The Surge Line Stress Analysis Model Setup With the Consideration of Thermal Stratification

2014 ◽  
Author(s):  
Jianjun Wang ◽  
Zengfang Ge ◽  
Zhongning Sun ◽  
Changqi Yan
Keyword(s):  
Stress Analysis ◽  
Transient Process ◽  
Thermal Stratification ◽  
Nuclear Power ◽  
Transient Temperature ◽  
Analysis Model ◽  
Pressurized Water ◽  
Line Model ◽  
Transient Temperature Distribution ◽  
Surge Line

In this paper, we deal with a typical pressurizer surge line in a conventional pressurized water reactor (PWR). This study is performed to develop an understanding of thermal stratification phenomenon, which may occur in the surge line during either normal condition or transient process, in the pressurizer surge line. The pressurizer surge line model of Daya Bay nuclear power plant is used as base analysis model, in which the hot leg is taken into account. The transient temperature distribution required to assess the phenomenon along the pressurizer surge line is obtained through CFD analysis technology using ANSYS FLUENT. The temperature loads are transferred to ANSYS Mechanical for stress evaluation for the heat up transient process. Subsequently, the usage factor is calculated on the basis of ASME Section-III design curve. The possible mitigation scheme for the thermal stratification phenomenon of changing the layout angles is also simulated and analyzed in detail. The results show that the thermal stratification phenomenon will occur both in normal operating condition and in heat up transient process. The circumfluent effect makes the thermal stratification phenomenon exhibit unique profile due to the introduction of the hot leg. The continuous spray mass flow rate may influence both the temperature difference and the occurrence range for the thermal stratification phenomenon. The stress analysis incorporating both temperature load and pressure load is performed for pressurizer surge line model with hot leg for the conservative and complete heat up case.

A New Method to Weaken Thermal Stratification Phenomena in Pipes of Nuclear Power Plant

2013 ◽  
Author(s):  
Shengfei Wang ◽  
Yuxin Pang ◽  
Xiaojing Li ◽  
Dandan Fu ◽  
Yang Li ◽  
...  
Keyword(s):  
Thermal Stratification ◽  
Nuclear Power ◽  
Thermal Stresses ◽  
Heat Pipes ◽  
New Method ◽  
Simple Experiment ◽  
Pressurized Water ◽  
Piping Systems ◽  
Surge Line ◽  
Water Reactors

Thermal stratification phenomena are observed in piping systems of pressurized water reactors, especially in the pressurizer surge line. As a result of the thermal stratification induced thermal stresses, fatigue problems can occur in the pipework. US NRC requirements have also identified flow stratification in surge lines as a phenomenon that must be considered in the design basis of surge lines. In this paper, a new method to reduce thermal stratification is proposed. As we all know, heat pipe is a simple device with no moving parts and can transfer large quantities of heat over fairly large distance. The new method is that using heat pipes to weaken the thermal stratification. In order to validate the new method, a simple experiment and theoretical analysis was taken. The results show that, the temperature difference of thermal stratification with heat pipes is smaller than the stratification without heat pipes. A design scheme was also given at the end of paper.

Effect of Heat-Up Transient Condition on the Thermal Stratification in Nuclear Power Plant Surgeline

2009 ◽  
Author(s):  
Young-Jong Kim ◽  
Maan-Won Kim ◽  
Eunmi Ko ◽  
Jae-Gon Lee ◽  
Byoung Chul Kim
Keyword(s):  
Flow Rate ◽  
Thermal Stratification ◽  
Nuclear Power ◽  
Element Model ◽  
Transient Condition ◽  
Analysis Model ◽  
Stratification Effect ◽  
Surge Line ◽  
Temperature And Pressure ◽  
Temperature Rate

During operating transients of the pressurizer, thermal stratification effect may occur especially in the horizontal parts of surge line. Generally, the fatigue usage factor of surge line is comparative high, due to its operating temperature and pressure transients and its thermal stratification loads. Traditional 2-D finite element model (FEM) for thermal stratification analysis has excessive conservativeness. To reduce such an excessive conservativeness, 3-D numerical analysis model for fluid-structure interaction (FSI) problem in the surgeline and some parametric FSI analyses were performed with different heat-up temperature rate and flow rate in the inlet of surgeline during plant heat-up. Based on these FSI analysis results, an efficient condition to reduce the excessive conservativeness in surgeline stratification analysis could be proposed in terms of heat-up rate and flow rate.

