Let me introduce myself.
My name is Vladimír Slugeň
and I am professor in area of
nuclear power engineering
at Slovak University of Technology.
I am working in field of nuclear
safety or nuclear accidents
for more than 30 years.
Since it is 30 years from accident
in Chernobyl, we thought,
not only for our students but
for interested public as well,
let's try to give a presentation,
where we can remind this accident,
discuss reasons and consequences,
but mainly try to get to the topic
of what Chernobyl accident meant
during next 30 years of development,
not only in technology
but in general acceptance of
nuclear power engineering
in society.
So, this presentation is going to be
focused mainly on changes in 30 years.
30th anniversary is going to
be exactly on 26th of April.
The accident happened shortly
before half past one o'clock.
Up there should be clock,
where you can see the time
when accident happened.
Someone would ask:
OK, how long had been this
nuclear power plant in operation?
It was the first operational shutdown!
It had been brought in operation just
two years ago, not including two days.
Yes, it was operating two years
thanks to continuous exchange of fuel
instead of campaign fuel change.
So, it was relatively young
power plant with first planned
operational shutdown from
beginning of operation in 1984.
Why is this nuclear
accident significant?
I think that all of you will agree,
it was the most horrible
nuclear accident in history, because
it had impact not only on Ukraine,
Belarus, Russia but also on
that time Czechoslovakia and
entire Europe except
for Portugal
and here you can see how
the radioactive cloud,
which represents concentration
of Cesium-137 in air spread in Europe.
First to register this were
Scandinavians mostly
Sweden and Finland,
then the cloud turned
and on the second-third day,
it followed direction through Poland,
above Czechoslovakia
and impacted our territory the most
as it went on through Morava
and Ostravsko (parts of Czech Republic)
and spread across all the Europe.
Maybe this radioactive cloud,
regarding radioactive contamination of
Europe's territory doesn't mean that much
and mainly meteorologists
would say it depended on the rain.
So, where did the Cesium and other
elements dropped to the ground
and where was their concentration
the highest?
But if you will have a look,
this is the 5th day after accident.
We are spread in whole Europe
and it is important to notice
that this radioactive cloud
is heading direction south
and the graphite which was
burning was already extinguished.
But on the 7th-8th
day another eruption occurred,
so, the cloud was still evolving
until 10th day,
which effected Bulgaria
and Romania.
Here you can see that
the reactor goes out
and that is when the graphite
extinguishing was managed
and heat chimney, initially 15 km high,
which propagated radioactivity in the air
was closed.
Up there you can again see
reactor gone out and the rest,
spreading on 10th, 11th, 12th day
is just mixing above the Europe
and heads to the ocean.
The radiation, radioactive cloud
movement has no boundaries so,
it is said that nuclear accident anywhere
is like nuclear accident everywhere.
The cloud won't listen when
you say "Stop, this is boarder,
no passing through
without the passport".
This is how reactor looked
like after the accident
you can see it was
truly big detonation
consisting of two explosions.
First one from water vapor,
second one most probably from
Hydrogen few seconds after first one.
This is already extinguished
reactor when various sands,
dolomites and lead
was thrown in there,
to create air-tight layer to
prevent graphite oxidation and burning.
In the next picture, we can see 4
blocks of Chernobyl nuclear power plant.
It was really young power plant.
Design-wise, there were slight
differences between first two blocks
and the second two blocks,
which had common operation part and
here you can see long hall
- engine room with turbines,
which connected all four blocks.
Two more blocks were in time
of accident under construction 1.5 km far
and during that night several hundreds of
workers were on the construction site.
Overall number of workers on
fifth and sixth block
was something between
three to five thousand more.
Currently you can see the
sarcophagus of fourth block,
which should be covered with
new sarcophagus,
because of decreasing leak
resistance of the first one.
So, the preparation of new
sarcophagus undergoes for few years,
with really interesting parameters:
height 105 meters, width 257 meters,
length 150 meters.
And if we will have a closer
look on the simulation,
we can see actual construction
of the sarcophagus.
You can see that the
construction is complicated,
financially demanding. In Ukrainian
conditions, it overcharges.
Last news say, it is already 4
times overcharged.
And it is still not finished.
Year 2018 should mean complete
coverage with new sarcophagus.
You can see as the construction
grows and is assembled.
It is divided in so called
eastern and western gate,
which will be eventually
connected and transferred
through rails over 4th block.
It will ensure leak resistance of
first sarcophagus for escaping
of radioactive elements.
So, when it will be assembled and
moved to its position,
it should last few decades
before actual decommissioning.
The consequences were terrible.
Maybe not in the number
of victims.
The causal connection to
the death was proven, as far as I know,
in 62 cases, where it was unambiguous,
but many in cases it was not.
Chernobyl could have had some
impact in form of dose received,
which could have caused some
oncological disease
but there were a lot of
psycho-social cases.
When 116 317 people are evacuated
from the 30-km radius.
And they abruptly lose
their home, personal ID, glasses,
teeth prosthesis, when they still fear
of illness, their children, losing their jobs
and sit one, two, three years
somewhere in sweat pants
and they just gain weight
and after 20 kilos
they have increased probability of
diabetes, high blood pressure
and mainly despair that they will not
get new job.
These impacts are significant
as well as the radiation.
The acute radiation syndrome
was registered by 134 cases,
from which, 106 cases were cured.
These were acute radiation syndromes.
28 people, mostly firemen
died till 4 months from accident.
But we have here almost
600 000 soldiers,
who were there for
week or more to build Slavutych,
inspected some zone or
decontaminated the roads
and they were changing in
weekly reshuffles.
>From these 600 000 only
110 000 were monitored
to the consequences of radiation
but 500 000 people were lost from
evidence and proving causal
connection is pretty difficult.
If someone is going to say that
hundreds of people had serious
health issue as a consequence of
Chernobyl accident, it is true.
But numbers from 10 000 to 100 000
are frequently presented,
which is not true.
Next, when we take into
consideration
100 times higher released activity
then in Hiroshima and Nagasaki,
but still it is 1000 times less
than activity released by nuclear
weapons tests in 50ies and 60ies.
Approximately 10 km dead forest
zone - rusty forest,
which still has orange tone,
was burned by fire and
there was the greatest
radioactive elements fallout.
If we have look where Chernobyl is
located, it is 100 km north to the
Kiev, near to the borders with Belarus
and Russia. Paradoxically, 90 % of
radioactive elements were spread
outside Ukraine, from which 70 %
felt on Belarus and a part on Russia.
So 70 % of all negative radioactive
impact felt on Belarus even though
the epicenter was in Ukraine.
Luckily, these were areas of
swamplands and except for new
city of Pripyat, which had to be
evacuated, 3 km far from power
plant, there was more-less lower
population density - villages or
small towns and in Belarus, it was
even smaller. But the environment
impact was on all 3 states. It is
970 km far from Bratislava. Here is
what I have been talking about.
