Supercritical rankine cycle A synopsis of the cycle, it’s background, potential applications and engineering challenges.

Shane Hough04/07/09(ME-517)

Supercritical rankine cycle A synopsis of the cycle, it’s background, potential applications and engineering challenges.

Shane Hough04/07/09(ME-517)

Abstract

TheRankinecyclehasbeenusingwatertogenerateusefulworksincethemid1800’s.Withtheadventofmodernsuper alloys,theRankinesteamcyclehasprogressedintothesupercriticalregionofthecoolantandisgeneratingthermalefficienciesintothemid40%range.Asof2001,therewere360supercriticalfossilfuelplantsoperatingacrosstheglobe[10].Theseplantsareoperatingattemperaturesaround1000oFandpressuresaround3500psia.TwoofthecurrentengineeringchallengesaretoadaptthesupercriticalRankinecycletocoolantsotherthanwater,andtodesignnuclearpowerplantscapableofoperatingatsupercriticaltemperaturesandpressures.Thereismuchworktobedoneintheareaofmaterialdevelopmentbeforenuclearplantswillbecapableofreliableoperationatthetemperaturesandpressuresrequiredtoachievethermalefficienciesover35%.

TableofContents

Introduction:TheSimpleRankineCycle 1

SimpleCycle 1 Figure1.SimpleRankine/SteamCycleDiagram. 1 Figure2.SimpleRankineCycleT-SDiagram. 1 Superheat 1 Figure3.SimpleRankineCyclewithSuperheatT-SDiagram. 1 Efficiency 2 MeasuredParameters 2 Figure4.EffectofTurbineOutletBackpressureforaConstantInputThrottle

Temperature. 2 Figure5.EffectofTurbineInletTemperatureforaConstantOutletBackpressure 3

SupercriticalRankineCycle 3

EfficiEncy� 3� � figurE�6.���SupErcritical�rankinE�cyclE.� 3� DEfinition� 3� MatErial�concErnS 4

NuclearLightWaterPowerApplication 4

SuperCriticalWater-cooledReactor(SCWR) 4 Differencebetweenconventionalnuclearplantdesigns 4 Table1:SCWRPressureVesselSpecifications 4 Materialstresstesting 4 Figure7.SCWRpowerconversioncycleschematic 5 Figure8.SCWR,PWR,&BWRcomparison 5 Figure9.StressCorrosionCracking(SCC)photos 6

NaturalGasProductionwithaSupercriticalGeothermalPowerApplicationBy-product 7

NaturalGasBrine 7 PropaneCycle 7 Design 7 Efficiency 7 Viability 7 Figure10.SupercriticalPropaneCycleSchematic 8

SupercriticalCO2PowerApplication 8

CO2criticalvalues 8

SCWRcomparison 8 Smallercomponents 8 Operationalparameters 8 Materialconcerns 8 Figure11.SupercriticalCO

2RecompressionCycle 9

Table2:CalculatedSystemParameterscorrespondingtoFigure11 9 Figure12.SizeComparisonbetweenTurbinesofVariousCycles/Coolants 9

Conclusion 10

Efficiencyimprovements 10 Materialimprovements 10 Reliability(60yrs) 10 PlantSize 10 Large(1600MW

e) 10

Mid(20MWe) 10

Small(400kWe) 10

EconomicConsideration 10

References 11

- 1 -

Introduction:TheSimpleRankineCycle

TheRankine cycle is synonymouswith the steamcycle and is the oldest functional heat cycle utilized byman.AbasicdiagramofthecycleisillustratedinFigure1.Figure 2 represents the Temperature - Entropy (T-S)diagramforthesimplestversionoftheRankinecyclewhichcorrespondstosystemswithworkingpressuresupto400psia[1].ThecycleasitisdepictedinFigure2israrelyusedtoday. More commonly, the simple Rankine cycle ismodified such that the steam is superheated prior toenteringtheturbine.Thisisindicatedbyline3-4intheT-SdiagramshowninFigure3.Whenproperlydesigned,thismodificationincreasesW(theworkcapacityofthesystem)withoutsignificantincreasetoQr(theunavailableheatofthe system). Typically, point 4 represents temperaturesup to approximately 900 oF (755 K). Theoretically, it should be possible to superheat the steam to thesametemperatureastheheatsource;whichinaboiler,isontheorderof3500oF(2200K).However,thetemperaturethatcorrespondstopoint4isphysicallylimitedtoadifferentialtemperatureofabout1000oF(811K),themetallurgicallimit[2].Inotherwords,solongastheheattransferacrossthematerialsintheboilerandtheturbinesmaintainsatemperaturedifferentiallessthantheoperationallimitsofthematerial,itshouldnotexperiencecatastrophicfailure.Additionally,superheatingallowsthesteamtostillremainapproximately90%(orgreater)dry as it exhausts from the turbine. This featureof the superheated cycle simplifies theturbinedesignandextendsturbinelifeduetoreducedwearfromwaterimpingementontheblades.

