Energy analysis and carbon dioxide emission of Tokamak fusion power reactors

Fusion Engineering and Design 48 (2000) 483–498

Energy analysis and carbon dioxide emission of Tokamakfusion power reactors

Koji Tokimatsu a,*,1, Hiroki Hondo b, Yuichi Ogawa a, Kunihiko Okano b,Kenji Yamaji a, Makoto Katsurai a

a School of Engineering, Katsurai-lab Building No 10, The Uni6ersity of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, Japanb Central Research Institute of Electric Power Industry, Tokyo, Japan

Abstract

Energy gain and carbon dioxide (CO2) emission of tokamak fusion power reactors are evaluated in this studycompared with other reactor types, structural materials, and other Japanese energy sources currently in use. Thereactors treated in this study are (1) a conventional physics performance international thermonuclear experimentalreactor (ITER), like a reactor based upon the ITER engineering design activity (ITER-EDA), (2) a RS (reversedshear) reactor using the reversed shear safety-factor/plasma current profile, and (3) a ST (spherical torus) reactorbased upon the final version of the advanced reactor innovative engineering study ST (ARIES-ST). The input energyand CO2 emission from these reactors are calculated by multiplying the weight or cost of the fusion reactorcomponents by the energy intensity and/or with the CO2 intensity data, which are updated as often as possible. TheITER cost estimation is estimated based on the component unit costs. The following results were obtained: (1) TheRS and the ST reactor can double the energy gain and reduce CO2 emission by one-half compared with the ITER-likereactor. (2) Silicon carbide (SiC) used as the structural material of inner vessel components is best for energy gain andCO2 emission reduction. (3) The ITER-like reactor is slightly superior to a photovoltaic (PV) with regard to CO2

emission. (4) The energy gain and CO2 emission intensity of the RS reactor and the ST reactor are as excellent asthose of a fission reactor and a hydro-powered generator. These results indicate that a tokamak fusion power reactorcan be one of the most effective power-generating technologies both in high-energy payback gains and reduction ofCO2. © 2000 Published by Elsevier Science S.A. All rights reserved.

Keywords: Energy gain; CO2 emission; ITER-like reactor; RS reactor; ST reactor; Structural materials

www.elsevier.com/locate/fusengdes

* Corresponding author. Present address: Research Institute of Innovative Technology for the Earth, 7th floor, No. 3 ToyokaijiBldg, 2-23-1, Nishi-shimbashi, Minato-ku, Tokyo 105-0003, Japan. Tel.: +81-3-34371699; fax: +81-3-38164996.

E-mail address: [email protected] (K. Tokimatsu).1 This work is based upon his Ph.D thesis, the University of Tokyo, 1998.

0920-3796/00/$ - see front matter © 2000 Published by Elsevier Science S.A. All rights reserved.

PII: S0920-3796(00)00157-5

K. Tokimatsu et al. / Fusion Engineering and Design 48 (2000) 483–498484

1. Introduction

The status of tokamak fusion research anddevelopment (R&D) has reached a point whereinnot only the physics or engineering of the reactorsis important, but also matters of economy, energygain, environmental impact, and safety come intoplay. All of these characteristics must be consid-ered if tokamak reactors are to be used in asocially responsible fashion as a commercial en-ergy source. Fusion energy is expected to be oneof the important future energy technologies in there-construction of the ‘New Earth Plan’ [1] advo-cated by the Japanese Ministry of InternationalTrade and Industry (MITI).

In this study, we used our physics/engineer-inglcost systems code [2] to evaluate componentvolumes and weights. We then analyzed energygains (calculated as the ratio between input andoutput energies) and CO2 emission, taking intoconsideration the scheduled replacement compo-nents within the plant’s lifetime from constructionto decommission. The aim of this study is toassess fusion as an energy source in light ofenergy gain and CO2 emission and to comparefusion reactors.

2. Reactor parameters used in this study

The reactor parameters treated in this study arelisted in Table 1. They are (i) the experimentalreactor ITER, and the power rectors (ii) theITER-like power reactor (iii) the reversed shear(RS) power reactor [3], which has parameterssimilar to those of the CREST (Compact RE-versed Shear Tokamak) power reactor [4], and

(iv) the spherical tokamak (ST) power reactor [5].In assessing the ST reactor, we used the plasmaparameters and the volume data of the final ver-sion of the advanced reactor innovative engineer-ing study ST (ARIES-ST) power reactor [5].

