The probability of formation and detection of large flaws in welds

This paper reviews recent data that have come available on flaws in nuclear components. It examines whether the conclusions in a previous paper [Bullough R, et al. The probability of “large” defects in thick section butt welds in nuclear components. Int J Pressure Vessels Piping 2001; 78: 553–65] still hold in the light of this new information.

A new model for estimating the distribution of flaws greater than 15 mm in through-wall extent for submerged arc welds is also reviewed. In this model, four potential flaw formation mechanisms are considered: (i) lack of fusion, (ii) weld metal solidification cracking, (iii) hydrogen-induced cracking in the heat-affected zone, and (iv) hydrogen-induced cracking in the weld metal. The distribution of large flaws remaining after pre-service inspection is calculated for each mechanism as the product of the probability of forming the flaw and the probability of the flaw being undetected during pre-service radiography. The assumptions and general applicability of the model are discussed.     

Italian developments in the ultrasonic examination of pressure vessels

A review of developments being pursued in Italy in ultrasonics for application to pressure vessels is presented.

Although nuclear construction in Italy has suffered heavy delays, R & D activities promoted by the Italian Electricity Board in the mid 1970s on advanced UT for non-destructive inspection of thick welded sections made it possible to obtain significant results scored by CISE Laboratories, mainly through the design, construction and qualification of the manual UT spectroscopy and signal processing computerized ARICE system and of the mechanized multifrequency acoustic holography HADIS system. Meanwhile theoretical ultrasonic modelling is actively studied in order to implement software applications and the overall reliability of UT inspections with regard to flaw detection, location and sizing.

Selected contributions from manufacturers and service companies with a view to improving UT practice are acknowledged, and still wider technology transfers may be expected in the future, also under ENEA industrial promotion programmes.     

A review and further analysis of the results of the defect detection trials

The Defect Detection Trials were initiated in the post-PISC I era when it was considered essential to determine under controlled conditions the capability of selected ultrasonic techniques to detect and size significant flaws. These trials were not intended to allow a statistical evaluation of either the capability or reliability of a particular team or technique since the number of tests had to be limited. However, useful conclusions relating to the effectiveness of specific ultrasonic techniques under the conditions relevant to the DDT can be drawn, and some guidance can be gained on factors which influence the reliability of inspection.

The analysis first considers defect detection and concludes that very high standards were achieved, with all the flaws being reported for DDT Plates 1 and 2 by all the teams. Secondly, the fraction of referable flaws which are correctly classified according to specified criteria is evaluated. In some cases the margin between classifying a flaw as acceptable or referable is extremely small, and tolerances on the sizing data are considered and causes of misclassification are assessed.

The contribution made by the tandem and pulse-echo techniques and the degree of redundancy in the detection data are reviewed.     

围堰施工导流风险率不确定性分析研究

施工导流风险评价是导流工程设计的重要依据,应综合考虑水文、水力等方面的不确定性影响。针对传统导流风险计算仅考虑不确定性因素的单一概率分布并固定分布参数值、忽略了分布及参数的不确定性的问题,基于对多元不确定性因素的Monte-Carlo仿真,综合考虑导流系统中水文和水力因素的分布和分布参数的不确定性,深入分析了导流系统风险率的不确定性。结果表明,水文与水力因素的参数不确定性对导流风险率的计算有较大影响,考虑水文与水力参数不确定性计算所得的导流风险率服从正态分布。     

A new general approach for the fracture of pressurized components with an oblique flaw and its experimental verification

A key element in the safe use of flawed components is that of developing an accurate method for predicting failure under operational conditions. In this paper a new general approach to the fracture of pressurized components with an oblique flaw is proposed. It can be used for predicting the failure load under operating conditions of a component containing surface flaws and/or through-wall oblique flaws, the relevant component being made of ductile structural steel. Experiments on eight pressure vessel models with an oblique through-wall flaw and four with an oblique surface flaw have been performed to support this approach.The approach proposed is in good agreement not only with the results of the experiments mentioned above but also with tests made at other research units in China. For the specific case of a flaw located in the axial direction, it has been supported by many tests in China and other countries.     

