The nuclear reactor after the disaster. Reactor 4 (centre). Turbine
building (lower left). Reactor 3 (centre right).
26 April 1986 (1986-04-26)
01:23 a.m. (UTC+3)
56 direct deaths
600,000 (est) suffered radiation exposure, which may result in as many
as 4,000 cancer deaths over the lifetime of those exposed, in addition
to the approximately 100,000 fatal cancers to be expected due to all
other causes in this population.
The Chernobyl disaster was a nuclear reactor accident that occurred on
26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine (then part
of the Soviet Union). It is considered to be the worst nuclear power
plant disaster in history and the only level 7 event on the
International Nuclear Event Scale. It resulted in a severe release of
radioactivity following a massive power excursion that destroyed the
reactor. Most deaths from the accident were caused by radiation
On 26 April 1986 at 01:23 a.m. (UTC+3) reactor number four at the
Chernobyl plant, near Pripyat in the Ukrainian Soviet Socialist
Republic, exploded. Further explosions and the resulting fire sent a
plume of highly radioactive fallout into the atmosphere and over an
extensive geographical area. Four hundred times more fallout was
released than had been by the atomic bombing of Hiroshima.
The plume drifted over large parts of the western Soviet Union,
Eastern Europe, Western Europe, and Northern Europe, with some nuclear
rain falling as far away as Ireland. Large areas in Ukraine, Belarus,
and Russia were badly contaminated, resulting in the evacuation and
resettlement of over 336,000 people. According to official post-Soviet
data, about 60% of the radioactive fallout landed in Belarus.
The accident raised concerns about the safety of the Soviet nuclear
power industry as well as nuclear power in general, slowing its
expansion for a number of years while forcing the Soviet government to
become less secretive. The countries of Russia,
Ukraine, and Belarus have been burdened with the continuing and
substantial decontamination and health care costs of the Chernobyl
accident. It is difficult to accurately quantify the number of deaths
caused by the events at Chernobyl, as over time it becomes harder to
determine whether a death has been caused by exposure to radiation.
The 2005 report prepared by the Chernobyl Forum, led by the
International Atomic Energy Agency (IAEA) and World Health Organization
(WHO), attributed 56 direct deaths (47 accident workers, and nine
children with thyroid cancer), and estimated that there may be 4,000
extra cancer deaths among the approximately 600,000 most highly exposed
people.] Although the Chernobyl Exclusion Zone and certain limited areas
remain off limits, the majority of affected areas are now considered
safe for settlement and economic activity.
Location of the Chernobyl Nuclear Power Plant.
The Chernobyl station is near the town of Pripyat, Ukraine, 18 km (11
mi) northwest of the city of Chernobyl, 16 km (10 mi) from the border of
Ukraine and Belarus, and about 110 km (68 mi) north of Kiev. The station
consisted of four RBMK-1000 nuclear reactors, each capable of producing
1 gigawatt (GW) of electric power, and the four together produced about
10% of Ukraine's electricity at the time of the accident. Construction
of the plant began in the late 1970s, with reactor no. 1 commissioned in
1977, followed by no. 2 (1978), no. 3 (1981), and no. 4 (1983). Two more
reactors, no. 5 and 6, also capable of producing 1 GW each, were under
construction at the time of the disaster.
On 26 April 1986 at 1:23 a.m., reactor 4 suffered a massive,
catastrophic power excursion (the chain reaction grew out of control,
similar to the initial stage in the detonation of a nuclear weapon).
This caused a steam explosion, followed by a second (chemical, not
nuclear) explosion from the ignition of generated hydrogen mixed with
air, which tore the top from the reactor and its building, and exposed
the reactor core. This dispersed large amounts of radioactive
particulate and gaseous debris containing cesium-137 and strontium-90
which are highly radioactive reactor waste products. The open core also
allowed air (oxygen) to contact the super-hot core containing 1,700
tonnes] of combustible graphite moderator. The burning graphite
moderator increased the emission of radioactive particles, carried by
the smoke. The reactor was not contained by any kind of hard containment
vessel (unlike most Western plants, Soviet reactors often did not have
them). Radioactive particles were carried by wind across international
Planning the test of the safety device
During the daytime of 25 April 1986, reactor 4 was scheduled to
be shut down for maintenance as it was near the end of its first fuel
cycle. An experiment was proposed to test a safety emergency core
cooling feature during the shut down procedure.
A very large amount of cooling water is needed to maintain a safe
temperature in the reactor core. The reactor consisted of about 1,600
individual fuel channels and each operational channel required a flow of
28 tons of water per hour. There was concern that in case of an external
power failure the Chernobyl power station would overload, leading to an
automated safety shut down in which case there would be no external
power to run the plant's cooling water pumps. Chernobyl's reactors had
three backup diesel generators. The generator required 15 seconds to
start up but took 60–75 seconds to attain full speed and reach its
capacity of 5.5 MW required to run one main cooling water pump.
The nuclear reactor needs coolant even when not actively operating.
In case of an external power failure, the reactor would automatically
scram; control rods would be inserted and stop the nuclear fission
process (and hence steam generation). However, in the spent fuel, the
fission products themselves were highly radioactive, and continued to
produce heat as they decayed. This could amount to 1-2 percent of the
normal output of the plant. If not immediately removed by coolant
systems, the heat could lead to core damage.
This one-minute power gap was considered unacceptable and it was
suggested that the mechanical energy (rotational momentum) of the steam
turbine could be used to generate electricity to run the main cooling
water pumps, while it was spinning down. In theory, it should have been
able to provide power for 45 seconds and thus bridge the power gap
between the onset of the external power failure and the full
availability of electric power from the emergency diesel generators, but
it needed to be tested. All previous tests ended unsuccessfully. The
very first test in 1982 showed that the system voltage of the
turbine-generator required refinement, it did not maintain the desired
magnetic field during the rotation slowdown. The system had been
refined, and in 1984 the test was repeated, but it also proved
unsuccessful. In 1985 the test was attempted a third time, but it also
gave no results. The exact same program was tested again in 1986.
The experiment concerned only different switchings in the electrical
chains of power unit. Since the reactor was scrammed automatically at
the very beginning of the experiment (as soon as it ceased to feed steam
to the turbine,) the experiment should not have had any detrimental
effect on the safety of the reactor. Therefore, the test program was
apparently not coordinated with either the chief designer of the
reactor, nor with the scientific manager. Instead, it was approved only
by the director of the plant (and even this was done incorrectly).
According to the test parameters, at the start of the experiment, the
thermal output of the reactor should have been no lower than 700 MW. If
the conditions of the reactor had been as planned, the test likely would
have proceeded safely, as the eventual disaster resulted from unplanned
attempts to boost the inadequate reactor output once the experiment had
The Chernobyl power plant had been in operation for two years without
this important safety feature. The station managers must have wished to
correct this at the first opportunity. This could explain why they were
so determined to carry out the test, even when serious problems arose,
and why the requisite approval for the test was not sought from the
Soviet nuclear oversight regulatory body.
For the experiment, the reactor would be set at a low power setting
and the steam turbine run up to full speed, at which point the steam
supply would be closed off and the turbines allowed to freewheel, as the
results were recorded.