To compare reactors, we used the characteris-tics of 1000 MW of electric output power at busbar Pe, 75% of plant availability, and 30 years ofplant lifetime for all reactor types. For the ITER-like reactor and the RS reactor the fusion poweris from 3 to 4 GW with a thermal to electricityconversion efficiency of 34.5% using water as acoolant. Ferrite steel is assumed/applied to thestructural material of the ITER-like, the RS, andthe ST power reactors. A shield blanket for theITER and a breeding blanket for the ITER-like,the RS, and the ST power reactors are assumed.Weight fractions of structural materials, tritiumbreeder lithium oxide (Li2O), and neutron multi-plier beryllium (Be) in the breeding blanket are setas described in Table 2 for each replacementblanket and permanent blanket, as referenced inthe technical description of the steady state toka-mak reactor (SSTR) [6]. Material, volumetric den-sity, volumetric fraction of reactor componentsare set in Table 3, which are based upon technicaldescription of the ITER-TAC4 report [7]. Detailproperties (volume, applied materials, etc.) of theARIES-ST reactor, which are described by Miller[5], are used as much as possible in the calculationof input energy and CO2 emission of the STreactor.

Energy gain and CO2 emission of the ITER-likereactor and the RS reactor are also evaluatedwhen structural materials, i.e. Ferrite steel, Vana-dium-alloy, and SiC/SiC (silicon carbide com-posite), are changed. Cases (Fe1.0) (V1.5) (V1.0)(SiC1.5) (SiC1.0) are compared in Table 1. Thosereactor parameters, including plasma physics, en-ergy flow, toloidal field (TF) coil shape, and cost,are calculated using a zero-dimensional systemscode [2]. In the design identification code (XY),X=Fe, V, SiC means structural materials, Y=1.0, and 1.5 means Pe (unit: GW). The symbol(Fe1.0) corresponds to ‘Ferrite steel, electric busbar 1.0 GW’, which is used in comparing theITER with the ST reactor. This is the base casefusion power close to 3 GW. Thermal to water

Table 2Weight fraction of structure, Li2O, and Be of replacement/per-manent blanketsa

Structure BeLi2O

0.1Replacement 0.12 0.20Permanent 0.380.1

0.2 0.20.5Total

a These values are assumed from ref. [6].

K. Tokimatsu et al. / Fusion Engineering and Design 48 (2000) 483–498 485

Tab

le1

Des

ign

para

met

ers

inth

isst

udy

Com

pari

son

ofre

acto

rty

pes

Com

pari

son

ofst

ruct

ural

mat

eria

ls

STIT

ER

-lik

eR

SIT

ER

ITE

R-l

ike

RS

(V1.

0)(S

iC1.

5)(S

iC1.

0)(V

1.5)

(V1.

0)(S

iC1.

5)(S

iC1.

0)(F

e1.0

)(F

e1.0

)(V

1.5)

VSi

Cc

VV

VF

eSi

CSt

ruct

ural

mat

eria

lSi

CV

bF

eF

eaSU

SW

ater

He

He

He

He

He

He

He

He

Wat

erW

ater

Coo

lant

He

Con

vers

ion

effic

ienc

y(%

)46

.534

.546

.546

.546

.546

.546

.546

.534

.534

.545

.046

.58.

558.

959.

055.

15.

655.

688.

45.

658.

43.

25.

1P

lasm

am

ajor

radi

um(m

)8.

42.

912.

912.

912.

912.

913.

04.

03.

04.

02.

913.

01.

6A

spec

tra

tio

1.6

1.8

1.8

2.0

2.0

2.0

Elo

ngat

ion

2.0

1.6

1.8

2.0

3.75

1.8

0.24

0.24

0.24

0.5

0.5

0.5

0.24

0.5

0.24

0.24

Tri

angu

lari

ty0.

670.

5

12.5

12.5

12.5

12.5

12.5

13.0

16.0

13.0

16.0

12.5

13.0

Tor

oida

lfie

ldon

TF

coil

(T)

7.43

7.38

2.7

2.7

2.7

2.7

4.95

4.0

4.95

4.5

Tor

oyon

coef

fcie

nt2.

72.

24.

95

1.63

91.

374

1.73

82.

289

1.42

42.

831

H-f

acto

r2.

196

−2.

62.

289

1.42

4

10.5

2020

2020

1515

1515

2015

Pla

sma

tem

pera

ture

(keV

)16

3.0

2.75

3.5

3.75

4.34

Safe

tyfa

ctor

on95

%3.

253.

04.

343.

03.

7510

.9d

3.0

23.8

29.4

23.5

15.5

10.8

917

.127

.610

.521

.0P

lasm

acu

rren

t(M

A)

28.4

15.5

27.6

0.28

90.

273

0.28

90.

289

0.93

50.

910.

935

0.91

0.28

90.

935

0.95

8B

oots

trap

curr

ent

frac

tion

200.

927

2.5

Cur

rent

driv

epo

wer

(MW

)17

5.3

7023

.527

.524

.6–

25.3

263.

123

.528

.426

3.1

1.68

2.09

41.

334

4.28

74.

23.

462.

371

3.47

4.28

72.