An integrated systematic analysis of uncertainties in UK energy transition pathways

Policy goals to transition national energy systems to meet decarbonisation and security goals must contend with multiple overlapping uncertainties. These uncertainties are pervasive through the complex nature of the system, the long term consequences of decisions, and in the models and analytical approaches used. These greatly increase the challenges of informing robust decision making. Energy system studies have tended not to address uncertainty in a systematic manner, relying on simple scenario or sensitivity analysis. This paper utilises an innovative UK energy system model, ESME, which characterises multiple uncertainties via probability distributions and propagates these uncertainties to explore trade-offs in cost effective energy transition scenarios. A linked global sensitivity analysis is used to explore the uncertainties that have most impact on the transition. The analysis highlights the strong impact of uncertainty on delivering the required emission reductions, and the need for an appropriate carbon price. Biomass availability, gas prices and nuclear capital costs emerge as critical uncertainties in delivering emission reductions. Further developing this approach for policy requires an iterative process to ensure a complete understanding and representation of different uncertainties in meeting mitigation policy objectives.     

Allowable sizes of axial flaws in pressurized pipes made of moderate toughness materials

Failure stresses for axially part-through flawed pipes made of moderately tough materials are predicted by several fracture mechanics. However, allowable flaw sizes using these fracture mechanics cannot be simply described because there are many effective parameters such as pipe diameter, wall thickness, material properties, etc. To establish codes and standards to evaluate flaws for piping of light water reactors, we determine unified allowable sizes for axial flaws in pipes subjected to internal pressure from J-integral based fracture mechanics. The allowable sizes are simply tabulated using a single parameter which consists of pipe geometry and material properties.     

承压设备焊缝超声相控阵检测图谱解读

国际权威法规ASME最新版（2015）给出了承压设备焊缝超声相控阵检测（PAUT）图像解读、分析、评断的典型示例。主要内容：图像彩色与波幅强度的相关性，缺陷信号测长测高方法，读谱准备，常用显示型式，面型体型缺陷典型图谱。触类旁通，融会贯通，可为国内制定相应工业PAUT评定标准，提供有用借鉴。     

Development of an interval multi‐stage stochastic programming model for regional energy systems planning and GHG emission control under uncertainty

A regional energy system consists of diverse forms of energy. Energy‐related issues such as utilization of renewable energy and reduction of greenhouse gas (GHG) emission are confronting decision makers. Meanwhile, various uncertainties and dynamics of the energy system are posing difficulties for the energy system planning, especially for those under multiple stages. In this study, an interval multi‐stage stochastic programming regional energy systems planning model (IMSP‐REM) was developed to support regional energy systems management and GHG control under uncertainty. The IMSP‐REM is a hybrid methodology of inexact optimization and multi‐stage stochastic programming. Not only can it handle uncertainties presented as intervals and probability density functions but also reflect dynamics of system conditions over multiple planning stages. The developed IMSP‐REM was applied to a hypothetical regional energy system. The results indicate that the IMSP‐REM can effectively reflect issues of GHG reduction and renewable energy utilization within an energy system planning framework. In addition, the model has advantages in incorporating multiple uncertainties and dynamics within energy management systems. Copyright © 2011 John Wiley & Sons, Ltd.     

