In May 2021, a report of a possible reignition of the Elephant's Foot under Chernobyl sent people into a panic. Why is it still possible that it could reignite after so many years? Because scientists found that the Elephant's Foot chamber had been soaked with rainwater.
What are the "elephant's feet" under Chernobyl? Why did the rainwater cause the Elephant's Foot to reignite? What are the terrible things that can happen when it reignites? What should we do?
Today we will learn about the melted core under Chernobyl, which looks like an elephant's foot, and we must be alert to the possibility of its reignition.
To talk about the "elephant's foot" under Chernobyl, we have to start with the Chernobyl incident. The Chernobyl nuclear power plant incident occurred in the early hours of April 26, 1986, when Ukraine was still under the rule of the former Soviet Union.
The nuclear reactor accident was the worst nuclear power plant accident in history, causing approximately $200 billion in damage, second only to the damage caused by the Fukushima nuclear power plant accident in Japan.
At that time, engineers were preparing to perform regular maintenance and testing at Reactor 4 and to check the safety systems of the power supply reactor.
As a result, it was not expected that the condensate in the pipe would back up under the dangerous operation, and under the high temperature of thousands of degrees Celsius in the reactor, the condensate turned into a large amount of steam. The pressure increased rapidly, causing the steam to explode and the top 2,000-ton cap was blown off.
Due to the failure to make proper treatment in time, a second explosion occurred when the core was exposed and reacted in the air, which subsequently triggered a fire and a large amount of nuclear fuel washed overhead, spreading radioactive material rapidly around the area.
The radiation dose released from this accident was more than 400 times the radiation dose released from the atomic bomb explosion in Hiroshima, Japan. You can imagine how much impact this accident had.
According to statistics, more than 31 people died on the spot, most of them were rescue workers and firefighters. This is because they were not aware of the radioactive substances that permeated the accident site. More than 200 people were exposed to severe radioactive radiation after the incident.
As a result of the ongoing damage caused by radioactive radiation, 60,000-80,000 people died one after another over the next 15 years, and more than 100,000 people were forced to leave their homes or even spend their entire lives suffering from diseases caused by radioactive radiation as a result of this accident.
Construction of nuclear sarcophagus
But, would you believe that this exposed nuclear fuel on the surface is only 5% of the entire core. To prevent the remaining 95% from melting through the foundation at high temperatures and seeping into the underground water veins.
More than 400 coal workers risked their lives for 45 days to dig a 168-meter-long tunnel underground and build a cooling layer.
To stop the continued spread of radioactive nuclear contamination, the Soviet Union relied on a cooling layer to build a nuclear sarcophagus 108 meters high, 250 meters wide and 150 meters long. The entire covered volume of 740,000 cubic meters was not built until November.
Melting the core "elephant foot"
As feared, the remaining 95% of the nuclear fuel melted the core at ultra-high temperatures after the reaction, melting the concrete, wrapping up large amounts of dust and sand, etc., and eroding all the way down, though it cooled and solidified in the basement under the influence of the cooling layer.
The rescue team came underground six months after the incident, and in a remote camera they saw a pipe near corridor 217 with a solidified lava in the shape of an elephant's foot.
This substance is known as Crem, when the rescue team found that the radiation around this "elephant's foot" value reached 12,000 roentgens per hour. The intensity of the radiation from the reactor explosion reached 30,000 roentgens at the time, and according to scientists' calculations and speculations later, the radiation would slowly decrease in intensity in the days following the event.
In the first seven hours, the radiation level will drop 10 times, and then after seventy-seven or forty-nine hours, it will drop ten times again, and so on. But the "elephant's foot" after six months still has such a high level of radiation, which is no way to let people close.
Because 500 roentgens of radiation will be enough to make a person in an hour rapid death. But in order to get the relevant data, the rescue team still managed to take off a part of the "elephant's foot", back to the laboratory analysis.
The result of the analysis is that the "elephant's foot" has cooled and will not spread underground, but this does not mean that the radiation is no longer there, it is still releasing nuclear radiation.
"Elephant's Foot" rekindled
Since the nuclear sarcophagus built at that time was not very secure, although it was said at the time that it would probably last 20-30 years, the experts involved in the design and construction of the nuclear sarcophagus, Artur Konev, were still very worried. After ten years of wind and water, the nuclear sarcophagus may not be able to cover the nuclear radiation.
