Creep Assessment of Large Size High Temperature Components Using Small Creep Test Specimens

2016 ◽  
Author(s):  
Balhassn S. M. Ali
Keyword(s):  
High Temperature ◽  
Creep Test ◽  
Nuclear Power ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Life Time ◽  
Safe Operation ◽  
Large Size ◽  
Testing Techniques ◽  
High Temperature Components

Most of the large components in the thermal, traditional and nuclear power plants such as pressurized vessels and pipes are operating at elevated temperatures. These temperatures and stress are high enough for creep to occur. For variety of reasons many of these power plants are now operating beyond their design life time. It is -known fact that as the high temperature components aged the failure rate normally increases as a result of their time dependent material damage. Further running of these components may become un-safe and dangerous in some cases. Therefore, creep assessment of the high temperature components of these plants is essential for their safe operation. Mainly for economic reasons these components have to be creep assessed as they are in service. However, assessing the creep strength for these high temperature components as they are in service, it can be challenging task, especially when these components are operating under extremely high temperature and/or stress. This paper introduces newly invented, small creep test specimens techniques. These new small types of specimens can be used to assess the remaining life times for the high temperature components, using only small material samples. These small material samples can be removed from the operating components surface, without affecting their safe operation. Two of the high temperature materials are used to validate the new testing techniques.

Rate constant for the H˙ + H2O → ˙OH + H2 reaction at elevated temperatures measured by pulse radiolysis

2017 ◽  
Vol 19 (45) ◽  
pp. 30834-30841 ◽  
Author(s):  
Y. Muroya ◽  
S. Yamashita ◽  
P. Lertnaisat ◽  
S. Sanguanmith ◽  
J. Meesungnoen ◽  
...  
Keyword(s):  
Rate Constant ◽  
Nuclear Power ◽  
Power Plants ◽  
Pulse Radiolysis ◽  
Nuclear Power Plants ◽  
Structural Integrity ◽  
Elevated Temperatures ◽  
Safe Operation

Maintaining the structural integrity of materials in nuclear power plants is an essential issue associated with safe operation.

scholarly journals Benefits, Drawbacks, and Future Trends of Brayton Helium Gas Turbine Cycles for Gas-Cooled Fast Reactor and Very-High Temperature Reactor Generation IV Nuclear Power Plants

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Arnold Gad-Briggs ◽  
Emmanuel Osigwe ◽  
Pericles Pilidis ◽  
Theoklis Nikolaidis ◽  
Suresh Sampath ◽  
...  
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Optimum Operating ◽  
Future Trends ◽  
Design Point ◽  
Gen Iv ◽  
Very High

Abstract Numerous studies are on-going on to understand the performance of generation IV (Gen IV) nuclear power plants (NPPs). The objective is to determine optimum operating conditions for efficiency and economic reasons in line with the goals of Gen IV. For Gen IV concepts such as the gas-cooled fast reactors (GFRs) and very-high temperature reactors (VHTRs), the choice of cycle configuration is influenced by component choices, the component configuration and the choice of coolant. The purpose of this paper to present and review current cycles being considered—the simple cycle recuperated (SCR) and the intercooled cycle recuperated (ICR). For both cycles, helium is considered as the coolant in a closed Brayton gas turbine configuration. Comparisons are made for design point (DP) and off-design point (ODP) analyses to emphasize the pros and cons of each cycle. This paper also discusses potential future trends, include higher reactor core outlet temperatures (COT) in excess of 1000 °C and the simplified cycle configurations.

scholarly journals Study on Probabilistic Safety Goals for Multimodule High-Temperature Gas-Cooled Reactor Based on Chinese Societal Risks

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jinghan Zhang ◽  
Jun Zhao ◽  
Jiejuan Tong
Keyword(s):  
High Temperature ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Regulatory Commission ◽  
Nuclear Safety ◽  
Energy Agency ◽  
Water Reactor ◽  
Regulatory Commission ◽  
High Temperature Gas ◽  
Probabilistic Safety

Nuclear safety goal is the basic standard for limiting the operational risks of nuclear power plants. The statistics of societal risks are the basis for nuclear safety goals. Core damage frequency (CDF) and large early release frequency (LERF) are typical probabilistic safety goals that are used in the regulation of water-cooled reactors currently. In fact, Chinese current probabilistic safety goals refer to the Nuclear Regulatory Commission (NRC) and the International Atomic Energy Agency (IAEA), and they are not based on Chinese societal risks. And the CDF and LERF proposed for water reactor are not suitable for high-temperature gas-cooled reactors (HTGR), because the design of HTGR is very different from that of water reactor. And current nuclear safety goals are established for single reactor rather than unit or site. Therefore, in this paper, the development of the safety goal of NRC was investigated firstly; then, the societal risks in China were investigated in order to establish the correlation between the probabilistic safety goal of multimodule HTGR and Chinese societal risks. In the end, some other matters about multireactor site were discussed in detail.

