基于格林函数节块法的物理与热工-水力耦合方法研究

开发了三维物理与热工-水力耦合的PWR堆芯瞬态分析程序NGFMN-K/COBRA-Ⅳ/COBRA-Ⅳ(NCC)。少群时空中子动力学计算采用格林函数节块法程序NGFMN-K,隐式耦合子通道程序COBRA-Ⅳ实现瞬态计算。采用P10H8B功率重构方法给出热组件栅元功率分布,耦合另一个COBRA-Ⅳ程序模块,进行热组件子通道分析得到安全参数。对NEACRP-L-335 C1弹棒基准问题的计算表明,NCC程序的计算结果与参考结果符合很好,说明程序计算正确,可用于评估事故结果。     

子通道分析程序LINDEN的开发与初步验证

中国广东核电集团有限公司自主开发的子通道分析程序LINDEN采用基于同位网格有限差分技术的四方程漂移流模型以及面向对象的模块化编程技术。该程序具备分析计算的可靠性、稳定性。通过LINDEN和COBRA-Ⅳ程序分别对大亚湾1#、2#机组稳态工况进行了计算分析。结果表明,LINDEN程序和COBRA-Ⅳ程序的计算结果总体吻合较好,LINDEN程序可适用于大型压水堆的热工水力分析。     

反应堆子通道分析中的一步混合网方法及CHAN-2程序

本文论证了一步混合网方法的可靠性与先进性,说明了CHAN-2程序比COBRA-ⅢC/MIT-2等程序的计算速度快,通过对Maine Yankee堆热组件出口水温的计算,表明CHAN-2程序的计算结果与堆内实测值是吻合的。文章还给出了对秦山核电站反应堆堆芯作子通道分析所得的数据及其与单通道分析结果的对比。     

耦合的PWR三维物理与热工-水力堆芯瞬态分析程序系统NLSANMT/COBRA-Ⅳ

介绍了采用非线性迭代半解析节块展开法求解的三维节块时-空中子动力学计算程序NLSANMT,并将其与子通道热工-水力堆芯分析程序COBRA-Ⅳ耦合,形成PWR三维物理与热工-水力堆芯瞬态分析程序系统NLSANMT/COBRA-Ⅳ.对OECD NEACPR PWR弹棒基准问题的计算表明,即使每个组件使用一个节块、每个节块一个通道,NLSANMT/COBRA-Ⅳ的计算结果仍然和参考值符合得很好.     

采用权重留数法进行燃料元件瞬态热传导分析的 RTEMP 程序

RTEMP 程序是参考国外较先进的 COBRA-4 程序编制的。文中介绍了该程程序采用的模型和求解方法的特点。把基尔霍夫(Kirchoff)变换用于热传导方程及其定解条件,采用正交排列的权重留数法处理径向导热项。文中还介绍了方程的推导、演变及处理方法。给出了计算实例。其计算结果与 COBRA-4 程序计算值及解析解的数据符合得很好。     

三维物理-热工耦合系统RECON的开发与验证

基于RELAP5、COBRA-Ⅳ和NLSANMT程序,采用并行耦合模式与并行虚拟机技术,开发了三维物理-热工耦合系统RECON,其耦合形式灵活,可根据分析需要选择用于耦合的程序。利用系列基准题进行了验证,特别是针对MSLB基准题的计算,与国际上众多耦合程序相比,RECON具有较好的计算精度,可用于反应性引入事故分析     

RIA基准题验证堆芯三维物理-热工耦合程序

以COBRA-Ⅳ和NLSANMT程序为基础,开发了堆芯三维物理-热工耦合程序C4/NK。针对两个典型的反应性引入事故（RIA）,即NEACRP弹棒基准题和提棒基准题,分别进行了验证计算。与参考值和其他程序的计算结果相比,C4/NK耦合程序具有较好的精度,能正确模拟瞬态过程中的物理-热工反馈现象。     

非能动压水堆热工水力多尺度耦合计算分析研究

本文为了更加真实准确的模拟非能动核电机组复杂的热工水力工况,提高事故分析计算精度,开展了非能动压水堆热工水力多尺度耦合计算分析研究。首先应用热工水力系统分析程序RELAP5对AP1000机组进行系统建模,并开展冷却剂强迫流动完全丧失事故(全失流事故)的分析计算,得到堆芯相关热工水力参数。然后将RELAP5程序的计算结果作为边界条件,分别利用子通道程序COBRA-Ⅳ、计算流体力学程序FLUENT以及基于两个程序的耦合程序对AP1000堆芯组件进行建模,并分别开展全失流事故过程中堆芯热工水力分析计算。最终通过三个程序计算结果的对比,表明应用耦合程序开展堆芯热工水力分析的方法可行,建立的堆芯组件模型合理,计算结果更加接近真实情况,有效减少了单一程序计算的过度保守性。     

