Questions on safety margins of components at loads beyond design — failure modes of the primary system of PWRs

1990 ◽  
Vol 124 (1-2) ◽  
pp. 143-152
Author(s):  
H. Schulz ◽  
P. Gruner
Keyword(s):  
Failure Modes ◽  
Primary System ◽  
Safety Margins

Code Compliance of a New Metallic Composite Pipeline

2010 ◽  
Author(s):  
Colin McKinnon ◽  
David J. Miles ◽  
Raymond N. Burke
Keyword(s):  
Failure Modes ◽  
Continuous Process ◽  
High Strength ◽  
Specific Reference ◽  
Thin Wall ◽  
Metal Composite ◽  
Metallic Composite ◽  
Safety Margins ◽  
Composite Pipe ◽  
Qualification Testing

The composite pipe system, known as XPipe™, is a steel strip laminate technology which uses high-performance adhesives to manufacture a metallic composite pipe. It offers a new method of low cost pipeline construction suitable for onshore gas and oil pipelines in a variety of configurations. The pipe is based on a thin wall liner that provides the fluid containment, the material of which will vary according to service requirements. Fusion bonded epoxy (FBE) coated martensitic ultra-high strength steel strips are then pre-formed and helically wound around the liner to form a laminated high strength reinforcing layer providing the pipe’s hoop strength. These are bonded using an adhesive. Unlike conventional linepipe that is manufactured in a pipe mill away from the construction site, this lightweight composite pipe can be produced at the construction facility using a portable manufacturing line. All components of the manufacturing process fit within standard ISO containers, each weighing between 5 and 15 tonnes. This allows for easy transportation via truck, and handling or shipping. Existing regulations and codes make no specific reference to metal composite pipes. They are mainly written for steel pipe lines with some mention of plastic pipe. The paper presents a comprehensive review of the following US onshore design codes (ASME B31.4/B31.8) and relevant regulations (CFR (DOT) 49 P192 / P195) in order to establish the applicability of these codes for use on XPipe. The paper describes how XPipe meets the code and regulation requirements with regard to safety, design, material, construction, inspection, testing, operation and maintenance. The paper will identify any areas where XPipe does not meet code and regulation requirements and describe the testing and /or design changes that have been made in order to meet the code requirements. The paper will focus on the how the XPipe can meet the practical requirements of these codes. The paper will describe how the qualification testing is being performed in accordance with DNV-RP-A203 Qualification Procedures for New Technology. The qualification testing focuses on how the XPipe meets or exceeds pipeline safety margins with regard to typical failure modes such as yield, burst, facture, fatigue, collapse, etc. This is a continuous process and is being updated after each step using the available knowledge on the status of the qualification.

Piping Stress-Strain Correlation for Seismic Loading

1988 ◽  
Vol 110 (4) ◽  
pp. 444-450
Author(s):  
G. Stawniczy ◽  
W. R. Bak ◽  
G. Hau
Keyword(s):  
Pressure Vessel ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Seismic Loading ◽  
Evaluation Procedure ◽  
Test Results ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Safety Margins ◽  
Fatigue Evaluation

This paper establishes limits on piping material strains for ASME Boiler and Pressure Vessel Code Level D loadings that ensure a limitation of deformation and provide suitable safety margins. In establishing the strain limits, potential piping failure modes due to compressive wrinkling and low-cycle fatigue are considered. A stress-strain correlation methodology to convert linear, elastically calculated Code Class 2 and 3 equation (9)-Level D stresses to strains is established. This correlation is based on the fatigue evaluation procedure of the Code and is verified by comparison with test results. A detailed discussion of test results compared with the stress-strain correlation methodology is also presented.

An Estimation Method for First Excursion Probability of Nonlinear System Using Maximum Response

2004 ◽  
Author(s):  
Shigeru Aoki
Keyword(s):  
Failure Modes ◽  
Damping Ratio ◽  
Estimation Method ◽  
Maximum Response ◽  
Estimation Methods ◽  
Mechanical Equipment ◽  
Primary System ◽  
Secondary System ◽  
Restoring Force ◽  
Excursion Probability

The secondary system such as pipings, tanks and other mechanical equipment are installed in the primary system such as building. The important secondary systems should be designed to maintain their function even if they are subjected to destructive earthquake excitations. First excursion failure is one of the most important failure modes. The secondary system has many nonlinear characteristics. In this paper, an estimation methods of the first excursion probability of the secondary system with gap and friction subjected to earthquake excitation is proposed. Restoring force with gap and friction force is equivalently linearized. When the tolerance level is normalized by the maximum response of the secondary system without gap and friction characteristics, variation of the first excursion probability is very small for various values of mass ratio of the secondary system to the primary system, the damping ratio and the natural period.

