On February 28, 2022, just four days after the start of The Russian Invasion of Ukrainethe country’s troops led by Vladimir Putin bombarded the vicinity of The Zaporiyia nuclear power plantlocated in the southeast of the country. Shortly after, during the night of March 3 to 4, the Ukrainian and Russian soldiers They fought together with the buildings of this nuclear installation. This scenario has been repeated several times since then, which has represented at some times a threat to the integrity of the nuclear reactors of this central.
Unfortunately, the Ukraine War is not the only war conflict that has endangered one or more nuclear facilities. During the last five decades Israel has repeatedly bombarded Iraq nuclear plants, Syria and Iran with the purpose, according to the Israeli government, to prevent these countries from developing nuclear weapons. This is the same scenario as presumably triggered The last episode of the conflict between Israel and Iran on June 13. However, not all nuclear facilities are the same.
Israel and the US argue that the plants of Fordo, Isfahán and Natanz, all in Iran, who have recently bombarded several thousand Uranium centrifugers. These machines contain uranium hexafluoruro (UF₆) inside, a corrosive gas that if it came to filter to the environment could trigger a radiological and chemical emergency, although there would be no nuclear explosion. In any case, in this article we propose to explore what would happen if one missile or other large -capacity projectile impact on the building of a nuclear reactor.
Nuclear reactors cannot explode as an atomic bomb
Nuclear centrals in operation used by many countries to generate electricity have been designed to offer A very high security level and hold your operation over time. The first protection barrier that nuclear reactors have external threats is the containment enclosure. This concrete structure is watertight and is designed to keep the primary circuit of the environment completely isolated (we will immediately see what this circuit consists of).
This framework is designed not to be degraded by dilation, to support the energy of an earthquake, and even to resist very important collisions, such as the impact of an airplane. However, in addition to protecting the nuclear reactor from external aggressions, it is responsible for preventing the radioactive material to be lodged in the primary circuit Remove and get in touch with the atmosphere. Anyway, the first thing that a missile or a pump would have to damage to damage a nuclear reactor is to destroy, or, at least, penetrate the containment enclosure.
The containment enclosure is designed to withstand very important collisions, such as the impact of a plane
The other element of the installation that has a crucial role in the proper functioning of a nuclear reactor is the cooling circuit. Although, in reality, a nuclear reactor works side by side with three different circuits. The primary circuit consists of the vessel, which is the deposit that contains Fuel bars and the water that must remain in contact with them to absorb their thermal energy; For the heat exchanger, which is a second tank to which the hot water comes from the vessel; and by a pump that facilitates the circulation of water between the vessel and the heat exchanger.
The primary circuit must be closed because the water it contains being in direct contact with the fuel bars is contaminated. And therefore, It is radioactive. The heat exchanger acts as a steam generatorso a second circuit is responsible for introducing the cold water inside that when it comes into contact with the hot water of the primary circuit, it enters the 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 vapor cools and condenses inside an additional tank to promote the appearance of water in a liquid state that will be introduced again in the heat exchanger, thus 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 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. The thermal energy exchange that occurs between these circuits allows us to obtain the electrical energy we need, which is the ultimate goal of nuclear power plants, but also seeks to keep the fuel bars housed in the reactor core within its optimal range of working temperature.
The most serious scenario implies the fusion of the reactor core
If the thermal energy generated by the fuel material of the fuel bars as a result of the sustained fission over time exceeds, for whatever reason, the capacity of the refrigeration systems of transporting that energy and maintaining the core of the reactor within the optimal range of working temperature, the fuel could be degraded. And if this happens, it could happen from the solid state in which it is initially to the semi -solid state, or even a liquid state.
This phenomenon is known as the fusion of the nucleus, and can cause a part of the radioactive material to end up coming out of the vessel. This was, in broad strokes and without entering the causes of the accident, which happened In Chernobil reactor 4 In 1986, but There are very important differences between the nuclear power plant that suffered that terrible accident and the plants in operation currently. And one of those fundamental differences is that the reactors of the Chernobil Central lacked containment enclosures.
The scenario posed
As we have seen, one of the primary tasks of the containment enclosure is to prevent the radioactive material from being exposed to the environment if a serious accident occurs in the reactor’s core and merges partially or totally. The number 2 reactor of the US plant Three Mile Islandhosted in Pennsylvania, it was partially melted in 1979, and thanks to the containment building its consequences were infinitely less serious than those unleashed by the Chernobil accident.
In any case, the nuclear power plants in operation have redundant and auxiliary systems that pursue minimize as much as possible, on the one hand, that an accident occurs, and, on the other hand, its harmful effects if it finally occurred. However, it is evident that the scenario it raises an external aggression of a war nature It can be very different from the one triggered by an accident caused by a technical failure or a human error. It is absolutely reasonable that some people are concerned about the consequences that the direct impact of a missile on the containment enclosure of a nuclear reactor could have.
So that something like this triggers a catastrophe similar to that of Chernobil, the external agent must be able to partially or totally damage the containment building. And, as we have seen, it is not simple because it is designed to withstand extremely violent impacts. In addition, it would also be necessary for the elements of the primary circuit, such as the vessel or the heat exchanger, to be affected. Or that the secondary circuit or the cooling circuit were seriously damaged.
Even so, if these damages occur, depending on their reach we still have a last containment barrier, and it is one of the most important: the operators of the control room of the nuclear power plant. And they have at their disposal auxiliary systems and other resources that can help them contain the impact of damages. If it is triggered The worst possible scenario And the containment enclosure, the cooling circuits, the auxiliary systems, and, in addition, the operators of the control room did not have a margin of action, a nuclear accident similar to that of Chernobyl could be produced.
Even so, the reactor would not exploit as an atomic bomb in any case because the uranium of nuclear plants It is enriched between 3 and 5%and atomic bombs require 90%enriched uranium. Or plutonium, and even a second stage with deuterium and tritium if it is a thermonuclear device that combines fission and nuclear fusion. However, in these last pumps uranium or plutonium is only used in the fission stage, which acts as a detonator of the nuclear fusion.
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