Heat Sink

Heat Source

Qa

Qr

Engine(Turbine)

Superheater

Pump

Boiler

Condenser

1

5 6

1

2

2

343

45

Figure 1. Simple Rankine/Steam Cycle Black numbers correspond to Figure 2; Grey numbers correspond to Figure 3.

T

0 S

1

2 3

45

W = Q - Q

Qr

a r

Figure 2. T-S Diagram, Simple Rankine Cycle.

T

0 S

1

6

2 3

4

5

W = Q - Q

Qr

a r

Figure 3. T-S Diagram, Simple Rankine Cycle with Superheat.

- � -

Theefficiency(η)ofthiscyclecanberepresentedbytheratioofworkcapacitydividedbytheheatputintothesystem(Qa):

η =WQa

ηsimple =h3 − h1 − h4 + h5

h3 − h1

ηsuperheat =h4 − h1 − h5 + h6

h4 − h1

ηsupercritical =h2 − h1 − h3 + h4

h2 − h1

Equation1.

Intermsofenthalpy(h),theefficiencyfortheRankinecyclewithandwithoutsuperheatingcanbedefinedbythefollowingequationsrespectively:

η =WQa

ηsimple =h3 − h1 − h4 + h5

h3 − h1

ηsuperheat =h4 − h1 − h5 + h6

h4 − h1

ηsupercritical =h2 − h1 − h3 + h4

h2 − h1

Equation2.

η =WQa

ηsimple =h3 − h1 − h4 + h5

h3 − h1

ηsuperheat =h4 − h1 − h5 + h6

h4 − h1

ηsupercritical =h2 − h1 − h3 + h4

h2 − h1

Equation3.

Typicalefficienciesforthesecyclesrangefromaround20%-35%. Therearetwomeasurablephysicalandcovariantparametersofthesystemwhichcorrelatetosubstantialaffectsonthethermalefficiencyofthecycle.Thefirstparameteristhesystembackpressure.Foragiveninlet(throttle)temperatureandpressureattheturbine,alowerbackpressureequatestoahighersystemefficiency.Ineffect,anincreaseinthebackpressurereducesthecapacityofthesteamtoexpandthroughtheturbine.TheeffectofvariationsinsystembackpressurecanbeseeninFigure4.Thesecondparameteristhethrottletemperature.Whileholdingboththesystembackpressureandthethrottlepressureconstant,anincreaseinthethrottletemperaturewillincreasethethermalefficiencyofthecycle.ThiseffectisshowninFigure5.Anincreaseinthethrottletemperaturesimplyincreasesthepotentialoftheexpandingsteamtotransferenergytotheturbine.

50

45

40

35

30

30

25

2520

20151051014.7312.289.827.374.912.460.490

Throttle Temperature = 810.93 K (1000 F)

Ran

kine

Ste

am C

ycle

Ther

mal

Eff

icie

ncy

, Pe

rcen

t

Thro

ttle

Pre

ssure

, psi

a

Engine Back Pressure, In. Hg abs (psia)

50003200

1500

2500

1000

500

200

10,000

o

Figure 4. Effect of Turbine Outlet Backpressure for a Constant Input Throttle Temperature [1].

- � -

SupercriticalRankineCycle

TheRankinecyclecanbegreatlyimprovedbyoperatinginthesupercriticalregionofthecoolant.MostmodernfossilfuelplantsemploythesupercriticalRankineSteamCyclewhichpushesthethermalefficiencyoftheplant(seeequation4)intothelowtomid40%range.

η =WQa

ηsimple =h3 − h1 − h4 + h5

h3 − h1

ηsuperheat =h4 − h1 − h5 + h6

h4 − h1

ηsupercritical =h2 − h1 − h3 + h4

h2 − h1 Equation4.

