VULNERABILITY ANALYSIS OF NPP EQUIPMENT BASED ON NEURAL NETWORK
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摘要: 核电结构的易损性分析是核电厂地震安全评估中至关重要的一环, 但是由于核电结构的复杂性以及考虑土−结相互作用(SSI)时较大的计算规模, 使得计算核电厂设备易损性曲线十分耗时. 为发展高效的核电厂设备易损性分析方法, 本文采用核电结构土−结相互作用分析的分区计算方法, 并利用有限的SSI分析结果建立神经元模型(ANN)代替有限元模型(FEM), 分别基于对数正态假定的回归法和蒙特卡洛法进行了设备易损性分析. ANN数值模拟包括了以下内容: (1)基于半偏相关系数选择最相关的地震动参数作为ANN输入, 并通过交叉检验建立神经元模型; (2)量化研究ANN数值模拟的预测不确定性, 其中包含了由于简化地震动输入引起的随机不确定性和训练样本缺失引起的认知不确定性; (3)基于ANN模型预测结果分别采用蒙特卡洛法和基于对数正态假定的回归法进行设备的易损性分析. 本文探讨了不同的地震强度指标以及土层材料的不确定性对易损性曲线的影响, 同时验证了回归法中对数正态模型假定的基本合理性, 为核电厂设备易损性分析提供了一种可能方向.
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关键词:
- 易损性分析 /
- 人工神经网络 /
- 蒙特卡洛法 /
- 预测不确定性 /
- 概率土−结构相互作用
Abstract: The vulnerability analysis is a vital part of the seismic probabilistic risk assessment of nuclear power plants. However, due to the complexity of nuclear power structures and the larger calculation scale, the vulnerability analysis of NPP equipment is very time consuming when considering soil-structure interaction (SSI). In order to develop an efficient vulnerability analysis method, this paper adopts a partition calculation method applied to NPP SSI analysis, and establishes an artificial neural network (ANN) using limited SSI analysis results to substitute the FEM process. Based on the regression method with log-normal assumption and Monte Carlo method to analyze the equipment vulnerability. The ANN numerical simulation includes the following contents: (1) Establish the best ANN model through cross-validation to substitute the FEM process, and the most relevant ground motion parameters are selected as the ANN input based on the semi-partial correlation coefficient; (2) Quantification and investigation of the ANN prediction uncertainty. It includes the aleatory uncertainty caused by the simplification of the seismic inputs and the epistemic uncertainty from the limited size of the training data; (3) Computation of fragility curves with Monte Carlo method and the regression method with log-normal assumption based on the prediction data of ANN model. This paper explores the impact on fragility curves induced by different seismic intensity measures and uncertainty of soil material. Meanwhile, the results verify the basic rationality of the lognormal assumption and provide a possible direction for the vulnerability analysis of NPP equipment.-
Key words:
- vulnerability analysis /
- ANN /
- MC method /
- forecast uncertainty /
- probabilistic SSI
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表 1 核电材料不确定性
Table 1. Uncertainties in material parameters of NPP
Type Distribution E/GPa C.V NAB Log-norm 24.7 0.2 NSB Log-norm 32.9 0.2 SCV Log-norm 210.0 0.2 表 2 土层材料不确定性
Table 2. Uncertainties in material parameters of soil
Layer H/m Distribution Vs(m/s2) C.V L1 20 Log-norm 560 0.2 L2 20 Log-norm 673 0.2 L3 20 Log-norm 794 0.2 表 3 地震动特征值
Table 3. Seismic intensity measures
IMs Definition R Rsp PGA $ \max \left| {a(t)} \right| $ 0.73 0.18 PGV $ \max \left| {v(t)} \right| $ 0.29 −0.13 PGD $ \max \left| {d(t)} \right| $ 0.36 0.07 IA $\dfrac{ {\text{π} } }{ {2 g} }\displaystyle\int_0^{ {t_{ {\text{total} } } }} {a{ {(t)}^2}{\rm{d}}t}$ 0.49 −0.03 CAV $\displaystyle\int_0^{ {t_{ {\text{total} } } }} {\left| {a(t)} \right|{\rm{d}}t}$ 0.38 0.03 PSamax $ \max (PSa(T)) $ 0.58 −0.03 Tp $ \arg \max (PSa(T)) $ −0.26 0.16 ASA $\displaystyle\int_5^{33} {PSa(f){\rm{d}}f}$ 0.85 0.33 注: R为相关系数, RSP为半偏相关系数 -
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