371

4.10

2N

eutr

onw

all

load

(MW

/m2)

1.5

1500

4034

2749

4079

2662

2879

2160

2885

2150

4034

2879

Fus

ion

pow

er(M

W)

2979

3218

4756

Tot

alth

erm

alpo

wer

(MW

)31

0232

3924

3132

4624

2146

9932

3933

7346

99

1000

1571

1000

1389

1000

1000

1390

1000

1000

1564

Ele

ctro

nic

outp

utpo

wer

(MW

)–

1000

aF

erri

test

eel.

bV

anad

ium

allo

y.c

Silic

onca

rbid

e.d

On

edge

.


Table 3Volumetric fraction, volumetric density of componentsa

ItemsComponents Materials Volumetric density (t m−3) Volumetric fraction

Nb3SnSC coil 5.1Winding 0.368Can SUS etc. 16.4 0.632

SUSBlanket 8.0Structure 0.61Ferritic steel 8.0 0.2Vanadium alloy 6.1Silicon carbide 3.2BreederLi2O 2.02 0.5

Multiplier Beryllium 1.87 0.2

Shield Structure SUS 8.0 1Ferritic steel 8.0Vanadium alloy 6.1Silicon carbide 3.2

SUSDivertor 8.0Structure 0.928Ferritic steel 8.0Vanadium alloy 6.1Silicon carbide 3.2

Cu-alloy Copper 8.96 0.0464Be brush Beryllium 1.87 0.0258

AluminumVacuum vessel 2.3Structure 1.0

a Volumetric fractions are assumed from refs. [5–7].

Table 4Thickness of the each component assumed in this study

Materials Inner components (m) Outer components (m)

Gap Shield BlanketBlanket Gap Shield

SiC 0.20.56 0.85 0.67 0.4 1.590.0 0.65 0.6 0.0 1.220.5Others

conversion efficiency is 34.5%, and ferrite steel isused as a structural material.

The (V1.5) case corresponds to ‘vanadium-al-loy, electric bus bar 1.5 GW’, which is appliedHe-cooling and vanadium-alloy with no changefrom the (Fe1.0) reactor parameters except incooling and structural material. The electric busbar is increased up to 1.5 GW because thermal toelectrical conversion efficiency increased to 45%with fusion power still being at about 3 GW. Inthe (V1.0) case, He-cooling and Vanadium alloy isalso applied as in the (V1.5) case, while Pe, isadjusted to 1 GW (fusion power 2.8 GW) bychanging the minor radius without changing the

aspect ratio. In the ITER-like case, the plasmashape bears almost no change; however, a highaspect ratio (aspect ratio A=4.0) and a highmagnetic field (16 Tesla on the TF coils) areapplied to the RS case such as the ARIES-RSreactor.

The same concept is applied to the (SiC1.0) and(SiC1.5) cases. The inner/outer blanket gap andshield thickness are increased in comparison tothose of other structural materials. The thicknessof these materials is described in Table 4, whichare derived from ref. [6] and The Senior Commit-tee on Environmental, Safety, and Econoniic As-pects of Magnetic Fusion Energy (ESECOM)study [8].


Fig. 1. Energy analysis and CO2 emission anaysis flow.

mining, refining, manufacturing, and disposal,and the transportation connecting these four pro-cesses. All the materials and energy have to beconsidered for each process. We used the bottom-up method, which sums up all the energies usedfor fuel and materials. Fuel energies include fuelmining, refining, manufacturing, and transport-ing. Material energies include mineral mining,material refining, materiallcomponent manufac-turing/transport, and component construction/building.

Energy gain is defined as the ratio of outputlin-put energy. Although output energy is electricity,it is considered secondary energy (i.e. electric en-ergy); however, both primary energy (i.e. thermalenergy) and secondary energy are included ininput energy. In this study, all the input energy isregarded as primary energy, and energy gain iscalculated as secondary energy. A 2250 kcalkWh−1 conversion efficiency is used [9], which isbased on Japanese electrical generatorsexperience.

3. Evaluation method

3.1. Background of this study

As shown in Fig. 1, there are two streams, fueland material, which compose the input of anenergy plant. These two streams are involved in

Table 5Inclusion and method of input energy for fuel and materialsa

MaterialsFuel

Inclusion MethodProcess Process Inclusion Method

Mining andNoMining Norefining ofminerals

Energy intensity or CO2Yes Material YesManufacturing Emission intensity or CO2

emission intensity×fuel emission intensity weight orconsumption cost

Manfacturing20% of manufacturing CostYes YesRefiningTransport Construction 20% of material andYes

transportation manufacturingYes Deuterium: 0.3 kg day−1 Replacement Yes Blanket/current drive:Consumption

considering neutron wall loadand neutron fluence

Tritium: self-sufficient is Yesreplacement Divertor: replacement of everyyearassumedAll the others: one time ofwhole replacement withinplant life time

a A total of 20% of (material and) manufacturing 11 method and replacement methods except blanket, current drive, and divertorin this table are referred from ref. [9]