For water, this cycle corresponds to pressures above 3,206.2 psia and temperatures above 705.4 oF(646.3 K) [1]. The T-S diagram for a supercritical cycle canbe seen inFigure6. With theuseof reheat and regenerationtechniques,point3 inFigure6,whichcorresponds to theT-Svaporstateofthecoolantafterithasexpandedthroughaturbine,canbepushedtotherightsuchthatthecoolantremainsinthegasphase†.Thissimplifiesthesystembyeliminatingtheneedforsteamseparators,dryers,andturbinesspeciallydesignedforlowqualitysteam.†Traditionally, a Rankine cycle operates across a phase change and a Brayton cycle operates

entirely in the gas phase. However, as improvements in material make higher temperatures

and pressures available, the difference between a supercritical Rankine cycle and a Brayton

cycle blur. For the purpose of this paper, a supercritical Rankine cycle is one which has

evolved from a simple Rankine cycle or one for which it is desirable to run along the

gas/vapor boundary (dimer and trimer formation only) to maximize heat extraction from

the coolant.

T

0 S

1

4

2

3

Qr

W = Q - Qa r

Figure 6. Supercritical Rankine Cycle.

Ran

kine

Ste

am C

ycle

Ther

mal

Effic

iency

, Pe

rcen

t

Thro

ttle

Pre

ssure

, psi

a

Back pressure = 0.5 In. Hg abs (0.0246 psia)

14.7

50

100

200

500

100015002500

3206.2

500010,000

Dry

Satu

rate

dV

apor

atTh

ro

ttle

54

52

50

48

46

44

42

40

38

36

34

32

30

Throttle Temperature, K ( F)o

400 600 800 1000 1200 1400 1600422 533 644 755 866 977 1088

Figure 5. Effect of Turbine Inlet Temperature for a Constant Outlet Backpressure [1].

- 4 -

Theprimaryconcernwiththiscycle,atleastforwater,isthemateriallimitsoftheprimaryandsupportequipment.Thematerialsinaboilercanbeexposedtotemperaturesabovetheirlimit,withinreason,solongastherateofheattransfertothecoolantissufficientto“cool”thematerialbelowitsgivenlimit.Thesameholdstruefortheturbinematerials.Withtheadventofmodernmaterials,i.e.superalloysandceramics,notonlyarethephysicallimitsofthematerialsbeingpushedtoextremes,butthesystemsarefunctioningmuchcloser to their limits. Thecurrent superalloysandcoatingsareallowing turbine inlet temperaturesofupto1290oF(973K)[3]andfourthgenerationsuperalloyswithRutheniummono-crystalstructurespromiseturbineinlettemperaturesupto2010oF(1370K)[4]inthefuture.

NuclearLightWaterPowerApplication

TheGenerationIVSuperCriticalWater-cooledReactor(SCWR)isa1600MWenuclearpowerplantdesignbasedonthe supercriticalRankinecycle. Thesystem layout is identical to the supercritical systemcurrentlyusedinfossilfuelsplantsexcepttheboilerisreplacedwithanuclearreactor.ThesystemdiagramcanbeseeninFigure7,page5.ConventionalnuclearplantsoperateonthesimpleRankinecyclewithsuperheatingand exhibit thermal efficiencies on the order of 33%. The SCWR is capable of a thermal efficiency of44.8%[5].Oneoftheattractiveaspectsofasupercriticalcycleforanuclearapplicationisthatiteliminatestheneedforpressurizers,primarytosecondaryheatexchangers,steamdryers,andsteamgenerators.Whenoneconsidersthattheprimarycostofelectricityforanuclearplantistheconstructioncost,eliminationofsupportequipmentiscrucial,especiallyifitoffsetsthecostofheavierpressurevesselsandsupportpiping. The primary differences between the SCWR and conventional Boiling Water Reactors (BWR) &PressurizedWater Reactors (PWR) is the reactor outlet temperature is 930 oF (770 K) instead of 570 oF(570 K) and the SCWR operates at approximately 3625 psia [5] as compared to 915 psia and 2265 psiarespectively[6].ThisdifferenceisgraphicallyrepresentedinFigure8,page5. Inorder tohandle thehigherpressuresand temperatures, the reactor vessel must be designedto handle the extreme temperatures and pressures. Thespecifications required to meet this demand are listed inTable1.Moreimportantthanthepressurevesselhowever,arethefuelassembliesandcontrolrodcomponents.Withareactorinlettemperatureof535oF(550K),thereactorcomponents are exposed to a temperature differential of395oF(220K).Unlikethetubesinaboiler,asignificantportion of the fuel assembly structure is not directlytransferring heat to the fluid. This places much greaterstress on those components and consequently, Phillip E.MacDonaldperformedafirstorderstress testonmanyofthecommonmaterialsused for theseassemblies. Of theaustenetic(304L&316L)andNickle(Alloy600,625,690,

