Disaster in chernobyl 2

Chernobyl disasterChernobyl disaster
The worst manmade disaster in humanThe worst manmade disaster in human
historyhistory
Czech Technical University In PragueCzech Technical University In Prague
2323 MayMay 20020077

23 May 2007 Czech Technical University in Prague 2
Where is Chernobyl?Where is Chernobyl?

ChernobylChernobyl
• Built in 1978-Built in 1978-
19791979
• ChornobylChornobyl

BackgroundBackground
• Reaktor Bolshoy Moshehnosty KipyashiyReaktor Bolshoy Moshehnosty Kipyashiy
• RBMK, a Russian acronym translatedRBMK, a Russian acronym translated
roughly means “roughly means “reactor (of) high powerreactor (of) high power
(of the) channel (type)(of the) channel (type)””
• reactor cooled by water and moderated byreactor cooled by water and moderated by
graphitegraphite

RBMK ReactorRBMK Reactor

Fuel assembliesFuel assemblies

Reactor Plant ScenarioReactor Plant Scenario
1.1. As the reaction occurs, the uranium fuelAs the reaction occurs, the uranium fuel
becomes hotbecomes hot
2.2. The water pumped through the core inThe water pumped through the core in
pressure tubes removes the heat from the fuelpressure tubes removes the heat from the 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

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 power halted at13:47 Lowering of the reactor power halted at
1,600 MWt1,600 MWt
• 14:00 The ECCS was isolated14:00 The ECCS was isolated
• 23:10 The power reduction resumed23:10 The power reduction resumed

2626 AprilApril 19861986
• 24:00 Operation shift change24:00 Operation shift change
• 24:28 Power level is now 500 MWt and kept decreasing24:28 Power level is now 500 MWt and kept decreasing
to 30 MWtto 30 MWt
• 24:40 The operator withdrew some control rods24:40 The operator withdrew some control rods
• 01:00 Power had risen to 20001:00 Power had risen to 200 MWtMWt
• 01:03 Connecting the fourth main cooling pump to the01:03 Connecting the fourth main cooling pump to the
left loop of the system 200left loop of the system 200 MWtMWt
• 01:07 Connecting the fourth main cooling pump to the01:07 Connecting the fourth main cooling pump to the
right of the loop system -right of the loop system - this was a violation of NOPthis was a violation of NOP

26 April 198626 April 1986 (cont.)(cont.)
• 01:19 Increased feed water flow to the steam01:19 Increased feed water flow to the steam
drums and removed more control rods -drums and removed more control rods -violationviolation
of NOPof NOP
• 01:23 The test was started01:23 The test was started
• 01:23:10 Automatic rods withdrawn from the01:23:10 Automatic rods withdrawn from the
corecore
• 01:23:21 Two groups of automated control rods01:23:21 Two groups of automated control rods
were back to the corewere back to the core

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 explosionthermal explosion
• 01:23:55 201:23:55 2ndnd
explosionexplosion

Human ErrorsHuman Errors
• Isolation of the emergency core cooling systemIsolation of the emergency core cooling system
• Unsafe amount of control rods withdrawnUnsafe amount of control rods withdrawn
• Connection of the four main cooling pumps toConnection of the four main cooling pumps to
the right and left of the systemthe right and left of the system

Human Errors (cont.)Human Errors (cont.)
• Mental modelMental model
– The operator did not have a good mental model ofThe operator did not have a good mental model of
the system itselfthe system itself
• OverconfidenceOverconfidence
– By having an electrical engineer on site for anBy having an electrical engineer on site for an
electrical testelectrical test
– No confirmation of cues obtained from the systemNo confirmation of cues obtained from the system
• Beta too highBeta too high
– Many missed signals before the accidentMany missed signals before the accident

Accident PreventionAccident Prevention

System AnalysisSystem Analysis
• Use of graphite as a moderatorUse of graphite as a moderator
• Lack of a well-built containment structureLack of a well-built containment structure
• Inadequate instrumentation and alarms for anInadequate instrumentation and alarms for an
emergency situationemergency situation
• There were no physical controls that preventedThere were no physical controls that prevented
the operators from operating the reactor in itsthe operators from operating the reactor in its
unstable stateunstable state

Summary of FactsSummary of Facts
• April 26, 1986:April 26, 1986:
– Chernobyl nuclear power plantChernobyl nuclear power plant
• Operator errors cause a reactorOperator errors cause a reactor
explosionexplosion
• Explosion releases 190 tons ofExplosion releases 190 tons of
radioactive gasses into theradioactive gasses into the
atmosphereatmosphere
• Fire starts that lasts 10 daysFire starts that lasts 10 days
• People:People:
– 7 million lived in contaminated7 million lived in contaminated
areas; 3 million were childrenareas; 3 million were children
• Wind:Wind:
– Carries radiation far distancesCarries radiation far distances

Far Reaching RadiationFar Reaching Radiation

Radioactive falloutRadioactive fallout

Direct CasualtiesDirect Casualties
• 5.5 million people still live in5.5 million people still live in
contaminated areascontaminated areas
• 31 people died in 3 months of31 people died in 3 months of
radiation poisoningradiation poisoning
• 1134 emergency workers suffered34 emergency workers suffered
from acute radiation sicknessfrom acute radiation sickness
• 25,000 rescue workers died since25,000 rescue workers died since
then of diseases caused bythen of diseases caused by
radiationradiation
• Cancer afflicts many othersCancer afflicts many others
• Increased birth defects,Increased birth defects,
miscarriages, and stillbirthsmiscarriages, and stillbirths

Indirect CasualtiesIndirect Casualties
– By the year 2000 there wereBy the year 2000 there were
1800 case of thyroid cancer1800 case of thyroid cancer
in children and adolescentin children and adolescent
– High number of suicide andHigh number of suicide and
violent death amongviolent death among
Firemen, policemen, andFiremen, policemen, and
other recovery workersother recovery workers

Environment ImpactEnvironment Impact
• Areas still impactedAreas still impacted
today:today:
– SoilSoil
– Ground WaterGround Water
– AirAir
– FoodFood
• CropsCrops
• LivestockLivestock

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

RecommendationsRecommendations
• Have proper Standard Operating ProceduresHave proper Standard Operating Procedures
(SOP) for both normal and emergency situations(SOP) for both normal and emergency situations
• Have scheduled trainings and practices forHave scheduled trainings and practices for
normal and emergency situationsnormal and emergency situations

Recommendations (cont.)Recommendations (cont.)
• Always have a reactor expert on siteAlways have a reactor expert on site
• Have operators confirm any cues from theHave operators confirm any cues from the
system before making hypothesis or take actionsystem before making hypothesis or take action
• Have a team work kind of environment suchHave a team work kind of environment such
that every body is involvedthat every body is involved

Disaster in chernobyl 2

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