3.2. Premises for energy analysis in this study

Input energies with regard to fuel and materi-als, inclusions, and methods are summarized inTable 5. In this study, we considered reactorconstruction, replacement within lifetime, and fuelconsumption. Waste disposal storage, the timespan of which can be as long as 100 years, is notconsidered. Deuterium is assumed to be obtainedfrom nitrogen and hydrogen by an ammonia–hy-drogen dual temperature exchange process in am-monia plants. Therefore, for fuel, only themanufacturing energy is considered, i.e. no con-sideration is given to mining. Because of thedifficulty of evaluating energy for fuel refinementand transportation, this energy is assumed to be20% of fuel refinement energy, as in ref. [9].Self-sufficient initial tritium and deuterium con-sumption (about 0.3 kg per day for the 1-GWreactor) are assumed. Energy intensity for deu-terium is based upon [10], and the energy intensityof tritium is assumed to be the same as that ofdeuterium.

Regarding material flow, the energy needed forraw mineral mining and refining cannot be con-sidered because of a lack of existing data. Wecalculated the energy necessary for manufacturingmaterials (material energy) from raw material viaintermediate material to final material by multi-plying weight by energy intensity. We evaluatedthe energy necessary for manufacturing (manufac-turing energy) from final material to componentbased on the manufacturing cost [7]. The energynecessary for construction and transportation isassumed to be 20% of the sum of material energyand manufacturing energy.

The input energy needed for one blanket re-placement, the current drive (CD), and the diver-tor equals the input energy for a replacementblanket plus 25% of the total input energy for acurrent drive plus the input energy of a divertor.All the other energies except replacement energyare assumed to be wholly replaced within 30 yearsof reactor operation in order to compare themwith other plants’ energy gains [9] using the samestandard.

3.3. Data for material energy

The input energy per unit cost and weights forcalculating material energy are listed in Table 6.Energy intensities for superconductor strands,stainless steel (SUS), ferrite steel, and copper al-loy, all of which are used for superconductorcoils, blanket shields, and divertors, are derivedfrom data contained in a report describing theenergy analysis of a Super-GM (a motor-genera-tor using a superconductor) [11]. These data areappropriate because (1) the data used in ref. [11]are detailed enough to be analytically reliable, (2)components of the super-GM resemble reactorcomponents, and (3) the data are relatively recent.Input energy for Li2O, which is used for theblanket, is evaluated using the latest data of Liextraction from sea water (10 000 kWh for 1 tonLi2CO3) [12]. The energy intensity of titan in ref.[13] is applied for vanadium-alloy. The energyintensity data for Be and SiC are derived from ref.[10].

In the evaluation of heat transportation (HeatTrans), the reactor building (R.B.), and the bal-ance of plant (B.O.P.), the sum of whose compo-nents is impossible to calculate in detail, weconsidered the amount of materials and electricalequipment. Unalloyed steel, which is used in thereactor plant equipment in ref. [14] (2086 tons), isincluded in the R.B. High-alloyed steel in thereactor is not included, since we classified it ashaving already been included in the reactor com-ponents. For the B.O.P., both unalloyed steelsand high alloyed steels for ‘structure+site facili-ties’, turbine plant equipment, and misc. plantequipment (total amount=43 656 tons) are con-sidered. In addition to the steel, concrete(Japanese fission experience=983 390 tons) iscounted as a part of the B.O.P. The energy inten-sities of blister steel and concrete described in ref.[15] are applied to these types of steel andconcrete.

Evaluation of the necessary amount of materialfee needed for the CD is very difficult because nodetailed information exists regarding the materialand its amount in the neutral beam injector (NBI)of the ITER, SSTR, or other reactor designs. Theonly weight data we could obtain about the NBI


Table 6Energy intensity and CO2 emission intensity of each componenta

Materials applied forItems Energy CO2 emissionMaterials for reactorsthis study intenstityb intesityc

Superconductior coils Nb3Sn strand NbTi strandsf 49.2 30.7SUS316 (Fe66, Ni22, SUS alloy(C) 7.535.2Cr18, Mn2, Mo2) (Fe31.2, Ni33,

Cr30.7)f

7.5Structural materialsBlanket shield SUS316 SUS alloy 35.2divertor vacuumvessel

Ferrite (HT-9) (Fe87, Fe–Ni–Cr alloy 82.3 8.7Cr8, W1) (Fe86.5, Ni9, Cr3)f

Vanadium (V3Cr3Ti) Ti64g 299 83.7(V90, C6, M5)SiC (Si50, C50) SiCh 50 14.0

CU99, CrIfCu-alloy 9.2 3.2Li20/Breeder Li2, 01i 21.2 9.68

Beh 860 240.8Be/multiplierAluminumjAluminum 22.97 7.55

Unalloyed steels Blister steeljReactor building 4.68 1.41(2086 ton)

Electrical equipmentj 1112dElectrical equipment 344.3e

High alloyed steelsBalance of plant Blister steel 4.68 1.41(43656 ton)Concrete (983390 Concretej 0.15 0.11ton)