Parameter Value

Material SA-533orSA-508Grade3,Class1

DesignPressure

27.5MPa(3990psig)110%ofnominalrating

OperatingTemperature

535oF(553K)

InsideShellDiameter

5.322m(209.5in)

ShellThickness

0.457m(18in)

HeadThickness

0.305m(12in)

VesselWeight

1.7millionlbs

Table 1: SCWR Pressure Vessel Specifications [5]

- 5 -

Reactor

Figure 7. Schematic of the SCWR power conversion cycle (HPT = high pressure turbine, LPT = low pressure turbine, FWH = feedwater heater) [5].

- 4 -

2175

3625

T (°F)

P (psig)

536 545

SCWR

BWR

1015

CriticalPoint

3206

L

SV

608 705 932

PWR

Figure 8. SCWR, PWR, & BWR operating conditions on the phase diagram of water [7].

- � -

(a)

(b)

(c)

Figure 9. Cross sections of the 304L stainless steel SCC sample tested in deaerated supercritical water at (a) 750 °F, (b) 930 °F, and (c) 1020 °F

[5].

- 7 -

&718)basedalloyswhichweretestedinthepressure/temperatureenvironmentpresentinanSCWR,allweresusceptibletoStressCorrosionCracking(SCC),thoughAlloy316LandAlloy690weresufficientlyresistanttowarrantfurtherstudy[5].ExamplesofSCCin304Lstainlesssteelcanbeseenonpage6inFigure9.Oftheferritic-martensitic(HT-9,T-91,&HCM12A)alloystested,manyexhibitedresistancetoSCCbuthadoxidationratesoneorderofmagnitudemorethantheausteneticalloys[5].Thismakestheferritic-martensiticmaterialsillsuitedforthinassemblycomponents.TheseissuesprovideasubstantialengineeringobstacletobeovercomebeforetheSCWRcanbeconsideredaviablenuclearpowerplantdesign.Additionally,noneofthematerialtestingtodatehasbeenperformedineitherahighneutronorhighgammafluxtocharacterizeactualmaterialperformanceinanoperatingreactorvessel.

NaturalGasProductionwithaSupercriticalGeothermalPowerApplicationBy-product

Inmanycases,thesourceforNaturalGasproductionisageothermallyheatedbrine.Inthesecases,thebrinetemperaturesrangefrom240oF(390K)upto360oF(455K)dependinglinearlyuponwelldepth[8].Inthistemperaturerange,thebrinepassesthroughaheatexchangertofeedasupercriticalRankinecycleforPropane,whichhasacriticaltemperatureof206oF(370K)andacriticalpressureof616psia.Theoretically,the brine may be able to run the cycle directly but there are too many contaminants and compositionalvariationsforthistobefeasible.Ifapowercyclelikethiswereemployed,thesitesproducingNaturalGascouldpotentiallygeneratepowerforGriduseor,ataminimum,generatethemajorityoftheplant’selectricalrequirements.IntheUnitedStates,thereareseveralareasalongtheTexasandtheLouisianaGulfCoastwherethistypeofpowercycleisfeasible[8]. Thebenefittothiscycle isthat it isextremelysimpleintermsofsystemcomponents. Thesystemrequires only a single phase heat exchanger, a turbine, an air cooled condenser, and a pump. Figure 10,page 8, depicts a basic system diagram. The nominal operating pressure of this system is approximately1000psia,which suggests thatallof the supportpipingandequipment is commerciallyavailable. Givena 15 Million BTU/hr brine source, this system could generate approximately 400 kW net power with athermalefficiencyof9%[8]. Additionally,thesystemcanbebuilttobeselfregulatingbyusingthepowergridasadynamicbrakefortheturbine-generatorset[8].Ineffect,thisactsasaspeedcontrolfortheturbineduringslightvariationsinsystemdemandundernormaloperatingconditions. Additionalcontrolscanbeimplementedtoautomatethesystembasedonbrinetemperatureandflowrates,allofwhichminimizetheneedtohaveafull-timeoperator,thusreducingoperationalcosts. Despite the downside of a poor thermal efficiency of only 9%, this system is still a viable sourceof energy. Currently,productionplants aredumping theavailableheat to theatmosphere. Thequestionbecomesoneofeconomics;atacostofapproximately$2,131/KW[8](1982dollars≈$5,488todayadjustedfor inflation),will a9%returnpay itselfbackover the lifeof thewell. At today’spriceswithanaverageelectricitycostof$0.11perkWhr,itwouldtakeapproximately6yearstorecoverthecostofthepowerplant.Sinceapowerplantofthissizecanbebuiltonamobileplatform,evenifanindividualwelldoesnotlast6years,thepowerplantcanbemovedtoanewlocationandreused.Basedontheplatformbeingreusable,thisisapotentiallyviablepowerplantdesigndespitethelowthermalefficiencyof9%.

