1) In 1986, a nuclear accident occurred at the Chernobyl Nuclear Power Plant in Ukraine causing multiple explosions that released significant radioactive material into the atmosphere. 2) Over 100,000 people were evacuated from the surrounding area in the initial aftermath. 3) 57 direct deaths are attributed to the accident, including 28 from acute radiation syndrome. Thousands of additional cancer cases, especially thyroid cancer, have been diagnosed since from long-term radiation exposure.

1. CHERNOBYL
1986

2. By:
Clavita A Rodrigues
Clavita.rods@gmail.com

3. Nuclear Power Plant
● Nuclear reactors are the heart of a nuclear power plant.
● With more than 440 commercial reactors worldwide, nuclear power
continues to be one of the largest sources of reliable carbon-
free electricity available.
● The main job of a reactor is to house and control nuclear fission—a
process where atoms split and release energy.

4. A nuclear reactor consists of three crucial components:
1. fuel elements,
2. moderators and
3. control rods.
1. Fuel elements
● shape - thin rods of about 1 cm in diameter
● contain fissionable nuclei like uranium-235 or uranium-238.
● This region where these fuel elements are placed is called the
reactor core.
● These fuel elements are normally immersed in water which acts
both as a coolant and moderator.

5. 2. Moderator
● capability to slow down or in other words moderate the speeds
of these high-energy neutrons.
● used for a chain reaction to trigger multiple fission reactions of
other uranium-235 nuclei.
● commonly ordinary or heavy water is used as a moderator
because of the deuterons present in them.
● Graphite is also used as moderator
3. Control rods.
● to absorb any excess or spare neutron in the moderator in order
to prevent any further fission reactions.
● to ensure the nuclear reaction takes place at the right speed,
reactors have systems that accelerate, slow or shut down the
nuclear reaction, and the heat it produces.
● typically are made out of neutron-absorbing materials such as
silver or boron or cadmium

6. Nuclear Power Plant

7. Saturday, April 26, 1986

8. Where is Chernobyl?
Northern Ukraine
The Chernobyl nuclear facility is located in Ukraine about 20 km south of the
border with Belarus.

9. The Chernobyl Nuclear Power Plant
⬜ Located 17Km’s north of the city of Chernobyl
⬜ Plant consisted of 4 reactors (units 1,2,3 & 4)
⬜ Produced 10% of Ukraine’s electricity
⬜ Construction began in the 1970’s
⬜ Reactor No.4 was completed in 1983

10. What Happened?
-The Chernobyl reactor is of the type Soviet
RBMK, which is an abbreviation in Russian
Reactor BolshoMoshchnosty Kanalny,
meaning “high-power channel reactor.”
-It is a pressurized water reactor using light
water as a coolant and graphite as a
moderator.
-The accident occurred in the very early
morning (1:24 am) of 26 April 1986 when
Reactor No.4 was undergoing a test of the
backup power supply in case of a power
loss.
-The power fell too low, allowing the
concentration of xenon-135 to rise.

11. What Happened?
-The workers continued the test, and in order to control the rising levels
of xenon-135 (produced in nuclear reactions), the control rods were
pulled out.
-The experiment involved shutting down the coolant pumps, which caused
the coolant to rapidly heat up and boil.
-Pockets of steam formed in the coolant lines. When the coolant
expanded in this particular design, the power level went up.
-All control rods were ordered to be inserted. As the rods were inserted,
they became deformed and stuck. The reaction could not be stopped.
-The rods melted and the steam pressure caused a series of explosions,
which blew a hole in the roof. A fire also resulted from the explosion.
-The hot fuel particles reacted with water and caused a steam explosion,
which lifted the 1,000-metric-ton cover off the top of the reactor,
rupturing the rest of the 1,660 pressure tubes, causing a second
explosion and exposing the reactor core to the environment.

12. ● The core debris dispersed by the explosion
started multiple (more than 30) fires on the
roofs of the reactor building and the machine
hall, which were covered with highly flammable
tar.
● A first group of 14 firemen arrived on the
scene of the accident at 1.28 a.m.
Reinforcements were brought in until about 4
a.m., when 250 firemen were available and 69
firemen participated in fire control activities.
● These activities were carried out at up to 70 m
above the ground under harsh conditions of high
radiation levels and dense smoke.
● By about 4.50 a.m., most of the fires had been
extinguished. These actions caused the deaths
of five firefighters.

