Design of Offshore Intake structures for Nuclear Plants

Abstract

ABSTRACT Many problems in designing offshore intake structures for recirculating systems to cool nuclear plants cannot be solved analytically - - experiments are needed. Hydro Research Science Company constructed an experimental basin to simulate complex coastal hydraulic conditions which affect intake structures. Solving intake design problems must be preceded by basic studies to correlate relevant variables. These interrelated variables fall into three categories: the intake structure itself, hydraulic conditions around the intake, and environmental conditions peculiar to a coastal site. Intakes can assume many shapes. Although many problems can be solved by changing the intake's design, hydraulic variables such as cross currents and waves sometimes preclude purely geometric solutions, but require an imaginative use of hydraulic conditions. Model intakes were evaluated by reproducing the approach flow conditions in the experimental basin and then observing and recording current velocities and flow directions in both near and far areas. The data was then subjected to dimensional analysis. Approach flow conditions recreated in the basin revealed that peripheral conditions strongly influence approach flow patterns to the intake structure. INTRODUCTION 1 In recent years many nuclear power plants have been constructed in coastal regions for easy access to the large quantities of water needed for recirculating cooling water systems. Designing such systems poses multiple challenges to an engineer: environmental restrictions, complex coastal waters, and regulatory restrictions in flow conveyance inherent in power plant operations. Many of these design problems cannot be solved by analytical means but must be solved by physical modeling. This paper describes the design of offshore intake structures based on such model studies. 2 The key elements of a circulating water system in a power plant are an intake and outlet structure, a pumping plant, and a conveyance system to circulate the coolant. Substantial amounts of water are circulated and the design of all components incorporates complex hydraulic analyses. This paper focuses on the hydraulic evaluation of intakes for cooling recirculating systems in nuclear plants. Such intakes can be classified in three types (Plate 1):Onshore intake structures, such as the Diablo Canyon Nuclear Plant, in which the onshore intake structure pumps the circulating water into the plant, recircu1ates it through the system, and discharges it through a specially designed compact structure. [1] [2]Offshore intake structures, such as the San Onofre Nuclear Plant, in which the intake and outlet structures are approximately 3, 000 ft offshore and the water is conveyed to and from the plant through a submarine pipe. [3]Offshore floating intake structures, such as the proposed Floating Nuclear Plant, in which the intake structure is incorporated into the compact power plant and is on a floating platform sheltered by surrounding breakwaters. [4] 3 The design considerations of the offshore intake structures enumerated under (b) above will be the topic of this paper. The submerged intake is the initial component of the circulating cooling water system. It consists of the intake structure proper which is connected to a conduit.