The use of nuclear energy is one of the most debated issues in recent years, especially after what happened at Chernobyl. A tragic event that will remain marked in history as one of the most serious to date. The reasons for this nuclear disaster served to prevent other situations similar to the Chernobyl accident from happening again. But what happened in Chernobyl and what were the causes of this catastrophe?
What happened at Chernobyl?
It was after one in the morning on April 26, 1986 when Reactor 4 of the Chernobyl nuclear plant exploded. In the middle of a failed drill, the plant operators did everything possible to deactivate the reactor moments before the explosion. However, all the countermeasures that were carried out were of no avail, as it was too late.
It only took a few seconds for two explosions to be generated that happened consecutively. The first gave off a huge amount of steam, while the second exposed the core of the reactor. A strong fire broke out while huge amounts of graphite and nuclear fuel were scattered outside.
Graphite was used as a regulator within the reactor core, however its radiation levels are extremely high. The consequences of the Chernobyl accident caused the death of at least thirty people between operators and rescue personnel. In addition, during the event, another 350,000 were evacuated from the areas close to the tragic event.
As if that were not enough, more than two hundred square kilometers were completely contaminated. This not only affected people’s health, the environment was also seriously harmed. A huge cloud of radioactive dust spread to a part of Europe, as well as other regions further afield.
Even after 30 years, the Chernobyl accident continues to generate buzz as its consequences still persist today. A terrible combination of human error and an unsafe reactor design started the greatest nuclear disaster of all time.
What were the causes of the Chernobyl accident?
The use of a reactor designed with almost zero security measures and the lack of compliance with the standards established by the operators. These were the main reasons for the Chernobyl accident, a region belonging to the former USSR. However, first you have to know what kind of reactor 4 was and what were the mistakes made by the operators in this disaster.
Reactor Design
It is a reactor known as RBMK that works with about a thousand electrical Megawatts, this, in turn, is regulated with graphite. Large amounts of light water stored in huge tanks are used as a cooling method. Said reactor had two functions, the first was to generate electricity, while the second was to produce plutonium 239. The latter was necessary for the production of large batches of highly dangerous weapons.
Now, the core of a RBMK type reactor tends to be unstable when it works at a level lower than 700 megawatts. In other words, it is often almost impossible to control at low power, making it vulnerable to chain reactions. It is precisely this characteristic that makes RBMK reactors so dangerous.
It should be noted that the Chernobyl accident occurred when the reactor was at low power. Which means, the chances of it becoming unstable were terribly high and still, the test was carried out.
The process of inserting the safety bars in such a reactor is really slow, taking at least 20 seconds to complete. Other reactors with different designs only need two seconds to stop their functions instantly. So during a crash where the kernel becomes unstable, 20 seconds was enough time for the disaster to start.
On the other hand, the safety bars of an RBMK reactor are made of boron carbide, while the cover is made of graphite. Once the rod insertion process begins, the graphite dramatically increases its reactivity. This feature was discovered in 1983, just three years before the Chernobyl accident. As if that were not enough, these reactors lack a filtration system to prevent gases from escaping. Worst of all, is that they do not have a containment structure, an elementary security requirement.
human error
After learning about some of the fundamental failures in RBMK rectors, now it’s time to discover the failures of the operators. Among these errors, at least six are directly related to the Chernobyl accident. Two mandatory rules were violated by these operators during the test. Never operate this type of reactor if power levels are below 700 megawatts. The number of security bars fixed in the core must never be less than thirty, the operators only left eight inserted.
Among the numerous failures on the part of the operators, is that of not following the safety procedure stipulated in the regulations. In addition, three other security measures were recklessly and willfully bypassed. One of these was the activation of the emergency cooling process. The others have to do with the shutdown of reactor functions in cases of emergency.
Investigations revealed that the operators in charge of reactor four lacked the necessary experience and training. For this reason, neither could understand the situation that was unfolding before their eyes, and their actions only accelerated the Chernobyl nuclear disaster. If the aforementioned failures had not been carried out, the explosion of reactor four would never have occurred.
Undoubtedly, the operators bear much of the responsibility for what happened, since they worked with the training they received. This was not enough, especially if one takes into account the characteristics in the design of a RBMK reactor. Not knowing how the core works, the operators were not able to make the right decisions given the situation. Bearing in mind that the reactor operated at low power without complying with the corresponding security measures.
A test that would start with a low power of 700 MW, would drop sharply to 500 and then 30 megawatts. With some actions, the operators managed to barely reach 200 MW, however, they still did not achieve the figure stipulated at the beginning. Instead of stopping all operations and giving the test as failed, the operators decided to continue with it. The reactor suddenly reached 33,000 MW of power when its maximum power was only 3,200 MW. After this, the first explosion occurred and immediately afterwards, the Chernobyl nuclear disaster.
other causes
During the Cold War, the countries of the former USSR needed to produce large amounts of plutonium for the manufacture of weapons. One of the fastest, but insecure ways to achieve this, was through the construction of RBMK reactors. In this sense, the funds that were available for the mass production of plutonium 239 were used. Said material had to be the highest quality possible and in the shortest time.
The former USSR was known for its internal secrecy, which is why they ignored external advice. They only cared about what could bring them some profit, so they built these reactors without paying attention to safety measures. For this and other reasons, the Chernobyl accident can be considered a situation that could have been avoided.
What is the chance of another Chernobyl-like accident happening?
At present, there is very little chance of another situation like the one experienced in Chernobyl more than thirty years ago. The reason for this is that the operation of modern reactors has nothing to do with that of an RBMK used in the former USSR.
First of all, if any abnormal situation occurs inside the reactor, it stops automatically. Additionally, the insertion of the security bars only requires 2 seconds to complete. Which means that they are safer in highly dangerous situations.
Also, modern or western reactors as they are also known, have a safer design. Unlike the RBMK reactors, the western ones do have a containment structure. While the control rods and the core do not contain any element of graphite or any other component that could be flammable.
The Chernovyl accident will be remembered throughout history as one of the most serious for humanity and the environment.
Sources:
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