The Chernobyl disaster
Conditions prior to the accident
Conditions to run the test were prepared prior to the day shift
of 25 April 1986. The day shift workers had been instructed in advance
about the test and were familiar with procedures. A special team of
electrical engineers was present to test the new voltage regulating
system. As planned, on 25 April a gradual reduction in the output of the
power unit was begun at 01:06, and by the beginning of the day shift the
power level had reached 50%. Another regional power station unexpectedly
went off line, and the Kiev grid controller requested that the further
reduction of Chernobyl's output be postponed, as power was consequently
needed to satisfy the evening peak demand. The Chernobyl plant director
agreed and postponed the test to comply.
At 11:04 p.m., the Kiev grid controller allowed the reactor shut-down
to resume. This delay had some serious consequences: the day shift had
long since departed, the evening shift was also preparing to leave, and
the night shift wouldn't take over until 12:00 midnight, well into the
job. Further rapid reduction in the power level from 50% was actually
executed during the shift change-over. The special team of electrical
engineers must have been exhausted from the long wait; according to
plan, the test should have been finalized during the daytime and the
night shift would only have had to maintain basic cooling systems in a
plant otherwise shut down; the night shift had very limited time to
prepare and carry out the experiment. Alexander Akimov was chief of the
night shift and Leonid Toptunov was the operator responsible for the
reactor's operational regime, including the movement of the control
rods. Toptunov was a young engineer who had worked independently as a
senior engineer for about only three months.
An emergency would not have occurred if the regulations were
followed. The operators of the power plant and the conductors of the
experiment on the No. 4 reactor held too much faith in the reactor; to
them, a catastrophe was simply inconceivable. Because of this, they had
no qualms about disabling the safety features of the reactor and taking
unnecessary risks to carry out the experiment.
The test plan called for the power output of reactor 4 to be reduced
from its nominal 3200 MW thermal to 700–1000 MW thermal. The power level
established in the test program (700 MW) was achieved at 00:05 on 26
April; however, due to the natural production of a neutron absorber in
the core, Xenon-135, reactor power continued to lower, even without
operator action. As the power reached approximately 500 MW, Toptunov
committed an error and inserted the control rods too far, bringing the
reactor to a near shutdown. The exact circumstances will probably never
be known as both Akimov and Toptunov died from radiation sickness.
The reactor power dropped to 30 MW thermal (or less)—almost complete
shut down level and approximately 5 percent of what was expected.
Control room personnel made a decision to restore the power and
extracted the reactor control rods, though several minutes lapsed after
their extraction until the power output began to increase and
subsequently stabilize at 160-200 MW (thermal). In this case the
majority of control rods proved to be on their upper limits, the low
value of the operational reactivity margin restricted further rise of
reactor power. Rapid reduction in the power and subsequent work at the
level of less than 200 MW led to that increased poisoning reactor core
by the isotope of xenon-135, which made it necessary to additionally
extract control rods from the reactor core.
The operation of the reactor at the low level of power with the small
reactivity margin was accompanied by the instability of the
thermohydraulic parameters and possibly by the instability of neutron
flux. The control room received repeated emergency signals on the levels
in the separator drums, the opening of the reduction valves which allow
excess steam into a turbine condenser, large overregulation in the flow
rate of feed water, and warning signals about the controllers of neutron
power. For this very reason in the period 00:35 on 00:45, apparently, in
order to preserve the reactor power level, emergency signals were
ignored from the thermal-hydraulic parameters and signals from the
Reactor Emergency Protection System (AZ-5) appeared on, turning off both
After reaching more or less stable state at the level of the power of
200 MW the preparation for the experiment was continued. As part of the
test plan, at 1:05 a.m. on 26 April extra water pumps were activated,
increasing the water flow. The increased coolant flow rate through the
reactor produced an increase in the temperature of heat-transfer agent
at the entrance into the reactor core, which approached the temperature
of the beginning of the effervescence of water. The flow exceeded the
allowed limit at 1:19 a.m. From the other side the extra water lowered
the core temperature and reduced steam voids. Since water also absorbs
neutrons (and the higher density of liquid water makes it a better
absorber than steam), it causes tendency to decrease the reactor power,
prompting the operators to remove the manual control rods.
All these actions led to an extremely dangerous condition with nearly
all of the control rods removed, a setup for a runaway reaction, as it
was explained after emergency.
Experiment and explosion
Aerial view of the damaged core.
Roof of the turbine hall is damaged (image centre).
Roof of the adjacent reactor 3 (image lower left) shows minor fire
At 1:23:04 a.m. the experiment began, the steam to the turbines was shut
off, and a run down of the turbine generator began, together with four
(from the total number of eight) Main Circulating Pumps (MCP). Start-up
of the diesel generator and stepped pick-up of load ended by 01:23:43
and in this period power supply to these four MCPs was achieved due to
the run down of the turbine generator. As the momentum of the turbine
generator drove the water pumps, the water flow rate decreased, leading
to the formation of steam voids. Because of the positive void
coefficient of the RBMK reactor, it was now primed to embark on a deadly
positive feedback loop, in which the formation of steam voids decreased
the ability of the liquid water coolant to absorb neutrons, which led to
a tendency towards an increase in the reactor's power output, causing
yet more water to flash into steam, and yet more positive reactivity
appearing in the reactor. However, in almost the entire period of the
experiment the automatic control system successfully counteracted this,
continuously inserting control rods into the reactor core.
At 1:23:39 (at 1:23:40 by the time of the centralized control system
“SKALA”) the AZ-5 button of the reactor emergency protection system was
pressed, which ordered a "SCRAM"—a shutdown of the reactor, fully
inserting all control rods, including the manual control rods that had
been incautiously withdrawn earlier. The reason why the AZ-5 button was
pressed has not been reliably verified and this gives occasion for
different interpretations, whether it was done as an emergency measure,
or simply as a routine method of shutting down the reactor upon the
completion of the experiment. There is a view that the SCRAM may have
been ordered as a response to the unexpected rapid power increase;
although there is no recorded data which convincingly testifies to this.
Moreover, doubts have been expressed about the question as to whether
the button was pressed at that moment. And it is asserted that the
signal was not from the button but was automatically produced by the
emergency protection system without any operator’s help. But, at the
same time, SKALA clearly registered a signal from the button itself. In
spite of all this, the question as to when the AZ-5 button was pressed
(and indeed whether it really was pressed) is still the subject of
debate. There are assertions that the pressure was caused by the rapid
power acceleration at the start. It is alleged furthermore that the
button was pressed during the time of the destruction of the reactor.
According to other assertions, it happened earlier and was performed in
Dyatlov writes in his book:
Prior to 01:23:40, systems of centralized control … did not register
any parameter changes that could justify the SCRAM. The Commission …
gathered and analyzed large amounts of material and, as stated in its
report, failed to determine the reason why the SCRAM was ordered. There
was no need to look for the reason. The reactor was simply being shut
down upon the completion of the experiment.
For whatever reason the SCRAM (AZ-5) command was executed, insertion
of control rods into the reactor core began. The control rod insertion
mechanism operated at a relatively slow speed (0.4 m/s) taking 18–20
seconds to travel the full approximately 7 meter core-length (height). A
bigger problem was a flawed graphite-tip control rod design, which
initially displaced coolant, before the reaction was slowed. In this
way, the SCRAM actually increased the reaction rate. At this point a
massive energy spike occurred, and the core overheated. Some of the fuel
rods fractured, blocking the control rod columns, and causing the
control rods to become stuck after being inserted only one-third of the
way. Within three seconds the reactor output rose above 530 MW. The
subsequent course of events was not registered by instruments: it is
known only as the result of mathematical simulation. According to some
estimations, the reactor jumped to around 30 GW thermal, ten times the
normal operational output but not immediately. First a great rise in
power caused the rise of fuel temperature and massive steam buildup with
rapid increasing in steam pressure. All that destroyed fuel elements and
ruptured channels in which these elements located.
