Hurry up, this is Chernobyl - not a walk in
a park. The radiation is very high, we have
to find shelter, follow me!
Wow you look really radiant today. Welcome
to the reactor 4 of the Vladimir Ilyich Lenin
Nuclear Power Plant or simply Chernobyl Power
plant. We are in the former Ukrainian SSR
close to the city of Pripyat, city of Chernobyl
and only 16 kilometers or 10 miles from the
Belarus border. Here on the 26th of April
1986 – on Saturday two seconds before 1:24
AM one of the worst nuclear disasters happened.
Actually the disasters reaching maximum severity
on the International Nuclear Event Scale were
only two in the history of mankind - This
and Fukushima in Japan in 2011. Chernobyl
plant began to be built in 1970 along with
the mentioned city of Prypiat, where the workers
lived and where – fun fact – the average
age of people living there was 26 years old.
Chernobyl had 4 RMBK-1000 reactors that together
produced about 10% of Ukraine's electricity
The last one of them - reactor No. 3 was shut
in 2000 so Chernobyl despite its “problems”
had quite a run. There were two more reactors
- No. 5 and No. 6 – that were under construction,
but were eventually cancelled in 1989. RMBK
stands for reaktor bolshoy moshchnosti kanalnyy,
"high-power channel-type reactor" and is a
solely soviet faulty design. It would be impossible
to build this in any other place that had
any regard for human life. But the soviet
doctrine since WWII was “nas mnoho” – “there
is plenty of us” – basically meaning that
people are disposable, only the final effect
counts. RMBK is a reactor where graphite acts
as a moderator. Each of them produced 1000
megawatts of electric power. The main difference
between this reactor and those used in the
West or on the good side of the iron curtain
is the fact that they were low-budget, used
cheaper low enriched uranium. Some could even
run on natural uranium. RMBK has control rods
that had a design flaw. This control rod had
two parts – one made of boron to decrease
chain reaction, and one made of graphite to
increase it. It played a key role in the disaster.
Basically it is as if you had your car’s
brake and acceleration in one pedal. To brake,
you had to accelerate for a second. And Soviets
knew about it since this "positive scram"
effect occurred in 1983 in Ignalina Nuclear Power
Plant. But the most distinctive feature of
RMBK-reactor is the fact that you could disconnect
any safety or automatic system, and do everything
by hand. This “I know better” mentality
is another factor that led to the disaster.
There are 10 RMBKs that are still running,
and the last one will be shut down in 2050.
So humanity brace yourself.
The whole kaboom was caused by so many factors
that it seems it was planned.
The main cause was the test of the reactor
No. 4 cooling system when the power is low.
Meaning: could the reactor cool itself when
there was a power problem? The test was planned
on the 25th of April 1986. There were some
flaws in the reactor design that were to be
fixed. In order to do so, a series of tests
had been already conducted. Previous tests
(from 1982, 84 & 85) had ended unsuccessfully.
The test required disabling of some safety
systems. And as you already know, with RMBK
you could do what you wanted.
There were 3 shifts working on the plant:
Day shift, Evening, and Night shift. The test
was to be conducted by the day shift. Meanwhile
at 2 PM some other power station went offline,
so lowering the power in the reactor needed
for the test was postponed, because you know,
people needed electricity, especially in the
evening. The day shift was replaced by the
evening shift. No one even bothered to restore
the emergency core cooling system. An hour
before midnight the test was finally green
lit from Kiev. Despite the fact that the Evening
shift was preparing to leave and the Night
shift had an hour to take over, the test was
resumed. In theory this test should run its
course like this: The test is finished during
the day shift, and the night shift maintains
a decay heat cooling systems in a basically
shut-down plant.
But now an unprepared operating shift was
on duty and they didn’t have much time to
prepare for the test. There were 3 people
that conducted it: Anatoly Dyatlov, deputy
chief-engineer of the entire Chernobyl Nuclear
Plant, he - supervised it.
Serving under Dyatlov, was Aleksandr Akimov
- chief of the night shift, and finally Leonid
Toptunov an operator of the movement of the
control rods – he was very young and had
worked there for only about 3 months. As I
said, the experiment was to see if the reactor
can produce enough power to cool itself with
water turbine when it is in a low power state.
