基于系统分析软件的IRWST中PRHR HX建模方法研究

本文针对AP1000内置换料水箱(IRWST)热工水力特性缩比实验4种典型的沸腾工况，应用两种不同的系统分析软件（RELAP5/SCDAPSIM mod3.4和COSINE），将三维模型简化为一维模型。基于单通道和多通道两种不同建模方法，研究不同的初始温度、加热功率、水箱水位工况下，水箱内的温度、沸腾时间等参数的变化。结果表明，RELAP5单通道模型与多通道模型计算结果低于实验值，COSINE的单通道模型与多通道模型计算结果高于实验值，两种软件的计算精度相当。RELAP5计算模型的沸腾时间整体上晚于实验时间，COSINE计算模型的沸腾时间整体上早于实验时间，采用多通道模型后，每个工况达到沸腾的时间均短于单通道模型，表明采用多通道建模方法后，模型整体的换热能力提高，缩短了模型整体沸腾所需的时间。在系统安全分析的建模过程中，可根据水箱内温度、整体沸腾时间对安全保守性的影响，确定具体的建模策略。

Research on Modeling Method of PRHR HX in IRWST Based on System Analysis Software

The in-containment refueling water storage tank (IRWST) is an important part of the passive residual heat removal system of AP1000. In order to evaluate the residual heat removal capability of AP1000, it is necessary to build a suitable model for IRWST and its heat exchanger. However, there is no common method yet to model the refueling water tank and its heat exchanger. In this work, the three-dimensional IRWST heat exchanger was simplified to one-dimensional model with two different system analysis softwares (RELAP5/SCDAPSIM mod3.4 and COSINE). With the support of Major National Science and Technology Projects, the scaled-down AP1000 separated-effects IRWST passive residual heat removal heat exchanger (PRHR HX) test facilities were built in North China Electric Power University to investigate the thermal hydraulic behavior after residual heat removal accident. In this paper, four typical boiling experiment conditions were simulated in above two system analysis softwares with single channel and multi-channel models respectively. The temperature distribution and boiling time of tank were studied under different initial experimental conditions, such as different initial water temperatures, heating power and initial water levels. It is shown that the computed temperature with RELAP5 single channel model and multi-channel model are lower than the measured values, and with the development of natural convection, subcooled boiling and pool boiling, the error increases gradually. In the later stage of the heat transfer process, the consistency between the calculation results of the multi-channel model and the experiment is better than that of the single channel model. The computed temperatures with COSINE single channel model and multi-channel model are higher than the measured values, and the calculation accuracy of the two softwares is equivalent. The calculated overall boiling time with RELAP5 software is later than the experimental time, and the calculated boiling time with COSINE software is generally earlier than the experimental time. Compared with single channel model, multi-channel model takes the transverse cross flow between different channels into consideration, which can improve the overall heat transfer efficiency and shorten the overall boiling time. In the modeling process of system safety analysis, the specific modeling strategy can be determined according to the influence on safety response of the temperature and the overall boiling time from the perspective of conservatism.