Modeling Swirl Penetration and Thermal Cycling in Un-Isolable Branch Lines of PWR Plants

2003 ◽  
Author(s):  
Jeffrey D. Keller ◽  
Alan J. Bilanin ◽  
Stan T. Rosinski
Keyword(s):  
Thermal Cycling ◽  
Fluid Dynamic ◽  
Model Development ◽  
Development Program ◽  
Fatigue Cracking ◽  
Driving Mechanism ◽  
Primary Coolant ◽  
Pressurized Water ◽  
Branch Line ◽  
High Reynolds

Thermal cycling has been identified as a mechanism that can potentially lead to fatigue cracking in un-isolable branch lines attached to pressurized water reactor (PWR) primary coolant piping. A significant research and development program has been undertaken to understand the mechanisms causing thermal cycling and to model the thermal-hydraulic boundary conditions for use in piping structural analysis. This paper will describe test and modeling results, with primary emphasis on predicting swirl penetration in dead-ended branch lines. Swirl penetration refers to the establishment of an axial vortical structure within the branch line, which has been shown previously to be the primary driving mechanism for thermal cycling in dead-ended branch lines. Swirl penetration testing was performed in a high Reynolds number facility to investigate the fluid dynamic and geometric parameters affecting the formation and decay of branch line swirl. Test results and preliminary model development are presented.

Development of a Thermal Fatigue Screening and Evaluation Methodology for Pressurized Water Reactor Plants

2004 ◽  
Author(s):  
J. D. Keller ◽  
A. J. Bilanin ◽  
S. T. Rosinski
Keyword(s):  
Thermal Cycling ◽  
Development Program ◽  
Fatigue Cracking ◽  
Evaluation Methodology ◽  
Experimental Investigations ◽  
Pressurized Water Reactor ◽  
Primary Coolant ◽  
Modeling Tools ◽  
Pressurized Water ◽  
Water Reactor

Thermal cycling has been identified as a mechanism that can potentially lead to fatigue cracking in un-isolable branch lines attached to pressurized water reactor (PWR) primary coolant piping. A significant research and development program has been undertaken to understand the mechanisms causing thermal cycling and to develop models for predicting the thermal-hydraulic boundary conditions for use in piping structural and fatigue analysis. A combination of first-principles engineering modeling and scaled experimental investigations has been used to formulate improved thermal cycling modeling tools. This paper will provide an overview of the model development program, a summary of the supporting test program, and a description of the thermal cycling model structure. Benchmarking of the thermal cycling model against several PWR plant configurations is presented, demonstrating favorable comparison with cases where thermal stratification and cycling has been previously observed.

Thermal Fatigue of Pwr Coolant System Loop Drain Lines Due to Outflow Activities

2021 ◽  
Author(s):  
Yue Zou ◽  
Brian Derreberry
Keyword(s):  
Thermal Fatigue ◽  
Operating Experience ◽  
Fatigue Cracking ◽  
Screening Methods ◽  
Primary Coolant ◽  
Pressurized Water ◽  
Thermal Transients ◽  
Piping Systems ◽  
Class 1 ◽  
Coolant System

Abstract Thermal cycling induced fatigue is widely recognized as one of the major contributors to the damage of nuclear plant piping systems, especially at locations where turbulent mixing of flows with different temperature occurs. Thermal fatigue caused by swirl penetration interaction with normally stagnant water layers has been identified as a mechanism that can lead to cracking in dead-ended branch lines attached to pressurized water reactor (PWR) primary coolant system. EPRI has developed screening methods, derived from extensive testing and analysis, to determine which lines are potentially affected as well as evaluation methods to perform evaluations of this thermal fatigue mechanism for the U.S. PWR plants. However, recent industry operating experience (OE) indicate that the model used to predict thermal fatigue due to swirl penetration is not fully understood. In addition, cumulative effects from other thermal transients, such as outflow activities, may also contribute to the failure of the RCS branch lines. In this paper, we report direct OE from one of our PWR units where thermal fatigue cracking is observed at the RCS loop drain line close to the welded region of the elbow. A conservative analytical approach that takes into account the influence of thermal stratification, in accordance with ASME Class 1 piping stress method, is also proposed to evaluate the severity of fatigue damage to the RCS drain line, as a result of transients from outflow activities. Finally, recommendations are made for future operation and inspection based on results of the evaluation.

