A Coupled Fluid-Solid Model to Investigate Leak Rates for Leak-Before-Break Assessments

2014 ◽  
Author(s):  
Peter Gill ◽  
Keith Davey ◽  
John Sharples
Keyword(s):  
Finite Element ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Model ◽  
Fluid Model ◽  
Crack Opening ◽  
Element Model ◽  
Leak Rate ◽  
Solid Model ◽  
Leak Before Break

A multiscale model is discussed here which incorporates fluid mechanics into a structural model. This is so that leak rates can be output from a crack in a finite element model without any complex meshing or post processing. The model can be implemented into any standard finite element solver, meaning leak rates can be investigated for cracks in realistic components. Crack opening area is obtained directly from the special elements that surround the crack, and leak rate is output with the solution. By adopting this holistic approach, it makes the calculation of leak rate more efficient, with the added benefit of higher accuracy. Furthermore, this provides a tool to investigate thermal interactions between the fluid and solid. Presented in this paper is a description of the physical model, and an outline of the numerical solution procedure. Leak rates are also discussed for the case of crack in a plate. The numerical tool provides an effective way of coupling a fluid model with microscale effects, to a macroscale solid model. Investigations using this new method have the potential to reduce uncertainty in leak rate evaluation. Also, by reducing the uncertainty, it is suggested that there would be an increase in the number of situations where Leak-before-Break could be applied in Nuclear Power Plants.

Estimates of Elastic Crack Opening Displacements of Slanted Through-Wall Cracks in Plate and Cylinder

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
Yeon-Sik Yoo ◽  
Suhn Choi ◽  
Keun-Bae Park
Keyword(s):  
Finite Element ◽  
Crack Opening ◽  
Three Dimensional ◽  
Bending Moment ◽  
Element Model ◽  
Finite Element Analyses ◽  
Opening Displacement ◽  
Elastic Crack ◽  
Leak Before Break ◽  
The Finite Element Model

This paper provides tractable solutions for elastic crack opening displacement (COD) of slanted through-wall cracks in plates and cylinders. The solutions were developed via detailed three dimensional elastic finite element analyses. The COD values were calculated along the thickness at the center of the crack. As for the loading conditions, only remote tension was considered for the plates, whereas remote tension, global bending moment, and internal pressure were considered for the cylinders. The finite element model employed in the present analysis was verified by using existing solutions for a cylinder with an idealized circumferential through-wall crack. The present results can be used to evaluate leak rates of slanted through-wall cracks, which can be used as a part of a detailed leak-before-break analysis considering more realistic crack shape development.

Assessing Prestress Losses in a Nuclear Containment Structure for License Renewal

2019 ◽  
Author(s):  
Eric Kjolsing ◽  
Randy James ◽  
Keith Kubischta ◽  
Dan Parker
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Nuclear Power ◽  
Power Plants ◽  
Element Model ◽  
Paper Analysis ◽  
Design Parameters ◽  
Original Design ◽  
Structural Capacity ◽  
Post Tensioning

Abstract Nuclear power plants around the world are nearing the end of their designed service life. Sufficient structural capacity must be demonstrated to extend each plant’s operating license when accounting for concrete creep, shrinkage, and tendon relaxation past the original design life. This may take the form of in-situ values which meet the design allowable or, as outlined in this paper, analysis models which demonstrate capacity. This paper presents an analysis methodology for a concrete containment structure utilizing grouted post-tensioned tendons representative of a non-US design. The methodology is intended to demonstrate that a structure can still meet established design requirements while accounting for creep, shrinkage, and tendon relaxation. The analysis effort is performed in multiple stages. First, design parameters feeding into post-tensioning loss calculations are identified and assigned statistical distributions. Probabilistic estimates of the post-tensioning losses are developed using both a variational and Monte Carlo approach. Second, a finite element model of a representative containment structure is developed with tendons and reinforcement explicitly modeled. Lastly, the finite element model is used in example analyses to demonstrate future performance and pressure capacity accounting for projected tendon losses.