The reactor was running low power the whole
day in preparation for the test that accumulated
xenon-135 that hampers nuclear reaction even
more.
They had a reactor that was simply switching
off, so they systematically extracted the
control rods to raise power. Eventually,
they manually extracted nearly all of the
211 control rods, leaving only 18 of the minimum
of 28 fail safe rods.
The power started to raise rapidly, water
to boil, alarms and warning lights to flicker.
But they still continued with the experiment. Why?
The first of May was too close. The 1st of
May - the International Workers’ Day – today’s
Labor Day - It’s like communists’ Thanksgiving.
The most important holiday of the year. The
promotions were given, and successful completion
of the test would have ensured that. As you
see, also the date couldn’t have been worse.
I will not bore you with the chemical / physical
details but:
- To prevent complete switch off of the reactor
and later maintain the power level, too many
control rods were extracted which made the
reactor unstable
- To cool the core, an increased water flow
was induced but it was too fast so it didn’t
cool itself, not to mention the core.
- They raised the power just to turn it down
for sake of the test .
At 01:23:04, AM on 26th of April the test
began. The steam to the turbines was shut
off in order to decrease the power for the
reactor cooling pumps. That caused formation
of steam voids (bubbles) in the coolant flowing
through the reactor. In this type of reactor,
boiling water induces chain reaction in the
core.
The power in the reactor rose uncontrollably
causing more water to boil, and this caused
more chain reaction causing even more water
to boil and so on… The Xenon hampering the
reaction was at this time long gone. Nothing
was controlling the reaction.
36 seconds after the test began, a SCRAM button
was pressed, to switch off the reactor. This
caused the system to insert all control rods
into the reactor and rapid increase in power,
which subsequently increased steam buildup
and finally steam pressure.
The control rods traveled slowly (about 20
seconds) through the core and there was the
accelerate before brake phenomenon - because
of the graphite tips. It is not clear who
decided to press the scram button since the
only people who could do it: Akimov and Toptunov
died several days later, due to lethal doses
of radiation they received.
At the time of the first explosion - eighteen
seconds after pressing the button - it is
estimated that the reactor ran at 30 000 mega
watts, ten times more than it was designed
to.
The steam explosion ripped the reactors’
casing, and blew up its metal lid. The other,
even more powerful, explosion occurred 2 to
3 seconds later. It is speculated that it
was the hydrogen from the water that caused
it. The second “bum” threw many of the
flaming graphite bricks from the bottom of
the reactor to the roof of the power plant.
The roof due to low cost was covered with
combustible bitumen. And bitumen or asphalt
is a form of petroleum. So… a fire broke.
And radioactivity was spreading all around.
Could it be worse? Yes. Despite the reactor’s
core was now bare and melting, the engineer
conducting the experiment Akimov still considered
the situation is manageable
– at first he didn’t even believe that
the reactor could have gone off. At this point
one person lost his life. It was engineer
Valery Khodemchuk who died during the explosion
and whose body was never found.
Just before 2 am, first firefighters from
Chernobyl arrive at the scene. We have flames
from the hole in the building, and bricks
of graphite laying around. At first firefighters
are unaware of the situation and pick them
up by hand. They have no masks to filter radioactive
dust, some of them quickly start to show signs
of nuclear exposure: vomiting, nosebleeds,
burns, some say that they can taste metal.
Many of them will die very soon. At the same
time, Akimov despite having proof of nuclear
fuel laying around, blatantly refuses to acknowledge
the gravity of the situation. The readings
from dosimeters are treated as defective.
Akimov orders his crew to pump water into
the reactor. They had nuclear tan and nearly
all of them, including Akimov, died soon after
the disaster. Dyatlov showed symptoms of radiation
sickness after 3 hours and was replaced by
chief engineer Nikolai Fomin.
A lethal dose of radiation is around 500 roentgens
over 5 hours (circa 5 sieverts per 5h – which
is 5000 millisieverts per 5h, and we will
stay with sieverts) - in some areas, unprotected
workers received fatal doses within few minutes.
Nearby the reactor core there was 300 sieverts
per hour. In the area of the destroyed reactor
the radiation reached 10-15 sieverts per hour.
