scholarly journals Fast Calculation of Transient Thermal Stress in Surge Lines with Thermal Stratification Region

2021 ◽  
Vol 11 (7) ◽  
pp. 3216
Author(s):  
Bingjun Gao ◽  
Mingze Li ◽  
Chulin Yu ◽  
Yan Li
Keyword(s):  
Thermal Stress ◽  
Thermal Stratification ◽  
Nuclear Power ◽  
Power Plants ◽  
Fluid Temperature ◽  
Fast Calculation ◽  
Database Construction ◽  
Transient Thermal Stress ◽  
Stratification Region ◽  
Transient Thermal

Nuclear power plants applying for license renewal are required to undertake a fatigue assessment of various components, which demands the fast calculation of transient thermal stress of the fatigue-sensitive components such as surge lines. In this study, the strategy of Green’s function database construction for the thermal stratification region was investigated, and the thermal stress calculation was shown to be more accurate by dividing the flow cases and thermal zones. Furthermore, a method to determine the fluid temperature for the thermal zones of the thermal stratification region was studied. In addition to the temperature of the hot leg fluid and the outlet fluid from the pressurizer, seven thermocouples installed on the outside wall in the thermal stratification region were used to determine the fluid temperature of thermal zones with stratification, and the calculation result of the fluid temperature was verified with the temperature Green’s functions.

A Study on Thermal Stress Evaluation of Safety Injection System for NPPs Considering Leakage Effect

2011 ◽  
Author(s):  
Hee-Dong Sung ◽  
Sun-Hye Kim ◽  
Ik-Joong Kim ◽  
Young-Jin Kim ◽  
Jeong-Soon Park ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Thermal Stratification ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Injection System ◽  
Stress Evaluation ◽  
Branch Line ◽  
Leakage Model ◽  
Cfd Analyses

Several piping failures caused by thermal stratification have been reported in some nuclear power plants since the early 1980s. However, this kind of thermal effect was not considered when the old vintage nuclear power plants were designed. Thermal stratification is usually generated by turbulent penetration from the RCS to branch line or leakage through damaged part of valve in branch line. In this paper, using the CFD analysis, characteristics of thermal stratification in a safety injection system of PWR plant were investigated and thermal stress evaluation was also conducted. First, CFD analyses were carried out on in-leakage model and out-leakage model according to operating condition. The case of out-leakage, the thermal stratification based on temperature distribution was generated a little at the rear of 1st valve. In contrast, significant thermal stratification was generated in front of 1st valve in in-leakage model because the effect of rapid flow velocity from RCS.

Thermal Stress Response to Boundary Oscillation Between Hot and Cold Fluid Temperature

2014 ◽  
Author(s):  
Kohei Soda ◽  
Takato Mizutani ◽  
Naoto Kasahara
Keyword(s):  
Thermal Stress ◽  
Frequency Response ◽  
Response Function ◽  
Thermal Fatigue ◽  
Thermal Stratification ◽  
Frequency Response Function ◽  
Nuclear Power ◽  
Fluid Temperature ◽  
Thermal Striping ◽  
High Cycle Thermal Fatigue

In nuclear power plants, high cycle thermal fatigue induced by temperature fluctuation of the coolant is one of frequent failure modes. To ensure the safety of nuclear power plant systems, it is important to prevent thermal fatigue failure. Typical causes of high cycle thermal fatigue are thermal striping at Tee-junction and thermal stratification oscillation. In order to evaluate thermal stress caused by thermal striping, a frequency response function has been developed. This function was derived from a heat transfer and thermal elastic theories, and can adequately evaluate thermal stress induced by temperature gradient into wall-thickness direction. However, this theoretical method cannot adequately evaluate thermal stress by thermal stratification oscillation, because this phenomenon has the fluid temperature distribution gradient along axial direction. To investigate the mechanism of thermal stress generated by oscillation of thermal stratification, two types of models were studied. In the first type, fluid temperature oscillates with sinusoidal history at the same location, and in the second one, the boundary layer of hot and cold fluid temperature moves with sinusoidal velocity. Through clarification of the stress generation mechanism, the frequency response function was improved to evaluate stress by the thermal stratification oscillation. Applicability of this function was verified through agreement with finite element simulations.

scholarly journals OS0802 Analysis of a Smart Multilayer Composite Disk for Control of Transient Thermal Stress

2013 ◽  
Vol 2013 (0) ◽  
pp. _OS0802-1_-_OS0802-2_
Author(s):  
Fumihiro ASHIDA ◽  
Sei-ichiro SAKATA ◽  
Takuya MORIMOTO ◽  
Tsuyoshi YAMADA
Keyword(s):  
Thermal Stress ◽  
Multilayer Composite ◽  
Transient Thermal Stress ◽  
Transient Thermal ◽  
Composite Disk
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