidation, molten salts, steam, etc. The resistance achieved by the use of different kind of coatings, such as functionally graded material coatings, has been optimized with the latest designs. In the case of supercritical steam turbines, many attempts have been made in terms of micro-structural coatings design, main...

What is geothermal steam worth?

International Nuclear Information System (INIS)

Thorhallsson, S.; Ragnarsson, A.

1992-01-01

Geothermal steam is obtained from high-temperature boreholes, either directly from the reservoir or by flashing. The value of geothermal steam is similar to that of steam produced in boilers and lies in its ability to do work in heat engines such as turbines and to supply heat for a wide range of uses. In isolated cases the steam can be used as a source of chemicals, for example the production of carbon dioxide. Once the saturated steam has been separated from the water, it can be transported without further treatment to the end user. There are several constraints on its use set by the temperature of the reservoir and the chemical composition of the reservoir fluid. These constraints are described (temperature of steam, scaling in water phase, gas content of steam, well output) as are the methods that have been adopted to utilize this source of energy successfully. Steam can only be transported over relatively short distances (a few km) and thus has to be used close to the source. Examples are given of the pressure drop and sizing of steam mains for pipelines. The path of the steam from the reservoir to the end user is traced and typical cost figures given for each part of the system. The production cost of geothermal steam is estimated and its sensitivity to site-specific conditions discussed. Optimum energy recovery and efficiency is important as is optimizing costs. The paper will treat the steam supply system as a whole, from the reservoir to the end user, and give examples of how the site-specific conditions and system design have an influence on what geothermal steam is worth from the technical and economic points of view

Metal temperature monitoring in corrosive gases at high temperature and high thermal flows; Monitoreo de temperaturas de metal en gases corrosivos a alta temperatura y altos flujos termicos

Energy Technology Data Exchange (ETDEWEB)

Huerta Espino, Mario; Martinez Flores, Marco Antonio; Martinez Villafane, Alberto; Porcayo Calderon, Jesus; Gomez Guzman, Roberto; Reyes Cervantes, Fernando [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1991-12-31

The direct measurement of metal temperatures during operation in superheater, reheater, and water wall tubes in zones exposed to high thermal flows is of great interest for the operation and analysis of the correct functioning of a steam generator. The operation temperature measurement of these zones differs very much of the monitored temperature in headers in the dead chamber, since the temperature measured in this zone is the steam temperature that does not reflect the one detected in the gas zone. For this reason, the thermocouples implant in gas zones will detect the real metal temperature and the incidence that some operation variables might have on it (Martinez et al., (1990). [Espanol] La medicion directa de temperaturas de metal durante operacion en tubos de sobrecalentador, recalentador y pared de agua en zonas expuestas a altos flujos termicos es de gran interes para la operacion y analisis del buen funcionamiento de un generador de vapor. La medicion de la temperatura de operacion de estas zonas, difiere mucho de la temperatura monitoreada en cabezales en zona de camara muerta, ya que la temperatura registrada en esta zona es la de vapor que no es un reflejo de la detectada en zona de gases. Por esta razon, la implantacion de termopares en zona de gases detectara la temperatura de metal real y la incidencia que algunas variables de operacion tengan sobre esta (Martinez et al., 1990).

Metal temperature monitoring in corrosive gases at high temperature and high thermal flows; Monitoreo de temperaturas de metal en gases corrosivos a alta temperatura y altos flujos termicos

Energy Technology Data Exchange (ETDEWEB)

Huerta Espino, Mario; Martinez Flores, Marco Antonio; Martinez Villafane, Alberto; Porcayo Calderon, Jesus; Gomez Guzman, Roberto; Reyes Cervantes, Fernando [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1990-12-31

The direct measurement of metal temperatures during operation in superheater, reheater, and water wall tubes in zones exposed to high thermal flows is of great interest for the operation and analysis of the correct functioning of a steam generator. The operation temperature measurement of these zones differs very much of the monitored temperature in headers in the dead chamber, since the temperature measured in this zone is the steam temperature that does not reflect the one detected in the gas zone. For this reason, the thermocouples implant in gas zones will detect the real metal temperature and the incidence that some operation variables might have on it (Martinez et al., (1990). [Espanol] La medicion directa de temperaturas de metal durante operacion en tubos de sobrecalentador, recalentador y pared de agua en zonas expuestas a altos flujos termicos es de gran interes para la operacion y analisis del buen funcionamiento de un generador de vapor. La medicion de la temperatura de operacion de estas zonas, difiere mucho de la temperatura monitoreada en cabezales en zona de camara muerta, ya que la temperatura registrada en esta zona es la de vapor que no es un reflejo de la detectada en zona de gases. Por esta razon, la implantacion de termopares en zona de gases detectara la temperatura de metal real y la incidencia que algunas variables de operacion tengan sobre esta (Martinez et al., 1990).

Temperature escalation in PWR fuel rod simulators due to the zircaloy/steam reaction: Tests ESSI-1,2,3

International Nuclear Information System (INIS)

Hagen, S.; Malauschek, H.; Wallenfels, K.P.; Peck, S.O.

1983-08-01

This report discusses the test conduct, results, and posttest appearance of three scoping tests (ESSI-1,2,3) investigating temperature escalation in zircaloy clad fuel rods. The experiments are part of an out-of-pile program using electrically heated fuel rod simulators to investigate PWR fuel element behavior up to temperatures of 2000 0 C. These experiments are part of the PNS Severe Fuel Damage Program. The temperature escalation is caused by the exothermal zircaloy/steam reaction, whose reaction rate increases exponentially with the temperature. The tests were performed using different initial oxide layers as a major parameter, obtained by varying the heatup rates and steam exposure times. (orig./RW) [de

Gravitational wave background from reheating after hybrid inflation

International Nuclear Information System (INIS)

Garcia-Bellido, Juan; Figueroa, Daniel G.; Sastre, Alfonso

2008-01-01

The reheating of the Universe after hybrid inflation proceeds through the nucleation and subsequent collision of large concentrations of energy density in the form of bubblelike structures moving at relativistic speeds. This generates a significant fraction of energy in the form of a stochastic background of gravitational waves, whose time evolution is determined by the successive stages of reheating: First, tachyonic preheating makes the amplitude of gravity waves grow exponentially fast. Second, bubble collisions add a new burst of gravitational radiation. Third, turbulent motions finally sets the end of gravitational waves production. From then on, these waves propagate unimpeded to us. We find that the fraction of energy density today in these primordial gravitational waves could be significant for grand unified theory (GUT)-scale models of inflation, although well beyond the frequency range sensitivity of gravitational wave observatories like LIGO, LISA, or BBO. However, low-scale models could still produce a detectable signal at frequencies accessible to BBO or DECIGO. For comparison, we have also computed the analogous gravitational wave background from some chaotic inflation models and obtained results similar to those found by other groups. The discovery of such a background would open a new observational window into the very early universe, where the details of the process of reheating, i.e. the big bang, could be explored. Moreover, it could also serve in the future as a new experimental tool for testing the inflationary paradigm

Lifetime evaluation of superheater tubes exposed to steam oxidation, high temperature corrosion and creep

Energy Technology Data Exchange (ETDEWEB)

Henriksen, N [Elsamprojekt A/S, Faelleskemikerne, Fredericia (Denmark); Hede Larsen, O; Blum, R [I/S Fynsvaerket, Faelleskemikerne, Odense (Denmark)

1996-12-01

Advanced fossil fired plants operating at high steam temperatures require careful design of the superheaters. The German TRD design code normally used in Denmark is not precise enough for the design of superheaters with long lifetimes. The authors have developed a computer program to be used in the evaluation of superheater tube lifetime based on input related to tube dimensions, material, pressure, steam temperature, mass flux, heat flux and estimated corrosion rates. The program is described in the paper. As far as practically feasible, the model seems to give a true picture of the reality. For superheaters exposed to high heat fluxes or low internal heat transfer coefficients as is the case for superheaters located in fluidized bed environments or radiant environments, the program has been extremely useful for evaluation of surface temperature, oxide formation and lifetime. The total uncertainty of the method is mainly influenced by the uncertainty of the determination of the corrosion rate. More precise models describing the corrosion rate as a function of tube surface temperature, fuel parameters and boiler parameters need to be developed. (au) 21 refs.

Guidelines for random excitation forces due to cross flow in steam generators

Energy Technology Data Exchange (ETDEWEB)

Taylor, C.E.; Pettigrew, M.J. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada)

1998-07-01

Random excitation forces can cause low-amplitude tube motion that will result in long-term fretting-wear or fatigue. To prevent these tube failures in steam generators and other heat exchangers, designers and trouble-shooters must have guidelines that incorporate random or turbulent fluid forces. Experiments designed to measure fluid forces have been carried out at Chalk River Laboratories and at other labs around the world. The data from these experiments have been studied and collated to determine suitable guidelines for random excitation forces. In this paper, a guideline for random excitation forces in single-phase cross flow is presented in the form of normalised spectra that are applicable to a wide range of flow conditions and tube frequencies. In particular, the experimental results used in this study were carried out over the full range of flow conditions found in a nuclear steam generator. The proposed guidelines are applicable to steam generators, condensers, reheaters and other shell-and-tube heat exchangers. They may be used for flow-induced vibration analysis of new or existing components, as input to vibration analysis computer codes and as specifications in procurement documents. (author)

Guidelines for random excitation forces due to cross flow in steam generators

International Nuclear Information System (INIS)

Taylor, C.E.; Pettigrew, M.J.

1998-01-01

Random excitation forces can cause low-amplitude tube motion that will result in long-term fretting-wear or fatigue. To prevent these tube failures in steam generators and other heat exchangers, designers and trouble-shooters must have guidelines that incorporate random or turbulent fluid forces. Experiments designed to measure fluid forces have been carried out at Chalk River Laboratories and at other labs around the world. The data from these experiments have been studied and collated to determine suitable guidelines for random excitation forces. In this paper, a guideline for random excitation forces in single-phase cross flow is presented in the form of normalised spectra that are applicable to a wide range of flow conditions and tube frequencies. In particular, the experimental results used in this study were carried out over the full range of flow conditions found in a nuclear steam generator. The proposed guidelines are applicable to steam generators, condensers, reheaters and other shell-and-tube heat exchangers. They may be used for flow-induced vibration analysis of new or existing components, as input to vibration analysis computer codes and as specifications in procurement documents. (author)

Development of a PF fired high efficiency power plant (AD700)

Energy Technology Data Exchange (ETDEWEB)

Blum, R.; Kjaer, S.; Bugge, J. [DONG Energy Generation, Fredericia (Denmark)

2007-05-15

European efforts to start substantial improvements of the performance of well established supercritical coal-fired power technology named the AD700 project began in 1998. Major targets were development of austenitic materials and nickel-based superalloys for the hottest sections of boilers, steam lines and turbines. Other targets were development of boiler and turbine designs for the more advanced conditions and finally economic viability of the AD700 technology has been investigated. The project has been very successful and 40 partners from the European power industry have worked together in several projects co-funded by the European Commission for nearly years. Procurement of mature and commercially optimised AD700 plant could take place around 2015. The investigated nickel-based materials have shown very high creep strengths but they have also shown to be very hard to manufacture, and more efforts to define new machining lines are being started. Ongoing tests indicate that the developed austenitic material will fulfil its creep strength target and is now ready for commercialisation. Development works on boiler and turbine designs for the advanced steam conditions have also been successfully completed but they also clearly indicate that further development work on improved ferritic steel for furnace walls is important. Conventional development of the steam cycles is based on new improved materials, which open for higher steam temperatures and efficiencies whereas other thermodynamic tools are only slowly being accepted. However, in the present paper a proposal for steam cycle improvements not based on higher steam temperatures is presented. The improved cycle is named the Master Cycle (MC) and it is based on a revision of the double reheat steam cycle where the bleeds of the IP turbines have been moved to a feed pump turbine bleeding on the first cold reheat line. Elsam has established protection of a patent for the MC in a number of countries. At constant main

The testing of a steam-water separating device used for vertical steam generators

International Nuclear Information System (INIS)

Ding Xunshen; Cui Baoyuan; Xue Yunkui; Liu Shixun

1989-01-01

The air-water screening tests of a steam-water separating device used for vertical steam generators at low pressure are introduced. The article puts emphasis on the qualification test of the steam-water separating device at hot conditions in a high temperature and pressure water test rig. The performance of the comprehensive test of the steam-water separating device indicates that the humidity of the steam at the drier exit is much less than the specified amount of 0.25%

Durability of bends in high-temperature steam lines under the conditions of long-term operation

Science.gov (United States)

Katanakha, N. A.; Semenov, A. S.; Getsov, L. B.

2015-04-01

The article presents the results of stress-strain state computations and durability of bent and steeply curved branches of high-temperature steam lines carried out on the basis of the finite element method using the modified Soderberg formula for describing unsteady creep processes with taking the accumulation of damage into account. The computations were carried out for bends made of steel grades that are most widely used for manufacturing steam lines (12Kh1MF, 15Kh1M1F, and 10Kh9MFB) and operating at different levels of inner pressure and temperature. The solutions obtained using the developed creep model are compared with those obtained using the models widely used in practice.

Steam Turbine Control Valve Stiction Effect on Power System Stability

International Nuclear Information System (INIS)

Halimi, B.

2010-01-01

four stages. The steam chest is represented by the first stage. The three other stages represent either reheaters or crossover piping. The shaft model which represents a four-mass system is coupled to the mass in a synchronous machine (generator) for a total of five masses. To analyze the oscillation in power system, an IEEE benchmark is used as reference scenario. In this scenario, a single generator is connected to infinite bus via a transmission line

The performance of a temperature cascaded cogeneration system producing steam, cooling and dehumidification

KAUST Repository

Myat, Aung

2013-02-01

This paper discusses the performance of a temperature-cascaded cogeneration plant (TCCP), equipped with an efficient waste heat recovery system. The TCCP, also called a cogeneration system, produces four types of useful energy-namely, (i) electricity, (ii) steam, (iii) cooling and (iv) dehumidification-by utilizing single fuel source. The TCCP comprises a Capstone C-30 micro-turbine that generates nominal capacity of 26 kW of electricity, a compact and efficient waste heat recovery system and a host of waste-heat-activated devices, namely (i) a steam generator, (ii) an absorption chiller, (iii) an adsorption chiller and (iv) a multi-bed desiccant dehumidifier. The performance analysis was conducted under different operation conditions such as different exhaust gas temperatures. It was observed that energy utilization factor could be as high as 70% while fuel energy saving ratio was found to be 28%. © 2013 Desalination Publications.

Measurement of Temperature in the Steam Arcjet During Plasma Arc Cutting

Czech Academy of Sciences Publication Activity Database

Mašláni, Alan; Sember, Viktor; Stehrer, T.; Pauser, H.

2013-01-01

Roč. 33, č. 3 (2013), s. 593-604 ISSN 0272-4324 R&D Projects: GA ČR GAP205/11/2070 Institutional support: RVO:61389021 Keywords : Plasma arc cutting * Optical emission spectroscopy * Plasma temperature * Steam torch Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.599, year: 2013 http://link.springer.com/content/pdf/10.1007%2Fs11090-013-9443-y.pdf

Reheating experiment in the 35-ton pile; Experience de rechauffage sur la pile de 35 tonnes

Energy Technology Data Exchange (ETDEWEB)

Cherot, J; Girard, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

When the 35-ton pile was started up it was necessary for us, in order to study certain effects (xenon for example), to know the anti reactivity value of the rods as a function of their dimensions. We have made use of the possibility, in the reheating experiment, of raising the temperature of the graphite-uranium block by simple heating, in order to determine the anti reactivity curves of the rods, and from that the overall temperature coefficient. For the latter we have considered two solutions: first, one in which the average temperature of the pile is defined as our arithmetical mean of the different values given by the 28 thermocouples distributed throughout the pile; a second in which the temperature in likened to a poisoning and is balanced by the square of the flux. The way in which the measurements have been made is indicated, and the different instruments used are described. The method of reheating does not permit the separation of the temperature coefficients of uranium and of graphite. The precision obtained is only moderate, and suffers from the changes of various parameters necessary to other manipulations carried out simultaneously (life time modulators for example), and finally it is a function of the comparatively restricted time allowed. It is evident of course that more careful stabilisation at the different plateaux chosen would have necessitated long periods of reheating. (author) [French] Nous avions besoin lors de la montee en puissance de la pile de 35 tonnes, pour l'elude de divers effets (xenon par ex.) de la valeur de l'antireactivite des barres en fonction de leurs cotes. Nous avons profite dans l'experience rechauffage de la possibilite de monter en temperature, non nucleairement, le bloc graphite uranium, pour determiner les courbes d'antireactivite des barres et de la le coefficient global de temperature. Nous avons considere pour ce dernier deux solutions. Une premiere dans laquelle la temperature moyenne de la pile est definie comme

Temperature profiles in a steam-liquid sodium jet. Application to wastage

International Nuclear Information System (INIS)

Park, K.H.

1983-12-01

The first part of this work presents a certain number of recalls concerning wastage, jets, sonic jets, turbulent jets reactive or not. The aim of this thesis is to group the theoretical formulas concerning gaseous jets in liquids, to determine from experiments the temperature distributions inside the reactive jet, and to establish correlations between the theory and the experiments carried out to obtain a model representative of the temperature distribution in steam jets into liquid sodium. The theoretical development is presented (differential and integral approaches), as also the experiments (JONAS) developed to determine the temperature distribution. The field of validity of experiments and approximations is then defined in view of application to wastage [fr

AREVA Modular Steam Cycle – High Temperature Gas-Cooled Reactor Development Progress

International Nuclear Information System (INIS)

Lommers, L.; Shahrokhi, F.; Southworth, F.; Mayer, J. III

2014-01-01

The AREVA Steam Cycle – High Temperature Gas-Cooled Reactor (SCHTGR) is a modular graphite-moderated gas-cooled reactor currently being developed to support a wide variety of applications including industrial process heat, high efficiency electricity generation, and cogeneration. It produces high temperature superheated steam which makes it a good match for many markets currently dependent on fossil fuels for process heat. Moreover, the intrinsic safety characteristics of the SC-HTGR make it uniquely qualified for collocation with large industrial process heat users which is necessary for serving these markets. The NGNP Industry Alliance has selected the AREVA SC-HTGR as the basis for future development work to support commercial HTGR deployment. This paper provides a concise description of the SC-HTGR concept, followed by a summary of recent development activities. Since this concept was introduced, ongoing design activities have focused primarily on confirming key system capabilities and the suitability for potential future markets. These evaluations continue to confirm the suitability of the SC-HTGR for a variety of potential applications that are currently dependent on fossil fuels. (author)

Techno-economic study of hydrogen production by high temperature electrolysis coupled with an EPR-water steam production and coupling possibilities

International Nuclear Information System (INIS)

Tinoco, R. R.; Bouallou, C.; Mansilla, C.; Werkoff, F.

2007-01-01

Nuclear reactors present a wide range of coupling possibilities with several industrial processes, hydrogen production being one of them. Among the Pressurised Water nuclear Reactors (PWR), the new European Pressurised Reactor (EPR) offers the water steam production at low-medium temperatures, from 230 degree Celsius to 330 degree Celsius for the primary and secondary exchange circuits. The use of this water steam for hydrogen production by High Temperature Electrolysis is the subject of this study, under a French context. The study of this coupling, has considered two hypotheses. First, water steam drawing off in secondary circuit has been evaluated in terms of possible impact in electricity production and reactor availability. After the drawing off at 78 bar (EPR secondary circuit pressure), pressure has to be dropped in order to protect the high temperature electrolyser from damage, so an isenthalpic drop has been considered. Liquid-vapour equilibrium happens with pressure drops, so separation of gas phase and recycling of liquid phase are proposed. Second, only water steam production with an EPR has been evaluated. The feed water enters the secondary circuit and passes from liquid phase to vapour in the steam generators, and then all steam is canalized to the high temperature electrolyser. The potentiality of water steam production in the EPR has been evaluated from 15 to 40 bar. Small reactors could be the best choice if only water steam production is considered. After steam production, it steam enters into the High Temperature Electrolysis process, like a cold stream for two parallel series of three heat exchangers reaching temperatures up to 950 degree Celsius. Then the steam is heated by an electric device and finally it enters the electrolyser. The electrolysis product streams (hydrogen-steam mixture and oxygen) are used in the heat exchangers like hot streams. For both hypotheses, information about water composition has been studied in order to minimise

Low Temperature Steam Methane Reforming Over Ni Based Catalytic Membrane Prepared by Electroless Palladium Plating.

Science.gov (United States)

Lee, Sang Moon; Hong, Sung Chang; Kim, Sung Su

2018-09-01

A Pd/Ni-YSZ porous membrane with different palladium loadings and hydrazine as a reducing reagent was prepared by electroless plating and evaluated for the steam methane reforming activity. The steam-reforming activity of a Ni-YSZ porous membrane was greatly increased by the deposition of 4 g/L palladium in the low-temperature range (600 °C). With an increasing amount of reducing reagent, the Pd clusters were well dispersed on the Ni-YSZ surface and were uniform in size (∼500 nm). The Pd/Ni-YSZ catalytic porous membrane prepared by 1 of Pd/hydrazine ratio possessed an abundant amount of metallic Pd. The optimal palladium loadings and Pd/hydrazine ratio increased the catalytic activity in both the steam-reforming reaction and the Pd dispersion.

Temperature escalation in PWR fuel rod simulator bundles due to the Zircaloy/steam reaction: Test ESBU-2A

International Nuclear Information System (INIS)

Hagen, S.; Kapulla, H.; Malauschek, H.; Wallenfels, K.P.; Peck, S.O.

1984-07-01

This report describes the test conduct and results of the bundle test ESBU-2A, which was run to investigate the temperature escalation of zircaloy clad fuel rods. This investigation of temperature escalation is part of a series of out-of-pile experiments, performed within the framework of the PNS Severe Fuel Damage Program. The test bundle was of a 3 x 3 array of fuel rod simulators with a 0.4 m heated length. The fuel rod simulators were electrically heated and consisted of tungsten heaters, UO 2 annular pellets, and zircaloy cladding. A nominal steam flow of 0.7 g/s was inlet to the bundle. The bundle was surrounded by a zircaloy shroud which was insulated with ZrO 2 fiber ceramic wrap. The initial heatup rate of the bundle was 0.4 0 C/s. The temperature escalation began at the 255 mm elevation after 1200 0 C had been reached. At this elevation, the measured peak temperature was limited to 1500 0 C. It was concluded from different thermocouple results, that induced by this first escalation melt was formed in the lower part of the bundle. Consequently, the escalation in the lower part must be much higher, at least up to the melting temperature of zircaloy. Due to the failure in the steam production system, steam starvation in the upper region may explain the beginning of the escalation at the 255 mm elevation. The maximum temperature reached was 2175 0 C on the center rod at the end of the test. The unregularities in the steam supply may be the reason for less oxidation than expected. (orig./GL) [de

Condensation front modelling in a moisture separator reheater by application of SICLE numerical model

International Nuclear Information System (INIS)

Grange, J.L.; Caremoli, C.; Eddi, M.

1988-01-01

This paper presents improvements performed on SICLE numerical model in order to analyse the condensation front that occurs in the moisture separator reheaters (MSR) of nuclear power plants. Modifications of SICLE numerical model architecture and a fine modelling of reheater have allowed to correctly simulate the MSR thermohydraulic behaviour during a severe transient (plant islanding) [fr

Experimental and Numerical Study of Low Temperature Methane Steam Reforming for Hydrogen Production

Directory of Open Access Journals (Sweden)

Martin Khzouz

2017-12-01

Full Text Available Low temperature methane steam reforming for hydrogen production, using experimental developed Ni/Al2O3 catalysts is studied both experimentally and numerically. The catalytic activity measurements were performed at a temperature range of 500–700 °C with steam to carbon ratio (S/C of 2 and 3 under atmospheric pressure conditions. A mathematical analysis to evaluate the reaction feasibility at all different conditions that have been applied by using chemical equilibrium with applications (CEA software and in addition, a mathematical model focused on the kinetics and the thermodynamics of the reforming reaction is introduced and applied using a commercial finite element analysis software (COMSOL Multiphysics 5.0. The experimental results were employed to validate the extracted simulation data based on the yields of the produced H2, CO2 and CO at different temperatures. A maximum hydrogen yield of 2.7 mol/mol-CH4 is achieved at 700 °C and S/C of 2 and 3. The stability of the 10%Ni/Al2O3 catalyst shows that the catalyst is prone to deactivation as supported by Thermogravimetric Analysis TGA results.

Multitechnique characterisation of 304L surface states oxidised at high temperature in steam and air atmospheres

Energy Technology Data Exchange (ETDEWEB)

Mamede, Anne-Sophie, E-mail: anne-sophie.mamede@ensc-lille.fr [University Lille, CNRS, ENSCL, Centrale Lille, University Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, F-59000 Lille (France); Nuns, Nicolas, E-mail: nicolas.nuns@univ-lille1.fr [University Lille, CNRS, ENSCL, Centrale Lille, University Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, F-59000 Lille (France); Cristol, Anne-Lise, E-mail: anne-lise.cristol@ec-lille.fr [University Lille, CNRS, Centrale Lille, Arts et Métiers Paris Tech, FRE 3723 – LML – Laboratoire de Mécanique de Lille, F-59000 Lille (France); Cantrel, Laurent, E-mail: laurent.cantrel@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire, PSN-RES, Cadarache, Saint Paul lez Durance, 13115 (France); Laboratoire de Recherche Commun IRSN-CNRS-Lille 1: «Cinétique Chimique, Combustion, Réactivité» (C3R), Cadarache, Saint Paul lez Durance, 13115 (France); Souvi, Sidi, E-mail: sidi.souvi@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire, PSN-RES, Cadarache, Saint Paul lez Durance, 13115 (France); Laboratoire de Recherche Commun IRSN-CNRS-Lille 1: «Cinétique Chimique, Combustion, Réactivité» (C3R), Cadarache, Saint Paul lez Durance, 13115 (France); and others

2016-04-30

Graphical abstract: - Highlights: • Mutitechnique characterisation of oxidised 304L. • Oxidation at high temperature under steam and air conditions of 304L stainless steel. • Chromium and manganese oxides formed in the outer layer. • Oxide profiles differ in air or steam atmosphere. - Abstract: In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8–12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe{sub 2}O{sub 3} oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data.

