Chernobyl
Chernobyl Operations
Nuclear Power is defined as the process of converting water to steam by the use of nuclear Fission. The steam created then spins a turbine, which powers an alternator which converts this energy into electrical power
The Chernobyl nuclear power station, located 65 miles north of Kiev, Ukraine in a town called Pripyat (then part of the Soviet Union) began supplying power to the grid in 1977, and provided 10% of Ukraine’s power.
The Explosion
The morning of April 25th, 1986, began like many others in Chernobyl. A routine safety test had been scheduled for reactor No. 4 - a test so routine that some head Chernobyl operators had deemed it too mundane to attend.
In preparation for this test, operators begin reducing power in Reactor No. 4 and disabling its emergency cooling system. Around 2pm, the test was delayed due to the nation's power needs, and didn’t continue until 11pm the same day.
As the operators receive permission to continue with the test, the night shift operators begin to take over- operators who never had formal training on how to perform the test.
At 1:23:04, the test officially begins and an unexpected power surge occurs, and 36 seconds later an operator presses the Emergency Shutdown button to release the control rods into the reactor. The control rods jam- and 18 seconds later, the first explosion occurs in reactor No. 4. The explosion blows the 1000 ton roof off the reactor as it spews radiation.
Five minutes after the explosion, police and firemen arrived with no protective gear- never to be told that they were entering an extremely radioactive area.
Aerial view of the damage to Reactor 4. Cranes in the background show the halted construction of reactors 5 and 6
Radiation safety poster on the wall of the Jupiter Factory. The factory complex was used as a radiological test lab following the disaster.
Radiation
Immediately following the explosion The radiation levels in the worst-hit areas of the reactor building, including the control room were at an estimated at 300,000mSv/hr- providing a fatal dose in just over a minute.
Device readings were exceeding 30mSv/hr and reading “off scale”, and reactor crew chief, Alexander Akimov had received many inaccurate low readings. Because of these inconsistent readings, Akimov assumed Reactor No. 4 was still intact. He remained with his crew until morning, attempting to pump water into the exposed reactor core to cool it.
Akimov and his crew worked to manually open water valves to increase the water supply. Knee deep in radioactive water, he and his crew began to notice acute radiation syndrome on themselves. Akimov died 3 weeks later from Acute Radiation Poisoning at the age of 33.
22 years after the explosion radiation levels inside the reactor hall were approximately 34 Sv/hr – a lethal dose in 10-20 minutes.Typical dosage recorded in Chernobyl workers who died within a month was 6,000.00 mSv. A single dose of 5,000 mSv would kill half of those exposed to it within a month.
Liquidators on the roof of Reactor three. The white streaks at the bottom of the photo were due to the high levels of radiation emanating from below. (Igor Kostin)
Liquidators in helicopters prayed the area with a dust suppressant
The Liquidators
Liquidators were those sent in to clean up Chernobyl following the reactor meltdown. Their tasks included cleaning up the debris from around the reactor, construction of the sarcophagus, decontamination, road building, and destruction and burial of contaminated buildings, forests and equipment.
Figures for the number of liquidators involved vary greatly from several hundred thousand to nearly a million people. It is likely that at least 300,000 – 350,000 people were directly involved. A report by the Nuclear Energy Agency quotes a figure “up to 800,000”.
The Soviets did not have uniforms that could provide adequate protection, so those liquidators enlisted to enter highly radioactive areas were required to cobble together what they could. Some workers attached aprons made of lead sheets just 2 to 4 millimeters thick over their cotton work clothing.
Death and disability rates among liquidators soared over the years. However, health studies on them have not shown “any direct correlation between their radiation exposure and an increase in other forms of cancer or disease,” according to the IAEA. Psychological trauma from Chernobyl remains widespread and profound resulting in “suicides, drinking problems and apathy.”
Official Oversight
The Soviet Union initially denied any accusations of a nuclear accident, eventually admitting that a meltdown had occurred- but falsely stating they had contained the meltdown. It was only after 36 hours that the residents of Pripyat were evacuated. This delay in evacuation exposed residents of Pripyat to extreme levels of radiation.
The completed concrete sarcophagus
The Sarcophagus and the New Safe Confinement
In an attempt to contain some of the radiation expelled from reactor No. 4, a team of liquidators quickly concocted a structure around the exploded reactor built of metal and concrete, that structure came to be known as the sarcophagus.
On December 22 1988, Soviet scientists announced that the sarcophagus would only last 20–30 years before requiring restorative maintenance work. The Object Shelter was never intended to be a permanent containment structure. Its continued deterioration increased the risk of its radioactive contents leaking out. In 2010 it was revealed that water leaking through the sarcophagus roof was becoming radioactively contaminated before seeping through the reactor’s floor into the soil.
The sarcophagus, after 30 years, was crumbling and was covered with a new container, named the New Safe Confinement. On November 29, 2016, the New Safe Containment was slid into place around the reactor. Primarily made of steel and concrete, the New Safe Containment is an arch-like structure, weighing 1944.25 tons and measuring 843 feet wide and 354 feet tall. An incredible feat of engineering, it is expected to contain the Chernobyl reactor for the next 100 years.
The small chunk of visible corium that makes up The Elephants foot
The Elephants Foot
Discovered in December of 1986, The Elephant's Foot is the name given to a 2 ton lava-like mass of nuclear waste that lies in the basement of reactor 4. The mixture of substances in nuclear waste compiles to form something called “Corium”. The mass seen in this picture of only a small part of a much larger mass.
Following the meltdown, the intense radiation emitted from the elephants foot after only 30 seconds, would be fatal within a week. After 2 minutes, your cells would begin to hemorrhage, after 4, you would begin to vomit, and after only 200 seconds near the elephant's foot-you would have mere days to live.
As the corium continues to eat through the metal and concrete that surrounds it, it descends further into the ground- at any time it could hit groundwater- contaminating a water source.
The Exclusion Zone
The “Chernobyl Nuclear Power Plant Zone of Alienation” is the officially designated exclusion area around the site of the Chernobyl nuclear reactor disaster, 1600 miles around the plant. It is commonly known as the “Chernobyl Exclusion Zone” or simply “The Zone”.
Prior to its evacuation Chernobyl was inhabited by 16,000 people but is now populated only by Zone administrative personnel, some of those involved in decommissioning the power plants and a number of residents who refused to leave their homes or subsequently returned.
The purpose of the Exclusion Zone is to restrict access to the most hazardous areas, reduce the spread of radiological contamination and conduct radiological and ecological monitoring activities. Today, the Exclusion Zone is one of the most radioactively contaminated areas in the world and draws significant scientific interest due to the high levels of radiation exposure in the environment, as well as an increasing interest from tourists.
Moving Forward
While Chernobyl has been shut down, It has yet to be decommissioned (taken down and decontaminated). The NEA, or the Nuclear Energy Agency, will have to treat and store every piece of equipment, not only in Chernobyl, but also in the decommissioning processes- the Nuclear waste will have to be housed on-site.
Webpage by Josef Wolfgang