Nuclear Power Plants - Koeberg, South Africa

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Nuclear Power Plants - South Africa

ESKOM, the South African electric utility, operates a 2 unit site at Koeberg Nuclear Power Station near Capetown. Each unit is a 3 loop Framatome Pressurized Water Reactor rated at 920 MWe. The trubine-generator sets were provided by Alsthom. The picture below shows the 2 units, each with a metal/concrete containment. A breakwater can be seen on the seaward side of the plant. The condenser on the secondary side is cooled by seawater. Unit 1 started up in 1984 and Unit 2 in 1985.

Courtesy ESKOM

The Framatome units are the French version of the Westinghouse PWR. Each of the 3 cooling loops is connected to the reactor and a reactor coolant pump and a steam generator. A pressurizer is connected to one of the 3 loops.

A number of simplified diagrams illustrate the the design of this pressurized water reactor plant (courtesy Westinghouse). The following are colored perspective and arrangement drawings of

The flow paths are illustrated by a colored graphic flow diagram and a black and white line drawing. The following describes the flow path and the linked drawings illustrate, in detail, the composition and major parts of the components. The temperatures stated are representative of many PWRs and may vary for specific plants.

Reactor - this diagram shows how the reactor is constructed with its major components. Water at 530F enters the reactor from the nozzles at about mid-height. The water flows downward on the outside of the core barrel to the bottom of the reactor. Then the flow turns upward past the fuel assemblies, removing heat from the assemblies and increasing in temperature to 590-600F. After leaving the core area, the water mixes in the upper plenum and leaves the reactor through nozzles. Flow then goes to the
Steam Generator where the radioactive Reactor Cooling System water enters at the bottom, flows through small inverted U-tubes. That water loses its heat as it passes through the tube being cooled by the non-radioactive water outside the tube. Non-radioactive feedwater enters through the nozzles at the mid-height of the steam generator at a temperature of about 425F. The water flows downward outside a wrapper sheet to the area just above the tubesheet where the water turns and flows upward past the U-tubes. The water increases in temperature and turns to steam. A moist steam at about 510-547F with pressure of 720-1005 pounds per square inch is produced. The moist steam travels upward to steam separators (chevron separators and swirl vanes) which allow 99.75% purity steam to pass of the steam generator and the remaining water is directed back to the lower part of the steam generator. The reactor cooling system water enters the steam generator at ~590F and leaves at ~ 530F. That water then flows to the
Reactor Coolant Pump which pumps the water back to the reactor.
Pressurizer is used to control the pressure in the reactor cooling system so that boiling does not occur in the reactor. The pressurizer also is used to act as a surge tank for the system taking up the level variations in the system. Heaters are installed at the bottom of the pressurizer for heating the water to 652F and 2250 pounds per square inch. Automated pressure control valves (called power operated relief valves) and safety valves, connected to the top of the pressurizer, can open to control and maintain pressure.
Secondary Systems line drawings identifying major sub-components in the non-radioactive part of the system where steam flows to the turbine, condenses in the condenser, then is pumped back to the steam generator first by condensate pumps, then by feedwater pumps. The feedwater heaters improve the efficiency of the cycle by recovering and reusing energy that would otherwise be lost. By doing so efficiency of the cycle is raised to 33%.

Courtesy ESKOM

The photo above shows the plant view from the intake basin. In the foreground is the screenhouse which conditions the seawater before it is pumped by large circulating water pumps through the condenser and back to the sea.