No coherent view exists as to the precise sequence of the processes
that led to the destruction of the reactor and the power unit building.
There is a general understanding that it was steam from the wrecked
channels entering the reactor inner space that caused the destruction of
the reactor casing, tearing off and lifting by the force of 2,000 tons
the upper plate (to which entire reactor assembly is fastened).
Apparently this was the first explosion, which many heard. This was a
steam explosion like the explosion of a steam boiler from the excess
pressure of vapor. This ruptured further fuel channels, the reactor core
suffered total water loss and a high positive void coefficient could
entirely appear. A second, more powerful explosion occurred about two or
three seconds after the first.
There are different points of view regarding the nature of this
explosion. There is the view that "the second explosion was caused by
the hydrogen which had been produced either by the overheated
steam-zirconium reaction or by the reaction of red-hot graphite with
steam that produce hydrogen and oxygen". According to another
hypothesis, this was an explosion of a nuclear nature, i.e., the thermal
explosion of the reactor as a result of the uncontrollable escape of
fast neutrons, caused by the complete water loss in the reactor core.
The high positive void coefficient makes this version of the emergency
entirely plausible. Finally, there is a version that the explosion was
caused, exceptionally, by steam. According to this version, the flow of
steam and the steam pressure caused all the destruction following the
ejection from the shaft of the substantial part of the graphite and
According to observers outside Unit 4, burning lumps of material
and sparks shot into the air above the reactor. Some of them fell onto
the roof of the machine hall and started a fire. About 25 per cent of
the red-hot graphite blocks and overheated material from the fuel
channels was ejected. ... Parts of the graphite blocks and fuel channels
were blown out of the reactor building. ... As a result of the damage to
the building an airflow through the core was established by the high
temperature of the core. The air ignited the hot graphite and started a
The graphite fire greatly contributed to the spread of radioactive
material and the contamination of outlying areas.
Contrary to safety regulations, a combustible material (bitumen) had
been used in the construction of the roof of the reactor building and
the turbine hall. Ejected material had ignited at least five fires on
the roof of the (still operating) adjacent reactor 3. It was imperative
to put those fires out and protect the cooling systems of reactor 3.
Inside reactor 3, the chief of the night shift, Yuri Bagdasarov, wanted
to shut down the reactor immediately, but chief engineer Nikolai Fomin
would not allow this. The operators were given respirators and potassium
iodide tablets and told to continue working. At 05:00, however,
Bagdasarov made his own decision to stop the reactor, leaving only those
operators there who had to work the emergency cooling systems.
The Chernobyl disaster
Immediate crisis management
The radiation levels in the worst-hit areas of the reactor
building have been estimated to be 5.6 röntgen per second (R/s) (0.056
Grays per second, or Gy/s), which is equivalent to 20,000 röntgen per
hour (R/hr) (200 Gy per hour, or Gy/hr). A lethal dose is around 500
röntgen (5 Gy) over 5 hours, so in some areas, unprotected workers
received fatal doses within several minutes. However, a dosimeter
capable of measuring up to 1,000 R/s (10 Gy/s) was inaccessible due to
the explosion, and another one failed when turned on. All remaining
dosimeters had limits of 0.001 R/s (0.00001 Gy/s) and therefore read
"off scale". Thus, the reactor crew could ascertain only that the
radiation levels were somewhere above 0.001 R/s (3.6 R/hr, or 0.036 Gy/hr),
while the true levels were much higher in some areas.
Because of the inaccurate low readings, the reactor crew chief
Alexander Akimov assumed that the reactor was intact. The evidence of
pieces of graphite and reactor fuel lying around the building was
ignored, and the readings of another dosimeter brought in by 4:30 a.m.
were dismissed under the assumption that the new dosimeter must have
been defective. Akimov stayed with his crew in the reactor building
until morning, trying to pump water into the reactor. None of them wore
any protective gear. Most of them, including Akimov, died from radiation
exposure within three weeks.
Shortly after the accident, firefighters arrived to try to
extinguish the fires. The first one to the scene was a Chernobyl Power
Station firefighter brigade under the command of Lieutenant Vladimir
Pravik, who died on 9 May 1986 of acute radiation sickness. They were
not told how dangerously radioactive the smoke and the debris were, and
may not even have known that the accident was anything more than a
regular electrical fire: "We didn't know it was the reactor. No one had
Grigorii Khmel, the driver of one of the fire-engines, later
described what happened:
We arrived there at 10 or 15 minutes to two in the morning ... We saw
graphite scattered about. Misha asked: What is graphite? I kicked it
away. But one of the fighters on the other truck picked it up. It's hot,
he said. The pieces of graphite were of different sizes, some big, some
small enough to pick up ...
We didn't know much about radiation. Even those who worked there had no
idea. There was no water left in the trucks. Misha filled the cistern
and we aimed the water at the top. Then those boys who died went up to
the roof - Vashchik Kolya and others, and Volodya Pravik ... They went
up the ladder ... and I never saw them again.
The immediate priority was to extinguish fires on the roof of the
station and the area around the building containing Reactor No. 4 to
protect No. 3 and keep its core cooling systems intact. The fires were
extinguished by 5 a.m., but many firefighters received high doses of
radiation. The fire inside Reactor No. 4 continued to burn until 10 May
1986; it is possible that well over half of the graphite burned out. The
fire was extinguished by a combined effort of helicopters dropping over
5,000 tonnes of materials like sand, lead, clay and boron onto the
burning reactor and injection of liquid nitrogen. Ukrainian filmmaker
Vladimir Shevchenko captured film footage of a Mi-8 helicopter as it
lost its bearings while dropping its load and got its rotors tangled in
the gibbets of a nearby construction crane, causing the wrecked
helicopter to fall near the damaged reactor building and kill its
From eyewitness accounts of the firefighters involved before they
died (as reported on the CBC television series Witness), one described
his experience of the radiation as "tasting like metal", and feeling a
sensation similar to that of pins and needles all over his face. (This
is similar to the description given by Louis Slotin, a Manhattan Project
physicist who died days after a fatal radiation overdose from a
The explosion and fire threw particles of the nuclear fuel and also
far more dangerous radioactive elements like caesium-137, iodine-131,
strontium-90 and other radionuclides into the air: the residents of the
surrounding area observed the radioactive cloud on the night of the
The abandoned city of Pripyat with Chernobyl plant in the distance.
Evacuation of Pripyat
The nearby city of Pripyat was not immediately evacuated.
Only after radiation levels set off alarms at the Forsmark Nuclear
Power Plant in Sweden did the Soviet Union admit that an accident
had occurred, but authorities attempted to conceal the scale of the
disaster. To evacuate the city of Pripyat, the following warning message
was reported on local radio: "An accident has occurred at the Chernobyl
Nuclear Power Plant. One of the atomic reactors has been damaged. Aid
will be given to those affected and a committee of government inquiry
has been set up." This message gave the false impression that any damage
and radiation was localized.
The government committee formed to investigate the accident, led by
Valeri Legasov, arrived at Chernobyl in the evening of 26 April. By that
time two people were dead and 52 were in the hospital. During the night
of 26 April / 27 April—more than 24 hours after the explosion—the
committee, faced with ample evidence of extremely high levels of
radiation and a number of cases of radiation exposure, had to
acknowledge the destruction of the reactor and order the evacuation of
the nearby city of Pripyat.