You can see concentration of
mostly 137-Cesium, where we can
see, impact on Ukraine and nearby
Belarus, where it probably rained as
well and were these radioactive
elements settled. Next highly
contaminated area is between
Russia and Belarus. They made
this area a reservation and let the
nature to handle this on its own.
Naturally, a lot of people were
evacuated from these areas as well.
If we compare contaminated areas
from Chernobyl and Fukushima
accident, we can see that 30-km
zone by Fukushima has much less
contaminated area than it was by
Chernobyl and released activities are
higher as well. Why are nuclear accidents
regarded such negatively? If we would have
thought, what matters during 30 years
the most about nuclear accidents, because
in the meantime Fukushima accident
occured, it would be tragedies, victims
which are significant, but when you
think about fallen plane  with 300 people
aboard, 1992 - 1994 in Rwanda were
murdering Hutus and Tutsis each other
in civil war. Millions of victims that world
barely registered this, at least the
media didn't intensively inform
about this. When you think about
different energetics accidents:
Bhopal (1984) - 2850 dead and
more than 200 000 affected with
health issues, when chemic factory
exploded. Think about gas explosions,
explosions of coal dust, bronchitis
all over the world, which increases
illness and death rate. Regarding
this, the number of deaths in
Chernobyl, without any belittlement
is not the key issue. Fire or floods,
which destroy areas are accepted
across population, sometimes it burns,
sometimes a wave comes, which
floods something but nuclear
accidents are not-acceptable and
taken as a big thread is that area
like this, which I am showing, will be
longtime hardly usable - loss of territory.
This is one of the consequences of
Chernobyl, that we think about
nuclear accidents as about territory loss.
Maybe the life will return there
after around 50 years, maybe the
contaminated zones will narrow
but at least in first decades, these
areas are evacuated, no agricultural
production, natural reservations are
needed as well, but when it is
densely populated zone, it is not
acceptable at all. The next reason
is fear from unknown and possible
genetical consequences. We have
experiences with Roentgenologists,
with generation from Hiroshima and
Nagasaki, there are 3-4 generations
from first nuclear bombs used, 30 years
are gone from the Chernobyl accident.
There are no remarkable genetical
consequences proven but after 3-4
generations they cannot be neglected
as well. Maybe this needs 10 generations,
maybe totally distinctive look on
these values. But there is potential
thread, subconscious thread from
genetical consequences of radioactive
radiation. Huge long-time material
and financial losses. To eliminate
impacts of Chernobyl it means
hundreds of billions and even
if Ukraine looks big, you can
see in nowadays establishment
there are no founds left. 
So, it stands still and
solutions are postponed.
I have already been talking about social
impacts. These are hardly identifiable things.
Public perception is changing, people lose their
jobs, perspective and trust in technology changes.
What had changed after Chernobyl
the most? Information propagation speed.
If we should list technical inventions in 30
years, everybody would say Wi-Fi or internet.
Information will speed up everything
and information is shared.
So, the speed of information propagation
has influence on politics as well.
Chernobyl accident occurred in time
of Perestroika and Glasnost.
If it would have occurred 5 or 10 years
earlier, during Brezhnev rule,
maybe the information would have
been totally different but the accident
occurred in the end of 80ies, when the
public perception was already changing.
Naturally there is a possibility to disagree,
dissatisfaction, the way how to change the government.
So, the election results are dependent
on information level of people
and when they get distorted or true information,
it can influence politics or change governments.
Chernobyl occurred in time of green wave.
Unacceptability of radiological impacts.
It was totally contradictive to the green organic
wave which spread in Europe in 90ies
and lasts until today. Globalization - the accident
really affects everybody all over the world -
see point nr.1 - information propagation.
And finally, price liberalization. Nuclear energetics
stopped being national prudence matter.
It stopped being matter of prolonging of
military complex and research for military
purposes, then shifted to peace purposes,
but started to be part of competition
between various sources.
Chernobyl meant increase of price per
kW/h produced in nuclear power plant,
because dramatic growth has been
made in the area of safety systems.
Investments in hardware were huge. Safety
features in deed, increased the price of
electric energy from nuclear power plant
and competition arose.
Who is better and cheaper will operate, because
profit becomes substantial in energetics.
And we want the security to be substantial.
Let's talk now about actual changes.
I don’t want to talk expressively about social
impacts but more about nuclear safety,
because that is topic I understand more.
The term safety culture has been introduced.
If someone should say what is lesson learned
from Chernobyl, safety culture has been accepted.
This term was introduced because, by events
analysis was told, mainly in first few years,
operational staff failed because they
didn't operate reactor safely.
They disengaged protection systems and
did it more times, there was no discussion.
No full-scale program was made in advance.
No possible impact analysis was made.
So, safety culture failed. This is main lesson
learned from Chernobyl accident.
Safety guidelines started to be overwritten
differently and new safety requirements
arose to all nuclear power plants
all over the world.
Human factor started to be analyzed,
because it is very important.
Nowadays, it is said that 70 - 80 % of
possible failures, come from human failure.
Symptom oriented guides, procedures
and training.
We expect that something can happen. We
make an analysis in advance. We get ready.
And when indicators in control room
indicate, that process goes this direction,
we already have exactly symptom oriented
guide, which we take and react,
ready for the situation because we
have safety engineers,
who analyze and are getting ready for it.
Next, severe accident management guidelines.
These are guidelines or recommendations
of procedures during severe accident.
Even when once in 1 000 000 years,
this accident could occur,
we anticipate and prepare to handle
this event, we have procedures in advance.
This is part of safety documentation
of nuclear installations.
Investments in hardware are the huge investments
initiated by this accident.
Not only for RBMK type reactors,
but generally,
inherent safety, safety based on physics,
started to be build.
It is based on initiation of processes,
because physical principles must work.
Inherent safety features were
implemented, which resulted in:
redundancy, diversification of
various systems,
multiplication of chose logic,
Increase of device safety,
implementation of probabilistic safety assessment
until structural measures,
I listed one - core catcher.
New types of power plants are built with
premise, that this could happen.
I am going to talk for a while, because
computer does what it wants sometimes.
It can happen that reactor core
melts down,
and when reactor core melts down,
it is unsolvable situation
New project say:
"Yes, we will sacrifice reactor core,
but we eliminate possible impact
on the environment by sealing impacts
of given accident in containment."
We anticipate, that with given probability,
let's say once in million years something
can happen and we have measures to
eliminate impact of an accident.
Various technical solutions
are available for this.
Next, in crisis safety
systems omit people.
This was not by Chernobyl and by accident
analysis we will tell,
where should the safety system react and
didn't let to be blocked out.
Exchange of experiences.
For example, international group
of experts was founded- INSAG.
International Nuclear Safety Advisory Group
And INSAG 1 as document written by
International Atomic Energy Agency,
was created in September 1986 based
on conference in August 1986,
where Soviet delegation referred about causes
and consequences of Chernobyl accident.
