This is a visual illustration of the inner workings of the reactor and the key events of
the Chernobyl disaster. The power plant had four nuclear reactors brought online over six years.
Steam turbines were located in the adjacent turbine hall.
Unit 4 had been making electricity for three years at the time of disaster in 1986.
The reactor was the RBMK 1000 type. A 1960s design and the legacy of the nuclear power
race where trying to be first meant undesirable shortcuts were made.
The propaganda was that it was a safe reactor and that could not explode which gave a false sense
of security. The uranium fuel was only slightly enriched resulting in a much larger reactor core.
Western reactors are stable by design. As they heat up the nuclear reaction slows
which is what you want. Chernobyl was the opposite where increased heat accelerated the
reaction setting it up to run away with itself. The technical term is positive void coefficient.
The pumps and steam systems which fed the turbines were paired on either side
and circulated enough coolant water to prevent overheating of the fuel.
The radioactive fuel was enclosed in a steel drum with the top and bottom lid.
This was the radiation shielding which safeguarded the plant workers.
Almost 2 000 vertical channels were arranged inside graphite bricks.
Graphite was a favored material for sustaining a nuclear chain reaction in low-grade uranium.
These channels contained the uranium fuel assemblies and the control rods.
The uranium pellets shown here in red were stacked inside seal tubes. They heated the water which
turned the turbines to produce electricity. 10% of the channels held control rods shown here in green
moving them in and out of the core did the job of the brakes and accelerator of the reactor.
The RBMK core was huge. This is the relative size of the Fukushima core which is 17 times
smaller. Chernobyl had rudimentary containment.
Here it is compared to the Japanese Fukushima reactor housing to the same scale. Fukushima had
three containment layers, the pressure vessel a steel lining and the outer concrete layer.
The Chernobyl reactor had just the one layer. The reactor was serviced from the reactor hall above.
Refueling could be done while the plant was at full power. This is a big advantage of
the RBMK design but was only possible because there was no pressure vessel.
This can be likened to driving without a seatbelt which is convenient but not wise.
The control room is located outside the reactor building in the lower levels of the turbine hall.
It is accessed from the golden corridor that connected all units and was 600 meters long.
It is ironic that this reactor blew up while testing if the reactor was safe. The control staff
were under pressure to get the test done because the next chance for the test would be in a year.
It is unthinkable that activating the emergency shutdown detonated this explosion.
A design quirk meant the shutdown mechanism briefly spiked the reaction before slowing it.
In certain low power configurations this is enough to send the reactor supercritical in seconds.
The design fault in the AZ-5 shutdown system was not communicated to the Chernobyl controllers.
The chief engineer bypass multiple automated safety systems.
Vast amounts of radiation were released directly into the atmosphere. Radioactive fuel debris
lay strewn all around the site. Large areas of Belarus and Ukraine were made uninhabitable. The
finest radiation was carried much further and detected in low amounts across Europe causing
widespread fear and panic. The reactor lid which weighed 1 000 tons was blown up through the roof
and landed back in the reactor pit on its side. To seal the radiation outflow to the outside world
an emergency concrete and steel cover was built in a hurry in just 200 days.
They called this shield the sarcophagus. It was built in heroic circumstances and never meant
as the final solution. The cleanup activities at Chernobyl was bravely done by as many as
500 000 people called liquidators most were simply told to be there uncertain how it would
impact their life expectancy. They were waging a war against an invisible self-inflicted enemy.
Large quantities of equipment were involved and abandoned after because of contamination. 30 years
later the shield was rusting and cracking and leaking radiation. It was at risk from extreme
weather and was going to collapse sooner or later. A new permanent containment arch was constructed
a safe distance away and rolled in place on rails in November 2016. The iconic Chernobyl ventilation
stack was in the path of the new cover and was taken down and replaced with the smaller one.
This new permanent cover is a success story of international cooperation.
It took 15 days to slide the new arch in place. It is the largest movable land structure ever made.
Finally the air we all breathe is properly sealed off and safe from this nuclear menace.
The arch has equipment for dismantling and decommissioning this atomic nightmare.
Chernobyl was the result of a flawed reactor design and the erosion of safety culture.
The fundamental failings of the Soviet system were laid bare at Chernobyl. The Soviet Union
unraveled soon after. Ukraine was left to carry this burden of historical proportions.
The rest of Chernobyl's reactors continued to run after the disaster. Unit 2 burned
in 1991 and was abandoned. The last reactor was switched off in 2000 after European insistence.
Russia to this day still operates 10 RBMK reactors at three locations and plans to
run the last one till 2034. These units were retrofitted with safety modifications.
This is the ghost town of Pripyat. It was a model town of 50,000 where the power plant staff lived.
It was a privilege to work and live here. In many ways it was a Soviet dream until it was evacuated
in one afternoon the day after the explosion. Countless lives were devastated here forever by
this tragedy. The Chernobyl nightmare that dragged on for so long finally has a workable long term
plan. But the cleanup will still run for decades. The Pripyat amusement park was days away from its
mayday opening. It was hastily opened early as a diversion for residents concerned about the
obvious damage to the power plant which would have been visible from the top of the ferris wheel.
Later in the day they were instructed to evacuate for three days unaware they would not return.
We hope you found this useful and enjoyed the visuals. If there is interest we plan
to make further videos on detailed aspects of the Chernobyl and nuclear power in general.