The evacuation began at 14:00, 27 April. To reduce baggage, the
residents were told the evacuation would be temporary, lasting
approximately three days. As a result, Pripyat still contains personal
belongings. An exclusion zone of 30 km/19 mi remains in place today.
Evacuation of Pripyat.
Steam explosion risk
There was a bubbler pool beneath the reactor. It served as a
large water reservoir from the emergency cooling pumps and as a pressure
suppression system capable of condensing steam from a (small) broken
steam pipe. The pool and the basement were flooded due to ruptured
cooling water pipes and accumulated fire water. It now constituted a
serious steam explosion risk. The smouldering fuel and other material
above, a corium at more than 1200°C, started to burn their way through
the reactor floor and mixed with molten concrete that had lined the
reactor, creating a radioactive semi-liquid material comparable to lava.
If this mixture had melted through the floor into the pool of water, it
would have created a massive steam explosion which would eject more
radioactive material from the reactor. It became an immediate priority
to drain the pool.
The bubbler pool could be drained by opening its sluice gates. Heroic
volunteers in diving suits entered the radioactive water and managed to
open the gates. These were engineers Alexei Ananenko (who knew where the
valves were) and Valeri Bezpalov, accompanied by a third man, Boris
Baranov, who provided them with light from a lamp, though this lamp
failed, leaving them to find the valves by feeling their way along a
pipe. All of them returned to the surface and according to Ananenko,
their colligues jumped from the happines when they heard they managed to
open the valves. Despite their good condition after the task completion,
all of them suffered from radiation sickness an at least two of them -
Ananenko and Bezpalov - died in the process. Some sources, however,
claim incorrectly that they died in the plant. It is likely that intense
alpha radiation hydrolyzed the water generating a hydrogen peroxide
(H2O2) solution with a low pH, akin to an oxidizing acid. Confirmation
that bubbler pool waters were converted to H2O2 is confirmed by the
identification of the minerals studtite and metastudtite in the
Chernobyl lavas, the only minerals that contain peroxide. Fire brigade
pumps were then used to drain the basement. The operation was only
completed by 8 May, after having pumped out 20,000 tonnes of highly
With the bubbler pool gone, a meltdown was less likely to produce a
powerful steam explosion. In order to do so, the molten core would now
have to reach the water table below the reactor. To reduce the
likelihood of this it was decided to freeze the earth beneath the
reactor; this would also stabilize the foundations. Using oil drilling
equipment, injection of liquid nitrogen began on 4 May. It was estimated
that 25 tonnes of liquid nitrogen per day would be required to keep the
soil frozen at -100 °C.This idea was soon scrapped and the bottom room
where the cooling system would have been installed was filled with
The worst of the radioactive debris was collected inside what was
left of the reactor, much of it shoveled in by liquidators wearing heavy
protective gear (dubbed "bio-robots" by the military); these workers
could only spend a maximum of 40 seconds at a time working on the
rooftops of the surrounding buildings due to the extremely high doses of
radiation given off by the blocks of graphite and other debris. The
reactor itself was covered with bags containing sand, lead and boric
acid thrown off helicopters (some 5,000 metric tonnes during the week
following the accident). By December 1986 a large concrete sarcophagus
had been erected, to seal off the reactor and its contents.
Many of the vehicles used by the "liquidators" remain parked in a
field in the Chernobyl area to this day, most giving off doses of 10-30
R/hr (0.1-0.3 Gy/hr) over 20 years after the disaster.
There were two official explanations of the accident: the first,
subsequently acknowledged as erroneous, was published in August 1986 and
effectively placed the blame on the power plant operators. To
investigate the causes of the accident the IAEA created the advisory
group known as International Nuclear Safety Advisory Group (INSAG) which
as a whole also supported this view, on the basis of the materials given
by the Soviet side and the oral statements of specialists in its report
of 1986 INSAG-1 . It was alleged that the accident which had such
catastrophic consequences was caused by the gross violation of operating
rules and regulations. "During preparation and testing of the turbine
generator under run-down conditions using the auxiliary load, personnel
disconnected a series of technical protection systems and breached the
most important operational safety provisions for conducting a technical
exercise". This was probably due to their lack of knowledge of
reactor physics and engineering, as well as lack of experience and
training. According to these allegations, at the time of the accident
the reactor was being operated with many key safety systems shut off,
most notably the Emergency Core Cooling System (ECCS). Personnel had an
insufficiently detailed understanding of the technical procedures
involved with the nuclear reactor and knowingly infringed regulations in
order to speed up completion of the test.
"The developers of the reactor plant considered this combination
of events to be impossible and therefore did not allow for the creation
of emergency protection systems capable of preventing the combination of
events that led to the crisis, namely the intentional disabling of
emergency protection equipment plus the violation of operating
procedures. Thus the primary cause of the accident was the extremely
improbable combination of rule infringement plus the operational routine
allowed by the power station staff."
By this account, deficiencies in the reactor design and in the
operating regulations that made this accident possible were cast to one
side and mentioned only casually. Serious critical observations covered
only general questions and did not address the specific reasons for the
accident. The following general picture arose from these observations.
Several procedural irregularities also helped to make the accident
possible. One was insufficient communication between the safety officers
and the operators in charge of the experiment being run that night. The
reactor operators disabled safety systems down to the generators, which
the test was really about. The main process computer, SKALA, was running
in such a way that the main control computer could not shut down the
reactor or even reduce power. Normally the reactor would have started to
insert all of the control rods. The computer would have also started the
"Emergency Core Protection System" that introduces 24 control rods into
the active zone within 2.5 seconds, which is still slow by 1986
standards. All control was transferred from the process computer to the
This view is reflected in the numerous publications on the theme of
the Chernobyl accident, in the artistic works that appeared immediately
after the accident and in the long time that it reigned in the public
consciousness and in popular publications. In 1993 the IAEA Nuclear
Safety Advisory Group (INSAG) published an additional report INSAG-7
which reviewed “that part of the INSAG-1 report in which primary
attention is given to the reasons for the accident”. Most of the
accusations against staff for breach of regulations were acknowledged to
be erroneous, based on incorrect information obtained in August 1986.
This report reflected another view of the reasons for the accident,
presented in appendix I.
According to this account, turning off the ECCS, and also interfering
with the settings on the protection equipment and blocking the level and
pressure in the separator drum, did not contribute to the original cause
of the accident and its magnitude, though they were possibly a breach of
regulations. Turning off the emergency system designed to protect
against the stopping of the two turbine generators was not a breach of
regulations. In fact, pushing the button on the AZ-5 emergency
protection system was a normal initial emergency action for damping down
Human factors contributed to the conditions that led to the disaster,
namely working with a small operational reactivity margin (ORM) and
working at a low level of power in the reactor, less than 700 MW - the
level documented in the run-down test program. Nevertheless, working at
this low level of power was not forbidden in the regulations, despite
what Soviet experts asserted in 1986.
Regulations forbade work with a small margin of reactivity. However,
“... post-accident studies have shown that the way in which the real
role of the ORM is reflected in the Operating Procedures and design
documentation for the RBMK-1000 is extremely contradictory” , and more
“ORM was not treated as an operational safety limit, violation of which
could lead to an accident”.
According to this report, the chief reasons for the accident lie in
the peculiarities of physics and in the construction of the reactor.
