The Chernobyl nuclear disaster occurred in 1986 when a safety test caused an explosion at the Chernobyl Nuclear Power Plant in Ukraine. This caused radioactive material to spread over much of Europe. Over 100,000 people were evacuated and many suffered long-term health effects like increased cancer rates. The disaster highlighted flaws in the Soviet nuclear reactor design and had enormous economic and social costs for the affected regions.

1. CHERNOBYL
DISASTER,1986
PRESENTED BY
HIRAK JYOTI KUMAR(M .Sc 4th sem,Radiological Physics)
AKHILESH KUMAR SAHU(M.Sc 4th sem,Radiological
Physics)

2. CONTENTS
 INTRODUCTION
 HISTORY
 WORKING OF NUCLEAR REACTOR
 CAUSES
 RADIOACTIVITY RELEASE
 EFFECTS AND OUTCOMES
 RECOMMENDATIONS TO THE GOVTS.
 LESSONS LEARNED

3. INTRODUCTION
 Where is Chernobyl
situated?
 Chernobyl is situated
about 130km north of
Kiev, Ukraine, and
about 20 km south of
the border with
Belarus.

4. HISTORY
 After 2nd world war, the soviet union invested a
lot of money in nuclear power plants. It built
many nuclear power plants, one of which was
the Chernobyl nuclear power plant.
 The official name of this plant is VLADIMIR
LENIN NUCLEAR POWER PLANT. It was
built in the early 1970s
 This plant was among one of the most
advanced nuclear power plants in the soviet
union.

5.  There were four nuclear reactors of RBMK
1000 design.
 Reaktor Bolshoy Moshehnosty
Kipyashiy(RBMK) is a Russian acronym
translated roughly means “reactors of high
power channel type”.
 The operations of the first 2 reactors had begun
in 1977,the third in 1981,and the fourth in 1983.
 The purpose of the power plants was to
generate electricity. In this case, each reactor
could produce 1000 MW electricity.

7. WORKING OF NUCLEAR
REACTOR
 Nuclear reactor is a device in which a nuclear chain
reaction is initiated, maintained and controlled. It
works on the principle of controlled chain reaction
and provides energy at a constant rate
 A nuclear reactor is driven by the splitting of atoms
a process called nuclear fission in which a heavy
nucleus when excited splits into two smaller nuclei
of nearly comparable masses.

8.  In a nuclear fission, the sum of the masses of the
final product is less than the sum of the masses of
the reactant components. The difference in
masses, called mass defect, is converted into
energy according to Einstein’s mass energy
relationship.

10. Main component of nuclear
reactor :
1) Nuclear fuel--material that can be fissioned
by neutrons Isotopes like U-235.
2) Moderator--To slow down the fast neutrons
3) Control rods--To start, stop or control the
chain reaction.
4) Coolant--It is the material used to cool the
reactor core and is capable of carrying
away large amount of heat produced in the
fission process.
5) Shielding--It is used to isolate the reactor
core from surrounding.

14. CAUSE:
 The Chernobyl disaster took place in the
reactor C4 on 26 April in 1986 around 1.23
am.
 The accident occurred during a safety test
mean to measure the ability of the steam
turbine to power the emergency feed water
pumps of an RBMK-type nuclear reactor in
the event of a simultaneous loss of external
power and major coolant leak.

15.  In Nuclear power plant It is important to
have a consistent supply of water at all time
for coolant.
 To ensure that the water pumps keep
working at all times there were some diesel
generators to provide electricity in
Chernobyl reactor in case of reactor shut
down.

16.  It takes about 1 or 2 minutes to start the
generator.
 The builders of the reactor had said that the
electricity needed for these 1-2 minutes
could be sourced from the reactor itself.
 The turbines would be moving because of
the steam and even after a reactor
shutdown ,there would be some amount of
steam, which would be enough to power
those plants.