A Special Finite Element for Leak-Before-Break Analysis

2012 ◽  
Author(s):  
Peter J. Gill ◽  
John Sharples ◽  
Keith Davey
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Crack Opening ◽  
Nuclear Industry ◽  
Leak Rate ◽  
Assessment Procedure ◽  
Factors Affecting ◽  
First Results ◽  
Crack Faces ◽  
Leak Before Break

Leak-before-Break is increasingly being used as part of safety justifications, particularly within the nuclear industry. In order to make a Leak-before-Break case for a pressurised component, it is necessary to determine leak rates through cracks under the operating load conditions. The R6 assessment procedure provides equations to calculate leak rates from a known crack opening area. Leak rates evaluated from this calculational route, however, can be subject to safety factors being applied due to various uncertainties. As such there is a strong motivation to better understand the factors affecting leak rates through cracks in pipes, so that there is less conservatism in the leak rate estimation. To perform the investigations into these factors, a special finite element has been developed. This element uses the extended finite element method to model cracks with boundary conditions on the faces due to the leaking fluid. Previous work has shown that leak rates through a crack are affected by closure of the crack, which is due to convective heat transfer from the leaking fluid to the crack faces. Therefore the new 2-D element is used to investigate this and it shows the effect of heat transfer and pressure acting on the crack faces. The first results of leak rate evaluations, using this new element, are presented in the paper.

Vertical soil-structure interaction effects

1979 ◽  
Vol 69 (1) ◽  
pp. 221-236
Author(s):  
R. R. Little ◽  
D. D. Raftopoulos
Keyword(s):  
Nuclear Power ◽  
Soil Structure ◽  
Power Plants ◽  
Structural Model ◽  
Free Field ◽  
Interaction Effects ◽  
Soil Structure Interaction ◽  
Response Curves ◽  
Transformation Techniques ◽  
Structure Interaction

abstract An analytical expression describing the three-dimensional vertical soil-structure interaction effects is developed using Laplace and Hankel transformation techniques. Utilizing these transformation techniques and normal mode theory of vibration, an N-mass structural model is coupled to an elastic half-space representing the earth. The resulting interaction equation is solved by numerical iteration techniques for a model of a nuclear power plant subjected to actual earthquake ground excitation. The effects of the soil-structure interaction are evaluated by comparing free-field acceleration spectrum response curves with similar curves determined from the foundation motion. These effects are found to be significant for structures typical of modern nuclear power plants subjected to seismic ground motions.

Forced Response Assessment Using Modal Force Based Indicator Functions

2008 ◽  
Author(s):  
M. Vahdati ◽  
C. Breard ◽  
G. Simpson ◽  
M. Imregun
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
Stokes Equations ◽  
Linear Time ◽  
Response Assessment ◽  
Element Model ◽  
Forced Response ◽  
Navier Stokes ◽  
Modal Force ◽  
Indicator Functions

This paper will focus on core-compressor forced response with the aim to develop two design criteria, the so-called chordwise cumulative modal force and heightwise cumulative force, to assess the potential severity of the vibration levels from the correlation between the unsteady pressure distribution on the blade’s surface and the structural modeshape. It is also possible to rank various blade designs since the proposed criterion is sensitive to changes in both unsteady aerodynamic loads and the vibration modeshapes. The proposed methodology was applied to a typical core-compressor forced response case for which measured data were available. The Reynolds-averaged Navier-Stokes equations were used to represent the flow in a non-linear time-accurate fashion on unstructured meshes of mixed elements. The structural model was based on a standard finite element representation from which the vibration modes were extracted. The blade flexibility was included in the model by coupling the finite element model to the unsteady flow model in a time-accurate fashion. A series of numerical experiments were conducted by altering the stator wake and using the proposed indicator functions to minimize the rotor response levels. It was shown that a fourfold response reduction was possible for a certain mode with only a minor modification of the blade.