There are two such reasons:
1.The reactor had a dangerously large positive void
coefficient. The void coefficient is a measurement of how the reactor
responds to increased steam formation in the water coolant. Most other
reactor designs have a negative coefficient, i.e. they attempt to
decrease the heat output in the presence of an increase of the vapor
phase in the reactor, because if the coolant contains steam bubbles,
fewer neutrons are slowed down. Faster neutrons are less likely to split
uranium atoms, so the reactor produces less power (a negative
feed-back). Chernobyl's RBMK reactor, however, used solid graphite as a
neutron moderator to slow down the neutrons, and the water in it, on the
contrary, acts like a harmful neutron absorber. Thus neutrons are slowed
down even if steam bubbles form in the water. Furthermore, because steam
absorbs neutrons much less readily than water, increasing the intensity
of vaporization means that more neutrons are able to split uranium
atoms, increasing the reactor's power output. This makes the RBMK design
very unstable at low power levels, and prone to suddenly increasing
energy production to a dangerous level. This behavior is
counter-intuitive, and this property of the reactor was unknown to the
2. A more significant flaw was in the design of the control rods
that are inserted into the reactor to slow down the reaction. In the
RBMK reactor design, the lower part of the control rods was made of
graphite and was 1.3 meters shorter than necessary and in the space
beneath them were hollow channels filled with water. The upper part of
the rod—the truly functional part which absorbs the neutrons and thereby
halts the reaction—was made of boron carbide. With this design, when the
rods are inserted into the reactor from the uppermost position,
initially the graphite parts displace some coolant. This greatly
increases the rate of the fission reaction, since graphite (in the RBMK)
is a more potent neutron moderator (absorbs far fewer neutrons than the
boiling light water). Thus for the first few seconds of control rod
activation, reactor power output is increased, rather than reduced as
desired. This behavior is counter-intuitive and was not known to the
3. Other deficiencies besides these were noted in the RBMK-1000
reactor design, as were its non-compliance with accepted standards and
with the requirements of nuclear reactor safety.
Both views were heavily lobbied by different groups, including the
reactor's designers, power plant personnel, and by the Soviet and
Ukrainian governments. The IAEA's 1986 analysis attributed the main
cause of the accident to the operators' actions. But Report 1993 of the
IAEA, a revised analysis, attributed the main cause to the reactor's
design. The simultaneous existence of two such opposing viewpoints as to
the reasons for the Chernobyl accident and the nonstop debate they
engendered were made possible additionally because the primary data
covering the disaster, as registered by the instruments and sensors,
were not completely published in the official sources.
Once again, the human factor had to be considered as a major element
in causing the accident. INSAG notes that both the operating regulations
and staff handled the disabling of the reactor protection easily enough:
witness the length of time for which the ECCS was out of service while
the reactor was operated at half power. INSAG’s view is that it was the
deviation from the test program taken by the operating crew that was
mostly to blame. “Most reprehensibly, unapproved changes in the test
procedure were deliberately made on the spot, although the plant was
known to be in a very different condition from that intended for the
As in the previously released report INSAG-1, close attention is paid
in report INSAG-7 to the inadequate (at the moment of the accident)
“culture of safety” at all levels. Deficiency in the safety culture was
inherent not only at the operational stage but also, and to no lesser
extent, during activities at other stages in the lifetime of nuclear
power plants (including design, engineering, construction, manufacture
and regulation). The poor quality of operating procedures and
instructions, and their conflicting character, put a heavy burden on the
operating crew, including the Chief Engineer.
“The accident can be said to have flowed from a deficient safety
culture, not only at the Chernobyl plant, but throughout the Soviet
design, operating and regulatory organizations for nuclear power that
existed at that time.”
International spread of radioactivity
The nuclear meltdown produced a radioactive cloud that floated
not only over the modern states of Russia, Belarus, Ukraine and Moldova,
but also Turkish Thrace, the Southern coast of the Black Sea, Macedonia,
Serbia, Croatia, Bosnia-Herzegovina, Bulgaria, Greece, Romania,
Lithuania, Estonia, Latvia, Finland, Denmark, Norway, Sweden, Austria,
Hungary, the Czech Republic and the Slovak Republic, The Netherlands,
Belgium, Slovenia, Poland, Switzerland, Germany, Luxembourg, Italy,
Ireland, France (including Corsica) the United Kingdom and the Isle of
The initial evidence that a major exhaust of radioactive material was
affecting other countries came not from Soviet sources, but from Sweden,
where on the morning of the 28 April workers at the Forsmark
Nuclear Power Plant (approximately 1,100 km (680 mi) from the Chernobyl
site) were found to have radioactive particles on their clothes. It was
Sweden's search for the source of radioactivity, after they had
determined there was no leak at the Swedish plant, which at noon of 28
April led to the first hint of a serious nuclear problem in the western
Soviet Union. Hence the evacuation of Pripyat on the 27 April 36 hours
after the initial explosions was silently completed before the disaster
became known outside the Soviet Union. The rise of radiation levels had
at that time already been measured in Finland, but a civil service
strike delayed the response and publication.
Contamination from the Chernobyl accident was scattered irregularly
depending on weather conditions. Reports from Soviet and Western
scientists indicate that Belarus received about 60% of the contamination
that fell on the former Soviet Union. However, the 2006 TORCH report
stated that half of the volatile particles had landed outside Ukraine,
Belarus and Russia. A large area in Russia south of Bryansk was also
contaminated, as were parts of northwestern Ukraine. Studies in
countries around the area say that over one million people could have
been affected by radiation.
Recently published data of a long-term monitoring programme (The
Korma-Report) show a decrease of internal radiation exposure of the
inhabitants of a region in Belarus close to Gomel. Resettlement may even
be possible in prohibited areas provided that people comply with
appropriate dietary rules.
In Western Europe, measures were taken including seemingly arbitrary
regulations pertaining to the legality of importation of certain foods
but not others. In France some officials stated that the Chernobyl
accident had no adverse effects.
Radioactive release (source term)
Like many other releases of radioactivity into the environment,
the Chernobyl release was controlled by the physical and chemical
properties of the radioactive elements in its core. While plutonium is
often perceived as particularly dangerous nuclear fuel by the general
population, its effects are almost eclipsed by those of its fission
products. Particularly dangerous are highly radioactive compounds that
accumulate in the food chain, such as some isotopes of iodine and
Two reports on the release of radioisotopes from the site were made
available, one by the OSTI, and a more detailed report by OECD, both in
1998. At different times after the accident, different isotopes were
responsible for the majority of the external dose. The dose that was
calculated is that received from external gamma irradiation for a person
standing in the open. The dose to a person in a shelter or the internal
dose is harder to estimate.
The release of the radioisotopes from the nuclear fuel was largely
controlled by their boiling points, and the majority of the
radioactivity present in the core was retained in the reactor.
1. All of the noble gases, including krypton and xenon,
contained within the reactor were released immediately into the
atmosphere by the first steam explosion.
2. About 55% of the radioactive iodine in the reactor was
released, as a mixture of vapor, solid particles and as organic iodine
3. Caesium and tellurium were released in aerosol form.
Two sizes of particles were released: small particles of 0.3 to 1.5
micrometers (aerodynamic diameter) and large particles of 10
micrometers. The large particles contained about 80% to 90% of the
released nonvolatile radioisotopes zirconium-95, niobium-95,
lanthanum-140, cerium-144 and the transuranic elements, including
neptunium, plutonium and the minor actinides, embedded in a uranium
Health of plant workers
In the aftermath of the accident, 237 people suffered from acute
radiation sickness, of whom 31 died within the first three
months. Most of these were fire and rescue workers trying to
bring the accident under control, who were not fully aware of how
dangerous the radiation exposure (from the smoke) was. 135,000 people
were evacuated from the area, including 50,000 from Pripyat.