Effects of chemistry on corrosion-erosion of steels in water and wet steam

International Nuclear Information System (INIS)

Berge, P.; Ducreux, J.; Saint-Paul, P.

1981-01-01

In steam production plants, numerous cases of degradation of steels occur when in contact with water or wet steam circulating at high velocity: in feed or discharge pumps, water reheaters, etc. When the phenomenon occurs without any mechanical wear of the metal or the oxide from the impact of solid particles (abrasion) or droplets (erosion), it is called corrosion-erosion. The phenomenon usually occurs between 100 and 250 0 C, as has been confirmed by an empirical study of the thermal and hydraulic factors which govern it. Corrosion rates can reach 1 to 2 mm/year, for a carbon steel pipe where water treated with ammonia circulates at about pH 9, at 200 0 C, and at a velocity of 5 to 10 m/s. This study evaluates the part played by the factors solely connected to the chemistry of water, with respect to the kinetics of the corrosion-erosion phenomenon. (author)

Reheat cracking in austenitic stainless steels; Fissuration en relaxation des aciers inoxydables austenitiques

Energy Technology Data Exchange (ETDEWEB)

Auzoux, Q.; Allais, L. [CEA Saclay, Dept. des Materiaux pour le Nucleaire, DMN, 91 - Gif sur Yvette (France); Pineau, A.; Gourgues, A.F. [Centre des Materiaux Pierre-Marie Fourt UMR CNRS 7633, 91 - Evry (France)

2002-07-01

Intergranular cracking can occur in heat-affected zones (HAZs) of austenitic stainless steel welded joints when reheated in the temperature range from 500 to 700 deg C. At this temperature, residual stresses due to welding relax by creep flow. HAZ may not sustain this small strain if its microstructure has been sufficiently altered during welding. In order to precise which particular microstructure alteration causes such an intergranular embrittlement, type 316L(N) HAZs were examined by transmission electron microscopy. A marked increase in the dislocation density, due to plastic strain during the welding process, was revealed, which caused an increase in Vickers hardness. Type 316L(N) HAZ were then simulated by the following thermal-mechanical process: annealing treatment and work hardening (pre-strain). Creep rupture tests on smooth specimens were also carried out at 600 deg C on both base metal and simulated HAZ. Pre-straining increased creep strength but reduced ductility. Slow strain rate tests on CT specimens confirmed this trend as well as did relaxation tests on CT specimens, which led to intergranular crack propagation in the pre-strained material only. Metallography and fractography showed no qualitative difference between base metal and HAZs in the creep cavitation around intergranular carbides. Although quantitative study of damage development is not achieved yet, experiments suggest that uniaxial creep strain smaller than one percent could lead to cavity nucleation when the material is pre-strained. Pre-strain as well as stress triaxiality reduce therefore creep ductility and enhance the reheat cracking risk. (authors)

Exergy based parametric analysis of a combined reheat regenerative thermal power plant and water–LiBr vapor absorption refrigeration system

International Nuclear Information System (INIS)

Gogoi, T.K.; Talukdar, K.

2014-01-01

Highlights: • Exergy analysis of a combined power–absorption cooling system is provided. • Exergetic efficiency of the power cycle and absorption cooling system are calculated. • Irreversibility in each component and total system irreversibility are calculated. • Effect of operating parameters on exergetic performance and irreversibility is analyzed. • Optimum operating parameters are identified based on energy and exergy based results. - Abstract: In this paper, exergy analysis of a combined reheat regenerative steam turbine (ST) based power cycle and water–LiBr vapor absorption refrigeration system (VARS) is presented. Exergetic efficiency of the power cycle and VARS, energy utilization factor (EUF) of the combined system (CS) and irreversibility in each system component are calculated. The effect of fuel flow rate, boiler pressure, cooling capacity and VARS components’ temperature on performance, component and total system irreversibility is analyzed. The second law based results indicate optimum performance at 150 bar boiler pressure and VARS generator, condenser, evaporator and absorber temperature of 80 °C, 37.5 °C, 15 °C and 35 °C respectively. The present exergy based results conform well to the first law based results obtained in a previous analysis done on the same combined system. Irreversibility distribution among various power cycle components shows the highest irreversibility in the cooling tower. Irreversibility of the exhaust flue gas leaving the boiler and the boiler are the next major contributors. Among the VARS components, exergy destruction in the generator is the highest followed by irreversibility contribution of the absorber, condenser and the evaporator

HyPEP FY-07 Report: System Integration Model Development

Energy Technology Data Exchange (ETDEWEB)

C. H. Oh; E. S. Kim; S. R. Sherman; R. Vilim

2007-04-01

The integrated system of a Very High Temperature Gas-Cooled Reactor (VHTR) and a High Temperature Steam Electrolysis (HTSE) process is one of systems being investigated by the U.S. Department of Energy and Idaho National Laboratory. This system will produce hydrogen by utilizing a highly efficient VHTR with an outlet temperature of 900 °C and supplying necessary energy and electricity to the HTSE process for electrolysis of high temperature steam. This report includes a description of five configurations including an indirect parallel cycle, an indirect serial cycle, a direct serial cycle, a steam combined cycle, and a reheat cycle. HYSYS simulations were performed for each of these configurations coupled to a HTSE process. Final results are presented along with parametric studies and process optimization.

SURGTANK, Steam Pressure, Saturation Temperature or Reactor Surge Tank

International Nuclear Information System (INIS)

Gorman, D.J.; Gupta, R.K.

2001-01-01

1 - Description of problem or function: SURGTANK generates the steam pressure, saturation temperature, and ambient temperature history for a nuclear reactor steam surge tank (pressurizer) in a state of thermodynamic equilibrium subjected to a liquid insurge described by a specified time history of liquid levels. It is capable also of providing the pressure and saturation temperature history, starting from thermodynamic equilibrium conditions, for the same tank subjected to an out-surge described by a time history of liquid levels. Both operations are available for light- or heavy- water nuclear reactor systems. The tank is assumed to have perfect thermal insulation on its outer wall surfaces. 2 - Method of solution: Surge tank geometry and initial liquid level and saturation pressure are provided as input for the out-surge problem, along with the prescribed time-sequence level history. SURGTANK assumes a reduced pressure for the end of the first change in liquid level and determines the associated change of entropy for the closed system. The assumed pressure is adjusted and the associated change in entropy recalculated until a pressure is attained for which no change occurs. This pressure is recorded and used as the beginning pressure for the next level increment. The system is then re-defined to exclude the small amount of liquid which has left the tank, and a solution for the pressure at the end of the second level increment is obtained. The procedure is terminated when the pressure at the end of the final increment has been determined. Surge tank geometry, thermal conductivity, specific heat, and density of tank walls, initial liquid level, and saturation pressure are provided as input for the insurge problem, along with the prescribed time-sequence level history. SURGTANK assumes a slightly in- creased pressure for the end of the first level, the inner tank sur- face is assumed to follow saturation temperature, linearly with time, throughout the interval, and

Variable electricity and steam from salt, helium and sodium cooled base-load reactors with gas turbines and heat storage - 15115

International Nuclear Information System (INIS)

Forsberg, C.; McDaniel, P.; Zohuri, B.

2015-01-01

Advances in utility natural-gas-fired air-Brayton combed cycle technology is creating the option of coupling salt-, helium-, and sodium-cooled nuclear reactors to Nuclear air-Brayton Combined Cycle (NACC) power systems. NACC may enable a zero-carbon electricity grid and improve nuclear power economics by enabling variable electricity output with base-load nuclear reactor operations. Variable electricity output enables selling more electricity at times of high prices that increases plant revenue. Peak power is achieved using stored heat or auxiliary fuel (natural gas, bio-fuels, hydrogen). A typical NACC cycle includes air compression, heating compressed air using nuclear heat and a heat exchanger, sending air through a turbine to produce electricity, reheating compressed air, sending air through a second turbine, and exhausting to a heat recovery steam generator (HRSG). In the HRSG, warm air produces steam that is used to produce added electricity. For peak power production, auxiliary heat (natural gas, stored heat) is added before the air enters the second turbine to raise air temperatures and power output. Like all combined cycle plants, water cooling requirements are dramatically reduced relative to other power cycles because much of the heat rejection is in the form of hot air. (authors)

An experimental investigation of the isochoric heat capacity of superheated steam and mixtures of superheated steam and hydrogen gas

International Nuclear Information System (INIS)

Nowak, E.S.; Chan, J.S.

1975-01-01

Measurements on the specific heat at constant volume of superheated steam and hydrogen gas mixtures at concentrations varying from 1.6 to 0.8 moles of water vapor per mole of hydrogen gas were made for temperatures ranging from 240 to 400 deg C. It was found that the experimental specific heat values of the mixtures are in good agreement with the ideal mixture values only near the saturation temperature of steam. The difference between the measured and the calculated ideal mixture values is a function of temperature, pressure and composition varying from about 11 to 24% at conditions far removed from the saturation temperature of steam. This indicates the heat of mixing is of significance in the steam-hydrogen system

Effect of Dynamic Reheating Induced by Weaving on the Microstructure of GTAW Weld Metal of 25% Cr Super Duplex Stainless Steel Weld Metal

Directory of Open Access Journals (Sweden)

Hee-Joon Sung

2017-11-01

Full Text Available The importance of the additional growth and/or transformation of the austenite phase that occurs in weld metals of super duplex stainless steel upon reheating is known. However, the effects have not been fully investigated, especially with respect to reheating induced by weaving during single-pass welding. In this work, bead-on-pipe gas tungsten arc welding (GTAW was conducted on super duplex stainless steel to understand the effect of weaving on the microstructure of weld metal. Microstructural analysis, electron backscatter diffraction (EBSD, and focused ion beam transmission electron microscopy (FIB-TEM were carried out to investigate the relationship between weaving and microstructural change. The weaving of GTAW produced a dynamic reheated area just before the weld bead during welding. It was revealed that extensive reheated weld existed even after one welding pass, and that the content of the austenite phase in the reheated area was higher than that in the non-reheated area, indicating the existence of a large quantity of intragranular austenite phase. In addition, the Cr2N content in the reheated area was lower than that in the non-reheated area. This reduction of Cr2N was closely related to the reheating resulting from weaving. TEM analysis revealed that Cr2N in the non-reheated area was dispersed following heating and transformed to secondary austenite.

Optimal set values of zone modeling in the simulation of a walking beam type reheating furnace on the steady-state operating regime

International Nuclear Information System (INIS)

Yang, Zhi; Luo, Xiaochuan

2016-01-01

Highlights: • The adjoint equation is introduced to the PDE optimal control problem. • Lipschitz continuity for the gradient of the cost functional is derived. • The simulation time and iterations reduce by a large margin in the simulations. • The model validation and comparison are made to verify the proposed math model. - Abstract: In this paper, this study proposed a new method to solve the PDE optimal control problem by introducing the adjoint problem to the optimization model, which was used to get the reference values for the optimal furnace zone temperatures and the optimal temperature distribution of steel slabs in the reheating furnace on the steady-state operating regime. It was proved that the gradient of the cost functional could be written via the weak solution of this adjoint problem and then Lipschitz continuity of the gradient was derived. Model validation and comparison between the mathematics model and the experiment results indicated that the present heat transfer model worked well for the prediction of thermal behavior about a slab in the reheating furnace. Iterations and simulation time had shown a significant decline in the simulations of 20MnSi slab, and it was shown by numerical simulations for 0.4 m thick slabs that the proposed method was better applied in the medium and heavy plate plant, leading to better performance in terms of productivity, energy efficiency and other features of reheating furnaces.

Steam gasification of waste tyre: Influence of process temperature on yield and product composition

Energy Technology Data Exchange (ETDEWEB)

Portofino, Sabrina, E-mail: sabrina.portofino@enea.it [UTTP NANO – C.R. ENEA Portici, P.le E. Fermi, 1 Loc. Granatello, 80055 Portici (Italy); Donatelli, Antonio; Iovane, Pierpaolo; Innella, Carolina; Civita, Rocco; Martino, Maria; Matera, Domenico Antonio; Russo, Antonio; Cornacchia, Giacinto [UTTTRI RIF – C.R. ENEA Trisaia, SS Jonica 106, km 419.5, 75026 Rotondella (Italy); Galvagno, Sergio [UTTP NANO – C.R. ENEA Portici, P.le E. Fermi, 1 Loc. Granatello, 80055 Portici (Italy)

2013-03-15

Highlights: ► Steam gasification of waste tyre as matter and energy recovery treatment. ► Process temperature affects products yield and gas composition. ► High temperature promotes hydrogen production. ► Char exploitation as activated carbon or carbon source. - Abstract: An experimental survey of waste tyre gasification with steam as oxidizing agent has been conducted in a continuous bench scale reactor, with the aim of studying the influence of the process temperature on the yield and the composition of the products; the tests have been performed at three different temperatures, in the range of 850–1000 °C, holding all the other operational parameters (pressure, carrier gas flow, solid residence time). The experimental results show that the process seems promising in view of obtaining a good quality syngas, indicating that a higher temperature results in a higher syngas production (86 wt%) and a lower char yield, due to an enhancement of the solid–gas phase reactions with the temperature. Higher temperatures clearly result in higher hydrogen concentrations: the hydrogen content rapidly increases, attaining values higher than 65% v/v, while methane and ethylene gradually decrease over the range of the temperatures; carbon monoxide and dioxide instead, after an initial increase, show a nearly constant concentration at 1000 °C. Furthermore, in regards to the elemental composition of the synthesis gas, as the temperature increases, the carbon content continuously decreases, while the oxygen content increases; the hydrogen, being the main component of the gas fraction and having a small atomic weight, is responsible for the progressive reduction of the gas density at higher temperature.

Temperature fields induced by direct contact condensation of steam in a cross-flow in a channel

NARCIS (Netherlands)

Clerx, N.; van Deurzen, L.G.M.; Pecenko, A.; Liew, R.; van der Geld, C.W.M.; Kuerten, Johannes G.M.

2011-01-01

The temperature fields in the center plane of a channel with a square cross-section have been measured. Steam injected at relatively low mass fluxes through a small hole in one of the walls of the channel condensed intermittently in a small area close to the inlet. The upstream temperature of the

Steam separator-superheater with drawing of a fraction of the dried steam

International Nuclear Information System (INIS)

Bessouat, Roger; Marjollet, Jacques.

1976-01-01

This invention concerns a vertical separator-superheater of the steam from a high pressure expansion turbine before it is admitted to an expansion turbine at a lower pressure, by heat exchange with steam under a greater pressure, and drawing of a fraction of the dried steam before it is superheated. Such drawing off is necessary in the heat exchange systems of light water nuclear reactors. Its purpose is to provide a separator-superheater that provides an even flow of non superheated steam and a regular distribution of the steam to be superheated to the various superheating bundles, with a significantly uniform temperature of the casing, thereby preventing thermal stresses and ensuring a minimal pressure drop. The vertical separator-superheater of the invention is divided into several vertical sections comprising as from the central area, a separation area of the steam entrained water and a superheater area and at least one other vertical section with only a separation area of the steam entrained water [fr

Antilisterial properties of marinades during refrigerated storage and microwave oven reheating against post-cooking inoculated chicken breast meat.

Science.gov (United States)

Fouladkhah, Aliyar; Geornaras, Ifigenia; Nychas, George-John; Sofos, John N

2013-02-01

This study evaluated growth of Listeria monocytogenes inoculated on cooked chicken meat with different marinades and survival of the pathogen as affected by microwave oven reheating. During aerobic storage at 7 °C, on days 0, 1, 2, 4, and 7, samples were reheated by microwave oven (1100 W) for 45 or 90 s and analyzed microbiologically. L. monocytogenes counts on nonmarinated (control) samples increased (P 2.4 to 5.0 (90 s) log CFU/g. With similar trends across different marinates, the high levels of L. monocytogenes survivors found after microwave reheating, especially after storage for more than 2 d, indicate that length of storage and reheating time need to be considered for safe consumption of leftover cooked chicken. © 2013 Institute of Food Technologists®

Steam injections wells: topics to consider in casing design of steam injection wells; Revestimento para pocos de vapor

Energy Technology Data Exchange (ETDEWEB)

Conceicao, Antonio Carlos Farias [PETROBRAS, Recife, PE (Brazil). Gerencia de Perfuracao do Nordeste. Div. de Operacoes

1994-07-01

Steam injection is one of the processes used to increase production from very viscous oil reservoirs. A well is completed at a temperature of about 110 deg F and during steam injection that temperature varies around 600 deg F. Strain or breakdowns may occur to the casing, due to the critical conditions generated by the change of temperature. The usual casing design methods, do not take into account special environmental conditions, such as those which exist for steam injection. From the results of this study we come up to the conclusion that casing grade K-55, heavy weight with premium connections, without pre-stressing and adequately heated, is the best option for steam injection well completion for most of the fields in Brazil. (author)

High temperature behaviour of E110G and E110 fuel claddings in various mixtures of steam and air

International Nuclear Information System (INIS)

Perez-Feró, Erzsébet; Novotny, Tamás; Horváth, Márta; Kunstár, Mihály; Vér, Nóra; Hózer, Zoltán

2014-01-01

Experiments with sponge base E110G and the traditional E110 were carried out to compare the oxidation kinetics of these alloys in steam, in hydrogen rich steam, in steam-air and in air atmosphere and to study the effect of hydrogen- and nitrogen-containing environment on the oxidation. The effect of oxidizing atmosphere on the mechanical behaviour of the claddings was also investigated. The new and the traditional types of cladding rings were oxidised at high temperature (600°C – 1200°C). Oxidation of both alloys in steam-air mixture and in air atmosphere resulted in faster oxidation kinetics compared to steam. In many cases bumpy, porous oxide layer have been found. The presence of hydrogen in the steam atmosphere had no significant effect on the oxidation kinetics. Comparing the two alloys, more favourable behaviour of oxidised E110G was observed regarding the oxidation kinetics, breakaway oxidation and load bearing capability in all cases. (author)

Steam jet mill-a prospective solution to industrial exhaust steam and solid waste.

Science.gov (United States)

Zhang, Mingxing; Chen, Haiyan

2018-04-20

Bulk industrial solid wastes occupy a lot of our resources and release large amounts of toxic and hazardous substances to the surrounding environment, demanding innovative strategies for grinding, classification, collection, and recycling for economically ultrafine powder. A new technology for grinding, classification, collection, and recycling solid waste is proposed, using the superheated steam produced from the industrial exhaust steam to disperse, grind, classify, and collect the industrial solid waste. A large-scale steam jet mill was designed to operate at an inlet steam temperature 230-300 °C and an inlet pressure of 0.2-0.6 MPa. A kind of industrial solid waste fluidized-bed combustion ashes was used to grinding tests at different steam temperatures and inlet pressures. The total process for grinding, classification, and collection is drying. Two kinds of particle sizes are obtained. One particle size is d 50  = 4.785 μm, and another particle size is d 50  = 8.999 μm. For particle size d 50  = 8.999 μm, the inlet temperature is 296 °C and an inlet pressure is 0.54 MPa for the grinding chamber. The steam flow is 21.7 t/h. The yield of superfine powder is 73 t/h. The power consumption is 3.76 kW h/t. The obtained superfine powder meets the national standard S95 slag. On the basis of these results, a reproducible and sustainable industrial ecological protocol using steam produced by industrial exhaust heat coupled to solid waste recycling is proposed, providing an efficient, large-scale, low-cost, promising, and green method for both solid waste recovery and industrial exhaust heat reutilization.

On high temperature strength of carbon steels

International Nuclear Information System (INIS)

Ichinose, Hiroyuki; Tamura, Manabu; Kanero, Takahiro; Ihara, Yoshihito

1977-01-01

In the steels for high temperature use, the oxidation resistance is regarded as important, but carbon steels show enough oxidation resistance to be used continuously at the temperature up to 500 deg. C if the strength is left out of consideration, and up to 450 deg. C even when the strength is taken into account. Moreover, the production is easy, the workability and weldability are good, and the price is cheap in carbon steels as compared with alloy steels. In the boilers for large thermal power stations, 0.15-0.30% C steels are used for reheater tubes, main feed water tubes, steam headers, wall water tubes, economizer tubes, bypass pipings and others, and they account for 70% of all steel materials used for the boilers of 350 MW class and 30% in 1000 MW class. The JIS standard for the carbon steels for high temperature use and the related standards in foreign countries are shown. The high temperature strength of carbon steels changes according to the trace elements, melting and heat treatment as well as the main compositions of C, Si and Mn. Al and N affect the high temperature strength largely. The characteristics of carbon steels after the heating for hours, the factors controlling the microstructure and high temperature strength, and the measures to improve the high temperature strength of carbon steels are explained. (Kako, I.)

Methods of increasing thermal efficiency of steam and gas turbine plants

Science.gov (United States)

Vasserman, A. A.; Shutenko, M. A.

2017-11-01

Three new methods of increasing efficiency of turbine power plants are described. Increasing average temperature of heat supply in steam turbine plant by mixing steam after overheaters with products of combustion of natural gas in the oxygen. Development of this idea consists in maintaining steam temperature on the major part of expansion in the turbine at level, close to initial temperature. Increasing efficiency of gas turbine plant by way of regenerative heating of the air by gas after its expansion in high pressure turbine and before expansion in the low pressure turbine. Due to this temperature of air, entering combustion chamber, is increased and average temperature of heat supply is consequently increased. At the same time average temperature of heat removal is decreased. Increasing efficiency of combined cycle power plant by avoiding of heat transfer from gas to wet steam and transferring heat from gas to water and superheated steam only. Steam will be generated by multi stage throttling of the water from supercritical pressure and temperature close to critical, to the pressure slightly higher than condensation pressure. Throttling of the water and separation of the wet steam on saturated water and steam does not require complicated technical devices.

Electrochemical performances of LSM/YSZ composite electrode for high temperature steam electrolysis

International Nuclear Information System (INIS)

Kyu-Sung Sim; Ki-Kwang Bae; Chang-Hee Kim; Ki-Bae Park

2006-01-01

The (La 0.8 Sr 0.2 ) 0.95 MnO 3 /Yttria-stabilized Zirconia composite electrodes were investigated as anode materials for high temperature steam electrolysis using X-ray diffractometry, scanning electron microscopy, galvano-dynamic and galvano-static polarization method. For this study, the LSM perovskites were fabricated in powders by the co-precipitation method and then were mixed with 8 mol% YSZ powders in different molar ratios. The LSM/YSZ composite electrodes were deposited on 8 mol% YSZ electrolyte disks by screen printing method, followed by sintering at temperature above 1100 C. From the experimental results, it is concluded that the electrochemical properties of pure and composite electrodes are closely related to their micro-structure and operating temperature. (authors)

Sodium and steam leak simulation studies for fluidized bed steam generators

International Nuclear Information System (INIS)

Keeton, A.R.; Vaux, W.G.; Lee, P.K.; Witkowski, R.E.

1976-01-01

An experimental program is described which was conducted to study the effects of sodium or steam leaking into an operating fluidized bed of metal or ceramic particles at 680 to 800 0 K. This effort was part of the early development studies for a fluidized-bed steam generator concept using helium as the fluidizing gas. Test results indicated that steam and small sodium leaks had no effect on the quality of fluidization, heat transfer coefficient, temperature distribution, or fluidizing gas pressure drop across the bed. Large sodium leaks, however, immediately upset the operation of the fluidized bed. Both steam and sodium leaks were detected positively and rapidly at an early stage of a leak by instruments specifically selected to accomplish this

Steam generating system in LMFBR type reactors

International Nuclear Information System (INIS)

Kurosawa, Katsutoshi.

1984-01-01

Purpose: To suppress the thermal shock loads to the structures of reactor system and secondary coolant system, for instance, upon plant trip accompanying turbine trip in the steam generation system of LMFBR type reactors. Constitution: Additional feedwater heater is disposed to the pipeway at the inlet of a steam generator in a steam generation system equipped with a closed loop extended from a steam generator by way of a gas-liquid separator, a turbine and a condensator to the steam generator. The separated water at high temperature and high pressure from a gas-liquid separator is heat exchanged with coolants flowing through the closed loop of the steam generation system in non-contact manner and, thereafter, introduced to a water reservoir tank. This can avoid the water to be fed at low temperature as it is to the steam generator, whereby the thermal shock loads to the structures of the reactor system and the secondary coolant system can be suppressed. (Moriyama, K.)

Separators/reheaters for nuclear turbines

International Nuclear Information System (INIS)

Guignard, S.

1986-01-01

During the past few years, the Nuclear Department of Stein Industrie has implemented a broad development programme for the design of superheating separators for nuclear power plant turbines. These units separate the water in the steam leaving the high-pressure section, and superheat the dry steam before expansion in the medium - and low - pressure sections. Thorough research, confirmed by tests, was conducted in different areas, and especially on problems of water and steam separation, and heat transfers in the tube bundle(s) required to superheat the steam. Special systems were designed to avoid processes detrimental to the operation of the units, such as vibrations, erosion/corrosion etc. Experimental feedback on the superheating separators of 900 MW nuclear power plants helped to substantiate the assumptions made for the thermal and hydraulic calculations, as well as the optimizations carried out on the different functions. These results confirmed the industrial application of the design methods to other superheating separators intended for 1300 MW nuclear power plants and for export [fr

R.B. pressure and temperature transient following main steam line break

International Nuclear Information System (INIS)

Das, M.; Bhawal, R.N.; Prakash, P.

1989-01-01

The R.B. containment plays an important role in mitigating the consequences of any accident core. The analysis of Main Steam Line Break (MSLB), though not of relevance from activity release considerations, is essentially from structural integrity point of view. In this paper the outline of the likely scenario is drawn and the approach for thermal hydraulic simulation of the system for carrying out transient blowdown analysis is discussed. The results of the containment pressure and temperature transient analysis are also presented. (author). 4 refs., 7 figs

Finite Element Modeling of Reheat Stretch Blow Molding of PET

Science.gov (United States)

Krishnan, Dwarak; Dupaix, Rebecca B.

