Quantification of the Lifecycle Greenhouse Gas Emissions from Nuclear Power Generation Systems

13 Pages·2016·0.77 MB·English

energies
Article
Quantification of the Lifecycle Greenhouse Gas
Emissions from Nuclear Power Generation Systems
AkhilKadiyala1,RaghavaKommalapati1,2,*andZiaulHuque1,3
1 CenterforEnergy&EnvironmentalSustainability,PrairieViewA&MUniversity,PrairieView,
TX77446,USA;[email protected](A.K.);[email protected](Z.H.)
2 DepartmentofCivil&EnvironmentalEngineering,PrairieViewA&MUniversity,PrairieView,
TX77446,USA
3 DepartmentofMechanicalEngineering,PrairieViewA&MUniversity,PrairieView,TX77446,USA
* Correspondence:[email protected];Tel.:[phone]
AcademicEditor:PierreTrambouze
Received:5July2016;Accepted:19October2016;Published:25October2016
Abstract: Thispaperstatisticallyquantifiesthelifecyclegreenhousegas(GHG)emissionsfromsix
distinctreactor-based(boilingwaterreactor(BWR),pressurizedwaterreactor(PWR),lightwater
reactor (LWR), heavy-water-moderated reactor (HWR), gas-cooled reactor (GCR), fast breeder
reactor(FBR))nuclearpowergenerationsystemsbyfollowingatwo-stepapproachthatincluded
(a)performingareviewofthelifecycleassessment(LCA)studiesonthereactor-basednuclearpower
generationsystems;and(b)statisticallyevaluatingthelifecycleGHGemissions(expressedingrams
ofcarbondioxideequivalentperkilowatthour,gCO e/kWh)foreachofthereactor-basednuclear
2
powergenerationsystemstoassesstheroleofdifferenttypesofnuclearreactorsinthereductionofthe
lifecycleGHGemissions. Additionally,thisstudyquantifiedtheimpactsoffuelenrichmentmethods
(centrifuge, gaseous diffusion) on GHG emissions. The mean lifecycle GHG emissions resulting
fromtheuseofBWR(samplesize,N=15),PWR(N=21),LWR(N=7),HWR(N=3),GCR(N=1),
andFBR(N=2)innuclearpowergenerationsystemsare14.52gCO e/kWh,11.87gCO e/kWh,
2 2
20.5gCO e/kWh,28.2gCO e/kWh,8.35gCO e/kWh,and6.26gCO e/kWh,respectively. TheFBR
2 2 2 2
nuclearpowergenerationsystemsproducedtheminimumlifecycleGHGs.Thecentrifugeenrichment
methodproducedlowerGHGemissionsthanthegaseousdiffusionenrichmentmethod.
Keywords: lifecycle assessment; greenhouse gas emissions; nuclear energy; power generation;
reactors;enrichment
1. Introduction
Nuclearenergymaybedefinedastheenergyharnessedfromcontrolledreactionswithinthe
nucleiofatomsthatreleaseenergy. Typically,thecontrolledreactionsareperformedinsideanuclear
reactorthatcomprisesofsevenmajorcomponents—fuel,moderator,controlrods,coolant,pressure
vessel or pressure tubes, steam generator, and containment [1]. Uranium (in the form of uranium
oxidefuelrods)isthemostwidelyusedfuelinnuclearreactors. Themoderatorisusedtoslowdown
theneutronsthatarereleasedfromfissiontoenablemorefission. Water(ordinarywater)isthemost
widelyusedmoderator. Alternatively,heavywater(10%denserthanordinarywaterwithaneutron
moderatingratio80timeshigherthanordinarywater)andgraphitemayalsobeusedasmoderators.
The control rods are neutron-absorbing materials that are inserted or withdrawn from the core to
controltherateofreaction,ortohaltit. Thecontrolrodsaremadefromoneofthematerialssuch
ascadmium,hafnium,andboron. Thecoolantisafluidthatcirculatesthroughthecoretotransfer
heat. Wateristhemostwidelyusedcoolant. Apressurevesselisarobuststeelvesselthatcontains
nuclearfuel,moderator,controlrods,andcoolant. Pressuretubesareaseriesoftubescontainingthe
Energies2016,9,863;doi:10.3390/en9110863 www.mdpi.com/journal/energies
Energies2016,9,863 2of13
fuelthroughwhichthecoolantiscirculatedandsurroundedbyamoderator. Thesteamgenerator
isaheatexchangerthattransmitsthethermalenergygeneratedinthereactorcoretoproducesteam
fortheturbinefromaworkingfluid. Thecontainmentisathickconcreteandsteelstructure,whichis
designedtoprotectthereactorfromoutsideintrusionandtoprotectthepeopleoutsidefromtheeffects
ofradiationincaseofanyseriousmalfunctionwithinthenuclearreactor.
Thetotalelectricitygeneratedin2012acrosstheworldwasreportedtobe21.53trillionkilowatt
hours(kWh)[2]. Nuclearenergyaccountedfor2.35trillionkWh(10.9%)oftheworld’stotalelectricity
generatedin2012. Theprojectedworldelectricitygenerationfor2040is39trillionkWh(anincrease
by81%from2012)[3]. Nuclearenergyhasbeenprojectedtoaccountfor5.5trillionkWh(14%)ofthe
world’stotalelectricitygenerationin2040,withanannualincreaseof2.5%. Thesestatisticsindicate
thatnuclearenergyhasavitalroletoplayinmeetingtheworld’senergydemand.
Under such circumstances, one needs to statistically quantify the lifecycle greenhouse gas
(GHG)emissionsresultingfromtheadoptionofdifferenttypesofnuclearpowergenerationsystems.