CFD Analysis of PWR Surge Line Subjected to Thermal Stratification

2012 ◽  
Vol 468-471 ◽  
pp. 78-82 ◽  
Author(s):  
Athar Rasool ◽  
Zhong Ning Sun ◽  
Jian Jun Wang ◽  
Zeng Fang Ge ◽  
Majid Ali
Keyword(s):  
Thermal Stratification ◽  
Power Plants ◽  
Structural Integrity ◽  
Complex Geometry ◽  
Transient Temperature ◽  
3D Analysis ◽  
Pressurized Water ◽  
Temperature Distributions ◽  
Operational Life ◽  
Surge Line

Thermal stratification effects have been a great concern in a pressurizer surge line of pressurized water reactor (PWR) since 1988. These effects may damage the structural integrity and contribute in reducing the operational life time of pressurizer surge line. Several nuclear power plants operators have so far reported such mechanical damages. To realistically assess the structural integrity of pressurizer surge line subjected to thermal stratification, it is necessary to analyze the transient temperature distribution. Several researchers and scholars have carried out considerable efforts to determine the temperature distributions in the pressurizer surge line. In this study, an effort has been made to simulate the behavior of thermally stratified flow and predict the transient temperature distributions in the pressurizer surge line realistically. To obtain realistic results for such complex geometry of pressurizer surge line 3D analysis is performed using CFX commercially available CFD software. The transient temperature distributions obtained are presented and discussed.

Experimental Investigation on Flash Evaporation Related to Pipe Leakage

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Benan Cai ◽  
Qi Zhang ◽  
Yu Weng ◽  
Hongfang Gu ◽  
Haijun Wang
Keyword(s):  
High Temperature ◽  
Thermal Fatigue ◽  
Weber Number ◽  
Thermal Stratification ◽  
Nuclear Power ◽  
Power Plants ◽  
Response Speed ◽  
Flash Evaporation ◽  
Main Pipe ◽  
Surge Line

Abstract Pipelines such as the surge line and main pipe are easily subjected to thermal stratification and thermal fatigue as a result of the nonuniform temperature distribution in the nuclear power plants. When the surge line or main pipe subjected to thermal stratification and thermal fatigue keeps operating for long time, the pipe leakage may happen due to the existence of pipeline crack. When the fluids with high temperature and pressure leak in the crack, the water will evaporate quickly, which means this process belongs to spray flash evaporation process. The flash evaporation related to pipe leak was experimentally studied in the paper. The experiment was carried out under high temperature and high pressure with low spray rate. The temperature and relative humidity (T&H) variations over time were monitored in the experiment with installing T&H detectors. The T&H variations at different measurement positions and with different spray rates were analyzed, respectively. In addition, the effect of the dimensionless parameters including the Weber number and Jakob number was also investigated. Results indicated that the response speed increased with the increase of the spray flow rate. Higher Weber number and higher Jakob number led to higher evaporation rate. The slight pipe leakage can be predicted by using the (T&H) in the hazardous areas.