2004-06-01

Poly (ethylene terephthalate) or PET is a polymer used as a packaging material for consumer products such as beverages, food or other liquids, and in other applications including drawn fibers and stretched films. Key features that make it widely used are its transparency, dimensional stability, gas impermeability, impact resistance, and high stiffness and strength in certain preferential directions. These commercially useful properties arise from the fact that PET crystallizes upon deformation above the glass transition temperature. Additionally, this strain-induced crystallization causes the deformation behavior of PET to be highly sensitive to processing conditions. It is thus crucial for engineers to be able to predict its performance at various process temperatures, strain rates and strain states so as to optimize the manufacturing process. In addressing these issues; a finite element analysis of the reheat blow molding process with PET has been carried out using ABAQUS. The simulation employed a constitutive model for PET developed by Dupaix and Boyce et al.. The model includes the combined effects of molecular orientation and strain-induced crystallization on strain hardening when the material is deformed above the glass transition temperature. The simulated bottles were also compared with actual blow molded bottles to evaluate the validity of the simulation.

Calculation of temperature fields formed in induction annealing of closing welded joint of jacket of steam generator for WWER 440 type nuclear power plant using ICL 2960 computer

International Nuclear Information System (INIS)

Sajnar, P.; Fiala, J.

1983-01-01

The problems are discussed of the mathematical description and simulation of temperature fields in annealing the closing weld of the steam generator jacket of the WWER 440 nuclear power plant. The basic principles are given of induction annealing, the method of calculating temperature fields is indicated and the mathematical description is given of boundary conditions on the outer and inner surfaces of the steam generator jacket for the computation of temperature fields arising during annealing. Also described are the methods of determining the temperature of exposed parts of heat exchange tubes inside the steam generator and the technical possibilities are assessed of the annealing equipment from the point of view of its computer simulation. Five alternatives are given for the computation of temperature fields in the area around the weld for different boundary conditions. The values are given of maximum differences in the temperatures of the metal in the annealed part of the steam generator jacket which allow the assessment of individual computation variants, this mainly from the point of view of observing the course of annealing temperature in the required width of the annealed jacket of the steam generator along both sides of the closing weld. (B.S.)

An Improved Steam Injection Model with the Consideration of Steam Override

Directory of Open Access Journals (Sweden)

He Congge

2017-01-01

Full Text Available The great difference in density between steam and liquid during wet steam injection always results in steam override, that is, steam gathers on the top of the pay zone. In this article, the equation for steam override coefficient was firstly established based on van Lookeren’s steam override theory and then radius of steam zone and hot fluid zone were derived according to a more realistic temperature distribution and an energy balance in the pay zone. On this basis, the equation for the reservoir heat efficiency with the consideration of steam override was developed. Next, predicted results of the new model were compared with these of another analytical model and CMG STARS (a mature commercial reservoir numerical simulator to verify the accuracy of the new mathematical model. Finally, based on the validated model, we analyzed the effects of injection rate, steam quality and reservoir thickness on the reservoir heat efficiency. The results show that the new model can be simplified to the classic model (Marx-Langenheim model under the condition of the steam override being not taken into account, which means the Marx-Langenheim model is corresponding to a special case of this new model. The new model is much closer to the actual situation compared to the Marx-Langenheim model because of considering steam override. Moreover, with the help of the new model, it is found that the reservoir heat efficiency is not much affected by injection rate and steam quality but significantly influenced by reservoir thickness, and to ensure that the reservoir can be heated effectively, the reservoir thickness should not be too small.

EFFECT OF STEAMING ON THE COLOUR CHANGE OF SOFTWOODS

Directory of Open Access Journals (Sweden)

Laszlo Tolvaj,

2012-05-01

Full Text Available The heat treatment of softwood (i.e. spruce, pine, fir, and larch may result in significant colour changes. During this study Scots pine and spruce samples were steamed and analysed for their altered hue and lightness. Treatments included: 0 to 22 days of steaming time at a temperature range of 70 to 100°C. The outcome included a variety of colours between the initial hues and brownish tint. These new colours are similar to that of aged furniture and indoor wooden structures. Consequently, properly steamed softwood may be used to repair historical artefacts and relic furniture. Besides restoration, steamed stocks are excellent sources for manufacture of periodical furniture, where the aged appearance has aesthetical value. Results however, indicated that steaming at a temperature above 90 ˚C has a bleaching effect, i.e. the coloured chemical components formed by moderate steaming may be removed. Furthermore, we observed a linear correlation between lightness and colour hue at all steaming times and temperatures.

1000 MW steam turbine for Temelin nuclear power station

International Nuclear Information System (INIS)

Drahy, J.

1992-01-01

Before the end 1991 the delivery was completed of the main parts (3 low-pressure sections and 1 high-pressure section, all of double-flow design) of the first full-speed (3000 r.p.m.) 1000 MW steam turbine for saturated admission steam for the Temelin nuclear power plant. Description of the turbine design and of new technologies and tools used in the manufacture are given. Basic technical parameters of the steam turbine are as follows: maximum output of steam generators 6060 th -1 ; maximum steam flow into turbine 5494.7 th -1 ; output of turbo-set 1024 MW; steam conditions before the turbine inlet: pressure 5.8 MPa, temperature 273.3 degC, steam wetness 0.5%; nominal temperature of cooling water 21 degC; temperature of feed water 220.8 degC; maximum consumption of heat from turbine for heating at 3-stage heating of heating water 60/150 degC. (Z.S.) 7 figs., 2 refs

High Temperature Monitoring the Height of Condensed Water in Steam Pipes

Science.gov (United States)

Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; Badescu, Mircea; Bao, Xiaoqi; Sherrit, Stewart; Widholm, Scott; Ostlund, Patrick; Blosiu, Julian

2011-01-01

An in-service health monitoring system is needed for steam pipes to track through their wall the condensation of water. The system is required to measure the height of the condensed water inside the pipe while operating at temperatures that are as high as 250 deg. C. The system needs to be able to make real time measurements while accounting for the effects of cavitation and wavy water surface. For this purpose, ultrasonic wave in pulse-echo configuration was used and reflected signals were acquired and auto-correlated to remove noise from the data and determine the water height. Transmitting and receiving the waves is done by piezoelectric transducers having Curie temperature that is significantly higher than 250 deg. C. Measurements were made at temperatures as high as 250 deg. C and have shown the feasibility of the test method. This manuscript reports the results of this feasibility study.

A Histological Analysis of Visceral Organs to Evaluate the Effect of Duration of Heating From Refrigeration to Core Body Temperature for Ballistics Investigations.

Science.gov (United States)

Humphrey, Caitlin; Kumaratilake, Jaliya

2017-12-01

Animal organs have been used in ballistics research to investigate the effects on human organs. Such organs are refrigerated until the investigation to minimize autolytic degradation and at times have been reheated to the human core body temperature to simulate the in situ environment. The aim of this investigation was to study the microstructural changes that may occur in fresh chilled visceral organs of the thorax and abdomen (ie, heart, lung, liver, and kidney) during the period of reheating to 37°C. Fifty-millimeter cubes of porcine heart, lung, liver, and kidney were taken rapidly after slaughter, chilled overnight, and the next morning were reheated to core body temperature (37°C). Histological changes occurring in the tissues during the reheating phase were investigated. The findings indicated that no cytoplasmic or nuclear changes occurred in any of the tissues during the period of reheating. Therefore, reheating of animal organs to the human core body temperature is not necessary, if the organs are refrigerated.

Reciprocating wear in a steam environment

Energy Technology Data Exchange (ETDEWEB)

Brown, L.J.; Gee, M.G. [National Physical Laboratory, Teddington, Middlesex (United Kingdom)

2010-07-01

Tests to simulate the wear between sliding components in steam power plant have been performed using a low frequency wear apparatus at elevated temperatures under static load, at ambient pressure, in a steam environment. The apparatus was modified to accept a novel method of steam delivery. The materials tested were pre-exposed in a flowing steam furnace at temperature for either 500 or 3000 hours to provide some simulation of long term ageing. The duration of each wear test was 50 hours and tests were also performed on as-received material for comparison purposes. Data has been compared with results of tests performed on non-oxidised material for longer durations and also on tests without steam to examine the effect of different environments. Data collected from each test consists of mass change, stub height measurement and friction coefficient as well as visual inspection of the wear track. Within this paper, it is reported that both pre-ageing and the addition of steam during testing clearly influence the friction between material surfaces. (orig.)

Steam reforming of commercial ultra-low sulphur diesel

Energy Technology Data Exchange (ETDEWEB)

Boon, J.; Van Dijk, E.; De Munck, S.; Van den Brink, R. [Energy research Centre of The Netherlands, ECN Hydrogen and Clean Fossil Fuels, P.O. Box 1, NL1755ZG Petten (Netherlands)

2011-03-11

Two main routes for small-scale diesel steam reforming exist: low-temperature pre-reforming followed by well-established methane steam reforming on the one hand and direct steam reforming on the other hand. Tests with commercial catalysts and commercially obtained diesel fuels are presented for both processes. The fuels contained up to 6.5 ppmw sulphur and up to 4.5 vol.% of biomass-derived fatty acid methyl ester (FAME). Pre-reforming sulphur-free diesel at around 475C has been tested with a commercial nickel catalyst for 118 h without observing catalyst deactivation, at steam-to-carbon ratios as low as 2.6. Direct steam reforming at temperatures up to 800C has been tested with a commercial precious metal catalyst for a total of 1190 h with two catalyst batches at steam-to-carbon ratios as low as 2.5. Deactivation was neither observed with lower steam-to-carbon ratios nor for increasing sulphur concentration. The importance of good fuel evaporation and mixing for correct testing of catalysts is illustrated. Diesel containing biodiesel components resulted in poor spray quality, hence poor mixing and evaporation upstream, eventually causing decreasing catalyst performance. The feasibility of direct high temperature steam reforming of commercial low-sulphur diesel has been demonstrated.

Steam reforming of commercial ultra-low sulphur diesel

Science.gov (United States)

Boon, Jurriaan; van Dijk, Eric; de Munck, Sander; van den Brink, Ruud

Two main routes for small-scale diesel steam reforming exist: low-temperature pre-reforming followed by well-established methane steam reforming on the one hand and direct steam reforming on the other hand. Tests with commercial catalysts and commercially obtained diesel fuels are presented for both processes. The fuels contained up to 6.5 ppmw sulphur and up to 4.5 vol.% of biomass-derived fatty acid methyl ester (FAME). Pre-reforming sulphur-free diesel at around 475 °C has been tested with a commercial nickel catalyst for 118 h without observing catalyst deactivation, at steam-to-carbon ratios as low as 2.6. Direct steam reforming at temperatures up to 800 °C has been tested with a commercial precious metal catalyst for a total of 1190 h with two catalyst batches at steam-to-carbon ratios as low as 2.5. Deactivation was neither observed with lower steam-to-carbon ratios nor for increasing sulphur concentration. The importance of good fuel evaporation and mixing for correct testing of catalysts is illustrated. Diesel containing biodiesel components resulted in poor spray quality, hence poor mixing and evaporation upstream, eventually causing decreasing catalyst performance. The feasibility of direct high temperature steam reforming of commercial low-sulphur diesel has been demonstrated.

Steam explosion studies review

International Nuclear Information System (INIS)

Hwang, Moon Kyu; Kim, Hee Dong

1999-03-01

When a cold liquid is brought into contact with a molten material with a temperature significantly higher than the liquid boiling point, an explosive interaction due to sudden fragmentation of the melt and rapid evaporation of the liquid may take place. This phenomenon is referred to as a steam explosion or vapor explosion. Depending upon the amount of the melt and the liquid involved, the mechanical energy released during a vapor explosion can be large enough to cause serious destruction. In hypothetical severe accidents which involve fuel melt down, subsequent interactions between the molten fuel and coolant may cause steam explosion. This process has been studied by many investigators in an effort to assess the likelihood of containment failure which leads to large scale release of radioactive materials to the environment. In an effort to understand the phenomenology of steam explosion, extensive studies has been performed so far. The report presents both experimental and analytical studies on steam explosion. As for the experimental studies, both small scale tests which involve usually less than 20 g of high temperature melt and medium/large scale tests which more than 1 kg of melt is used are reviewed. For the modelling part of steam explosions, mechanistic modelling as well as thermodynamic modelling is reviewed. (author)

Study of the combined plant for the generator diesel engine; Hatsudenki diesel engine no combined plant no kenkyu

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, Y [Kumamoto Institute of Technology, Kumamoto (Japan); Hanada, S; Watase, M; Nakajima, T

1997-10-01

It is intended to recover more effectively thermal energy currently discharged from marine vessels into air. This paper describes a diesel engine combined power generation system in which medium-order waste heat energy from a diesel engine for power generation in a marine vessel is recovered and utilized to operate a Rankine cycle system (using the waste gas as the high temperature source and sea water as the low temperature source), thus the thermal energy is recovered as a motive force. Two kinds of fluorocarbons and steam were discussed as a working fluid. Due to fluorocarbons making the whole system ultra-high in pressure, and from a viewpoint of high-temperature thermal stability, the temperature was remained at levels from 100 to 200 degC, and a single-stage expansion cycle was used. With the use of steam, a two-stage reheating cycle was employed, by which the temperature is raised fully up to 300 degC and effective head of fluid was taken largely. Ceramic paint was used as a means to prevent sulfur oxide corrosion when the system is used down to the dew point, and its effectiveness was verified. Motive force recovered by combining the steam two-stage reheating cycle and the ceramic painted heat collector was calculated, whereas electric power output of about 45 kW was obtained from a main generator with 450 PS. The derived thermal efficiency was about 26%. 2 refs., 24 figs., 2 tabs.

Potential use of high-temperature and low-temperature steam ...

African Journals Online (AJOL)

The effectiveness of different treatment methods to improve the nutritional value of the sugarcane by-products (pith or bagasse) has been evaluated. The treatment methods included a high-pressure steam treatment (HPST; 19 bar, 3 min), treating the products with sodium hydroxide, sulphuric acid plus an enzyme mixture, ...

J-resistance curves for Inconel 690 and Incoloy 800 nuclear steam generators tubes at room temperature and at 300 °C

Energy Technology Data Exchange (ETDEWEB)

Bergant, Marcos A., E-mail: marcos.bergant@cab.cnea.gov.ar [Gerencia CAREM, Centro Atómico Bariloche (CNEA), Av. Bustillo 9500, San Carlos de Bariloche 8400 (Argentina); Yawny, Alejandro A., E-mail: yawny@cab.cnea.gov.ar [División Física de Metales, Centro Atómico Bariloche (CNEA) / CONICET, Av. Bustillo 9500, San Carlos de Bariloche 8400 (Argentina); Perez Ipiña, Juan E., E-mail: juan.perezipina@fain.uncoma.edu.ar [Grupo Mecánica de Fractura, Universidad Nacional del Comahue / CONICET, Buenos Aires 1400, Neuquén 8300 (Argentina)

2017-04-01

The structural integrity of steam generator tubes is a relevant issue concerning nuclear plant safety. In the present work, J-resistance curves of Inconel 690 and Incoloy 800 nuclear steam generator tubes with circumferential and longitudinal through wall cracks were obtained at room temperature and 300 °C using recently developed non-standard specimens' geometries. It was found that Incoloy 800 tubes exhibited higher J-resistance curves than Inconel 690 for both crack orientations. For both materials, circumferential cracks resulted into higher fracture resistance than longitudinal cracks, indicating a certain degree of texture anisotropy introduced by the tube fabrication process. From a practical point of view, temperature effects have found to be negligible in all cases. The results obtained in the present work provide a general framework for further application to structural integrity assessments of cracked tubes in a variety of nuclear steam generator designs. - Highlights: •Non-standard fracture specimens were obtained from nuclear steam generator tubes. •Specimens with circumferential and longitudinal through-wall cracks were used. •Inconel 690 and Incoloy 800 steam generator tubes were tested at 24 and 300 °C. •Fracture toughness for circumferential cracks was higher than for longitudinal cracks. •Incoloy 800 showed higher fracture toughness than Inconel 690 steam generator tubes.

Condensation of the steam in the horizontal steam line during cold water flooding

International Nuclear Information System (INIS)

Strubelj, L.; Tiselj, I.

2006-01-01

Direct contact condensation and condensation induced water-hammer in a horizontal pipe was experimentally investigated at PMK-2 test facility of the Hungarian Atomic Energy Research Institute KFKI. The experiment is preformed in the horizontal section of the steam line of the PMK-2 integral test facility. As liquid water floods the horizontal part of the pipeline, the counter current horizontally stratified flow is being observed. During the flooding of the steam line, the vapour-liquid interface area increases and therefore the vapour condensation rate and the vapour velocity also increase. Similar phenomena can occur in the cold/hot leg of the primary loop of PWR nuclear power plant during loss of coolant accident, when emergency core cooling system is activated. Water level at one cross-section and four local void fraction and temperature at the top of steam line was measured and compared with simulation. Condensed steam increases the water temperature that is why the local temperature measurements are the most important information, from which condensation rate can be estimated, since mass of condensed steam was not measured. Free surface simulation of the experiment with thermal phase change model is presented. Surface renewal concept with small eddies is used for calculation of heat transfer coefficient. With surface renewal theory we did not get results similar to experiment, that is why heat transfer coefficient was increased by factor 20. In simulation with heat transfer coefficient calculated with surface renewal concept bubble entrapment is due to reflection of the wave from the end of the pipe. When heat transfer coefficient is increased, condensation rate and steam velocity are also increased, bubble entrapment is due to Kelvin-Helmholtz instability of the free surface, and the results become similar to the measurements. (author)

Oxidation-induced deformation of zircaloy-4 tubing in steam in the temperature range 600-1000 degree C

International Nuclear Information System (INIS)

Aly, A.E.; Hussein, A.G.; EL-Raghy, S.M.; EL-Sayed, A.A.; EL-Banna, O.A.

1992-01-01

The oxidation-induced deformation of zircaloy-4 (zry-4) tubing in steam has been studied in the temperature range 600 to 1000 degree C. The induced deformation has been measured in both radial and axial directions of the tube. The effect of hydrogen addition to steam was also investigated. The oxidation-induced deformation has been characterized by uniform and non-uniform (distortion) strain period. During the uniform strain period the radial strain kinetics were found in general, to be parallel to the oxidation kinetics. The axial strain (δA) induced by oxidation was found to be always lower than the radial strain (εR). The addition of 5% by volume hydrogen to steam leads to an increase in the oxidation rate and to a decrease in the degree of anisotropy between radial and axial strains

Oxidation of 304 stainless steel in high-temperature steam

Science.gov (United States)

Ishida, Toshihisa; Harayama, Yasuo; Yaguchi, Sinnosuke

1986-08-01

An experiment on oxidation of 304 stainless steel was performed in steam between 900°C and 1350°C, using the spare cladding of the reactor of the nuclear-powered ship Mutsu. The temperature range was appropriate for a postulated loss of coolant accident (LOCA) analysis of a LWR. The oxidation kinetics were found to obey the parabolic law during the first period of 8 min. After the first period, the parabolic reaction rate constant decreased in the case of heating temperatures between 1100°C and 1250°C. At 1250°C, especially, a marked decrease was observed in the oxide scale-forming kinetics when the surface treated initially by mechanical polishing and given a residual stress. This enhanced oxidation resistance was attributed to the presence of a chromium-enriched layer which was detected by use of an X-ray microanalyzer. The oxidation kinetics equation obtained for the first 8 min is applicable to the model calculation of a hypothetical LOCA in a LWR, employing 304 stainless steel cladding.

High temperature corrosion in straw-fired power plants: Influence of steam/metal temperature on corrosion rates for TP347H

DEFF Research Database (Denmark)

Montgomery, Melanie; Biede, O; Larsen, OH

2002-01-01

The corrosion in straw-fired boilers has been investigated at various straw-fired power plants in Denmark. Water/air-cooled probes, a test superheater and test sections removed from the actual superheater have been utilised to characterise corrosion and corrosion rates. This paper describes...... the corrosion rates measured for the TP347H type steel. The corrosion morphology at high temperature consists of grain boundary attack and selective attack of chromium. The corrosion rate increases with calculated metal temperature (based on steam temperature), however there is great variation within....... The difference in the results could be traced back to a lower flue gas temperature on one side of the boiler. Although metal temperature is the most important parameter with respect to corrosion rate, flue gas temperature also plays an important role. Efforts to quantify the effect of flue gas temperature...

Multi-layer casing of a steam turbine for high steam pressures and temperatures

International Nuclear Information System (INIS)

Remberg, A.

1978-01-01

In previous turbine casings there is no sealing provided between the inner layer and the outer layer, so that the steam pressure acts fully on the casing top and on the shaft seal housing situated there. To reduce the displacement which occurs there due to pressure differences in the various steam spaces, the normal inner casing is made with the shaft sealing housing in an inner layer, which cannot be divided in the axial direction. The inner layer can be inserted from the high pressure side into the unit outer casing. A horizontal section through the turbine in the attached drawing makes the construction and operation of the invention clear. (GL) [de

A three-dimensional laboratory steam injection model allowing in situ saturation measurements

Energy Technology Data Exchange (ETDEWEB)

Demiral, B.M.R.; Pettit, P.A.; Castanier, L.M.; Brigham, W.E.

1992-08-01

The CT imaging technique together with temperature and pressure measurements were used to follow the steam propagation during steam and steam foam injection experiments in a three dimensional laboratory steam injection model. The advantages and disadvantages of different geometries were examined to find out which could best represent radial and gravity override flows and also fit the dimensions of the scanning field of the CT scanner. During experiments, steam was injected continuously at a constant rate into the water saturated model and CT scans were taken at six different cross sections of the model. Pressure and temperature data were collected with time at three different levels in the model. During steam injection experiments, the saturations obtained by CT matched well with the temperature data. That is, the steam override as observed by temperature data was also clearly seen on the CT pictures. During the runs where foam was present, the saturation distributions obtained from CT pictures showed a piston like displacement. However, the temperature distributions were different depending on the type of steam foam process used. The results clearly show that the pressure/temperature data alone are not sufficient to study steam foam in the presence of non-condensible gas.

A Numerical Study on Mass Transfer and Methanol Conversion Efficiency According to Porosity and Temperature Change of Curved Channel Methanol-Steam Reformer

Energy Technology Data Exchange (ETDEWEB)

Seong, Hong Seok; Lee, Chung Ho; Suh, Jeong Se [Gyeongsang Nat’l Univ., Jinju (Korea, Republic of)

2016-11-15

Micro methanol-steam reformer for fuel cell can effectively produce hydrogen as reforming response to steam takes place in low temperature (less than 250℃). This study conducted numerical research on this reformer. First, study set wall temperature of the reformer at 100, 140, 180 and 220℃ while methanol conversion efficiency was set in 0, 0.072, 3.83 and 46.51% respectively. Then, porosity of catalyst was set in 0.1, 0.35, 0.6 and 0.85 and although there was no significant difference in methanol conversion efficiency, values of pressure drop were 4645.97, 59.50, 5.12 and 0.45 kPa respectively. This study verified that methanol-steam reformer rarely responds under the temperature of 180℃ and porosity does not have much effect on methanol conversion efficiency if the fluid flowing through reformer lowers activation energy by sufficiently contacting reformer.

A Numerical Study on Mass Transfer and Methanol Conversion Efficiency According to Porosity and Temperature Change of Curved Channel Methanol-Steam Reformer

International Nuclear Information System (INIS)

Seong, Hong Seok; Lee, Chung Ho; Suh, Jeong Se

2016-01-01

Micro methanol-steam reformer for fuel cell can effectively produce hydrogen as reforming response to steam takes place in low temperature (less than 250℃). This study conducted numerical research on this reformer. First, study set wall temperature of the reformer at 100, 140, 180 and 220℃ while methanol conversion efficiency was set in 0, 0.072, 3.83 and 46.51% respectively. Then, porosity of catalyst was set in 0.1, 0.35, 0.6 and 0.85 and although there was no significant difference in methanol conversion efficiency, values of pressure drop were 4645.97, 59.50, 5.12 and 0.45 kPa respectively. This study verified that methanol-steam reformer rarely responds under the temperature of 180℃ and porosity does not have much effect on methanol conversion efficiency if the fluid flowing through reformer lowers activation energy by sufficiently contacting reformer.

Vapor generator steam drum spray heat

International Nuclear Information System (INIS)

Fasnacht, F.A. Jr.

1978-01-01

A typical embodiment of the invention provides a combination feedwater and cooldown water spray head that is centrally disposed in the lower portion of a nuclear power plant steam drum. This structure not only discharges the feedwater in the hottest part of the steam drum, but also increases the time required for the feedwater to reach the steam drum shell, thereby further increasing the feedwater temperature before it contacts the shell surface, thus reducing thermal shock to the steam drum structure

Supersymmetric D-term inflation, reheating, and Affleck-Dine baryogenesis

International Nuclear Information System (INIS)

Kolda, C.; March-Russell, J.