Thelifecycleassessment(LCA)approachhelpsquantifythenetGHGemissionsresultingfromthe
use of nuclear energy as a fuel. LCA is an analytical method that provides an assessment of the
environmentalimpactsoftheconsideredproductsandtechnologiesfroma‘cradletograve’systems
perspectiveutilizingthedetailedinputandoutputparametersthatoperatewithinthedesignated
systemboundaries.
ManystudiesanalyzedtheLCAofnuclearpowergenerationsystems[4–29]. Theuseofnuclear
powergenerationsystemsacrosstheworldisbeingencouragedinviewoftheadvantagesthatnuclear
energyservesasanalternativetotherapidlydepletingfossilfuels,accountsfortheintermittencyand
theunpredictabilityissuesassociatedwiththerenewableenergysourcesbycontinuallygenerating
power(approximately90%oftheannualtime),andhelpsimproveairqualityconsideringthatthey
producenoGHGsoremissionsthatcausestheformationofacidrainorurbansmog[30].Theextensive
useofnuclearpowergenerationsystemsisinhibitedbyissuessuchasthemanagementofnuclear
waste,therecoveryofinvestmentcosts,andsecurityconcerns.
ThemajorityofthenuclearLCApublicationstodateemphasizedthedeterminationofthelifecycle
GHGemissionsfromselectnuclearpowergenerationsystems. Therewerelimitedstudies[31,32]
thatanalyzedthelifecycleGHGemissionsacrossabroaderspectrumofnuclearpowergeneration
systems. None of the earlier studies quantified the lifecycle GHG emissions and compared them
acrossallthecurrentlyavailabledistinctnuclearreactor-basedandfuelenrichmentmethod-based
power generation systems. This study aims to fill this knowledge gap by performing a review of
theliteratureonallthecurrentlyavailablenuclearLCAstudies,followedbyastatisticalevaluation
ofthelifecycleGHGemissionsfromthereviewednuclearpowergenerationsystemsindividually.
The results from the statistical evaluation of the lifecycle GHG emissions will assist energy policy
makersandenvironmentalprofessionalsinidentifyingandencouragingtheuseofenvironmentally
friendlynuclearoptionstogeneratepowerwithminimalGHGemissions. PerformingtheLCAfor
nuclearpowergenerationsystemswouldadditionallyprovidedetailsthatmaybeincorporatedinto
makingacomparisonwiththeGHGsemittedfromotherpowergenerationtechnologies.
2. Methodology
Areviewoftheliteratureshowedthatthenuclearpowergenerationsystemsmaybecategorized
onthebasisofthetypeofnuclearreactor,whicharecharacterizedbythefueltype,themoderator
type,andthecoolanttype. Thesixcommontypesofnuclearreactorsthatareemployedforpower
generationacrosstheworldareasfollows[33]:
• Boilingwaterreactor(BWR):BWRsareasingle-loopsystemthatmakessteamintheprimary
circuititselfabovethereactorcore. BWRsgenerallyoperateusinguraniumdioxide(UO )asthe
2
fuelandwater(H O)asthemoderatoraswellasthecoolant. ThereactorcoreinaBWRcomprises
2
ofupto800fuelassembliesormore. ThefuelassembliesoftheBWRarecomprisedofa7×7to
10×10squarearrayoffuelpins,surroundedbyametalfuelchannelthatpreventthemovement
Energies2016,9,863 3of13
ofsteam-watermixturebetweenthefuelassemblies,therebyensuringadequatecoolingofthefuel
assemblies. Thefeedwater(pumpedintothesteelreactorvesselcontainingthecore)isconverted
tosteamasaresultoftheheatgeneratedbyfissionchainreactionsoccurringwithinthefuelpins.
Thereactivitycontrolisimplementedthroughacombinationofneutron-controllingfuelrods
(madeofboroncarbide-filledpins)andcoolantflowadjustment. Thesteam-watermixturethat
leavesfromthetopofthecoreentersthestageofmoistureseparationwherethewaterdroplets
areremovedbeforethesteamisallowedtoenterthesteamline. Thesteamlinethendirectsthe
steamtoturntheturbinegeneratortoproduceelectricity.
• Pressurizedwaterreactor(PWR):PWRshavewaterinaprimarycooling/heattransfercircuitand
generatesteaminasecondarycircuit. LikeBWRs,PWRsalsooperatewithUO asthefueland
2
H Oasthemoderatoraswellasthecoolant. ThereactorcoreinalargePWRcomprisesof150
2
to200fuelassemblies,ormore. ThefuelassembliesofthePWRarecomprisedofa14×14to
17×17squarearrayoffuelpinsorupto331hexagonalfuelpins. InthePWRs,thereisnometal
fuelchannelasthesingle-phaseprimaryfluid(water)operatedbetterthantheBWR’sboiling
coolant. Thewaterintheprimaryloopismaintainedasaliquidunderhighpressureandenters
thesteelreactorvesselcontainingthecorethroughinletnozzles. Thewaterflowsdownward
along the inner vessel wall and flows up through the fuel assemblies gathering heat energy,
andexitsthroughtheoutletnozzleasaliquid. Theheatenergyfromtheprimaryloopisextracted
by the steam generators (secondary circuit) that convert the water into steam. The reactivity
controlisimplementedthroughneutron-controllingfuelrods(madeofboroncarbide-filledpins)
andsolubleneutronpoisonboricacid. Thesteam-watermixturethatleavesfromthetopofthe
secondarycircuitentersthestagesofmoistureseparation. Thesteamlinethendirectsthesteamto
turntheturbinegeneratortoproduceelectricity.