This was the first analysis
of Chernobyl accident.
But this group was formed, which
continued working
and groups of experts in Nuclear Safety
were meeting,
in 1988, they wrote INSAG 3, where
nuclear safety was defined,
goals of nuclear safety, its principles,
defense in depth was defined as well.
INSAG 4 defined safety culture and
these materials were involved
in national legislations and shifted perception
of nuclear safety to another level.
WANO (World Association of Nuclear
Operators) was founded as well,
where experiences are exchanged,
verifications are made and advices are given.
In the end of 80ies, beginning of 90ies,
INES scale was introduced.
International Nuclear Event Scale.
So, when accident occurs,
according to simple criteria,
understandable for journalist and
even politicians as well,
when know to scale impact of
the event.
>From anomalies and incidents- INES 1, to
heavy accident INES 7 - Chernobyl accident.
All these things were created
after Chernobyl,
even some signs of need for this
were before it,
but Chernobyl speeded this up and
nuclear safety got totally different
dynamics and importance.
So, when we have closer look at the 4th
block of crashed nuclear power plant,
we will try to tell something about:
causes, process, consequences and outcomes,
which followed from this.
Firstly, we should tell something
about design of RBMK 1000 reactor.
1000 that is electrical output.
It was not accurately 1000 MW.
Clean output was around 950 MW,
but let's stick with 1000 MW - electric.
Thermal power was 3200 MW - thermal.
You can see, the graphite was moderator,
coolant was common water,
fuel was UO2 in fuel
pellets - ceramic fuel
Maybe most important is to imagine
reactor core as cylinder.
Imagine this room as reactor core.
It would almost correspond with
reality, if we were in cylinder,
with diameter of 12 meters,
what we maybe have
and height 7 meters, what
we also possibly have.
Everything is from graphite,
carbon - really good flammable.
When it is ignited, it burns terribly.
This is reactor core.
Fuel enrichment was relatively low -
2 %, nowadays we are getting to 5 %
but 2 % were due to design
of this reactor type
and it had side effect that
spent fuel could be reprocessed
and Plutonium could be
separated for military purposes.
Burn-up was relatively low,
20 000 MW-days per ton.
Temperature of coolant at the inlet
was 270°C, it was still water
but we have to say, at pressure of 7 MPa -
70 times atmospheric pressure.
It means 270°C is still water and
in top third of reactor core
it changed into steam with 284°C.
>From reactor division point of view,
RBMK reactor type,
"Reaktor Bolshoy Moshchnosti Kanalnyy"
(High Power Channel-type Reactor)
was something like one-circuit
boiling reactor,
where water was changing into steam
and through separator it followed
to turbine, where it expanded.
Number of elements was 1600.
Number of control
rods was 211.
Where in the world were this type
reactors build?
Biggest blocks, which long
term leaded the size chart
were in Ignalina (Lithuania), there
were 2 blocks with 1500 MW-electrical.
Four blocks in Bilibino
were on 10 MW level,
but Bilibino is direction Kamchatka,
where it served mainly for
diamond mining
as energy source, but unit performance
was only on level of 10 MW.
These were only small blocks.
Kursk - RBMK 1000, Leningrad as well.
Smolensk - 3 blocks build, 4th
was not further constructed.
In Chernobyl 4 blocks were build
and launched in 1978, 79, 82 and
4th crashed block in 1984. Relatively
young new power plant.
If we take remarkable milestones,
how it all ended:
Commercial operation begun in
1978 but shutdown in 1996 for 1st block.
It means 10 years after accident.
2nd block was shut down in
1991 because of fire.
Next technology failure. They didn't
repair it afterwards but shut it down.
The longest operated was 3rd block,
which was operated until 2000.
It had common wall with 4th block.
They separated it and operated till 2000.
And the 4th block, after accident in
April 1986 was shutdown.
9th of April 2015, this spring,
entire Chernobyl locality
came to decommissioning state.
Until now it was ending of
operation state.
Preparation for decommissioning
were ongoing.
So, Chernobyl locality is in first
stage of decommissioning since April 2015.
Construction.
How does the block look like?
Let's take reactor core,
that is the cylinder,
12 meters in diameter,
7 meters high.
2 fuel elements above each
other in one channel,
where water flows.
You can see the pipeline,
where water is injected from
the bottom of fuel channels,
comes around fuel elements,
heats up, changes into steam,
steam comes out
through separator,
where water drops are
separated from steam
and from separators it
moves on the turbine.
After condensation,
it flows back through main
water pump in reactor core.
Here, you can see:
separators - 20 meters
long cylinders,
on one side 4 main
coolant pumps,
on the other side 4 main
coolant pumps,
fuel charging machine.
This picture is much
more schematic.
Here is the fuel element
inserted in channel
and surrounded by graphite.
Water comes around
fuel elements,
where it takes heat,
changes into steam,
comes to separator,
separated steam
moves on the turbine,
expands,
with mechanical work
rotates the turbine's wheel,
which has the same shaft
wit generator's rotor,
which produces alternate
electrical current.
When steam does it work,
it comes through condenser
and condenser pump and it is
injected back,
through main coolant pump
to the reactor.
It is one circuit nuclear power plant.
Really important are
these control rods,
which are inserted,
these channels are
filled with water
and here are absorption assemblies -
neutron absorbing material.
It decreases reactivity
of the system.
These channels were proven
as bad construction solution.
They contributed in
accident elevation.
We will talk about it later.
Here, you can see construction
of regulation components,
which are being inserted.
During operation, when I have
power level set,
they are in certain position
and when I want to make
operational reactor shut down,
I insert these regulation
components in channels,
I expel the water and put
absorber in its place.
Construction-wise, you can see
the graphite dispatchers,
which were part of accident
by bringing positive reactivity
in the beginning.
Because at such a low performance
as they operated,
they detected increase
of reactivity,
which was a structural error.
Constructors wanted to
introduce it there,
because it had a very positive
neutron balance effect,
when the reactor was
at nominal output.
But, it was not well designed
for emergency situations.
So, this was one of the
block construction errors.
Here is a look at the reactor
fuel channel arrangement.
These gentlemen move
over reactor core.
So, under each this element,
there is a channel,
where is either a fuel assembly
or the regulating element.
Fuel was changed
during the operation,
by isolating of one
channels,
attaching fuel charging machine,
fuel was changed
and then reactor continued
without changes.
Here you see the separators.
Here you see 4 main coolant
pumps on each side.
Here is reactor core.
Here is fuel charging machine.
Fuel charging machine -
relatively big object,
which is placed onto its
place it equals the pressures
and changes fuel assembly.
Control room was
relatively complicated.
One of the reactor errors was that,
power could not
be regulated uniformly.
There could have been some
power oscillation,
even though they
were counting on it.
Despite the fact that the designers
had a number of measures to minimize it,
but similar control room,
maybe not so extensive,
can be on another reactor
types as well.