Heat trans Electrical equipment Electrical equipment 1112d 344.3d

SUS etc.Current drive electric computerj 85.2 21.3

a Energy intensity of superconductor strands, SUS, and Ferrite steel are referred from ref. [11], Vanadium, SiC, and Be arereferred from [10,13], the others are referred from ref. [15]; CO2 emission intensities are calculated following by Table 9 or referredfrom [15].

b Unit, Gcal per t-material.c Unit, t-CO2 per t-material.d Unit, Gcal M$−1.e Unit, t-CO2 m$−1.f Ref. [11].g Ref. [13].h Ref. [10].i Ref. [12].j Ref. [15].

are those of components for the NBI device (0.5MeV, 10 MW) in the JT-60U of the JapanAtomic Energy Research Institute (JAERI) [16].

Because a 2-MeV NBI applied to the SSTR isassumed in our study, we tried to develop acorrespondence between the NBI components inthe JT-60U and those in the SSTR. Table 7 showsthe weight of the NBI components of the SSTR asestimated from the volume and weight of the NBIcomponents of the JT-60U [6]. Based upon this

correspondence, we assumed the following values:5 MW output per ion source tank, based on ref.[6,16], eight ion sources per beam line, based onref. [6], and one vending tube, one beam dump+ion neutralizer cell, a NBI port, and a measuringsystem. We formulated a relation between CDpower and weight by using these assumptionsregarding components.

We had no data describing materials used in theNBI or input energy data for manufacturing the


NBI. An evaluation seems insufficient if the inputenergy for the NBI is based only on the energy forSUS. We therefore used the second-highest energyintensity data described in ref. [15] for the NBI(85.2 Gcal ton−1 of an electric computer). Electricequipment for the electric power station, whichcorresponds to transformer equipment and trans-mission equipment in ref. [15], is also included inenergy cost and the costs for Heat Trans, CD,R.B., and B.O.P.

The cost of the CD is a product of heatingpower and unit heating cost. The cost of HeatTrans, R.B., and B.O.P. is a product of standardcost and scaling factor. The scaling factors arescaled from standard thermal power or standardfusion island (FI) volume. The thermal power is

the total thermal power gained from the fusionreactor, which is converted into electricity at theturbines. The FI volume is the sum of the volumesof the reactor components. Cost calculation meth-ods of CD, Heat Trans, R.B., and B.O.P. arelisted in Table 8. The unit cost of heating power isset at 4.6 $ W−1 [17], taken from the SSTR. Thestandard costs of heat trans, R.B., and B.O.P. aredecided by re-categorizing the ITER-interlim de-sign report (IDR) [18] cost items following theGeneromak model [19]. Detailed items of R.B.and B.O.P. are listed in Table 9. Costs of the mainreactor building, vacuum systems, coil power sup-ply, cryostat (all of which are in the ITER-MR)are included in the standard cost of the R.B. Thestandard cost of the B.O.P. includes some costs

Table 7Weight assumption of SSTR NBI components from those of JT-60U

JT-60U SSTR

Specification (m) Weight (ton) ComponentsComponents Specification (m) Multiply Weight (ton)

×2.597.4 250�f3×6 Ion source tank f3×15Ion source tank

25 ×2.5 15059.3−10 �Neutralizer cell Bending tube

Ion dump tank ×4.5� 28062.2 Beamf4×3.5 f7×9dump+neutralizer

NBI port 5.5(×2.5)NBI port�2.2

Measurement�30 (×2.5)Measurement 75

Table 8Cost calculation formulas and contents of current drive, heat trans, reactor building, and balance of plant

Items ITER Formulas Contents

Current drive 388 calculated by 4.6$ W−1 Current drive and its power supply etc.

Heat transportation and heat tank etc.Heat trans 264 264·� Pth

4699

�0.6a

Main reactor building, vacuum system, coil power supply, cryostatReactor building 1834 1834 ·� VFI

5553

�0.67a

etc.

Landb, buildingsb, fuel and waste treatment, instrumentation andBalance of plant 872 2189 ·

� Pth

4699

�0.6a

control, liquid/gas distribution, turbineb, machine assembling,remote handling, other reactor plant equipmentb, etc.

a Unit; M$, VFI, Pth means volume of fusion island and thermal power of fusion reaction, respectively.b Not included in ITER.