含概率与区间混合不确定性的重力坝可靠性分析

针对重力坝可靠度分析中由于数据缺乏或监测条件限制难以得到各变量精确的概率分布的情况,提出了含概率与区间混合不确定性的结构可靠性分析方法,对于可得到精确概率分布的变量用随机变量进行考虑,对于无精确概率分布的变量用区间表示,并结合响应面法计算了广西红水河龙滩重力坝坝踵抗拉可靠度。结果表明,该方法只需少量的不确定信息就可对结构进行可靠性分析,更适合结构复杂、不确定性较高的水工建筑物结构。     

A method for remaining discharge time prediction of lithium‐ion batteries under dynamic uncertainty

Remaining discharge time of the battery system in electric vehicles relates strongly to the decision‐making of driving. Subjected to the various uncertainties, such as modeling uncertainty, state estimation uncertainty, and future load uncertainty, the accuracy and reliability of the remaining discharge time prediction reduce, which will lead to range anxiety. A stochastic framework based on the state‐of‐charge estimation and prediction strategy is proposed to predict remaining discharge time against the uncertainty. Firstly, the equivalent circuit model is established to model the dynamic behavior of the battery. Through the analysis of different fitting functions of open circuit voltage and state‐of‐charge, the Akaike information criterion is introduced to select the best function. Secondly, the coestimator is employed to bound the influence of the model parameter uncertainty and noise uncertainty. Finally, the uncertainties are quantified by a probabilistic method, and a Monte Carlo–based stochastic prediction strategy is proposed to predict the probability distribution of remaining discharge time under dynamic uncertainty. Experimental results demonstrate that the proposed prediction framework is of great effectiveness as it can provide an accurate remaining discharge time interval under dynamic uncertainty, which helps to promote the energy‐saving driving and overcome the range anxiety.     

The influence of perceived uncertainty on entrepreneurial action in emerging renewable energy technology; biomass gasification projects in the Netherlands

Emerging renewable energy technologies cannot break through without the involvement of entrepreneurs who dare to take action amidst uncertainty. The uncertainties that the entrepreneurs involved perceive will greatly affect their innovation decisions and can prevent them from engaging in innovation projects aimed at developing and implementing emerging renewable energy technologies. This article analyzes how perceived uncertainties and motivation influence an entrepreneur's decision to act, using empirical data on biomass gasification projects in the Netherlands. Our empirical results show that technological, political and resource uncertainty are the most dominant sources of perceived uncertainty influencing entrepreneurial decision-making. By performing a dynamic analysis, we furthermore demonstrate that perceived uncertainties and motivation are not stable, but evolve over time. We identify critical factors in the project's internal and external environment which influence these changes in perceived uncertainties and motivation, and describe how various interactions between the different variables in the conceptual model (internal and external factors, perceived uncertainty, motivation and previous actions of the entrepreneurs) positively or negatively influence the decision of entrepreneurs to continue entrepreneurial action. We discuss how policymakers can use these insights for stimulating the development and diffusion of emerging renewable energy technologies.     

Overview of JSME flaw evaluation code for nuclear power plants

A Japanese flaw evaluation code for nuclear power plant components has been developed at the Japan Society of Mechanical Engineers (JSME). The code prescribes methods for the evaluation of flaws, which are detected during inservice inspection for pressure vessels and pipes in nuclear power plants. This paper describes the basic flow chart, methods of evaluation and allowable flaw sizes for acceptance standards and criteria, including comparisons with the ASME Code Section XI.     

a－Si：H薄膜的表面缺陷研究

ａ－Ｓｉ：Ｈ薄膜的缺陷会给以该材料制作的半导体器件，如太阳电池、激光唱盘、光导鼓、ＴＦＴ等造成疵点，降低器件的质量和成品率；而对微波功率器件，这些缺陷则是致命的危害。本文讨论表面上由细微颗粒造成的各种缺陷。揭示这些缺陷的微结构形貌，对其形成的原因进行理论分析，并就如何消除这些缺陷，制备光洁如镜的ａ－Ｓｉ：Ｈ薄膜进行讨论。     

承压设备NDE新通道——ASME对超声TOFD技术的应用规定 第二部分：焊缝TOFD检测的基本要求

概述ASME有关TOFD检测缺陷测深定高校验演示的要领，包括校验试块的型式、系统校验的要点、定量原理和定量评价，以及误差分析等，旨在控制焊接缺陷超声检测定量精确度，为工程应用提供高可靠数据。     