13. ● Approximately 20 h after the explosion, at 9.41 p.m., a large fire
started as the material in the reactor became hot enough to
ignite combustible gases released from the disrupted core, e.g.
hydrogen from zirconium-water reactions and carbon
monoxide from the reaction of hot graphite with steam.
● The large fire burned for 10 days.
● The fire made noise and burned with a large flame that reached
at least 50 m above the top of the destroyed reactor hall.

14. Why did the accident occur?
● because of the unstable state of the reactor before the accident due
both to basic engineering deficiencies and to faulty actions of
the operators (e.g., switching off the emergency safety systems of
the reactor)
● To save money, the reactor was constructed with only partial
containment, which allowed the radiation to escape. 13%-30% of the
material escaped.
● Other actions resulted in a rapid increase in the power level of
the reactor. This generated a shock wave in the cooling water,
which led to the failure of most of the lower transition joints. As a
result, the pressurized cooling water in the primary system was
released, and it immediately flashed into steam.
● The safety systems had been switched off, and the reactor was
being operated under improper, unstable conditions,
● an uncontrollable power surge to occured resulting in successive
steam explosions that severely damaged the reactor building and
completely destroyed the reactor.

15. ● The first measures taken to control the fire and the radionuclide releases
consisted of 1,800 helicopters repeatedly dumping neutron-
absorbing compounds and fire-control materials into the crater
formed by the destruction of the reactor
● later the reactor structure was cooled with liquid nitrogen using pipelines
originating from another reactor unit.
● The total amount of materials dumped on the reactor was approximately
5,000 t, including about 40 t of boron (B) compounds, 2,400 t of lead
(Pb), 1,800 t of sand (SiO2) and clay, and 600 t of dolomite
(CaMg(CO3)2), as well as sodium phosphate and polymer liquids.
● About 150 t of materials were dumped on 27 April, followed by 300t on 28
April, 750 t on 29 April, 1,500 t on 30 April, 1,900 t on 1 May, and 400 t on
2 May.
Measures taken

16. ● During the first flights, the helicopters remained
stationary over the reactor while dumping the materials.
● the dose rates received by the helicopter pilots were too
high, it was decided that the materials should be
dumped while the helicopters travelled over the reactor.
● This procedure, which had a poor accuracy, caused
additional destruction of the standing structures and
spread the contamination.
● In fact, much of the material delivered by the helicopters
was dumped on the roof of the reactor hall, where a
glowing fire was observed.
● because the reactor core was partially obstructed by
the upper biological shield, broken piping, and other
debris, and rising smoke made it difficult to see and
identify the core location.

17. Evacuation
Helicopter pilots dropped over
5000t of material

18. Evacuation
• The accident brought about the evacuation of about 116,000 people
from areas surrounding the reactor during 1986, and the relocation, after
1986, of about 220,000 people from what were at that time three
constituent republics of the Soviet Union: Belorussia, the Russian Soviet
Federated Socialist Republic (RSFSR) and Ukraine
• (these republics will hereinafter be called by their present-day country
names: Belarus, the Russian Federation and Ukraine).
• In addition, about 240,000 workers (“liquidators”) were called upon in
1986 and 1987 to take part in major mitigation activities at the reactor and
within the 30-km zone surrounding the reactor; residual clean-up activities
continued until 1990.
• Altogether, about 600,000 persons received the special status of
“liquidator”
*liquidator: an official person or organization that is given the job of closing a company, by selling its
assets so that its debts can be paid

19. Clean Up
Approximately 300,000 to
600,000 people were involved in
the cleanup of the 30 km
evacuation zone around the
plant in the years following the
meltdown.

20. West and Northwest winds
carried radiation
NW winds from the Black Sea carried the radiation for km’s
in the following days. Scandinavian detectors picked up
on the abundance of radiation, but the Soviet
government denied any knowledge of the event.

21. MAP TO SHOW INITIAL EXTENT OF
RADIOACTIVE CLOUD (Day 1-4)

23. How were humans exposed to radiation?

24. Effects of Radiation
○ If the human body absorbs a dose of a few of grays external
radiation, it may cause acute radiation syndrome (ARS).
○ Workers who were near the reactor at the time of the accident and
shortly afterwards received high doses of external gamma radiation,
which were fatal to some of them.
○ Belarusian doctors identify the following effects from the Chernobyl
disaster on the health of their people:
○ 100% increase in the incidence of cancer and leukemia
○ 250% increase in congenital birth deformities
○ “Chernobyl AIDS”--the term doctors are using to describe
illnesses associated with the damage done to the immune system

