New Trends in Accurate Simulations for the Verification of Safety Margins in the Nuclear Power Plant Industry: Application of Virtual Performance Solution™ for the Response of Immersed Structures Subjected to Earthquakes

2011 ◽  
Author(s):  
Alain Tramec¸on ◽  
Jorg Kuhnert ◽  
Laurent Mouchette ◽  
Morgane Perrin
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Dynamic Simulations ◽  
Finite Point ◽  
Fluid Structure ◽  
Finite Element Software ◽  
Mesh Free ◽  
Safety Margins ◽  
Non Linear

Constraints on the safety of nuclear power plant components have increased recently along with the necessity to extend the lifespan of existing plants. For example, the acceleration levels to be sustained by the plant equipment during an earthquake have been increased many folds by the safety regulation agencies. Industrial and economic requirements plead for a verification of unknown safety margins, by accurate and physics based models taking into account all non-linear effects (for example contacts and fluid structure interaction). These effects are only approximately represented by standard linear analysis tools. Virtual Performance Solution (VPS), developed by ESI Group, includes (among other capabilities) a structural finite element software for non-linear, high velocity, dynamic simulations (PAM-CRASH), as well as a coupled, mesh free CFD module, FPM (Finite Point Method), developed in partnership with Fraunhofer ITWM. This solution accurately predicts fluid structure interactions, taking into account non-linear structural effects (contacts, friction, damping…) as well as complex fluid influences.

Seismic Design Margin of the Piping and Support System: Part 3—Evaluation of Seismic Margin of the Piping System

2010 ◽  
Author(s):  
Eiji Shirai ◽  
Takanori Yamada ◽  
Kazutoyo Ikeda ◽  
Toshiaki Yoshii ◽  
Masami Kondo ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Support System ◽  
Earthquake Engineering ◽  
Nuclear Power ◽  
System Response ◽  
Piping System ◽  
Linear Modeling ◽  
Safety Margins ◽  
Non Linear

Seismic safety is one of the major key issues of nuclear power plant safety in Japan. It is demonstrated that nuclear piping possesses large safety margins through the piping and support system test, which consisted of three dimensional piping, supports, U-bolts, and concrete anchorages, using the E-defense vibration table of National Research Institute for Earth Science and Disaster Prevention, Hyogo Earthquake Engineering Research Center, on extremely high seismic excitation level [1,2,3]. In the above test, the non-linear hysteretic behaviors of the support are quite complicated, but the dissipated energies introduce large damping effects on the piping system response. In order to evaluate the inelastic behavior of the support with respect to the whole piping system response, the following simulation methodology for the support re-evaluation is proposed. 1) Non-linear modeling of the support: • Failure mode and failure capacity of each support. • Simplified non-linear modeling of each support. 2) Simulation Analysis of the piping and support system: • Considering the non-linearity both of the supports and elbows in the piping system. 3) Evaluation of seismic margin: • Focused on the failure level for the support system, and the fatigue damage for the strain range of the piping. The limit state analysis of the typical piping system of a nuclear power plant is presented in this paper, and it is demonstrated that these evaluations of the seismic margins would give important insight into the support reinforcement program on the seismic re-evaluation work.

Analysis and Assessment of Errors of Commission in Nuclear Power Plant Settings

2000 ◽  
Vol 44 (22) ◽  
pp. 851-854
Author(s):  
Oliver Straeter
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Maintenance Management ◽  
Pressure Injection ◽  
Safety Margins ◽  
Plant Maintenance ◽  
Complex Technical Systems ◽  
Technical Systems ◽  
High Pressure Injection

The term Errors of Commission (EOC) describes a safety problem of complex technical systems where humans intervene into the system functions in an inappropriate way. Most serious events in any technical area are caused by EOCs. Humans shut down a high pressure injection that is needed in the current situation (TMI Nuclear Power Plant), humans decide to continue a test that brings the plant into serious conditions (Chernobyl Nuclear Power Plant), Maintenance Management does not exchange a wheel that is far below the safety margins (Eschede Railway Accident in Germany). Similar examples can be mentioned in other technical systems like Aircraft or Medicine for instance. This paper firstly gives an overview about the problem and the work in that field. It then focuses on some approaches for solution concerning the modeling of cognitive human behaviour.

