A simplified method for evaluating sloshing impact pressure on a flat roof based on Wagner's theory

In sodium-cooled fast reactors, free liquid surfaces are found in several important components, including reactor vessels; sloshing due to earthquakes is one of the major concerns in design. Especially in cases where seismic isolation systems are installed to prevent or reduce damages to facilities due to earthquakes, periods of vibration are lengthened and become close to natural sloshing periods. As a result, sloshing is more likely to occur. In severe seismic conditions, sloshing waves are considered to even reach a roof slab of a reactor vessel. The structural integrity of roof slabs is required to be evaluated against sloshing impacts. However, there is no widely recognized evaluation method for sloshing impact pressure on flat roofs yet. Therefore, in this paper, a simplified evaluation method is proposed based on Wagner's theory, which is a well-known classic theory for evaluating impact pressures on rigid wedges dropping on water surfaces. In the proposed method, we assume an equivalent wedge on a flat roof. The impact pressure on the equivalent wedge is evaluated by applying Wagner's theory. Computational fluid dynamics analysis is conducted to confirm that a key assumption of Wagner's theory is applicable to the evaluation of sloshing impact on a flat roof. In addition, the predictability of the proposed method is investigated by comparing literature data of sloshing experiments with the estimated values. (author)