25. Effects of Radiation

27. Deaths & Impact
• The initial steam explosion resulted in the deaths of two workers.
• On the day of the accident, there were 600 workers onsite. 134 plant
staff and emergency workers suffered acute radiation syndrome
(ARS) due to high doses of radiation; of those, 28 of them later died
from ARS.
• The total number of cases of thyroid cancer registered in the 1991–
2015 period among those under 18 years of age in 1986 (for the
whole of Belarus and Ukraine, and for the four most-contaminated
oblasts of the Russian Federation), approached 20,000.
• About 5,000 thyroid cancer cases were attributable to radioactive
iodine (iodine-131) exposure to those who were children or
adolescents at the time of the accident.
• The remaining 15,000 cases were cataracts, tumours, leukaemia, hair
loss, heart failures, decrease in white blood cells etc
• An estimated 8,000-20,000 to date have died (20% from
suicide)

28. ❏ The childhood thyroid gland is,
besides red bone marrow,
premenopausal female breast,
and lung, one of the most
radiosensitive organs in the body
❏ Among survivors, the most
pronounced risk of thyroid
cancer was found among those
exposed before the age of 10
years, and the highest risk was
seen 15-29 years after exposure
and was still increased 40 years
after exposure

29. • After the accident, the crippled Chernobyl 4 reactor was originally
enclosed in a concrete structure that was growing weaker over
time.
• As of November 2018, it is now encased in an enormous steel
and concrete sarcophagus which is expected to last 100 years
or more.
• problems have later arisen from the fact that the Shelter had to
be erected quickly and under very difficult conditions, partly
because the construction personnel were exposed to severe
radiation levels.
Long-term effects and responses - Containment

30. Belarus after Chernobyl
Abandoned city in
southern Belarus

31. Environmental Consequences
Belarusian Landscape
Pripyat River in Belarus
Abandoned road in Belarus

32. Contaminated Agricultural areas
• After the accident, the deposition of radioactive iodine
contaminated agricultural plants, grazing animals, and thus
the milk produced in parts of Belarus, Russia, Ukraine and some
other parts of Europe.
• Children who had consumed milk from cows that had eaten
contaminated grass were particularly affected, and many of them
went on to develop thyroid cancer.
• After this early phase of deposition, an increasingly important
concern was plant contamination through absorption of
radioactive materials, such as caesium and strontium, from the soil
through their roots.
• For decades to come, most of the radioactive materials that
people take in through food and drink in the affected areas will be
caesium-137 present in milk, meat, and crops

33. Contaminated water bodies
• Radioactive materials from Chernobyl deposited on rivers,
lakes and some water reservoirs both in areas close to the
reactor site and in other parts of Europe.
• Fish absorbed radioactive iodine very quickly but the levels
decreased rapidly due to radioactive decay .
• Bioaccumulation of radioactive caesium along the aquatic
food chain resulted in high concentrations in fish in some lakes
as far away as Scandinavia and Germany.
• Aquatic bodies are still being contaminated by runoff of long
lived caesium-137 and strontium-90 released from
contaminated soils.
• in some “closed” lakes with no outflowing streams in Belarus,
Russia and Ukraine both water and fish will remain
contaminated with caesium-137 for decades to come.

34. •70% of total
fallout fell
on Belarus
•20% of
Belarus land
area was
evacuated
•130,000
Belarusians
evacuated
•2.5 million
Belarusians
affected
Impact on Belarus

35. The Land
⬜ 25% of the country's
farmland and forest
contaminated at a
dangerous level
⬜ 10% of the land is
unusable
⬜ 1% of the entire
land was
uncontaminated
⬜ Forests ruined
⬜ Many animals are
dying as well from
the radiation

36. ⬜ Plutonium’s half life is
24,400 years.
⬜ The 30-km radius has
been expanded into a
70-km radius, covering
a portion of southern
Belarus.
⬜ Forest/brush fires have
spread the radiation
through the air.

37. ⬜ Food & Water
◼Milk—Farmers have to watch
the radiation level in milk.
◼Fish—Cannot be eaten, as
water absorbs radiation and
fats concentrate it
The Land
◼Radioactive Floods
every spring

38. Physiological Impact
➢ The Chernobyl-exposed populations following a traumatic
accident or event: stress, depression, anxiety (including post-
traumatic stress symptoms), medically unexplained physical
symptoms, and subjective poor health.
➢ Many people were traumatized by the rapid relocation and the
breakdown in social contacts, and in the absence of reliable
information have experienced fear and anxiety about what
health effects might result.
➢ In addition, individuals in the affected population have come
to be known as "Chernobyl victims" rather than "survivors",
which encouraged them to perceive themselves as helpless,
weak and lacking control over their future, thus to take on the
role of invalid

