Nuclear power plants have a very valuable resource so as not to collapse if electricity fails: the “flex” strategy

The refrigeration system of The reactors of nuclear centrals It has a fundamental purpose: to guarantee that Fuel bars will remain at all times within Its operating temperatures range. If this parameter increases excessively they could melt and trigger a serious accident. To avoid it Conventional nuclear reactorslike those we have in Spanish nuclear plants, have a triple cooling circuit.

The primary circuit consists of the vessel that contains the fuel bars and a deposit known as heat exchanger. The hot water from the vessel circulates between both deposits thanks to the action of a pump, so that it cools in the exchanger before returning to the vessel. This circuit is closed. In addition, the heat exchanger acts as a steam generator, so a second circuit is responsible for introducing the cold water inside that, when coming into contact with the hot water of the primary circuit enters boiling.

From there the necessary steam proceeds to transfer to the turbine the kinetic energy that will make it possible to obtain electricity thanks to the action of the alternator. Once the fluid crosses the turbine the water steam is cooled and condenses inside an additional tank to promote the appearance of water in the liquid state that will be introduced again in the heat exchangerthus giving rise to a second closed circuit known as secondary circuit. Again a pump is responsible for the water to circulate between the condensation tank and the heat exchanger.

So far we have described two different closed circuits, the primary and the secondary, but we have left a loose end. In order for the water vapor of the secondary circuit to be condensed inside the condensation tank it is necessary to introduce in the latter cold water. And to do so it is necessary to resort to a third circuit known as external cooling circuit. The water of this last installation comes from the sea or from a river near the nuclear power plant, hence it is necessary to accommodate this type of centrals near one of these two natural resources.

In modern nuclear centrals flexibility and redundancy are everything

As we have just verified, so that the water that acts as a refrigerant element circulates correctly inside the primary and secondary circuits the action of at least two pumps is necessary, one for each circuit. And, of course, the pumps need electricity to function, like many other elements of the nuclear reactor, such as the pressor, the external cooling circuit pumps or the safety injection pumps. We explain everything in more detail in the article that we dedicate to The control rooms of nuclear centrals.

After Fukushima The safety of all the world’s nuclear power plants was reinforced. They underwent very important stress tests during which all the central parameters were reviewed, especially those that were related to what had happened in Fukushim Baskets on the electricity grid. And once everything was reviewed, the incorporation of a series of measures to mitigate and prevent such accidents was standardized worldwide. This strategy is known as “flex”, which is the flexibility apocope.

Nuclear centrals have been designed to Prevent Design Base accidents. This philosophy consists in thinking about what can happen with the purpose of implementing security measures to mitigate them in case they occur. What happens is that in practice, of course, there are accidents that you can not have planned, so in addition to the security systems prior to Fukushima, a series of portable equipment that allow all those functions from outside without having to depend on exterior power supply have been incorporated.

They are totally portable and autonomous equipment that are already incorporated into all nuclear plants, and that can also be transported from one central to another in case of need via helicopter or through the military emergency unit (UME). In addition, there are also A central warehouse in Technatom Madrid where there are portable equipment that could be transferred in two or three hours to any Spanish nuclear power plant. As we have just seen, the redundancy of the equipment is also a crucial strategy in nuclear facilities. However, there is another resource that is even more important: The security culture. The training of all people who work in a nuclear power plant is individualized and permanent throughout their professional career.

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