17.  On 26 April ,1986, The experiment was begun at
night.
 The output of the power plant was 1600MW. To
start the experiment the workers were tasked to
reduce the output to 50% of its output, which is
750MW
 As soon as the workers inserted the control rods,
the power dropped even more and reached 30MW.

18. The reason for this sudden reduction of
the output is a byproduct called Xenon
135, which was created during these
fission reactions.
Similar to Boron, Xenon 135 could also
absorb the neutron quite efficiently.
This byproduct which was being created
in this reaction worked like control rods
and it reduced the output.

19.  Normally when xenon is produced in a nuclear
reaction it burns out within a few hours.
 But in this case, it kept getting accumulated in
the nuclear core. It is known as xenon
poisoning.
 Seeing that very little electricity was produced,
the shift supervisor ordered the workers to take
out some of the control rods.
 After taking out some of the control rods the
power output reached 200MW .

21. But still they couldn’t run their tests,
because required power output was
700MW.
They had to speed up the reaction further.
so the supervisor again ordered to take out
some of more control roads.
 211 control rods were present in that
reactor, out of 211 only 8 rods were inside
the reactor and 203 rods were taken out.

22. Due to this, power output spiked up. At
1.19 AM the power output increased
rapidly, and whatever little water was
present in the core, turned into steam
The xenon present in the reactor till then
which was working to slow down the
reaction burned out when reaction speed
up.

23.  So there were no more xenon to absorb the
neutrons this was the point of extreme power
surge. The speed of the nuclear reaction
increased exponentially. A lot of steam was
being produced here.
 Because of huge amount of steam the lid of the
containment structure started shaking.
Shokwaves were felt throughout the building.
 Workers realised that they have to execute an
emergency stop. So they pressed the
emergency stop button at around 1.23 AM.

24.  Pressing the button mean that the control
rods would be reinserted into the reactor to
slow down the reaction.
 But there was a design flaw in this reactor related to
control rods. Control rod was made up two parts:
a) The main part of the control rod was made of
Boron. It slows down the reaction by absorbing
the neutrons.
b) The tip were made up of graphite. It worked like
moderator and it speeded up the reaction.

25.  As soon as the button was pressed the power
generation of the reactor reached 33,000 MW.and this
caused a blast.
 Because of this blast , the core of the reactor started
melting, after 2-3 seconds of the first blast there was
another blast
 The 1000- ton lid on top of the structure, was blown
into air.

26.  The radioactive material started spreading through the
atmosphere.
 Two people were instantly killed in the blast
 More than 100 radioactive elements and 5%uranium
fuel, went into the atmosphere

28. RADIOACTIVITY RELEASES
Daily releases of radioactivity from the Chernobyl
plant .

29. Table I indicates that the escape of fission products
from the reactor occurred in four phases:
 The first involved the initial, highly energetic
release.
 This was followed by a gradual decrease in
the release rate, due partly to the relocation of
the core and partly to the deposition of about
5000 tons of material on the exposed reactor
vault. This material, which included boron
compounds, lead, dolomite, sand, and clay
provided a filtering action which retarded
fission product release.

30.  It probably also retarded natural cooling of the
core, since, on the sixth day, the daily rate of
release began to increase, possibly because
a fissure had formed in the blanket material.
This constituted the third phase of the release
pattern.
 The fourth phase was the sudden drop in
release rate on the tenth day after the
accident, which coincided with the injection of
cold nitrogen into the space beneath the
reactor.

32. GROUPING OF LIQUIDATORS
The time-oriented classification might divide
liquidators into three subtypes:
 During the initial phase, people called the “early
liquidators” were on site during the explosion or came in
during the initial phase of the accident (0-1 days, before
the evacuation of Pripyat), including fire fighters.

34.  The early phase ranges from the end of the
evacuation of Pripyat to the end of the
construction of the sarcophagus (November
1986).

36. The late phase liquidators worked between the
end of the Sarcophagus construction until the
dissolution of the USSR in 1991, when central
management of clean-up work was split
between Russia, Belarus and Ukraine.