Methodology for the pressurized thermal shock evaluation: recent improvements in French RPV PTS assessment

An extensive work was conducted in France related to the structural integrity re-assessment of the French 900 and 1300 MW reactor pressure vessels in order to increase their lifetime. Within the framework of this programme, numerous developments have been implemented related to the methodology used for the assessment of flaws during a pressurized thermal shock (PTS) event. This extensive work includes the development of new simplified approaches, with their validations by two-dimensional (2D) and three-dimensional (3D) finite element computations, the development of 3D elastic and elastic–plastic analyses, and finally the evaluation of the influence of the stainless steel cladding in a PTS analysis.A new simplified methodology — based on an elastic approach including a specific plasticity correction (β correction) taking into account the cladding yielded during a severe PTS transient — has been developed for the assessment of shallow subclad flaws, derived from 2D elastic and elastic–plastic computations. This new approach is described and compared to results obtained by reference 2D and 3D finite element elastic and elastic–plastic computations. This methodology is validated with reasonable margins and a sufficient level of accuracy.A similar work has been conducted related to the assessment of embedded shallow flaws located in the first layer of the stainless steel cladding. A new approach has been proposed, more realistic and less conservative than the methodology previously used for this kind of flaw.These two methodologies have been accepted by the French Safety Authority and are now used in the RPV structural integrity assessment in progress.Some 3D finite element analyses have been also performed in order to study the behaviour of several cracks (shallow subclad flaws and through-clad surface cracks) in a French RPV during a severe overcooling transient. Several through-clad surface cracks have been compared to shallow subclad flaws located at the cladding–base metal interface, and the influence of cladding in a PTS has been evaluated. The main results are presented. A RPV structural integrity assessment based on through-clad surface cracks appears much more severe than the specific French approach based on more realistic shallow subclad flaws. The influence of the cladding is particularly significant on the margins, regarding the risk of cleavage initiation along the crack front in the base metal of the vessel, by significantly decreasing the level of the stress intensity factor and consequently increasing the maximum allowable end-of-life RT_NDT.     

Failure probability of nuclear piping due to IGSCC

A simple model for the estimation of the pipe break probability due to IGSCC is developed and discussed. It is partly based on analytical procedures, partly on service experiences from the Swedish BWR program. Some rough estimates of the resulting break probabilities indicate that further studies are urgently needed. A sensitivity study is performed and it is found that the uncertainties about the initial crack configuration are the most important contributors to the total uncertainty. The results of inservice inspection are studied and it is found that the inspection intervals need to be shortened if a significant reduction in the failure probabilities is to be obtained.     

An interval-fuzzy two-stage stochastic programming model for planning carbon dioxide trading under uncertainty

In this study, an IFTSP (interval-fuzzy two-stage stochastic programming) method is developed for planning carbon dioxide (CO₂) emission trading under uncertainty. The developed IFTSP incorporates techniques of interval fuzzy linear programming and two-stage stochastic programming within a general optimization framework, which can effectively tackle uncertainties described in terms of probability density functions, fuzzy membership functions and discrete intervals. The IFTSP cannot only tackle uncertainties expressed as probabilistic distributions and discrete intervals, but also provide an effective linkage between the pre-regulated CO₂ mitigation policies and the associated economic implications. The developed model is applied to a case study of CO₂-emission trading planning of industry systems under uncertainty, where three trading schemes are considered based on different trading participants. The results indicate that reasonable solutions have been generated. They are help for supporting: (a) formulation of desired GHG (greenhouse gas) mitigation policies under various economic and system-reliability constraints, (b) selection of the desired CO₂-emission trading pattern, and (c) in-depth analysis of tradeoffs among system benefit, satisfaction degree, and CO₂ mitigation under multiple uncertainties.