1999-01-01

The phenomenology of supersymmetric models of inflation, where the inflationary vacuum energy is dominated by D terms of a U(1), is investigated. Particular attention is paid to the questions of how to arrange for sufficient e folds of inflation to occur, what kind of thermal history is expected after the end of inflation, and how to implement successful baryogenesis. Such models are argued to require a more restrictive symmetry structure than previously thought. In particular, it is nontrivial that the decays of the fields driving D inflation can reheat the Universe in such a way as to avoid the strong gravitino production constraints. We also show how the initial conditions for Affleck-Dine baryogenesis can arise in these models and that the simplest flat directions along which a baryon number is generated can often be ruled out by the constraints coming from a decoherence of the condensate in a hot environment. At the end, we find that successful reheating and baryogenesis can take place in a large subset of D-inflationary models. copyright 1999 The American Physical Society

High Temperature Steam Oxidation Testing of Candidate Accident Tolerant Fuel Cladding Materials

Energy Technology Data Exchange (ETDEWEB)

Pint, Bruce A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nelson, Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Parker, Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Parkison, Adam [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2013-12-23

The Fuel Cycle Research and Development (FCRD) program’s Advanced Fuels Campaign has initiated a multifold effort aimed at facilitating development of accident tolerant fuels in order to overcome the inherent shortcomings of light water reactor (LWR) fuels when exposed to beyond design basis accident conditions. The campaign has invested in development of experimental infrastructure within the Department of Energy complex capable of chronicling the performance of a wide range of concepts under prototypic accident conditions. This report summarizes progress made at Oak Ridge National Laboratory (ORNL) and Los Alamos National Laboratory (LANL) in FY13 toward these goals. Alternative fuel cladding materials to Zircaloy for accident tolerance and a significantly extended safety margin requires oxidation resistance to steam or steam-H₂ environments at ≥1200°C for short times. At ORNL, prior work focused attention on SiC, FeCr and FeCrAl as the most promising candidates for further development. Also, it was observed that elevated pressure and H2 additions had minor effects on alloy steam oxidation resistance, thus, 1 bar steam was adequate for screening potential candidates. Commercial Fe-20Cr-5Al alloys remain protective up to 1475°C in steam and CVD SiC up to 1700°C in steam. Alloy development has focused on Fe-Cr-Mn-Si-Y and Fe-Cr-Al-Y alloys with the aluminaforming alloys showing more promise. At 1200°C, ferritic binary Fe-Cr alloys required ≥25% Cr to be protective for this application. With minor alloy additions to Fe-Cr, more than 20%Cr was still required, which makes the alloy susceptible to α’ embrittlement. Based on current results, a Fe-15Cr-5Al-Y composition was selected for initial tube fabrication and welding for irradiation experiments in FY14. Evaluations of chemical vapor deposited (CVD) SiC were conducted up to 1700°C in steam. The reaction of H₂O with the alumina reaction tube at 1700°C resulted in Al(OH)₃

Materials Performance in USC Steam

Energy Technology Data Exchange (ETDEWEB)

G. R. Holcomb, P. Wang, P. D. Jablonski, and J. A. Hawk

2010-05-01

The proposed steam inlet temperature in the Advanced Ultra Supercritical (A-USC) steam turbine is high enough (760 °C) that traditional turbine casing and valve body materials such as ferritic/martensitic steels will not suffice due to temperature limitations of this class of materials. Cast versions of several traditionally wrought Ni-based superalloys were evaluated for use as casing or valve components for the next generation of industrial steam turbines. The full size castings are substantial: 2-5,000 kg each half and on the order of 100 cm thick. Experimental castings were quite a bit smaller, but section size was retained and cooling rate controlled to produce equivalent microstructures. A multi-step homogenization heat treatment was developed to better deploy the alloy constituents. The most successful of these cast alloys in terms of creep strength (Haynes 263, Haynes 282, and Nimonic 105) were subsequently evaluated by characterizing their microstructure as well as their steam oxidation resistance (at 760 and 800 °C).

Optimization of High Temperature and Pressurized Steam Modified Wood Fibers for High-Density Polyethylene Matrix Composites Using the Orthogonal Design Method

Directory of Open Access Journals (Sweden)

Xun Gao

2016-10-01

Full Text Available The orthogonal design method was used to determine the optimum conditions for modifying poplar fibers through a high temperature and pressurized steam treatment for the subsequent preparation of wood fiber/high-density polyethylene (HDPE composites. The extreme difference, variance, and significance analyses were performed to reveal the effect of the modification parameters on the mechanical properties of the prepared composites, and they yielded consistent results. The main findings indicated that the modification temperature most strongly affected the mechanical properties of the prepared composites, followed by the steam pressure. A temperature of 170 °C, a steam pressure of 0.8 MPa, and a processing time of 20 min were determined as the optimum parameters for fiber modification. Compared to the composites prepared from untreated fibers, the tensile, flexural, and impact strength of the composites prepared from modified fibers increased by 20.17%, 18.5%, and 19.3%, respectively. The effect on the properties of the composites was also investigated by scanning electron microscopy and dynamic mechanical analysis. When the temperature, steam pressure, and processing time reached the highest values, the composites exhibited the best mechanical properties, which were also well in agreement with the results of the extreme difference, variance, and significance analyses. Moreover, the crystallinity and thermal stability of the fibers and the storage modulus of the prepared composites improved; however, the hollocellulose content and the pH of the wood fibers decreased.

Estimation of steam-chamber extent using 4D seismic

Energy Technology Data Exchange (ETDEWEB)

Tanaka, M. [Waseda Univ., Waseda (Japan); Endo, K. [Japan Canada Oil Sands Ltd., Calgary, AB (Canada); Onozuka, S. [Japan Oil, Gas and Metals National Corp., Tokyo (Japan)

2009-07-01

The steam-assisted gravity drainage (SAGD) technique is among the most effective steam injection methods and is widely applied in Canadian oil-sand reservoirs. The SAGD technology uses hot steam to decrease bitumen viscosity and allow it to flow. Japan Canada Oil Sands Limited (JACOS) has been developing an oil-sand reservoir in the Alberta's Hangingstone area since 1997. This paper focused on the western area of the reservoir and reported on a study that estimated the steam-chamber extent generated by horizontal well pairs. It listed steam injection start time for each well of the western area. Steam-chamber distribution was determined by distinguishing high temperature and high pore-pressure zones from low temperature and high pore-pressure zones. The bitumen recovery volume in the steam-chamber zone was estimated and compared with the actual cumulative production. This paper provided details of the methodology and interpretation procedures for the quantitative method to interpret 4D-seismic data for a SAGD process. A procedure to apply a petrophysical model was demonstrated first by scaling laboratory measurements to field-scale applications, and then by decoupling pressure and temperature effects. The first 3D seismic data in this study were already affected by higher pressures and temperatures. 11 refs., 3 tabs., 12 figs.

Corrosion fatigue in LP steam turbine blading - experiences, causes and appropriate measures; Korrosionsutmattning i aangturbinskovlar - Erfarenheter, inverkande faktorer och moejliga aatgaerder

Energy Technology Data Exchange (ETDEWEB)

Tavast, J [ABB STAL AB, Finspaang (Sweden)

1996-12-01

Corrosion fatigue in LP steam turbine blading was reviewed together with result of tests performed in order to find blade materials with improved resistance against this. According to international experience, corrosion fatigue of 12Cr steam turbine blades in the transition zone between dry and wet steam, is one of the major causes, if not the major cause, for unavailability of steam turbines. Corrosion fatigue in LP blading is a frequent problem also in Swedish and Finnish nuclear power plants, especially in turbines of type D54 in BWR-plants. Corrosion fatigue has also been discovered in at least one type of nuclear turbine. Initiation times have been very long and the varying experiences in different types of turbines may simply reflect differing initiation times. Corrosion fatigue may therefore become more frequent in other types of turbines in the future. The type of water treatment (BWR/PWR) and possibly temperature after reheating seem to influence the risk for corrosion fatigue. Influence of inleakage of cooling water is less clear for these nuclear plants. The long initiation times together with the fact that very few of the cracked blades have actually failed, indicate that the cracks initiate and/or propagate during transients. Extensive laboratory tests show that there are alternative blade materials available with improved resistance against corrosion fatigue, with the most promising being 15/5 PH and A905, together with Ti6Al4V. The Ti alloy shows the best resistance against corrosion fatigue in most environments and is already used in some turbines. Disadvantage is a higher cost and possible need for redesign of the blades. The alternative materials are recommended for use for blades in the transition zone between dry and wet steam in LP turbines. The main disadvantage is a lack of references, even if 15%5 PH has been used to a very limited extent. 40 refs, 24 figs, 12 tabs, 9 appendices

High-temperature deformation and rupture behavior of internally-pressurized Zircaloy-4 cladding in vacuum and steam enivronments

International Nuclear Information System (INIS)

Chung, H.M.; Garde, A.M.; Kassner, T.F.

1977-01-01

The high-temperature diametral expansion and rupture behavior of Zircaloy-4 fuel-cladding tubes have been investigated in vacuum and steam environments under transient-heating conditions that are of interest in hypothetical loss-of-coolant accident situations in light-water reactors. The effects of internal pressure, heating rate, axial constraint, and localized temperature nonuniformities in the cladding on the maximum circumferential strain have been determined for burst temperatures between approximately 650 and 1350 0 C

Treating bituminous minerals. [use of superheated steam

Energy Technology Data Exchange (ETDEWEB)

MacIvor, G

1880-12-21

In this new procedure, the superheated steam is the agent by which the heat is directly applied to the rock; the superheated steam is made to pass between the rocks and into the vessel or retort in which the rock is contained and where the extraction of the bitumen or the distillation of the mineral oils is carried out. The temperature of the heating apparatus in which the steam is superheated, is easily regulated at will in accord with the desired result. When one wishes to extract only bitumen, the temperature of the steam is raised to a point sufficiently high to loosen and separate the bitumen without permitting any condensation of water inside the retort. When it is desired to produce a mineral oil, the temperature is increased in such a way that all the volatile products are distilled from the rock and come into the condenser. By means of this process, any temperature up to a full red heat, can be maintained in the retort, making possible many variations in the kind of products obtainable from the rock.

Influence of Superheated Steam Temperature Regulation Quality on Service Life of Boiler Steam Super-Heater Metal

Directory of Open Access Journals (Sweden)

G. T. Kulakov

2009-01-01

Full Text Available The paper investigates influence of change in quality of superheated steam temperature regulations on service life of super-heater metal. А dependence between metal service life and dispersion value for different steel grades has been determined in the paper. Numerical values pertaining to increase of super-heater metal service life in case of transferring from manual regulation to standard system of automatic regulation (SAR have been determined and in case of transferring from standard SAR to improved SAR. The analysis of tabular data and plotted dependencies makes it possible to conclude that any change in conditions of convection super-heater metal work due to better quality of the regulation leads to essential increase of time period which is left till the completion of the service life of a super-heater heating surface.

Design of H2/H∞ RMPC for Boiler Superheated Steam Temperature Based on Memoryless Feedback Multistep Strategy

Directory of Open Access Journals (Sweden)

Pu Han

2017-01-01

Full Text Available The collection of superheated steam temperature models of a thermal power plant under different loads can be approximated to “multimodel” linear uncertain systems. After transformation, the tracking system was obtained from “multimodel” linear uncertain systems. For this tracking uncertain system, a mixed H2/H∞ robust model predictive control (HRMPC based on a memoryless feedback multistep strategy is proposed. A multistep control strategy combines the advantages of predictive control rolling optimization with memoryless feedback control thoughts. It could effectively decrease the controller optimization parameter and ensure closed-loop system stability, and, at the same time, it also achieved acceptable control performance. Successful application to the superheated steam temperature system of a 300 MW thermal power plant verified the study of the HRMPC-P cascade controller design scheme in terms of feasibility and effectiveness.

Ultra high-temperature solids-free insulating packer fluid for oil and gas production, steam injection and geothermal wells

Energy Technology Data Exchange (ETDEWEB)

Ezell, R.G.; Harrison, D.J. [Society of Petroleum Engineers, Canadian Section, Calgary, AB (Canada)]|[Halliburton Energy Services, Calgary, AB (Canada)

2008-10-15

Uncontrolled heat transfer from production/injection tubing during thermal oil recovery via steam injection can be detrimental to the integrity of the casing and to the quality of the steam that is injected into the reservoir. An aqueous-based insulating packer fluid (IPF) was introduced to improve the steam injection process by controlling the total heat loss from the produced fluids to the surrounding wellbore, internal annuli and formation. The IPF was developed for elevated temperature environments through extensive investigation across multidisciplinary technology. The innovative system delivers performance beyond conventional systems of comparable thermal conductivity. Its density range and conductivity measurements were presented in this paper. High-temperature static aging tests showed superior gel integrity without any phase separation after exposure to temperatures higher than 260 degrees C. The new fluids are hydrate inhibitive, non-corrosive and pass oil and grease testing. They are considered to be environmentally sound by Gulf of Mexico standards. It was concluded that the new ultra high-performance insulating packer fluid (HTIPF) reduced the heat loss significantly by both conduction and convection. Heat transfer within the aqueous-based HTIPF was 97 per cent less than that of pure water. It was concluded that the HTIPF can be substituted for conventional packer fluids without compromising any well control issues. 21 refs., 1 tab., 4 figs.

Zircaloy-steam reaction under a simulated loss-of-coolant accident

International Nuclear Information System (INIS)

Kawasaki, Satoru; Furuta, Teruo; Hashimoto, Masao

1975-07-01

Under a simulated loss-of-coolant condition, the reaction between zircaloy and steam and the embrittlement of the zircaloy oxidized by this reaction have been studied. The parabolic rate constant, ksub(p), in the zircaloy-steam reaction is represented as ksub(p)=3.24x10 6 exp(-40500/RT) (mg 2 /cm 4 . sec) Ring compression test was made on the steam-reacted zircaloy tubes, and following results were obtained: Embrittlement of the steam-reacted zircaloy tube increases with oxidation at each oxidation temperature. For a given quantity of the oxidation, the incursion of α-phase into β-phase is more remarkable in the specimens reacted at low temperatures than those at high temperatures. The embrittlement, however, is larger in the specimens oxidized at high temperatures than those at low temperatures. (auth.)

Multifactorial modelling of high-temperature treatment of timber in the saturated water steam medium

Science.gov (United States)

Prosvirnikov, D. B.; Safin, R. G.; Ziatdinova, D. F.; Timerbaev, N. F.; Lashkov, V. A.

2016-04-01

The paper analyses experimental data obtained in studies of high-temperature treatment of softwood and hardwood in an environment of saturated water steam. Data were processed in the Curve Expert software for the purpose of statistical modelling of processes and phenomena occurring during this process. The multifactorial modelling resulted in the empirical dependences, allowing determining the main parameters of this type of hydrothermal treatment with high accuracy.

Corrosion of Inconel-625, Hastelloy-X280 and Incoloy-800 in 550 - 750°C superheated steam. Influence of alloy heat treatment, surface treatment, steam temperature and steam velocity. Part I: Results up to 6000 hours exposure time. RCN Report

International Nuclear Information System (INIS)

Tilborg, P.J. van; Linde, A. van der

1969-10-01

Sheet samples of Inconel-625, Hastelloy-X280 and Incoloy-800 were tested, in the solution annealed and in the solution annealed + 20% cold worked + 800°C tempered condition, in steam with a velocity of 5 m/sec. at 550, 650 and 750°C and in steam with a volocity of 15 and 85 m/sec. at 550°C. At 550°C and 750°C the samples were tested in the heat treated, annealed or tempered and the heat treated + electropolished condition. At 650°C moreover as heat treated + ground and pickled samples were tested. Post-corrosion sample investigations involved measurement of the adherent oxide thickness, the total amount of corroded metal, the metal loss to system, and the metallographic and microprobe investigation of the adherent oxide film and adjacent diffusion disturbed alloy layer. The results obtained up to 6000 hours exposure time showed that the surface treatment has a decisive influence on the corrosion behaviour of all three alloys tested. The differences in the corrosion data for the two heat treatment conditions are small. The influence of the steam velocity, as tested at 550°C, on the initial corrosion rate was surprisingly high, while the long-term linear corrosion rates are only slightly influenced by the gas velocity. In general the linear corrosion rates were low, 1-5 mg/dm 2 month, and not consistently affected by the test-temperature. The metal loss to system values were 2 <15 mg/dm 2 in the low velocity steam at all three test temperatures and <30 mg/dm 2 in the high velocity steam at 550°C. The metallographic and microprobe examinations revealed no remarkable results, as compared with the results of analogous tests reported in literature. (author)

Oxidation behaviour of titanium in high temperature steam

International Nuclear Information System (INIS)

Moroishi, Taishi; Shida, Yoshiaki

1978-01-01

The oxidation of pure titanium was studied in superheated steam at 400 -- 550 0 C. The effects of prior cold working and several heat treatment conditions on the oxidation were examined and also the effects of the addition of small amounts of iron and oxygen were investigated. The oxidation mechanism of pure titanium is discussed in relation to the scale structure and the oxidation kinetics. Hydrogen absorption rate was also measured. As a result, the following conclusions were drawn: (1) The oxidation of pure titanium in steam was faster than in air and breakaway oxidation was observed above 500 0 C after the specimen had gained a certain weight. Prior cold working and heat treatment conditions scarcely affected the oxidation rate, whereas the specimen containing small amounts of iron and oxygen showed a little more rapid oxidation. (2) At 500 and 550 0 C a dark grey inner scale and a yellow-brown outer scale were formed. The outer scale was apt to exfoliate after the occurrence of breakaway oxidation. At 400 and 450 0 C only a dark grey scale was observed. All of these oxides were identified as the rutile type, TiO 2 . Furthermore, the presence of a thin and uniform oxygen rich layer beneath the external scale was confirmed at all test temperatures. (3) The measured weight gain approximately followed the cubic rate law; this would be expected for the following reason; one component of the weight gain is due to the dissolved oxygen, the amount of which remains constant after the early stages of oxidation. The second component is due to the parabolic growth of the external TiO 2 scale. When these contributions are added a pseudo-cubic weight gain curve results. (4) It was shown that 50 percent of the hydrogen generated during the oxidation was absorbed into the metal. (auth.)

Study on thermodynamic cycle of high temperature gas-cooled reactor

International Nuclear Information System (INIS)

Qu Xinhe; Yang Xiaoyong; Wang Jie

2017-01-01

The development trend of the (very) High temperature gas-cooled reactor is to gradually increase the reactor outlet temperature. The different power conversion units are required at the different reactor outlet temperature. In this paper, for the helium turbine direct cycle and the combined cycle of the power conversion unit of the High temperature gas-cooled reactor, the mathematic models are established, and three cycle plans are designed. The helium turbine direct cycle is a Brayton cycle with recuperator, precooler and intercooler. In the combined cycle plan 1, the topping cycle is a simple Brayton cycle without recuperator, precooler and intercooler, and the bottoming cycle is based on the steam parameters (540deg, 6 MPa) recommended by Siemens. In the combined cycle plan 2, the topping cycle also is a simple Brayton cycle, and the bottoming cycle which is a Rankine cycle with reheating cycle is based on the steam parameters of conventional subcritical thermal power generation (540degC, 18 MPa). The optimization results showed that the cycle efficiency of the combined cycle plan 2 is the highest, the second is the helium turbine direct cycle, and the combined cycle plan 2 is the lowest. When the reactor outlet temperature is 900degC and the pressure ratio is 2.02, the cycle efficiency of the combined cycle plan 2 can reach 49.7%. The helium turbine direct cycle has a reactor inlet temperature above 500degC due to the regenerating cycle, so it requires a cooling circuit for the internal wall of the reactor pressure vessel. When the reactor outlet temperature increases, the increase of the pressure ratio required by the helium turbine direct cycle increases may bring some difficulties to the design and manufacture of the magnetic bearings. For the combined cycle, the reactor inlet temperature can be controlled below than 370degC, so the reactor pressure vessel can use SA533 steel without cooling the internal wall of the reactor pressure vessel. The pressure

Steam-chemical reactivity for irradiated beryllium

Energy Technology Data Exchange (ETDEWEB)

Anderl, R.A.; McCarthy, K.A.; Oates, M.A.; Petti, D.A.; Pawelko, R.J.; Smolik, G.R. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States)

1998-01-01

This paper reports the results of an experimental investigation to determine the influence of neutron irradiation effects and annealing on the chemical reactivity of beryllium exposed to steam. The work entailed measurements of the H{sub 2} generation rates for unirradiated and irradiated Be and for irradiated Be that had been previously annealed at different temperatures ranging from 450degC to 1200degC. H{sub 2} generation rates were similar for irradiated and unirradiated Be in steam-chemical reactivity experiments at temperatures between 450degC and 600degC. For irradiated Be exposed to steam at 700degC, the chemical reactivity accelerated rapidly and the specimen experienced a temperature excursion. Enhanced chemical reactivity at temperatures between 400degC and 600degC was observed for irradiated Be annealed at temperatures of 700degC and higher. This reactivity enhancement could be accounted for by the increased specific surface area resulting from development of a surface-connected porosity in the irradiated-annealed Be. (author)

Model studies of the vertical steam generator thermal-hydraulic characteristics

International Nuclear Information System (INIS)

Desyatun, V.F.; Moskvichev, V.F.; Ulasov, V.M.; Morozov, V.G.; Burkov, V.K.; Grebennikov, V.N.

1984-01-01

Results of investigations conducted to clarify the calculation technique and to test the workability of the main elements and units of the PGV-250 vertical steam generator of saturated steam are considered. The steam generating capacity of the plant is 1486 t/h, thermal power is 792 MW. Steam generation follows a multiple circulation scheme. The heat surface comprises 330-shields. The investigations are carried out with a model which reproduces all the main elements of the steam generator xcluding the economizer section. The flow rates of feed water, generated steam and coolant of the first circuit as well as temperature, pressure and humidity of the generated steam past the separator are determined. The average heat transfer factors of the heat surface are calculated on the base of the data obtained and a conclusion is drawn on the correctness of the thermohydraulic calculation technique used in development of the PGV-250 steam generator design. Temperature pulsations and heat surface steaming are not observed. The steam humidity at the outlet and steam capture into sinking tubes are within permissible values

MSW-resonant fermion mixing during reheating

Science.gov (United States)

Kanai, Tsuneto; Tsujikawa, Shinji

2003-10-01

We study the dynamics of reheating in which an inflaton field couples two flavor fermions through Yukawa-couplings. When two fermions have a mixing term with a constant coupling, we show that the Mikheyev-Smirnov-Wolfenstein (MSW)-type resonance emerges due to a time-dependent background in addition to the standard fermion creation via parametric resonance. This MSW resonance not only alters the number densities of fermions generated by a preheating process but also can lead to the larger energy transfer from the inflaton to fermions. Our mechanism can provide additional source terms for the creation of superheavy fermions which may be relevant for the leptogenesis scenario.

MSW-resonant fermion mixing during reheating

International Nuclear Information System (INIS)

Kanai, Tsuneto; Tsujikawa, Shinji

2003-01-01

We study the dynamics of reheating in which an inflaton field couples two flavor fermions through Yukawa-couplings. When two fermions have a mixing term with a constant coupling, we show that the Mikheyev-Smirnov-Wolfenstein (MSW)-type resonance emerges due to a time-dependent background in addition to the standard fermion creation via parametric resonance. This MSW resonance not only alters the number densities of fermions generated by a preheating process but also can lead to the larger energy transfer from the inflaton to fermions. Our mechanism can provide additional source terms for the creation of superheavy fermions which may be relevant for the leptogenesis scenario

Steam cleaning device

International Nuclear Information System (INIS)

Karaki, Mikio; Muraoka, Shoichi.

1985-01-01

Purpose: To clean complicated and long objects to be cleaned having a structure like that of nuclear reactor fuel assembly. Constitution: Steams are blown from the bottom of a fuel assembly and soon condensated initially at the bottom of a vertical water tank due to water filled therein. Then, since water in the tank is warmed nearly to the saturation temperature, purified water is supplied from a injection device below to the injection device above the water tank on every device. In this way, since purified water is sprayed successively from below to above and steams are condensated in each of the places, the entire fuel assembly elongated in the vertical direction can be cleaned completely. Water in the reservoir goes upward like the steam flow and is drained together with the eliminated contaminations through an overflow pipe. After the cleaning has been completed, a main steam valve is closed and the drain valve is opened to drain water. (Kawakami, Y.)

Digital simulation for nuclear once-through steam generators

International Nuclear Information System (INIS)

Chen, A.T.

1976-01-01

Mathematical models for calculating the dynamic response of the Oconee type once through steam generator (OTSG) and the integral economizer once through steam generator (IEOTSG) was developed and presented in this dissertation. Linear and nonlinear models of both steam generator types were formulated using the state variable, lumped parameter approach. Transient and frequency responses of system parameters were calculated for various perturbations from both the primary coolant side and the secondary side. Transients of key parameters, including primary outlet temperature, superheated steam outlet temperature, boiling length/subcooled length and steam pressure, were generated, compared and discussed for both steam generator types. Frequency responses of delta P/sub s//deltaT/sub pin/ of the linear OTSG model were validated by using the dynamic testing results obtained at the Oconee I nuclear power station. A sensitivity analysis in both the time and the frequency domains was performed. It was concluded that the mathematical and computer models developed in this dissertation for both the OTSG and the IEOTSG are suitable for overall plant performance evaluation and steam generator related component/system design analysis for nuclear plants using either type of steam generator

Steam oxidation of Zr 1% Nb clads of VVER fuels in high temperature

International Nuclear Information System (INIS)

Solyanyj, V.I.; Bibilashvili, Yu.K.; Dranenko, V.V.; Levin, A.Ya.; Izrajlevskij, L.B.; Morozov, A.M.

1984-01-01

In a wide range of accident conditions processes of clad corrosion effected by steam are rather intensive and in many respects influence the safety of NPP and the after-accident dismantling of a reactor core. This paper discusses the results of comprehensive studies into corrosion behaviour of Zr 1%Nb clads of VVER-type fuels at high temperatures. These studies are a continuation of previous work and the base for the design modelling of corrosion processes

Fast power cycle for fusion reactors

International Nuclear Information System (INIS)

Powell, J.; Fillo, J.; Makowitz, H.

