Prediction of the Inner Temperatures in a Duct Based on Outer Thermocouples Measurements

2013 ◽  
Author(s):  
Stéphane Gervais ◽  
Alexandre Girard
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Element Model ◽  
Fluid Temperature ◽  
Time Saving ◽  
Gradient Computation ◽  
Different Temperatures ◽  
Fatigue Evaluation ◽  
The Cost ◽  
Nelder Mead Algorithm

Nuclear power plants (NPP) include connections of branches conveying fluids at different temperatures. Some thermohydraulics phenomena such as stratification may affect the inner wall of the ducts and lead to fatigue damage. They are then defined in a conservative way for fatigue evaluation. In order to improve the definitions of these phenomena EDF plans to install thermocouples rings on the outer surfaces of some ducts. The aim of this article is to define a methodology to derive thermal loadings from outer measurements. To estimate the temperature of the inner skin duct through measurements on the outer surface of the ducts, we propose to use optimal control (with quadratic cost functions) to compare the outer temperatures calculated with a finite element model and the measurements. Different methods are investigated: first, a method based on Nelder-Mead algorithm [3] and second, an advanced method based on gradient computation. The advantage of the latter is to explicitly compute the gradient and a Hessian approximation of the cost function with respect to the water temperatures, which is time saving for computation-wise. To enhance the robustness of the methodology, additional conditions on the regularity of the fluid temperature field are added.

scholarly journals Method of estimation of annual risk from breaks, fires and explosions on the basis of state graphs in electrolysis plants

2019 ◽  
Vol 11 (4) ◽  
pp. 305-310
Author(s):  
R. Z. Aminov ◽  
E. Yu. Burdenkova ◽  
A. V. Portyankin
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Linear Equations ◽  
The State ◽  
State Graph ◽  
Explosion Hazard ◽  
Equipment Failures ◽  
State Breakdown ◽  
The Cost ◽  
Annual Risk

A method is presented for estimating the possible annual risk that a hydrogen superstructure at a nuclear power plant (NPP) may have in the production of explosive hydrogen. With the observance of safety rules in terms of receiving, storing, transporting and using hydrogen, it is possible to minimize the occurrence of fi re and explosion hazard situations on the hydrogen superstructure. Scheduled repair and overhauls with all diagnostics reduce emergencies and equipment failures in the same way. However, there is a likelihood for the equipment to be found in an abnormal state (breakdown, fi re and explosion) as a result of hydrogen leaks. Depressurization of equipment with leakage of explosive hydrogen in enclosed spaces concurrently with adverse attendant factors may lead to the destruction of the electrolysis plant due to fi re and explosion. With the help of the state graph, the probabilities of a failure of electrolysis equipment because of unplanned breakdowns and possible fi res or explosions indoors due to depressurization of equipment are estimated. To this effect, possible scenarios of breakdowns of the electrolyzer in one and two workshops are considered. In the calculations of the state graph, a system of linear equations was composed for steady-state values only. The calculations have shown that for a configuration involving two electrolysis plants, the possible annual risk would increase. Minimizing the annual risk can be achieved through boosting the capacity of the electrolysis plant still in operation by increasing its productivity in hydrogen and oxygen. The effect will only be achieved if the cost of electricity from nuclear power plants is kept within 0.81 rubles/(kW·h) with a peak electricity tariff at 3.5 rubles/(kW·h).

Analytical Evaluation of Unsteady Thermal Hydraulic Characteristics in Shell and Tube Heat Exchangers

2006 ◽  
Author(s):  
Shiro Takahashi ◽  
Yuichi Narumi ◽  
Kiyoshi Ishihama ◽  
Akihito Yokoyama ◽  
Toyohiko Tsuge ◽  
...  
Keyword(s):  
Heat Exchangers ◽  
Nuclear Power ◽  
Power Plants ◽  
Tube Bundle ◽  
Fluid Temperature ◽  
Detached Eddy Simulation ◽  
Tube Heat Exchanger ◽  
Eddy Simulation ◽  
Safety And Reliability ◽  
Cfd Analyses

