The Chernobyl nuclear disaster of 1986 was the worst nuclear power plant accident in history. On April 26, 1986, a failed safety test at the Chernobyl nuclear power plant in Ukraine caused a massive explosion that released radiation 100 times more than the atomic bombings of Hiroshima and Nagasaki. Over 30 emergency workers died immediately from acute radiation sickness. Over the following decades, thousands more died from long-term health effects like cancer. The radiation fallout contaminated large areas of Ukraine, Belarus, Russia and beyond, forcing over 336,000 people to be permanently evacuated from the most affected areas near the plant. The disaster highlighted the risks of nuclear power and led to increased safety standards worldwide.

1. Chernobyl Disaster
Dr Nik Nor Ronaidi bin Nik Mahdi

2. Chernobyl Disaster: The Worst
Nuclear Disaster in History
100 times more radioactivity than
Hiroshima

3. Where is Chernobyl?
-In Northern Ukraine
-10 miles away
from Belarus
-80 miles North of Kiev
http://students.vassar.edu/mezegen/Eastern%20Europe%20Map.gif
http://studiohousebooks.co.uk/chernobyl/Chernobyl/chernobyl.html

4. The Chernobyl Nuclear Power Plant
• Located 11 miles north of the city of Chernobyl
• Plant consisted of 4 reactors
• Produced 10% of Ukraine’s electricity
• Construction began in the 1970’s
• Reactor #4 was completed in 1983
• At the time of
the accident,
reactors #5
and #6 were
in progress.
http://www.rotten.com/library/history/nuclear-incidents/chernobyl

5. Background
• Type: Reaktor Bolshoy Moshehnosty Kipyashiy
(RBMK)
• RBMK, a Russian acronym translated
roughly means “reactor (of) high power
(of the) channel (type)”
• reactor cooled by water and moderated by
graphite

6. Reactor Schematic

7. Reactor Plant Scenario
1. As the reaction occurs, the uranium fuel becomes
hot
2. The water pumped through the core in pressure
tubes removes the heat from the fuel
3. The water is then boiled into steam
4. The steam turns the turbines
5. The water is
then cooled
6. Then the process
repeats

8. What happened?
Saturday, April 26, 1986:
-Reactor #4 was undergoing a test to test
the backup power supply in case of a
power loss.
-The power fell too low, allowing the
concentration of xenon-135 to rise.
-The workers continued the test, and in
order to control the rising levels of
xenon-135, the control rods were pulled
out.
http://www.ukrainianweb.com/images/chernobyl/chernobyl_reactor.jpg

9. What happened? cont’d
-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 an explosion,
which blew a hole in the roof. A graphite fire also resulted from
the explosion.
-To save money, the reactor was constructed with only partial
containment, which allowed the radiation to escape.
This dispersed large amount of radioactive particulate and
gaseous debris containing cesium-137 and strontium-90 which
are highly radioactive reactor waste product.

10. Reasons for the accident
– Workers lack of knowledge of reactor
physics and engineering, as well as
lack of experience and training
• Delay
• The night shift was not prepared to
carry out the experiment
• But it was still carried out
• The operators seem to have been
unaware of the xenon poisoning
– Insufficient communication
between the safety officers and
the operators in charge of the
experiment
– Disabled all safety systems
– Poor quality (typical Soviet
craftsmanship)
• Rushed design
• A lot of corners cut to meet deadline
– Bonus for meeting deadline

11. The Reactor After the Explosion
After the
explosion, most of the
plant is still standing. Some
might think from this
picture that the disaster
wasn’t all that bad, but
what makes the Chernobyl
disaster the worst in
history is the sheer volume
of radioactive materials
that where spewed across
the European continent.

12. Summary of Facts
• April 26, 1986:
– Chernobyl nuclear power
plant
• Operator errors cause a reactor
explosion
• Explosion releases 190 tons of
radioactive gasses into the
atmosphere
• Fire starts that lasts 10 days
• People:
– 7 million lived in
contaminated areas; 3 million
were children
• Wind:
– Carries radiation far distances

13. Chernobyl Catastrophe Victims
comprise four main groups
• Group 1: persons involved in the clean-up
operations at the Chernobyl Nuclear Plant
(liquidators).
• Group 2: Persons evacuated from the exclusion
zone in 1986 (evacuees)
• Group 3: Persons resident in the territories
monitored (relocation zone) or resident there
immediately after the accident (residents)
• Group 4: Children born to parents in Groups 1-3
(offspring).