Table 9Standard cost breakdown of reactor building and balance ofplant

ReferenceItems Costa

Reactor building1014Main building ITERb

69ITERVacuum systemscoil power ITER 386

81ITERCryostat22Thermal shield ITER

262ITERCryoplant/cryodistribution

Balance of plantLand 5.6dGen.c

Buildings (except main Gen./ITER 529d

building)79ITERWaste treatment

Fuel handling32Fueling ITERrrERTritium plant 72

Instrumentation and controls63CODAC ITERITERInterlocks and alarms 2.3

0.6ITERPoloidal controlITERDiagnostics 168

4.6Radwaste monitoring ITERGas/liquid distribution

ITERLiquid distribution 64Gas distribution 23ITER

4.6Sampling ITERGen.Turbine plant and main heat 366d

rejectMachine assembly,

equipmentMachine assembly and tools 92ITERRemote handling equip. ITER 239

ITERGeneral test equip. 28111dGen.Spare parts allowance

Gen.Electrical plant equip. 171d

Other reactor equip. 74dGen.60dGen.Miscellaneous equip.

a Unit: ‘93 US W.b ITERADR.c Generomak.d Not included in IMR.

and general test equipment. The costs from theGeneromak model are the land, buildings (ex-cept the main building), turbines, and otherequipment, including the electrical plant. Thecost of buildings in the B.O.P. is calculated bymultiplying the cost of the main building (aggre-gated in the ITER-IDR report) by a fractionderived from the costs of the main building re-lated to the other buildings in the Generomakmodel. Since the standard costs of the Genero-mak model and those of the ITER-IDR reflectthe dollar values of ‘83 and’89, respectively,these standard costs are adjusted to US ‘93$ asin the ITER-TAC4, derived from the ImplicitPrice Deflator (IPD) in the ARIES SystemsCode (ASC) [20]. The standard thermal powerand the FI volume, whose values are 4699 MWand 5553m3 respectively, as described in Table8, are those of the ITER-like reactor.

3.4. CO2 emission

The premises for evaluating CO2 emission arethe same as that of the energy analysis shown inTable 5. In order to calculate the CO2 emissionfrom a component, all the energies such as theoil, gas, and electricity input into the componenthave to be known. CO2 emission resulting fromeach kind of input energy is calculated by multi-plying the input energy quantity by the CO2

emission intensity, and the emissions from allcomponents are then totaled. Table 10 showsthe quantities and CO2 emission intensities of allthe input energies of the various components.Total CO2 emission intensities of the compo-nents treated in Table 10 can be calculated bysumming all the products of input energy andCO2 emission intensity. The CO2 emission inten-sity data for electrical equipment, blister steel,concrete, and electrical computers in Table 10are derived from the I/O method described inref. [15]. The CO2 emission intensities of specialmaterials such as Vanadium-alloy, SiC, and Beare products of each energy intensity with 0.28t-CO2/Gcal, which is a ratio of total energy con-sumption to total CO2 emission in Japan in1990 [15].

from the ITER-MR and the others from theGeneromak model.

The categories from the ITER-IDR are thefollowing: cost of waste treatment, fuel han-dling, instrumentation and controls, gas/liquiddistribution, machine assembly, remote handling,


Table 10CO2 emission intensity of energy sources and energy consumption of each componenta1

Energy consumption for each componentEnergy

CO2 Emission Copper alloy DeuteriumNbTi strandsUnit of items SUS alloyItems Ferrite alloyintensity (gCO2 per unitenergy)

2358.6Volatile oils Litre 0.02528.3 1.5 5.8Litre 4.2Lamp oils 1.92644.3 0.3 3.1Light oils 0.7Litre 0.4

Litre 2697.7 38.7A type heavy 1.6 3.8 1.8oils

Litre 2885.6 6.2 34.1 0.9B type heavy 124.2oils

C type heavy Litre 2885.6 126.2 257.2 93.6 161.0 11 350 00oils

Litre 3162.5Hydro-carbon 0.0oils

2795.0 132.9 133.5Coals 45.1kg 169.5Oil coke kg 3307.4 6708.0 8.6

kgCoalcoke 3247.2 31.0 382.5 615.7 46.73006.6 5.5 145.9kg 6.2LPG 67.1

809.6 27.5Coke gas 78.9m3

2041.9 600.0m3 634.0Butane gasm3Natural gas 2026.2 1.5 4.3

2141.0 0.0 0.3m3 0.8Refined gasm3Fireplace gas 877.1 124.5 356.9

Electricity K Wh−1 392.3 19200 8000 11700 3006.1 2 260 000

a CO2 emission intensities are referred from ref. [15]. Energy consumption breakdown is referred from ref. [10,11].

4. Results

4.1. Reactor comparison

Breakdowns of energy consumption and CO2

emission are shown in Figs. 2 and 3, respectively.Breakdowns of the bar graphs are, from the bot-tom, (1) coils and their support structure, (2)blanket/shield/divertor, (3) current drive (CD), (4)heat transportation (heat trans), (5) reactor build-ing (R.B.), (6) balance of plant (B.O.P.), (7) re-placement (blanket, inboard shield for ST,divertor, CD, and center post for ST from thebottom) and (8) fuel.

