chernobyl disaster the worst manmade disaster in human history

Chernobyl Chernobyl disasterdisaster

The worst manmade disaster in The worst manmade disaster in human historyhuman history

Czech Technical University In PragueCzech Technical University In Prague

2323 MayMay 200 20077

23 May 2007 Czech Technical University in Prague

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Where is Chernobyl?Where is Chernobyl?


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ChernobylChernobyl

• Built in Built in 1978-19791978-1979

• ChornobylChornobyl


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BackgroundBackground

• Reaktor Bolshoy Moshehnosty Reaktor Bolshoy Moshehnosty KipyashiyKipyashiy

• RBMK, a Russian acronym translated RBMK, a Russian acronym translated roughly means “roughly means “reactor (of) high power reactor (of) high power (of the) channel (type)(of the) channel (type)””

• reactor cooled by water and moderated by reactor cooled by water and moderated by graphitegraphite


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RBMK ReactorRBMK Reactor


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Fuel assembliesFuel assemblies


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Reactor Plant ScenarioReactor Plant Scenario

1.1. As the reaction occurs, the uranium As the reaction occurs, the uranium fuel becomes hotfuel becomes hot

2.2. The water pumped through the core in The water pumped through the core in pressure tubes removes the heat from pressure tubes removes the heat from the fuelthe fuel

3.3. The water is then boiled into steamThe water is then boiled into steam

4.4. The steam turns the turbinesThe steam turns the turbines

5.5. The water is then cooledThe water is then cooled

6.6. Then the process repeatsThen the process repeats


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Day of disasterDay of disaster

25 April 198625 April 1986• 01:00 The preparation for the test01:00 The preparation for the test• 13:47 Lowering of the reactor 13:47 Lowering of the reactor

power halted at 1,600 MWtpower halted at 1,600 MWt• 14:00 The ECCS was isolated14:00 The ECCS was isolated• 23:10 The power reduction resumed23:10 The power reduction resumed


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26 26 AprilApril 19861986

• 24:00 Operation shift change24:00 Operation shift change• 24:28 Power level is now 500 MWt and kept 24:28 Power level is now 500 MWt and kept

decreasing to 30 MWtdecreasing to 30 MWt• 24:40 The operator withdrew some control 24:40 The operator withdrew some control

rods rods • 01:00 Power had risen to 20001:00 Power had risen to 200 MWtMWt• 01:03 Connecting the fourth main cooling 01:03 Connecting the fourth main cooling

pump to the left loop of the system 200pump to the left loop of the system 200 MWtMWt• 01:07 Connecting the fourth main cooling 01:07 Connecting the fourth main cooling

pump to the right of the loop system - pump to the right of the loop system - this was this was a violation of NOPa violation of NOP


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26 April 198626 April 1986 (cont.) (cont.)

• 01:19 Increased feed water flow to 01:19 Increased feed water flow to the steam drums and removed more the steam drums and removed more control rods -control rods -violation of NOPviolation of NOP

• 01:23 The test was started01:23 The test was started• 01:23:10 Automatic rods withdrawn 01:23:10 Automatic rods withdrawn

from the corefrom the core• 01:23:21 Two groups of automated 01:23:21 Two groups of automated

control rods were back to the corecontrol rods were back to the core


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26 April 198626 April 1986 (cont.) (cont.)

• 01:23:30 Power kept increasing01:23:30 Power kept increasing• 01:23:40 Emergency button pushed01:23:40 Emergency button pushed• 01:23:44 Power is at 300000 MWth01:23:44 Power is at 300000 MWth• 01:23:48 101:23:48 1stst thermal explosion thermal explosion• 01:23:55 201:23:55 2ndnd explosion explosion


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Human ErrorsHuman Errors

• Isolation of the emergency core cooling Isolation of the emergency core cooling systemsystem

• Unsafe amount of control rods withdrawnUnsafe amount of control rods withdrawn• Connection of the four main cooling Connection of the four main cooling

pumps to the right and left of the systempumps to the right and left of the system


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Human Errors (cont.)Human Errors (cont.)