14. Immediate Impact
- 231 people were
hospitalized immediately
due to acute radiation
sickness.
- 31 of them eventually
died. Most of these people
were workers in the plant
or local firefighters.
http://www.cmc.ec.gc.ca/~arqidor/ctbto/ctbt3.html

15. The Clean Up
• “Liquidators”
– These were firemen who helped
put out the fires and helped clean
up the radiation
– Most did not realize the dangers
of radiation.
– Many later died from
radiation, because they didn’t
wear protection.
– An estimated 8,000-20,000 to
date have died (20% from
suicide)
• Robots
– United States supplied
– Specifically designed to enter
reactor core and help build the
sarcophagus
http://www.chernobyl-international.com/aboutchernobyl/fateoftheliquidators.asp
http://er1.org/docs/photos/Disaster/Chernobyl%2002%20robotic%20inspector.jpg

16. Clean Up
Approximately
300,000 to 600,000
liquidators were
involved in the
cleanup of the 30
km evacuation zone
around the plant in
the years following
the meltdown.
http://library.thinkquest.org/3426/data/emergency/cleanup.efforts.html

17. Evacuation
-Following the accident hundreds of
thousands of people had to be
evacuated and between 1990 and 1995
an additional 210,000 people were
resettled.
People evacuated:
-May 2-3 (1 week later)
10 km area (45,000 people)
-May 4
30 km area (116,000 people)
-50,000 people from Pripyat, Ukraine were evacuated 2 days after
the accident.
http://library.thinkquest.org/3426/data/emergency/evacuation.html

18. Long term Impact
• International spread of radioactivity
– detected over all of Europe except for the Iberian
Peninsula
– The nuclear meltdown provoked a radioactive cloud
which floated over Russia, Belarus, Ukraine and
Moldova, but also the European part of the Republic of
Macedonia, Croatia, Turkey, Bulgaria, Greece, Romania,
Lithuania, Latvia, Finland, Denmark, Norway, Sweden,
Austria, Hungary, the Czech Republic and the Slovak
Republic, Slovenia, Poland, Switzerland, Germany, Italy,
Ireland, France and the United Kingdom (UK).

19. Long term Impact (cont)
• Radioactive release
– Highly radioactive compounds that accumulate in the
food chain, such as some isotopes of iodine and
strontium are particularly dangerous.
– All of the noble gases, including krypton and xenon,
contained within the reactor were released immediately
into the atmosphere by the first steam explosion.
– About 55% of the radioactive iodine in the reactor was
released, as a mixture of vapor, solid particles and as
organic iodine compounds.
– Plutonium’s half life is 24,400 years.

20. Cycle of Radioactive Materials

21. Long term Impact (cont)
• Residual radioactivity in the environment
– Rivers, lakes and reservoirs
• 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.
• Bio-accumulation of radioactivity in fish were significantly
above guideline maximum levels for consumption
– Groundwater
• Groundwater was not badly affected 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

22. Long term Impact (cont)
– Fauna and vegetation
• pine forest in the 10km2 surrounding 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.

23. Long term Impact (cont)
Socio Economical impact
• The affected territories are mostly rural.
• The main source of income before the accident
was agriculture
• The agricultural sector was the area of the
economy worst hit by the effects of the accident.
• A total of 784 320 hectares of agricultural land
was removed from service in the three countries,
and timber production was halted for a total of
694 200 hectares of forest.

24. Long term Impact (cont)
Socio Economical impact
• Restrictions on agricultural production crippled
the market for foodstuffs and other products from
the affected areas.
• Even where remediation measures have made
farming safe, the stigma of Chernobyl has caused
some consumers to reject products from affected
areas.

25. Long term Impact (cont)
• Health Effects
– Thyroid cancers
• A large increase in the incidence of thyroid cancer has
occurred among young children and adolescents at
the time of the accident and lived in the most
contaminated areas of Belarus, the Russian
Federation and Ukraine.
• This was due to the released of high levels of
radioactive iodine
• Radioactive iodine was deposited in pastures eaten by
cows who then concentrated it in their milk which
was subsequently drunk by children

26. Long term Impact (cont)
• Health effects
– Leukaemia and non-thyroid solid cancer
• Ionizing radiation is a known cause of certain types of
leukaemia (a malignancy of blood cells).
• An elevated risk of leukaemia was first found among the
survivors of the atomic bombings in Japan some two to five
years after exposure.
• Recent investigations suggest a doubling of the incidence of
leukaemia among the most highly exposed Chernobyl
liquidators.
• Reports indicate a small increase in the incidence of pre-
menopausal breast cancer in the most contaminated areas,
which appear to be related to radiation dose.
• Need confirmation in well-designed epidemiological studies.

