3- Nuclear Risk - A-Yamaguchi
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Transcript of 3- Nuclear Risk - A-Yamaguchi
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FrameworkforEnsuringNuclearSafety:
BeingPreparedforNuclearRisk
AkiraYamaguchi
DepartmentofEnergyandEnvironment
Osaka
University,
Osaka,
Japan
1
PresentedatCSD&M,1214December,2012
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Summaryof
Fukushima
Dai
ichi Accident
RadiationExposureofFukushimaResidents (for4monthsaftertheaccident) 99
out
of
25,520
exceed
10mSv
(public),
maximum
25.1mSv
48outof147exceed10mSv(workersinnuclearfacilities)
Confusioninevacuation,foodandwatercontrol
Contamination
of
land
is
significant
Ifemergencypreparednessworks,theyshouldhavebeenmitigated
Exposurelimitation
in
emergency
situation
Radioactivitycontrolinfoodanddrinks
Mitigationmeasureofsignificantradioactiverelease
2
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TheTsunamiCausedStationBlackout(SBO)and
Lossof
Ultimate
Heat
Sink
3
Unit1 Unit2 Unit 3 Unit4 Unit5 Unit6
Offsitepower X(0/6/7) X(0/6/7) X(0/6/7) X(0/6/7) X(0/6/7) X(0/6/7)
EmergencyDG X X X
(X) (X)
X (X) X (X) (X) O
(X)
Metal clad(6.9kV) X X X X X (X)
X X X X X O
X X (X)
Power center
(480V)
X O X X O
X O X O X O
X X O
DCbattery X X O X O O
X X O X O O
Ultimate heatsink X X X X X X
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Crossroadin
Fukushima
Dai
ichi Accident
EarthquakePracticallynodamageonsafetyfunctions at14:46,March11
TsunamiLossofmultifunctions(notonlysafetybutlogistics)at15:42
Stationblackout(SBO)
Lossofultimateheatsink(LUHS)
Lossofinstrumentationandcontrol
Lossofcommunicationandinformation(lighting,computer,mobilephone,
paging)
Lossofoffsiteexternalassistance
Fearonaftershockandanothertsunami
HydrogenExplosiononUnit1at15:36,March12
Lossofaccidentmanagement
Lossofaccessibility
Lossofhabitability
Fearonthenextexplosion
4
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Recoveryfrom
Disaster
Thestaffalwaysconsideredpriority;toselectthebestaction
on
the
worst
unit Knowledgebasemanagement
Mobileequipment
Carbatteries
Informationishelpfulforgooddecisionmaking
HelicopterflightconfirmedwaterinthespentfuelpoolonMarch16
Externalsupportstarted(SelfDefenseForce,Fire
ManagementAgency,
etc)
Corecoolingusingfireengines
Spentfuelpoolcooling usingconcretepumpvehicles
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LessonsLearned
Always,wecanmanage
Flexibility,knowledge
and
imagination
Agreementwithsocietybeforepreparation
Justificationof
nuclear
technology
Riskisuncertainty
6
Scrutinyofwhatwentwellandworseandpreparation
ofallpossibilitiesofSevereAccidentManagement
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HowtoEnsureSafety
RiskModel
in
Mathematical
Form
Toensuresafety,suppresstherisktolowlevel ReduceFrequency
MitigateConsequence
ItworksonlyIfweknowthefrequencypreciselyandwecontroltheconsequence
7
Risk Frequency Consequence
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FrequencyandConsequence;
WhichIs
More
Important?
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Frequency
Consequence
Large Risk
Small Risk
LowConsequence
Low
Frequency
Lackofknowledge
andrecognition
Large risk means large uncertainty
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LowFrequency:
What
Does
It
Mean?
9
F
requency
Consequence
Large Risk
Small Risk
LowConsequence
LowFrequency
Low frequency means less information (ignorance)
Lowlevelof
knowledge/
recognitionLikeliness
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Approach
to
Ensure
Safety
Limit
the
Risk
Riskisnotfrequencytimesconsequence
Riskcomes
from
uncertainty
which
we
cannot
be
free
from
Wemustbepreparedforuncertaintyandovercomeignorance
Approachtoprepareforuncertaintyandtolimit
the
risk
is
: Defense
in
Depth Whatcausestherisk?