1978-01-01

The unique, deep penetration capability of 14 MeV neutrons produced in DT fusion reactions allows the generation of very high temperature working fluid temperatures in a thermal power cycle. In the FAST (Fusion Augmented Steam Turbine) power cycle steam is directly superheated by the high temperature ceramic refractory interior of the blanket, after being generated by heat extracted from the relatively cool blanket structure. The steam is then passed to a high temperature gas turbine for power generation. Cycle studies have been carried out for a range of turbine inlet temperatures [1600 0 F to 3000 0 F (870 to 1650 0 C)], number of reheats, turbine mechanical efficiency, recuperator effectiveness, and system pressure losses. Gross cycle efficiency is projected to be in the range of 55 to 60%, (fusion energy to electric power), depending on parameters selected. Turbine inlet temperatures above 2000 0 F, while they do increase efficiency somewhat, are not necessarily for high cycle efficiency

Numerical simulation in steam injection process by a mechanistic approach

Energy Technology Data Exchange (ETDEWEB)

De Souza, J.C.Jr.; Campos, W.; Lopes, D.; Moura, L.S.S. [Petrobras, Rio de Janeiro (Brazil)

2008-10-15

Steam injection is a common thermal recovery method used in very viscous oil reservoirs. The method involves the injection of heat to reduce viscosity and mobilize oil. A steam generation and injection system consists primarily of a steam source, distribution lines, injection wells and a discarding tank. In order to optimize injection and improve the oil recovery factor, one must determine the parameters of steam flow such as pressure, temperature and steam quality. This study focused on developing a unified mathematical model by means of a mechanistic approach for two-phase steam flow in pipelines and wells. The hydrodynamic and heat transfer mechanistic model was implemented in a computer simulator to model the parameters of steam injection while trying to avoid the use of empirical correlations. A marching algorithm was used to determine the distribution of pressure and temperature along the pipelines and wellbores. The mathematical model for steam flow in injection systems, developed by a mechanistic approach (VapMec) performed well when the simulated values of pressures and temperatures were compared with the values measured during field tests. The newly developed VapMec model was incorporated in the LinVap-3 simulator that constitutes an engineering supporting tool for steam injection wells operated by Petrobras. 23 refs., 7 tabs., 6 figs.

Control system for fluid heated steam generator

Science.gov (United States)

Boland, J.F.; Koenig, J.F.

1984-05-29

A control system for controlling the location of the nucleate-boiling region in a fluid heated steam generator comprises means for measuring the temperature gradient (change in temperature per unit length) of the heating fluid along the steam generator; means for determining a control variable in accordance with a predetermined function of temperature gradients and for generating a control signal in response thereto; and means for adjusting the feedwater flow rate in accordance with the control signal.

Optimum gas turbine cycle for combined cycle power plant

International Nuclear Information System (INIS)

Polyzakis, A.L.; Koroneos, C.; Xydis, G.

2008-01-01

The gas turbine based power plant is characterized by its relatively low capital cost compared with the steam power plant. It has environmental advantages and short construction lead time. However, conventional industrial engines have lower efficiencies, especially at part load. One of the technologies adopted nowadays for efficiency improvement is the 'combined cycle'. The combined cycle technology is now well established and offers superior efficiency to any of the competing gas turbine based systems that are likely to be available in the medium term for large scale power generation applications. This paper has as objective the optimization of a combined cycle power plant describing and comparing four different gas turbine cycles: simple cycle, intercooled cycle, reheated cycle and intercooled and reheated cycle. The proposed combined cycle plant would produce 300 MW of power (200 MW from the gas turbine and 100 MW from the steam turbine). The results showed that the reheated gas turbine is the most desirable overall, mainly because of its high turbine exhaust gas temperature and resulting high thermal efficiency of the bottoming steam cycle. The optimal gas turbine (GT) cycle will lead to a more efficient combined cycle power plant (CCPP), and this will result in great savings. The initial approach adopted is to investigate independently the four theoretically possible configurations of the gas plant. On the basis of combining these with a single pressure Rankine cycle, the optimum gas scheme is found. Once the gas turbine is selected, the next step is to investigate the impact of the steam cycle design and parameters on the overall performance of the plant, in order to choose the combined cycle offering the best fit with the objectives of the work as depicted above. Each alterative cycle was studied, aiming to find the best option from the standpoint of overall efficiency, installation and operational costs, maintainability and reliability for a combined power

7 CFR 305.23 - Steam sterilization treatment schedules.

Science.gov (United States)

2010-01-01

... 7 Agriculture 5 2010-01-01 2010-01-01 false Steam sterilization treatment schedules. 305.23... Steam sterilization treatment schedules. Treatment schedule Temperature( °F) Pressure Exposure period (minutes) Directions T303-b-1 10 lbs 20 Use 28″ vacuum. Steam sterilization is not practical for treatment...

Monitoring method for steam generator operation

International Nuclear Information System (INIS)

Tamaoki, Tetsuo

1991-01-01

In an LMFBR plant having an once-through steam generator, reduction of life of a heat transfer pipe caused by heat cycle fatigue is monitored by early finding for the occurrence of abnormality in the inside of the steam generator and by continuous monitoring for the position of departure from nucleate boiling (DNB), which are difficult with existent static characteristic analysis codes. That is, RMS values of fluctuations in temperature signals sent from thermocouples for measuring the fluid temperature in the vicinity of heat transfer pipe disposed along a primary channel of the once-through type steam generator. The abnormality in heat transfer performance is monitored by the distribution change of the RMS values. Subsequently, DNB point on the side of water and steam is determined by the distribution of the RMS value. Then, accumulated values of the product between the time in which the starting point stays in the DNB region and a life consumption amount per unit time given in accordance with the operation condition are monitored. Accordingly, thermal fatigue failure of the heat transfer pipe due to temperature fluctuation in the DNB region is monitored. (I.S.)

High-temperature reactors. Activities in France on the steam cycle HTR

International Nuclear Information System (INIS)

Lacoste Lareymondie, de; Guennec, N.; Rastoin, J.

1975-01-01

Although French activities cover all the possibilities of high-temperature reactors the effort of the last few years has been concentrated on the steam cycle electricity-generating version. This work, closely coordinated with that of General Atomic in application of agreements settled in 1972 and 1973, was devoted to engineering as a result of the assimilation of American technique by French industry and to research and development owing to the joint CEA and GA programme. After an examination of these two centers of activity the reasons which will lead to a closer collaboratin among the European partners of General Atomic are expressed in conclusion [fr

Formula for radial profiles of temperature in steam-liquid sodium reactive jets

International Nuclear Information System (INIS)

Hobbes, P.; Mora-Perez, J.L.; Carreau, J.L.; Gbahoue, L.; Roger, F.

1987-01-01

One of the important problems of the study of distribution of temperatures in the reactive steam-liquid sodium jet rests in the mathematical formulation of their radial effects. During the experiment, two forms have been brought to light: from a certain distance of the injector, the radial distribution of temperature can be represented, in a classical way, by an error function curve; close to the injector, the radial profile allows for a minimum located on the axis of the jet. An energy balance permits, by dividing the jet in three parts: a central nucleus composed of practically pure gas, a gas ring plus drops and a liquid peripheral area plus bubbles, to obtain a mathematical formulation of the profiles, close to the injection which accounts quite well for the experimental points and their form

Method for extending the unrestricted operating range of condensing steam turbines

International Nuclear Information System (INIS)

Csaba, G.; Bannerth, Cs.

2009-01-01

The allowed condenser temperature of the condensing steam turbines is determined by the design parameters of the steam turbine (casing geometry, exhaust area, blade length, blade angle, blade profile etc.). The fluctuations of condenser temperature may lead to reduced power output of the condensing steam turbine. Solutions where the low pressure turbine casings have the same exhaust area can be kept in operation at narrow condenser temperature range without restrictions. Exceeding the mentioned temperature range the exhaust hood temperature restriction, undergoing the temperature range choking point restriction appears causing increased operation cost. The aim of the paper is to present a condensing steam turbine - direct-contact condenser system that can extend the unrestricted operating range. The examined system consists of more parallelly connected low pressure turbine casings so-called diabolo that having at least two exhausts separated at the steam side. The exhausts, utilizing varying input-temperature coolant, are connected to the condensers that are separated at the steam side and serially connected at the coolant side. The casings have the same inlet areas while the exhausts have different areas resulting different volume flows and temperature operating range. The economic advantage of this solution approaches the savings between the serially connected direct-contact condensers and condensers in parallel of a dry cooling system. It can be proven by a simple calculation using the ambient air temperature duration diagram that is presented in the paper. (author)

Device and Container for Reheating and Sterilization

Science.gov (United States)

Sastry, Sudhir K.; Heskitt, Brian F.; Jun, Soojin; Marcy, Joseph E.; Mahna, Ritesh

2012-01-01

Long-duration space missions require the development of improved foods and novel packages that do not represent a significant disposal issue. In addition, it would also be desirable if rapid heating technologies could be used on Earth as well, to improve food quality during a sterilization process. For this purpose, a package equipped with electrodes was developed that will enable rapid reheating of contents via ohmic heating to serving temperature during space vehicle transit. Further, the package is designed with a resealing feature, which enables the package, once used, to contain and sterilize waste, including human waste for storage prior to jettison during a long-duration mission. Ohmic heating is a technology that has been investigated on and off for over a century. Literature indicates that foods processed by ohmic heating are of superior quality to their conventionally processed counterparts. This is due to the speed and uniformity of ohmic heating, which minimizes exposure of sensitive materials to high temperatures. In principle, the material may be heated rapidly to sterilization conditions, cooled rapidly, and stored. The ohmic heating device herein is incorporated within a package. While this by itself is not novel, a reusable feature also was developed with the intent that waste may be stored and re-sterilized within the packages. These would then serve a useful function after their use in food processing and storage. The enclosure should be designed to minimize mass (and for NASA's purposes, Equivalent System Mass, or ESM), while enabling the sterilization function. It should also be electrically insulating. For this reason, Ultem high-strength, machinable electrical insulator was used.

High Temperatures Health Monitoring of the Condensed Water Height in Steam Pipe Systems

Science.gov (United States)

Lih, Shyh-Shiuh; Bar-Cohen, Yoseph; Lee, Hyeong Jae; Badescu, Mircea; Bao, Xiaoqi; Sherrit, Stewart; Takano, Nobuyuki; Ostlund, Patrick; Blosiu, Julian

2013-01-01

Ultrasonic probes were designed, fabricated and tested for high temperature health monitoring system. The goal of this work was to develop the health monitoring system that can determine the height level of the condensed water through the pipe wall at high temperature up to 250 deg while accounting for the effects of surface perturbation. Among different ultrasonic probe designs, 2.25 MHz probes with air backed configuration provide satisfactory results in terms of sensitivity, receiving reflections from the target through the pipe wall. A series of tests were performed using the air-backed probes under irregular conditions, such as surface perturbation and surface disturbance at elevated temperature, to qualify the developed ultrasonic system. The results demonstrate that the fabricated air-backed probes combined with advanced signal processing techniques offer the capability of health monitoring of steam pipe under various operating conditions.

Study on Relative COP Changes with Increasing Heat Input Temperatures of Double Effect Steam Absorption Chillers

Directory of Open Access Journals (Sweden)

Abd Majid Mohd Amin

2016-01-01

Full Text Available Absorption chillers at cogeneration plants generate chilled water using steam supplied by heat recovery steam generators. The chillers are mainly of double effect type. The COP of double effect varies from 0.7 to 1.2 depending on operation and maintenance practices of the chillers. Heat input to the chillers during operations could have impact on the COP of the chillers. This study is on relative COP changes with increasing the heat input temperatures for a steam absorption chiller at a gas fueled cogeneration plant. Reversible COP analysis and zero order model were used for evaluating COP of the chiller for 118 days operation period. Results indicate increasing COP trends for both the reversible COP and zero model COP. Although the zero model COP are within the range of double effect absorption chiller, it is not so for the actual COP. The actual COP is below the range of normal double effect COP. It is recommended that economic replacement analysis to be undertaken to assess the feasibility either to repair or replace the existing absorption chiller.

Gravitino or axino dark matter with reheat temperature as high as 10{sup 16} GeV

Energy Technology Data Exchange (ETDEWEB)

Co, Raymond T. [Berkeley Center for Theoretical Physics, Department of Physics, University of California,366 LeConte Hall MC 7300, Berkeley, CA 94720 (United States); Theoretical Physics Group, Lawrence Berkeley National Laboratory,1 Cyclotron Rd., Berkeley, CA 94720 (United States); D’Eramo, Francesco [Department of Physics, University of California Santa Cruz,1156 High Street, Santa Cruz, CA 95064 (United States); Santa Cruz Institute for Particle Physics,1156 High Street, Santa Cruz, CA 95064 (United States); Hall, Lawrence J. [Berkeley Center for Theoretical Physics, Department of Physics, University of California,366 LeConte Hall MC 7300, Berkeley, CA 94720 (United States); Theoretical Physics Group, Lawrence Berkeley National Laboratory,1 Cyclotron Rd., Berkeley, CA 94720 (United States)

2017-03-01

A new scheme for lightest supersymmetric particle (LSP) dark matter is introduced and studied in theories of TeV supersymmetry with a QCD axion, a, and a high reheat temperature after inflation, T{sub R}. A large overproduction of axinos (ã) and gravitinos (G̃) from scattering at T{sub R}, and from freeze-in at the TeV scale, is diluted by the late decay of a saxion condensate that arises from inflation. The two lightest superpartners are ã, with mass of order the TeV scale, and G̃ with mass m{sub 3/2} anywhere between the keV and TeV scales, depending on the mediation scale of supersymmetry breaking. Dark matter contains both warm and cold components: for G̃ LSP the warm component arises from ã→G̃a, while for ã LSP the warm component arises from G̃→ãa. The free-streaming scale for the warm component is predicted to be of order 1 Mpc (and independent of m{sub 3/2} in the case of G̃ LSP). T{sub R} can be as high as 10{sup 16} GeV, for any value of m{sub 3/2}, solving the gravitino problem. The PQ symmetry breaking scale V{sub PQ} depends on T{sub R} and m{sub 3/2} and can be anywhere in the range (10{sup 10}−10{sup 16}) GeV. Detailed predictions are made for the lifetime of the neutralino LOSP decaying to ã+h/Z and G̃+h/Z/γ, which is in the range of (10{sup −1}−10{sup 6})m over much of parameter space. For an axion misalignment angle of order unity, the axion contribution to dark matter is sub-dominant, except when V{sub PQ} approaches 10{sup 16} GeV.

Study on hydrogen production by high temperature electrolysis of steam

International Nuclear Information System (INIS)

Hino, Ryutaro; Aita, Hideki; Sekita, Kenji; Haga, Katsuhiro; Iwata, Tomo-o.

1997-09-01

In JAERI, design and R and D works on hydrogen production process have been conducted for connecting to the HTTR under construction at the Oarai Research Establishment of JAERI as a nuclear heat utilization system. As for a hydrogen production process by high-temperature electrolysis of steam, laboratory-scale experiments were carried out with a practical electrolysis tube with 12 cells connected in series. Hydrogen was produced at a maximum density of 44 Nml/cm 2 h at 950degC, and know-how of operational procedures and operational experience were also accumulated. Thereafter, a planar electrolysis cell supported by a metallic plate was fabricated in order to improve hydrogen production performance and durability against thermal cycles. In the preliminary test with the planar cell, hydrogen has been produced continuously at a maximum density of 33.6 Nml/cm 2 h at an electrolysis temperature of 950degC. This report presents typical test results mentioned above, a review of previous studies conducted in the world and R and D items required for connecting to the HTTR. (author)

Thermal Efficiency of Cogeneration Units with Multi-Stage Reheating for Russian Municipal Heating Systems

Directory of Open Access Journals (Sweden)

Evgeny Lisin

2016-04-01

Full Text Available This paper explores the layout of an optimum process for supplying heat to Russian municipal heating systems operating in a market environment. We analyze and compare the standard cogeneration unit design with two-stage reheating of service water coming from controlled extraction locations and layouts that employ three in-line reheaters with heat the supply controlled by a rotary diaphragm and qualitative/quantitative methods (so-called “uncontrolled extraction”. Cogeneration unit designs are benchmarked in terms of their thermal efficiency expressed as a fuel consumption rate. The specific fuel consumption rate on electricity production is viewed as a key parameter of thermal efficiency.

TEM/STEM study of Zircaloy-2 with protective FeAl(Cr) layers under simulated BWR environment and high-temperature steam exposure

Science.gov (United States)

Park, Donghee; Mouche, Peter A.; Zhong, Weicheng; Mandapaka, Kiran K.; Was, Gary S.; Heuser, Brent J.

2018-04-01

FeAl(Cr) thin-film depositions on Zircaloy-2 were studied using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) with respect to oxidation behavior under simulated boiling water reactor (BWR) conditions and high-temperature steam. Columnar grains of FeAl with Cr in solid solution were formed on Zircaloy-2 coupons using magnetron sputtering. NiFe2O4 precipitates on the surface of the FeAl(Cr) coatings were observed after the sample was exposed to the simulated BWR environment. High-temperature steam exposure resulted in grain growth and consumption of the FeAl(Cr) layer, but no delamination at the interface. Outward Al diffusion from the FeAl(Cr) layer occurred during high-temperature steam exposure (700 °C for 3.6 h) to form a 100-nm-thick alumina oxide layer, which was effective in mitigating oxidation of the Zircaloy-2 coupons. Zr intermetallic precipitates formed near the FeAl(Cr) layer due to the inward diffusion of Fe and Al. The counterflow of vacancies in response to the Al and Fe diffusion led to porosity within the FeAl(Cr) layer.

Application of flexible micro temperature sensor in oxidative steam reforming by a methanol micro reformer.

Science.gov (United States)

Lee, Chi-Yuan; Lee, Shuo-Jen; Shen, Chia-Chieh; Yeh, Chuin-Tih; Chang, Chi-Chung; Lo, Yi-Man

2011-01-01

Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS) technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM), with the relevant parameters optimized as well.

Application of Flexible Micro Temperature Sensor in Oxidative Steam Reforming by a Methanol Micro Reformer

Directory of Open Access Journals (Sweden)

Yi-Man Lo

2011-02-01

Full Text Available Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM, with the relevant parameters optimized as well.

Thermal hydraulic studies in steam generator test facility

International Nuclear Information System (INIS)

Vinod, V.; Suresh Kumar, V.A.; Noushad, I.B.; Ellappan, T.R.; Rajan, K.K.; Rajan, M.; Vaidyanathan, G.

2005-01-01

Full text of publication follows: A 500 MWe fast breeder reactor is being constructed at Kalpakkam, India. This is a sodium cooled reactor with two primary and two secondary sodium loops with total 8 steam generators. The typical advantage of fast breeder plants is the high operating temperature of steam cycles and the high plant efficiency. To produce this high pressure and high temperature steam, once through straight tube vertical sodium heated steam generators are used. The steam is generated from the heat produced in the reactor core and being transported through primary and secondary sodium circuits. The steam generator is a 25 m high middle supported steam generator with expansion bend and 23 m heat transfer length. Steam Generator Test Facility (SGTF) constructed at Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam aims at performing various tests on a 5.5 MWt steam generator. This vertically simulated test article is similar in all respects to the proposed 157 MWt steam generator module for the Prototype Fast Breeder Reactor (PFBR), with reduced number of tubes. Heat transfer performance tests are done with this 19 tube steam generator at various load conditions. Sodium circuit for the SGTF is equipped with oil fired heater as heat source and centrifugal sodium pump, to pump sodium at 105 m 3 /hr flow rate. Other typical components like sodium to air heat exchanger, sodium purification system and hydrogen leak detection system is also present in the sodium circuit. High pressure steam produced in the steam generator is dumped in a condenser and recycled. Important tests planned in SGTF are the heat transfer performance test, stability test, endurance test and performance test of steam generator under various transients. The controlled operation of steam generator will be studied with possible control schemes. A steady state simulation of the steam generator is done with a mathematical model. This paper gives the details of heat transfer

Genetic optimization of steam multi-turbines system

International Nuclear Information System (INIS)

Olszewski, Pawel

2014-01-01

Optimization analysis of partially loaded cogeneration, multiple-stages steam turbines system was numerically investigated by using own-developed code (C++). The system can be controlled by following variables: fresh steam temperature, pressure, and flow rates through all stages in steam turbines. Five various strategies, four thermodynamics and one economical, which quantify system operation, were defined and discussed as an optimization functions. Mathematical model of steam turbines calculates steam properties according to the formulation proposed by the International Association for the Properties of Water and Steam. Genetic algorithm GENOCOP was implemented as a solving engine for non–linear problem with handling constrains. Using formulated methodology, example solution for partially loaded system, composed of five steam turbines (30 input variables) with different characteristics, was obtained for five strategies. The genetic algorithm found multiple solutions (various input parameters sets) giving similar overall results. In real application it allows for appropriate scheduling of machine operation that would affect equable time load of every system compounds. Also based on these results three strategies where chosen as the most complex: the first thermodynamic law energy and exergy efficiency maximization and total equivalent energy minimization. These strategies can be successfully used in optimization of real cogeneration applications. - Highlights: • Genetic optimization model for a set of five various steam turbines was presented. • Four various thermodynamic optimization strategies were proposed and discussed. • Operational parameters (steam pressure, temperature, flow) influence was examined. • Genetic algorithm generated optimal solutions giving the best estimators values. • It has been found that similar energy effect can be obtained for various inputs

Inflation and reheating in induced-gravity models

International Nuclear Information System (INIS)

Barr, S.; Segre, G.

1990-01-01

The Planck mass is generated dynamically in induced-gravity models, typically being related to the vacuum expectation value of a scalar field φ, ε 1/2 left-angle φ right-angle=M Pl / √8π , where ε is a dimensionless parameter, typically smaller than one. We discuss in this paper the decay of the φ particle, which is mainly into gravitons, and the consequences this has for models in which the φ field is responsible for inflation. We show in particular that too much energy is stored in φ oscillations and adequate reheating does not occur

PMK-2. Experimental study on steam generator behaviour

Energy Technology Data Exchange (ETDEWEB)

Ezsoel, G.; Szabados, L.; Trosztel, I. [KFKI Atomic Energy Research Inst., Budabest (Hungary)

1995-12-31

The PMK-2 is a full pressure scaled-down model of the Paks Nuclear Power Plant, with a 1:2070 scaling ratio for the volume and power. It has a steam generator model which is a vertical section of the horizontal steam generator. The model has hot and cold collectors similarly to the steam generators of the plant. The heat transfer tubes are horizontal tubes. There are 82 rows of tubes and the elevations, as well as the heat transfer surface distribution is the same as in the plant. The elevation of the feed water supply is similar to that of the plant. To study the temperature distribution in both the primary and the secondary side several thermocouples are built in, in addition to the overall instrumentation of the loop which has again a high number of measurement channels. Paper gives a description and results of SPE-4, with special respect to the steam generator behaviour in both steady state and transient conditions. Axial distribution of coolant and feedwater temperatures are given for the primary and the secondary side of hot and cold collectors and the temperature distribution in the centre of steam generator. (orig.).

PMK-2. Experimental study on steam generator behaviour

Energy Technology Data Exchange (ETDEWEB)

Ezsoel, G; Szabados, L; Trosztel, I [KFKI Atomic Energy Research Inst., Budabest (Hungary)

1996-12-31

The PMK-2 is a full pressure scaled-down model of the Paks Nuclear Power Plant, with a 1:2070 scaling ratio for the volume and power. It has a steam generator model which is a vertical section of the horizontal steam generator. The model has hot and cold collectors similarly to the steam generators of the plant. The heat transfer tubes are horizontal tubes. There are 82 rows of tubes and the elevations, as well as the heat transfer surface distribution is the same as in the plant. The elevation of the feed water supply is similar to that of the plant. To study the temperature distribution in both the primary and the secondary side several thermocouples are built in, in addition to the overall instrumentation of the loop which has again a high number of measurement channels. Paper gives a description and results of SPE-4, with special respect to the steam generator behaviour in both steady state and transient conditions. Axial distribution of coolant and feedwater temperatures are given for the primary and the secondary side of hot and cold collectors and the temperature distribution in the centre of steam generator. (orig.).

Steam reforming of light oxygenates

DEFF Research Database (Denmark)

Trane-Restrup, Rasmus; Resasco, Daniel E; Jensen, Anker Degn

2013-01-01

Steam reforming (SR) of ethanol, acetic acid, acetone, acetol, 1-propanol, and propanal has been investigated over Ni/MgAl2O4 at temperatures between 400 and 700 degrees C and at a steam-to-carbon-ratio (S/C) of 6. The yield of H-2 and conversion increased with temperature, while the yield of by-...... of CH4. Significant deactivation of the catalyst was observed for all of the compounds and was mainly due to carbon formation. The carbon formation was highest for alcohols due to a high formation of olefins, which are potent coke precursors....

AMPTRACT: an algebraic model for computing pressure tube circumferential and steam temperature transients under stratified channel coolant conditions

International Nuclear Information System (INIS)

Gulshani, P.; So, C.B.

1986-10-01

In a number of postulated accident scenarios in a CANDU reactor, some of the horizontal fuel channels are predicted to experience periods of stratified channel coolant condition which can lead to a circumferential temperature gradient around the pressure tube. To study pressure tube strain and integrity under stratified flow channel conditions, it is, necessary to determine the pressure tube circumferential temperature distribution. This paper presents an algebraic model, called AMPTRACT (Algebraic Model for Pressure Tube TRAnsient Circumferential Temperature), developed to give the transient temperature distribution in a closed form. AMPTRACT models the following modes of heat transfer: radiation from the outermost elements to the pressure tube and from the pressure to calandria tube, convection between the fuel elements and the pressure tube and superheated steam, and circumferential conduction from the exposed to submerged part of the pressure tube. An iterative procedure is used to solve the mass and energy equations in closed form for axial steam and fuel-sheath transient temperature distributions. The one-dimensional conduction equation is then solved to obtain the pressure tube circumferential transient temperature distribution in a cosine series expansion. In the limit of large times and in the absence of convection and radiation to the calandria tube, the predicted pressure tube temperature distribution reduces identically to a parabolic profile. In this limit, however, radiation cannot be ignored because the temperatures are generally high. Convection and radiation tend to flatten the parabolic distribution

Direct Digital Control Study.

