The diagram provided depicts a specifically designed man-made process to create steam using a gas cooled nuclear reactor.
Overall, the production of steam requires both a reactor as well as a separately heat exchanger. The nuclear reactor contains uranium fuel elements, covered in graphite moderators, which produce heat. In addition, boron control rods and charge tubes for loading fuel elements are at the top of the reactor, which is shielded in concrete.
The cyclical process of steam production starts with the uranium’s hot gas exiting the reactor through ducts. The hot gas generates steam which flows into a turbo-alternator. As a result, electricity is produced through thermal energy.
In order to avoid the reactor from overheating the hot gas flows down into a heat exchanger. In order to cool down the hot air the system circulates water. Then, the cool gas is introduced into the reactor through a gas blower so as to reduce the heat.