Residual radioactivity in the environment
Rivers, lakes and reservoirs
Satellite image of the reactor and surrounding area.
The Chernobyl nuclear power plant lies next to the Pripyat River which
feeds into the Dnieper River reservoir system, one of the largest
surface water systems in Europe. The radioactive contamination of
aquatic systems therefore became a major issue in the immediate
aftermath of the accident. In the most affected areas of Ukraine, levels
of radioactivity (particularly radioiodine: I-131, radiocaesium: Cs-137
and radiostrontium: Sr-90) in drinking water caused concern during the
weeks and months after the accident. After this initial period however,
radioactivity in rivers and reservoirs was generally below guideline
limits for safe drinking water.
Bio-accumulation of radioactivity in fish resulted in concentrations
(both in western Europe and in the former Soviet Union) that in many
cases were significantly above guideline maximum levels for consumption.
Guideline maximum levels for radiocaesium in fish vary from country to
country but are approximately 1,000 Bq/kg in the European Union. In the
Kiev Reservoir in Ukraine, activity concentrations in fish were several
thousand Bq/kg during the years after the accident. In small "closed"
lakes in Belarus and the Bryansk region of Russia, activity
concentrations in a number of fish species varied from 0.1 to 60 kBq/kg
during the period 1990–92. The contamination of fish caused concern in
the short term (months) for parts of the UK and Germany and in the long
term (years-decades) in the Chernobyl affected areas of Ukraine, Belarus
and Russia as well as in parts of Scandinavia.
Map of radiation levels in 1996 around Chernobyl.
Groundwater was not badly affected by the Chernobyl accident since
radionuclides with short half-lives decayed away a long time before they
could affect groundwater supplies, and longer-lived radionuclides such
as radiocaesium and radiostrontium were adsorbed to surface soils before
they could transfer to groundwaters. Significant transfers of
radionuclides to groundwaters have occurred from waste disposal sites in
the 30 km (19 mi) exclusion zone around Chernobyl. Although there is a
potential for off-site (i.e. out of the 30 km (19 mi) exclusion zone)
transfer of radionuclides from these disposal sites, the IAEA Chernobyl
Report argues that this is not significant in comparison to current
levels of washout of surface-deposited radioactivity.
Flora and fauna
After the disaster, four square kilometres of pine forest in the
immediate vicinity of the reactor turned ginger brown and died, earning
the name of the "Red Forest". Some animals in the worst-hit areas
also died or stopped reproducing. Most domestic animals were evacuated
from the exclusion zone, but horses left on an island in the Pripyat
River 6 km (4 mi) from the power plant died when their thyroid glands
were destroyed by radiation doses of 150–200 Sv. Some cattle on the same
island died and those that survived were stunted because of thyroid
damage. The next generation appeared to be normal.
A robot sent into the reactor itself has returned with samples of
black, melanin-rich fungi that are growing on the reactor's walls.
Chernobyl after the disaster
Following the accident, questions arose about the future of the
plant and its eventual fate. All work on the unfinished reactors 5 and 6
was halted three years later. However, the trouble at the Chernobyl
plant did not end with the disaster in reactor 4. The damaged reactor
was sealed off and 200 metres (660 ft) of concrete was placed between
the disaster site and the operational buildings. The Ukrainian
government continued to let the three remaining reactors operate because
of an energy shortage in the country. A fire broke out in the turbine
building of reactor 2 in 1991; the authorities subsequently declared the
reactor damaged beyond repair and had it taken offline. Reactor 1 was
decommissioned in November 1996 as part of a deal between the Ukrainian
government and international organizations such as the IAEA to end
operations at the plant. On 15 December 2000, then-President Leonid
Kuchma personally turned off Reactor 3 in an official ceremony,
effectively shutting down the entire plant transforming the Chernobyl
plant from energy producer to energy consumer.
Chernobyl's Exclusion Zone
In his book, Disasters: Wasted Lives, Valuable Lessons,
Economist and Crisis Consultant Randall Bell writes after his
research at Chernobyl, "There is a 17-mile (sic) Exclusion Zone around
Chernobyl where officially nobody is allowed to live, but people do.
These "resettlers" are elderly people who lived in the region prior to
the disaster. Today there are approximately 10,000 people between the
ages of 60 and 90 living within the Zone around Chernobyl. Younger
families are allowed to visit, but only for brief periods of time.
"Eventually the land could be utilized for some sort of industrial
purpose that would involve concrete sites," Randall Bell continues. "But
estimates range from 60 – 200 years before this would be allowed.
Farming or any other type of agricultural industry would be dangerous
and completely inappropriate for at least 200 years. It will be at least
two centuries before there is any chance the situation can change within
the 1.5-mile Exclusion Zone. As for the #4 reactor where the meltdown
occurred, we estimate it will be 20,000 years before the real estate
will be fully safe."
Controversy over "Wildlife Haven" claim
The Exclusion Zone around the Chernobyl nuclear power station is
reportedly a haven for wildlife. As humans were evacuated from the area
just over 23 years ago, existing animal populations multiplied and rare
species not seen for centuries have returned or have been reintroduced
e.g. Lynx, Wild Boar, Wolf, Eurasian Brown Bear, European Bison,
Przewalski's horse and Eagle Owl. Birds even nest inside the cracked
concrete sarcophagus shielding in the shattered remains of reactor
number 4. The Exclusion Zone is so lush with wildlife and greenery that
the Ukrainian government designated it a wildlife sanctuary in 2000,
“Chernobyl Special” , at 488.7 km2 it is one of the largest wildlife
sanctuaries in Europe.
According to a 2005 U.N. report, wildlife has returned despite
radiation levels that are presently 10 to 100 times higher than normal
background. Although they were significantly higher soon after the
accident, the levels have fallen due to radioactive decay.
Some researchers claim that by halting the destruction of habitat,
the Chernobyl disaster helped wildlife flourish. Biologist Robert J.
Baker of Texas Tech University was one of the first to report that
Chernobyl had become a wildlife haven and that many rodents he has
studied at Chernobyl since the early 1990s have shown remarkable
tolerance for elevated radiation levels.
However Møller et al. (2005) suggested that reproductive success and
annual survival rates of barn swallows are much lower in the Chernobyl
exclusion zone; 28% of barn swallows inhabiting Chernobyl return each
year, while at a control area at Kanev 250 km to the SE the return rate
is around 40%. A later study by Møller et al. (2007) furthermore claimed
an elevated frequency of 11 categories of subtle physical abnormalities
in barn swallows e.g. bent tail feathers, deformed air sacks, deformed
beaks, isolated albinistic feathers.
However, another researcher criticised these findings and instead
proposed that a lack of human influence in the exclusion zone locally
reduced the swallows' insect prey and radiation levels across the vast
majority of the exclusion are now too low to have an observable negative
effect. But the criticisms raised were responded to in Møller et al.
(2008). It is possible that barn swallows are particularly vulnerable to
elevated levels of ionizing radiation because they are migratory; they
arrive in the exclusion area exhausted and with depleted reserves of
radio-protective antioxidants after an arduous journey.
Several researchers groups have suggested that plants in the area
have adapted to cope with the high radiation levels by e.g. increasing
the activity of DNA cellular repair machinery, hypermethylation etc.