In the fall of 1996, after calculating the dose of radiation from Elephant's Foot, he thought he could look deep underground. Here he took a picture of Elephant's Foot, which was leaked in 2013. But this photo is frightening because Elephant's Foot is clearly burning.
Although when a New York Times reporter interviewed Atul in 2014, he explained that most of the flames presented in this photo were due to the long exposure he used when shooting. In the weak light of the flashlight, this is the appearance of burning. But it is certain that the temperature near the "elephant's foot" is still very high, indicating that it is not completely extinguished.
And over the years, the "elephant's foot" has obviously been eroded by rainwater, the nuclear sarcophagus is built using concrete, rainwater can easily react with the "elephant's foot", leading to the possibility of its rekindling.
- How does rain react with "elephant's foot"?
It is important to understand that the radiation level in the Elephant's Foot is decreasing because the concentration of neutrons in it is gradually decreasing. The neutrons released from the uranium material move very fast and it is difficult to produce a chain reaction, so in a dry environment, the "elephant's foot" may still be safe in the basement.
In nuclear power plants, it is generally necessary to slow down the neutrons and the nuclear uranium nucleus undergoes a chain reaction, which is when the neutron reducer is used. The ones that can make the neutron speed lower are heavy water reducers, graphite reducers, light water reducers and platinum slowing agents.
The elements in rainwater are similar to heavy water and light water, that is, the hydrogen atoms in rainwater have the same mass as neutrons. When the rainwater is immersed in the "elephant's foot" room, it can act as a decelerator.
To avoid this, engineers chose to spray a solution of gadolinium nitrate, which absorbs a large number of neutrons, with a chain reaction with the uranium nucleus. To avoid this, the engineers chose to spray gadolinium nitrate solution, which can absorb a large number of neutrons. 1990, because of a heavy rain, the nuclear sarcophagus seeped into the rain, when an engineer stared at the nuclear radiation into the spray gadolinium nitrate solution.
Although automatic spraying equipment for gadolinium nitrate solution was installed at the back, the possibility of the "elephant's foot" reigniting was discovered in 1996.
In order to prevent the nuclear sarcophagus from being unable to withstand the radiation generated by the reignition of the Elephant's Foot and to increase the barrier to rainwater, a larger shield was built in 1998 to protect the nuclear sarcophagus.
This protective cover took more than 20 years to build, but there is a situation is that when the construction will inevitably let the rain infiltration, so that the "elephant feet" room began to become wet.
Although the constructed protective shield blocked the rain outside, the water molecules inside the protective shield were difficult to evaporate. The equipment for spraying gadolinium nitrate solution has no way to deal with the water seepage in the basement, thus causing these water molecules to be trapped in the ground.
In 2021, monitoring data from the Elephant's Foot room shows that the neutron concentration in the room is already twice as high as it was four years ago. If this is left unchecked, there is a risk that Elephant's Foot will break out again, and a new round of nuclear radiation will hit the land again.
When a nuclear leak occurs, what is generally produced is ionizing radiation, which is extremely lethal and makes us very weak in the face of ionizing radiation.
In addition to the Chernobyl nuclear power plant accident, there have been many other nuclear leaks around the world, both large and small. We are most familiar with the Fukushima nuclear meltdown in Japan, which resulted in a large number of casualties in every meltdown.
And the damage of ionizing radiation to people is lasting, as described in the article, the ionizing radiation generated by Chernobyl made tens of thousands of people, who suffered from diseases for the rest of their lives.
The greatest damage caused by ionizing radiation to the human body is DNA damage of varying degrees. However, when there is too much DNA damage, it can cause chromosomal aberrations. In severe cases, cells die on the spot. Even a slightly better situation can cause cells to develop into cancer cells, and many people who have suffered from ionizing radiation have ended up dying of cancer.
If we are unfortunate enough to be exposed to strong ionizing radiation, we must protect ourselves promptly and quickly by evacuating the contaminated area as soon as possible, taking good personal protection, washing our hands and bathing regularly, going to the hospital for regular checkups, etc.