I have been talking about
pros already:
The Russians have had good
experience with the reactor type.
Very few now, that the first reactor
brought in operation in 1954
in Obninsk with 5 MW,
first Russian or first commercial
power reactor had similar design.
There were experiences,
Russian-home construction.
A favorable neutron balance,
which was one of possible military reasons
reasons for plutonium production.
Next, construction did not
require pressure vessel.
Despite huge thermal
power - 3200 MW,
it was very unnecessary to make
a large durable pressure vessel.
They made 1600 channels.
Basically, we can produce pipe
faster than a pressure vessel.
But by increasing
the reactor power
by enhancing the number
of these channels
was extensive approach, which
was not construction-wise ideal.
But it was not the reason
for the accident.
Continuous fuel exchange
was one of the advantages,
because the reactor could
operate for several years.
If it did not require any
operational or unplanned shutdown,
you could continuously exchange
individual fuel elements.
Cons:
Unstable at low power,
below 700 MW-thermal,
when feedback reactivity
coefficient was positive.
It was a constructional error.
And although in regulations
it was forbidden
to operate on this power,
it was not foolproof.
It was not possible
to avoid it.
Further, positive void reactivity
coefficient at less
than by 80 inserted
absorption rods.
Of course, this is a bit
more complicated
because some manipulations,
transient modes
required lower number
of rods in reactor,
even up to 15 inserted rods,
bud in accident case, when
equivalent was calculated,
it 6 to 8 regulation rods and
the positive void coefficient
was really significant at this time.
Reactor core was too big,
meaning complicated regulation
and slight leakage of radioactive material
from turbine working area.
This is common in all boiling
reactor types
because steam from reactor
flows directly into turbine.
This one circuit can not be
made so leak resistant
as by two circuit power plant.
But when the power plant is
operating in the standard mode,
these leaks are not significant.
Even though they are slightly higher
than by the pressure water reactors.
What happened on 26th of April?
They had a scheduled security
test for the 4th block.
And what was the purpose of the test?
It was a demonstration of the
ability to cope with a power outage
of a selected port of
its own consumption,
own consumption,
which provided supply for
main coolant pumps,
till start of diesel generators.
Diesel generator needs
certain start-up time.
40 seconds are needed for diesel
generator to start working.
These 40 second have to be
bridged over in some way.
It should have been after-running
of turbine's rotor
and rotation speed regulator has
been installed at the generator,
so supply of main coolant pumps
will be ensured without problem.
Experiment plan was written in
advance and too generally
but it was pretty clear:
After closure of quick turnaround
valve ensure turbine's after-running
till this supply is covered
from diesel generator.
Decrease of thermal power to
allowed level 700 - 1000 MW.
Disconnection of emergency
cooling system - it was planned.
Switch of supply for main
coolant pumps in such manner
that 4 will be supplied from
outer grid
and 4 from after-running
turbo generator.
After 8th turbine shutdown,
measurement of electrical
parameters should be made
according to the test program.
Everything was electrical experiment!
Test was regarded as matter of
electricians and block's regime
was not well prepared mainly
from nuclear safety point of view
and it was underestimated.
Test preparation:
It must be said, during preparation
several significant errors occurred.
The first, and really big error was
by grid operator to operate
the reactor at 50% for next 12 hours
after power decrease.
So, the power rate was at 50%
one turbine was shutdown
but mainly Xenon was produced,
which is poison element
regarding reactivity absorption
and operation stability
was changed.
It could be handled but
it was a good state.
It was not consulted,
it was not in experiment plan.
Furthermore, when you
prolong the time,
shift, which was trained and prepared
for operation during experiment
went away and another
shift came,
which was not prepared
and didn't count with it
that something like that
could be in progress.
At 12 O'clock they changed
the shift and third shift came.
To do experiment like this during
the night, because it came out this way,
is not very reasonable, because
people are more tired, sleepy
and planning of experiments like
this during the night
doesn't happen any longer.
It came out like this that time,
furthermore, somebody said
by 1st of May this test should
be accomplished.
No one can analyze this
accurately now.
At 00:28 thermal power
dropped to 30 MW.
Maybe from the reason
that the regulation
came from auto to manual
and the process was not
set up properly.
Operators didn't count with
this case a lot.
It was not planned.
They should be over 700 MW,
700 to 1000 MW,
but the thermal power
dropped to 30 MW.
At this point they should
shutdown the reactor!
Because operation of reactor
is not allowed below 700 MW-thermal.
They should have shut it down
but they didn't.
They continued.
Command for operator came
to increase the power
by pulling out more control
assemblies-absorbers
so, they had 80 inserted
no more, non 26 to 30
which was recommended
for this transient mode,
but they reached thermal
power of 200 MW,
what head of shift - Dyatlov
regarded as manageable level.
Switch on of auxiliary pumps,
decrease of water level in separator.
Maybe it wouldn’t mean so much,
but steam amount was increasing.
We go on. Operator switches of
automatic shutdown safety system
in order to continue in operation
in case of experiment failure.
This should not have happened!
This is one of operational
stuff errors.
Pulling out of few more manual
absorption HRK rods
(emergency regulation-compensation rods)
due to temperature and pressure
increase in separator.
Regulation for minimal inserted
HRK was not met.
If they didn't, they should have
shutdown the reactor - next error.
Maybe not decisive,
but significant.
Operator decreases coolant
flow due stabilization
of water level in separator.
They wanted to get it
in stable state.
Excess steam creation is
generated in reactor core
This meant that even in channels,
where was water,
where regulation assemblies
are inserted,
water was more absorber
than moderator in this case,
graphite was moderator,
this water was changed
into steam.
Once more, neutron absorption
was decreasing
because steam begun to be
created in these channels.
Next, operational indicators.
1:22:45 operational stuff got
information, which they relied on,
that reactor is stable.
And this should not
happen either,
but operators were not
responsible for this.
They received information
that reactor is stable.
This was the reason to
continue with the test
So, time 1:23:04 follows, when
inlet turbine valves are being closed.
The quick turnaround valves are
closed and turbine's after-running begun.
Now was the time when
the experiment started!
Subsequently, automatic HRK
are beginning to be pulled out slowly.
This is the consequence of
these assemblies design.
Afterwards, after 11 seconds,
power increases
due to void reactivity coefficient
also created steam amount increases
and begins to grow uncontrollably.
Maybe if they pushed
the AZ5 button now,
they could have managed
something,
even though some
thermo-hydraulic analysis say,
that even in case of pushing it
23:10 it could not have been helpful.
23:40 operator pushes
emergency button AZ5
that is analogy of fast
reactor shutdown,
where actuators insert
regulation assemblies.
After few seconds operator noticed
it was going down too slow,
"let's disconnect them and
let them fall with their own weight".
Even that did not help.
The steam pressure was so high
that it stopped the assemblies.
The steam pressure was
still growing,
fuel elements are beginning
to break-up,
the steam exploded.