Given the uncertainties, further research is needed to assess the
long-term health effects elevated of ionizing radiation on Chernobyl's
The Chernobyl reactor is now enclosed in a large concrete
sarcophagus which was built quickly to allow continuing operation of the
other reactors at the plant. However, the structure is not strong or
durable. Some major work on the sarcophagus was carried out in 1998 and
1999. Some 200 tons of highly radioactive material remains deep within
it, and this poses an environmental hazard until it is better contained.
A New Safe Confinement structure will be built by the end of 2011,
and then will be put into place on rails. It is to be a metal arch 105
meters (344.4 feet) high and spanning 257 meters (842.9 feet), to cover
both unit 4 and the hastily built 1986 structure. The Chernobyl Shelter
Fund, set up in 1997, has received ˆ810 million from international
donors and projects to cover this project and previous work. It and the
Nuclear Safety Account, also applied to Chernobyl decommissioning, are
managed by the European Bank for Reconstruction and Development (EBRD).
As of 2006, some fuel at units 1 to 3 remained in the reactors, most
of which is in each unit's cooling pond, as well as some material in a
small interim spent fuel storage facility pond (ISF-1).
In 1999 a contract was signed for construction of a radioactive waste
management facility to store 25,000 used fuel assemblies from units 1–3
and other operational wastes, as well as material from decommissioning
units 1–3 (which will be the first RBMK units decommissioned anywhere).
The contract included a processing facility, able to cut the RBMK fuel
assemblies and to put the material in canisters, which were to be filled
with inert gas and welded shut. The canisters were to be transported to
dry storage vaults, where the fuel containers would be enclosed for up
to 100 years. This facility, treating 2500 fuel assemblies per year,
would be the first of its kind for RBMK fuel. However, after a
significant part of the storage structures had been built, technical
deficiencies in the concept emerged, and the contract was terminated in
2007. The interim spent fuel storage facility (ISF-2) will now be
completed by others by mid 2013.
Another contract has been let for a Liquid radioactive Waste
Treatment Plant, to handle some 35,000 cubic meters of low- and
intermediate-level liquid wastes at the site. This will need to be
solidified and eventually buried along with solid wastes on site.
In January 2008 Ukrainian government announced a 4-stage
decommissioning plan which incorporates the above waste activities and
progresses towards a cleared site.
Lava-like Fuel-Containing Materials (FCMs)
According to official estimates, about 95% of the fuel (about 180
tonnes) in the reactor at the time of the accident remains inside the
shelter, with a total radioactivity of nearly 18 million curies (670
PBq). The radioactive material consists of core fragments, dust, and
lava-like "fuel-containing materials" (FCM) that flowed through the
wrecked reactor building before hardening into a ceramic form.
Three different lavas are present in the basement of the reactor
building; black, brown and a porous ceramic. They are silicate glasses
with inclusions of other materials present within them. The porous lava
is brown lava which had dropped into water thus being cooled rapidly.
Degradation of the lava
It is unclear how long the ceramic form will retard the release
of radioactivity. From 1997 to 2002 a series of papers were published
which suggested that the self irradiation of the lava would convert all
1,200 tons into a submicrometre and mobile powder within a few weeks.
But it has been reported that it is likely that the degradation of the
lava is to be a slow and gradual process rather than a sudden rapid
process. The same paper states that the loss of uranium from the wrecked
reactor is only 10 kg (22 lb) per year. This low rate of uranium
leaching suggests that the lava is resisting its environment. The paper
also states that when the shelter is improved, the leaching rate of the
lava will decrease.
Some of the surfaces of the lava flows have started to show new
uranium minerals such as Na4(UO2)(CO3)3 and uranyl carbonate. However
the level of radioactivity is such that during one hundred years the
self irradiation of the lava (2 × 1016 α decays per gram and 2 to 5 ×
105 Gy of β or γ) will fall short of the level of self irradiation which
is required to greatly change the properties of glass (1018 α decays per
gram and 108 to 109 Gy of β or γ). Also the rate of dissolution of the
lava in water is very low (10−7 g-cm−2 day−1) suggesting that the lava
is unlikely to dissolve in water.
Possible consequences of further collapse of the
The Sarcophagus, the concrete block surrounding reactor #4
The protective box which was placed over the wrecked reactor was named
object "Shelter" by the Soviet government, but the media and the public
know it as the sarcophagus.
The present shelter is constructed atop the ruins of the reactor
building. The two "Mammoth Beams" that support the roof of the shelter
are resting partly upon the structurally unsound west wall of the
reactor building that was damaged by the accident. The
western end of the shelter roof was supported by a wall (at a point
designated axis 50). This wall is reinforced concrete, which was cracked
by the accident. In December 2006 the Designed Stabilisation Steel
Structure (DSSS) was extended until 50% of the roof load (about 400
tons) was transferred from the axis-50 wall to the DSSS. The DSSS is a
yellow steel object which has been placed next to the wrecked reactor;
it is 63 metres (207 ft) tall and has a series of cantilevers which
extend through the western buttress wall and is intended to stabilise
the sarcophagus. This was done because if the wall of the reactor
building or the roof of the shelter were to collapse, then large amounts
of radioactive dust and particles would be released directly into the
atmosphere, resulting in a large new release of radioactivity into the
A further threat to the shelter is the concrete slab that formed the
"Upper Biological Shield" (UBS), situated above the reactor prior to the
accident. This concrete slab was thrown upwards by the explosion in the
reactor core and now rests at approximately 15° from vertical. The
position of the upper bioshield is considered inherently unsafe, as only
debris supports it in its nearly upright position. A collapse of the
bioshield would further exacerbate the dust conditions in the shelter,
possibly spreading some quantity of radioactive materials out of the
shelter, and could damage the shelter itself.
Grass and forest fires
It is known that fires can make the radioactivity mobile again.
In particular V.I. Yoschenko et al. reported on the possibility of
increased mobility of caesium, strontium, and plutonium due to grass and
forest fires. As an experiment, fires were set and the levels of the
radioactivity in the air down wind of these fires was measured.
Grass and forest fires have happened inside the contaminated zone,
releasing radioactive fallout into the atmosphere. In 1986 a series of
fires destroyed 23.36 km2 (5,772 acres) of forest, and several other
fires have since burned within the 30 km (19 mi) zone. In early May 1992
a serious fire occurred which affected 5 km2 (1,240 acres) of land
including 2.7 km2 (670 acres) of forest. This resulted in a great
increase in the levels of caesium in airborne dust.
The Chernobyl Shelter Fund was established in 1997 at the Denver
G7 summit to finance the Shelter Implementation Plan (SIP). The plan
calls for transforming the site into an ecologically safe condition
through stabilization of the sarcophagus, followed by construction of a
New Safe Confinement (NSC). While original cost estimate for the SIP was
US$768 million, the 2006 estimate is $1.2 billion. The SIP is being
managed by a consortium of Bechtel, Battelle, and Electricité de France,
and conceptual design for the NSC consists of a movable arch,
constructed away from the shelter to avoid high radiation, to be slid
over the sarcophagus. The NSC is expected to be completed in 2012, and
will be the largest movable structure ever built.
Span: 270 m (886 ft)
Height: 100 m (330 ft)
Length: 150 m (492 ft)
The United Nations Development Programme has launched in 2003 a specific
project called the Chernobyl Recovery and Development Programme (CRDP)
for the recovery of the affected areas. The programme launched its
activities based on the Human Consequences of the Chernobyl Nuclear
Accident report recommendations and has been initiated in February 2002.
