地震载荷下反应堆系统的不确定性量化

反应堆结构力学分析中，由于设计变更、制造安装、计算偏差等因素的影响，会导致力学分析关键输入参数存在一定的不确定性，这种不确定性将直接影响到动力响应、载荷分配与最终的力学评价结果。为量化参数不确定性对载荷计算的影响，本文采用不确定性量化的方法，以反应堆系统为研究对象，开展了地震载荷下系统关键结构参数对系统动力响应与载荷分配的不确定性量化研究。首先依据关键参数的基本特性，利用最大熵原理，建立了描述反应堆系统部件间接触刚度和间隙的概率密度函数。随后，应用马尔科夫链蒙特卡罗采样技术对系统关键参数进行采样，并通过有限元瞬态计算获得了输入输出数据池。最后，以样本数据为基础，考察了不确定性参数对部件动力响应统计分布的影响，开展了名义模型的可靠性与不确定性量化分析。研究发现，结构参数不确定性对系统响应的影响在不同部位、不同频域内呈现不同的分布。在考察名义模型的可靠性时应根据响应具体形式有针对性地进行量化。本文所提出的不确定性量化方法对核动力装置其他系统和设备的动力分析具有推广价值。

Uncertainty Quantification of Reactor System under Seismic Load

In the mechanical analysis of reactor structure, due to the influence of the design change, manufacturing and installation and calculation deviation, the key mechanical analysis input parameters of reactor system are uncertain, which affects the dynamic response, load distribution and final mechanical evaluation results. In order to quantify the influence of input parameter uncertainty on seismic responses and load distribution, uncertainty quantification of key structural parameters of reactor system under seismic load was studied. Firstly, according to the fundamental characters of contact stiffness and clearance among various assemblies of the reactor system, maximum entropy principle was adopted to construct the probability density distributions of these design parameters. Then, Markov chain Monte Carlo technique was applied to sample data points according to given probability density function (PDF), and the input and output data pool was constructed via finite element transient computations. According to the results, statistic distributions of dynamic responses caused by uncertainty parameters were evaluated and the reliability of nominal model and uncertainty quantification of reactor system were examined. The results show that the influence of structural parameter uncertainty on system response presents different distributions in different parts and different frequency domains. When examining the reliability of the nominal model, the uncertainty should be quantified according to the specific form of the response. The uncertainty quantification method proposed in this paper provides a way for the dynamic analysis of other systems and equipment in the nuclear power plants.