基于单粒子程序的软件检测

介绍了BESⅢ离线软件检测系统的框架以及单粒子检测程序的作用和工作原理。单粒子事例可以根据不同的需求产生不同的事例样本,是离线软件检测中不可缺少的重要部分。利用本文所述的单粒子检测程序可以检测BESⅢ各个子探测器的模拟和重建程序,快速自动发现离线软件不同版本的变化,从而为软件开发人员提供参考,发现可能存在的问题。     

人工神经网络在棒束临界热流密度预测中的应用

基于已有的棒束临界热流密度数据库，采用COBRA-Ⅳ程序计算得到子通道局部临界热流密度数据库。用人工神经网络（ANN）理论对数据库进行训练，得到基于ANN理论的棒束临界热流密度预测模型。预测模型的预测精度显著高于常用经验关系式的预测精度，其预测值的均方差为5.63%。     

Scaling effects predicted by COBRA/TRAC for UPI plant best estimate LOCA

The COBRA/TRAC-MOD7A, Rev. 1 code is currently licensed for best estimate LOCA analyses of 3 and 4 loop PWRs. As part of a licensing effort to extend the code application to plants equipped with upper plenum injection (UPI), scaling effects predicted by the code are investigated. The scaling effects of UPI tests were obtained through data analyses and summarized in Damerell and Simons (1993). The scaling subjects are: breakthrough flow area, downflow rate into the core, hot leg water carryover, and liquid level in upper plenum. The test facilities that supplied the data include UPTF and CCTF. In this report, the scaling trend is obtained from COBRA/TRAC analyses of CCTF Run 72 and Run 76 (scaling factor 0.091), UPTF Tests 20A, 20B, and 20C (scaling factor 2.1), and a typical UPI plant (scaling factor 1.0). The predicted scaling trend is found to agree well with the test data.     

棒束中高含气量空泡份额计算模型适用性的研究

在子通道分析程序中,空泡份额计算模型对两相流的分析预测结果有显著影响.在较高含气率条件下,空泡份额计算模型在子通道分析程序COBRA中的适用性并没有经过充分的验证.本文用COBRA程序中自带的空泡份额计算模型与选自文献的4个空泡份额模型,对4×4棒束的气.液两相流进行子通道分析.结合实验数据,选取相对焓升和相对质量流速比,对预测结果进行分析评估.结果表明,在本文的计算范围内,Dix模型和滑速比S=1.5时的滑速比模型的预测结果最优.     

子通道程序SUBSC的开发及稳态验证

采用面向对象模块化编程技术开发了面向大规模热工水力计算的自主化子通道程序SUBSC,利用SUBSC和COBRA程序分别计算了典型压水堆1/4组件,结果表明,两者计算结果吻合很好。为进一步验证SUBSC程序,计算了PSBT稳态5×5棒束基准题,结果表明,在各种工况下SUBSC程序计算得到的通道平均含汽率与实验测量值吻合很好,最大相对偏差仅为0.7%,证明了程序具有较高的计算精度。为提高SUBSC程序的计算效率,引入不完全LU分解预处理的再启动GMRES算法求解质量守恒方程,对多组件的计算结果表明,SUBSC程序具备大规模热工水力计算能力。     

Research on Adaptive BP Neural Network Prediction Method for Thermal Parameters of China Experimental Fast Reactor

Whether the thermal-hydraulic parameters of China Experimental Fast Reactor (CEFR) core exceed the limit is the standard for evaluating the safe operation of the reactor. For the maximum temperature prediction problem of fuel cladding, after generating the data samples by the core sub-channel analysis code COBRA, an intelligent prediction code based on adaptive BP neural network algorithm was developed in the paper. For a specific single-box component, only the core inlet power and mass flow rate were required to achieve fast and accurate prediction of the fuel cladding maximum temperature. Compared with COBRA, in the scenario of large-scale repetitive calculation, self development code can save a lot of calculation time and rescource, and improve the operating efficiency of fuel cladding design and CEFR operation. The experimental analysis shows that the maximum relative error of BP neural network method is less than 6%, the average prediction relative error is less than 3%, and the calculation efficiency is improved to 300 times of the original code. So the prediction accuracy of the network model is high, and self development code is easy to apply to other parameter predictions of the experimental fast reactor.     