Many shell & tube heat exchangers are used in nuclear power plants. Unsteady thermal hydraulic phenomena have been studied in shell & tube heat exchangers to improve their safety and reliability and to extend their lifetime based on experience obtained from long periods of plant operation. We investigated unsteady flow in shell & tube heat exchangers by using computational fluid dynamics (CFD) analyses. The inlet flow on the shell side was separated and flow in several directions. A large part of the flow crossed over the tube bundle, and some parts of the flow took two circuitous roots (up and down) along the inner surface of the shell. Separated circuitous flows collided again where a baffle plate had been cut off. A pair of symmetric vortexes could be seen in that location. Some parts of the circuitous flow moved backwards into the tube bundle due to vortexes. These vortexes were unstable and changed their size and location. A pair of vortexes changed from symmetric to asymmetric. As a result, the direction of flow in the tube bundle near the vortexes changed continuously. Variations in vortexes simulated through CFD analyses could also be seen in tests on the actual size. Fluid temperature fluctuations around tubes were also evaluated through CFD analyses. Unsteady phenomena with changes from symmetric to asymmetric vortexes could be observed in the shell & tube heat exchanger and were simulated through CFD analyses with a detached eddy simulation (DES) turbulence model.

scholarly journals Determination of Transient Fluid Temperature and Thermal Stresses in Pressure Thick-Walled Elements Using a New Design Thermometer

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 222 ◽  
Author(s):  
Magdalena Jaremkiewicz ◽  
Dawid Taler ◽  
Piotr Dzierwa ◽  
Jan Taler
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Critical Pressure ◽  
Thermal Stresses ◽  
Thermal Inertia ◽  
Internal Surface ◽  
Transient Temperature ◽  
Fluid Temperature ◽  
Start Up

In both conventional and nuclear power plants, the high thermal load of thick-walled elements occurs during start-up and shutdown. Therefore, thermal stresses should be determined on-line during plant start-up to avoid shortening the lifetime of critical pressure elements. It is necessary to know the fluid temperature and heat transfer coefficient on the internal surface of the elements, which vary over time to determine transient temperature distribution and thermal stresses in boilers critical pressure elements. For this reason, accurate measurement of transient fluid temperature is very significant, and the correct determination of transient thermal stresses depends to a large extent on it. However, thermometers used in power plants are not able to measure the transient fluid temperature with adequate accuracy due to their massive housing and high thermal inertia. The article aims to present a new technique of measuring transient superheated steam temperature and the results of its application on a real object.

A Study of Nanoparticle-Enhanced Heat Transfer

2010 ◽  
Author(s):  
Lawrence M. Jones ◽  
Timothy Sirk ◽  
Eugene Brown
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Molecular Dynamics ◽  
Heat Flux ◽  
Nuclear Power ◽  
Power Plants ◽  
Md Simulations ◽  
Theoretical Description ◽  
Different Temperatures ◽  
Dynamics Simulations

The study of the heat transfer characteristics of nanofluids, i.e. fluids that are suspensions of nanometer size particles, has gained significant attention in the search for new coolants that can effectively service a variety of needs ranging from the increasing heat transfer demands of ever smaller microelectronic devices to mitigating the effects of loss of coolant accidents in nuclear power plants. Experimental data has shown large increases in thermal conductivity and associated increases in the level of critical heat flux in nuclear reactors; however, in some cases the range of the applicability of the experimental results is uncertain and there is a lack of a theory by which this can be resolved. Complicating the theoretical description of heat transfer in nanofluids is the fact that fluids in the vicinity of the nanoparticles are a complex combination of phase transition, interfacial, and transport phenomena. This paper describes a study in which molecular dynamics simulations were used to enhance the understanding of the effect of nanoparticles on heat transfer. The molecular dynamics (MD) simulations presented here model a Lennard-Jones fluid in a channel where the walls are maintained at different temperatures. The heat flux is calculated for a variety of nanoparticle sizes and concentrations. The results are compared to experimental data in order to provide information that will more confidently bound the data and provide information that will guide the development of more comprehensive theories. We also anticipate that this work could contribute to the design of biosensors where suspended molecules are transported through micro- and nano-channels in the presence of heat transfer.

scholarly journals Catalytic activity of Pd-Ni in the oxidation of hydrogen for the safety of nuclear power plant

2016 ◽  
Vol 18 (1) ◽  
pp. 15-18
Author(s):  
Dariusz Łomot ◽  
Zbigniew Karpiński
Keyword(s):  
Bimetallic Catalysts ◽  
Nuclear Power ◽  
Power Plants ◽  
Hydrogen Oxidation ◽  
Precious Metals ◽  
Oxidation Of Hydrogen ◽  
Different Temperatures ◽  
Flowing System ◽  
Over Time ◽  
Excellent Stability

