Evaluation of fracture resistance of ruptured,oxidized, and quenched Zircaloy cladding by four-point-bend tests

To evaluate fracture resistance of light water reactor fuel rods under loss-of-coolant accident (LOCA) and post-LOCA cooling conditions, four-point-bend tests were performed on non-irradiated Zircaloy cladding samples that were ruptured, oxidized in high-temperature steam, and quenched in flooding water. The bend test methodology was designed to apply a uniform bending moment to the entire rupture region and to generate tensile stress on the ruptured side. The fracture bending moment of the cladding decreased with oxidation temperature and hydrogen concentration as well as oxidation amount. Comparison with bending moments estimated from design basis seismic ground motion indicated that the cladding is unlikely to be fractured by seismic loads during post-LOCA cooling if high-temperature oxidation is kept below 15% equivalent cladding reacted, the oxidation limit of the Japanese LOCA criteria.     

A simple approach for failure bending moments of straight pipes

Based on more than 100 experimental results a simple approach for calculating the failure bending moment of a straight pipe is given. Similar to limit load theory a constant stress distribution is assumed over the cross section, whereas stress intensity is expressed by a function of pipe geometry and work-hardening capability of the material.     

Fatigue and fracture behavior of straight pipe with flaws in inner surface

Fatigue and fracture tests of piping models with flaws in the inner surface were carried out to investigate the fatigue crack growth, coalescence of multiple cracks and fracture behavior.Two straight test pipes with and without weldment in the test section of AISI type 304L stainless steel were tested under almost the same test conditions by imposing moment loads. Three artificial defects were machined in the inner surface of the test section of the test pipes and the fatigue test was performed until the cracks coalesced and grew through the thickness. Subsequently, a static load was imposed on the test pipe which contained a large crack in the test section.The fatigue test results are compared with an analytical crack growth behavior predicted by the method described in the Section XI of ASME Code, and show slower crack growth than that of the prediction. From the fracture test results, it is found that the test pipes can endure considerably high load.     

停棒子系统与控制棒组操作范围监测试验

本文叙述了反应堆保护系统停棒与汽轮机降功率子系统的系统功能、保护参数和秦山核电站控制棒组插入监测器的设计与参数选择,确定了控制棒提升上极限值和在不同工况下棒插入低位、低-低位整定值,并在热态零功率条件下加以验证。试验证明参数选择是合理的,为功率运行阶段提供了数据。     

Proposal of limit moment equation applicable to planar/non-planar flaw in wall thinned pipes under bending

In this paper, a limit bending moment equation applicable to all types of planar and non-planar flaws in wall-thinned straight pipes under bending was proposed. A system to rationally classify the planar/non-planar flaws in wall-thinned pipes was suggested based on experimental observations focused on the fracture mode. The results demonstrate the importance of distinguishing between axial and circumferential long flaws in wall-thinned pipes.     

Guidance of a Laser Beam Through an Axially Non-Uniform Plasma Channel in the Weakly Relativistic Limit

The guiding of a laser beam in a plasma channel formed by a short ionizing pulse is investigated in the weakly relativistic limit. The plasma channel formed is axially non-uniform due to self defocusing of the prepulse. When a second delayed laser pulse propagates through the plasma channel formed by the prepulse, the competition between refraction and diffraction results into alternate convergence and divergence of the guided beam. Second-order nonlinear differential equations for the beam width parameter of the prepulse and guided pulse are derived by moment theory approach. The effect of the guided pulse and prepulse intensities on the propagation of the guided laser pulse through the plasma channel formed by the prepulse is studied. Laser guidance up to several Rayleigh lengths is observed.     

适用于核电厂BEPU的高效全局敏感性分析方法开发及应用

最佳估算加不确定性（BEPU）分析是IAEA推荐用于核电厂事故安全分析的方法,该方法中一个关键步骤为评估输入参数对目标输出的影响大小,即定量敏感性分析。传统BEPU分析中常使用基于线性或单调假设的局部敏感性分析方法,其难以适用于复杂的核反应堆系统,而全局敏感性分析则由于计算成本过高而难以在实际工程中应用。本研究中针对矩独立全局敏感性分析方法开展了优化研究,使用高阶模型表示、高斯求积公式等方法降低矩独立敏感性度量的计算成本,得到了一种高效的敏感性分析方法。使用了多个例题对优化方法的可靠性进行了验证,并将其应用于LOFT（loss of fluid test）大破口事故的敏感性分析。结果表明,该高效敏感性分析方法能准确识别核反应堆事故工况中的重要参数,并能对参数重要度进行定量排序。     

Prediction of the Gas-Dynamic Source of Contamination during an Explosion at a Radiation-Hazardous Object

For predicting the radiation conditions after an explosion at a radiation-dangerous object, a method is proposed for determining the parameters of the medium contaminated with radioactive sources from the moment of the explosion up to the time when the motion of the cloud is determined primarily by the meteorological conditions. The formulation of the explosion problem takes account of the interaction of the gas with finely dispersed water particles, including mass, momentum, and energy transfer (due to phase transformations of the water), aerodynamic drag forces, and convective heat transfer. The problem is solved using the nonstationary method of large particles, modified by introducing a flow-correction step. The results of a test calculation of the 1957 explosion in the Southern Urals are presented. 4 figures, 5 references.     

