The Chernobyl disaster was the worst man-made disaster in history. On April 26, 1986 at the Chernobyl nuclear power plant in Ukraine, operator errors caused a reactor explosion that released large amounts of radioactive material into the atmosphere. Over 30 emergency workers died from acute radiation sickness in the months following. Thousands of cleanup workers also suffered health effects and died prematurely from radiation exposure. The radioactive fallout spread over much of Europe, contaminating wide areas and increasing cancer risks for millions of people living in affected regions.

1. Chernobyl disaster
Seminar topic 1

2. The worst manmade disaster in human history

3. Where is Chernobyl?

4. Geographical map

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

6. RMBK Reactor

7. Fuel assembler

8. 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

9. Day of disaster
25 April 1986
• 01:00 The preparation for the test
• 13:47 Lowering of the reactor power halted at 1,600 MWt
• 14:00 The ECCS was isolated
• 23:10 The power reduction resumed

10. 26 April 1986
• 24:00 Operation shift change
• 24:28 Power level is now 500 MWt and kept decreasing to 30 MWt
• 24:40 The operator withdrew some control rods
• 01:00 Power had risen to 200 MWt
• 01:03 Connecting the fourth main cooling pump to the left loop of the
system 200 MWt
• 01:07 Connecting the fourth main cooling pump to the right of the loop
system - this was a violation of NOP

11. 26 April 1986 (cont.)
• 01:19 Increased feed water flow to the steam drums and removed more
control rods -violation of NOP
• 01:23 The test was started
• 01:23:10 Automatic rods withdrawn from the core
• 01:23:21 Two groups of automated control rods were back to the core

12. 26 April 1986 (cont.)
• 01:23:30 Power kept increasing
• 01:23:40 Emergency button pushed
• 01:23:44 Power is at 300000 MWth
• 01:23:48 1st thermal explosion
• 01:23:55 2nd explosion

13. After the accident

14. Human Errors
• Isolation of the emergency core cooling system
• Unsafe amount of control rods withdrawn
• Connection of the four main cooling pumps to the right and left of the
system

15. Human Errors (cont.)
• Mental model
• The operator did not have a good mental model of the system itself
• Overconfidence
• By having an electrical engineer on site for an electrical test
• No confirmation of cues obtained from the system
• Beta too high
• Many missed signals before the accident

16. System Analysis
• Use of graphite as a moderator
• Lack of a well-built containment structure
• Inadequate instrumentation and alarms for an emergency situation
• There were no physical controls that prevented the operators from
operating the reactor in its unstable state

17. 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

18. Radioactive fallout

19. Direct Casualties
• 5.5 million people still live in contaminated areas
• 31 people died in 3 months of radiation poisoning
• 134 emergency workers suffered from acute radiation sickness
• 25,000 rescue workers died since then of diseases caused by radiation
• Cancer afflicts many others
• Increased birth defects, miscarriages, and stillbirths

20. Indirect Casualties
•By the year 2000 there were 1800 case of thyroid
cancer in children and adolescent
•High number of suicide and violent death among
Firemen, policemen, and other recovery workers

21. Left overs

22. Professor legasov

23. Vladimir Gorbachev

24. Radiation problems

25. liquidators

26. Radiation levels
• Normal occurring background radiation range is about 1.5-3.5
millisievert.
• Levels of radiation at Chernobyl. The radiation levels in the worst-hit
areas of the reactor building, including the control room, have been
estimated at 300Sv/hr. fatal dose in just over a minute.
• Now a days it is reduced to 34 Sv/hr. a lethel dose in 10-20 mins.

27. Problems Today
• The Sarcophagus
• After the disaster, a huge cement box was built around the radioactive material
• It is falling apart!
• According to a 2003 report by the Russian Atomic Energy Minister, Alexander Rumyantsev, "the concrete shell
surrounding the Chernobyl nuclear reactor is in real danger of collapsing at any time."
• A new Sarcophagus is scheduled to be completed in 2009.

28. Recent photo of Chernobyl with sarcophagus

29. losses
• Environmental loss
• Economic loss $935 billion(670000 crores)
• Death count-54
• Life of lakhs of people
• Farm lands
• Pripyat river

30. Recommendations
• Have proper Standard Operating Procedures (SOP) for both normal and
emergency situations
• Have scheduled trainings and practices for normal and emergency
situations
• Always have a reactor expert on site
• Have operators confirm any cues from the system before making
hypothesis or take action
• Have a team work kind of environment such that every body is involved

31. Thank you