Xenon poisoning calculation code for miniature neutron source reactor（MNSR）

In line with the actual requirents and based upon the specific characteristics of MNSR,a revised point-reactor model was adopted to model MNSR‘s xenon poisoning.The corresponding calculation code.MNSRXPCC(Xenon Poisoning Calculation Code for MNSR),was developed and tested by the Shanghai MNSR data.     

Loss of flow accident and its mitigation measures for nuclear systems with SCWR-M

Based on a revised version of RELAP5, which can be used for super-critical pressure calculation, a model of mixed spectrum SCWR (SCWR-M) system is established. To analyze the transient behavior of SCWR-M and develop mitigation measures during loss of flow accident (LOFA), some important parameters, e.g. reactor coolant pump (RCP) coast-down time, Reactor Pressure Vessel (RPV) upper water volume and safety injection flow, etc., are chosen for the parametric analysis. The results achieved so far indicate that the SCWR-M system design is feasible and promising. Three important mitigation measures for LOFA of SCWR-M are derived from the results: RCP coast-down time of more than 15 s, RPV upper water volume of more than 27 m³, and safety injection of more than 5% of the system design flow.     

自然循环临界热流密度实验研究

本文介绍高压自然循环临界热流密度(CHF)实验研究。结果表明,对于稳定流动,自然循环与强迫循环CHF值几乎没有差別;不稳定流动将导致CHF降低。文中还给出了自然循环CHF工况预算模型。     

Yucca Mountain engineered barrier system corrosion model (EBSCOM)

A revised engineered barrier system model has been developed by the Electric Power Research Institute to predict the time dependence of the failure of the drip shields and waste packages in the proposed Yucca Mountain repository. The revised model is based on new information on various corrosion processes developed by the US Department of Energy and others and for a 20-mm-thick waste package design with a double closure lid system. As with earlier versions of the corrosion model, the new EBSCOM code produces a best-estimate of the failure times of the various barriers. The model predicts that only 15% of waste packages will fail within a period of 1 million years. The times for the first corrosion failures are 40,000 years, 336,000 years, and 375,000 years for the drip shield, waste package, and combination of drip shield and the associated waste package, respectively.     

混合能谱超临界水堆失流事故缓解措施研究

使用改进的系统程序RELAP5建立了一个混合能谱超临界水堆(SCWR-M)模型。为研究混合能谱超临界水堆失流事故特性,以获取缓解混合能谱超临界水堆失流事故的措施,选取反应堆冷却剂泵惰转时间、压力容器上部储水空间容积和安注流量作为主要参数进行分析。研究表明,混合能谱超临界水堆系统的设计是可行的。反应堆冷却剂泵惰转15 s,压力容器上部水空间容积大于27 m³,以及安注流量高于系统满功率稳态流量的5%是缓解混合能谱超临界水堆失流事故的主要措施。     

Theoretical model and experimental investigation of optically triggered hollow cathode discharge formation

In order to investigate the process of optically triggered discharge formation,a model of ion space-charge formation based on classical plane electrodes and revised for a characteristic hollow-cathode discharge(HCD)configuration is proposed in this paper.The primary modified factor in our model is the penetrating electric-field parameter,which influences the ionization of trigger electrons and is calculated via particle simulation.Optical-trigger experiments are carried out using different voltages and under different seed-electron conditions,provided by two different photocathodes,Cu and Mg.The ion-accumulation rates calculated by our model are compared to the discharge-formation time,which is deduced from optical-trigger experiments.The results demonstrate that the process of positive space-charge formation is dominant in the HCD formation process or trigger delay,which is highly dependent on the seeding-electron density and applied voltage,and can therefore be quantitatively described by our model.Additionally,electron-beam generation is investigated by optically triggered HCD experiments on Mg-and Cu-photocathode-based devices.The results show that a more efficient trigger device is capable of generating an electron beam with higher amplitude and density.     

The revised URGAP model to describe the gap conductance between fuel and cladding

The URGAP gap conductance model has been extended and revised generally. An enlarged data base consisting of approximately 1000 data has been constructed and was used to calibrate the revised URGAP model. With this model the gap conductance for very different conditions such as material pairing, gas and contact pressure, surface roughness of fuel and cladding, gap width, gas temperature and composition are very satisfactorily described. URGAP may be used in any code describing the fuel rod behaviour of any reactor type.     

