Wave-induced effects have been observed in a model of the cooling water intake basin of the Pacific Gas and Electric Company's Diablo Canyon Nuclear Power Plant. This model, built to an undistorted scale of 1:45, was constructed initially to study the design for the repair of the terminus region of the West breakwater damaged in storms of January 28, 1981. It was decided by PG&E to investigate, in the same model, the forces due to waves acting on two air intake structures for the auxiliary saltwater pumps and the pressures or. the external and the internal walls and the ceiling of the cooling water intake structure located in the manmade cooling water intake basin. During the course of the experiments it was noticed that the mean water level in the breakwater enclosed basin changed as a function of the incident wave characteristics. This allowed waves to overtop the cooling water intake structure which, without the change in mean water level, would not have occurred. It is this difference between the mean water level and the still water level inside the cooling water basin, defined as ponding, which will be reported herein. Diskin, et al. (1970) investigated this effect behind low and submerged permeable breakwaters in a two-dimensional wave tank model. As was mentioned by them, in normal breakwater tests it is a common practice to provide some means of communication between the seaward and shoreward side of the breakwater so that precisely this mean water level change due to overtopping of the structure does not occur. For their experiments the change in mean level varied from about 5% of the deep water wave height to 32% of the deep water wave height depending upon the submergence of the breakwater crest; the smallest change corresponded to the largest depth over the breakwater crest. This effect was discussed by Dalrymple and Dean (1971), and they proposed an analytical model based on the conservation of mass. The estimated inflow was equated to an estimate of the return flow over and through the permeable structure. Some limited agreement with the results of Diskin, et al. (1970) were shown.
WAVE-INDUCED EFFECTS IN A COOLING WATER BASIN