• Heavy-water-moderatedreactor(HWR):HWRsarealsoatwo-loopsystemlikePWRswiththe
exceptionthatheavywater(inprimaryloop)transferstheheattowater(insecondaryloop)for
generationofsteam. TheHWRsoperatewithUO asthefuelandheavywater/deuteriumoxide
2
(D O) as the moderator as well as the coolant. The Canadian Deuterium-Uranium (CANDU)
2
reactoristhesignaturerepresentativeofHWRs. Thepressurizedheavywater(PHW)CANDU
alsocontainsatwo-loopsystem,likethePWRs,withtheprimaryPHWlooptransferringtheheat
toaloopofordinarywaterforsteamproduction. Theprimaryfluid,i.e.,thePHWisdistributed
among the pressure tubes that pass through a large Calandria vessel that contains a separate
heavywatermoderator. Thecoolantiscollectedintwoseparateloops. Thefuelassembliesofthe
HWRsarecomprisedofuraniumdioxidefuelpelletscladinzirconium. Thereactivitycontrolis
accomplishedthroughonlinefueling(amachine-basedtechniquethatenableschangingthefuel
ofanuclearreactor,whilethereactoriscritical)thatisrequiredtocompensateforlowreactivity
inherentinnaturaluranium. Thesteam-watermixturethatleavesfromthetopofthesecondary
circuitentersthestageofmoistureseparationforsegregationofsteam,whichispassedintothe
steamlinetofinallyturntheturbinegeneratorforproducingelectricity.
• Gas-cooledreactors(GCR):TheinitialversionofGCRsusednaturaluraniumasthefuel,graphite
asthemoderator,andnatural-circulationairforcooling. SubsequentGCRsutilizedgraphiteas
themoderatorincombinationwithnaturalorenricheduraniumasthefuel,andcarbondioxide
(CO )orheliumasthecoolant. TheMagnoxreactorhavingatwoloopsystemwithCO asa
2 2
primarycoolant,gastowastestreamgenerators,andnaturaluraniumasthefuelisrepresentative
oftheGCRs. ThedevelopmentofCO gas-cooledreactorsisinhibitedbythecoolantlimitations
2
suchasexcessivecorrosioninpipingandsteamgeneratorsunderhightemperatures.
• Light-water-cooledgraphitemoderatedreactor(LWGR)/pressuretubegraphitereactor(PTGR):
TheLWGR/PTGRusesgraphiteasanarrayofblockstoactasamoderatorincontrollingthe
neutronsandcomprisesofadirectsteamcyclelikeBWRs. LiketheHWRs,theLWGR/PTGR
reactorsalsohaveacomplexpressuretubedesignwithseparatecoolantandmoderatorinthecore.
LWGRs/PTGRsoperatewithUO asthefuel,graphiteasthemoderator,andH Oasthecoolant.
2 2
Energies2016,9,863 4of13
Thesoviet-eraReaktorBolshoyMoshchnostiKanalnyy(RBMK)isrepresentativeofthePTGR.
Thereareapproximately1900verticalpressuretubesthataccommodatemultiplefuelassemblies
orcontrolrodsinaRBMKreactor. ThepressuretubesintheRBMKreactoraresurroundedbyan
arrayoflong,square-shapedgraphiteblockssetsidebysidetoresembleacylindershapethat
functionsasamoderator. IntheRBMKreactor,waterisintroducedfromthebottomofthecore
and enters the pressure tubes. The water then boils due to the fission heat from the fuel pins.
Thesteamisthendrawnoutforuseinoneofthetwosteamgenerators. Thepressuretubesand
thepipingareenclosedwithinasteelreactorvessel. ThefuelassembliesoftheRBMKreactor
includetwosub-assembliesof18zirconium-cladfuelpinsofenricheduranium. Thereactivity
controlisaccomplishedthroughonlinefueling,asnotedinthecaseofHWRs.
• Fastbreederreactor(FBR):FBRsworkontheprincipleofbreedingmorenewfuelthanthatis
requiredfortheneutronchainreaction. FBRsgenerallyoperateusingUO orplutoniumdioxide
2
(PuO ) as the fuel, have no moderator, and use sodium (Na) as the coolant. The liquid metal
2
fastbreederreactor(LMFBR)representstheFBRandhasthreeloops(firsttwoloopswithNa,
third loop with water) in the steam cycle. The intermediate loop isolates the first loop from
comingincontactwiththethirdloop. TheprimaryloopNabecomesradioactivefromneutron
absorptionandalsopicksupfission-productradionuclides.Whenthiscomesincontactwithwater,
itcanleadtoprecipitationasanexothermicreactionandradioactivecontamination. Thefuelfor
LMFBRcomprisesofmixed-oxide(MOX:PuO -UO )pelletsthatareloadedintothinstainless
2 2
steel cladding tubes to form hexagonal array fuel assemblies. Additional depleted or natural
uraniumisusedasacovertotheMOXcoretooptimizethebreeding. Thereactivitycontrolis
accomplishedthroughtheuseofneutron-poisoncontrolrods.