A Disturbance Wave Instability Model for Annular-to-intermittent Flow Transition in Vertical Two-phase Flow System

A model is developed to describe the transition from annular flow to intermittent flow in a vertical two-phase flow system. Since the instability of the disturbance wave, which is a dominant wave shape at the boundary between annular flow and intermittent flow, is considered as a governing mechanism, this instability described by the concept of hyperbolicity breaking in the characteristic equation is included in the model. The developed model is validated by comparing its predictions of gas superficial velocity for the transition with experimental data available in the literature, and comparing those with the predictions of the other correlations. The comparison results show that the model gives better predictions for the transition condition than existing correlations, and the effects of fluid properties, geometry and liquid flow rate on the transition are well considered by the developed model. The average of prediction errors is 3% for the present model. The standard deviation of the prediction errors of the model reaches 28%, which is the smallest among the models compared here.     

Mechanistic Model of Slugging Onset in Horizontal Circular Tubes

A new model of the transition mechanism from stratified gas-liquid two-phase flow into a slug pattern in horizontal circular tubes was developed. This model incorporated the contribution of liquid kinematic energy to wave growth on the interphase surface. The transition limit was numerically determined so as to allow a wave crest to reach the top wall of the horizontal tubes.

Air-water experiments were performed to obtain data for comparison with model predictions. Three test sections were used. They had different inner diameters and the largest test section had a rod bundle inside it. Predictions of liquid flow rate at the flow pattern transition boundary, with given gas flow rates, were within data scatter of the experiments. This suggested that the present model satisfactorily described effects of tube size and internal structure on slugging onset in horizontal circular tubes.     

Theoretical model and experimental investigation optically triggered hollowcathode discharge formation

In order to investigate the process of optically triggered discharge formation, a model of ion space-charge formation based on classical plane electrodes and revised for a characteristic hollow-cathode discharge(HCD) configuration is proposed in this paper. The primary modified factor in our model is the penetrating electric-field parameter, which influences the ionization of trigger electrons and is calculated via particle simulation. Optical-trigger experiments are carried out using different voltages and under different seed-electron conditions, provided by two different photocathodes, Cu and Mg. The ion-accumulation rates calculated by our model are compared to the discharge-formation time, which is deduced from optical-trigger experiments.The results demonstrate that the process of positive space-charge formation is dominant in the HCD formation process or trigger delay, which is highly dependent on the seeding-electron density and applied voltage, and can therefore be quantitatively described by our model.Additionally, electron-beam generation is investigated by optically triggered HCD experiments on Mg-and Cu-photocathode-based devices. The results show that a more efficient trigger device is capable of generating an electron beam with higher amplitude and density.     

蒸汽发生器U型管低含气率两相倒流现象研究

针对立式倒U型管自然循环蒸汽发生器传热管内的两相倒流现象,基于均相流模型,建立了U型管内低含气率两相流动传热理论模型,给出了U型管的进出口压降-质量流量曲线,分析了U型管内出现两相倒流现象的机理,研究了二次侧流体温度和入口含气率对倒流现象的影响规律,并与单相倒流进行了对比。利用RELAP5/MOD 3.3程序对相同条件下的倒流问题进行了计算。研究表明,提高蒸汽发生器二次侧工作压力可减少倒流,两相流入口含气率越高,倒流越易发生,两相流较单相流在U型管内更易倒流。     

Reinforced concrete membrane elements subjected to reversed cyclic in-plane shear stress

A macroscopic model has become noticeable instead of a microscopic model by FEM analysis for concrete structures. Among them the model proposed by Vecchio and Collins is considered to be one of the powerful tools because of its rationalility and simplicity. The essential point of this model is a modified compression theory of cracked concrete and the stress-strain relationship for cracked concrete.This paper follows basically Collins' theory but is revised so as to be able to predict the response of reinforced concrete elements subjected to alternate reversed cyclic in-plane shear simulating earthquake forces. The overall characteristics of the new model exist in the tensile residual strains accumulated by cycles in cracked concrete, which is different from the monotonic loading.     

