Spanish nuclear have been criticized for their role in the blackout. This was what they did before, during and after collapse

On April 29, just a few hours after Total collapse of the electricity grid Spanish, Pedro Sánchez, the president of the Government of Spain, He made these statements: “Citizens should know that during this crisis nuclear power plants, far from being a solution, have been a problem Because they were turned off. And it has been necessary to divert large amounts of energy to maintain their stable nuclei. At this time there are two nuclear centrals activated, and they are not because they are needed, but because their activation was already planned. “

His words require several nuances if we want to know in some detail what was the role of Spanish nuclear facilities in this incident and what they did before, during and after the total blackout. The first thing is worth repairing is that only three of the seven nuclear reactors of the Spanish park were turned off: the Trillo because the technicians were recharging fuel barsand those of Almaraz I and chests due to the needs that the electric market had at that time.

The other four nuclear reactors, those of Almaraz II, Ascó I and II and Vandellós II, were operating normally before the blackout occurred. If we have this present the statement of Pedro Sánchez in which he argues that “(…) nuclear power plants, far from being a solution, have been a problem because they were turned off (…)” is not right. As we have just seen, Four reactors were delivering electricity to the network with total normality. In any case, the most interesting is what happened just when the collapse occurred.

Security systems went into action to guarantee a safe stop

Nuclear reactors are prepared to stop fission reactions whenever. The procedure that is used, very broadly, consists of introducing the control bars in the active section of the vessel, which are made of metal alloys of boron, cadmium or hafnio because these chemical elements have the ability to absorb a large number of neutrons. Fission reactions stop very quickly thanks to the effect of control bars, but, and this is very important, nuclear reactors have a great thermal inertia.

This simply means that once the flow of neutron has stopped completely the reactor continues to generate residual heat due to the disintegration of products derived from nuclear fission. The main consequence of this behavior is evident: It is essential to sustain core cooling of the reactor even although this machine has stopped by introducing the control bars and modifying the composition of the refrigerant By adding boric acid to the primary circuitwhich also has a very high index of neutron absorption.

Active and passive cooling systems have to ensure that residual heat does not compromise the integrity of the reactor, and, curiously, thermal inertia can last even for several days. When on April 28 there was the collapse of the Electric Red the four reactors that were in operation were automatically stopped and the security systems that have been designed to hold a safe stop were activated.

The first thing that happened was that autonomous diesel generators started automatically and generated the electricity that was necessary at that time to keep the entire installation on a safe stop. Everything was executed as planned according to the Nuclear Safety Council. A few hours later, when the supply of electricity from abroad resumed, the autonomous diesel groups were disconnected and the emergency plan was deactivated.

From that moment on, nuclear centrals have been resuming the production of electricity, although before doing so the technicians have carried out the security checks that are necessary. An important note once we have reached this point: the recovery of the activity of nuclear power plants and their synchronization with the electricity grid are carried out as the system operator, which is Red Eléctrica de España, and the electricity market requires it. A week after the total blackout we have no solid reason to conclude that Spanish nuclear power plants have put us in danger.

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