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L7 The
accident
at
FukushimaDaiichi:first
glimpse
Jos
Marques
ITN
[email protected]
IntensiveCourseonAcceleratorsandReactorOperation(ICARO)
ITN,Sacavm,March718,2011
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NuclearpowerinJapan Earthquake
Statusofnearbynuclearpowerplants
AccidentinFukushimaDaiichi Conclusions
Layout
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Japan's first commercial nuclearpower plant began operation
in
1966.
Japan has 55reactors operating around the country with
atotaloutputof 47,361MWe (net).
Mostly BWRtype (37units),followed by PWR(17units)and
FNR(1unit=Monju).
Nuclearpower
accounts
forapproximately
1/3of
the
country's totalelectric power output.
In2009only29%asseveralunitsclosedforverifications
afterearthquakein2007.
NuclearpowerinJapan
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2011March1105:46:23UTC Magnitude8.9 Location38.32N,142.37E
(US
Geological
Service)
ThirteenreactorsintheOnagawa,
Fukushima
Daiichi
andFukushimaDaini
sites
(InternationalNuclearSafety
Center,ANL,US)
Earthquake
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Onagawa
Unit1:automaticshutdown,coldshutdownat0:58,
March12.
Unit2:automaticshutdown.
Unit3:automaticshutdown,coldshutdownat1:17,March12.
Fireinoneturbinebuildingwasextinguishedat22:55
onMarch
11.
AnomalousradiationlevelsreportedonMarch13butallunitsreportedasbeingundercontrol.
Status
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FukushimaDaini
Unit1:automaticshutdown,coldshutdownat13:40,
March14
Unit2:automaticshutdown,coldshutdownat14:20,March14
Unit3:automaticshutdown,coldshutdownat12:15,March12.
Unit4:automaticshutdown. Nohighradiationlevelsdetected.
Status
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FukushimaDaiichi1
Reactor Type
Netpower
(MWe) OperatorReactorsupplier
Criticality
dateFUKUSHIMADAIICHI1 BWR 439 TEPCO GE/GETSC 10Oct70
FUKUSHIMADAIICHI2 BWR 760 TEPCO GE/T 10May73
FUKUSHIMADAIICHI3 BWR 760 TEPCO TOSHIBA 06Sep74
FUKUSHIMADAIICHI4 BWR 760 TEPCO HITACHI 28Jan78
FUKUSHIMADAIICHI5 BWR 760 TEPCO TOSHIBA 26Aug77
FUKUSHIMADAIICHI6 BWR 1067 TEPCO GE/T 09Mar79
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Containmentconsistsofadrywell(w/reactoranditscoolingequipment)andawetwell,insidebuilding.
ThedrywellismuchsmallerthanaPWRcontainmentandplaysalargerrole.
Duringaleakagedesignbasisaccidentthereactor
coolantflashes
to
steam
in
the
drywell,
pressurizing
it
rapidly.Ventpipesortubesfromthedrywelldirectthesteambelowthewaterlevelmaintainedinthe
wetwell
condensingthesteam,limitingthepressureultimatelyreached.
Buildingenclosingdrywellandwetwell
ismaintained
ataslight
negative
pressure
during
normal
operation
andrefuelingoperations.
FukushimaDaiichi1
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FukushimaDaiichi1
Reactorvesselinside
drywell(stainless
steel)
Wetwell
shapedasa
torus;also
known
as
suppressionpool.
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Responseof
areactor
to
anegative
step
change
of
reactivity,
or
theInhourequationstrikesagain
(Bennet,TheElementsofNuclearPower,3rdEd.,Longman,1989).
T1
Theaccident
Longest livingprecursor of
delayed
neutrons
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Fission
product
decay
heating
after
shutdown
(Bennet,
The
ElementsofNuclearPower,3rdEd.,Longman,1989).
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Uponascrampowergoesdownslowly
Decay
of
fission
products
Smallfractionofthetotalheatbeingreleasedduringnormaloperation.