Science.gov (United States)

1985-02-01

Deck - Cold Deck Reset Reheat Coil Reset Steam Boiler Optimization [lot Water Outside Air Reset Chiller Optimization Chiller Water Temperature Reset...with programming techniques for each type of installed DDC in order to effect changes in operating setpoints and application programs. *Communication...can be changed without recailbration of instrumentation devices. Changes to the application software, operating setpoints and parameters require the

Redox-reversible perovskite ferrite cathode for high temperature solid oxide steam electrolyser

International Nuclear Information System (INIS)

Li, Zhe; Li, Shisong; Tseng, Chung-Jen; Tao, Shanwen; Xie, Kui

2017-01-01

Highlights: • Redox reversible ferrite cathode is demonstrated for solid oxide electrolyser. • Promising electrical conductivity is obtained with Pr doping in hydrogen. • High performance of steam electrolysis is achieved with ferrite cathode. - Abstract: In this work, perovskite Sr 1−x Pr x FeO 3-δ (SPF) (x = 0.02, 0.04, 0.06, 0.08 and 0.10) are investigated and employed as solid oxide steam electrolyser cathode at 800 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM) analysis together indicate that the Sr 1−x Pr x FeO 3-δ is redox reversible with a phase transition from cubic to orthorhombic structure in redox cycles. The doping of Pr in A site has remarkably enhanced the electronic conduction to 1.0–1.2 S cm −1 at intermediate temperatures in reducing atmosphere. Electrochemical measurements demonstrate that the polarization resistance with Sr 0.96 Pr 0.04 FeO 3-δ electrode shows the lowest values of 0.25 Ω cm 2 in symmetric cells in reducing atmosphere at 800 °C. Direct steam electrolysis with Sr 0.96 Pr 0.04 FeO 3-δ cathode shows a current density of 1.64 A cm −2 at 2.0 V when fed with 5%H 2 O/Ar. The hydrogen production rate reaches 4.73, 6.68, 8.35 and 10.23 mL min −1 cm −2 at 1.4, 1.6, 1.8, 2.0 V, respectively, while the highest Faraday efficiency is as high as 97.16% at 1.8 V.

ANALYSIS OF EXERGY PARAMETERS OF BIOGAS POWER PLANT

Directory of Open Access Journals (Sweden)

Denysova A.E.

2014-08-01

Full Text Available The techniques of an exergy analysis concerning various circuits of biogas units, which allows replacing traditional energy resources and improving environmental conditions, has been presented. The heat schemes of biogas units were proposed, and analysis of their effectiveness was made. The comparison of different cycle parameters of various biogas units (i.e. a combustion turbine unit, a combined cycle gas turbine unit with gas discharges into the boiler and a combined cycle gas turbine with a high-temperature vapor generator and a reheating stage was made, and the comparison of their exergy characteristics was carried out. The results of exergy analysis had demonstrated that the cycle of biogas CCGT (combined cycle gas turbine with a reheating stage and using a high-pressure steam generator is the most effective, that can be explained by the fact that the thermal energy proportions of combustion products, accounting for the steam cycle and the gas cycle are approximately equal, comparing to conventional combined cycle gas turbine units.

Hypercharged dark matter and direct detection as a probe of reheating.

Science.gov (United States)

Feldstein, Brian; Ibe, Masahiro; Yanagida, Tsutomu T

2014-03-14

The lack of new physics at the LHC so far weakens the argument for TeV scale thermal dark matter. On the other hand, heavier, nonthermal dark matter is generally difficult to test experimentally. Here we consider the interesting and generic case of hypercharged dark matter, which can allow for heavy dark matter masses without spoiling testability. Planned direct detection experiments will be able to see a signal for masses up to an incredible 1010  GeV, and this can further serve to probe the reheating temperature up to about 109  GeV, as determined by the nonthermal dark matter relic abundance. The Z-mediated nature of the dark matter scattering may be determined in principle by comparing scattering rates on different detector nuclei, which in turn can reveal the dark matter mass. We will discuss the extent to which future experiments may be able to make such a determination.

Thermal energy storage and utilization system

International Nuclear Information System (INIS)

1976-01-01

The power output from a nuclear power plant or fossil fuel power plant operating under constant reactor (or furnace) and boiler conditions is varied by regulating the rate of turbine extraction steam and primary high pressure steam used to heat boiler feed water (BFW). During periods of low power demand, excess extraction steam is drawn off to heat excess quantities of boiler feed water. Such boiler feed water can be heated to the maximum extent possible and used to reheat interstage steam before being sent at slightly reduced temperature to the boilers. In this way, maximum use can be made of the thermal energy stored in the low vapor pressure organic material. Alternatively, or simultaneously, the stored hot LVP organic material can be used to raise intermediate pressure steam and this steam can be injected into the steam turbines between appropriate stages or into auxiliary turbines used solely for this purpose

Numerical Research of Steam and Gas Plant Efficiency of Triple Cycle for Extreme North Regions

Directory of Open Access Journals (Sweden)

Galashov Nikolay

2016-01-01

Full Text Available The present work shows that temperature decrease of heat rejection in a cycle is necessary for energy efficiency of steam turbine plants. Minimum temperature of heat rejection at steam turbine plant work on water steam is 15°C. Steam turbine plant of triple cycle where lower cycle of steam turbine plant is organic Rankine cycle on low-boiling substance with heat rejection in air condenser, which safely allows rejecting heat at condensation temperatures below 0°C, has been offered. Mathematical model of steam and gas plant of triple cycle, which allows conducting complex researches with change of working body appearance and parameters defining thermodynamic efficiency of cycles, has been developed. On the basis of the model a program of parameters and index cycles design of steam and gas plants has been developed in a package of electron tables Excel. Numerical studies of models showed that energy efficiency of steam turbine plants of triple cycle strongly depend on low-boiling substance type in a lower cycle. Energy efficiency of steam and gas plants net 60% higher can be received for steam and gas plants on the basis of gas turbine plant NK-36ST on pentane and its condensation temperature below 0°C. It was stated that energy efficiency of steam and gas plants net linearly depends on condensation temperature of low-boiling substance type and temperature of gases leaving reco very boiler. Energy efficiency increases by 1% at 10% decrease of condensation temperature of pentane, and it increases by 0.88% at 15°C temperature decrease of gases leaving recovery boiler.

Steam Oxidation Testing in the Severe Accident Test Station

Energy Technology Data Exchange (ETDEWEB)

Pint, Bruce A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-08-01

After the March 2011 accident at Fukushima Daiichi, Oak Ridge National Laboratory (ORNL) began conducting high temperature steam oxidation testing of candidate materials for accident tolerant fuel (ATF) cladding in August 2011 [1-11]. The ATF concept is to enhance safety margins in light water reactors (LWR) during severe accident scenarios by identifying materials with 100× slower steam oxidation rates compared to current Zr-based alloys. In 2012, the ORNL laboratory equipment was expanded and made available to the entire ATF community as the Severe Accident Test Station (SATS) [4,12]. Compared to the current UO2/Zr-based alloy fuel system, an ATF alternative would significantly reduce the rate of heat and hydrogen generation in the core during a coolant-limited severe accident [13-14]. The steam oxidation behavior of candidate materials is a key metric in the evaluation of ATF concepts and also an important input into models [15-17]. However, initial modeling work of FeCrAl cladding has used incomplete information on the physical properties of FeCrAl. Also, the steam oxidation data being collected at 1200°-1700°C is unique as no prior work has considered steam oxidation of alloys at such high temperatures. Also, because many accident scenarios include steadily increasing temperatures, the required data are not traditional isothermal exposures but exposures with varying “ramp” rates. In some cases, the steam oxidation behavior has been surprising and difficult to interpret. Thus, more fundamental information continues to be collected. In addition, more work continues to focus on commercially-manufactured tube material. This report summarizes recent work to characterize the behavior of candidate alloys exposed to high temperature steam, evaluate steam oxidation behavior in various ramp scenarios and continue to collect integral data on FeCrAl compared to conventional Zr-based cladding.

Gas--steam turbine combined cycle power plants

Energy Technology Data Exchange (ETDEWEB)

Christian, J.E.

1978-10-01

The purpose of this technology evaluation is to provide performance and cost characteristics of the combined gas and steam turbine, cycle system applied to an Integrated Community Energy System (ICES). To date, most of the applications of combined cycles have been for electric power generation only. The basic gas--steam turbine combined cycle consists of: (1) a gas turbine-generator set, (2) a waste-heat recovery boiler in the gas turbine exhaust stream designed to produce steam, and (3) a steam turbine acting as a bottoming cycle. Because modification of the standard steam portion of the combined cycle would be necessary to recover waste heat at a useful temperature (> 212/sup 0/F), some sacrifice in the potential conversion efficiency is necessary at this temperature. The total energy efficiency ((electric power + recovered waste heat) divided by input fuel energy) varies from about 65 to 73% at full load to 34 to 49% at 20% rated electric power output. Two major factors that must be considered when installing a gas--steam turbine combines cycle are: the realiability of the gas turbine portion of the cycle, and the availability of liquid and gas fuels or the feasibility of hooking up with a coal gasification/liquefaction process.

Oxidation behaviour of titanium in high temperature steam

Energy Technology Data Exchange (ETDEWEB)

Moroishi, T; Shida, Y [Sumitomo Metal Industries Ltd., Amagasaki, Hyogo (Japan). Central Research Labs.

1978-03-01

The oxidation of pure titanium was studied in superheated steam at 400 -- 550/sup 0/C. The effects of prior cold working and several heat treatment conditions on the oxidation were examined and also the effects of the addition of small amounts of iron and oxygen were investigated. The oxidation mechanism of pure titanium is discussed in relation to the scale structure and the oxidation kinetics. Hydrogen absorption rate was also measured. As a result, the following conclusions were drawn: (1) The oxidation of pure titanium in steam was faster than in air and breakaway oxidation was observed above 500/sup 0/C after the specimen had gained a certain weight. Prior cold working and heat treatment conditions scarcely affected the oxidation rate, whereas the specimen containing small amounts of iron and oxygen showed a little more rapid oxidation. (2) At 500 and 550/sup 0/C a dark grey inner scale and a yellow-brown outer scale were formed. The outer scale was apt to exfoliate after the occurrence of breakaway oxidation. At 400 and 450/sup 0/C only a dark grey scale was observed. All of these oxides were identified as the rutile type, TiO/sub 2/. Furthermore, the presence of a thin and uniform oxygen rich layer beneath the external scale was confirmed at all test temperatures. (3) The measured weight gain approximately followed the cubic rate law; this would be expected for the following reason; one component of the weight gain is due to the dissolved oxygen, the amount of which remains constant after the early stages of oxidation. The second component is due to the parabolic growth of the external TiO/sub 2/ scale. When these contributions are added a pseudo-cubic weight gain curve results. (4) It was shown that 50 percent of the hydrogen generated during the oxidation was absorbed into the metal.

Steam Reformer With Fibrous Catalytic Combustor

Science.gov (United States)

Voecks, Gerald E.

1987-01-01

Proposed steam-reforming reactor derives heat from internal combustion on fibrous catalyst. Supplies of fuel and air to combustor controlled to meet demand for heat for steam-reforming reaction. Enables use of less expensive reactor-tube material by limiting temperature to value safe for material yet not so low as to reduce reactor efficiency.

Thermodynamics of Hydrogen Production from Dimethyl Ether Steam Reforming and Hydrolysis

Energy Technology Data Exchange (ETDEWEB)

T.A. Semelsberger

2004-10-01

The thermodynamic analyses of producing a hydrogen-rich fuel-cell feed from the process of dimethyl ether (DME) steam reforming were investigated as a function of steam-to-carbon ratio (0-4), temperature (100 C-600 C), pressure (1-5 atm), and product species: acetylene, ethanol, methanol, ethylene, methyl-ethyl ether, formaldehyde, formic acid, acetone, n-propanol, ethane and isopropyl alcohol. Results of the thermodynamic processing of dimethyl ether with steam indicate the complete conversion of dimethyl ether to hydrogen, carbon monoxide and carbon dioxide for temperatures greater than 200 C and steam-to-carbon ratios greater than 1.25 at atmospheric pressure (P = 1 atm). Increasing the operating pressure was observed to shift the equilibrium toward the reactants; increasing the pressure from 1 atm to 5 atm decreased the conversion of dimethyl ether from 99.5% to 76.2%. The order of thermodynamically stable products in decreasing mole fraction was methane, ethane, isopropyl alcohol, acetone, n-propanol, ethylene, ethanol, methyl-ethyl ether and methanol--formaldehyde, formic acid, and acetylene were not observed. The optimal processing conditions for dimethyl ether steam reforming occurred at a steam-to-carbon ratio of 1.5, a pressure of 1 atm, and a temperature of 200 C. Modeling the thermodynamics of dimethyl ether hydrolysis (with methanol as the only product considered), the equilibrium conversion of dimethyl ether is limited. The equilibrium conversion was observed to increase with temperature and steam-to-carbon ratio, resulting in a maximum dimethyl ether conversion of approximately 68% at a steam-to-carbon ratio of 4.5 and a processing temperature of 600 C. Thermodynamically, dimethyl ether processed with steam can produce hydrogen-rich fuel-cell feeds--with hydrogen concentrations exceeding 70%. This substantiates dimethyl ether as a viable source of hydrogen for PEM fuel cells.

Effect of thermal barrier coatings on the performance of steam and water-cooled gas turbine/steam turbine combined cycle system

Science.gov (United States)

Nainiger, J. J.

1978-01-01

An analytical study was made of the performance of air, steam, and water-cooled gas-turbine/steam turbine combined-cycle systems with and without thermal-barrier coatings. For steam cooling, thermal barrier coatings permit an increase in the turbine inlet temperature from 1205 C (2200 F), resulting in an efficiency improvement of 1.9 percentage points. The maximum specific power improvement with thermal barriers is 32.4 percent, when the turbine inlet temperature is increased from 1425 C (2600 F) to 1675 C (3050 F) and the airfoil temperature is kept the same. For water cooling, the maximum efficiency improvement is 2.2 percentage points at a turbine inlet temperature of 1683 C (3062 F) and the maximum specific power improvement is 36.6 percent by increasing the turbine inlet temperature from 1425 C (2600 F) to 1730 C (3150 F) and keeping the airfoil temperatures the same. These improvements are greater than that obtained with combined cycles using air cooling at a turbine inlet temperature of 1205 C (2200 F). The large temperature differences across the thermal barriers at these high temperatures, however, indicate that thermal stresses may present obstacles to the use of coatings at high turbine inlet temperatures.

Comments on US LMFBR steam generator base technology

International Nuclear Information System (INIS)

Simmons, W.R.

1984-01-01

The development of steam generators for the LMFBR was recognized from the onset by the AEC, now DOE, as a difficult, challenging, and high-priority task. The highly reactive nature of sodium with water/steam requires that the sodium-water/steam boundaries of LMFBR steam generators possess a degree of leak-tightness reliability not normally attempted on a commercial scale. In addition, the LMFBR steam generator is subjected to high fluid temperatures and severe thermal transients. These requirements place great demand on materials, fabrication processes, and inspection methods; and even greater demands on the designer to provide steam generators that can meet these demanding requirements, be fabricated without unreasonable shop requirements, and tolerate off-normal effects

MHTGR steam generator on-line heat balance, instrumentation and function

International Nuclear Information System (INIS)

Klapka, R.E.; Howard, W.W.; Etzel, K.T.; Basol, M.; Karim, N.U.

1991-09-01

Instrumentation is used to measure the Modular High Temperature Gas-Cooled Reactor (MHTGR) steam generator dissimilar metal weld temperature during start-up testing. Additional instrumentation is used to determine an on-line heat balance which is maintained during the 40 year module life. In the process of calibrating the on-line heat balance, the helium flow is adjusted to yield the optimum boiling level in the steam generator relative to the dissimilar metal weld. After calibration is complete the weld temperature measurement is non longer required. The reduced boiling level range results in less restrictive steam generator design constraints

Numerical simulations of pressure fluctuations at branch piping in BWR main steam line

International Nuclear Information System (INIS)

Morita, Ryo; Inada, Fumio; Yoshikawa, Kazuhiro; Takahashi, Shiro

2009-01-01

The power uprating of a nuclear power plant may increase/accelerate degradation phenomena such as flow-induced vibration and wall thinking. A steam dryer was damaged by a high cycle fatigue due to an acoustic-induced vibration at the branch piping of safety relief valves (SRVs) in main steam lines. In this study, we conducted the numerical simulations of steam/air flow around a simplified branch piping to clarify the basic characteristics of resonance. LES simulations were conducted in ordinary pressure/temperature air and steam under BWR plant conditions. In both cases, the excitation of the pressure fluctuations at the branch was observed under some inlet velocity conditions. These fluctuations and inlet conditions were normalized and the obtained results were compared. The normalized results showed that the range and maximum amplitude of pressure fluctuations were almost the same in low-pressure/temperature air and high-pressure/temperature steam. We found that ordinary pressure/temperature air experiments and simulations can possibly clarify the characteristics of the resonance in high-pressure/temperature steam. (author)

Development of technologies on innovative-simplified nuclear power plant using high-efficiency steam injectors (5) operating characteristics of center water jet type supersonic steam injector

International Nuclear Information System (INIS)

Abe, Y.; Kawamoto, Y.; Iwaki, C.; Narabayashi, T.; Mori, M.; Ohmori, S.

2005-01-01

Next-generation reactor systems have been under development aiming at simplified system and improvement of safety and credibility. A steam injector has a function of a passive pump without large motor or turbo-machinery, and has been investigated as one of the most important component of the next-generation reactor. Its performance as a pump depends on direct contact condensation phenomena between a supersonic steam and a sub-cooled water jet. As previous studies of the steam injector, there are studies about formulation of operating characteristic of steam injector and analysis of jet structure in steam injector by Narabayashi etc. And as previous studies of the direct contact condensation, there is the study about the direct contact condensation in steam atmosphere. However the study about the turbulent heat transfer under the great shear stress is not enough investigated. Therefore it is necessary to examine in detail about the operating characteristic of the steam injector. The present paper reports the observation results of the water jet behavior in the super sonic steam injector by using the video camera and the high-speed video camera. And the measuring results of the temperature and the pressure distribution in the steam injector are reported. From observation results by video camera, it is cleared that the water jet is established at the center of the steam injector right after steam supplied and the operation of the steam injector depends on the throat diameter. And from observation results by high-speed video camera, it is supposed that the columned water jet surface is established in the mixing nozzle and the water jet surface movement exists. And from temperature measuring results, it is supposed that the steam temperature at the mixing nozzle is changed between about 80 degree centigrade and about 60 degree centigrade. Then from the pressure measuring results, it is confirmed that the pressure at the diffuser depends on each the throat diameter and

Comparison of elastic and inelastic seismic response of high temperature piping systems

International Nuclear Information System (INIS)

Thomas, F.M.; McCabe, S.L.; Liu, Y.

1994-01-01

A study of high temperature power piping systems is presented. The response of the piping systems is determined when subjected to seismic disturbances. Two piping systems are presented, a main steam line, and a cold reheat line. Each of the piping systems are modeled using the ANSYS computer program and two analyses are performed on each piping system. First, each piping system is subjected to a seismic disturbance and the pipe material is assumed to remain linear and elastic. Next the analysis is repeated for each piping system when the pipe material is modeled as having elastic-plastic behavior. The results of the linear elastic analysis and elastic-plastic analysis are compared for each of the two pipe models. The pipe stresses, strains, and displacements, are compared. These comparisons are made so that the effect of the material yielding can be determined and to access what error is made when a linear analysis is performed on a system that yields

Temperature escalation in PWR fuel rod simulators due to the zircaloy/steam reaction ESSI-4 ESSI-11

International Nuclear Information System (INIS)

Hagen, S.; Kapulla, H.; Malauscheck, H.; Wallenfels, K.P.; Buescher, B.J.

1985-03-01

The tests had the initial heatup rate as main parameter. The experimental arrangement consisted of a fuel rod simulator (central tungsten heater, UO 2 ring pellets and zircaloy cladding), a zircaloy shroud and the fiber ceramic insulation. A steam flow of ca. 20 g/min was introduced at the lower end of the bundle. A temperature escalation was observed in every test. The maximum cladding surface temperature in the single rod tests never exceeded 2200 0 C. The escalation began in the upper region of the rods and moved down the rods, opposite to the direction of steam flow. For fast initial heatup rates, the runoff of molten zircaloy was a limiting process for the escalation. For slow heatup rates, the formation of a protective oxide layer reduced the reaction rate. The test with less insulation thickness showed a reduction of the escalation. A stronger influence was found for the gap between shroud and insulation. This is caused by convection heat losses to the steam circulating in this gap by natural convection. Removal of the gap between shroud and insulation in essentially the same experimental arrangement produced a faster escalation. The posttest appearance of the fuel rod simulators showed that, at slow heatup rates oxidation of the cladding was complete, and the fuel rod was relatively intact. Conversely, at fast heatup rates, relatively little cladding oxidation with extensive dissolution of the UO 2 pellets and runoff of molten cladding was observed. (orig./HP) [de

SUS 321 HTB boiler tubing with fire grained internal surface resistant to steam-induced oxidation

International Nuclear Information System (INIS)

Kanero, Takahiro; Minami, Yuusuke; Kodera, Toshihide

1981-01-01

Considerable amount of scale is produced by high temperature steam on the austenitic stainless steel tubes used for the superheaters and reheaters of large boilers for power generation. The scale of outer layer separates off due to the thermal stress at the time of starting-up and stopping, and causes the blocking of pipes and the erosion of turbine blades. Following the increase of nuclear power generation, large boilers are used for medium load, accordingly it is expected that the troubles like these increase. In this paper, the manufacturing method and the properties of SUS 321 HTB with fine grain internal surface are reported, which was developed to reduce the rate of growth of scale and to prevent the separation of scale. In order to prevent the separation of scale from austenitic stainless steel tubes, the reduction of scale thickness, surface treatment such as chrome plating, the use of alloys with excellent oxidation resistance, the formation of chrome-rich film rapidly, the heat treatment of cold-worked tubes and so on were carried out. The nitrification of SUS 321 H steel brought about two-phase structure of the fine grain internal surface with excellent oxidation resistance and the rest of coarse grains with high creep strength. (Kako, I.)

1000 MW steam turbine for nuclear power station

International Nuclear Information System (INIS)

Drahy, J.

1987-01-01

Skoda Works started the manufacture of the 1000 MW steam turbine for the Temelin nuclear power plant. The turbine will use saturated steam at 3,000 r.p.m. It will allow steam supply to heat water for district heating, this of an output of 893 MW for a three-stage water heating at a temperature of 150/60 degC or of 570 MW for a two-stage heating at a temperature of 120/60 degC. The turbine features one high-pressure and three identical low-pressure stages. The pressure gradient between the high-pressure and the low-pressure parts was optimized as concerns the thermal efficiency of the cycle and the thermodynamic efficiency of the low-pressure part. A value of 0.79 MPa was selected corresponding to the maximum flow rate of the steam entering the turbine. This is 5,495 t/h, the admission steam parameters are 273.3 degC and 5.8 MPa. The feed water temperature is 220.9 degC. It is expected that throughout the life of the turbine, there will be 300 cold starts, 1,000 starts following shutdown for 55 to 88 hours, and 600 starts following shutdown for 8 hours. (Z.M.). 8 figs., 1 ref

Testing installation for a steam generator

International Nuclear Information System (INIS)

Dubourg, M.

1985-01-01

The invention proposes a testing installation for a steam generator associated to a boiler, comprising a testing exchanger connected to a feeding circuit in secondary fluid and to a circuit to release the steam produced, and comprising a heating-tube bundle connected to a closed circuit of circulation of a primary coolant at the same temperature and at the pressure than the primary fluid. The heating-tube bundle of the testing exchanger has the same height than the primary bundle of the steam generator and the testing exchanger is at the same level and near the steam generator and is fed by the same secondary fluid such as it is subject to the same operation phases during a long period. The in - vention applies, more particularly, to the steam generators of pressurized water nuclear power plants [fr

Aluminium Alloy AA6060 surface treatment with high temperature steam containing chemical additives

DEFF Research Database (Denmark)

Din, Rameez Ud; Tabrizian, Naja; Jellesen, Morten S.

2015-01-01

The steam treatment process was employed to produce a conversion coating on aluminium alloy AA6060. The changes in microstructure and its effect on corrosion resistance properties were investigated. Various concentrations of KMnO4 containing Ce(NO3)3 was injected into the steam and its effect...... on the formation of steam-based conversion coating was evaluated. The use of Mn-Ce into the steam resulted in incorporation of these species into the conversion coating, which resulted in improved corrosion resistance of the alloy substrate....

Leptogenesis and reheating in complex hybrid inflation

International Nuclear Information System (INIS)

Martinez-Prieto, Carlos; Delepine, David; Urena-Lopez, L. Arturo

2010-01-01

We study the transformation into a baryon asymmetry of a charge initially stored in a complex (waterfall) scalar field at the end of a hybrid inflation phase as described by Delepine, Martinez, and Urena-Lopez [Phys. Rev. Lett. 98, 161302 (2007)]. The waterfall field is coupled to right-handed neutrinos, and is also responsible for their Majorana masses. The charge is finally transferred to the leptons of the standard model through the decay of the right-handed neutrinos without introducing new CP violating interactions. Other needed processes, like the decay of the inflaton field and the reheating of the Universe, are also discussed in detail.

The corrosion resistance of Zr-Nb and Zr-Nb-Sn alloys in high-temperature water and steam

International Nuclear Information System (INIS)

Dalgaard, S.B.

1960-03-01

An alloy of reactor-grade sponge zirconium-2.5 wt. % niobium was exposed to water and steam at high temperature. The corrosion was twice that of Zircaloy-2 while hydrogen pickup was found to be equal to that of Zircaloy-2. Ternary additions of tin to this alloy in the range 0.5-1.5 had no effect on the corrosion resistance in water at 315 o C up to 100 days. At higher temperatures, tin increased the corrosion, the effect varying with temperature. Heat treatment of the alloys was shown to affect corrosion resistance. (author)

The corrosion resistance of Zr-Nb and Zr-Nb-Sn alloys in high-temperature water and steam

Energy Technology Data Exchange (ETDEWEB)

Dalgaard, S B

1960-03-15

An alloy of reactor-grade sponge zirconium-2.5 wt. % niobium was exposed to water and steam at high temperature. The corrosion was twice that of Zircaloy-2 while hydrogen pickup was found to be equal to that of Zircaloy-2. Ternary additions of tin to this alloy in the range 0.5-1.5 had no effect on the corrosion resistance in water at 315{sup o}C up to 100 days. At higher temperatures, tin increased the corrosion, the effect varying with temperature. Heat treatment of the alloys was shown to affect corrosion resistance. (author)

The Grand Quevilly thermal test station - the SMW sodium circuit with a generator of superheated steam at 545 deg

International Nuclear Information System (INIS)

Robin, M.G.