39. Economic cost of the Chernobyl accident
○ direct damage caused by the accident.
○ expenditures related for instance to sealing off the reactor,
treating the Exclusion Zone and other affected areas,
resettling people, providing health care and social protection
for those affected, monitoring radiation, and disposing of
radioactive waste.
○ indirect costs linked to restrictions in the use of agricultural
land and forests, and to the closure of industrial and
agricultural facilities.
○ increased energy costs resulting from the closure of the
Chernobyl plant and the cancellation of Belarus’s nuclear
power programme.
The level of government spending linked to Chernobyl is a huge
burden on national budgets and is unsustainable,

40. Chernobyl Today
•The plant has been shut down by
Ukraine.
(Dec. 2000)
•The cement sarcophagus is falling
apart, due to the quick emergency
construction of it.
•The UN estimates that up to 9
million people have been affected
directly or indirectly by the fallout.
•The full consequences will not be
seen for at least another 50 years.

41. Chernobyl Today
•Hundreds of abandoned towns
•Land still very contaminated, cannot be
used for the next 20,000 years
•Most of budget goes towards medical
facilities
•Over the next 30 years, Chernobyl will
have spent a total of $235 billion on
dealing with radiation.
•Many areas will forever be radioactive.
•Radiation is still a problem, specially in
children

42. Living in the contaminated zone today…
• People must change their clothes twice a day, and may
not walk in the woods for more than two hours a month.
• Radiation level charts are printed in the newspapers and
dictate decisions such as whether children can be allowed
out to play.
• People are told to wash food at least five times in clean
water, but nobody is told where this clean water is to be
found.
• Cattle are not supposed to graze in areas where the grass
is less than 10cm high so their mouths will not touch the
earth.
• Most people find it impossible to follow these nearly
impossible instructions, so they simply give up trying.
• There are also housing shortages in Belarus and the rest
of the ex-Soviet Union. This is a problem because people
have a hard time moving out of the contaminated zone,
since there are no other places to live.

43. Signs warn against entering areas around Chernobyl
affected by high levels of radiation.

44. Measures taken
• contaminated regions of the USSR were cleaned up at great
cost.
• However, this produced a disposal problem because it created a
considerable amount of low-level radioactive waste.
• to avoid human exposure to radioactive iodine through milk, use of
"clean" fodder for cattle and rejection of contaminated milk.
• the land used for fodder crops was treated and animals were given
not only clean fodder but also chemicals that "trap" the radioactive
caesium.
• These effective but costly countermeasures have been applied less
often since the middle of the 1990s leading to increased levels of
radioactive caesium in agricultural products.

45. • Restrictions have been applied to many
forests in terms of access, hunting, and
harvesting of forest products such as
berries, mushrooms, and firewood.
• Many attempts were made to protect water
systems from radioactive materials
leaching from contaminated soils, but they
were generally ineffective and expensive.
• The most effective countermeasure was
switching to uncontaminated drinking
water supplies.
• Restrictions on consumption of freshwater
fish were only followed in some areas.

46. The Chernobyl nuclear power plant complex. Today, the destroyed
4th reactor is sheltered by a protective shield.

47. Solutions
● engineering of the plant with extensive safety features to
prevent large scale accidents
● reactors enclosed in a shield of thick concrete or lead walls
so that gamma rays don’t penetrate out
● use of water as moderator instead of graphite
● recruiting qualified employees
● extensive emergency preparedness planning, of course
accidents do happen.
● as of today there is no concept of safe nuclear energy
● alert and notification. Do not conceal the accident from
higher authorities and local population. (evacuation started
late)

48. Valery Legasov
Valery Alekseyevich Legasov was a Soviet and Russian
inorganic chemist and a member of the Academy of
Sciences of the Soviet Union
Many people credit him as the sole rational, intelligent figure involved in the problem’s
solution, as it was Legasov who was responsible for launching the immediate remedies
to Chernobyl’s long-term effects.
Valery Legasov would fly over the Chernobyl Nuclear Power Plant 5-6 times a day. An on-
board Geiger-Muller Counter (dosimeter) with a maximum scale of 500 roentgens per
hour went off the scale
He led the commission that investigated the catastrophe.
Valery was a proponent of transparency between the
commission’s findings and the public in spite of the Soviet
government’s efforts to downplay the Chernobyl disaster.
Although it was allowed to spend a maximum of two weeks at the site, the scientist spent
4 months (!) There, and was exposed to 100 REM (Roentgen Equivalent Man) – four times
the allowed maximum of 25 REM.
The Hero!

49. Thank You!