This was in few seconds intervals.
There were two explosions.
First from steam pressure.
Second most probably as consequence
of accumulated hydrogen, CO2 and air
similar to the other cases,
when concentration of hydrogen
in the air is more than 4 %,
explosion follows,
which smashed the reactor core.
Here we can see,
the power evolution.
This was unplanned operation
at 50 % power rate - first error.
Second error - mismanagement
of transition to testing level.
Third error - test beginning
at 200 MW - thermal.
They switched of the
protection system,
after which two explosions
followed, which caused
destruction of 4th block
of Chernobyl power plant.
The first INSAG blamed operators
from everything.
Maybe from the reason, that
the main report was done
by designers, which did not feel guilty
for the construction of this 4th block.
And operators clearly did some mistakes.
The fact, that you can not do
safety regulation by using red color
to write what is prohibited but
you don't physically block it,
it is also structural error for me.
The reactor was not
sufficiently inherently safe.
In 1991 INSAG 1 was revaluated
and another document was written -
INSAG 7 where structural block
errors have been highlighted.
These were the dispatchers made
from graphite on control rods.
Simply the fact, you have emergency
handbrake as in train,
which causes evolution of
fission reaction,
this is substantial
structural error.
You cannot have substantial safety
element for fast reactor shutdown,
which starts fission reaction at certain
circumstances and causes explosion.
This is main structural error.
Of course, there were more errors
in reactor design:
the void effect should not be
designed by constructors this way.
Precise identification the reason, which
started the power excursion
based on executed analysis
was not possible.
Maybe we came close to
highest probability.
Nevertheless, pushing the button
for reactor shutdown
was regarded as most probable
reason of accident elevation initialization.
Even though, many accident analysis
say that even if the automatic shutdown
was initiated at the time,
it would be too late
and same thing would have happened.
Many reactor operators
paid for this with their lives.
Reactor operators Akimov and Toptunov
received dose around 4 Sv and died,
on 15th and 17th day.
The shift head, at that time
head of experiment
and head of reactor
operation was Dyatlov,
He received 6 years
arrest punishment,
in the meantime, he suffered
from leukemia, received 5-6 Sv
but because as if he was older,
maybe his body radio sensitivity was lower,
maybe when he served in submarines,
he received some dose,
and maybe he was more
resistant to it he survived.
Even when he suffered from leukemia,
after 4.5 years,
he was released from prison,
he took healthcare,
he has been traveling to Munich
for marrow transplantation
and died to heart attack.
But, not all the blame
can be put on him.
Of course, he was
responsible for it
and big part of responsibility
lays with him.
But for sure, he was not fool.
He absolved MEPhI with red diploma.
He was recognized by
all RBMK experts.
He was regarded as person,
who know a lot about RBMK.
But, most probably he failed here.
Notice, that the power plant director,
who was not present that time
received 10 years prison punishment.
Notice, that main engineer received
10 years prison punishment.
Notice, that reactor guild chief
received prison punishment too.
Notice, the regulatory body inspector
received prison punishment too.
This was their error as well.
Because the operator is inseparably
responsible for the personnel.
And when he committed, that personnel,
which didn't keep safety regulations,
it is his fault as well!
That personnel was not good choice.
That it was not appropriate
psychologically tested.
That it was not instructed properly.
This all is error of leaderboard
of electrical company
and you see, the regulatory
body has been punished as well.
Accepted measures after accident.
Reinforced concrete sarcophagus
was build, finished in December 1986.
Next, population has been evacuated.
The 36 hours post accident
seems too long.
But, I don't think, that it
was such unforgivable time
because it happened from
Friday to Saturday,
precisely in early Saturday morning.
Commission flew to Kiev
in the morning.
Decision for evacuation was
issued till 12 hours from accident.
And last from 116 000 was evacuated
36 hours after accident.
Can you imagine to manage buses,
hygienic loop, showers, new clothes
for 116 000 people in 36 hours?
This is really tough challenge for everyone.
In comparison with Fukushima, fatal cases
are not know during population evacuation.
But in Fukushima after the
tsunami wave has fallen,
although radiation was not so high,
during evacuation from
44 000 people 50 people died.
It has to be said, longevity
in Japan is differently set,
there were some
retirement houses,
and replacement of lying patient
in age of 100 years has a death scent,
even if it would have been
done in most cautious way.
But, in Chernobyl case, surroundings
have been relatively young.
Pripyat city with 50 000
inhabitants was young.
It was established in 70ies.
Approximately in one month
116 000 have been evacuated
and except for that,
after accident,
mainly from most contaminated
areas, mainly in Belarus and Russia,
next 220 000 people have been
evacuated but this was sequential.
Total evacuated area has been
increased from 2800 square km
to 4300 square km.
That is one tenth of Slovakia.
Accepted technical measures:
Increase in operational reactor reactivity.
Minimally, 40 HRK rods must
have been installed.
Next, installation of additional
absorber rods
to avoid operation at
low power rate
and to prevent positive
void reactivity coefficient.
Increase in fuel enrichment
from 2.2 to 2.4 %,
which shifts the boarder value
of 700 MW-thermal direction zero.
Next, speed up in control rods
falling time from 18 to 12 seconds,
there were no more the slow actuators,
which inserted the rods.
Design change in control assemblies
graphite dispatchers have been removed.
Fast reactor shutdown system installation,
which was more effective.
Measures to prevent unauthorized
interventions in control systems.
Certain protection systems could
not be switched off manually no more.
So, it was probably the biggest
nuclear accident in history.
The primacy is not
very wanted or famous,
mainly, from radioactive
material release point of view,
from terrain contamination point
of view, it had the greatest impact.
It was consequence of technology
and human factor failure
and it is difficult to judge and say,
that 90 % of blame
lays with constructors and design
of power plant
and 10 % with operating personnel.
>From certain point of view, the blame
of operating personnel can be even higher.
It is mutual combination
of both reasons.
Additional deaths, mostly from
insufficient management of
post-accident measures
is not exactly monitored
but some were there for sure.
Contaminated area will be
withdrawn from usage for decades
regarding technical and
agricultural purposes.
A lot of measures in safety
increasing all around the world.
Of course, the safety culture
of nuclear installation level,
which tried to learn from this accident,
has increased.
Slovak nuclear society,
in 2011 organized
scientific expedition to Chernobyl.
Various professors, associate professors
or students of our institute were there.
They have been there
for one week,
measured radiation conditions
and told about the current state.
So, you see the Pripyat city,
you see the block,
4th block of nuclear power plant,
and 18 km south was Chernobyl town,
with something around
12 000 inhabitants.
Pripyat had 50 000 at the time
and was just 3 km far.
Very big luck for Pripyat
inhabitants was,
that the first wind blown
direction rusty forest area.
It did not go directly Pripyat direction.
Here, you see data,
dose rate on the way by train
from Slavotschuk to Chernobyl
nuclear power plant.