- � -

SupercriticalCO2PowerApplication

ThesupercriticalCO2cycleisonewhichisarguablyaBraytoncycleratherthanaRankinecycle.CO2hasacriticalpressureofapproximately1057psiaandacriticaltemperatureofapproximately88oF(305K).Becausethecriticaltemperatureisachievableduringnormaloperatingconditions,itisfeasibletorunalongthegas/vaporboundarybetween the turbineoutlet and the compressor inlet; thus allowing the system tomaximizetheworkthatcanbeextractedfromthecoolant.Forthisreason,thesupercriticalCO2cyclewillbeconsideredinthispaper.AbasicsystemdiagramisshowninFigure11,page9,andcorrespondingsystemtemperaturesandpressuresintable2,page9. OneoftheGenerationIVnuclearplantdesignsisasupercriticalCO2cycle.ThisdesignoperatesatsimilartemperatureandpressureastheSCWR.Theoutlettemperatureisapproximately1020oF(820K)andtheexitpressureis2900psia[9].Thethermalefficiencyofthiscycleisabout45%butduetotheenhancedheattransferpropertiesofCO2,thecomponentscanbemadesmallerandtherebyreducecomponentcostsbyupto18%comparedtoconventionalBWRandPWRplants[9].Alsoofinterest,thedensityofCO2increasesand compressibilitydecreases substantially as it approaches the critical point. Thispropertyboth reducestheworkrequiredtobeperformedbythecompressorandreducesthefootprintofthephysicalcomponent,thusimprovingefficiencyandcomponentcost.AnexampleoftheconceptualsizedifferencecanbeseeninFigure12,page9. Additionally,thissystemhasreactorinlettemperaturesofapproximately745oF(670K),whichleadstotemperaturedifferentialsofabout275oF(410K)[9].WhiletheconditionsinthesupercriticalCO2cyclearenotasextremeasthoseintheSCWR,theyaresufficienttowarrantextensiveSCCtests,especiallywhereCO2ispotentiallymorecorrosivethanwateratthenominaloperatingtemperatures.

Brine

Turbine

Pump Accumulator

Air CooledCondenser

Primary HeatExchanger

Figure 10. Supercritical Propane Cycle Fed by Geothermally Heated Natural Gas Brine.

- 9 -

Steam turbine: 55 stages / 250 MWMitsubishi Heavy Industries Ltd, Japan (with casing)

Helium turbine: 17 stages / 333 MW (167 MWe)X.L.Yan, L.M. Lidsky (MIT) (without casing)

Supercritical CO2 turbine: 4 stages / 450 MW (300 MWe)(without casing)

5 m

Compressors are of comparable size

Figure 12. Size Comparison between Turbines of Various Cycles/Coolants [9].

LOWTEMPERATURERECUPERATOR

FLOWMERGE

TURBINE

HIGHTEMPERATURERECUPERATOR

SPLIT

MAIN

PRECOOLER

FLOW

COMPRESSOR

REACTOR2 4

6

7

8 6

8

RECOMPRESSING

188

COMPRESSOR

3

35

3

Figure 11. Supercritical CO2 Recompression Cycle [9].

Point Pressure(psia)

TemperatureoF

1 1101 89.62 2864 142.03 2862 316.44 2858 745.85 2839 1022.06 1131 824.57 1119 335.08 1103 157.3

Table 2: Calculated System Parameters corresponding to Figure 11 [9].