Amongstthecurrentlyavailablecommercialnuclearreactorsacrosstheworld,PWRs(numberof
installations, N = 277) are the most widely used nuclear reactors, followed by BWR (N = 80),
i i
HWR(N =49),GCR(N =15),LWGR/PTGR(N =15),andFBR(N =2)[1].Somestudies[16,18,20,27]
i i i i
performed the LCA by combining the BWR and the PWR nuclear power generation systems,
andreferredtothemasthelightwaterreactors(LWRs)basedonthecategorizationinaccordance
with the medium of moderator. Accordingly, this study adopted the use of LWR as an additional
categorytothegeneralclassification(BWR,PWR,HWR,GCR,LWGR/PTGR,andFBR)proposedby
theNuclearEngineeringInternationalHandbook[33]inquantifyingthelifecycleGHGemissionsfrom
nuclearpowergenerationsystems. EachofthereviewednuclearLCAstudycasedescriptionswasfirst
categorizedonthebasisofthereactortype. Next,thelifecycleGHGemissionsfromthereactor-based
and the fuel enrichment method-based nuclear power generation systems were quantified using
statistical metrics (sample size, mean, standard deviation, minimum, maximum, standard error
of the mean, quartile 1, quartile 2 or median, quartile 3) and graphical representations (error bars
representingthemeanwith95%confidenceintervals,boxplotsrepresentingthequartileswithoutliers).
Thesamplesizeisameasurethatindicatesthetotalnumberofobservations. Themeanisameasure
thatrepresentsthecentraltendencyoftheobserveddata. Thestandarddeviationisameasureusedto
quantifythedegreeofvariationwithinasetofobservationsfromasinglesample. Theminimumand
maximummeasuresdefinetheleastobservationandthehighestobservationwithaconsideredsample,
respectively. Thestandarderrorofthemeanisameasurethatestimatesthevariabilitybetweensample
means obtained by taking multiple samples from the same population. The standard error of the
meandeterminestheprecisionbetweenthemeanofthesampleestimatesandthepopulationmean.
Thequartilestatisticsareasetofthreemeasuresthatdividearankedsetofobserveddatavaluesinto
fourequalgroupswitheachgroupcomprisingaquarterofthedata. Whiletheerrorbarsdemonstrate
thedegreeofconfidenceinthemeanGHGemissions,theboxplotsprovideinformationonthedegree
ofvariationamongtheLCAstudiescharacterizedbydifferentbiomassfeedstockcategories.
Thisstudyislimitedinitsscopebynotincludingthecategoryofsmallmodularreactors(SMRs)
that are capable of generating the power on a small scale and have been gaining prominence in
recentyears.
Energies2016,9,863 5of13
3. ResultsandDiscussion
3.1. ReviewofNuclearLCAStudies
Therearenumerousstudies[4–29]thatevaluatedthelifecycleenvironmentalimpactsofusing
nuclear reactors for power generation. One needs to define the system boundary conditions
(thatincludesdetailsontheactivitiesorprocessestobeconsideredintheanalysis)andafunctional
unitofmeasure(thatenablesquantificationofthenetenvironmentalimpactsfromcarryingoutan
activityoraprocessasdefinedwithintheLCAsystemboundaryconditions)whenperformingaLCA.
Themajorityoftheaforementionedstudies[4–12,14–27,29]thatperformedtheLCAofnuclear
power generation systems defined the system boundary conditions to include front-end activities
(mining, milling, refinery, conversion, enrichment, fuel fabrication), operation of power plants
to generate electricity, back-end activities (interim storage, waste conditioning, waste disposal),
transportation,constructionofthenuclearpowerplant,anddecommissioningofthenuclearpower
plant. Onestudy[13]definedtheirboundaryconditionstoincludealltheactivitiesassociatedwiththe
majorityofthestudiesthatarelistedaboveandtheonlyexceptionbeingthatthefuelcycleresults
wereborrowedfromthethenexistingliterature. Theremainingstudy[28]consideredalltheactivities
associatedwiththemajorityofthestudiesthatarelistedaboveandadditionallyincludedtheactivities
relatedtopowerdistributiontoendusers.
The common functional unit of measure adopted by the majority of the nuclear LCA studies
is grams of CO equivalent per kilowatt hour (gCO e/kWh) of electricity produced. Accordingly,
2 2
this study also adopted the functional unit of measure for GHG emissions to be gCO e/kWh of
2
electricityproduced.
Table 1 provides a summary of the GHG emissions (in gCO e/kWh) for ∆different nuclear
2
reactortypesonthebasisofthereviewed26nuclearpowergenerationLCAstudies(having49case
representations). Table1alsoprovidesadditionaldetailssuchastheelectricitygenerationcapacity
(EGC, in MW), the thermal efficiency (η, in %), the capacity factor (CF, in %), the plant lifetime
t
(PL,inyears),thefuelenrichmentmethod(FEM—gaseousdiffusion(D),centrifuge(C),mixturewith
gaseous diffusion dominance (M-D), mixture with centrifuge dominance (M-C), mixture with
equivalent proportions of gaseous diffusion and centrifuge (M-DC)), the uranium ore-grade
(UOG,in%), theLCAmethodtype(LCAType—processanalysis(Process), input-outputanalysis
(I-O), mix of process analysis with input-output analysis (Hybrid)), and the geographical location
(GL)fortheinstallednuclearpowergenerationsystems. TheEGCmaybedefinedastheamount
of electrical power that is produced under standard operating conditions. η is the ratio of gross
t
electricitygeneratedtothermalenergy. Itisrelatedtothedifferenceintemperaturebetweenthesteam
from the reactor and the coolant. The CF is the ratio of the average power generated to the rated
peakpower. ThePLindicatesthelicensedoperationallifespanofthenuclearreactorconsideredin
thestudy. TheFEMindicatesthetypeofprocessadaptedinfuel(uranium)enrichment. TheUOG
denotesthegradeofuranium. TheGLindicatesthesite-specificlocationofthenuclearpowerplant
beingexamined.
Basedonthereviewof26nuclearpowergenerationLCAstudies(with49caserepresentations,
refertoTable1),onemaynotethatthePWR(N=21)nuclearpowergenerationsystemsweremorein
numbercomparedtotheBWR(N=15),LWR(N=7),HWR(N=3),FBR(N=2),andGCR(N=1).