中国实验快堆热工参数的自适应BP神经网络预测方法研究

中国实验快堆（CEFR）堆芯的热工参数是否超出限值是评价反应堆安全运行的标准。本文针对燃料包壳最高温度预测问题,通过堆芯子通道分析程序COBRA生成数据样本后,开发基于BP神经网络自适应算法的智能预测程序,对于特定的单盒组件,仅需给出堆芯进口功率和流量,即可实现燃料包壳最高温度的快速准确预测。结果表明,与COBRA相比,在大规模重复性计算的场景下,自开发程序能节约大量计算时间和算力,提高燃料包壳设计和CEFR运行时的操作效率。实验分析得出BP神经网络方法的最大相对误差不超过6%,平均预测相对误差不超过3%,计算效率提升至原程序的300倍,网络模型的预测精度高,且易推广至实验快堆其他参数预测,具有很大的应用前景。     

Flow redistribution due to void drift in two-phase flow in a multiple channel consisting of two subchannels

Void drift in two-phase flow is studied experimentally using a geometrically simple, vertical channel consisting of two interconnected subchannels. Data on the flow redistributions of both air and water along the channel axis are obtained and presented for the following two multiple channels: one with two circular subchannels of different cross-sectional area and the other with two identical circular subchannels. The data are analysed by a simple one-dimensional subchannel code taking account of the effects of void drift and turbulent mixing between subchannels, i.e. incorporating both the void-settling model of Lahey et al. and a term similar to that in the COBRA code in the momentum equation. The flow redistribution process can be explained by the analysis.     

Dimensionally adaptive dynamic switching and adjoint sensitivity analysis: new features of the RELAP5/PANBOX/COBRA code system for reactor safety transients

This paper highlights two novel features that have been implemented into the coupled RELAP5/PANBOX2/COBRA3 (R/P/C) code system. On the one hand, the R/P/C code system has been extended to include a dimensionally adaptive algorithm that uses the underlying physical phenomena to switch dynamically between three-dimensional (3D), one-dimensional (1D), and point-kinetics models, thereby reducing computational times up to a factor of five while preserving the accuracy, within user-defined error criteria, of the 3D reference calculation. On the other hand, the R/P/C system has also been extended to include the Adjoint Sensitivity Analysis Procedure (ASAP) for the RELAP5/MOD3.2 two-fluid model with non-condensables, thus enabling the efficient calculation of local sensitivities of RELAP5 results to various parameters in the RELAP5 code.     

钠冷快堆自然循环组件子通道程序初步研发

本文为计算和分析钠冷快堆自然循环组件的热工水力特性,开发了钠冷快堆堆芯自然循环冷却组件子通道分析程序。基于61棒单组件模型,通过将本程序的结果与COBRA程序进行比较,验证了钠冷快堆堆芯自然循环冷却组件子通道分析程序对自然循环冷却组件的适用性。基于多盒组件模型,初步验证了本程序具备自然循环冷却组件的流量分配和盒间换热计算的功能。本程序能为池式快堆自然循环冷却组件提供有效的设计和分析工具。     

Analyses of subcooled CCFL tests for evaluation of W̱COBRA/TRAC applicability

The W̱COBRA/TRAC-MOD7A, Rev. 1 code is currently licensed for best estimate large break LOCA analyses of 3 and 4 loop PWRs with emergency core cooling system injection located in the cold legs. As a part of the licensing effort to extend the code applicability to an upper plenum injection plant, the codes ability to predict subcooled flooding on a perforated plate was assessed by analyses of GE counter current flow limit tests and by comparison to the Bankoff flooding correlation (Bankoff, S.G., Tankin, R.S., Yuen, M.C., Hsieh, C., 1981). Counter current flow of air/water and steam/water through a horizontal perforated plate, Int. J. Heat Mass Transfer, 24 (8) 1382). The observed code model bias for subcooled CCFL can be eliminated by applying multiplication factors to the interfacial condensation and the interfacial drag models.     

Assessment of flooding in a best estimate thermal hydraulic code ( COBRA/TRAC)

The performance of COBRA/TRAC code in predicting the flooding, the counter-current flow limit, is evaluated in three geometries important to nuclear reactor loss-of-coolant accident evaluation; a vertical pipe, a perforated plate, and a downcomer annulus. These flow limits are computationally evaluated through transient conditions. The flooding in the vertical pipe is compared with the classical Wallis flooding limit. The flooding on the perforated plate is compared with the Northwestern flooding data correlation. The downcomer flooding in 1/15th and 1/5th scale model is compared with the Creare data. Finally, full scale downcomer flooding is compared with the UPTF test data. The prediction capability of the code for the flooding is found to be very good.