37. RADIATION DOSES OF LIQUIDATORS
Physical Dosimetry and Documented Doses:
Documented doses mean doses stated for the individual
liquidator in various documents and references. These
doses have different origins but are commonly based on
physical dosimetry data.
Three main sources of these “documented” doses:
 Dose recorded by an individual dosimeter .Only 2-3% of
liquidators had a dosimeter during all time of their work .

38.  Group dose values assigned to the members of a group
performing an operation in the zone, based on the
readings of an individual dosimeter held by one member
of the group.
 Marching route dose values estimated from a dose rate
in the zone and the duration of stay of the group in this
area.

39. Figure 1 gives a sources of collective dose for a highly
exposed group of 1986 liquidators from staff of CNPP
and scientists from the Institute of Biophysics, Russian
Ministry of Public Health obtained by analysis of the
marching routs . This group consisted of 670 persons.
Total collective dose is 980 men Gy, mean individual
dose is 1.46 Gy.

44. EFFECT AND OUTCOMES
 Chernobyl Catastrophe Victims comprises into four main
groups:
 Group1: Persons involved in the clean up operations at
the Nuclear Plant (Liquidators)
 Group2: Persons evacuated from the exclusion zone
 Group3:Persons resident in the territories immediately
after the accident.
 Group4: Children born to parents

45. EFFECT AND OUTCOME CONTD
GROUP A: Immediate
Impact
 2 workers involved during
the safety test operation
died due to explosion.
 231 people mainly fireman
and emergency clean up
workers were hospitalised
immediately due to acute
radiation sickness.
 28 of them eventually died
in the first three months
after explosion.
GROUP B: Long Term
Impact
 International spread of
radioactivity
 Radioactivity release
 Residual radioactivity in the
environment.
 Socio Economical impact
 Health Effects
 Economic cost

46. LONG TERM IMPACT CONTD
International spread of radioactivity –
The nuclear meltdown provoked a radioactive cloud
which floated over Russia , Belarus, Ukraine
,Moldova and also some part of the Europe.
 Radioactive release-Highly radioactive
compounds that accumulate in he food chain, such
as some isotopes of iodine and Strontium
 All of the noble gases ,including krypton and xenon,
contained within the reactor were released
immediately into the atmosphere by the first steam
explosion

47.  About 55% of the radioactive iodine in the reactor was
released ,as a mixture of vapor, solid particles and as
organic iodine compounds.

48. Residual radioactivity in the environment:
a) Rivers, lakes and reservoirs:
 I-131, Cs-137,and Sr-90 in drinking water
caused concern during the weeks and months
after the accident.
 Bio-accumulation of radioactivity in water
bodies were high.
b) Fauna and Vegetation:
 Pine forest in the 10km^2 surrounding of the
reactor turned brown and died, earning the
name “Red Forest”
 Some animals in the worst hit areas also died or
stopped reproducing.

53. Socio economical impact:
 The agricultural sector was the area of the
economy worst hit by the effects of the accident.
 A total of 7,84,320 hectres of agricultural land
was removed and timber production was
halted for a total of 6,94,200 hectres of forest.
 Restrictions on agricultural production crippled
the market for food stuffs and other products
from the affected areas.

54. Health Effects:
Thyroid cancers:
 A large increase in the incidence of thyroid cancer
occurred among young children and adolescents lived in
the most contaminated areas of Belarus, the Russian
Federation and Ukraine.
 Radioactive iodine was deposited in pastures eaten by
cows who then concentrated it in their milk which was
subsequently drunk by children.

56.  Leukaemia and non-thyroid cancer:
 Causes a certain types of leukaemia (a malignancy of
blood cells).
 A small increase in the incidence of pre-menopausal
breast cancer in the most contaminated areas.
 Cataracts:
 The lens of the eye is very sensitive to ionizing radiation
and cataracts are known to result from effective dose of
about 2Sv.

57. Cardiovascular disease:
 A large Russian study among emergency workers has
suggested increased risk of death from cardiovascular
disease in highly exposed individuals.
 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.

