Abstract
Spent fuel pools are used as temporary storage for spent fuel assemblies in nuclear power plants and are filled with coolant which removes the decaying heat from spent fuel assemblies. Sloshing of the coolant can occur if an earthquake occurs in the area. It may produce additional forces on the pool or inner structure and cause overflow of the coolant. It is therefore critical to investigate the phenomenon of sloshing in a seismic assessment of the spent fuel pool. The size of an actual spent fuel pool is excessive for carrying out an experimental study; thus, a scale model is necessary for experimentation. In this study, a scaling law was defined for test conditions using a scale model to understand sloshing behavior, and the results were validated via computational fluid dynamic analysis. Because sloshing is resonant in a fluid and the first mode natural frequency of a fluid is dominant in sloshing behavior, the test condition could be obtained based on the natural frequency of the fluid. In the model, which is scaled with a factor of “Sf,” the scale factors “Sf,” “Sf0,” “Sf−0.5,” and “Sf0.5” were used for displacement, acceleration, excitation frequency, and excitation time, respectively. Approximately 5% difference in maximum sloshing height between two models was predicted in the only case that 1/8 and 1/4 models (1/8 and 1/4 scaled down from an actual spent fuel pool) were excited with 10 Hz and 7.071 Hz, respectively, but the same sloshing height and pressure were predicted in other cases. The results of this study support the idea that the Froude scaling law can be used when using a scale model for a seismic assessment of spent fuel pools to investigate sloshing behavior.
Highlights
Spent fuel pools are facilities in nuclear power plants that act as temporary onsite storage for spent fuel assemblies which have been used in the nuclear reactor
It has been reported that the generation of hydrogen gas caused by the melting of the zircaloy cladding could lead to an explosion in the spent fuel pool [1,2,3]. erefore, one of the major concerns about the spent fuel pool is its ability for preventing the loss of coolant and maintaining cooling of the radioactive fuel
Several nondimensional numbers such as the Reynolds number, Froude number, Mach number, and Weber number have been used for developing scale models and obtaining suitable experimental conditions. e Froude number, which is de ned as the ratio of ow inertia (Fi) to gravity (Fg) in continuum mechanics, has been used for studying uid behavior using scale models [14, 23, 24]: inertia force gravity force where, ρ, U, L, and g are density, characteristic ow velocity, characteristic length, and acceleration due to gravity, respectively. e dynamic similarity requirement between real and scale models could be satis ed using equality in the Froude number (Fn), shown as follows: U2M U2F, gLm gLF
Summary
Spent fuel pools are facilities in nuclear power plants that act as temporary onsite storage for spent fuel assemblies which have been used in the nuclear reactor. Spent fuel assemblies produce heat from radioactive decay which could result in a critical accident and need to be removed by the coolant within a spent fuel pool. It has been reported that the generation of hydrogen gas caused by the melting of the zircaloy cladding could lead to an explosion in the spent fuel pool [1,2,3]. In the case of the spent fuel pool, the sloshing behavior of the coolant causes additional force on the wall of the pool and the racks [4]. Is overflow, in the authors’ opinion, could be crucial with regard to cooling of the spent fuel assemblies; it is critical to investigate the sloshing behavior of coolant in an evaluation The USNR Commission has reported that decreases in the coolant level by 2.5 ft (1.5 m) was estimated at Units 1 and 3 of the Fukushima Daiichi plant after the Tohoku earthquake (March 11, 2011, Japan) [1]. is overflow, in the authors’ opinion, could be crucial with regard to cooling of the spent fuel assemblies; it is critical to investigate the sloshing behavior of coolant in an evaluation
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