Improvement in the accuracy of SPACE prediction for the unblocked FLECHT SEASET reflood tests by data assimilation

Abstract This study aims to improve the reliability of the Safety and Performance Analysis Code (SPACE) prediction for reflooding phenomena. We utilized the data assimilation technique, which can improve the reliability of the system by adjusting the model parameters within their uncertainty limits, to enhance the accuracy of the cladding temperature, the quenching time, and the steam temperature prediction of SPACE for the reflood tests. The Fast Fourier Transform Based Method (FFTBM) was applied to examine the improvement of the SPACE code before and after the data assimilation process. We found that generally the investigation results of all the reflood tests were enhanced by using the sampling approach of data assimilation. Moreover, the large impact models that significantly contributed to the prediction accuracy of this problem were identified. One can focus on improving these models to enhance the calculation accuracy.