58.  Reproductive and hereditary effects and children’s
health:
 Birth defects, infertility.

59. 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;

60.  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
 Radio ecological improvement of
settlements and disposal of radioactive
wastes.

61. Indirect Losses:
 Losses relating to the opportunity cost of removing
agricultural land and forests from use and the closure of
agricultural and industrial facilities.
 Opportunity costs, including the additional cost of energy
resulting from the loss of power from Chernobyl and the
cancellation of Belaru’s nuclear power programme.
 In Ukraine, 5-7% of govt. spending each year is still
devoted to Chernobyl related benefits and programmes.

62.  In Belarus, govt. 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 -
2003 was more than USD 13 billion.

64. HOW ARE HIGHLY CONTAMINATED AREAS
MANAGED?
What has been done to reduce exposure in
contaminated areas?
 During the first years after the accident, settlements in
contaminated regions of the USSR were cleaned up.
 Soon after the accident, the most effective agricultural
countermeasures to avoid human exposure to radioactive
iodine through milk were the use of "clean" fodder for
cattle and rejection of contaminated milk.

65.  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.

66.  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.

67. WHAT HAS BEEN DONE TO CONFINE THE DAMAGED
REACTOR AND NUCLEAR WASTE?
 Construction of the Shelter between May and
November 1986, aiming at environmental
containment of the damaged reactor,
reduced radiation levels on-site and prevented
further release of radionuclides off-site.

68.  To avoid the top of the Shelter collapsing, there are plans
to strengthen unstable structures and to build a New Safe
Confinement (NSC) that would cover the existing Shelter
and last more than 100 years.
 After the accident, the cleaning operations created a
large volume of radioactive waste and this was placed in
trenches and land-fills in the Exclusion Zone.

69. WHAT IS THE FUTURE OF THE RESTRICTED ACCESS AREA
SURROUNDING THE SITE?
The future of the Exclusion Zone for the next hundred
years and more is envisaged to be associated with
the following activities:
 Construction and operation of the NSC and relevant
engineering infrastructure;
 Defuelling, decommissioning and dismantling of
Units 1, 2 and 3 of the nuclear power plant and the
Shelter;

70.  Construction of facilities for processing and management
of radioactive waste, in particular a deep geological
repository for high-activity and long lived radioactive
material;
 Development of natural reserves in the area that remains
closed to human habitation; and
 Maintenance of environmental monitoring and research
activities.

72. RECOMMENDATIONS TO THE GOVT. OF BELARUS,
THE RUSSIAN FEDERATION AND UKRAINE.
 At the Chernobyl Forum meeting in April 2005, two
reports of the experts groups :
a) Health– coordinated by WHO
b) Environment--- coordinated by the IAEA.
 Recommendations on Health Care and
Research:
 Medical care and annual examinations of the
workers who recovered from ARS and other
exposed persons.

73.  Screening for thyroid cancer.
 Programs targeting minimisation of the psychosocial
impact on children and those who were children at the
time of accident should be encouraged and
supported.
 Recommendations on Environmental Monitoring
,Remediation and Research:
 Long term monitoring of radionuclides in various
environmental compartments is required.
 To inform the general public in affected areas about
the persistence of radioactive contamination in natural
food products.

74. PRESENT SCENARIO
Chernobyl has become a heaven for wildlife.

77. LESSONS LEARNED
 Containment Buildings- Containment building is
a reinforced steel, concrete or lead structure
enclosing a nuclear reactor.

78.  To use Moderator as a coolant material, so that in the
absence of coolant, reaction automatically stop.

79. BIBLIOGRAPHY
 THE CHERNOBYL ACCIDENT - CAUSES AND CONSEQUENCES*, CONP-8709104—
3
 Chernobyl’s Legacy: Health, Environmental and Socio-economic
Impacts and Recommendations to the Governments of Belarus, the
Russian Federation and Ukraine
 WWW.IAEA.ORG
 https://en.wikipedia.org/wiki/Chernobyl_disaster

80. THANK YOU