Application of Damage Mechanics and Polynomial Chaos Expansion for Lifetime Prediction of High-Temperature Components Under Creep-Fatigue Loading

2020 ◽  
Author(s):  
Felix Koelzow ◽  
Muhammad Mohsin Khan ◽  
Christian Kontermann ◽  
Matthias Oechsner
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Damage Mechanics ◽  
Fatigue Loading ◽  
Probabilistic Methods ◽  
Lifetime Prediction ◽  
Model Parameters ◽  
Creep Fatigue ◽  
High Temperature Components ◽  
Mechanics Concepts

Abstract Several (accumulative) lifetime models were developed to assess the lifetime consumption of high-temperature components of steam and gas turbine power plants during flexible operation modes. These accumulative methods have several drawbacks, e.g. that measured loading profiles cannot be used within accumulative lifetime methods without manual corrections, and cannot be combined directly to sophisticated probabilistic methods. Although these methods are widely accepted and used for years, the accumulative lifetime prediction procedures need improvement regarding the lifetime consumption of thermal power plants during flexible operation modes. Furthermore, previous investigations show that the main influencing factor from the materials perspective, the critical damage threshold, cannot be statistically estimated from typical creep-fatigue experiments due to massive experimental effort and a low amount of available data. This paper seeks to investigate simple damage mechanics concepts applied to high-temperature components under creep-fatigue loading to demonstrate that these methods can overcome some drawbacks and use improvement potentials of traditional accumulative lifetime methods. Furthermore, damage mechanics models do not provide any reliability information, and the assessment of the resultant lifetime prediction is nearly impossible. At this point, probabilistic methods are used to quantify the missing information concerning failure probabilities and sensitivities and thus, the combination of both provides rigorous information for engineering judgment. Nearly 50 low cycle fatigue experiments of a high chromium cast steel, including dwell times and service-type cycles, are used to investigate the model properties of a simple damage evolution equation using the strain equivalence hypothesis. Furthermore, different temperatures from 300 °C to 625 °C and different strain ranges from 0.35% to 2% were applied during the experiments. The determination of the specimen stiffness allows a quantification of the damage evolution during the experiment. The model parameters are determined by Nelder-Mead optimization procedure, and the dependencies of the model parameters concerning to different temperatures and strain ranges are investigated. In this paper, polynomial chaos expansion (PCE) is used for uncertainty propagation of the model uncertainties while using non-intrusive methods (regression techniques). In a further post-processing step, the computed PCE coefficients of the damage variable are used to determine the probability of failure as a function of cycles and evolution of the probability density function (pdf). Except for the selected damage mechanics model which is considered simple, the advantages of using damage mechanics concepts combined with sophisticated probabilistic methods are presented in this paper.

Elevated-Temperature Life Assessment

2021 ◽  
pp. 146-166
Author(s):  
Arun Sreeranganathan ◽  
Douglas L. Marriott
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Stress Relaxation ◽  
Damage Mechanics ◽  
Elevated Temperatures ◽  
Constitutive Models ◽  
Life Assessment ◽  
Remaining Life ◽  
High Temperature Components ◽  
Remaining Life Assessment

Abstract This article provides some new developments in elevated-temperature and life assessments. It is aimed at providing an overview of the damage mechanisms of concern, with a focus on creep, and the methodologies for design and in-service assessment of components operating at elevated temperatures. The article describes the stages of the creep curve, discusses processes involved in the extrapolation of creep data, and summarizes notable creep constitutive models and continuum damage mechanics models. It demonstrates the effects of stress relaxation and redistribution on the remaining life and discusses the Monkman-Grant relationship and multiaxiality. The article further provides information on high-temperature metallurgical changes and high-temperature hydrogen attack and the steps involved in the remaining-life prediction of high-temperature components. It presents case studies on heater tube creep testing and remaining-life assessment, and pressure vessel time-dependent stress analysis showing the effect of stress relaxation at hot spots.

Components Qualification for the Safe Operation of Nuclear Power Plants

2017 ◽  
pp. 337-349
Author(s):  
Holger Schmidt ◽  
Martin Betz ◽  
Ingo Ganzmann ◽  
Achim Beisiegel ◽  
Thomas Wagner ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Safe Operation
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