Preliminary Large Break LOCA and SGTR Accident Analysis of the Compact Small Reactor

2017 ◽  
Author(s):  
Mian Xing ◽  
Linsen Li ◽  
Feng Shen ◽  
Xiao Hu ◽  
Zhan Liu ◽  
...  
Keyword(s):  
Cooling System ◽  
Thermal Power ◽  
Reactor Core ◽  
Safety System ◽  
Passive Safety ◽  
Primary System ◽  
The Core ◽  
Passive Safety System ◽  
Safety Margins ◽  
Guideline Values

This paper gives a brief introduction of the Compact Small Reactor (CSR). It is a simplified two-loop reactor with thermal power of 660MW and with compact primary system and passive safety feature. Preliminary safety analysis of the CSR is conducted to evaluate and further optimize the design of passive safety system, especially the passive core cooling system. Large Break Loss Of Coolant Accident (LBLOCA) and Steam Generator Tube Rupture (SGTR) are selected as two reference accidental scenarios. Each scenario is modeled and computed by RELAP5/MOD3.4. For the LBLOCA analysis, a guillotine break happens in the cold leg of the loop containing the core makeup tanks balance lines. The results show certain safety margins from the guideline values, and the passive safety system could supply enough cooling of the core. For the SGTR analysis, the results show the robustness of the design from the safety perspective. It is concluded that the safety systems are capable of mitigating the accidents and protecting the reactor core from severe damage.

Condition Management of HP/HT Pipelines: A New Approach

2008 ◽  
Author(s):  
Hroar Nes ◽  
Birger Etterdal ◽  
Stian Svardal
Keyword(s):  
Survey Data ◽  
Failure Modes ◽  
Hot Spot ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Design Criteria ◽  
Integrity Assessment ◽  
Safety Margins ◽  
Wide Range ◽  
Relative Utilization

StatoilHydro operates a large number of High Pressure/High Temperature (HP/HT) pipeline systems in the Norwegian Sea. These lines connect remote subsea templates to floating processing and storage units. Flowlines are designed for a maximum temperature up to 155 °C and a pressure in the range of 390–500 bar. Design pressure for injection lines are in general 500 bar. In addition to high operating loads, the infield lines are exposed to challenging seabed conditions and a potential for interference with on-bottom trawl gear. The objective of this paper is to present the principles and the methodology used for integrity assessment of the HP/HT lines, which provides the basis for specification of optimum maintenance requirements. The risk of integrity failure, associated with any hot-spot location, is consistently estimated based on safety margins predicted for the actual design criterion and as a function of the pre-defined Safety Class. The developed methodology assumes that the pipeline configuration and associated response parameters are accurately determined for relevant operating conditions. This requires finite element models that are calibrated according to survey data and corresponding operating parameters. A cyclic load history is applied to the post-buckled pipeline model in order to simulate actual operating conditions. Design criteria for relevant degradation and failure modes are established for a wide range of operating configurations and conditions. These criteria are used both to identify potential hot-spots and to estimate the relative utilization. The relative utilization may be estimated for an extreme single event, i.e. a design condition, or due to long term degradation. The risk of integrity failure is then determined as a function of the Safety Class and the relative utilisation, expressing the consequences and the probability of failure, respectively. A risk matrix, configured according to design safety principles, determines the risk of integrity failure. A software interface has been developed to compare and to visualize pipeline simulation results, survey data and corresponding design criteria. This information is used for documentation of the pipeline operating condition, and finally, for specification and follow-up of maintenance measures. The new integrity assessment methodology has been implemented as part of the condition management system for more than 30 HP/HT pipelines operated by StatoilHydro.

Structural Analysis Approach for Risk Assessment Under BDBE

2016 ◽  
Author(s):  
Naoto Kasahara ◽  
Izumi Nakamura ◽  
Hideo Machida ◽  
Koji Okamoto ◽  
Takuya Sato
Keyword(s):  
Risk Assessment ◽  
Structural Analysis ◽  
Failure Modes ◽  
The Other ◽  
Analysis Approach ◽  
Inelastic Analysis ◽  
Design Basis ◽  
Other Hand ◽  
Safety Margins ◽  
Defense In Depth