1964-01-01

A 5 MW installation is described which is a reduced model of the heat exchange system of a sodium-cooled reactor. This plant, which is situated at Grand Quevilly (near Rouen), consists of: 1 - A primary sodium loop made up of a sodium re-heater running on heavy diesel oil, a mechanical pump and an intermediate exchanger made up of clusters of tubes fitted with baffles. 2 - A NaK(56 per cent of K) secondary loop consisting mainly of a mechanical pump and a double-wall steam generator with forced circulation and complete vaporization. 3 - A tertiary water loop consisting of the inside of the steam generator pipes, a pressure-reducing valve which cools down the super-heated fluid and acts as a turbine, a condenser, a charge-pump and a supply pump for the boiler. The heat is given finally to a water-source flowing into the Seine. Two important points of the installation are: - The water treatment unit - The control and regulation system Apart from the general satisfactory operation of the installation which it is hoped to obtain, a careful study will be made of the heat transmission coefficients of the important equipment such as the intermediate exchanger and the steam generator. The construction was finished on April 28, 1964. (author) [fr

New ferritic steels for advanced steam plants

Energy Technology Data Exchange (ETDEWEB)

Mayer, K H; Koenig, H [GEC ALSTHOM Energie GmbH, Nuremberg (Germany)

1999-12-31

During the last 15-20 years ferritic-martensitic 9-12 % chromium steels have been developed under international research programmes which permit inlet steam temperatures up to approx. 625 deg C and pressures up to about 300 bars, thus leading to improvements in thermal efficiency of around 8 % and a CO{sub 2} reduction of about 20 % versus conventional steam parameters. These new steels are already being applied in 13 European and 34 Japanese power stations with inlet steam temperature up to 610 deg C. This presentation will give an account of the content, scope and results of the research programmes and of the experience gained during the production of components which have been manufactured from the new steels. (orig.) 13 refs.

New ferritic steels for advanced steam plants

Energy Technology Data Exchange (ETDEWEB)

Mayer, K.H; Koenig, H. [GEC ALSTHOM Energie GmbH, Nuremberg (Germany)

1998-12-31

During the last 15-20 years ferritic-martensitic 9-12 % chromium steels have been developed under international research programmes which permit inlet steam temperatures up to approx. 625 deg C and pressures up to about 300 bars, thus leading to improvements in thermal efficiency of around 8 % and a CO{sub 2} reduction of about 20 % versus conventional steam parameters. These new steels are already being applied in 13 European and 34 Japanese power stations with inlet steam temperature up to 610 deg C. This presentation will give an account of the content, scope and results of the research programmes and of the experience gained during the production of components which have been manufactured from the new steels. (orig.) 13 refs.

Engineered for the energy future. I. Moisture separator-reheaters: extreme reliability an imperative

International Nuclear Information System (INIS)

Anon.

1976-01-01

A description is given of the design and development activities performed by Foster-Wheeler to insure operational reliability of sixteen moisture separator-reheaters being manufactured for eight twin-unit BWR power plants to be operated by TVA

Characterization of a steam plasma jet at atmospheric pressure

International Nuclear Information System (INIS)

Ni Guohua; Zhao Peng; Cheng Cheng; Song Ye; Meng Yuedong; Toyoda, Hirotaka

2012-01-01

An atmospheric steam plasma jet generated by an original dc water plasma torch is investigated using electrical and spectroscopic techniques. Because it directly uses the water used for cooling electrodes as the plasma-forming gas, the water plasma torch has high thermal efficiency and a compact structure. The operational features of the water plasma torch and the generation of the steam plasma jet are analyzed based on the temporal evolution of voltage, current and steam pressure in the arc chamber. The influence of the output characteristics of the power source, the fluctuation of the arc and current intensity on the unsteadiness of the steam plasma jet is studied. The restrike mode is identified as the fluctuation characteristic of the steam arc, which contributes significantly to the instabilities of the steam plasma jet. In addition, the emission spectroscopic technique is employed to diagnose the steam plasma. The axial distributions of plasma parameters in the steam plasma jet, such as gas temperature, excitation temperature and electron number density, are determined by the diatomic molecule OH fitting method, Boltzmann slope method and H β Stark broadening, respectively. The steam plasma jet at atmospheric pressure is found to be close to the local thermodynamic equilibrium (LTE) state by comparing the measured electron density with the threshold value of electron density for the LTE state. Moreover, based on the assumption of LTE, the axial distributions of reactive species in the steam plasma jet are estimated, which indicates that the steam plasma has high chemical activity.

Shiraz solar power plant operation with steam engine

International Nuclear Information System (INIS)

Yaghoubi, M.; Azizian, K.

2004-01-01

The present industrial developments and daily growing need of energy, as well as economical and environmental problem caused by fossil fuels consumption, resulted certain constraint for the future demand of energy. During the past two decades great attention has been made to use renewable energy for different sectors. In this regard for the first time in Iran, design and construction of a 250 K W Solar power plant in Shiraz, Iran is being carried out and it will go to operation within next year. The important elements of this power plant is an oil cycle and a steam cycle, and several studies have been done about design and operation of this power plant, both for steady state and transient conditions. For the steam cycle, initially a steam turbine was chosen and due to certain limitation it has been replaced by a steam engine. The steam engine is able to produce electricity with hot or saturated vapor at different pressures and temperatures. In this article, the effects of installing a steam engine and changing its vapor inlet pressure and also the effects of sending hot or saturated vapor to generate electricity are studied. Various cycle performance and daily electricity production are determined. The effects of oil cycle temperature on the collector field efficiency, and daily, monthly and annual amount of electricity production is calculated. Results are compared with the steam cycle output when it contains a steam turbine. It is found that with a steam engine it is possible to produce more annual electricity for certain conditions

Efficiency analysis of a hard-coal-fired supercritical power plant with a four-end high-temperature membrane for air separation

International Nuclear Information System (INIS)

Kotowicz, Janusz; Michalski, Sebastian

2014-01-01

The supercritical power plant analyzed in this paper consists of the following elements: a steam turbine, a hard-coal-fired oxy-type pulverized fuel boiler, an air separation unit with a four-end-type high-temperature membrane and a carbon dioxide capture unit. The electrical power of the steam turbine is 600 MW, the live steam thermodynamic parameters are 650°C/30 MPa, and the reheated steam parameters are 670°C/6 MPa. First of all the net efficiency was calculated as functions of the oxygen recovery rate. The net efficiency was lower than the reference efficiency by 9–10.5 pp, and a series of actions were thus proposed to reduce the loss of net efficiency. A change in the boiler structure produced an increase in the boiler efficiency of 2.5–2.74 pp. The range of the optimal air compressor pressure ratio (19–23) due to the net efficiency was also determined. The integration of all installations with the steam turbine produced an increase in the gross electric power by up to 50.5 MW. This operation enabled the replacement of the steam regenerative heat exchangers with gas–water heat exchangers. As a result of these alterations, the net efficiency of the analyzed power plant was improved to 5.5 pp less than the reference efficiency. - Highlights: • Analysis of a power plant with a “four-end” HTM for oxygen production was made. • Reorganization of the flue gas recirculation increased the boiler efficiency. • Optimization of the air compressor pressure ratio decreased the auxiliary power. • Replacement of the regenerative heat exchangers increased the gross electric power. • Comparison of the net efficiency of the analyzed and reference plants were made

Comparative Study on the Effects of Boiling, Steaming, Grilling, Microwaving and Superheated Steaming on Quality Characteristics of Marinated Chicken Steak

Science.gov (United States)

Choi, Yun-Sang; Kim, Young-Boong; Jeon, Ki-Hong; Kim, Eun-Mi; Sung, Jung-Min; Kim, Hyun-Wook

2016-01-01

The effects of five different cooking methods (boiling, steaming, grilling, microwaving, and superheated steaming) on proximate composition, pH, color, cooking loss, textural properties, and sensory characteristics of chicken steak were studied. Moisture content and lightness value (L*-value) were higher in superheated steam cooked chicken steak than that of the other cooking treatments such as boiling, steaming, grilling and microwaving cooking (pcooked chicken steak was lower than that in the other cooking treatments (pchicken steak cooked using various methods (p>0.05). Among the sensory characteristics, tenderness score, juiciness score and overall acceptability score were the highest for the superheated steam samples (p0.05). These results show that marinated chicken steak treated with superheated steam in a preheated 250℃ oven and 380℃ steam for 5 min until core temperature reached 75℃ improved the quality characteristics and sensory properties the best. Therefore, superheated steam was useful to improve cooked chicken steak. PMID:27499656

Water jet behavior in center water jet type supersonic steam injector

International Nuclear Information System (INIS)

Kawamoto, Y.; Abe, Y.

2005-01-01

Next-generation reactor systems have been under development aiming at simplified system and improvement of safety and credibility. A steam injector has a function of a passive pump without large motor or turbo-machinery, and has been investigated as one of the most important component of the next-generation reactor. Its performance as a pump depends on direct contact condensation phenomena between a supersonic steam and a sub-cooled water jet. As previous studies of the steam injector, there are studies about formulation of operating characteristic of steam injector and analysis of jet structure in steam injector by Narabayashi etc. And as previous studies of the direct contact condensation, there is the study about the direct contact condensation in steam atmosphere. However the study about the turbulent heat transfer under the great shear stress is not enough investigated. Therefore it is necessary to examine in detail about the operating characteristic of the steam injector. The present paper reports the observation results of the water jet behavior in the super sonic steam injector by using the video camera and the high-speed video camera. And the measuring results of the temperature and the pressure distribution in the steam injector are reported. From observation results by video camera, it is cleared that the water jet is established at the center of the steam injector right after steam supplied and the operation of the steam injector depends on the throat diameter. And from observation results by high-speed video camera, it is supposed that the columned water jet surface is established in the mixing nozzle and the water jet surface movement exists. Furthermore and effect of the non-condensable gas on the steam injector is investigated by measuring the radial temperature distributions in the water jet. From measuring results, it is supposed the more the air included in the steam, the more the temperature fluctuation of both steam and discharge water

Tuning and performance evaluation of PID controller for superheater steam temperature control of 200 MW boiler using gain phase assignment algorithm

Science.gov (United States)

Begum, A. Yasmine; Gireesh, N.

2018-04-01

In superheater, steam temperature is controlled in a cascade control loop. The cascade control loop consists of PI and PID controllers. To improve the superheater steam temperature control the controller's gains in a cascade control loop has to be tuned efficiently. The mathematical model of the superheater is derived by sets of nonlinear partial differential equations. The tuning methods taken for study here are designed for delay plus first order transfer function model. Hence from the dynamical model of the superheater, a FOPTD model is derived using frequency response method. Then by using Chien-Hrones-Reswick Tuning Algorithm and Gain-Phase Assignment Algorithm optimum controller gains has been found out based on the least value of integral time weighted absolute error.

The chemical kinetics of the reactions of lithium with steam-air mixtures

International Nuclear Information System (INIS)

Barnett, D.S.; Kazimi, M.S.

1989-04-01

This work involved the experimental and analytical determination of the consequences of lithium fires in the presence of steam. Experiments were performed to characterize the chemical reactions of lithium with steam-nitrogen and steam-air mixtures. Models were introduced in the LITFIRE code to describe lithium fires in the presence of steam inside the containment building and plasma chamber of a hypothetical fusion reactor. The code was also equipped with the capability to determine the effects of decay heat and lithium fire on the temperature response of the reactor first wall in the event of a coolant disturbance. Forty-two kinetics experiments were performed in which a stream of steam-nitrogen or steam-air was passed over and reacted with approximately three grams of lithium heated to a predetermined temperature. The lithium reaction rates with the constituent gases were measured and characterized for a wide range of lithium temperatures and gas compositions. Experiments were performed with steam molar concentrations of 5, 15 and 30% and lithium temperatures ranging from 400 to 1100 degree C, inclusive. The LITFIRE code was modified to enable it to model the interactions of lithium with steam-air atmospheres. Results of the reaction kinetics experiments were used in the reaction model, and the heat transfer model was expanded to allow it to handle condensible atmospheres. Three groups of accidents were investigated: a spill on the containment building floor, a spill inside the reactor plasma chamber, and a spill inside the plasma chamber with steam injection to the containment building simulating a steam line break. The results were compared to dry air cases under the same conditions. 23 refs., 66 figs., 18 tabs

Thermohydraulic verification during THTR steam generator commissioning

International Nuclear Information System (INIS)

Henry, C.; Elter, C.

1988-01-01

In one of the six THTR 300 steam generators thermocouples are installed inside the heat transfer tube bundles for measuring the gas and steam temperatures. Fluid temperature distribution measurements along and across the helix bundle have been recorded in its first months of operation over a load range of 40% up to 100% for steady state and transient conditions. Using these measurements as well as the rest of the operating instrumentation. the computer programs for the design of heat exchanger heat transfer areas are verified. The temperature measurements for steady state conditions are compared with predictions obtained in the design stage. In these codes. the heat transferred from the outside helium gas to the water/steam inside the tubes is determined in discrete steps along the heating surface by one- and two-phase heat transfer correlations. The degree of conformity between prediction and measurement is discussed and compared with more recent correlations. (author)

Steam generator tube rupture effects on a LOCA

International Nuclear Information System (INIS)

LaChance, J.L.

1979-01-01

A problem currently experienced in commercial operating pressurized water reactors (PWR) in the United States is the degradation of steam generator tubes. Safety questions have arisen concerning the effect of these degraded tubes rupturing during a postulated loss-of-coolant accident (LOCA). To determine the effect of a small number of tube ruptures on the behavior of a large PWR during a postulated LOCA, a series of computer simulations was performed. The primary concern of the study was to determine whether a small number (10 or less of steam generator tubes rupturing at the beginning surface temperatures. Additional reflood analyses were performed to determine the system behavior when from 10 to 60 tubes rupture at the beginning of core reflood. The FLOOD4 code was selected as being the most applicable code for use in this study after an extensive analysis of the capabilities of existing codes to perform simulations of a LOCA with concurrent steam generator tube ruptures. The results of the study indicate that the rupturing of 10 or less steam generator tubes in any of the steam generators during a 200% cold leg break will not result in a significant increase in the peak cladding temperature. However, because of the vaporization of the steam generator secondary water in the primary side of the steam generator, a significant increase in the core pressure occurs which retards the reflooding process

Effect of Dynamic Reheating Controlled by the Weaving Width on the Microstructure of GTA Bead-On-Pipe Weld Metal of 25% Cr Super Duplex Stainless Steel

Directory of Open Access Journals (Sweden)

Hee-Joon Sung

2018-05-01

Full Text Available Gas tungsten arc welding (GTAW with three different heat inputs controlled by the weaving width was performed to understand their effects on the microstructural changes during bead-on-pipe welding of super duplex stainless steel. The microstructure of the weld metals was categorized into three different types of zones: non-reheated, reheated type, and reheating-free zone. Even though single-pass welding with different weaving widths was employed, a reheated microstructure was detected, which has been previously observed with multiple pass welding. This phenomenon was called “dynamic reheating”, because it was produced by the weaving operation during welding regardless of the weaving width. The categorized area fraction varied with the weaving width change. Electron backscatter diffraction (EBSD results at the edge (the area near the fusion line of the low-heat-input condition indicated a higher austenite volume fraction and a lower Cr2N fraction than that of the medium heat input condition. Thus, it described an inverse relationship, because higher heat input provided a lower austenite fraction. In addition, it was observed clearly that the austenite fraction at the medium heat input condition was dramatically increased by reheating, while the Cr2N fraction was reduced. Regardless of the weaving width, reheating contributed to the increase of the austenite fraction, further reducing the Cr2N quantity. The edge areas in the map showed an inverse relationship in the reheated area fraction between low heat input and medium heat input. For this reason, the austenite fraction on the weld metal was determined not only by the heat input, but also by the amount of reheating.

Future development of large steam turbines

International Nuclear Information System (INIS)

Chevance, A.

1975-01-01

An attempt is made to forecast the future of the large steam turbines till 1985. Three parameters affect the development of large turbines: 1) unit output; and a 2000 to 2500MW output may be scheduled; 2) steam quality: and two steam qualities may be considered: medium pressure saturated or slightly overheated steam (light water, heavy water); light enthalpie drop, high pressure steam, high temperature; high enthalpic drop; and 3) the quality of cooling supply. The largest range to be considered might be: open system cooling for sea-sites; humid tower cooling and dry tower cooling. Bi-fluid cooling cycles should be also mentioned. From the study of these influencing factors, it appears that the constructor, for an output of about 2500MW should have at his disposal the followings: two construction technologies for inlet parts and for high and intermediate pressure parts corresponding to both steam qualities; exhaust sections suitable for the different qualities of cooling supply. The two construction technologies with the two steam qualities already exist and involve no major developments. But, the exhaust section sets the question of rotational speed [fr

Predicting steam generator crevice chemistry

International Nuclear Information System (INIS)

Burton, G.; Strati, G.

2006-01-01

'Full text:' Corrosion of steam cycle components produces insoluble material, mostly iron oxides, that are transported to the steam generator (SG) via the feedwater and deposited on internal surfaces such as the tubes, tube support plates and the tubesheet. The build up of these corrosion products over time can lead to regions of restricted flow with water chemistry that may be significantly different, and potentially more corrosive to SG tube material, than the bulk steam generator water chemistry. The aim of the present work is to predict SG crevice chemistry using experimentation and modelling as part of AECL's overall strategy for steam generator life management. Hideout-return experiments are performed under CANDU steam generator conditions to assess the accumulation of impurities in hideout, and return from, model crevices. The results are used to validate the ChemSolv model that predicts steam generator crevice impurity concentrations, and high temperature pH, based on process parameters (e.g., heat flux, primary side temperature) and blowdown water chemistry. The model has been incorporated into ChemAND, AECL's system health monitoring software for chemistry monitoring, analysis and diagnostics that has been installed at two domestic and one international CANDU station. ChemAND provides the station chemists with the only method to predict SG crevice chemistry. In one recent application, the software has been used to evaluate the crevice chemistry based on the elevated, but balanced, SG bulk water impurity concentrations present during reactor startup, in order to reduce hold times. The present paper will describe recent hideout-return experiments that are used for the validation of the ChemSolv model, station experience using the software, and improvements to predict the crevice electrochemical potential that will permit station staff to ensure that the SG tubes are in the 'safe operating zone' predicted by Lu (AECL). (author)

Hydrogen production from biomass tar by catalytic steam reforming

International Nuclear Information System (INIS)

Yoon, Sang Jun; Choi, Young-Chan; Lee, Jae-Goo

2010-01-01

The catalytic steam reforming of model biomass tar, toluene being a major component, was performed at various conditions of temperature, steam injection rate, catalyst size, and space time. Two kinds of nickel-based commercial catalyst, the Katalco 46-3Q and the Katalco 46-6Q, were evaluated and compared with dolomite catalyst. Production of hydrogen generally increased with reaction temperature, steam injection rate and space time and decreased with catalyst size. In particular, zirconia-promoted nickel-based catalyst, Katalco 46-6Q, showed a higher tar conversion efficiency and shows 100% conversion even relatively lower temperature conditions of 600 deg. C. Apparent activation energy was estimated to 94 and 57 kJ/mol for dolomite and nickel-based catalyst respectively.

Design and Activation of a LOX/GH Chemical Steam Generator

Science.gov (United States)

Saunders, G. P.; Mulkey, C. A.; Taylor, S. A.

2009-01-01

The purpose of this paper is to give a detailed description of the design and activation of the LOX/GH fueled chemical steam generator installed in Cell 2 of the E3 test facility at Stennis Space Center, MS (SSC). The steam generator uses a liquid oxygen oxidizer with gaseous hydrogen fuel. The combustion products are then quenched with water to create steam at pressures from 150 to 450 psig at temperatures from 350 to 750 deg F (from saturation to piping temperature limits).

Corrosion Product Measurements to ensure integrity of the Steam Generators in Beznau NPP

International Nuclear Information System (INIS)

Mailand, Irene; Franz, Patrick; Venz, Hartmut

2012-09-01

The Nuclear Power Plant Beznau comprises two identical 380 MWe PWR units with two loops each, commissioned in 1969 and 1971. Westinghouse was responsible for the primary part of the plant and BBC/ABB for the secondary circuit. The original materials used in the secondary systems were made of several copper-based alloys, such as for the Condensers, the Low Pressure Pre-heaters and the Moisture Separator Re-heater. The original Steam Generator Tubes were made of Inconel 600 MA. Regarding its age, the NPP Beznau has to be qualified as an old plant. However, in fact particularly in the last 20 years the plant has undergone an extensive modernisation programme in which about 1.5 billion Swiss Francs have been invested. Important measures were the replacements of the Steam Generators with tubes comprising Inconel 690 TT which was realized at unit 1 in 1993 and at unit 2 in 1999. Copper was completely banished from the secondary system and replaced by stainless and chromium steel. The Condensers were fitted with titanium tubes. The secondary water chemistry had to be changed by these replacements and moved step by step from Low-AVT with a pH of about 9.3 to High-AVT with a pH of 9.8 to 9.9, currently. To ensure the integrity of the new Steam Generators as well as of the whole Secondary System a corrosion product programme was introduced at the end of the Nineties. Several investigations which are performed periodically are represented by analyses of corrosion products, measurements of sludge mass and composition in the Steam Generators, Hide-Out-Return- and mass balance measurements of corrosion products in the whole circuit. Objectives of these investigations are assessments of the efficiency of the water chemistry and trend considerations regarding to the transport of corrosion products and pollutants into the Steam Generator, as well as of the potential danger of deposits and stored or absorbed pollutants. The main target of all measures is to avoid any chemical

Deactivation Studies of Rh/Ce0.8Zr0.2O2 Catalysts in Low Temperature Ethanol Steam Reforming

Energy Technology Data Exchange (ETDEWEB)

Platon, Alex; Roh, Hyun-Seog; King, David L.; Wang, Yong

2007-10-30

Rapid deactivation of Rh/Ce0.8Zr0.2O2 catalysts in low temperature ethanol steam reforming was studied. A significant build-up of carbonaceous intermediate, instead of carbon deposit, was observed at a lower reaction temperature which was attributed to the rapid catalyst deactivation. Co-feed experiments indicated that acetone and ethylene caused more severe catalyst deactivation than other oxygenates such as acidic acid and acetaldehyde.

Interpretation of biomass gasification yields regarding temperature intervals under nitrogen-steam atmosphere

Energy Technology Data Exchange (ETDEWEB)

Haykiri-Acma, H.; Yaman, S. [Istanbul Technical University, Chemical and Metallurgical Engineering Faculty, Chemical Engineering Department, 34469 Maslak, Istanbul (Turkey)

2007-04-15

Gasification of some agricultural waste biomass samples (sunflower shell, pine cone, cotton refuse, and olive refuse) and colza seed was performed using a thermogravimetric analyzer at temperatures up to 1273 K with a constant heating rate of 20 K/min under a dynamic nitrogen-steam atmosphere. Derivative thermogravimetric analysis profiles of the samples were derived from the non-isothermal thermogravimetric analysis data. Gasification yields of the biomass samples at temperature intervals of 473-553 K, 553-653 K, 653-773 K, 773-973 K, and 973-1173 K were investigated considering the successive stages of ''evolution of carbon oxides'', ''start of hydrocarbon evolution'', ''evolution of hydrocarbons'', ''dissociation'', and ''evolution of hydrogen'', respectively. Although, there were some interactions between these stages, some evident relations were observed between the gasification yields in a given stage and the chemical properties of the parent biomass materials. (author)

Research on axial total pressure distributions of sonic steam jet in subcooled water

International Nuclear Information System (INIS)

Wu Xinzhuang; Li Wenjun; Yan Junjie

2012-01-01

The axial total pressure distributions of sonic steam jet in subcooled water were experimentally investigated for three different nozzle diameters (6.0 mm, 8.0 mm and 10.0 mm). The inlet steam pressure, and pool subcooling subcooled water temperature were in the range of 0.2-0.6 MPa and 420-860 ℃, respectively. The effect of steam pressure, subcooling water temperature and nozzle size on the axial pressure distributions were obtained, and also the characteristics of the maximum pressure and its position were studied. The results indicated that the characteristics of the maximum pressure were influenced by the nozzle size for low steam pressure, but the influence could be ignored for high steam pressure. Moreover, a correlation was given to correlate the position of the maximum pressure based on steam pressure and subcooling water temperature, and the discrepancies of predictions and experiments are within ±15%. (authors)

High Temperature Air/Steam Gasification of Biomass Wastes - Stage 1. Final report

Energy Technology Data Exchange (ETDEWEB)

Blasiak, Wlodzimierz; Szewczyk, Dariusz; Lucas, Carlos; Rafidi, Nabil; Abeyweera Ruchira; Jansson, Anna; Bjoerkman, Eva [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Science and Engineering

2003-05-01

In Jan 2002 the Division of Energy and Furnace Technology started the project High Temperature Air an Steam Gasification (HTAG) of biomass wastes, following the approval made by Swedish Energy Agency. The research proved successful; with the fixed bed updraft gasifier coupled to the highly regenerative preheater equipment able to produce a fuel gas not only from wood pellets but also from wood chips, bark and charcoal with considerably reduced amount of tar. This report provides information on solid biomass conversion into fuel gas as a result of air and steam gasification process performed in a fixed bed updraft gasifier. The first chapter of the report presents the overall objectives and the specific objectives of the work. Chapter 2 summarizes state-of-the-art on the gasification field stating some technical differences between low and high temperature gasification processes. Description and schemes of the experimental test rig are provided in Chapter 3. The equipment used to perform measurements of different sort and that installed in the course of the work is described in Chapter 4. Chapter 5 describes the methodology of experiments conducted whose results were processed and evaluated with help of the scheme of equations presented in Chapter 6, called raw data evaluation. Results of relevant experiments are presented and discussed in Chapter 7. A summary discussion of the tar analysis is presented in Chapter 8. Chapter 9 summarizes the findings of the research work conducted and identifies future efforts to ensure the development of next stage. Final chapter provides a summary of conclusions and recommendations of the work. References are provided at the end of the report. Aimed to assist the understanding of the work done, tables and graphs of experiments conducted, irrespective to their quality, are presented in appendices.

