What was caused by the Chernobyl accident?
It has been difficult to determine the causes of the Chernobyl accident, especially because the nuclear energy producing countries were very bad at informing each other about the experiences with nuclear power. This meant that one could not benefit from each other’s knowledge. Therefore, a wide range of eyewitness reports and experimental reconstructions have been necessary to get an idea of ?? the cause of the accident.
The background to the accident is believed to be a combination of human errors and technical defects in the reactor. According to the website www.chernobyl.info (see sources), the reactor type used by the Chernobyl engine has an error in the control rods. In a reactor, the energy level is normally controlled by lifting and lowering the control rods so that the fewer control rods that are between the core elements, the greater the power of the reactor. However, in reactor number four at the Chernobyl plant, there was a fatal mistake in this process. This meant that when the control rods were lifted and quickly lowered again, the effect was completely opposite, namely that the reactor power was increased. If “too many” control rods are lifted at one time and then lowered simultaneously in an emergency, as in Chernobyl, the energy level apparently rises so dramatically that the reactor is destroyed.
What did you do to slow the fire in reactor 4?
The first ten hours after the accident, fire extinguishers pumped cold water into the heart of the reactor to extinguish the fire and stop the discharge of radioactive materials. However, the effect was minimal. Because of the high temperatures the graphite burns, it can not be switched off with water or with chemical extinguishing media. Therefore, you had to put in more powerful shooting.
From April 27th to May 5th, more than 30 helicopters flew over the burning reactor and dropped more than 2400 tons of lead and 1800 tons of sand to quench the fire and absorb the radioactive radiation. However, this only worsened the situation. The heat was increased under the dumped materials and the temperature in the reactor rose again. This meant that the amount of radioactive radiation was increased. Therefore, the tactics had to be changed again and in the final phase of the fire extinguisher the reactor was cooled with nitrogen.
On May 6, both the fire and the radioactive release were finally under control. According to www.chernobyl.info (see sources).
How was the reactor protected against radioactive emissions?
When the reactor was covered with lead, sand with more, it was found to be sufficiently safe to encapsulate the reactor in a giant shell. A 300,000-ton heavy concrete structure was formed, which was called ‘sarcophagus’ – an old word for tombs – and in December 1986, reactor number four was completely enclosed. The sarcophagus should secure the environment against radioactive radiation for the next 20-30 years. The main problem, however, was that it was designed in hiding and hurry why there was a great risk that its skeleton in the form of 6,000 tons of metal would rust.
In 1997, the G7 agreed to implement the so-called “the Shelter Implementation Plan” with Russia, the EU, Ukraine and the European Bank. According to the website www.chernobyl.info (see sources), the plan is to construct a 20,000-tonne heavy protection shell, which must encompass reactor number four from 2008 and have a durability of at least 100 years.
Immediate consequences of the Chernobyl accident
How much pollution was released?
There is great uncertainty about how much pollution was released when reactor number four in the Chernobyl nuclear power plant exploded. Soviet scientists announced that the reactor contained about 200 tons of nuclear fuel in the form of uranium dioxide and fission products. Most experts, according to the website www.chernobyl.info (see sources), suspect that it was released between 3.8 and 20 percent of the content. Others claim that most nuclear fuel is released from the reactor. On the other hand, the Ukrainian government reports that studies of the reactor over 15 years show that 95 percent of nuclear fuel is still in the reactor.
What type of pollution was released?
When uranium nuts are split into a nuclear reactor, many different fission products are formed. This means that over 20 different radionuclides were released from the exploded reactor four. The discharge was especially high the first 10 days after the accident. According to the Wikipedia article wikipedia (see sources), the release depends mainly on the boiling point of the individual substances:
All noble gases in the reactor were immediately released at the first steam explosion
About 44 percent of the radioactive iodine was released in the form of vapors, solid particles, as well as iodine-containing organic compounds.
Cesium and tellurium were released in the form of aerosols
In addition, far more dangerous radioisotopes, such as cesium-137, iodine-135, strontium-90 and Plutonium-241, spread through dust particles into the air escape. This means that they can, for example, be inhaled and deposited in the soil via rain, whereby they enter the food chain via plants. According to www.chernobyl.info (see source