The effect of internal pressure on in-plane collapse moment of elbows

Elastic–plastic finite element analysis has been carried out to evaluate collapse moments of six elbows with elbow factors varying from 0.24 to 0.6. Collapse moment is obtained by twice elastic slope method from the moment vs. end-rotation curve. The effect of internal pressure on in-plane closing/opening collapse moment is studied. For various elbow factors and level of internal pressure, total 60 and 54 cases are analysed for closing and opening mode of bending moment, respectively. Based on these results, two closed-form equations are proposed to evaluate the collapse moments of elbows under combined internal pressure and in-plane closing and opening bending moment.     

高梯度加速管的设计

叙述了双间隙高梯度加速管的设计，介绍了加速管的主要部件的作用和结构，井扼要说明和讨论了加速管的试验结果。     

Plastic limit load analysis for steam generator tubes with local wall-thinning

This paper introduces the study of experimental and numerical analysis for plastic limit loads of Inconel 690 steam generators (SG) tubes with local wall-thinning defects. Meanwhile, the effect of the three dimensions of a local wall-thinning defect on the plastic limit load of SG tubes is analyzed.A test facility which can test both burst pressure and plastic limit load of SG tubes was established and SG tubes with 3 typical types of defects were tested by using the facility. A regularization method for local wall-thinning defect is proposed and the finite element method was used to analyze the plastic limit load of SG tubes with defects. Compared with the experimental results of SG tubes with real defects, the calculated values of plastic limit load for SG tubes with regularized defects are conservative.Based on finite element method, the effect of the three dimensions of local wall-thinning defects on plastic limit loads of defected Inconel 690 SG tubes has been got. The studied results show that the defect depth of a local wall-thinning defect is the main factor influencing the plastic limit load of SG tubes, on the other hand, both the longitudinal length and the circumferential length of a defect have effect on the plastic limit load of SG tubes.It is found that in some cases, when the longitudinal length and the circumferential angle of a local wall-thinning defect exceed some extent, the effect of the longitudinal length and the circumferential angle on plastic limit load can be ignored.     

应急操作时人的失误因素

在应急操作下，人往往处于精神极限状态。此时，操作失误率极度升高，灾难性事故往往在此刻发生。本文以提高人－机系统可靠性为前题，阐述了极限状态下人的心理、病理变化和应急操作时的待业特点，并介绍了国外专家对人心理层次的划分。分析了造成人的极限状态的心理、生理、病理和机器设备等方面的影响因素，本文还以核动力学发电厂应急操作规程为例，重点研究了预防出现极限状态的对策，包括；环境影响对策，优化设备措施和操作者     

Stability of circumferential through-cracks in ductile pipes

An analysis of tearing instability is presented for a pipe with a circumferential through-crack. Loading conditions consisting of a large external axial force and a bending moment, together with an internal pressure, have been considered. The mechanical behavior of the material is assumed to be elastic perfectly-plastic. Instability has been studied under fixed grip conditions, following the application of loads which correspond to the plastic limit load of the cracked cross-section. The values of the applied tearing modulus have been expressed in terms of geometrical factors such as pipe length, pipe radius, and the length of the crack. Numerical examples have been calculated to obtain an estimate of the critical value of the length-to-radius ratio, for the case that the tearing modulus of the material is known.     

Nonlinear dynamic analysis of high energy line pipe whip

This paper describes a nonlinear dynamic analysis of TVA high energy line pipe whip tests using the ABAQUS-EPGEN code. The analysis considers the effects of large deformation and strain rate on resisting moment and energy absorption capability. The numerical results of impact forces, impact velocities, pipe strains, and reaction forces at pipe supports are compared to the TVA test data. The calculated pipe whip impact time and forces are also compared with those predicted using current industry practice.The calculated pipe support reaction forces are found to be in good agreement with the TVA test data except for some peak values at the very beginning of the pipe break. These peaks are believed to be due to stress wave propagation which cannot be addressed by the ABAQUS code. Both elbow crushing and strain rate have been approximately simulated. The effects are found to be important for pipe whip impact evaluation.     

