Modification of the fast fourier transform-based method by signal mirroring for accuracy quantifi cation of thermal-hydraulic system code

A thermalehydraulic system code is an essential tool for the design and safety analysis of a nuclear powerplant, and its accuracy quantification is very important for the code assessment and applications. The fastFourier transform-based method (FFTBM) by signal mirroring (FFTBM-SM) has been used to quantify theaccuracy of a system code by using a comparison of the experimental data and the calculated results. Themethod is an improved version of the FFTBM, and it is known that the FFTBM-SM judges the code accuracyin a more consistent and unbiased way. However, in some applications, unrealistic results have beenobtained. In this study, it was found that accuracy quantification by FFTBM-SM is dependent on the frequency spectrum of the fast Fourier transform of experimental and error signals. The primary objective ofthis study is to reduce the frequency dependency of FFTBM-SM evaluation. For this, it was proposed toreduce the cut off frequency, which was introduced to cut off spurious contributions, in FFTBM-SM. Amethod to determine an appropriate cut off frequency was also proposed. The FFTBM-SM with themodified cut off frequency showed a significant improvement of the accuracy quantification KCI Citation Count: 1