Big thanks go to associate professor
Hinca, who supplied and measured the data.
These data have to be compared
with fact, 100 nGy per hour
could be measured on Europe roads.
So, it is clear, the road has been cleaned,
this is railway track.
Somewhere the dose rate was higher
and it increases direction block.
Here expedition participants
monitored radiation condition
in Pripyat city and you see
big differences,
from 4000 to 272 nGy per hour,
depending on decontamination quality.
If we were in Slovakia, the number 272
is double or maybe triple of average.
Of course, 4000 is extremely high.
But this is Pripyat city,
which is evacuated.
The activity still decreases,
here, you see railway station
at the Chernobyl entrance.
There is controlled area, people
step out of the train,
come through the detectors
and change their clothes.
At the time - September 2011,
when our members
of nuclear society were there
equivalent dose rate,
was measured at reactor level
at 22.5 but this is in uSv per hour,
elsewhere it decreased to 3-4.
Currently, when the online
monitoring system is installed
the dose rates move
at the half of our measured data
So, 50 - 30 % lower.
This is data from the day
before yesterday.
You can visit next website as well,
where you have monitoring system,
which measures effective dose rate
around 300 nSv per hour,
in Pripyat and Chernobyl,
of course, it is higher in Pripyat
because it is closer to crashed block.
So online, you can promptly
find out radiation situation
at various locations.
Activity estimations, released
at the time of accident in environment,
these are analysis, estimations
not accurate numbers.
But they came from certain
model with justified assumptions.
You see, the activity on the
10 to the 18 Bequerell is really high.
>From 10 over 15 Bq you have INES 7.
That is the greatest accident.
This was 10 to the 18.
Most affected area in Czechoslovakia
was Ostravsko area,
because of biggest rain.
And the differences are
sometimes multiple.
You see it has stabilized
over the time.
So after one month it has
got to the level of previous background.
Here are the most affected areas,
this is bound to Cesium-137 in kBq/m2.
Maybe, the most important is to
do some comparison,
because the numbers are hardly
understandable for a layman.
So, let's take our area
natural background,
which is at 2.4 mSv/year level,
whether we want it or not,
whether we are members
of Green political party
or we are technical lobby
each of us is getting this
mostly from Radon
or from the rare earth elements,
which come from the ground
or from the Radon from
building materials.
That is 2.4 mSv.
Diagnostic examination,
when we undergo CT or roentgen scan,
we receive less
but that is significant
it is 0.4 mSv but that is one time dose.
Atmospheric weapon tests in presence
have really small significance
but in 60ies it was much higher.
Firstly, the elements
have been reduced,
secondly, radioactive elements
are decaying, so the impact is smaller.
Chernobyl accident has
small impact today,
similar to the Fukushima accident.
But,
the world is full of differences.
radioactive load depends very much
on altitude you live in,
because you are affected
by cosmic rays
and if you are stargazer for instance
somewhere in Lomnicky peak,
you receive higher dose than
IT worker in Bratislava.
Of course, the locality you
live in makes the difference.
Whether in Slovakia, where
where background level is at 2.4 mSv
or you are somewhere in India,
province Kerala tells about 17 mSv/year.
But there are certain localities,
where we receive up to 260 mSv/year
which is so much,
that it is extreme.
But this is province,
where people live,
take it as natural
and are used to it.
There are no direct connections
with illnesses or nobody observes it.
But when rescue workers
hat to go to Fukushima
for certain time
to do certain measures,
limit was 250 mSv but for the action,
these data are per year.
If we have a look on comparison
of impact of Chernobyl accident
with other impact such as
nuclear weapons tests.
Look, this is average Belgian.
Belgium, far from all nuclear weapons tests.
They received this from
Cesium in the air
and this was in
Belgium inhabitant body.
This is contribution of Chernobyl
and here you see the spike from Cesium,
that was the cloud,
which came over it.
If you compare effect of Chernobyl,
as nuclear accident
with contamination from
Radon from building materials.
Radon is released from the walls,
from building materials, it is gas,
alpha radiation source,
we breathe it,
half live of 3.82 day.
This is what affect us the most
from radiation point of view,
almost 70 %.
Chernobyl did not reach this
Radon level,
regarding impact on human
body on our territory, at the time.
So, worrying about Chernobyl impact
on our territory,
maybe was not adequate
even in 1986.
Maybe, I would not like to be
a cyclist at peace race
in 1986 which started in Kiev
on 6th of May,
which means 10th day from
Chernobyl accident.
The race started and I would
not have like to go there.
But I think, impacts on Slovakia
were not so significant.
Unfortunately, health impacts on people,
who were dealing with the accident,
musty fire workers were frequently fatal.
I have been talking about
acute radiation syndrome.
So, 106 patients have survived,
28 died in first months.
Thyroid cancer.
Good curability does not interest
anyone, who suffers from it.
Often, it has to be solved
through thyroid surgery.
There were lot of these surgeries
and 9 children unfortunately died of it.
Mainly in Belarus.
If we compare released radioactivity
from Chernobyl, we see 10 to the 15 Bq,
for example, with Windscale accident,
it was dramatically higher.
With Fukushima accident,
there it is almost comparable,
but after all, was multiple bigger,
from released radioactivity of
individual isotopes point of view.
Most significant is the
Cesium-137,
which replaces Sodium and
Potassium in human body
and Strontium-90,
which replaces Calcium in bones.
With approximately 30 years
of half-life,
what is not negligible,
that it would decay quickly,
these are the worst isotopes from
impact on human body point of view.
So, you see in comparison with
nuclear weapon tests
it is hundred times less.
Nobody protested again
nuclear weapon tests.
Maybe it was not even
possible that time
and maybe no one had
knowledge about it,
but Chernobyl accident are
emphasized in media till today.
This is everything from my side
and I am ready for discussion.
I told myself to try to make
it in one hour,
it 59 minutes from the beginning.
Here you are.
I have got even more slides.
I see many experts here,
these are wise, generally gray heads,
which you can see around.
So definitely many people can
add or extend certain thesis
and the thesis is mainly:
What has changed from
Chernobyl after 30 years.
That is, why so big emphasis
was on the measures,
on the new safety systems,
new philosophy,
novel approach to the safety,
which has been developed mainly
in 90ies and it still goes on.
Fukushima came, it still goes on.
So whoever has a question,
here you go.
Because, if you won't ask
I will go on.
Ok. Till you find the courage,
I have here few slides to think about.
On the x axis we have time scale,
on the y axis number of
reactor years of operation
So, Three Mile Island was
in 1979 and Chernobyl in 1986.
>From Chernobyl till Fukushima,
more than 11 000 reactors
years of operation passed.
More than 400 block were
in operation,
when it is multiplied with 25
years, 437 blocks,
it is about 11 000.
It means, if we would have
put it in denominator,
the probability of accident
is really on level 10 to the minus 5.
So, as if Fukushima accident was
logical statistical consequence,
which is valid.