A Study of Some Key Parameters Used in the Environmental Fatigue Evaluation of a Hot Leg Surge Nozzle

2009 ◽  
Author(s):  
Tim F. Wiley ◽  
Tim J. Pournaras ◽  
Chris T. Kupper ◽  
Mark A. Gray ◽  
Seth A. Swamy
Keyword(s):  
Nuclear Power ◽  
Sensor Data ◽  
Maximum Temperature ◽  
Pressurized Water Reactor ◽  
Maximum Temperature Difference ◽  
Pressurized Water ◽  
Coolant Pump ◽  
Surge Line ◽  
Fatigue Evaluation ◽  
Made In

When considering environmentally assisted fatigue (EAF) in the fatigue evaluation of nuclear power plant components, some assumptions made pertaining to plant operation in the design basis fatigue analyses have to be re-evaluated to accommodate potential increase in fatigue usage factors resulting from environmental effects. The surge line was identified in NUREG/CR-6260 [1] to be a representative component for the evaluation of EAF for Pressurized Water Reactor (PWR) plants. For some PWR plants, the hot leg surge nozzle is one of the components evaluated for environmentally assisted fatigue. The hot leg surge nozzle was chosen for this study because the results of the fatigue evaluation are highly dependent on several key parameters, such as maximum temperature difference between the pressurizer and hot leg piping during heatups and cooldowns, the amount of temperature sensor data available along the surge line, availability of thermal event cycle counting, and the frequency and timing of reactor coolant pump starts and stops during heatups and cooldowns. This paper assesses the impacts of the assumptions made in these key parameters on the environmental fatigue evaluation results for a typical hot leg surge nozzle.

Radiation Induced Thermal Stratification in Surface Layers of Stagnant Water

1975 ◽  
Vol 97 (1) ◽  
pp. 35-40 ◽  
Author(s):  
D. M. Snider ◽  
R. Viskanta
Keyword(s):  
Energy Transfer ◽  
Temperature Distribution ◽  
Thermal Stratification ◽  
Pure Water ◽  
Spectral Characteristics ◽  
Transient Temperature ◽  
Radiant Heating ◽  
Surface Layers ◽  
Stagnant Water ◽  
Transient Temperature Distribution

Analysis is developed for the time dependent thermal stratification in surface layers of stagnant water by solar radiation. The transient temperature distribution is obtained by solving the one-dimensional energy equation for combined conduction and radiation energy transfer using a finite difference method. Experimentally, solar heating of water is simulated using tungsten filament lamps in parabolic reflectors of known spectral characteristics. The transient temperature distribution resulting from radiant heating of pure water in a glass-walled test cell is measured with a Mach-Zehnder interferometer. Measured and predicted temperature profiles show good agreement, thus verifying the radiation and total energy transfer models in stagnant water. It is found that the boundary condition at the air-water interface and internal radiant heating rate must be correctly specified in order to properly model stratification of water by radiation.

Analysis of the Velocity Field of Thermal Stratification in Pipes

2013 ◽  
Author(s):  
Limiao Xing ◽  
Wenbin Zhuo ◽  
Bingde Chen ◽  
Dewen Yuan ◽  
Wanyu Xiong
Keyword(s):  
Cross Section ◽  
Thermal Stratification ◽  
Nuclear Power ◽  
Power Plants ◽  
Sudden Change ◽  
Fatigue Cracking ◽  
Transient Temperature ◽  
Pressure Drops ◽  
Safety Issues ◽  
Cfd Method

The thermal stratification plays an important role in the aging of the piping because of the excessive stresses caused by the temperature differences in the cross section of the pipe. These stresses can limit the lifetime of the piping, causing deformation, support failure, thermal fatigue, cracking, etc. Several nuclear power plants have experienced such mechanical damages. This phenomenon has been addressed as one of the significant safety issues in nuclear power plant operation. Research of the thermal stratification phenomenon by both Computational Fluid Dynamics (CFD) method and experimental method are performed in this paper. It is observed that in the thermal stratification region, the cold and hot fluid in the pipe flow conversely in the numerical analysis. This phenomenon is caused by the flow characteristic that the surge flow pushes the fluid of the whole cross section downstream, causing pressure drops at the upper or bottom section of the surge flow. The fluid downstream flows backwards because of the pressure difference. In the experiment the converse flow when thermal stratification happens in the pipe is confirmed, which causes a sudden change of the tendency of transient temperature evolutions and the fluctuation of the temperature. Further experimental analysis and validation are needed as this phenomenon enlarges the temperature difference of the pipelines.

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