Steam-treatment-based soil remediation promotes heat-tolerant, potentially pathogenic microbiota

DEFF Research Database (Denmark)

Altenburger, Andreas; Bender, Mikkel; Ekelund, Flemming

2014-01-01

We investigated microbiota in surface and subsurface soil from a site, above steam-treated deep sub-soil originally contaminated with chlorinated solvents. During the steam treatment, the surface soil reached temperatures c. 30°C higher than the temperature in untreated soil; whereas the subsurfa...

Environmentally assisted fatigue evaluation model of alloy 690 steam generator tube in high temperature water

International Nuclear Information System (INIS)

Tan Jibo; Wu Xinqiang; Han Enhou; Wang Xiang; Liu Xiaoqiang; Xu Xuelian

2015-01-01

Nickel-based alloy 690 has been widely used as steam generator tube in light water reactor (LWR) nuclear power plants, which may suffer from corrosion fatigue during long-term service. Many researches and operating experience indicated that the effect of LWR environment could significantly reduce the fatigue life of structural materials. However. such an environmental degradation effect was not fully addressed in the current ASME code design fatigue curves. Therefore, the Regulatory Guide 1.207 issued by US NRC required a new NPP have to incorporate the environment effects into fatigue analyses. In the last few decades, researchers in USA and Japan systematically investigated the corrosion fatigue behavior of nuclear-grade structural materials in LWR environment. Then, ANL model and JSME model were proposed, which incorporated environmental effects, including temperature, dissolved oxygen (DO) and strain rate for the nickel-based alloys. Due to lack of experiment data on domestic materials, there is no related environmental fatigue design model in China. In the present work, based on the corrosion fatigue tests of a kind of boat-shaped specimen in borated and lithiated high temperature water, the corrosion fatigue behavior and environmentally assisted cracking mechanism of domestic Alloy 690 steam generator tube have been investigate. An IMR model for the nickel-based alloy was proposed. The environmental fatigue life correction factor (F en ) was established, which addressed the environmental factors, including temperature, strain rate and dissolved oxygen. The method to evaluate environmental fatigue damage of structural materials in NPPs was proposed. (authors)

On possibility of application of the parallel-mixed type coolant flow scheme to NPP steam generators linked with superheaters

International Nuclear Information System (INIS)

Malkis, V.A.; Lokshin, V.A.

1983-01-01

Optimum distribution of the coolant straight-through flow between the superheater, evaporator and economizer is determined and the parallel-mixed type flow scheme is compared with other schemes. The calculations are performed for the 250 MW(e) steam generator for the WWER-1000 reactor unit the inlet and outlet primary coolant temperature of which is 324 and 290 deg C, respectively, while the feed water and saturation temperatures are 220 and 278.5 deg C, respectively. The rated superheating temperature is 300 deg C. The comparison of different schemes has been performed according to the average temperature head value at the steam-generator under the condition of equality as well as essential difference in the heat transfer coefficients in certain steam-generator sections. The calculations have shown that the use of parallel-mixed type flow permits to essentially increase the temperature head of the steam generator. At a constant heat transfer coefficient in all steam generator sections the highest temperature head is reached. At relative flow rates in the steam generator, economizer and evaporator equal to 6, 8 and 86%, respectively. The superheated steam generator temperature head in this case by 12% exceeds the temperature head of the WWER-1000 reactor unit wet steam generator. In case of heat transfer coefficient reduction in the superheater by a factor of three, the choice of the primary coolant, optimum distribution permits to maintain the steam generator temperature head at the level of the WWER-1000 reactor unit wet-steam steam generator. The use of the parallel-mixed type flow scheme permits to design a steam generator of slightly superheated steam for the parameters of the WWER-1000 unit

Thermoelastic steam turbine rotor control based on neural network

Science.gov (United States)

Rzadkowski, Romuald; Dominiczak, Krzysztof; Radulski, Wojciech; Szczepanik, R.

2015-12-01

Considered here are Nonlinear Auto-Regressive neural networks with eXogenous inputs (NARX) as a mathematical model of a steam turbine rotor for controlling steam turbine stress on-line. In order to obtain neural networks that locate critical stress and temperature points in the steam turbine during transient states, an FE rotor model was built. This model was used to train the neural networks on the basis of steam turbine transient operating data. The training included nonlinearity related to steam turbine expansion, heat exchange and rotor material properties during transients. Simultaneous neural networks are algorithms which can be implemented on PLC controllers. This allows for the application neural networks to control steam turbine stress in industrial power plants.

Experiment on the Influence Factors of Steam Distillation Rate of Crude Oil in Porous Media

Directory of Open Access Journals (Sweden)

Tian Guoqing

2017-01-01

Full Text Available To explore the influence of complexity of reservoir properties in porous media and the diversity of operating conditions on the steam distillation rate of crude oil in the process of heavy oil exploitation with steam injection, steam distillation simulation devices are used to study steam distillation rate of crude oil in porous media. Then steam distillation ratio is obtained under the condition of different core permeability, oil saturation, steam temperatures, system pressure, steam injection rates and steam distillation rates with different viscosities of crude oil. The results show that the steam distillation rate of crude oil in porous media depends mainly on the nature of the crude oil itself, for temperature and pressure are the key factors compared with the pore structure, the initial oil saturation and steam injection rate. The experimental results help estimate the amount of crude oil and the required steam in the reservoir in the steam drive process, aiming to facilitate the optimization design and operation of steam drive.

Two-dimensional modeling of water spray cooling in superheated steam

Directory of Open Access Journals (Sweden)

Ebrahimian Vahid

2008-01-01

Full Text Available Spray cooling of the superheated steam occurs with the interaction of many complex physical processes, such as initial droplet formation, collision, coalescence, secondary break up, evaporation, turbulence generation, and modulation, as well as turbulent mixing, heat, mass and momentum transfer in a highly non-uniform two-phase environment. While it is extremely difficult to systematically study particular effects in this complex interaction in a well defined physical experiment, the interaction is well suited for numerical studies based on advanced detailed models of all the processes involved. This paper presents results of such a numerical experiment. Cooling of the superheated steam can be applied in order to decrease the temperature of superheated steam in power plants. By spraying the cooling water into the superheated steam, the temperature of the superheated steam can be controlled. In this work, water spray cooling was modeled to investigate the influences of the droplet size, injected velocity, the pressure and velocity of the superheated steam on the evaporation of the cooling water. The results show that by increasing the diameter of the droplets, the pressure and velocity of the superheated steam, the amount of evaporation of cooling water increases. .

Three-dimensional modeling of nuclear steam generator

International Nuclear Information System (INIS)

Bogdan, Z.; Afgan, N.

1985-01-01

In this paper mathematical model for steady-state simulation of thermodynamic and hydraulic behaviour of U-tube nuclear steam generator is described. The model predicts three-dimensional distribution of temperatures, pressures, steam qualities and velocities in the steam generator secondary loop. In this analysis homogeneous two phase flow model is utilized. Foe purpose of the computer implementation of the mathematical model, a special flow distribution code NUGEN was developed. Calculations are performed with the input data and geometrical characteristics related to the D-4 (westinghouse) model of U-tube nuclear steam generator built in Krsko, operating under 100% load conditions. Results are shown in diagrams giving spatial distribution of pertinent variables in the secondary loop. (author)

French steam generator design developments

International Nuclear Information System (INIS)

Ginier, R.; Campan, J.L.; Pontier, M.; Leridon, A.; Remond, A.; Castello, G.; Holcblat, A.; Paurobally, H.

1986-01-01

From the outset of the French nuclear power program, a significant R and D effort has been invested in improvement of the design and operation of Pressurized Water Reactors including a special committment to improving steam generators. The steam generator enhancement program has spawned a wide variety of specific R and D resources, e.g., low temperature hydraulic models for investigation of areas with single-phase flow, and freon-filled models for simulation of areas of steam generators experiencing two-phase flow (tube bundles and moisture separators). For the moisture separators, a large scale research program using freon-filled models and highly sophisticated instrumentation was used. Tests at reactor sites during startup of both 900 MWe and 1300 MWe have been used to validate the assumptions made on the basis of loop tests. These tests also demonstrated the validity of using freon to simulate two-phase flow conditions. The wealth of knowledge accumulated by the steam generator R and D program has been used to develop a new design of steam generators for the N4 plants. The current R and D effort is aimed at qualifying the N4 steam generator model and developing more comprehensive models. One prong of the R and D effort is the Megeve program. Megeve is a 25 MW steam generator which simulates operating conditions of the N4 model. The other prong is Clotaire, a freon-filled steam generator model which will be used to qualify thermal/hydraulic design codes used for multidimensional calculations for design of tube bundles

Corrosion of graphitic high temperature reactor materials in steam/helium mixtures at total pessures of 3-55 bar and temperatures of 900-1150 C (1173-1423K)

International Nuclear Information System (INIS)

Hinssen, H.K.; Loenissen, K.J.; Katscher, W.; Moormann, R.

1993-03-01

In course of accident examination for (HTR), experiments on the corrosion behavior of graphitic reactor materials in steam have been performed a total pressures of 3-55bar and temperatures of 900-1150 C (1173-1423K); these experiments and their evaluation are documented here. Reactor materials examined are the structure graphite V483T2 and the fuel element matrices A3-27 and A3-3. In all experiments, the steam partial pressure was 474mbar (inert gas helium). The dependence of reaction rates and density profiles on burn-off, total pressure and temperature has been examined. Experimental reaction rates depending on burn-off are fitted by theoretical curves, a procedure, which allows rate comparison for a well defined burn-off. Comparing rates as a function of total pressure, V483T2 shows a linear dependence on 1√p total , whereas for matrix materials a pressure independent rate was found for p total 4mm for A3-3. (orig.) [de

Steam generators secondary side chemical cleaning at Point Lepreau using the Siemen's high temperature process

International Nuclear Information System (INIS)

Verma, K.; MacNeil, C.; Odar, S.

1996-01-01

The secondary sides of all four steam generators at the Point Lepreau Nuclear Generating Stations were cleaned during the 1995 annual outage run-down using the Siemens high temperature chemical cleaning process. Traditionally all secondary side chemical cleaning exercises in CANDU as well as the other nuclear power stations in North America have been conducted using a process developed in conjunction with the Electric Power Research Institute (EPRI). The Siemens high temperature process was applied for the first time in North America at the Point Lepreau Nuclear Generating Station (PLGS). The paper discusses experiences related to the pre and post award chemical cleaning activities, chemical cleaning application, post cleaning inspection results and waste handling activities. (author)

Cast Alloys for Advanced Ultra Supercritical Steam Turbines

Energy Technology Data Exchange (ETDEWEB)

G. R. Holcomb, P. Wang, P. D. Jablonski, and J. A. Hawk,

2010-05-01

The proposed steam inlet temperature in the Advanced Ultra Supercritical (A-USC) steam turbine is high enough (760 °C) that traditional turbine casing and valve body materials such as ferritic/martensitic steels will not suffice due to temperature limitations of this class of materials. Cast versions of several traditionally wrought Ni-based superalloys were evaluated for use as casing or valve components for the next generation of industrial steam turbines. The full size castings are substantial: 2-5,000 kg each half and on the order of 100 cm thick. Experimental castings were quite a bit smaller, but section size was retained and cooling rate controlled to produce equivalent microstructures. A multi-step homogenization heat treatment was developed to better deploy the alloy constituents. The most successful of these cast alloys in terms of creep strength (Haynes 263, Haynes 282, and Nimonic 105) were subsequently evaluated by characterizing their microstructure as well as their steam oxidation resistance (at 760 and 800 °C).

Steam chugging in pressure suppression containment

International Nuclear Information System (INIS)

Lee, C.K.B.; Chan, C.K.

1978-01-01

The condensation of steam flow in subcooled water was studied by injecting a quasi-steady stream of saturated steam into a pool water at different temperature. From the movies, it was observed that chugging occurred at a frequency on the order of 1 to 2 times a second. In between each chug over a period of approximately half a second, a few bubbles formed and collapsed at the exit of the downcomer. At a mass flow rate of approximately 5.02 Kg/m 2 sec., the chugging process is found to be strongly affected by the bubble formation. At pool temperatures below 50 0 C, the chugging process is dominated by internal chugging which is characterized by high water slug exit velocity, detached steam bubble and lhigh chugging level. Above 50 0 C, the external chugging mode is dominant. The external chugging mode is characterized by pancake bubble shape, low water slug exit velocity, and low chugging level. (author)

Methane Steam Reforming Kinetics for a Rhodium-Based Catalyst

DEFF Research Database (Denmark)

Jakobsen, Jon Geest; Jakobsen, M.; Chorkendorff, Ib

2010-01-01

Methane steam reforming is the key reaction to produce synthesis gas and hydrogen at the industrial scale. Here the kinetics of methane steam reforming over a rhodium-based catalyst is investigated in the temperature range 500-800 A degrees C and as a function of CH4, H2O and H-2 partial pressures....... The methane steam reforming reaction cannot be modeled without taking CO and H coverages into account. This is especially important at low temperatures and higher partial pressures of CO and H-2. For methane CO2 reforming experiments, it is also necessary to consider the repulsive interaction of CO...

Steam 80 steam generator instrumentation

International Nuclear Information System (INIS)

Carson, W.H.; Harris, H.H.

1980-01-01

This paper describes two special instrumentation packages in an integral economizer (preheater) steam generator of one of the first System 80 plants scheduled to go into commercial operation. The purpose of the instrumentation is to obtain accurate operating information from regions of the secondary side of the steam generator inaccessible to normal plant instrumentation. In addition to verification of the System 80 steam generator design predictions, the data obtained will assist in verification of steam generator thermal/hydraulic computer codes developed for generic use in the industry

The influence of heating rate on reheat-cracking in a commercial 2 1/4Cr1Mo steel

International Nuclear Information System (INIS)

Hippsley, C.A.

1983-03-01

The effects of elevated heating rate on stress-relief cracking in a commercial 2 1/4 Cr1Mo steel have been investigated. A SEN bend-specimen stress-relaxation test was used to assess reheat cracking susceptibility and fracture mechanisms for an initial post-weld heating rate of 1000 Kh - 1 . Two factors controlling the influence of heating rate on the final severity of cracking were identified, i.e. the rate of stress-relaxation with respect to temperature, and the time available for crack-growth. The factors were found to counteract each other, but in the case of commercial 2 1/4 Cr1Mo steel, the crack-growth factor outweighed the relaxation factor, resulting in a reduction in the propensity to stress-relief cracking at the elevated heating rate. However, by reference to the results of a separate investigation concerning A508/2 MnMoNiCr steel it was demonstrated that the balance between these two factors may be reversed in other alloy systems, with the consequence that reheat cracking is exacerbated by increasing the initial heating rate. A computer model was addressed to the stress-relaxation test conditions using data from the commercial 2 1/4 Cr1Mo steel. The model predictions exhibited reasonable agreement with experimental test results for both 100 Kh - 1 and 1000 Kh - 1 heating rates. (author)

Analysis on Operating Parameter Design to Steam Methane Reforming in Heat Application RDE

Science.gov (United States)

Dibyo, Sukmanto; Sunaryo, Geni Rina; Bakhri, Syaiful; Zuhair; Irianto, Ign. Djoko

2018-02-01

The high temperature reactor has been developed with various power capacities and can produce electricity and heat application. One of heat application is used for hydrogen production. Most hydrogen production occurs by steam reforming that operated at high temperature. This study aims to analyze the feasibility of heat application design of RDE reactor in the steam methane reforming for hydrogen production using the ChemCAD software. The outlet temperature of cogeneration heat exchanger is analyzed to be applied as a feed of steam reformer. Furthermore, the additional heater and calculating amount of fuel usage are described. Results show that at a low mass flow rate of feed, its can produce a temperature up to 480°C. To achieve the temperature of steam methane reforming of 850°C the additional fired heater was required. By the fired heater, an amount of fuel usage is required depending on the Reformer feed temperature produced from the heat exchanger of the cogeneration system.

Heat transfer in the over-crisis region in a steam-generating channel with steam-droplet flow

International Nuclear Information System (INIS)

Nigmatulin, B.I.; Kukharenko, V.N.

1991-01-01

Statement and results of numerical solution of the problem on heat transfer in the over-crisis region under stationary and nonstationary conditions are studied. Two-temperature model, accounting for influence of phase slipping on heat exchange between steam and droplets and direct heat interaction with heated surface is used for describing steam-droplet flow. Comparison is made of calculational results and experimental data published in the literature on heated surface temperature within broad range of parameters: pressure - p=0.3-18.5 MPa; specific mass flow rate of the mixture - G=30-5000 kg/m 2 xs; specific heat flows - q=0.02-3 MW/m 2 and tube diameter - D=4-20 mm

Cascade control of superheated steam temperature with neuro-PID controller.

Science.gov (United States)

Zhang, Jianhua; Zhang, Fenfang; Ren, Mifeng; Hou, Guolian; Fang, Fang

2012-11-01

In this paper, an improved cascade control methodology for superheated processes is developed, in which the primary PID controller is implemented by neural networks trained by minimizing error entropy criterion. The entropy of the tracking error can be estimated recursively by utilizing receding horizon window technique. The measurable disturbances in superheated processes are input to the neuro-PID controller besides the sequences of tracking error in outer loop control system, hence, feedback control is combined with feedforward control in the proposed neuro-PID controller. The convergent condition of the neural networks is analyzed. The implementation procedures of the proposed cascade control approach are summarized. Compared with the neuro-PID controller using minimizing squared error criterion, the proposed neuro-PID controller using minimizing error entropy criterion may decrease fluctuations of the superheated steam temperature. A simulation example shows the advantages of the proposed method. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Performance of iron–chromium–aluminum alloy surface coatings on Zircaloy 2 under high-temperature steam and normal BWR operating conditions

Energy Technology Data Exchange (ETDEWEB)

Zhong, Weicheng; Mouche, Peter A.; Han, Xiaochun [University of Illinois, Department of Nuclear, Radiological, and Plasma Engineering, Urbana, IL 61801 (United States); Heuser, Brent J., E-mail: bheuser@illinois.edu [University of Illinois, Department of Nuclear, Radiological, and Plasma Engineering, Urbana, IL 61801 (United States); Mandapaka, Kiran K.; Was, Gary S. [University of Michigan, Department of Nuclear Engineering and Radiological Sciences, Ann Arbor, MI 48109 (United States)

2016-03-15

Iron-chromium-aluminum (FeCrAl) coatings deposited on Zircaloy 2 (Zy2) and yttria-stabilized zirconia (YSZ) by magnetron sputtering have been tested with respect to oxidation weight gain in high-temperature steam. In addition, autoclave testing of FeCrAl-coated Zy2 coupons under pressure-temperature-dissolved oxygen coolant conditions representative of a boiling water reactor (BWR) environment has been performed. Four different FeCrAl compositions have been tested in 700 °C steam; compositions that promote alumina formation inhibited oxidation of the underlying Zy2. Parabolic growth kinetics of alumina on FeCrAl-coated Zy2 is quantified via elemental depth profiling. Autoclave testing under normal BWR operating conditions (288 °C, 9.5 MPa with normal water chemistry) up to 20 days demonstrates observable weight gain over uncoated Zy2 simultaneously exposed to the same environment. However, no FeCrAl film degradation was observed. The 900 °C eutectic in binary Fe–Zr is addressed with the FeCrAl-YSZ system. - Graphical abstract: Weight gain normalized to total sample surface area versus time during 700 °C steam exposure for FeCrAl samples with different composition (A) and Fe/Cr/Al:62/4/34 (B). In both cases, the responses of uncoated Zry2 (Zry2-13A and Zry2-19A) are shown for comparison. This uncoated Zry2 response shows the expected pre-transition quasi-cubic kinetic behavior and eventual breakaway (linear) kinetics. Highlights: • FeCrAl coatings deposited on Zy2 have been tested with respect to oxidation in high-temperature steam. • FeCrAl compositions promoting alumina formation inhibited oxidation of Zy2 and delay weight gain. • Autoclave testing to 20 days of coated Zy2 in a simulated BWR environment demonstrates minimal weight gain and no film degradation. • The 900 °C eutectic in binary Fe-Zr is addressed with the FeCrAl-YSZ system.

Prospects for Martensitic 12 % Cr Steels for Advanced Steam Power Plants

DEFF Research Database (Denmark)

Hald, John

2016-01-01

and FB2 are now used in power plants up to 600–620 °C steam temperature. For higher steam temperatures up to 650 °C steels with 11–12 % Cr are needed for better resistance against steam oxidation. However, fine V and Nb based nitrides may transform to coarse Z-phase [Cr(V,Nb)N] nitrides in steels...

Baryogenesis, dark matter and the maximal temperature of the early universe

Energy Technology Data Exchange (ETDEWEB)

Buchmueller, Wilfried

2012-12-15

Mechanisms for the generation of the matter-antimatter asymmetry and dark matter strongly depend on the reheating temperature T{sub R}, the maximal temperature reached in the early universe. Forthcoming results from the LHC, low energy experiments, astrophysical observations and the Planck satellite will significantly constrain baryogenesis and the nature of dark matter, and thereby provide valuable information about the very early hot universe. At present, a wide range of reheating temperatures is still consistent with observations. We illustrate possible origins of matter and dark matter with four examples: moduli decay, electroweak baryogenesis, leptogenesis in the {nu}MSM and thermal leptogenesis. Finally, we discuss the connection between baryogenesis, dark matter and inflation in the context of supersymmetric spontaneous B-L breaking.

Baryogenesis, dark matter and the maximal temperature of the early universe

International Nuclear Information System (INIS)

Buchmueller, Wilfried

2012-12-01

Mechanisms for the generation of the matter-antimatter asymmetry and dark matter strongly depend on the reheating temperature T R , the maximal temperature reached in the early universe. Forthcoming results from the LHC, low energy experiments, astrophysical observations and the Planck satellite will significantly constrain baryogenesis and the nature of dark matter, and thereby provide valuable information about the very early hot universe. At present, a wide range of reheating temperatures is still consistent with observations. We illustrate possible origins of matter and dark matter with four examples: moduli decay, electroweak baryogenesis, leptogenesis in the νMSM and thermal leptogenesis. Finally, we discuss the connection between baryogenesis, dark matter and inflation in the context of supersymmetric spontaneous B-L breaking.

Heating characteristics of billet in a walking hearth type reheating furnace

International Nuclear Information System (INIS)

Emadi, Ali; Saboonchi, Ahmad; Taheri, Mahdi; Hassanpour, Saeid

2014-01-01

The heating characteristics of billet in a walking hearth type reheating furnace were studied by developing a mathematical heat transfer model. Radiation calculations were conducted by means of zone method and considering all radiation exchange paths. The weighted-sum-of-gray-gas-model was used for better accuracy of gas radiation prediction. Convective heat flux was calculated by considering suitable value of convective heat transfer coefficient at any location of the furnace. The model was substantiated through its comparison to experimental data. A comparison was drawn to evaluate the effect of constant and variable convective coefficient on convective flux distribution and billet thermal behavior. The effect of furnace wall's emissivity of each zone and whole of the furnace on the billet thermal behavior was investigated. The obtained results revealed that by increasing furnace wall's emissivity for a determined residence time, billet's temperature in primary zones rises but it has no significant effect on its final temperature. However, by increasing wall's emissivity from 0.7 to 0.95, the residence time can be declined by about 5%. Moreover, emissivity increase in non-firing and preheating zones as compared to heating and soaking zones has greater impact on the billet thermal behavior. -- Highlights: • 3D radiation modeling by considering all possible paths of radiation exchange. • Using WSGG model for better prediction of gas radiation. • Using non-constant convection coefficient to consider variation of gas mass flow. • Investigation of effect of convection coefficient on billet temperature behavior. • Investigation of wall emissivity of furnace zones

Development and validation of advanced oxidation protective coatings for super critical steam power plant

Energy Technology Data Exchange (ETDEWEB)

Henderson, M.B.; Scheefer, M. [Alstom Power Ltd., Rugby (United Kingdom); Agueero, A. [Instituto Nacional de Tecnica Aerospacial (INTA) (Spain); Allcock, B. [Monitor Coatings Ltd. (United Kingdom); Norton, B. [Indestructible Paints Ltd. (United Kingdom); Tsipas, D.N. [Aristotle Univ. of Thessaloniki (Greece); Durham, R. [FZ Juelich (Germany); Xiang, Z. [Northumbria Univ. (United Kingdom)

2006-07-01

Increasing the efficiency of coal-fired power plant by increasing steam temperatures and pressures brings benefits in terms of cheaper electricity and reduced emissions, particularly CO{sub 2}. In recent years the development of advanced 9%Cr ferritic steels with improved creep strength has enabled power plant operation at temperatures in excess of 600 C, such that these materials are being exploited to construct a new generation of advanced coalfired plant. However, the move to higher temperatures and pressures creates an extremely hostile oxidising environment. To enable the full potential of the new steels to be achieved, it is vital that protective coatings are developed, validated under high temperature steam and applied to candidate components from the steam path. This paper reviews recent work conducted within the Framework V project ''Coatings for Supercritical Steam Cycles'' (SUPERCOAT) to develop and demonstrate advanced slurry and thermal spray coatings capable of providing steam oxidation protection at temperatures in excess of 620 C and up to 300 bar. The programme of work has demonstrated the feasibility of applying a number of candidate coatings to steam turbine power plant components and has generated long-term steam oxidation rate and failure data that underpin the design and application work packages needed to develop and establish this technology for new and retrofit plant. (orig.)

Reheating-volume measure for random-walk inflation

International Nuclear Information System (INIS)