TherewerenoLCAstudiesontheuseofLWGRnuclearpowergenerationsystems.
Energies2016,9,863 6of13
Table1.GHGemissionsforreactor-basednuclearpowergenerationsystems.
NuclearReactor GHGEmissions
Source Type (gCO2e/kWh) EGC(MW) ηt(%) CF(%) PL(years) FEMType UOG(%) LCAType GL
MeridianCorporation[4] BWR 8.59 1000 70 30 D 0.17 Process USA
SanMartin[5] BWR 8 1000 70 30 D 0.17 Process USA
Yasukawaetal.[6] PWR 34 1000 33 75 30 D Hybrid Japan
PWR 25.7 1100 D Hybrid Japan
Yasukawaetal.[7]
PWR 7.9 1100 C Hybrid Japan
FBR 7.8 1000 33 75 30 C Hybrid Japan
Uchiyama[8] BWR 10.4 1000 32 75 30 C Hybrid Japan
BWR 21.1 1000 32 75 30 D Hybrid Japan
PWR 6 600 87 60 C Process Switzerland
Donesetal.[9]
BWR 6 1300 87 60 C Process Switzerland
HWR
3.2 600–900 31 80 40 Process Canada
Andsetaetal.[10] (bestcase)
HWR
15.41 600–900 31 80 40 Process Canada
(worstcase)
BWR
11 1000 32 70 30 C Hybrid Japan
(Purecycle)
BWR
21.6 1000 32 70 30 M-DC Hybrid Japan
Hondoetal.[11] (Purecycle)
PWR
24.7 1000 32 70 30 M-DC Hybrid Japan
(Purecycle)
BWR
26.4 1000 32 70 30 M-DC Hybrid Japan
(noPurecycle)
PWR
31.4 1000 32 70 30 M-DC Hybrid Japan
(noPurecycle)
BWR
37 1000 32 70 30 D Hybrid Japan
(Purecycle)
RashadandHammad[12] PWR 25.7 1000 75 30 D 0.2 Process
PWR 1.8 1000 33 85 40 M-DC 0.2 Process Belgium
Voorspoolsetal.[13]
PWR 4 1000 33 85 40 M-DC 0.2 I-O Belgium
WhiteandKulcinski[14] PWR 15 1000 33 75 40 C Hybrid USA
Hondo[15] BWR 24.2 1000 32.2 70 30 D Hybrid Japan
LWR 10 1000 90 60 C Process Japan
Tokimatsuetal.[16]
LWR 13 1000 90 60 M-D Process Japan
Energies2016,9,863 7of13
Table1.Cont.
NuclearReactor GHGEmissions
Source Type (gCO2e/kWh) EGC(MW) ηt(%) CF(%) PL(years) FEMType UOG(%) LCAType GL
PWR 5.19 1000 32 88.7 40 M-D Process Switzerland
PWR 5.18 1000 32 88.7 40 M-C Process Switzerland
PWR 9.8 1000 33 84.6 40 M-C Process Germany
PWR 5.95 1000 33 71.7 40 D Process France
Donesetal.[17]
PWR 7.74 1000 33 80.4 40 M-D Process Europe
BWR 11 1000 32 88.7 40 M-D Process Switzerland
BWR 10.7 1000 32 88.7 40 M-C Process Germany
BWR 7.45 1000 32 88.7 40 M-D Process Europe
Värö
LWR
EPDReport[18] 3.8 3671 34 90 50 C Process Peninsula,
(1BWR,3PWRs)
Sweden
Forsmark,
EPDReport[19] BWR 3.3 3274 34 90 50 C Process
Sweden
LWR
16 1100 85 40 D 12.7 Hybrid USA
(bestcase)
FthenakisandKim[20]
LWR
25 1100 85 40 D 0.2 Hybrid USA
(baselinecase)
LWR
55 1100 85 40 D Process USA
(worstcase)
PWR 5.91 1000 34 40 D Process Europe
NEEDSReport[21] PWR 5.58 1590 37 60 C Process Europe
FBR 4.72 1450 40 40 Process Europe
EPDReport[22] GCR 8.35 1185 35 C Process Scotland
Cantonof
EPDReport[23] PWR 3.54 730(2×365) 50 C Process Aargau,
Switzerland
Kunakemakornetal.[24] PWR 1.98 1630 37 94 60 D Process Canada
Santoyo-Castelazoetal.[25] BWR 11 1365 32.8 91 100 Process Mexico
KumariandRao[26] HWR 66 4560 100 Process India
Nianetal.[27] LWR 20.68 1000 33 70 60 Process Japan
Pereiraetal.[28] PWR 16.95 1250 70 40 Process Japan
Poinssotetal.[29] PWR 5.29 63400 20–50 C Process France
Energies2016,9,863 8of13
ETnheregieGs 2H016G, 9,e xm FOisRs PioEEnRs RwEVeIErWe found to be lower for the case representations that had8 orfe 1c3y  cled
plutonium (refer to the GHG emissions data provided by Hondo et al. [11] for LWR (BWR, PWR)
The GHG emissions were found to be lower for the case representations that had recycled 
nuclearpowergenerationsystemsinTable1). ItmayalsobenotedthattheGHGemissionsdecreased
plutonium (refer to the GHG emissions data provided by Hondo et al. [11] for LWR (BWR, PWR) 
