Improvement in the accuracy of SPACE prediction for the unblocked FLECHT SEASET reflood tests by data assimilation. (October 2021)

• Record Type: Journal Article
• Authors: Tiep, Nguyen Huu; Kim, Kyung Doo; Heo, Jaeseok
• Is Part Of: Annals of nuclear energy. Volume 161(2021)
• Publication Date: 2021-10
• Subjects: Reflooding simulation -- Data assimilation -- Sampling approach -- FLECHT-SEASET experiment -- Accuracy improvement; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2021.108462
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: Nearly all the a posteriori quenching times reached the measured values. The lower PCTs were strongly improved while the higher PCTs were slightly enhanced. The accuracy of all F-S runs was generally enhanced with the improvements up to 23.6% The most sensitive physical model was saturated film boiling heat transfer coefficient. The total mismatch of calculation and experiment were drastically reduced. 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.