- 10 -

Conclusion

The supercritical Rankine cycle, in general, offers an additional 30% relative improvement in thethermalefficiencyascomparedtothesamesystemoperatinginthesubcriticalregion. Thecyclehasbeensuccessfullyutilizedinfossilfuelplantsbutthecurrentavailablematerialsprohibitreliableapplicationofthesupercriticalcycletonuclearapplications.Thereismuchworktobedoneinordertoadvancematerialstothepointwheretheywillbeabletoreliablywithstandthestressesofasupercriticalenvironmentinsideanuclearreactorforadesignedlifespanofapproximately60years. Whilemanyofthematerialadvancesareduetotheadventofspecializedcoatings,itisreasonabletosuspectthatnewadvancescouldalsobemadebyimprovementsintheisotopicqualityofthebasemetals.Ithasbeenknownfordecadesthat isotopicallypurematerialshaveconsiderablybetterthermalconductivity.Improvementsinisotopicpuritycanaffectheattransfercharacteristicsbyuptoafactorofthree[11],possiblymore. It should be noted however, the cost of obtaining sufficient quantities of such materials may beprohibitiveandthebenefitgainedistemperaturedependant. OneotherconsiderationforasupercriticalRankinecycleisthesizeoftheplant.Forlargeplantsontheorderofa1600MWethethermalefficienciesareinthe40%region.Bythetimethepowerplantsarereducedtothe20MWerange,thermalefficienciesaredownintothelowtomid20%region[7].Asindicatedbythegeothermalpropaneapplication,whenaplantisinthe400kWeregion,thethermalefficiencyisloweryet.Forthepropanecycle,itwas9%;byextrapolation,asupercriticalsteamcyclewouldbe≈19%efficientwere it applicable. The issue for smaller systems is the cost effectiveness. A supercritical cycle is simplerandreducestheamountofequipmentrequiredtooperatethecyclebutbecauseitoperatesatmuchhigherpressuresandtemperaturesthecostoftheequipmentwhichisrequired,goesupconsiderably.Smallsystemsmayhaveimprovedthermalefficiencybutmaynotbethemostcosteffectivesolutions;forthisreasontheyshouldbeconsideredskepticallybeforebeingimplemented.Justbecauseasystemcanbemademoreefficientdoesnotmeanitisthebestallocationofmoney,ormaterialresources.

- 11 -

References

[1] G.A.Skrotzki(1963).BasicThermodynamics:ElementsofEnergySystems.NewYork:McGrawHillBookCompany,382-420.

[2] Sears,F.,andG.Salinger(1975).Thermodynamics,KineticTheory,andStatisticalThermodynamics.3rded.,Reading:Addison-WesleyPublishingCompany,354-362.

[3] Yang,G.,Paxton,D.,Weil,S.,Stevenson,J.,andSingh,P.,(2002).“MaterialPropertiesDatabaseforSelectionofHigh-TemperatureAlloysandConceptsofAlloyDesignforSOFCApplications.”PNNL-14116.

[4] Wikipedia.(2009,March28).Superalloy:http://en.wikipedia.org/wiki/Superalloy

[5] P.E.MacDonald(2005).“FeasibilityStudyofSupercriticalLightWaterCooledReactorsforElectricPowerProduction,NuclearEnergyResearchInitiativeProject2001-001,WestinghouseCo.GrantNumber:DE-FG07-02SF22533,FinalReport.”INEEL/EXT-04-02530.

[6] Lamarsh,J.,andA.Baratta(2001).IntroductiontoNuclearEngineering.3rded.,UpperSaddleRiver:PrenticeHall,203-205.

[7] Middleton,B.,andJ.Buongiorno(2007).“SupercriticalWaterReactorCycleforMediumPowerApplications.”LM-06K146.

[8] F.L.Goldsberry(1982).“VariablepressuresupercriticalRankinecycleforintegratednaturalgasandpowerproductionfromthegeopressuredgeothermalresource.”NVO-240:OSTIID5348110.

[9] V.Dostal(2004).“ASupercriticalCarbonDioxideCycleforNextGenerationNuclearReactors.”MIT-ANP-TR-100.

[10] Voss,S.,andG.Gould(2001).“TheRankineCycle:WorkhorseoftheCoal-firedUtilityIndustry.”TechBriefs,Burns&McDonnell,(No.3),4-6.

[11] Kittel,Charles(1996).IntroductiontoSolidStatePhysics.7thed.,NewYork:JohnWiley&Sons,Inc.,138.