Sourcetermorradioactivematerial:fissionproductcausestherisk
Whosustains
the
risk?
Publichealthandsafetyandenvironmentsustaintherisk
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WhatIsHazard? WhoShouldbe
Protected?
IdentifyHazardSource
Radioactivematerials
DefineSafetyObjective
Health
and
property
of
public
and
environment KeepHazardandPublicSeparate
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Hazardous
Material
Publichealth
andproperty,
environmentManagement
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3rd
Defense:Objective
Is
the
Goal
Toprotectpublicismostimportant
Emergencyresponse
is
scenarioless Scenarioisunpredictable
1st defensedependsonscenario
Flexibilityandknowledgebaseactionworks Managementsystem
Drilland
education
Safetyculture
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2nd
DefenseIs
Flexible
and
Broad
13
Hazard
(Fission
Product)
Healthand
safety,and
propertyof
public
1st Defence
Prevention
3rd Defence
Emergency
preparedness
NoSevereAccident RespondtoEmergency
Barrier/Distance/Time
2nd Defence
Mitigation
ContainFissionProduct
Management
Purposeofthe2nd defenseisambiguous
Boundariesare
overlapped
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AbsolutelyUnlikely
Is
Impossible
BlackSwan/WhiteRaven
14
BlackSwan (N.Taleb,2007) WhiteRavens(Hempel's Ravens)
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Four
Categories
of
Undesirable
Event
15
Recognition
UnknownknownUnknownunknownKnowled
ge
KnownknownKnownunknown
TwoBeyond
Design
Basis
Type:
Unlikely
Event
and
Rare
Event
Unlikely
RareUnknown
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Precursoris
Messenger
of
Safety
WhiteSnake(Iwakuni City,Yamaguchi,Japan)
Appearanceof
unknowns
is
messenger
of
safety
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KnownUnknown
Becomes
Reality
17
EarthquakeandtsunamiintheIndian
OceanoffSumatra:Kalpakkam NPP
Flooding:LeBlayais NPP,France
FortCalhounNPP:Missouri
RiverFloodingin2011,USA
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IdentificationandPreparationfor
Unknowns
KnownKnownisalreadyconsidered
Design
basis UnknownUnknownbecomesKnowns
PRAfindoutsequences(UnknownKnown) BWRcontainmentvesselfailure(SBOscenario):hardenedvent
Unexpectedevent
becomes
reality
(Known
Unknown)
SmallLOCAandhumanerror(TMI)
SBO+LUHS(FukushimaDaiichi)bytsunami
Unknownknown
is
investigated
in
detail
(stress
test)
Knownunknownisprotected(provisions)
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Role
of
Stress
Test,
PRA
and
Provisions
19
PRA Stresstest
DesignBasisUrgent Provisions
Knownunknown
Recognitionlevel
Knownknown
UnknownknownUnknown
unknown
Knowle
dgelevel Beyondrecognition
BeyondknowledgeResidualRisk
The1st Defense
The2nd Defens
How
to
Deal
with
the
Residual?
The3rd Defense
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Do
We
Accept
Residual
Risk?
20
Justitia
Justificationistheactionofdeclaringor
makingrighteousinthesightofGod
(OxfordDictionaryofEnglish)
Bereadytoacceptriskunderjustification
Butcontinue
to
reduce
/optimize
risk
IAEAFundamentalSafetyPrinciples
Facilitiesandactivitiesthatgiverisetoradiationrisksmustyield
anoverallbenefit.
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Conclusions Goodmanagementandknowledgeleadustotheright
wayatcrossroads
Preparationfor
Uncertainty
(Unpostulated scenario)
DefenseinDepth
UnlikelyEventandRareEvent
BeingPrepared
for
Three
Types
of
Unknowns
Stresstestcoversrareevent:Unknownknown
Appropriatebackfitpreparesfor:Knownunknown
PRAdealwithunlikelyevent:UnknownUnknown
Thereexist
clue
to
survival
anywhere;
Try
to
find
it
alwaysandcontinually
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