Physics

How do nuclear power plants work?


As already stated, to get a nuclear plant up and running requires first of all enriched uranium. To give you an idea, 0.5kg of enriched U-235 - the amount used to power submarines and nuclear aircraft carriers - is equivalent to 3.8 million liters of gasoline.

In general, uranium is formed into pellets (pill-shaped) with a diameter close to that of a coin of R $ 0.10 and a thickness of 2.5cm. These pellets are arranged on long rods grouped into bundles which are submerged in water inside a pressure vessel. Water, in turn, has the function of cooling the system.

For the reactor to work, the beam needs to be slightly supercritical. This means that if left alone, uranium would melt. So, in order not to happen, they are inserted into the beam control rods (also called camshafts or yet, control bars), which are made of material capable of absorbing neutrons, using a device that can lower and / or raise the rods.

Thus raising and lowering the rods controls the level of nuclear reactions. Therefore, when higher heat production is desired from the uranium core, the rods are raised out of the beam, while to produce less heat, the rods are lowered into the beam. In addition, the rods have other functions: lowering them fully into the beam can shut down the reactor in the event of an accident or make it possible to change fuel.

The heat released during the nuclear reaction is responsible for heating the water, which is transformed into steam. This steam triggers a turbinewhich rotates a generator, responsible for producing the energy.

In some plants, reactor steam passes through an intermediate heat exchanger to transform water from another circuit into steam, which will be responsible for driving the steam turbine. Also, in some reactors, the coolant is a gas (CO2) or liquid metal, allowing the core to be operated at higher temperatures.