27. Long term Impact (cont)
• Health effects
– Cataracts
• The lens of the eye is very sensitive to ionizing radiation and
cataracts are known to result from effective doses of about 2 Sv.
• The production of cataracts is directly related to the dose. The higher
the dose the faster the cataract appears.
• Chernobyl cataract studies suggest that radiation opacities may
occur from doses as low as 250 mSv.
– Cardiovascular disease
• A large Russian study among emergency workers has suggested an
increased risk of death from cardiovascular disease in highly exposed
individuals.
• While this finding needs further study with longer follow-up times, it
is consistent with other studies, for example, on radiotherapy
patients, who received considerably higher doses to the heart.

28. Long term Impact (cont)
• Health effects
– Mental health and psychological effects
• High levels of stress, anxiety and medically unexplained
physical symptoms continue to be reported among those
affected by the accident.
– Reproductive and hereditary effects and children's
health
• Birth defects, infertility

29. Economic cost
• The scale of the burden is clear from the wide range of
costs incurred, both direct and indirect:
– Direct damage caused by the accident;
– Expenditures related to:
• Actions to seal off the reactor and mitigate the consequences in the
exclusion zone;
• Resettlement of people and construction of new housing and
infrastructure to accommodate them;
• Social protection and health care provided to the affected population;
• Research on environment, health and production of clean food;
• Radiation monitoring of the environment; and
• Radioecological improvement of settlements and disposal of radioactive
waste.
– Indirect losses relating to the opportunity cost of removing
agricultural land and forests from use and the closure of
agricultural and industrial facilities; and
– Opportunity costs, including the additional costs of energy
resulting from the loss of power from the Chernobyl and the
cancellation of Belarus’s nuclear power programme.

30. Economic cost (cont)
• Coping with the impact of the disaster has placed a
huge burden on national budgets.
• In Ukraine, 5–7 % of government spending each
year is still devoted to Chernobyl-related benefits
and programmes.
• In Belarus, government spending on Chernobyl
amounted to 22.3% of the national budget in 1991,
declining gradually to 6.1% in 2002. Total spending
by Belarus on Chernobyl between 1991 and 2003
was more than USD 13 billion.

31. What has been done to reduce exposure
in contaminated areas?
• The Soviet and Commonwealth of Independent States
(CIS) authorities introduced a wide range of short and
long term environmental countermeasures to mitigate
the accidents negative consequences:
– Decontamination of settlements in contaminated regions
– Exclusion of contaminated pasture grasses from animal diets
and rejection of milk based on radiation monitoring data.
– Feeding animals with “clean” fodder
– Application of Cs-binders, such as Prussian blue, to prevent
contamination of milk and meat

32. What has been done to reduce exposure
in contaminated areas?
• Restrictions:
– Restrictions on public and forest worker access as a
countermeasure against external exposure;
– Restricted harvesting of food products such as game, berries and
mushrooms by the public that contributed to reduction of internal
doses. In the CIS countries mushrooms are a staple of many diets
and, therefore, this restriction has been particularly important;
– Restricted collection of firewood by the public to prevent
exposures in the home and garden when the wood is burned and
the ash is disposed of or used as a fertilizer; and
– Alteration of hunting practices aiming to avoid consumption of
meat with high seasonal levels of radiocaesium.
– restriction of drinking water and changing to alternative supplies.
– Restrictions on consumption of freshwater fish

33. Lessons learned from Chernobyl
• The scale of the material and the financial losses in mitigating
the consequences of the Chernobyl accident provide
compelling evidence of the extremely high price of errors and
shortcomings when ensuring the safety of nuclear power
plants and of the need for strict compliance with international
safety requirements during their design, construction and
operation.
• The cost of ensuring the safety of nuclear facilities is
significantly lower than that of dealing with accident
consequences. Large-scale man-made accidents cause great
social and economic damage to countries located in their area
of influence. Hundreds of billions of US dollars’ worth of
direct and indirect damages have been reported by
Belarus, Russia and Ukraine as a result of the Chernobyl
nuclear power plant accident over the past 20 years.

34. Lessons learned from Chernobyl
• The accident has shown the importance of strict
compliance with the basic and technical safety
principles for nuclear power plants, of continuous
safety analysis of operating nuclear power plants
and of their early upgrading in order to eliminate
deviations, of active study and the introduction of
leading world experience, and of taking thorough
account of the human factor.
• The accident has demonstrated the need to
establish and support a high-level national
emergency response system in case of man-made
accidents.

35. THaNK YoU

36. Content
• Chronology - The site and accident sequence
• The release and nature of radionuclide
• Estimation of exposure
• Human health effects – clinical manifestation
and acute vs chronic effects
• Agricultural and environmental impacts
• Potential residual risks
• Lessons learnt
• Studies done related to Chernobyl disaster