Importantoncethereactorwasscrammed.Powersourcesforthecoolingpumps
Thereactoritself
Offsitepower(throughpowerlines)
Dieselgenerator
Theaccident
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FD1wasautomaticallystoppedwiththequake.
Externalpowerlostasseawatersweptawaythe
powerlines.
Dieselgeneratorsstartedtoprovidebackupelectricalpowertotheplantsbackupcoolingsystem.
Dieselgeneratorsstoppedafterapproximatelyonehourduetotsunamiinduceddamagetotheirfuel
supply.
Anisolationcondenserwasusedtoremovethedecayheatfromtheshutdownreactor.
Apparentlytheplantthenexperiencedasmalllossofcoolant
from
the
reactor.
Theaccident
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ReactorCoreIsolationCooling(RCIC)pumpswereusedtoreplacereactorcorewaterinventory,however,
they
lost
battery
supplied
DC
power.
DCpowerfrombatterieswasconsumedafterapproximately8hours.
Atthatpoint,theplantexperiencedacompleteblackout(noelectricpoweratall).
Hourspassedasprimarywaterinventorywaslostandcoredegradationoccurred(throughsome
combinationofzirconiumoxidationandcladfailure).
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Portabledieselgeneratorsweredeliveredtothesite.
ACpowerrestoredallowingforanotherbackup
pumpingsystem
to
replace
inventory
in
reactor
pressurevessel.
Pressureinthecontainmentdrywellroseaswetwell becamehotter.
Thedrywellwasventedtothereactorbuildingwhich
surroundsit.
Hydrogenproducedfromzirconiumoxidationwasventedfromthedrywellintothereactorbuilding.
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Chemicalreactionswithwaterandoxygen(Knief,NuclearEngineering,Taylor&Francis,1992).
Theaccident
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Hydrogeninreactorbuildingexplodedcausingittocollapsearoundthedrywell.
Thedrywellandthepressurevesselwerereportedtobeintact.
Seawaterstartedbeinginjectedintothepressurevesseltocontinuethecoolingprocess.
Boronaddedforreactivitycontrol.
Othersourcesclaimtheouterpartoftheprimaryconfinementisalsobeingflooded.
Attempttocoolthecorium?
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Explosion in Unit 1 on March 12, 2011.(www.spiegel.de)
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Unit 1 after the explosion. Unit 2 is shownundamaged
(www.spiegel.de).
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Reactor pressure vessel and drywell reported to beundamaged;
only containment building was damaged.
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Theaccident
Massive evacuation and contaminationcontrol
(www.spiegel.de).
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Theaccident
The French IRSN reported that the primary containmentis no
longer intact on March 15, after the third explosion.
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Theaccident
Accidents with core melt: no events for 25 years(data for 2010
and 2011 estimated).
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Theaccident
Chernobyl4
TMI2
FD1/2/3,
SaintLaurent
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Itisclearthatcoremelt(s)haveoccurred
H2
producingreactionsoccurathightemperature
AccidentasTMI2canserveasreference
DecreaseH2
pressure
Keepradioactivereleaseslow
Willmostlikelytakeuntiltheweekend
Ifcontrolislost,partoftheinventoryoffission
productsmay
be
released
Partofthef.p.isretainedinthefuel/corium;remainingis
releasedintowater
Partofthef.p.releasedintowaterwillreachtheatmosphere.
Whatcanhappen
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Stilltooearlytohaveaclearpicture
Noise
frommanychannels.
Severalunitsaffectedinthesameperiod
Disruptionofpowergrid(conventionalplantsalsoaffected)
Earlymitigationmeasures(evacuation/sheltering)
Preliminaryclassificationpointstoalevel4accident,i.e.,onlywithlocalconsequences
Comparable
to
other
accidents
such
as
Saint
Laurent
A2
(France)in1980
Mayescalatetolevels5or6
Numberofvictimsfromearthquakewillsurelyexceedlargelythenumberofvictimsintheaccident
Conclusions