Those exposed to radiation were transported
to Pripyat hospital and eventually treated
in Soviet Health Ministry's Hospital No. 6
in Moscow. In most cases the treatment was
futile. The dead were buried in zinc coffins
and covered with concrete, due to enormous
radiation their bodies emitted. Surprisingly,
Diatlov survived, despite the radiation he
received. Those who survived had many health
problems, skin grafting and cancer included.
Water was not enough to extinguish fires.
Moreover, it later caused a serious problem.
In the first days, helicopters dropped sand,
clay, lead and neutron absorbing boron onto
the burning reactor. Approximately 600 soviet
pilots risked their lives flying over the
reactor. The reactor’s temperature was more
than 1,200 °C (almost 2,200 °F). Underneath,
there was a mass built of graphite and fuel,
which burned through the reactor floor and
mixed with molten concrete coming from the
reactor lining. It all formed corium lava
or just corium - very radioactive mass, which
flowed into the basement of the reactor. Beneath
the basement there were bubbler pools – water
reservoirs, a safety backup in case some steam
pipe breaks. And here is the problem. Water
from firefighting accumulated there. Corium
plus water equals explosion, throwing new
masses of radioactive materials into the air.
The valves to drain those pools were in the
basement, underwater. Three volunteers from
the Chernobyl staff equipped with wetsuits,
respirators and dosimeters managed to release
the valves. They all survived! And the risk
of the steam explosion was eliminated. Then
fire brigade pumped out the water – the
task, which was completed on the 8th of May.
The reactor fire was extinguished two days
earlier. But Soviets didn’t release any
credible info about the disaster to the world,
not to mention their own citizens. Here is
an invitation for Ukrainian children to participate
in the International Workers’ Day – Labor
Day. Of course the most important party members
and their children were long gone from the
area. That is terrifying because the 1st May
parades on the International Workers’ Day
in Kiev and other cities were not canceled.
The reactor still constituted a problem as
the core kept melting through the construction.
Chernobyl power plant is placed on wetlands.
Under the plant there was groundwater which
feeds into the Pripyat River, and Pripyat
River feeds into the Dnieper. Contamination
of water was imminent. Another action had
to be done.
The 13th of May 1986, 450 coal miners came
to excavate a 150-meter (about 500 feet) long
tunnel below the reactor to make room for
a cooling system. The excavation was then
filled with concrete to strengthen the foundation
below the reactor. The miners worked in 3
hour-shifts for 36 days until they finally
secured the reactor. The following years,
170 of them died. Was is due to radiation?
Probably. Temperature and humidity made it
very hard for them to wear any protective gear
during the work.
Soviets didn’t put the 1st man on the moon,
but they certainly put the first lunar rover
on the roof of a nuclear power plant. There
were many tons of radioactive debris on that
roof that came from the explosion. It had
to be removed to enable the safe construction
of the 'sarcophagus' – a structure made
of concrete that would be placed over the
reactor and would reduce radioactivity released
into the atmosphere.
At first they used remote controlled machinery,
but radiation is devastating for electronics,
so they quickly realized that even space equipment
is quickly fried. You remember “nas mnoho”
– there is many of us – doctrine? 5000
soldiers called “bio-robots”, who wore
improvised protective gear, shoveled blocks
of graphite and other debris off the roof.
One shift due to immense radiation lasted
less than a minute. As you see, not many realized
the gravity of their situation.
All those brave men were called “liquidators”.
The miners, pilots, soldiers, plant workers,
engineers, those who built sarcophagus, chopped
radioactive trees, washed buildings, streets,
bulldozed villages and even killed animals
to prevent radiation from spreading. Their
number varies to approximately 600 000 of
them, actively combating fallout. Many of
them without gear, dosimeters – totally
unprepared for the task they were handed.
These emergency workers received high doses
of radiation - an estimated average dose was
165 millisieverts.
It took 36 hours from explosion to evacuation
of the inhabitants of Pripyat. The radioactive
cloud started to form and you can even see
it on this film taken a day after explosion.