Based on the lessons learned from the Fukushima nuclear power plant accident, it is recognized the importance of the risk assessment and mitigation for failure consequences to avoid catastrophic failure of pressure equipment during severe accidents (SA) and excessive earthquake. The objectives of structural design (from the first layer to the third layer of the defense-in-depth) is strength confirmation under assumed loading conditions. On the other hand, ones of risk assessment and mitigation (the forth layer of the defense-in-depth) is prediction of realistic failure scenarios. Through investigation of failure locations and modes of main components under both severe accident and excessive earthquake, different failure modes from DBE(Design Basis Events) were identified for BDBE(Beyond Design Basis Events). To clarify these modes, the failure mechanisms were studied with some strength experiments. For most of failure modes, their dominant parameters are inelastic strain rather than stress. So that large scale inelastic analysis methods were studied and extended to very high temperature and large strain. By using above results, this paper has proposed the new structural analysis approach for risk assessment under BDBE. This is the extension of “design by analysis” concept. However it is clearly different from design approach from next viewpoints. (1) Additional failure modes to design condition Such additional failure modes induced by excessive loadings are considered for as local failure, creep rupture, creep buckling, ratcheting collapse and so on. (2) Identification of dominant failure modes Design codes require conservative evaluation against all of assumed failure modes. On the other hand, risk assessment needs adequate failure scenarios, where failure locations, modes and their order are important. For that reason, dominant failure modes have to be identified. To identify dominant modes, failure mode map concept was proposed. (3) Best estimation To estimate realistic accident phenomena, the best estimation is required. Therefore, dominant strength parameters and criteria without safety margins should be adopted. Through strength mechanism investigations, plastic and creep strain are recognized as more dominant parameters than stress for many failure modes. So that realistic inelastic analyses are recommended for BDBE.

Evaluation of Limit Load Analysis Methods Applied to High Temperature Design: Part 1 — Consistent Material Modeling

2014 ◽  
Author(s):  
Dave Dewees ◽  
Rahul Jain
Keyword(s):  
Elevated Temperature ◽  
Failure Modes ◽  
Limit Load ◽  
Material Model ◽  
Element Analysis ◽  
Allowable Stresses ◽  
Safety Margins ◽  
Advanced Analysis ◽  
Load Analysis ◽  
Pressure Part

Design-by-Rule codes (i.e. ASME Section I, EN 12952) already exist for elevated temperature (creep) design and have been successfully used for decades; however, there is motivation to optimize designs, or to assess non-standard ones. Limit Load Analysis (LLA) is the simplest advanced analysis method, and a powerful and widely-used tool for establishing compliance with required pressure part safety margins for operation at temperatures below the creep range. However, there is no direct relationship between LLA and elevated temperature allowable stresses and failure modes, such that the basic LLA methods or results must be manipulated in some way to be generally meaningful. With this in mind, review of proposed elevated temperature LLA methods (which are discussed in Part 2 of this work) by comparison to detailed transient inelastic finite element analysis allows for rigorous assessment of simplifications. Specification of an elevated temperature material model that is consistent with traditional allowable stresses for the detailed analysis is described in this paper (Part 1), and the material model and simplified methods are applied to the case of a typical steam header in the next (Part 2). Paper published with permission.

Scanning Electron Microscopy in Hybrid Microelectronics

1976 ◽  
Vol 34 ◽  
pp. 456-457
Author(s):  
S. Khadpe ◽  
R. Faryniak
Keyword(s):  
Integrated Circuits ◽  
Thick Film ◽  
Integrated Circuit ◽  
Failure Modes ◽  
Three Dimensional ◽  
Circuit Components ◽  
Hybrid Microcircuit ◽  
Electrical Connections ◽  
Scanning Electron

The Scanning Electron Microscope (SEM) is an important tool in Thick Film Hybrid Microcircuits Manufacturing because of its large depth of focus and three dimensional capability. This paper discusses some of the important areas in which the SEM is used to monitor process control and component failure modes during the various stages of manufacture of a typical hybrid microcircuit.Figure 1 shows a thick film hybrid microcircuit used in a Motorola Paging Receiver. The circuit consists of thick film resistors and conductors screened and fired on a ceramic (aluminum oxide) substrate. Two integrated circuit dice are bonded to the conductors by means of conductive epoxy and electrical connections from each integrated circuit to the substrate are made by ultrasonically bonding 1 mil aluminum wires from the die pads to appropriate conductor pads on the substrate. In addition to the integrated circuits and the resistors, the circuit includes seven chip capacitors soldered onto the substrate. Some of the important considerations involved in the selection and reliability aspects of the hybrid circuit components are: (a) the quality of the substrate; (b) the surface structure of the thick film conductors; (c) the metallization characteristics of the integrated circuit; and (d) the quality of the wire bond interconnections.

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