Computational method for the added mass of fluid imposed on spent fuel storage racks considering three-dimensional flow

Abstract

Spent fuel in nuclear power plants is usually stored temporarily in spent fuel pools in the form of racks. Seismic analysis of the racks is required for the structural safety of the spent fuel. Since the racks are arranged in water, the seismic analysis of the racks should consider the fluid–structure interaction effect (i.e. the added mass of fluid imposed on spent fuel storage racks). The traditional computational method for the added mass is to simplify the racks to a concentric square column with a two-dimensional flow. This simplification improves computational efficiency but results in excessive margins. In addition, since the rack of CAP1400 (a Chinese AP-type PWR) uses a porous structure, which is different from the conventional rack, the traditional simplified method cannot be used to calculate the added mass of the rack of CAP1400. Therefore, this paper proposes a computational method for the added mass, in which the three-dimensional flow, as well as the internal pores of the rack, are considered so that the excessive margin can be reduced. Using this new method, a formula with four factors was given to calculate the added mass coefficient. Among four factors, the dimensionless gaps in X and Y directions represent two-dimensional flow effect, while the dimensionless height of the rack represent three-dimensional flow effect. The new method is verified by a scaled down experiment for rack of CAP1400.