Predicting Steam Generator Auxiliary Feedwater Nozzle Thermal Stratification Transients and Fatigue Effects in Complex Systems

2005 ◽  
Author(s):  
E. L. Cranford ◽  
M. A. Gray ◽  
S. Sahgal
Keyword(s):  
Steam Generator ◽  
Thermal Stratification ◽  
Transient Characteristics ◽  
Thermal Transients ◽  
Fatigue Monitoring ◽  
Interacting Systems ◽  
Thermal Transient ◽  
Related Stress ◽  
Evaluation And Monitoring ◽  
System Characteristics

External thermocouple measurements on auxiliary feedwater piping revealed thermal transient cycles that warranted evaluation and monitoring. Development of a fatigue monitoring system for the associated steam generator auxiliary feedwater nozzles required consideration of a number of complex factors. The thermal transients measured on the external surface often indicated the presence of thermal stratification cycling of the contained fluids. The characteristics of the transients were influenced by complex combinations of the thermal hydraulic influence of four interacting systems. The transient characteristics were found to be very sensitive to small changes in the system parameters. This paper describes methods used to simulate these complex system characteristics and obtain reasonable predictions of local thermal transient characteristics that correlate with the measured data. The predicted transient loads are used to calculate the related stress and fatigue impact in the nozzles.

Thermal Stratification in Steam Generator Feedwater Lines

1984 ◽  
Vol 106 (1) ◽  
pp. 78-85 ◽  
Author(s):  
R. Braschel ◽  
M. Miksch ◽  
G. Schu¨cktanz
Keyword(s):  
Stress Intensity ◽  
Steam Generator ◽  
Thermal Stratification ◽  
Load Case ◽  
Steam Generators ◽  
Design Modification ◽  
Material Fatigue

In recent years cracks have been found in the inlet nozzles of feedwater lines of steam generators. These cracks occur as a result of material fatigue. Thermal stratification in the feedwater is probably one of the factors primarily responsible for the fatigue. This paper describes methods of calculating the stress intensity ranges occurring as a result of the stratification. In addition, a design modification (a diversion tank) is proposed which effectively prevents the occurrence of this load case.

A Methodology for Online Fatigue Monitoring With Consideration of Temperature-Dependent Material Properties Using Artificial Parameter Method

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Hengliang Zhang ◽  
Yangheng Xiong ◽  
Chu Nie ◽  
Danmei Xie ◽  
Kunfeng Sun
Keyword(s):  
Material Properties ◽  
Thermal Stresses ◽  
Function Technique ◽  
Parameter Method ◽  
Temperature Dependent ◽  
Linear Superposition ◽  
Thermal Transients ◽  
Fatigue Damage Accumulation ◽  
Fatigue Monitoring ◽  
Artificial Parameter

Following the basis of the ASME codes, the major nuclear components are designed to successfully avoid the fatigue failure. However, such design is generally very conservative and it is necessary to accurately assess the fatigue life of the components for the optimal life. The assessment of fatigue damage accumulation due to the thermal transients is currently performed via online fatigue monitoring systems. The algorithms for online calculation of thermal stress are one of the main components of these systems and are often based on the Green function technique (GFT), in which machine parameters such as fluid temperatures, pressures, and flow rates are converted into metal temperature transients and thermal stresses. However, since the GFT is based upon the linear superposition principle, it cannot be directly used when the temperature-dependent material properties are considered. This paper presents a methodology to consider the temperature- dependent material properties using artificial parameter method. Two cases are presented to compare the results calculated from the proposed models with those calculated by finite element method (FEM). It is found that the temperature-dependent material properties have significant influence on the maximum peak stresses which can be accurately captured by the models proposed in this work.