CFD Analysis of the Coolant Mixing within the Upper Plenum of a Pressurized Water Reactor (PWR)

2013 ◽  
Vol 444-445 ◽  
pp. 411-415 ◽  
Author(s):  
Fu Cheng Zhang ◽  
Shen Gen Tan ◽  
Xun Hao Zheng ◽  
Jun Chen
Keyword(s):  
Temperature Distribution ◽  
Fluid Dynamic ◽  
Characteristic Temperature ◽  
Reactor Core ◽  
Flow Distribution ◽  
Sensitivity Study ◽  
Cfd Model ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor

In this study, a Computational Fluid Dynamic (CFD) model is established to obtain the 3-D flow characteristic, temperature distribution of the pressurized water reactor (PWR) upper plenum and hot-legs. In the CFD model, the flow domain includes the upper plenum, the 61 control rod guide tubes, the 40 support columns, the three hot-legs. The inlet boundary located at the exit of the reactor core and the outlet boundary is set at the hot-leg pipes several meters away from upper plenum. The temperature and flow distribution at the inlet boundary are given by sub-channel codes. The computational mesh used in the present work is polyhedron element and a mesh sensitivity study is performed. The RANS equations for incompressible flow is solved with a Realizable k-ε turbulence model using the commercial CFD code STAR-CCM+. The analysis results show that the flow field of the upper plenum is very complex and the temperature distribution at inlet boundary have significant impact to the coolant mixing in the upper plenum as well as the hot-legs. The detailed coolant mixing patterns are important references to design the reactor core fuel management and the internal structure in upper plenum.

scholarly journals Research on the Undulatory Motion Mechanism of Seahorse Based on Dynamic Mesh

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Xinyu Quan ◽  
Ximing Zhao ◽  
Shijie Zhang ◽  
Jie Zhou ◽  
Nan Yu ◽  
...  
Keyword(s):  
Design Method ◽  
Fluid Dynamic ◽  
Underwater Vehicles ◽  
Dynamic Mesh ◽  
Driving Mechanism ◽  
Optimized Design ◽  
Motion Mechanism ◽  
Dorsal Fin ◽  
Propulsion Performance ◽  
Fluent Software

The seahorse relies on the undulatory motion of the dorsal fin to generate thrust, which makes it possess quite high maneuverability and efficiency, and due to its low volume of the dorsal fin, it is conducive to the study of miniaturization of the driving mechanism. This paper carried out a study on the undulatory motion mechanism of the seahorse’s dorsal fin and proposed a dynamic model of the interaction between the seahorse’s dorsal fin and seawater based on the hydrodynamic properties of seawater and the theory of fluid-structure coupling. A simulation model was established using the Fluent software, and the 3D fluid dynamic mesh was used to study the undulatory motion mechanism of the seahorse’s dorsal fin. The effect of the swing frequency, amplitude, and wavelength of the seahorse’s dorsal fin on its propulsion performance was studied. On this basis, an optimized design method was used to design a bionic seahorse’s dorsal fin undulatory motion mechanism. The paper has important guiding significance for the research and miniaturization of new underwater vehicles.

scholarly journals Numerical Investigation of the Flow around a Feather Shuttlecock with Rotation

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 28
Author(s):  
John Hart ◽  
Jonathan Potts
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Numerical Investigation ◽  
Computational Fluid Dynamic ◽  
High Reynolds Number ◽  
Fluid Dynamic ◽  
Flow Structures ◽  
Drag Forces ◽  
High Reynolds

This paper presents the first scale resolving computational fluid dynamic (CFD) investigation of a geometrically realistic feather shuttlecock with rotation at a high Reynolds number. Rotation was found to reduce the drag coefficient of the shuttlecock. However, the drag coefficient is shown to be independent of the Reynolds number for both rotating and statically fixed shuttlecocks. Particular attention is given to the influence of rotation on the development of flow structures. Rotation is shown to have a clear influence on the formation of flow structures particularly from the feather vanes, and aft of the shuttlecock base. This further raises concerns regarding wind tunnel studies that use traditional experimental sting mounts; typically inserted into this aft region, they have potential to compromise both flow structure and resultant drag forces. As CFD does not necessitate use of a sting with proper application, it has great potential for a detailed study and analysis of shuttlecocks.

Evaluation of Residual Stresses in Dissimilar Weld Joints

2011 ◽  
Vol 681 ◽  
pp. 182-187 ◽  
Author(s):  
Alix Bonaventur ◽  
Danièle Ayrault ◽  
Guillaume Montay ◽  
Vincent Klosek
Keyword(s):  
Residual Stresses ◽  
Weld Joint ◽  
Safety Issue ◽  
Austenitic Steels ◽  
Hole Drilling ◽  
Primary Coolant ◽  
Pressurized Water ◽  
Dissimilar Weld ◽  
Dissimilar Welds ◽  
Water Reactors

Dissimilar metal joints between pipes of ferritic and austenitic steels are present in primary coolant circuit of pressurized water reactors. Over the last years in particular in USA and Japan, stress corrosion cracks, often associated with weld repairs, have been observed for some dissimilar welds made with an Inconel filler metal. The integrity of this type of components is thus a major safety issue. In this context, the goal of this work is to evaluate the welding residual stresses field for a dissimilar weld joint. A representative bi-metallic tubular weld joint was fabricated and residual stresses profiles in the different weld zones were evaluated by means of the hole drilling and neutron diffraction methods.

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