But it must be said, the great
difference between Chernobyl,
which was structural error in combination
with errors of operational personnel,
Fukushima accident was caused
by natural disaster -
earthquake and following
tsunami wave.
So, external factor.
Chernobyl was maybe the last
nuclear accident,
where operational personnel or
technology failure parted.
In Chernobyl, it was really error
of design in combination
with operational stuff.
But Fukushima, it was natural
disaster with fatal consequences.
Maybe, we would have secured
the Fukushima project much better
with the preparation for
severe accident,
those sever accident
management guidelines.
They would have reacted to this.
This would be next lesson learned.
But Chernobyl was the last
nuclear accident this big.
Since then, safety systems or training
of operational personnel achieved elevated level.
It is impossible to rule the
accident out for 100 %.
Probability 10 to the minus 8,
to the minus 9 exist
but we see that the accident
from this reason -
personnel or technology
failure, did not happen.
Fukushima is in another
category.
That is the first remark.
Maybe you agree, maybe you don't.
Next myth, I would like to refute
is that everybody says:
Chernobyl meant the
end of nuclear energetics.
Nope! These are counts of reactor
on individual continents in construction.
And you see, that Chernobyl,
which happened at the time of
Mochovce 3,4 construction beginning,
the curve goes downwards. Number
of reactor in construction was decreasing.
Over and above, the decision
about construction
must forego actual digging, concreting
and iron pulling for some years,
because certain legislative acts and
acceptations have to be made.
Today it is maybe 10 - 15 years,
in the 70ies it was maybe only 5 years
so, it was shorter.
But the decision for construction
is important.
As if I would shift this 5
years direction left.
Chernobyl did not mean decision
to stop construction of new power plants.
But maybe it had negative
influence in certain cases.
Here, I have few examples
of energetics accidents
but I don't want to talk
about them any further.
Here is the INES scale.
International Nuclear
Event Scale.
Abruptly after Chernobyl
people were astonished:
How do we rate the accidents,
when we now nothing about them?
When we don't have
a tool to categorize them?
Decision was made to
create sort of scale,
accessible and understandable
for wide public,
where will be defined, how
to sense individual anomalies,
incidents and accidents.
You see it rises on the pyramid
until severe accident like Chernobyl.
The most important
is defense in depth.
It is strategy, safety concept,
it is philosophical approach,
defense in depth,
having always a solution
even a plan B.
During lectures, I always
recommend students
to watch movie The Bodyguard
with Kevin Costner,
if they want to know something
about defense in depth.
He always had plan B.
And similar approach is
in the defense in depth
in nuclear safety.
I anticipate, that the
technology can fail.
It fails in operation.
I have reserve or redundant
operational safety systems.
I invest loads of money,
they must work all the time,
so, I test them but this
is at the level 2.
After Chernobyl, we shifted
in emphasis on level 4,
which means control of
accident process.
So, it will not develop to the
uncontrollable stage.
After Chernobyl, redundancies
of emergency systems were made,
which could work maybe
once in million years,
in case of accident, so I would
manage situation
in case of beyond design
accident.
INSAG-3 which was innovated
in 1999 with INSAG-12,
defined safety goals,
procedures, approaches
and recommended everything
to national regulatory bodies,
which incorporated it afterwards
to the nuclear regulations
on national legislation level.
Here are the affected areas.
I have been talking
about this earlier.
After Chernobyl, totally different
concept started to be developed,
through the defense in depth
in physics resistance or in
inherent safety,
based on physics principles
of all these nuclear installations.
Concept Estimated Simplified
Boiling Reactor was created,
which haven’t been constructed yet,
but it is interesting
by not having any
main coolant pumps,
everything is based on natural
water circulation.
Backups of individual system
are growing.
Diversification of individual
safety systems has grown big.
Generally, I have
independent systems.
Certain measures have been
accepted and here you see
few proposals to increase safety.
Robust cooling system.
Natural circulation, which
works in all circumstances.
Next, decrease power density.
Decrease of components number,
because the more components,
the higher probability of failure.
The more things, the more
frequent failures.
Usage of improved materials.
Reactor must have, negative
thermal and void feedback.
Increase protection of pressure
vessel against embrittlement.
And so on.
This is where I will stop
and let's talk about what bothers
you in coherence with Chernobyl.
So, here you go.
Q: If I understood properly, three
other blocks were left in operation.
Q: Weren't the workers endangered
somehow, because of contamination?
Yes, they were to some extent.
I have not been working
in Chernobyl.
So, I cannot judge it accurately.
What has to be known is that
after accident area decontamination followed,
which means bulldozers removed
everything what was possible,
in radius of 5 - 10 km,
20 - 30 cm of soil has been removed,
roads have been decontaminated
by washing out regularly.
Next, when shift went there,
I think, the other blocks
begun to operate in September 1986.
They went there by
air-conditioned buses,
they had masks for sure
in the initial stages,
went 20 for meters
inside of blocks,
which were also air-conditioned
and there was probably cleaner
surroundings than in the outside.
So, they had precautions
to make it possible to operate.
Chernobyl nuclear power plant
meant 8 % of energetic consumption
of Ukraine.
It is not much, neither too few.
Maybe it was necessity
for Ukraine to operate it further.
Yes, it was operated, special
systems were installed there
but I don't know exact realization.
I did not work there.
Hand down, there you are.
Yes you.
Q: The rusty forest became rusty
because of the radiation?
Well, rusty forest.
Of course, it was affected
by fire of graphite
and by radioactive fallout.
I can't explain the red color
but associate professor Hinca
saw it, was there, measured there,
Robo why it was red? Where are you?
He left already.
Well, you were there in Chernobyl
Gabo, why is it so?
How red, how rusty it was?
A: It was not so red for me.
Mr. Rohar at the rear has the answer.
Plutonium.
Increased concentration of Plutonium
can cause something like this.
There you go.
Q: I would like to hear your opinion on
Q: why the hygienic controls
started to be made so late oater 1986?
Q: That is first thing.
Q: Next one, why is it rusty?
Q: I have been poisoned,
i have been in Tatras at the time,
Q: on a school trip, we had
various illnesses and gangrene.
Q: So, your opinion on the
impact, how much of it was here.
Hygienic service monitored it
but try the beginning of the question
once more, we overheard it
here in front.
Q: How much it affected Slovakia
after the cloud flew over central Europe?
Q: We were at cottage, and we have
been told not to drink from the streams.
Q: So, what is your opinion.
I will begin with my opinion
and there are more experts here,
who probably measured it,
so, maybe somebody will add
to my answer.
Slovakia was affected at the time
till 1.7 mSv over natural
background level.
When each year each person
received 2.4 Sv, 1.7 was added to it.
It is within the range, in which
you can get 5 mSv
added to background
in five years.
This norm has not been crossed.
Next, hygienists told, milk level
won’t be 2000 but 1000 Bq per liter.