The main goal of the CRDP’s activities is supporting the Government of
Ukraine to mitigate long-term social, economic and ecological
consequences of the Chernobyl catastrophe, among others. CRDP works in
the four most Chernobyl-affected areas in Ukraine: Kyivska, Zhytomyrska,
Chernihivska and Rivnenska.
The International Project on the Health Effects of the Chernobyl
Accident (IPEHCA) was created and received $20 million US, mainly from
Japan, in hopes of discovering the main cause of health problems due to
I131 radiation. These funds that were given to IPEHCA were divided
between Ukraine, Belarus, and Russia, the three main affected countries,
for further investigation of health effects. As corruption played an
important role of the former Soviet countries, most of the foreign aid
was given to Russia, and no positive outcome from this money was ever
Assessing the disaster's effects on human health
An international assessment of the health effects of the
Chernobyl accident is contained in a series of reports by the United
Nations Scientific Committee of the Effects of Atomic Radiation (UNSCEAR).
UNSCEAR was set up as a collaboration between various UN bodies,
including the World Health Organisation, after the atomic bomb attacks
on Hiroshima and Nagasaki, to assess the long-term effects of radiation
on human health.
UNSCEAR has conducted 20 years of detailed scientific and
epidemiological research on the effects of the Chernobyl accident. Apart
from the 57 direct deaths in the accident itself, UNSCEAR originally
predicted up to 4,000 additional cancer cases due to the accident,
however the latest UNSCEAR reports insinuate that these estimates were
overstated. In addition, the IAEA states that there has been no increase
in the rate of birth defects or abnormalities, or solid cancers (such as
lung cancer) corroborating UNSCEAR's assessments.
Precisely, UNSCEAR states:
"Among the residents of Belaruss 09, the Russian Federation and
Ukraine there had been, up to 2002, about 4,000 cases of thyroid cancer
reported in children and adolescents who were exposed at the time of the
accident, and more cases are to be expected during the next decades.
Notwithstanding problems associated with screening, many of those
cancers were most likely caused by radiation exposures shortly after the
accident. Apart from this increase, there is no evidence of a major
public health impact attributable to radiation exposure 20 years after
the accident. There is no scientific evidence of increases in overall
cancer incidence or mortality rates or in rates of non-malignant
disorders that could be related to radiation exposure. The risk of
leukaemia in the general population, one of the main concerns owing to
its short latency time, does not appear to be elevated. Although those
most highly exposed individuals are at an increased risk of
radiation-associated effects, the great majority of the population is
not likely to experience serious health consequences as a result of
radiation from the Chernobyl accident. Many other health problems have
been noted in the populations that are not related to radiation
Thyroid cancer is generally treatable. The five year survival rate of
thyroid cancer is 96%, and 92% after 30 years, with proper treatment.
The Chernobyl Forum is a regular meeting of IAEA, other United
Nations organizations (FAO, UN-OCHA, UNDP, UNEP, UNSCEAR, WHO and The
World Bank) and the governments of Belarus, Russia, and Ukraine, which
issues regular scientific assessments of the evidence for health effects
of the Chernobyl accident. The Chernobyl Forum concluded that
twenty-eight emergency workers died from acute radiation syndrome, 15
patients died from thyroid cancer, and it roughly estimated that cancers
deaths caused by Chernobyl may reach a total of about 4000 among the 600
000 people having received the greatest exposures. It also concluded
that a greater risk than the long-term effects of radiation exposure, is
the risk to mental health of exaggerated fears about the effects of
" ... The designation of the affected population as “victims”
rather than “survivors” has led them to perceive themselves as helpless,
weak and lacking control over their future. This, in turn, has led
either to over cautious behavior and exaggerated health concerns, or to
reckless conduct, such as consumption of mushrooms, berries and game
from areas still designated as highly contaminated, overuse of alcohol
and tobacco, and unprotected promiscuous sexual activity."
While it was commented by Fred Mettler that 20 years later:
The population remains largely unsure of what the effects of
radiation actually are and retain a sense of foreboding. A number of
adolescents and young adults who have been exposed to modest or small
amounts of radiation feel that they are somehow fatally flawed and there
is no downside to using illicit drugs or having unprotected sex. To
reverse such attitudes and behaviors will likely take years although
some youth groups have begun programs that have promise.
In addition, disadvantaged children around Chernobyl suffer from
health problems which are not only to do with the Chernobyl accident,
but also with the desperately poor state of post-Soviet health systems.
Another study critical of the Chernobyl Forum report was commissioned
by Greenpeace, which is well known for its anti-nuclear positions. In
its report, Greenpeace alleges that "the most recently published figures
indicate that in Belarus, Russia and Ukraine alone the accident could
have resulted in an estimated 200,000 additional deaths in the period
between 1990 and 2004." However, the Greenpeace report failed to
discriminate between the general increase in cancer rates that followed
the dissolution of the USSR's health system and any separate effects of
the Chernobyl accident.
Lastly, in its report Health Effects of Chernobyl, the German
affiliate of the International Physicians for the Prevention of Nuclear
War (IPPNW) argued that more than 10,000 people are today affected by
thyroid cancer and 50,000 cases are expected in the future. According to
some commentators, both the Greenpeace and IPPNW reports suffer from a
lack of any genuine or original research and failure to understand
epidemiologic data. This said, it is important to bear in mind that many
of the conclusions from reports such as UNSCEAR remain disputed by other
commentators and scientists in the field.
In popular culture
The Chernobyl accident attracted a great deal of interest.
Because of the distrust that many people had in the Soviet authorities
(people both within and outside the USSR) a great deal of debate about
the situation at the site occurred in the first world during the early
days of the event. Due to defective intelligence based upon photographs
taken from space, it was thought that unit number three had also
suffered a dire accident.
A few authors claim that the official reports underestimate the scale
of the Chernobyl tragedy, counting only 30 victims; some estimate the
Chernobyl radioactive fallout as hundreds of times that of the atomic
bomb dropped on Hiroshima, Japan, counting millions of exposed.
In general the public knew little about radioactivity and radiation
and as a result their degree of fear was increased. It was the case that
many professionals (such as the spokesman from the UK NRPB) were
mistrusted by journalists, who in turn encouraged the public to mistrust
It was noted that different governments tried to set contamination
level limits which were stricter than the next country.
In Italy, the fear of nuclear accidents was dramatically increased by
the Chernobyl accident: this was reflected in the outcome of the 1987
referendum about the construction of new nuclear plants in Italy. As a
result of that referendum, Italy began phasing out its nuclear power
plants in 1988.
Commemoration of the disaster
The Front Veranda (1986), a lithograph by Susan Dorothea White in
the National Gallery of Australia shows awareness of the event
worldwide. Heavy Water: A film for Chernobyl was released by Seventh Art
in 2006 to commemorate the disaster through poetry and first-hand
accounts. The film secured the Cinequest Award as well as the Rhode
Island 'best score' award along with a screening at Tate Modern.
This exhibit presents the stories of 20 people who have each been
affected by the disaster, and each person's account is written on a
panel. The 20 individuals whose stories are related in the exhibition
are from Belarus, France, Latvia, Russia, Sweden, Ukraine, and the
Developed by Danish photo-journalist Mads Eskesen, the exhibition is
prepared in multiple languages including German, English, Danish, Dutch,
Russian and Ukrainian.
In Kiev, Ukraine, the exhibition was launched at the "Chernobyl 20
Remembrance for the Future" conference on 23 April 2006. It was then
exhibited during 2006 in Australia, Denmark, the Netherlands,
Switzerland, Ukraine, the United Kingdom, and the United States.