Thermal flexure of an infinite plate with a doubly periodic array of holes

A theoretical method is presented for bending problems of perforated plates. The method is illustrated by giving the solution for an infinite plate with a doubly periodic set of circular holes having a square or triangular pattern under a uniform temperature difference between upper and lower faces of the plate within the framework of the Poisson-Kirchhoff theory of thin plates. Numerical results are given for the bending moment around holes and curves of stress concentration factors. The results show the power and flexibility of the technique. The solution obtained here can be used, just as it is, for a plate with holes of arbitrary shape and array. Also the extension of the method to a plate under a class of loads other than thermal load, e.g. uniform bending or twisting moment, is quite straightforward.     

从理论角度降低低本底α、β测量仪净计数率探测下限研究

本文从不等式角度推导了低本底α、β测量仪测量过程中净计数率探测下限的公式,并计算两种典型探测下限公式对应的犯第二类错误的实际概率值。在不做近似的情况下,一定时间发生原子核衰变的数目服从二项分布。当净计数率的平均值为探测下限这个值时,净计数率的随机数低于判断限的概率就是犯第二类错误的实际概率值。结合初始时刻的放射性原子核数目、整个测量时间发生了衰变的放射性原子核数、放射性原子核发生衰变的概率,可以计算犯第二类错误(产生误判)的实际概率值。通过计算,发现大多数情况下犯第二类错误的实际最大概率比标称概率值低1到2个量级。因此在保证犯第二类错误的实际概率值趋近并小于标称值的情况下,通过引入修正系数对探测下限进行了修正。通过计算发现,当k_α=1.645,k_β=1.645时,通过引入修正系数可以使探测下限至少降低22%。     

Collapse moment estimation by support vector machines for wall-thinned pipe bends and elbows

The collapse moment due to wall-thinned defects is estimated through support vector machines with parameters optimized by a genetic algorithm. The support vector regression models are developed and applied to numerical data obtained from the finite element analysis for wall-thinned defects in piping systems. The support vector regression models are optimized by using both the data sets (training data and optimization data) prepared for training and optimization, and its performance verification is performed by using another data set (test data) different from the training data and the optimization data. In this work, three support vector regression models are developed, respectively, for three data sets divided into the three classes of extrados, intrados, and crown defects, which is because they have different characteristics. The relative root mean square (RMS) errors of the estimated collapse moment are 0.2333% for the training data, 0.5229% for the optimization data and 0.5011% for the test data. It is known from this result that the support vector regression models are sufficiently accurate to be used in the integrity evaluation of wall-thinned pipe bends and elbows.     

Analysis of a bending test on a full-scale PWR hot leg elbow containing a surface crack

EDF, in co-operation with Framatome, has conducted a large research programme on the mechanical behaviour of thermally aged cast duplex stainless steel elbows, which are part of the main primary circuit of French PWRs. One important task of this programme consisted of testing a full-scale PWR hot leg elbow. The elbow contained a semi-elliptical circumferential notch machined on the outer surface of the intrados, as well as casting defects located on the flanks. To simulate the end-of-life condition of the component regarding material toughness, it had previously undergone a 2400-h ageing heat treatment at 400°C. The test preparation and execution, as well as the material characterization programme, were handled by MPA. The test was conducted under constant internal pressure and in-plane bending (opening mode) at 200°C. For safety reasons, it took place at an open air-site: the Meppen military test ground. At the maximum applied moment (6000 kN m), the notch did not initiate. This paper presents the results of the experiment and the results of the fracture mechanics analysis, based on finite element calculations.     

Elasto-plastic behavior of pipe subjected to steady axial load and cyclic bending

The elasto-plastic behavior of a pipe subjected to a steady axial force and a cyclic bending moment is studied. By using two parameters c and d, which describe the elasto-plastic interfaces of beam cross-section, the boundary curve equations between various types of elasto-plastic behavior, such as shakedown, plastic fatigue, ratcheting, and plastic collapse, are derived. The results are applicable for beams of any cross-section with two orthogonal axes of symmetry. As a result, the load regime diagram for a pipe is obtained, which gives an intuitive picture of the elasto-plastic behavior of the pipe under a given combination of constant axial load and cyclic bending moment.     

多源数据融合方法研究

选取工程应用中易于实现的数据融合方法进行分析研究,并以融合数据与数据真实值的偏差作为数据融合方法的稳定性判定依据,进行了三余度多源数据的数据融合仿真试验。试验结果表明,加权最小二乘法在数据融合时表现稳定,可替代常用的矩估计融合和中值融合,更有效地提高融合数据的精度。