withnauncilenacrr epaosweeirn gtehneeruartaionni usymstoemresg inra Tdaebl(er e1f)e. rItt moathy ealGsoH bGe neomteidss tihoants thdea GtaHpGro evmidisesdionbsy dFetchreeansaekdi sand
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studyre[q3u4i]rethmaetnnt ootfe hdigGhH enGeregmy iinssteionnsistiwese froer lloowweerr uforarnniuumcl eoarre pgroawdeesr. gSeimneilraart oiobnsesryvsatteiomnss wuteirleiz minagdeh igher
by another study [34] that noted GHG emissions were lower for nuclear power generation systems 
uraniumoregrades(0.1%–2%)incomparisonwiththenuclearpowergenerationsystemsoperating
utilizing higher uranium ore grades (0.1%–2%) in comparison with the nuclear power generation 
withloweruraniumoregrades(0.01%–0.02%). IntheUnitedStatesofAmerica(USA),theNuclear
systems operating with lower uranium ore grades (0.01%–0.02%). In the United States of America 
RegulatoryCommission(NRC)providesaninitialoperatinglicenseforaperiodof40yearsfornewly
(USA), the Nuclear Regulatory Commission (NRC) provides an initial operating license for a period 
builtnuclearpowerplants.Towardstheendofthenuclearplantlifetime,theowners(i.e.,thelicensees)
of 40 years for newly built nuclear power plants. Towards the end of the nuclear plant lifetime, the 
mayocwhonoersse (tio.e.g, othfeo rlicae2n0seyees)a rmeaxyt ecnhsoioosne uton gdoe rfothr ea N20R yCe’asr eesxttaebnlsiisohne duntdimere ltyhel iNceRnCs’es reesntaebwliashlepdr ocess
(coditfiimedelyin li1ce0nCseF rRenPeawratl5 p1roacnedss1 (0coCdFifRiedP ianr t105 4C)F.RT PhaerNt 5R1 Canhda 1s0g CrFaRn tPeadrto 5p4e).r Tahtien NgRliCce hnasse grreannteewd alsto
74ofotpheera1t0in0go lpiceernastei nregnreewaacltso tros 7i4n otfh teheU 1S0A0 ofpoerraatpinegr iroedacotofras dind tihtieo UnaSlA2 f0ory ae apresri[o3d5 ]o.f additional 20 
years [35]. 
3.2. StatisticalEvaluationofNuclearLCAStudies
3.2. Statistical Evaluation of Nuclear LCA Studies 
Figure1providesagraphicalrepresentationofthe(a)errorbars(mean±95%confidenceinterval
Figure 1 provides a graphical representation of the (a) error bars (mean ±95% confidence interval 
(CI)statistics)and(b)boxplots(quartiles+outlierstatistics)forGHGemissionsfromthedifferent
(CI) statistics) and (b) box plots (quartiles + outlier statistics) for GHG emissions from the different 
reactor-basednuclearpowergenerationsystemsreviewedinthisstudy. Table2providesastatistical
reactor‐based nuclear power generation systems reviewed in this study. Table 2 provides a statistical 
summaryofthelifecycleGHGemissionswithdetailsonthesamplesize(N),mean(X)±standard
summary of the lifecycle GHG emissions with details on the sample size (N), mean (X) ± standard 
deviation(SD),minimum(Min.),maximum(Max.),standarderrorofthemean(SE),quartile1(Q1),
deviation (SD), minimum (Min.), maximum (Max.), standard error of the mean (SE), quartile 1 (Q1), 
quartile2ormedian(Q2),andquartile3(Q3)forthedifferentreactor-basednuclearpowergeneration
quartile 2 or median (Q2), and quartile 3 (Q3) for the different reactor‐based nuclear power generation 
systesmysstermevsi reewvieedwiend tihni tshsistu sdtuyd.y. 

FiguFreig1u.reG 1H. GGHeGm eismsiiossniosnfsr ofrmomd idffifefreernenttn nuucclleeaarr ppoowweerr ggeennereartaiotino nsyssytesmtesm: (sa:) (ma)eamn e±a 9n5±% C95I %errCorI error
bars; and (b) quartile box plots. 
bars;and(b)quartileboxplots.
Table 2. GHG emission (gCO2e/kWh) statistics from different nuclear power generation systems. 
Table2.GHGemission(gCO e/kWh)statisticsfromdifferentnuclearpowergenerationsystems.