Review of Residual Stress Mitigation Methods for Application in Nuclear Power Plant

2006 ◽  
Author(s):  
P. R. Hurrell ◽  
D. Everett ◽  
A. Gregg ◽  
S. Bate
Keyword(s):  
Residual Stress ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Cost Savings ◽  
Surface Plastic ◽  
Significant Treatment ◽  
Thermal Transients ◽  
Safety Margins ◽  
Mitigation Methods

A research project has recently been launched in the UK investigating residual stress (RS) in nuclear power plant [1]. At the outset there is a need to review techniques available for modifying/relieving residual stress levels in weldments, since it is well known that large tensile RS levels generated in welds can be detrimental in terms of fatigue, fracture resistance and environmentally assisted cracking (EAC). Therefore current RS mitigation methods have been reviewed. Mitigation methods can be categorised into three main groups as follows: a) Surface treatment to induce compressive skin stress; b) Stress relief through thickness; c) Weld design optimisation to produce low/favourable RS levels and minimize distortion. A brief description is provided of how each method works, together with the capability and potential benefit in terms of RS reduction, as well as references for further information. Metallurgical effects of treatment are also an important consideration. The practicality of application to nuclear plant is considered, both in manufacture and in-service, together with any limitations and risks. Several techniques are identified that are likely to be beneficial and warrant funding for further development. RS mitigation should be targeted at key/critical weld locations in the plant, where loadings and degradation mechanisms (such as corrosion, fatigue, EAC or fracture) are most significant. Treatment would be carried out in order to improve plant integrity and reliability (eg safety margins). There are potentially substantial cost savings since through-life inspection/maintenance work could be reduced and expensive repairs and shutdowns avoided. Note that it is important to understand whether the benefits in terms of RS improvement are likely to be long term. In certain systems large thermal transients are applied that might generate additional surface plastic strains, thereby modifying RS magnitudes and distributions.

CNSC Review of Safety Improvements: CANDU Fuel Modification in Canada

2013 ◽  
Author(s):  
Yujun Guo
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Nuclear Safety ◽  
Nuclear Industry ◽  
Fuel Bundle ◽  
Safety Margins ◽  
Fuel Design

Aging of a CANDU nuclear power plant affects various safety margins of the plant. Margin to fuel sheath dryout is one of the safety margins that have been detrimentally affected, leading to a reduced margin to dryout with time. If no proactive actions are taken, the plant will have to de-rate its operation at an earlier time. To postpone the de-rating, the Canadian nuclear Industry has taken multi-initiatives to restore, or partially restore the safety margins that have been eroded due to plant aging. One of the initiatives is modification/re-optimization of the current fuel design, in order to improve the fuel thermalhydraulic performance, i.e., to suppress fuel sheath dryout, whereby offset partially the erosion of margin to fuel sheath dryout. In response to the initiative of fuel bundle modification, the Canadian Nuclear Safety Commission (CNSC) — the nuclear safety regulator — has set clear requirements and expectations and followed rigours processes and procedures for reviewing and licensing the modified fuel. This paper summarizes the fuel modification program in Canada, and the CNSC requirements, expectations, and review processes associated with licensing review of fuel modifications in Canada.

scholarly journals Dynamic behaviour of nuclear island structure of AP1000 under El Centro and Dien Bien earthquakes

2021 ◽  
Vol 7 (4) ◽  
pp. 34-41
Author(s):  
Lam Dong Vu Lam ◽  
Ngoc Dong Pham ◽  
Dinh Kien Nguyen ◽  
Dai Minh Nguyen ◽  
Tien Thinh Do
Keyword(s):  
Finite Element ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Dynamic Response ◽  
Dynamic Behavior ◽  
Nuclear Power ◽  
Seismic Analysis ◽  
Element Model ◽  
Island Structure ◽  
Finite Element Software

AP1000 is a nuclear power plant developed by Westinghouse based on an advanced passive safety feature, and it is one of selected technologies for Ninh Thuan 2 Nuclear Power Plant. The dynamic behavior of the plant under earthquakes is the most concerned in design and construction of the plant. This paper presents a seismic analysis of the AP1000 nuclear island structure by using the computational finite element software ANSYS. A 3D finite element model for the structure is developed and its dynamic response, including the time histories for displacements, velocities andaccelerations, deformed configurations and von Mises stresses of the structure are obtained for America El Centro (6.9 Richter) and Vietnam Dien Bien (5.3 Richter) earthquakes. A comparison on the dynamic response of the structure under the two earthquakes is given, and the dynamic behavior of the structure under the earthquakes is discussed.

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