The steam generators are not electrical generators. They are heat exchangers that sit between the primary coolant loop and secondary coolant loops to generate clean, non-radioactive steam for the turbine and electrical generator.
The primary coolant loop pumps coolant water, which is radioactive, through the reactor itself and then through one side of the heat exchanger. This water emerges at ~315°C at a pressure around 15MPa to keep it from boiling and goes into the heat exchanger where the heat is transferred to the secondary coolant loop.
The secondary coolant loop is non-radioactive water and it is converted to saturated steam at a temperature of ~275°C at 6MPa which then drives the steam turbine before heading into another heat-exchanger linked to a tertiary coolant loop which condenses the secondary loop steam back to water.
The tertiary coolant loop at Koeberg is seawater to the best of my knowledge.
Since the steam generators link the primary and secondary loops, it means that the replacement of these is very similar to their original construction process. The existing units will have to be cut out of the plumbing system after the reactor has been shut down and cooled, then processed as nuclear waste as the primary side will be contaminated. Then the new units have to be installed, the plumbing welded to take the 15MPa and 6MPa pressures and then the whole system refilled with coolant, pressure checked and then finally taken online again.
It is a major works project and is being performed by Areva who are the group that Framatome (the original French reactor builders at Koeberg) was absorbed into. Areva has done this upgrade to a number of very similar reactors in France. These are the chaps we want doing the work.
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