Abstract Pd-Ni/Al2O3 systems were investigated in the reaction of hydrogen oxidation in terms of their possible application as catalysts used in passive autocatalytic recombiners (PARs) used in nuclear power plants. Testing experiments were carried out in a flowing system at different temperatures and humidity of the reaction mixture. The bimetallic catalysts exhibited higher response to the increase of temperature and higher resistance to inhibit water than the monometallic palladium catalyst. They showed excellent stability during a few tens of hours, similarly, like their monometallic counterpart. Our bimetallic catalysts of hydrogen oxidation can be used as cheaper alternatives to catalysts based on the precious metals in the hydrogen oxidation without loss of their activity over time.

Long Term Fatigue Evaluation in Primary Circuit Components Within Nuclear Power Plants Operated by E.ON

2013 ◽  
Author(s):  
Sven H. Reese ◽  
Dietmar Klucke
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Primary Circuit ◽  
Integrity Assessment ◽  
Comprehensive Information ◽  
Substantial Progress ◽  
Circuit Components ◽  
Numerical Finite Element ◽  
Fatigue Evaluation

Temperature-measuring thermocouples have been applied to various positions on primary circuit piping where most significant thermal loads were expected. Measuring positions were monitored and evaluated, leading to comprehensive information of existing thermal loadings like stratification and thermo shock events. During design of NPP (nuclear power plant) predicted cumulative fatigue usage factors (CUF) were defined based on specified transients. Conservative assumptions are part of this predicted end of life CUF. In comparison to detailed analysis based on real measured values, these predictions based on specified loads are leading to more conservative results in general. Evaluations underline the conservatism of design predictions in general and result in substantial progress in component integrity assessment knowledge. The range of methods to calculate component specific fatigue usage factors goes from conservative approaches based on the evaluation of the stress range of the specific events up to numerical Finite Element simulations. Based on the level of detail the conservatism decreases while the complexity of the model increases. An overview of monitoring measures of passive piping components in terms of thermal fatigue assessment is being applied in NPPs operated by E.ON Kernkraft GmbH. Evaluation methods will be discussed in detail and differences between these methods will be presented.

Systematic Evaluation of Creep-Fatigue Life Prediction Methods for Various Alloys

2009 ◽  
Author(s):  
Yukio Takahashi ◽  
Bilal Dogan ◽  
David Gandy
Keyword(s):  
Power Generation ◽  
Nuclear Power ◽  
Power Plants ◽  
Strain Range ◽  
Creep Damage ◽  
Small Strain ◽  
Systematic Evaluation ◽  
Wide Range ◽  
Creep Fatigue ◽  
Different Temperatures

Failure under creep-fatigue interaction is receiving increasing interest due to an increased number of start-up and shut-down in fossil power generation plants as well as development of newer nuclear power plants employing low-pressure coolant. These situations have promoted the development of various approaches for evaluating its significance. However, most of them are fragment and rather limited in terms of materials and test conditions they covered. Therefore applicability of the proposed approaches to different materials or even different temperatures is uncertain in many cases. The present work was conducted in order to evaluate and compare the representative approaches used in the prediction of failure life under creep-fatigue conditions as well as their modifications, by systematically applying them to available test data on a wide range of materials which have been used or are planned to be used in various types of power generation plants. The following observations have been made from this exercise. (i) Time fraction model has a tendency to be unconservative in general, especially at low temperature and small strain range. Because of the large scatter of the total damage, this shortcoming would be difficult to cover by the consideration of creep-fatigue interaction in a fixed manner. (ii) Classical ductility exhaustion model showed a common tendency to be overly conservative in many situations, especially at small strain ranges. (iii) The modified ductility exhaustion model based on the re-definition of creep damage showed improved predictability with a slightly unconservative tendency. (iv) Energy-based ductility exhaustion model developed in this study seems to show the best predictability among the four procedures in an overall sense although some dependency on strain range and materials was observed.