特定探测器计算模型符合方法研究

特定探测器探头的物理尺寸一般是已知的,但是生产商对一些涉及到探测器性能的尺寸是保密的,诸如探测器的孔径、井深及死层,由此给模拟计算带来了困难。文章通过蒙特卡罗方法建立了均匀分布的面源以及源粒子各向同性运动的抽样方法;计算了Eu152面源与探测器在一定距离的γ射线响应能谱,使用计算结果与相同条件下实验结果的相对效率符合法和能谱相似度符合法校验,并修正探测器模型,从而为确定探测器的计算模型,进一步计算探测器的效率和能谱计算奠定了基础。     

自吸式文丘里水洗器结构设计程序开发

开发了1套自吸式文丘里水洗器结构设计程序,该程序给出了完善的热工参数计算和喉部结构设计逻辑。在实验研究的基础上,提出了阻力计算修正关系式,修正后的计算结果与实验值的相对误差在8.6%以内。     

Improvement of a physical model for blockage formation of solid–liquid mixture flow with freezing for core safety evaluation of SFRs

The SIMMER code has been developed to analyze event progression during core disruptive accidents (CDAs) in sodium-cooled fast reactors. One of the key phenomena during CDAs is the discharge of molten fuel from the core region which reduces the reactivity effectively. The discharge flow is inhibited by blockage formation due to freezing of the molten fuel. Then, the blockage formation is enhanced by unmolten fuel which forms solid–liquid mixture flow with the molten fuel. A physical model for blockage formation of solid–liquid mixture flow with freezing in the SIMMER code is improved in this study to dissolve some inconsistencies between the modeling and the physical phenomena involved in the solid–liquid mixture flow with freezing for more precise evaluation of CDA. The improved model is validated with a systematical procedure through a benchmark analysis of an experiment. Consequently, experimental penetration behaviors are simulated reasonably by the SIMMER code analysis with the improved model while excessive blockage formation occurred in the analysis with the original model.     

氦屏蔽效应的实验与分析

为了解氦屏蔽效应的机现,进行了储氢材料的表面分析工作。结果表明,Ａｒ＾＋与储氢材料间没有可察觉的电相互作用。提出了一个将吸氢过程分为整体流和扩散流两阶段的模型,用以描述整个吸氢过程。该模型能够解释吸氢全过程。     

海洋条件下冷却剂系统自然循环仿真模型

在对核反应堆堆芯冷却剂系统分析的基础上,建立了海洋条件下冷却剂系统自然循环运行状态仿真模拟的数学模型。模型分为稳态计算和动态计算两部分,包括修正的单通道模型、强迫外干扰力模型、两相沸腾计算和动态计算模型等。对于海洋条件,主要是针对左右摇摆的情况进行了计算,并对结果作了简单的分析。计算结果表明模型是可行的。     

Modeling of bubble shape in horizontal and inclined tubes

An experimental and theoretical study on the bubble shape of intermittent flow in the horizontal and inclined pipes has been carried out. The experiment results show that the bubble shape depends on the Froude number, bubble length and pipe inclination. The bubble with staircase pattern tail is observed at low Froude numbers, which is corresponding to plug flow. A model for the prediction of the bubble shape in horizontal and inclined pipes is proposed. The model is able to predict the bubble shape, flow pattern transition between plug and slug flow regimes as well as nose-tail inversion phenomenon observed in the downwardly inclined pipe. Validation shows the model can well predict the bubble shapes in horizontal and inclined pipes. The model discloses that the transition between plug and slug flow regimes occurs within a region. The Froude number range for plug flow regime in the downwardly inclined pipe is much wider than that in the horizontal or upwardly inclined pipe. The assumption of fully developed liquid film under the long bubbles tends to under-estimate the liquid fraction in this part of the slug structure, especially, for the intermittent flow in the upwardly inclined pipe with high Froude numbers.     

Numerical study of the MHD flow characteristics in a three-surface-multi-layered channel with different inlet conditions

A 3D MHD flow simulation was conducted to clarify the effects of the inlet flow conditions on the results of the validation experiment carried out previously and on the design window of the first wall using a three-surface-multi-layered channel. MHD pressure drop was largely influenced by the inlet condition. The numerical model with turbulent velocity profile showed qualitatively good agreement with the experimental result. The first wall temperature and pressure distributions obtained by the 3D simulation corresponded well to those obtained by the 2D simulation assuming fully developed flow. This suggested that complicated three-dimensional inlet flow condition generated in the L-shape elbow would not affects the existing design window.