Additional Damping Conditions Analysis and Calculation for Exciting Force and External Load

2013 ◽  
Vol 579-580 ◽  
pp. 507-511
Author(s):  
Yi Xiang Liu ◽  
Yong Mei Wang
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Structure Design ◽  
Exciting Force ◽  
Reduction Gear ◽  
Solid Model ◽  
Gear Noise ◽  
Force Reduction ◽  
And Control ◽  
The Impact

This paper firstly starting mechanism of vibration and noise from gear, gear noise mechanism is explained, and analyze the factors and the impact of noise on the gear reducer. Secondly, the establishment of a complete solid model of gear reducer and reducer model for finite element model, the reduction gear box gear reducer of modal analysis and finite element modal calculation, and points out the dynamic analysis of structure, size and weight factor is proportional to the reciprocal of the modal frequencies of each mode is the with the frequency is low, that is, the greater the weight. Once again, the main measure of load and control of gear noise of gear is analyzed, including the calculation, for exciting force reduction gear reducer gear load computation. The analysis and calculation are the theoretical basis of gear structure design and its performance evaluation.

Modelling of Piezoceramic Patches for Actuator Placement Strategies

2014 ◽  
Author(s):  
Michael Rose
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Structural Model ◽  
Electrical Coupling ◽  
Element Model ◽  
Dynamics Simulation ◽  
Tool Chain ◽  
Active Layers ◽  
Speed Up ◽  
Actuator Placement

Piezoceramic Patches are commonly used as actuator devices in smart structures if the induced forces are sufficient for the application. To model these devices in a structural dynamics simulation, a finite element model can be augmented by active layers. This needs a suitable element meshing, taking care of the actual shapes and positions of the active patches in use. If many different setups have to be evaluated, which is naturally the case for placement strategies for suitable actuator positions, this approach is quite cumbersome. To ease and speed up the augmentation of fixed finite element models with piezoceramic patches, so called modal correction methods have been successfully used in this context. These approximative methods avoid the remeshing and the reassembling of the underlying finite element model by adapting the modal description of the structural model with the mass, stiffness and electrical coupling effects of the applied patches. In this paper different aspects of this modelling approach are discussed especially for a tool chain to optimize patch locations in an ASAC simulation environment.

scholarly journals Estimation of leak rate through circumferential cracks in pipes in nuclear power plants

2015 ◽  
Vol 47 (3) ◽  
pp. 332-339 ◽  
Author(s):  
Jai Hak Park ◽  
Young Ki Cho ◽  
Sun Hye Kim ◽  
Jin Ho Lee
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Leak Rate

scholarly journals A Buckling Flexure-Based Force-Limiting Mechanism

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Jonathan Slocum ◽  
Kenneth Kamrin ◽  
Alexander Slocum
Keyword(s):  
Finite Element ◽  
Design Methodology ◽  
Structural Model ◽  
Cost Effective ◽  
Element Model ◽  
Single Shot ◽  
Excessive Force ◽  
Molding Machine ◽  
Preliminary Model ◽  
Wide Range

A force-limiting buckling flexure has been created which can be used in a wide range of applications where excessive force from an implement can cause harm or damage. The buckling flexure is monolithic, contains no electronics, and can be manufactured using a single shot in an injection molding machine, making it cost effective. In this paper, the design of the flexure is applied to a force-limiting toothbrush as a design study to show its application in a real-world technology. An overview of the buckling flexure is presented, and a structural model is presented to predict when the flexure will elastically buckle. Flexures of different geometries were tested and buckled. The data show that the model can predict buckling of the flexure with an error of 20.84%. A finite element model was also performed which predicts buckling of the flexure within an error of 25.35%. Furthermore, a preliminary model is presented which enables the design of the buckling beam’s displacement, such that the total breakaway deformation can be maximized, making sensing the sudden deformation easier to detect. As part of the application of the buckling flexure, an ergonomic, injection moldable toothbrush was created with the flexure built into the neck of the brush. When the user applies too much force while brushing, the flexure gives way and alerts the user when they have applied too much force; when the user lets off the force, the brush snaps back to its original shape. This design methodology is generalized and can be utilized in other force limited applications where an injection-moldable, pre-set force, and purely mechanical breakaway device is desired.

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