The characteristics of energy intensities andCO2 emission of tokamak fusion reactors are asfollows. Results show that fraction of fuel can beneglected. The fraction of input energy and CO2

emission due to initial construction/installation,

corresponding to all the breakdowns except fueland replacement, approaches 70–80%, while in-put energy and CO2 emission due to operationequals 20–30%. Input energy and CO2 emissionfor the reactor components (coils/structure+blanket/shield/divertor) of the ITER-like reactoroccupy about 50% of the initial installation frac-tion, while all the other components (R.B. andB.O.P.) are 50% of the total. The RS and the STreactor cases correspond to 20–30% for reactorcomponents and 70–80% for R.B. and B.O.P.These figures indicate that energy consumptionand CO2 emissions of the RS reactor and the STreactor are less than half the amounts of theITER-like reactor. These reactors have highphysics performance, which results in compactreactors. The ST reactor can reduce input energyand CO2 emission, compared with the RS reactor,20 and 10%, respectively. The reasons that the STreactor can reduce both input energy and CO2


Fig. 2. Comparison of the input energy for the ITER-like, the RS, and the ST reactors. Following two things are characteristic forthese tokamak reactors; the input energy for fuel can be neglected, the input energy related for the RS reactor and the ST reactoris less than half that of the ITER-like reactor. The total input energy for the ST reactor is slightly lesser than for the RS reactor.

Fig. 3. Comparison of the CO2 emission for the ITER-like, the RS, and the ST reactors. The same tendency can be seen as thatobserved in the case of the input energy.

emission are that (1) ferrite steel is used for struc-tural materials, and (2) aluminum, not supercon-ductors, is used for the TF coil. Both the RS

reactor and the ST reactor can be prominentmodels for future fusion R&D if both reactorscan attain the 75% plant availability.


4.2. Structural material comparisons

Input energy and CO2 emission of the ITER-like and the RS reactor are evaluated in the caseswhere the structural materials are changed fromferrite steel to vanadium alloy and SiC. Resultsfor the ITER-like reactors are shown by unitelectricity (or electric power) in Figs. 4 and 5, theRS reactors in Figs. 6 and 7. Figs. 4 and 6correspond to energy gain, Figs. 5 and 7 toCO2intensity. Breakdowns are the same of thoseof Section 4.1. Scale merit affects those cases(V1.5) and (SiC1.5) where electric power is largerthan the other Pe=1.0 cases.

In comparing (Fe1.0) (V1.0) (SiC1.0), input en-ergy and CO2 emission are greater as SiCBFeBvanadium, while used volume for the fusionreactor components increases in the reactor casesmade from Fe, vanadium, SiC structural materi-als, in this order. There are two reasons for SiC’ssuperior result: (1) component weights with SiCare light because of the lightness of the volumetric

density, even though the volume of the reactorcomponents is greater than that with other mate-rials, and (2) both input energy and CO2 emissionare small because the energy intensity and CO2

emission intensity (in terms of unit weight) arealso small. Moreover, an anonymous refereepointed out that the energy requirement for vana-dium alloy, compared with that for titaniumwhich is applied instead of vanadium in thisstudy, is greater by more than a factor of 8 thanthat of titanium. Such an issue cannot be verifiedby our investigation; however, this point does notchange the result.

In the SiC reactor case, energy gain increasesslightly and CO2 emission intensity (in terms ofunit electric power at a bus bar) decreases slightlyin comparison with a ferrite reactor. The tendencyof the structural material difference is almostidentical to that of the RS reactor. However, thevolume of superconductor coils increases with themodification to the ARIES-RS type, which resultsin an increased CO2 emission intensity in the caseof (SiC 1.0).

Fig. 4. Comparison of the input energy for the structural material variations of ferrite steel, vanadium allowy, and SiC of theITER-like reactor. The energy gain is increased in the order of vanadiumB ferriteBSiC. Although the component volumes of theSiC case are larger than the others, the energy intensity for SiC is smaller than other structural materials.


Fig. 5. Comparison of the CO2 emission for the structural material variations of ferrite steel, vanadium alloy and SiC of theITER-like reactor. The same tendency can be seen as that observed in the case of the input energy.

Fig. 6. Comparison of the input energy for the structural material variations of ferrite steel, vanadium alloy, and SiC of the RSreactor.


Fig. 7. Comparison of the CO2 emission for the structural material variations of ferrite steel, vanadium alloy, and SiC of the RSreactor.

4.3. Comparisons with other energy sources

Energy gain and CO2 emission are comparedwith other energy sources in Table 11. The data,except that of fusion reactors, come from ref.[9,21]. We adopted the once-through method forthe fuel cycle and the gas diffusion method ofuranium condensation for the fission reactor inthis table. We assumed 1 GW of electric powerand 75% plant availability for the fission reactorsand the coal-fired power plants, 10 MW of electricpower and 45% plant availability for the hydro-powered generator plant, and 3 kW of electricpower and 15% availability for a house-use PV.