So, they lowered the limit to half
and I know in some locations,
they used the milk production
for durable cheeses,
so if Iodine-131 or other
short-lived isotopes were present,
they would decay.
Regarding water, I don't thing
measured water exceeded the limit.
So nowhere was limit
that you cannot drink from here.
Maybe it was not recommended
to harvest mushrooms,
because after rain,
mainly in the first year
they could suck in
more Cesium.
But no special restrictions
were in Slovakia
or long-time restriction
for grocery.
Because the fallout in
Slovakia was not remarkable.
Now someone will add to this.
Ms. associate professor
Cabanekova maybe
or she will agree with
what I said.
So, there you go.
A: Regarding population
protection:
A: It is a fact that lot of
reparation measures were made.
A: It is a fact, people did not
know about it.
A: Regarding that time regime,
sometimes I think is better
because there were no
worries and panic.
But the measures were made.
A: Measures were made for
critical groups of population.
A: Iodine profile axion have been
applied in the areas,
A: where workers have
been outside.
A: Measures were made in terms
of animals and cattle
A: have not been
shepherded outside,
A: it was stabled inside.
A: As professors said, milk with high
Iodine concentration was stored,
A: to wait for decay.
A: Milks that have been produced
from localities, where it rained
A:and with higher concentration
have not been placed on the market.
A: Only clean milk has been
supplied for the consumption market.
A: So, measures have been made.
A: And according to the needs,
based on real monitoring results.
Well.
Here you are, next thesis.
Peter Uhrik.
Nuclear Regulatory Authority
of the Slovak republic.
A: Good afternoon, my name is
Peter Uhrik. I work at
A: Nuclear Regulatory Authority
of the Slovak republic
A: and maybe one interesting
facto to fulfill from the time.
A: In 1986, I have been working as
operator in control room.
A: At Nuclear power plant V2
in Jaslovske Bohunice.
A: And
A: it has been remarkable year for
me because I married that year.
A: It came to my mind because
Mr. at the rear asked if water
A: was contaminated.
A: I know about one
contaminated water.
A: It was circulating coolant
water, which is in principle
A: cooled down in cooling towers
in nuclear power plant.
A: These are the big towers,
you can see from big distance
A: and where the water is
cooled in the way,
A: it is fed with circulation pumps
into the middle of cooling tower,
A: exactly to the one third of
tower height,
A: where it is spread to all sides
and rains down.
A: By placement of the
tower on the legs,
A: remarkable chimney effect
is created there,
A: so, cold air is pulled up against
which moves heated water
A: from technology of
nuclear power plant.
A: By this process certain amount
of water is evaporated.
A: I think, it is up to two thirds of volume,
I don't remember it accurately anymore.
A: 2000 tons per hour,
so, enormous volume.
A: This water is cooled down
like this.
A: But this is only one process.
A: Another one is that the air, which
comes through the cooling tower
A: is excellently "washed through".
A: When nuclear power plant
was in operation,
A: the air which was in close
range to power plant
A: and which was contaminated by
crossing of radioactive cloud from Chernobyl,
A: was washed through in a way
A: and certain elements
accumulated in this cooling water.
A: Circulating cooling water is
connected with
A: important technical water
by pipelines
A: and important technical water
is used among the others
A: for cooling down of dosimetry
systems in nuclear power plant.
A: We were really surprised
at the time
A: because through normal
block operation,
A: abruptly signalization came
to the control room
A: and higher activity of steam was
measured in one of steam generators.
A: We were scared a little bit
A: because, same as other people
in Slovakia, we did not receive
A: any information about
Chernobyl and cloud.
A: This was few days after accident,
it was not the first day!
A: We did not have any valid
information
A: about what is going on.
A: And signalization from steam
generator came.
A: Normal response of operators
in this case
A: is to look for
the indication sources
1157
01:19:39,600 --> 01:19:39,232
A: whether there are some leaks.
A: Operator firstly controlled all
the pressures, temperatures,
A: levels in vessels to confirm,
that we don’t spill the water
A: and the activity is not caused
by the leakage in steam generator.
A: Than signalization on 2nd,
3rd and 4th steam generator came
A: and reason was searched
of course, somewhere else.
A: And here, the colleague of
mine has just crossed himself
A: it was not entirely
like that.
A: And after it information came about
radioactive cloud from Chernobyl
A: and the signalization is caused by
contamination of cooling water,
A: which cooled dosimetry
sensors on steam generator.
A: This is my personal experience
with Chernobyl accident.
A: Fortunately, I have no more
experiences with it.
A: Here you are, in case of
questions.
Q: I would like to discuss about
Fukushima.
Q: It is real case for disputation,
because you said,
Q: that Chernobyl was the last
accident caused by technology
Q: and human factor failure.
It is true, there were some
little accidents but not so significant.
Q: But from the point of view
of Fukushima.
Q: Of course, initiation was external,
it was natural disaster
Q: but impacts caused, were
proven to be consequence
Q: of bad safety culture in Japan as well.
Q: They even admitted it afterwards,
it was error of their hierarchical system,
Q: where they were scared to talk
and point to the fact,
Q: that tsunami like that were
in the locality, already
Q: and we must prove it here
that our power plants
Q: will be able to withstand it.
Q: But they did not.
Q: The analysis have been postponed.
Q: Until this happened.
Q: So, this was one from the
reasons and based on this,
Q: we had to accept and check
some of our measures,
Q: that we are ready
for all circumstances.
Q: We cannot have tsunami here,
but other external impacts
Q: like high temperature,
low temperature
Q: earthquakes
and so on.
Q: So, other aspects have been
there, not only fatalistic approach,
Q: that God or nature hit against
our good technology.
I agree, you are right.
There you go Mr. Rohar.
Q: It is about Japanese accident,
which was inspected by commission
Q: with clear conclusion,
that this accident was caused
Q: by human factor.
Thank you.
More questions, remarks
or completions?
When somebody says,
my jams are rotting
due to Chernobyl,
it won’t be probably truth.
So, Mr. Rohar one more remark.
Q: Consequences of Chernobyl
here in Slovakia
Q: are about the fact, that agency
reacted, created safety assessment program
Q: for nuclear power plants.
Q: They released recommendations
and all our power plants paid
Q: billions of crowns and maybe billions
euro for the safety enhancements
Q: of all our nuclear plants.
Q: So, this is one of Chernobyl
consequences.
Practically, accidents and disasters
are engines for progress.
But, this engine in Chernobyl
did not have to be started
because the consequences
were enormous.
Many times, we start to care
about things after notification
and Chernobyl pointed out
on project design so, structure
or on some of operator dos.
Q: In other areas, as well.
This is valid in each area.
Exactly.
Well. If there is no more
question or remark
I thank you all for coming
here in your free time
on academic soil.
And I trust that lectures like this
will not be given as a consequence
of accident but as a consequence
of good operation of nuclear sources
maybe we could do next presentation
after bringing Mochovce 3,4 to operation,
what we expect year after year.