• Mental modelMental model– The operator did not have a good mental The operator did not have a good mental

model of the system itselfmodel of the system itself

• OverconfidenceOverconfidence– By having an electrical engineer on site for By having an electrical engineer on site for

an electrical testan electrical test– No confirmation of cues obtained from the No confirmation of cues obtained from the

systemsystem

• Beta too highBeta too high– Many missed signals before the accidentMany missed signals before the accident


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Accident PreventionAccident Prevention


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System AnalysisSystem Analysis

• Use of graphite as a moderatorUse of graphite as a moderator• Lack of a well-built containment Lack of a well-built containment

structurestructure• Inadequate instrumentation and Inadequate instrumentation and

alarms for an emergency situationalarms for an emergency situation• There were no physical controls that There were no physical controls that

prevented the operators from prevented the operators from operating the reactor in its unstable operating the reactor in its unstable state state


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Summary of FactsSummary of Facts• April 26, 1986:April 26, 1986:

– Chernobyl nuclear power Chernobyl nuclear power plantplant• Operator errors cause a Operator errors cause a

reactor explosionreactor explosion• Explosion releases 190 tons Explosion releases 190 tons

of radioactive gasses into of radioactive gasses into the atmospherethe atmosphere

• Fire starts that lasts 10 daysFire starts that lasts 10 days

• People:People: – 7 million lived in 7 million lived in

contaminated areas; 3 contaminated areas; 3 million were childrenmillion were children

• Wind:Wind:– Carries radiation far Carries radiation far

distancesdistances


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Far Reaching RadiationFar Reaching Radiation


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Radioactive falloutRadioactive fallout


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Direct CasualtiesDirect Casualties

• 5.5 million people still live 5.5 million people still live in contaminated areasin contaminated areas

• 31 people died in 3 months 31 people died in 3 months of radiation poisoningof radiation poisoning

• 1134 emergency workers 34 emergency workers suffered from acute suffered from acute radiation sicknessradiation sickness

• 25,000 rescue workers died 25,000 rescue workers died since then of diseases since then of diseases caused by radiationcaused by radiation

• Cancer afflicts many othersCancer afflicts many others• Increased birth defects, Increased birth defects,

miscarriages, and stillbirthsmiscarriages, and stillbirths


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Indirect CasualtiesIndirect Casualties

– By the year 2000 By the year 2000 there were 1800 case there were 1800 case of thyroid cancer in of thyroid cancer in children and children and adolescentadolescent

– High number of High number of suicide and violent suicide and violent death among death among Firemen, policemen, Firemen, policemen, and other recovery and other recovery workersworkers


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Environment ImpactEnvironment Impact

• Areas still Areas still impacted today:impacted today:– SoilSoil– Ground WaterGround Water– AirAir– FoodFood

• Crops Crops • LivestockLivestock


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Problems TodayProblems Today

• The SarcophagusThe Sarcophagus– After the disaster, a huge After the disaster, a huge

cement box was built around cement box was built around the radioactive materialthe radioactive material

– It is falling apart!It is falling apart!– According to a 2003 report by According to a 2003 report by

the Russian Atomic Energy the Russian Atomic Energy Minister, Alexander Minister, Alexander Rumyantsev, "the concrete Rumyantsev, "the concrete shell surrounding the shell surrounding the Chernobyl nuclear reactor is Chernobyl nuclear reactor is in real danger of collapsing at in real danger of collapsing at any time."any time."

– A new Sarcophagus is A new Sarcophagus is scheduled to be completed in scheduled to be completed in 20092009


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RecommendationsRecommendations

• Have proper Standard Operating Have proper Standard Operating Procedures (SOP) for both normal Procedures (SOP) for both normal and emergency situationsand emergency situations

• Have scheduled trainings and Have scheduled trainings and practices for normal and emergency practices for normal and emergency situationssituations


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Recommendations Recommendations (cont.)(cont.)

• Always have a reactor expert on site Always have a reactor expert on site • Have operators confirm any cues Have operators confirm any cues

from the system before making from the system before making hypothesis or take action hypothesis or take action

• Have a team work kind of Have a team work kind of environment such that every body is environment such that every body is involved involved


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chernobyl disaster the worst manmade disaster in human history

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