A Little History
It was April 25th 1986, and the technicians working in Reactor 4 were in the process of preparing the reactor for shutdown, so that maintenance could be performed on the reactor and various performance tests could be exacted. The head of the maintenance operation decided to test the efficiency of the fail-safe systems, making sure that the reactor could generate enough electricity to power up the safety protocols preventing a meltdown of the reactor. The reactor itself was an RBMK-1000 model which required water to be continuously circulated through the core, in order to cool down the nuclear fuel and prevent any accidents.
The plant's reactors themselves had back-up generators as a precaution, though it would take 40 seconds for the generators to power up to full speed in case of an accident. Nevertheless, the maintenance team went ahead with the preparation, as they felt they could react in time lest something go wrong, despite a test run already coming up negative. The reactor output (in other words, the amount of electricity the reactors produced) had been gradually reduced to 50% causing a regional power generator to go offline. This was an unexpected complication for the team, as they had not projected that this would happen. Nevertheless, it wasn't a massive setback so they continued with the test. The grid controller at Kiev furthermore requested that the team stop the reduction of the output rate, as they needed electricity for rush hour and the like in the evening. The plant director agreed and postponed the testing, and left a skeleton crew to watch over the plant during the night. The crew itself had very little experience when it came to these types of tests, and were indeed insufficiently advised concerning reactor safety, this was one of the main factors responsible for the meltdown, yet the worst was still to come.
The crew were unaware of the postponement of the reactor shutdown, whether it be through communications errors or simple incompetence. They therefore followed the original test protocol that had been planned out prior to the decision to postpone the testing. This meant that the power level supporting the safety protocols that safe-guarded the reactor were decreased too rapidly, leaving the reactor incredibly vulnerable. The reactor started to produce more nuclear toxins (Xenon-135) which further dropped the power output, further endangering the integrity of the reactor core. The operators, through sheer inexperience simply believed that this was a malfunction in the automated power generators and not because of reactor poisoning. They then decided to try and increase the productivity of the reactor by extracting the control rods from the reactor's core.
Then came the day of the experiment itself. Officially, we know that it started at 1:23:04AM on the morning of April 26th. Through what was possibly an equipment malfunction, the unstable state of the reactor did not show on the control panel, therefore the team were unaware of the fact that there was something wrong. The steam leading to the turbines was then shut off, and the water cooling the reactor decreased in flow. The turbine was further disconnected from the reactor, which in turn increased the amount of steam contained therein, heating up the core. The reactor had an elevated void coefficient (the rate at which a nuclear reactor can change as steam bubbles form in the coolant) and the reactor started to become unstable.
At 1:23:40 AM the team noticed that something was going wrong and ordered an immediate shutdown of the reactor, re-inserting the control rods into the reactor core. The emergency shutdown was known as a SCRAM and Anatoly Dyatlov, who was the deputy chief engineer of the plant further stated in his book Chernobyl, How did it Happen? :
Prior to 01:23:40, systems of centralized control … didn't register any parameter changes that could justify the SCRAM. Commission … gathered and analyzed large amount of materials and, as stated in its report, failed to determine the reason why the SCRAM was ordered. There was no need to look for the reason. The reactor was simply being shut down upon the completion of the experiment.The mechanism that inserted the control rods was incredibly slow, which in turn reduced the amount of coolant generated around the reactor, meaning that the emergency shutdown increased the reaction rate. At this point, nothing could be done to reverse the effects. A massive energy surge fractured several of the control and fuel rods, making it impossible to shut down the reaction. The reactor then suffered an immense steam explosion which blew the lid off of the reactor. The sudden surge of oxygen in the reactor then sparked a fire and the reactor exploded.
Crisis Management
Due to the fact that the crew were unaware of the immensely high radiation levels contained within the reactor itself, they performed several severe miscalculations. In the reactor building, the worst hit areas contained up to 20 000 Roetgens per hour (500R/h is a fatal amount). Nevertheless, a geiger counter measuring up to 1000R/h was unavailable at the time, due to the Soviet economy decline that the 80s experienced. The Geiger counters that were being used at the time read off-scale levels of radiation, therefore the crews only knew that the radiation contained in the area was somewhere over 3.6R/h. Alexander Akimov, the crew leader assumed that because of these low readings, the reactor was still intact, ignoring the fact that there was massive chunks of debris lying all around the reactor. Another Geiger counter was brought in, and read accurate readings, but they were assumed to be defective and the readings were disregarded. Akimov and his crew therefore stayed in the reactor building, and were dead three weeks later from radiation poisoning.
After the accident, several firefighter crews arrived at the scene, but were not told of the severity of the accident or of the nature of the accident; they assumed that it was a simple electrical fire, and therefore were in the dark about the toxic radioactive materials they would be handling. By 5AM the fires on the roof of the plant were extinguished, and the crew focused their attention on the fire in the reactor. They decided to try and drop sand, boron, lead and clay into the reactor in order to try and smother the fire. This did nothing, and in fact further fueled the fire. This can be evidenced by looking in the underbelly of the reactor; large lava flows were created thanks to the superheated material.
Pripyat was then evacuated. The residents were told that the evacuation would only be temporary. This means that you can still see many of the personal belongings of residents still in the city today. Having said that, many people have taken to looting, despite government warnings.
The liquidators were then sent in to assist in the clean-up. I have nothing but the utmost respect for these men; they were volunteers and they knew precisely what they were getting in to. Teams would work for up to two minutes each, running across the plant roof and clearing a small piece of debris off, then running back to safety. Hundreds of these men died not long after, all that remains of them is a large vehicle graveyard on the outskirts of the Zone, and a monument to their bravery in Chernobyl itself.
Aftermath
Since the fatal experiment, Chernobyl has now become an internationally recognized symbol for the fight against nuclear proliferation. Many countries were affected by the explosion, and still are to this day.
One would expect Chernobyl and the 30km disaster zone surrounding it to be completely barren of life, though this couldn't be further from the truth. Ukranian authorities are reporting a surge in the Elk population, a species which were dwindling before the disaster, and it also appears that there are no serious mutations among animals except a slightly elevated cancer risk for mice.
The reactor core itself is still probed and explored by several scientists, trying to find out where the nuclear fuel went after the explosion. Ironically, they have suffered two deaths from heart related problems. One would expect radiation to be the culprit.
There are still problems though; the sarcophagus surrounding the reactor is slowly crumbling. Plans have been made to construct another sarcophagus around the reactor, but due to lack of funding this has been delayed. If the sarcophagus were to crumble, another accident could happen, resulting in another release of toxins into the air, which could affect many countries in Europe, such as Belarus, a country which already has an elevated child deformity rate as an direct cause of the radiation. In fact there is an orphanage in Belarus itself housing many children with mental deficiencies and Leukemia. Many people visit this place on their way to Chernobyl, to help the children and donate money to the orphanage.
Other than that, what's to say? It's easy enough to get into the Zone itself. It's an interesting place, regardless of what happened there.
Peace
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