Hydraulic study on reconstruction of the cooling water outlet for No.2 unit of Tsuruga Power Station to suppress emission of foams

The power generating unit No. 2 of Tsuruga Power Station, Japan Atomic Power Company, started its operation in 1987. Since then, a problem of the emission of sea water foam from the cooling water outlet took place. Foaming water is not a contaminant to water quality, but it is undesirable from the viewpoint of seascape. Thus in order to suppress the emission, a few types of countermeasure works, a flexible floating curtain type like an oil fence, for instance, were applied to the sea area just off the outlet. But all of these countermeasures did not work well. In 1994, the authors started a project to investigate how to eliminate the initiation of bubbles in the cooling water streams by flow simulation using both numerical and physical, reduced scale, models. The answer is outflow through a submerged discharge culvert, which eliminates an abrupt fall in water surface level which will cause initiation of bubbles. A detailed hydraulic model test was carried out to select the best option among three culvert type plans. JAPCO constructed the selected submerged discharge culvert during a period of scheduled inspection of the generating systems in 1997. Thereafter no emission of foamy water has been observed in front of the outlet both in calm summer and in stormy winter. (author)