采用FFT方法对横摇条件下堆芯核热耦合流动不稳定性的分析

基于开发的海洋条件下堆芯核热耦合流动不稳定性分析程序，利用快速傅里叶变换（FFT）方法对堆芯通道的流量振荡曲线进行分析，获得了静止和横摇条件下堆芯发生核热耦合流动不稳定性时通道的频谱特性。研究表明，静止条件下堆芯发生流动不稳定性时仅具有1个频率峰值，其对应固有频率；在横摇条件下堆芯发生流动不稳定性时，堆芯所有通道均受到横摇条件和核热耦合效应影响，但只有最高功率通道中固有频率处于支配地位，该类功率通道首先发生流动不稳定性。FFT方法可精确地分析复杂流量振荡曲线的特性，进而判定横摇下堆芯核热耦合系统是否发生流动不稳定性。

Analysis of Neutronic/Thermal-hydraulic Coupling Flow Instability in Reactor Core under Rolling Condition Using FFT Method

Based on the developed neutronic/thermal‐hydraulic coupling flow instability code for reactor cores under ocean conditions ,the fast Fourier transformation (FFT ) method was used to analyze oscillation curves of reactor core channels ,and spectrum characteristics of reactor core channels occurring flow instability under static and rolling conditions were obtained .The results show that one spectrum peak can be found when the flow instability happens under static conditions ,and the corresponding spectrum is called inherent spectrum .For the flow instability occurred under rolling conditions ,all channels of the reactor core are affected by both rolling conditions and neutronic/ther‐mal‐hydraulic coupling effect , and the inherent spectrum is dominant in the highest power channels which means that the flow instability is firstly induced in those chan‐nels .T he characteristics of the complicated oscillation curves of mass flow rate can be analyzed precisely by FFT method to estimate whether the neutronic/thermal‐hydraulic coupling flow instability under rolling conditions occurs .