2
Nuclear Reactor Type N  X ± SD Min. Max. SE Q1  Q2  Q3
NuclearRBeWacRto rType N15  X1±4.5S2D ± 9.37  Min3..3  Ma3x7.  2S.E42  8Q 1 11Q  2 21.6Q 3
PWR  21  11.87 ± 10.24  1.8  34  2.24  5.18  6  15 
BWLWRR  157  14.5220.±5 ±9 1.367.71  3.33.8  3755  26..4322  108  16 11 252 1.6
PHWWRR  213  11.8728±.2 1±0 3.234.3  1.83.2  3466  129.2.242  35..21 8 15.416  66 15
LWGCRR  7 1  20.5±8.3156 .±7 01  3.88.35  585.35  6.30 2 8.3150  8.351 6 8.352 5
HWFBRR  3 2  28.26.±26 3±3 2.3.18  3.24.72  676.8  119..5242  4.372.2  6.2165 .41 7.86 6
GCR 1 8.35±0 8.35 8.35 0 8.35 8.35 8.35
FBR 2 6.26±2.18 4.72 7.8 1.54 4.72 6.26 7.8
Energies2016,9,863 9of13
From Figure 1a and Table 2, one may note that the mean lifecycle GHG emissions obtained
from the use of BWR, PWR, LWR, HWR, GCR, and FBR in nuclear power generation systems
are14.52gCO e/kWh,11.87gCO e/kWh,20.5gCO e/kWh,28.2gCO e/kWh,8.35gCO e/kWh,
2 2 2 2 2
and 6.26 gCO e/kWh, respectively. These results indicate that lower GHGs are emitted from the
2
FBR nuclear power generation systems in comparison to the widely adopted LWR (PWR/BWR)
and HWR nuclear power generation systems. This is because the FBR nuclear power generation
systems involves the recycling of plutonium (which is the bulk of long life radioactive waste)
in its entirety, while the LWR nuclear power generation systems permit only partial recycling of
plutoniumwithMOXfuelloading[22]. TherelativelyhighermeanlifecycleGHGemissionsfrom
HWRnuclearpowergenerationsystemsmaybeattributedtotheprocessofheavywaterproduction
beinghighlyenergyintensive[10,32,36]. ThehighestmeanlifecycleGHGemissioninthisstudywas
obtainedfromtheHWRs(refertoTable2). ThehighestmeanlifecycleGHGemissionfromtheHWR
reactors (28.2 gCO e/kWh) in this study was 108%, 108%, 62.7%, 33.2%, 5.7%, 3.9%, and 3.2% of
2
themeanlifecycleGHGemissionsfromhydroelectricity(26gCO e/kWh),wind(26gCO e/kWh),
2 2
biomass (45 gCO e/kWh), solar photovoltaics (85 gCO e/kWh), natural gas (499 gCO e/kWh),
2 2 2
oil (733 gCO e/kWh), and coal (888 gCO e/kWh) power generation systems, respectively [37].
2 2
From Figure 1b, one may note that the degree of variation in GHG emissions was less for FBR
nuclearpowergenerationsystems,followedbyPWR,BWR,LWR,andHWRnuclearpowergeneration
systems. Consequently,onemayinferthattheuseofFBRnuclearpowergenerationsystemsprovides
themostenvironmentally-friendlyoptionamongstthesixdifferenttypesofnuclearpowergeneration
systemsconsideredinthisstudy. NotethatthisstudyhasalimitedsamplesizeoftwoforFBRnuclear
powergenerationsystems,whichisequivalenttothetotalnumberofreal-worldFBRnuclearpower
generationsystemsassuggestedbytheWorldNuclearAssociation[1]. MoreLCAstudiesutilizing
GCRnuclearpowergenerationsystemsaretobeconsideredbeforeonegeneralizestheinfluenceof
GCRonthelifecycleGHGemissions(notethatthemeanlifecycleGHGemissionstatisticsofGCR
nuclearpowergenerationsystemsinthisstudywerebasedonasamplesizeequaltoone).
Figure2providesagraphicalrepresentationofthe(a)errorbars(mean±95%CIstatistics)and
(b)boxplots(quartiles+outlierstatistics)forGHGemissionswithrespecttodifferentfuelenrichment
methods. Table 3 provides a statistical summary of the lifecycle GHG emissions for different fuel
enrichmentmethodsassociatedwiththereviewed26nuclearLCAstudies. FromFigure2aandTable3,
onemaynotethatthemeanlifecycleGHGsassociatedwiththeuseofC,D,M-C,M-D,andM-DC
fuelenrichmentmethodsinnuclearpowergenerationsystemsare7.43gCO e/kWh,21gCO e/kWh,
2 2
8.56 gCO e/kWh, 8.87 gCO e/kWh, and 18.32 gCO e/kWh, respectively. These results clearly
2 2 2
indicate that the centrifuge fuel enrichment method is a better option than the gaseous diffusion
enrichmentmethod,consideringthatthe100%gaseousdiffusionGHGemissionsexceededthe100%
centrifugeGHGemissionsandthegaseousdiffusiondominantmixtureGHGemissionswerehigher
thanthecentrifugedominantmixtureGHGemissions. ThehigherGHGemissionsassociatedwith
gaseousdiffusionenrichmentmethodmaybeattributedtothehigherconsumptionofelectricload
incomparisonwiththeelectricityconsumptionassociatedwithcentrifugeenrichmentmethod[37].
FromFigure2b,onemayalsonotethatthedegreeofvariationinGHGemissionswaslessforcentrifuge
enrichmentmethodsincomparisonwiththecorrespondinggaseousdiffusionenrichmentmethods.
Resultantly,onemayinferthattheuseofcentrifugeenrichmentmethodinnuclearpowergeneration
systemsprovidesabetterenvironmental-friendlyoptiontowardsreducingGHGemissionsthanthe
gaseousdiffusionenrichmentmethod.
Energies2016,9,863 10of13
Energies 2016, 9, 863  10 of 13 

FigurFeig2u.reG 2H. GGHeGm eimssiisosinosnsf rforomm ddiiffffeerreenntt fufuele elnernicrhicmhemnte mntetmhoedths:o (da)s m: (eaa)n m± e95a%n C±I 9er5r%or CbaIrse;r arnodr bars;
(b) quartile box plots. 
and(b)quartileboxplots.
Table 3. GHG emission (gCO2e/kWh) statistics from different fuel enrichment methods. 
Table3.GHGemission(gCO e/kWh)statisticsfromdifferentfuelenrichmentmethods.
