摘要
硝酸盐自然循环回路(Nitrate Natural Circulation Loop,NNCL)是研究熔盐自然循环特性的重要实验平台,通过NNCL数值模拟及参数的敏感性分析,加深对熔盐自然循环的理解,为熔盐堆非能动余热排出系统设计积累经验。通过实验数据,验证数值模拟及不确定性分析的正确性,并基于敏感性分析方法研究输入参数对自然循环流量的影响。采用修改后的RELAP5/MOD4.0程序,建立NNCL分析模型,采用基于蒙特卡罗的不确定性分析法计算数值分析的不确定性。采用多元线性回归法研究输入参数的敏感性。结果表明数值模拟结果和实验数据符合性较好,同时不确定性分析的上下限值可包络NNCL实验结果及其误差。通过敏感性分析,对影响自然循环的输入参数的重要性进行排序。修改后的RELAP5/MOD4.0程序结合不确定性分析,适用于硝酸盐自然循环的数值分析。影响自然循环最敏感的3个因素分别为回路阻力系数、硝酸盐密度、硝酸盐比热。
[Background]The nitrate natural circulation loop(NNCL)serves as a crucial experimental platform for studying the natural circulation characteristics of molten salts.Numerical simulation and sensitivity analysis of parameters in the NNCL deepen our understanding of molten salt natural circulation,thereby accumulating experience for the design and validation of passive residual heat removal systems in molten salt reactors.[Purpose]This study aims to validate the accuracy of numerical simulations and analyze uncertainty using experimental data,and explore the impact of input parameters on natural circulation flow rate through sensitivity analysis.[Methods]The modified RELAP5/MOD4.0 code was employed to establish a nitrate natural circulation analysis model.New models related to molten salt such as molten salt fluids(nitrate,FLiNaK,etc.),heat transfer correlations,liquid-fueled reactor models,etc.were added to RELAP5/MOD4.0.The NNCL system model consisted of three coupled parts,i.e.,the primary circuit,molten salt pool and air cooling system modules,was validated by experimental data.The propagation of input uncertainty approach on the bassis of Monte Carlo methods,was used to calculate uncertainty bounds of numerical analysis,and 14 uncertain parameters for NNCL transient were selected through previous studies,experimental data and expert judgment.Consequently,a list of input parameters along with their associated density functions was adopted by using a probabilistic methodology.Wilks'formula was used to quantify the minimum number of code runs,and the upper tolerance limit's percentile and confidence were set to the standard 95%/95%.Once the code run number and sets of uncertain input parameters were established,input uncertainty was propagated through the modified RELAP5/MOD4.0 code,hence the upper and lower uncertainty bands were obtained.The sensibility of input parameters was analyzed by performing Multiple Linear Regression(MLR)method.Finally,the standardized regression coefficient(SRC)was used to rank the importance of input parameters affecting natural circulation.[Results]Numerical analysis results indicate that variations in NNCL cold-end and hotend temperatures,as well as main loop nitrate flow rates,align with experimental trends,and the maximum error between the upper and lower limits of uncertainty analysis relative to experimental data is-5.7%to 4.2%for the DRACS(Direct Reactor Auxiliary Cooling System)Heat Exchanger(DHX)inlet temperature,-3.5%to 4.0%for the DHX outlet temperature,and-12%to 12%for the NNCL primary loop nitrate flow rate.The uncertainty analysis's upper and lower bounds effectively encompass experimental data and experimental errors.The calculated F-value is 2682.0,which is greater than 2.32,this indicates that at theα=0.01 significance level,there is a significant linear relationship between the nitrate flow rate of the NNCL system and the 14 input parameters.[Conclusion]The incorporation of uncertainty analysis with the modified RELAP5/MOD4.0 code presented in this study provides a good prediction of NNCL system operational characteristics.Through sensitivity analysis,heat transfer coefficient of air side,local resistance coefficient of primary loop,and density of nitrate are identified as three most sensitive factors affecting natural circulation.
作者
王凯
王超群
蔡创雄
杨群
何兆忠
王纳秀
WANG Kai;WANG Chaoqun;CAI Chuangxiong;YANG Qun;HE Zhaozhong;WANG Naxiu(Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《核技术》
北大核心
2025年第12期120-128,共9页
Nuclear Techniques
基金
中国科学院青年创新促进会(No.E3292901)资助。