Prediction of Fluid Temperatures From Measurements of Outside Wall Temperatures in Pipes

1994 ◽  
Vol 116 (2) ◽  
pp. 179-187 ◽  
Author(s):  
M. Guyette
Keyword(s):  
Temperature Measurement ◽  
Wall Temperature ◽  
Industrial Application ◽  
Thermal Stratification ◽  
Transfer Functions ◽  
Fluid Temperature ◽  
Convolution Integral ◽  
Thermal Transients ◽  
Points Of Interest ◽  
Piping Systems

The monitoring of the fatigue induced by thermal transients in thick-walled structures becomes more and more currently performed, mainly on equipment the failure of which could present severe implications on the environment. The easiest way of performing this monitoring is by use of Green’s functions in a convolution integral of the measured fluid temperatures to assess the stresses at the points of interest. Numerous cases, however, exist where the fluid temperatures are not available and only an outside wall temperature measurement is feasible. This paper describes the development and the industrial application of the so-called “inverse” transfer functions to predict the evolution of the fluid temperature from measurements of the metal temperature either at the outside or in the wall of the considered equipment. Some applications are shown for the particular case of the thermal stratification in piping systems.

Fatigue Monitoring: Case Studies in Nuclear Power Plant

2018 ◽  
Author(s):  
G. Bourguigne ◽  
F. Schroeter
Keyword(s):  
Power Plant ◽  
Thermal Stratification ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Life Extension ◽  
Monitoring Systems ◽  
Fatigue Monitoring ◽  
Cycle Count ◽  
Critical Components

During design of Class I components in Nuclear Power Plants, cumulative usage factors (CUF) are conservatively calculated to estimate fatigue damage, and results must be below the limits of the applicable codes. Nevertheless, when these results are used to evaluate the possibility of using these components for an extended life, the results are frequently above code limits. Many Nuclear Power Plants have installed commercial fatigue monitoring systems at critical components in order to assess transient severity and cycle count for life extension fatigue calculations among other reasons. Since the commissioning of the system, unexpected operation modes and thermal stratification was discovered and evaluations needed to be done. Findings, interpretations and solving are presented in this paper.

Thermal transient characteristics of die attach in high power LED PKG

2008 ◽  
Vol 48 (3) ◽  
pp. 445-454 ◽  
Author(s):  
Hyun-Ho Kim ◽  
Sang-Hyun Choi ◽  
Sang-Hyun Shin ◽  
Young-Ki Lee ◽  
Seok-Moon Choi ◽  
...  
Keyword(s):  
High Power ◽  
Transient Characteristics ◽  
Die Attach ◽  
High Power Led ◽  
Thermal Transient

Experiments on thermal stratification in inlet nozzle of steam generator

2007 ◽  
Vol 21 (4) ◽  
pp. 654-663 ◽  
Author(s):  
Sang-Nyung Kim ◽  
Cheol-Hong Kim ◽  
Bum-Su Youn ◽  
Hag-Ki Yum
Keyword(s):  
Steam Generator ◽  
Thermal Stratification

Assessment of a Piping System Subjected to Thermal Stratification and Thermal Striping

2010 ◽  
Author(s):  
Somnath Chattopadhyay
Keyword(s):  
Thermal Stratification ◽  
Nuclear Power ◽  
Power Plants ◽  
Thermal Stresses ◽  
Temperature Gradients ◽  
Low Flow ◽  
Piping System ◽  
Thermal Transients ◽  
Fatigue Evaluation ◽  
Thermal Striping

Piping systems in nuclear power plants are often designed for pressure and mechanical loadings (including seismic loads) and operating thermal transients. In the last few decades a number of failures have occurred due to thermal stratification caused by the mixing of hot and cold fluids under certain low flow conditions. Such stratified temperature fluid profiles give rise to circumferential metal temperature gradients through the pipe leading to high stresses causing fatigue damage. In this work, thermal stresses due to such temperature gradients have been calculated using a finite element method. The peak stresses calculated by this method has been used for fatigue evaluation. In addition the stresses due to thermal striping associated with stratification have also been independently assessed for high cycle fatigue. The method outlined in this paper is a simplified conservative procedure to obtain stratification stresses.

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