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The function of the steam generator is to transfer the heat from the reactor cooling system to the secondary side of the tubes which contain feedwater. As the feedwater passes the tube, it picks up heat and eventually gets converted to steam. The steam generators may also contain a steam separation region, described below.
![Picture](/uploads/2/4/5/4/24542517/6646454_orig.gif)
The horizontal steam generators have horizontal tubes as shown to the right. Reactor coolant flows through the tubes. Feedwater is supplied outside the tubes and is converted to steam that flows up into the header. During refueling outages, the steam generator tubes are inspected for degradation and thinning using a non-destructive examination method known as eddy current testing. Probes as the one shown below are routed through the tubes and signals from the sensor are evaluated using a computer. The probes are used to find defects in the tubing material. If defects are found the tube may be plugged or have a sleeve installed to strengthen the tube.
![Picture](/uploads/2/4/5/4/24542517/9754498_orig.gif)
The function of the steam separators is to remove the water from the steam. This is done to ensure that the steam impinging on the turbine blades causes minimal erosion. The blades are large and steam laden with water can cause severe erosion and wear of the blading. So also can the presence of chemicals, e.g. silica, in the water that is converted to steam.
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