Hydro-thermo-mechanical analysis on high cycle thermal fatigue induced by thermal striping in a T-junction

Thermal striping phenomena caused by mixing of fluids at different temperature is one of the most important issues in design of Fast Breeder Reactors (FBRs), because it may cause high-cycle thermal fatigue in structure and affect the structural integrity. A numerical simulation code MUGTHES has been developed to investigate thermal striping phenomena and to estimate high cycle thermal fatigue in FBRs. In this study, numerical simulation for the WATLON experiment which was the water experiment of a T-junction piping system (T-pipe) conducted in JAEA was carried out to validate the MUGTHES and to investigate the relation between the mechanism of temperature fluctuation generation and the unsteady motion of large eddy structures. In the numerical simulation, the large eddy simulation (LES) approach with standard Smagorinsky model was employed as eddy viscosity model to simulate large-scale eddy motion in the T-pipe. The mesh as the same with the previous study as reference, the finer mesh and the coarser mesh arrangements were employed to estimate the Grid Convergence Index (GCI) for uncertainty quantification in the validation process. The modified method of the GCI estimation based on the least squire version could successfully quantify uncertainty. Through the numerical simulations, it was indicated that the fine mesh arrangement could improve the temperature distribution in the wake. It could be found that the thermal mixing phenomena in the T-pipe were caused by the mutual interaction of the necklace-shaped vortex around the wake from in the front of the branch jet, the horseshoe-shaped vortex and the Karman’s vortex motions in the wake.

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Numerical analysis of thermal striping induced high cycle thermal fatigue in a mixing tee

Nuclear Engineering and Design ◽

10.1016/j.nucengdes.2008.06.014 ◽

2009 ◽

Vol 239 (5) ◽

pp. 833-839 ◽

Cited By ~ 60

Author(s):

Jeong Ik Lee ◽

Lin-wen Hu ◽

Pradip Saha ◽

Mujid S. Kazimi

Keyword(s):

Numerical Analysis ◽

Thermal Fatigue ◽

Thermal Striping ◽

High Cycle Thermal Fatigue

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High-Cycle Analytical Thermal Fatigue Tests on Pipe Structures

Selected Topics on Aging Management, Reliability, Safety and License Renewal ◽

10.1115/pvp2002-1374 ◽

2002 ◽

Author(s):

J. M. Stephan ◽

F. Curtit

Keyword(s):

Thermal Fatigue ◽

Thermal Stresses ◽

Heat Removal ◽

Fatigue Tests ◽

Bench Test ◽

Surface Finishes ◽

Water Sprays ◽

Thermal Striping ◽

High Cycle Thermal Fatigue ◽

Non Destructive

In 1998, a leak occurred in the main mixing zone of the residual heat removal systems (RHR) of the EDF CIVAUX nuclear plant unit 1. The crack is attributed to high-cycle thermal fatigue due to the fluid thermal turbulences. An research and development (R&D) program is now being conducted at EDF to understand the incident and to assess the risks of cracks in other mixing zones. This program includes thermal-hydraulic tests on mock-ups and their numerical interpretation, material testing in high-cycle fatigue, structure tests on mock-ups submitted to high-cycle thermal stresses and their interpretations, and developments in non destructive evaluations in the presence of crazing zones (thermal striping). After a brief presentation of the R&D program, the paper presents a new high-cycle thermal fatigue bench test, named INTHERPOL, for pipe structures. The thermal cycles consist of periodic controlled cold shocks by water sprays and hot shocks by infrared radiations on the inner surface of part of the structure. The structure under test, the water spray devices and infrared modules are inserted into a tank to allow constant control of the environment. The types of pipe structures tested include plain or welded structures and various industrial surface finishes. The first tests results and their numerical interpretations are presented.

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

Volume 5: High-Pressure Technology; ASME NDE Division; 22nd Scavuzzo Student Paper Symposium and Competition ◽

10.1115/pvp2014-28393 ◽

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.

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