Those flashes are radioactivity destroying
photographic film – a phenomenon applied
in simple dosimeters - used by radiologists
in hospitals. The radiation was so high that
some people had symptoms of radiation poisoning:
vomiting, headaches. Despite army planes flying
over, strange trucks washing streets there
was no official information passed to people
about what is happening. The evacuation of
50 000 people started in the afternoon of
April 27th 1986, that is way before neighboring
countries even learnt about the explosion.
People of Pripyat were told that evacuation
is for 3 days only, so there was no need to
take all their belongings. There are furnished
flats and houses with every day items to this
day. Pets had to be left behind. Of course
people never returned, and poor animals were
executed by special squads.
The iconic Ferris wheel in the Pripyat amusement
park was never even officially used, since
its opening was scheduled on the 1st May celebrations.
Several people stayed: those were either liquidators
or plant workers. Some buildings stayed open
for those allowed to stay. Imagine that another
iconic building, the Azure swimming pool remained
open and in use until 1998 – 12 years after
the disaster.
At the beginning the exclusion zone had radius
of 10 kilometers (6.2 miles) but in May it
was tripled and another 68 000 people were
evacuated. But this 30 kilometers (19 miles)
zone called Chernobyl Nuclear Power Plant
Zone of Alienation or Chernobyl Exclusion
Zone was in later years expanded leading to
more evacuations.
I already told you that Soviets kept the disaster
even from their citizens, not to mention the
world. But two days after the Reactor 4 had
gone off, the Swedish workers of Forsmark
Nuclear Power Plant, located more than 1300 kilometres – more than 800 miles
from the Chernobyl power plant – detected
radioactive particles on their clothing. Sweden
checked its reactors for leaks and didn’t
find any. It was obvious that the source of
radiation is from USSR. Under international
pressure Soviets admitted to malfunction of
the Chernobyl reactor but lied the very same
day - April the 28th – that situation is
under control. It was a few days before the
reactor fire would be even extinguished, not
to mention the risks of additional explosions.
It wasn’t until the information about mass
evacuations reached the world, that seriousness
of the disaster was obvious. For example Soviets
scrambled signal of Radio Free Europe, preventing
Western countries of their block - their own
Soviet allies - from knowing what is happening.
Soviet Union was our version of melting pot,
and Chernobyl was doing it literally.
The fire from the reactor formed a radioactive
cloud that mostly swept over Russia, Belarus,
Ukraine, Poland, Sweden and Norway even. Due
to spring weather conditions the radiation
was scattered irregularly over Europe. Soviets
tried to seed rain using special planes to
remove radioactive particles from clouds heading
toward highly populated areas – especially
Moscow. They seeded rain over 10,000 square
kilometers (3,900 sq mi) of the Belorussian
SSR. A radioactive black rain was registered
in city of Gomel Belarus that is 150 km (96
miles) from the plant. Despite all this, as
you already know, they didn’t cancel the1st
of May parade in Kiev.
There were four most harmful radioactive isotopes
(radionuclides) spread from Chernobyl’s
explosion: Iodine-131 that has a half-life
of only 8 days; caesium-134 – 2 years; caesium-137
– 30 years; strontium-90 – 28 years. But
it was the iodine-131 that was regarded as
immediate threat. This element is highly volatile
and traveled the furthest. It is easily absorbed
through air and accumulates in humans’ thyroid
glands and cows’ milk glands, being a risk
of developing thyroid cancer. Some countries
like Poland tried to prevent absorption of
iodine-131 by administering Lugol's iodine
to children but since Soviets withheld information
about event even from their own allies, it
was probably way too late for that - the radioactive
iodine was the first to accumulate in thyroid
glands. Iodine-131 and cesium-137 are the
most volatile elements from the meltdown,
and both of them were found for example in
milk.
The doses of radiation received by people
via respiratory tract in the zone are calculated
to be between 3 to 150 millisieverts. To imagine
it: two to three catscans of 90 millisieverts
are proven cancerous.
That my dear comrades was part one of our
glowing show about Chernobyl. What happened
after, you’ll learn in Part II, where we’ll
talk about radiation sickness, plants and
animals from the zone. Do there live any scary
mutants? This and many, many more interesting
facts from 1986 until today. Thank you very
many for
your attention, Stay tuned, be a good stalker
and subscribe. To our Zone. Bye