2
Fuel Enrichment Method  N  X ± SD  Min.  Max.  SE  Q1  Q2  Q3 
FuelEnrichmCen tMethod N14  X7.±43S ±D 3.33  Mi3n.3.  Ma1x5.  S0.E89  5Q.219  6Q.92  10Q 3
CD  1414  7.4321± ± 314.3.732  31.3.98  1555  03.8.993  5.82 9 226.6.95  25.170 
DM‐C  143  218±.561 4± .27.296  1.59.818  5150.7  31.9.731  5.818  292.8.6 5 102.75 .7
MM-C‐D  35  8.568.±87 2±. 93.61  5.51.819  10.173  11.7.319  75..4158  79.7.48  1110 .7
MM-D‐DC  56  81.887.3±2 ±3 1.12.38  5.119.8  1331.4  15.3.095  7.44 5 273..1754  26.141 
M-DC 6 18.32±12.38 1.8 31.4 5.05 4 23.15 26.4
4. Conclusions 
4. ConcluTshiios npsaper quantified the lifecycle GHG emissions from six different reactor‐based nuclear 
power generation systems (BWR, PWR, LWR, HWR, GCR, and FBR) by performing a review of 26 
ThispaperquantifiedthelifecycleGHGemissionsfromsixdifferentreactor-basednuclearpower
nuclear LCA studies (having 49 case representations) and the subsequent computation of statistical 
generationsystems(BWR,PWR,LWR,HWR,GCR,andFBR)byperformingareviewof26nuclear
metrics with development of associated graphical representations. Additionally, this study also 
LCAstudies(having49caserepresentations)andthesubsequentcomputationofstatisticalmetrics
quantified the lifecycle GHG emissions with respect to the type of fuel enrichment method. 
withdevelopmentofassociatedgraphicalrepresentations. Additionally,thisstudyalsoquantifiedthe
Lower lifecycle GHG emissions were noted for those nuclear power generation systems that 
lifecyrcelceyGcleHdG pleumtoinsisuiomn sinw coitmhpraersipsoenct ttoo tthhoeset ynpuecloeafrf upeolweenrr gicehnmeraetniotnm seytshteomd.s that did not recycle 
Lplouwtoenriulmife. cTyhcele liGfeHcyGclee mGHisGsi oenmsiswsieornes nforotmed nfuocrletahro speownuerc lgeeanrepraotiwone rsgysetnemersa tuiotinlizsiyngst elomws that
recycqleudaliptylu utroanniiuumm oinre cgormadpesa r(riseoqnuirtiongth hoigseh nenuecrlgeya rinpteonwsietyr) gweenreer haitgiohner styhastne tmhossteh nautcdleiadr npoowtreerc ycle
plutogneinuemra.tiTohne sylisfteecmycs loepGerHatGingem wiisthsi ohnigshf qroumalitnyu ucrleanariupmo woreer ggraedneesr.a tionsystemsutilizinglowquality
The mean lifecycle GHG emissions obtained from the use of BWR, PWR, LWR, HWR, GCR, and 
uraniumoregrades(requiringhighenergyintensity)werehigherthanthosenuclearpowergeneration
systeFmBsRo ipn enruactlienagr pwoiwtherh gigenheqrautaiolint ysyusrteamnisu amre o14re.5g2 rgaCdOe2se./kWh, 11.87 gCO2e/kWh, 20.5 gCO2e/kWh, 
28.2 gCO2e/kWh, 8.35 gCO2e/kWh, and 6.26 gCO2e/kWh, respectively. The FBR nuclear power 
The mean lifecycle GHG emissions obtained from the use of BWR, PWR, LWR, HWR,
generation systems proved to be the most environmentally‐friendly option (with minimal GHG 
GCR, and FBR in nuclear power generation systems are 14.52 gCO e/kWh, 11.87 gCO e/kWh,
emissions  and  minimal quartile  variation)  amongst  the  six  different2  types  of  nuclear po2wer 
20.5 gCO e/kWh, 28.2 gCO e/kWh, 8.35 gCO e/kWh, and 6.26 gCO e/kWh, respectively.
genera2tion systems considere2d in this study. This stu2dy captured the variation in2 the performance of 
TheFFBBRR nnuucclleeaarr ppoowweerr ggeenneerartaiotino nsyssytesmtesm isn pitrso venetdiretotyb, ecotnhseidmeroinstg etnhvati rtohnem saemntpallel ys-ifzrei efnodr lFyBoRp tion
(withnmucilneaimr paolwGeHr gGeneemraitsiosnio snysstaenmd LmCAin simtudalieqs ureavriteilweevda irni athtiios ns)tuadmy oanndg sttheth teotsailx nudmiffbeerre onft FtByRp es of
nuclenaurcpleoawr peorwgeern geernaetrioatniosny ssytestmemssc oopnesriadteinregd ini nthteh riesasl‐twudoryl.dT ahreis bsottuh deqyuciavpalteunrte tdo ttwheo.v Tahreia htiigohnlyi nthe
perfoernmeargnyc einotefnFsBivRe nhueacvleya wrpatoewr perrogdeuncetiroant ipornocseyssst ecomnstriinbuittesde ncotinrseitdye,rcaobnlys itdoewrainrdgst hhiagthtehre lisfeacmycpllee  size
GHG emissions from HWR nuclear power generation systems. 
forFBRnuclearpowergenerationsystemLCAstudiesreviewedinthisstudyandthetotalnumber
The mean lifecycle GHGs associated with the use of C, D, M‐C, M‐D, and M‐DC fuel enrichment 
of FBR nuclear power generation systems operating in the real-world are both equivalent to two.
methods from nuclear power generation systems reviewed in this study are 7.43 gCO2e/kWh, 21 
Thehighlyenergyintensiveheavywaterproductionprocesscontributedconsiderablytowardshigher
lifecy cleGHGemissionsfromHWRnuclearpowergenerationsystems.
ThemeanlifecycleGHGsassociatedwiththeuseofC,D,M-C,M-D,andM-DCfuelenrichment
methods from nuclear power generation systems reviewed in this study are 7.43 gCO e/kWh,
2