Fatigue Effect of RCS Branch Line by Thermal Stratification

2003 ◽  
Author(s):  
Hag-Ki Youm ◽  
Kwang-Chu Kim ◽  
Man-Heung Park ◽  
Tea-Eun Jin ◽  
Sun-Ki Lee ◽  
...  
Keyword(s):  
Thermal Stratification ◽  
Nuclear Power ◽  
Power Plants ◽  
Evaluation Methodology ◽  
Element Analysis ◽  
Branch Line ◽  
Reactor Coolant ◽  
Stratification Effect ◽  
Fatigue Evaluation ◽  
Coolant System

Recent events reported at a number of nuclear power plants worldwide have shown that thermal stratification, cycling, and striping in piping can cause excessive thermal stress and fatigue on the piping material. These phenomena are diverse and complicated because of the wide variety of geometry and thermal hydraulic conditions encountered in reactor coolant system. Thermal stratification effect of re-branched lines is not yet considered in the fatigue evaluation. To evaluate the thermal load due to turbulent penetration, this paper presents a fatigue evaluation methodology for a branch line of reactor coolant system with the re-branch line. The locations of fatigue monitoring and supplemented inspections are discussed as a result of fatigue evaluations by Interim Fatigue Management Guideline (ITFMG) and detail finite element analysis. Although the revised CUF was increased less than 50 %, the CUF values for some locations was greater than the ASME Code limits.

Application of Mixed Equivalent Solid and Explicit Hole Models to Analysis of Thick Perforated Plates

2008 ◽  
Author(s):  
E. Josserand ◽  
F. Billon
Keyword(s):  
Thermal Gradient ◽  
Nuclear Power ◽  
Power Plants ◽  
Side Surface ◽  
Element Model ◽  
Fatigue Analysis ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Geometrical Effects ◽  
Load Types

Confronted with the problem of how to conduct a complete fatigue analysis of the Tube Plate (TP) of Tubular and Shell Heat Exchangers and particularly of the Steam Generators equipping nuclear power plants of the Pressurized Water Reactor type (PWR), analysts have developed a method to analyse stress in perforated flat and thick Tube Plates with square penetration (crate) patterns, and in particular to analyse several specific zones such as the Interface Zones and various Effects, such as the Secondary (or Shell) Thermal Gradient Effect (STG Effect), the Thermal Gradient in the No-Tube Lane Effect (TGL Effect) and their interactions. The benefit of the approach is that it enables to analyze mechanical and thermal stress calculated using a full 3D Finite Element model incorporating an equivalent solid and the different Interface Zones, and allowing simulating the specific Thermo-Mechanical Effects. The Interface Zones (IZs) are those between the perforated and non-perforated area, the STG Effect is due to the strong gradient near the Secondary (or Shell) Side surface, the TGL Effect is produced by a temperature gradient across the No-Tube Lane. The method used for the fatigue analysis is based on a “Partitioning Stress Method” by means of which the stress induced by the various load types — mechanical loads, global thermal loads, local thermal effects (STG and TGL Effects), and local geometrical effects (IZs) — are first treated separately and then recombined with their appropriate Stress Multiplier Functions.

The competitiveness of nuclear energy in an era of liberalized markets and restrictions on greenhouse-gas emissions

2009 ◽  
pp. 37-62
Author(s):  
Luigi De Paoli ◽  
Francesco Gulli
Keyword(s):  
Electricity Markets ◽  
Electricity Generation ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Energy ◽  
Fossil Fuels ◽  
Levelized Cost Of Electricity ◽  
Cost Of Electricity ◽  
Generation Costs ◽  
The Cost

- The debate on the benefits of nuclear energy revolves around the very competitiveness of this energy source. This article tries to show why it is not easy to answer unambiguously the question whether or not it is convenient to resort to nuclear power in a given country. After listing the factors on which the cost of electricity generation rests and discussing the range of probability of their value, the levelized cost of electricity generation from nuclear, coal and gas-fired plants is calculated using the Monte Carlo method. The results show that nuclear power is likely to be competitive, especially if policies to combat CO2 emissions will continue in the coming decades. There are, however, some margins of uncertainty, mainly related, to the one hand, to the cost of nuclear plants, that depends on the socio-institutional context, and on the other, to the fossil fuels cost, that are inherently difficult to anticipate even on average. Finally it is noted that the context of liberalized electricity markets may make it more difficult for investors to accept the risk of investing in nuclear power plants and for the community to socialize some of the costs associated with this technology.Key words: Nuclear energy, generation costs, Montecarlo method, environmental impacts.JEL classifications: G11, H23, L72, L94, Q31, Q40

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