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 station in Ukraine caused two explosions that released radiation and led to at least 31 deaths. Over 400,000 people were evacuated and large areas became permanently uninhabitable due to high radiation levels. The accident exposed flaws in the reactor design and in the Soviet regulatory system. It demonstrated the need for open communication, rapid evacuation procedures, and careful monitoring of food contamination in the event of a nuclear emergency. The long-term effects on health and the environment continue to be studied.

1. Chernobyl Nuclear Power Plant Disaster
26th April 1986
Most Severe Accident in the History of the Peaceful use of the Nuclear Energy
Presented By:
Gokul V. Mahajan.
M.Tech. Chem. Engg. Ist Yr.
National Institute of Technology, Tiruchirapalli
Tamilnadu, India

2. Introduction
• Chernobyl is located on the border area between Ukraine and Belarus.
• The Chernobyl nuclear power station was built in 1978-1979.
• This plant produced 10 % of Ukraine’s electricity.
• There were four unit (1 to 4 )in operating conditions and Unit 5and 6 unit under construction at the time of disaster.
• All four reactors were of RMBK-1000 type, each capable of producing 1000 MW Electrical power.
• This disaster happened in Reactor of Unit 4 during carrying out turbo generator efficiency test
• The test consisted on a simulation of a power failure, the objective was to determine how much time the turbines generate
energy despite the power failure .
• The explosion was caused mainly due to three types of errors: humans, design and automation.

3. Scenario Of RMBK-1000 Reactor
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 cooled and then condensed.
6. Condensed water pumped to bottom of the reactor core
and process repeats.

4. Day Of Disaster -26th April 1986
25th April 1986
01:00 The preparation for the test
13:47 Lowering of the reactor power halted at 1,500 MWt
14:00 The ECCS was isolated
23:10 The power reduction resumed
26th 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

5. Day Of Disaster -26th April 1986 (Continued….)
01:07 Connecting the fourth main cooling pump to the right of the loop system - this was a violation of NOP
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.
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

6. Main Reasons of the Accident
• Operation of the reactor at a very low operative reactivity surplus (ORS)
• Conducting of the experiment by the power below the level provided for test
• Blocking of the protection system relaying on water level and steam pressure in steam-separators
• Blocking of the protection system relaying on shutdown signal from two turbo generators
• Connection of all the main circulating pumps to the reactor.
• Switching off the emergency core cooling system (ECCS).

7. Before After

8. Effects of the accident.
• 203 people were hospitalized immediately ,31 of them eventually died.
• 20,000 peoples indirectly dead caused by the radiation (tumors and different organ disorders) (20% by suicide)
• 400,000 peoples evacuated.
• 100% increase in the incidence of cancer and leukemia.
• 250% increase in congenital birth deformities
• 1,000% increase in suicide in the contaminated zones.
• 25% of the country's farmland and forest contaminated at a dangerous level
• 10% of the land is unusable
• 1% of the entire land in Belarus was uncontaminated
• Forests ruined
• The total costs including cleanup, resettlement, and compensation to victims has been estimated to be roughly US$200
Billion.

9. Effects of the accident (Continued…)
Effects of Radiation

10. Effects of the accident (Continued…)
Flora
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”
Local pine trees grow huge pine cones, pine needles of the needle-like leaves 10 times heavier than normal

11. Effects of the accident (Continued…)
Fauna
Radiation has affected animals living near the site of Ukraine's Chernobyl nuclear disaster.
A major effect on the livestock was mutation.
The livestock was culled and buried.
Figure above: These animals suffering from a serious effect of
mutation
Figure above: A cow that experiencing mutations. This cow
having a cleft lip.

12. The factors that could have avoided disaster……
• Overcome on Reactor Design Shortcomings.
Low Steam Void Coefficient
High Operative Reactivity Surplus.
• Experiment without Safety Violations.
No Sudden reduction in Power (30 MW)
No Switching off Emergency Core cooling System.
Not Conducting experiment below defined power level.
• Proper Communication between different group of responsible workers.
Proper relieving to Night shift operator
• Advanced Automation and Trained employee.

13. Lessons Learned from Chernobyl Disaster
1. Tell the truth
After the Chernobyl disaster, the authorities failed to alert the public to the danger for three days, putting thousands of lives at
risk. Today, there is still a need for total transparency when it comes to nuclear accidents.
2. Evacuate
Soviet authorities were initially in denial over the extent of the crisis and failed to move people living close to the reactor to
safety in the hours and days after the incident. If they had acted sooner, countless lives would have been saved.
3. Closely monitor radiation levels in food
The cancers came about because Soviet authorities allowed children to continue to drink heavily contaminated milk. As a result,
many children received high doses of radiation to the thyroid.
4. Comply with safety rules
International reports have blamed the poor design of the Soviet RBMK (High Power Channel-type Reactor), a lack of safety
culture at the plant and errors by operators for the Chernobyl disaster.
5. Plan ahead

14. Past 29 Years…..
Chernobyl Humanitarian Assistance and Rehabilitation Programme (CHARP)
• Program running since 1990 by International Federation of Red Cross and Red Crescent Societies with local societies
• address basic health needs of those living in the regions of the 3 countries affected (Belarus, Russia, Ukraine)
Chernobyl Recovery and Development Programme (CRDP)
• Developed by the United Nations Development Program, initiated 2002
• Aim: return to normal life by providing support to the government of Ukraine for elaboration and implementation of
development oriented solutions for the regions.
• International Atomic Energy Agency (IAEA)
• employs a safeguards system which is among the most advanced at any safeguarded nuclear facility
• remote monitoring, on-site inspections, seals to ensure the non-diversion of nuclear material

15. References
The Chernobyl Reactor: Design Features and Reasons for Accident
http://www.rri.kyoto-u.ac.jp/NSRG/reports/kr79/kr79pdf/Malko1.pdf
Chernobyl Children’s Project International
http://www.chernobyl-international.com/aboutchernobyl/default.asp
Chernobyl.info. “Geographical location and extent of radioactive contamination”
http://www.chernobyl.info/index.php?navID=2#
Russian Research Center; Kurchatov Institute. “The Causes of the accident and its progress”
http://www.cs.ntu.edu.au/homepages/jmitroy/sid101/chernobyl/history.html
Time Magazine. May 12, 1986. “Deadly Meltdown”
http://www.time.com/time/daily/chernobyl/860512.cover.html
Uranium Information Center. August 2004. Nuclear Issues Briefing Paper 22. “Chernobyl Accident”
http://www.uic.com.au/nip22.htm
Ukrainian Web; Chernobyl Tour
http://www.ukrainianweb.com/chernobyl_ukraine.htm
Wikipedia, The Free Encyclopedia; Chernobyl accident
http://en.wikipedia.org/wiki/Chernobyl_accident

16. Any Questions
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