Development and application of 3D pool-type sodium cooled fast reactor system analysis program

Sodium cooled fast reactor (SFR) is the most comprehensively studied and the most extensively operated reactor-type in the 4th generation of nuclear power plants. One of the key points of the transient analysis in pool-type SFR is refined analysis of the transient thermal-hydraulic characteristics of the 3D sodium pool. In this paper, according to the characteristics of pool-type SFR, a three-dimensional (3D) system analysis model is developed. The difficulties involved: establishment of the basic 3D mathematical model, method for processing 3D momentum convection terms, accurate simulation of the position 1D pipe and 3D space. On this basis, the 3D transient analysis program NUSOL-LMR-3D for pool-type SFR is independently developed. Then, the 3D system model is fully verified with the MONJU thermal stratification experiment and the EBR-II transient experiment. Subsequently, NUSOL-LMR-3D program was applied to the 3D transient safety analysis of the TBO accident of (CEFR). The results show that NUSOL-LMR-3D program can accurately simulate the accident process, and it is pointed out that there is obvious thermal stratification in the hot sodium pool around 50s after the accident. The temperature gradient on the thermal interface is relatively large, which may result in a large thermal stress on the internal structure of the pool. Besides, the location with maximum temperature gradient of the inner barrel wall and central measuring column were suggested through analyzing the temperature field of the inner hot pool. The most attention should be paid to the area of the inner barrel wall axial position of 0.45 m–0.65 m and the central measuring column axial position of 0.65 m–0.95 m. This study provides an in-depth analysis of the three-dimensional transient thermal-hydraulic characteristics of the pool-type SFR, which solves the problem of rapid and refined analysis of the 3D sodium pool and provides a reference basis for the design of fast reactor systems.