Manufacturing energy is not included in thefusion energy gain results because this manufac-turing energy is not included in any of the otherenergy sources in Table 11. Therefore, the valuesof fusion reactors are different from those shownin Figs. 2–7. The energy gain of the ITER-likereactor exceeds that of the coalfired power plantand PV; however it is below of that of fission. Theenergy gain of the RS and the ST reactors exceeds

that of fission. Therefore, energy gain of the RSreactor and the ST reactor are excellent amongmodem power plants. CO2 emission intensity(CO2 emission per unit of electricity) exceedsslightly that of a PV in the case of the ITER-likereactor. Moreover, both the RS reactor and theST reactor are close to a hydro-powered genera-tor or a fission reactor in terms of CO2 emissionintensity. Therefore, it can be concluded thattokamak fusion power reactors are ‘clean’ interms Of CO2 emission.

5. Summaries

We conducted a quantitative analysis compar-ing (1) reactor types, (2) structural materials, and(3) other energy sources in light of energy analysisand CO2 emission. In comparing reactor types,both the RS reactor and the ST reactor cansuccessfully double their properties over those ofthe ITER-like reactor in that CO2 emission perunit of electricity can be reduced by half, while


Tab

le11

Com

pari

son

ofen

ergy

gain

and

CO

2em

issi

onw

ith

othe

rpo

wer

plan

tsa

1

Coa

lfir

edW

ater

pow

ered

Pho

to-v

otai

c(f

ora

Fis

sion

(onc

eF

usio

nho

use

use)

thro

ugh)

STR

S(F

e1.0

)IT

ER

-lik

e(F

e1.0

)

1000

1621

1000

100.

003

1117

1518

Tot

alou

tput

elec

tric

pow

er(M

W)

3.4

7.4

0.25

010

.5R

e-ci

rcul

atio

now

erfr

acti

on38

.39.

975

0.00

392

696

610

00E

lect

ric

pow

erat

bus

bar

(MW

)10

0010

0075

7545

1575

75P

lant

avai

labi

lity

50E

nerg

yga

in9

1428

3224

17 990

17.6

58.7

20.9

22.5

22.2

46.5

CO

2em

issi

onin

tens

ity

[g-C

O2

k−1

Wh−

1

aE

nerg

yga

inan

dC

O2

emis

sion

ofth

eIT

ER

-lik

ere

acto

rar

esl

ight

lysu

peri

orto

thos

eof

PV

.E

nerg

yga

inan

dC

O2

emis

sion

ofth

eR

Sre

acto

ran

dth

eST

reac

tor

are

asde

sira

ble

asth

ose

ofa

fissi

onre

acto

r(o

nce-

thro

ugh,

gas

diff

usio

nty

pe)

ora

hydr

o-po

wer

edge

nera

tion

.All

the

data

exce

ptfu

sion

are

deri

ved

from

ref.

[9]


energy gain can be doubled. By further reducingcomponent volume using innovative plasmaphysics and by using both ferrite steel and normalconductor for the TF coils, the ST reactor canreduce input energy by 10% and CO2 emission by20% compared with the RS reactor.

SiC is the best structural material, while vana-dium is the worst, for obtaining high energy gainand low CO2 emission intensity. We must pointout, however, that further detailed investigation isneeded to obtain base data on the various struc-tural materials.

In our comparison of energy sources, we foundthat the energy gain and CO2 emission of theITER-like reactor are slightly superior to those ofa PV. Therefore, tokamak fusion power reactors,can be considered at least as ‘clean’ an energysource as a PV. Moreover, energy gain and CO2

emission of the RS reactor and the ST reactor arefavorably comparable to those of a fission reactor(once-through, gas diffusion type) or a hydropow-ered generator. In conclusion, tokamak fusionpower plants are both ‘high-energy payback’ and‘low CO2 emission’ energy sources amongpresently available Japanese power sources.

Acknowledgements

The authors give grateful appreciation to DrRonald L. Miller, who informed us of the detaileddesign parameters of the ARIES-ST, and also tothe anonymous referee who provided fruitfulcomments and discussions.

References

[1] MITI, Vision of global environment, Research Instituteof Industrial Trade and Industry, 1997, (in Japanese).

[2] T. Yoshida et al., Development of cost assessment code offusion power reactors, T94001, Kornae Research Labora-tory, Central Research Institute of Electric Power Indus-try (1994), (in Japanese) Hatayama, A. et al., FusionTechnol., 26 (1994) 27.

[3] K. Tokimatsu, K. Okano, et al., Study of design parame-ters for minimizing the cost of electricity of tokamakfusion power reactors, Nucl. Fusion 38 (1998) 885.

[4] K. Okano et al., Compact reversed shear tokamak reactorwith a super-heated steam cycle, IAEA-CN-69/FTP11,Proc. of 17 th IAEA Fusion Energy Conference, Yoko-hama, October, 1998.

[5] R.L. Miller, private communication (http://aries.ucsd.edu/�miller/AST272a/output.html), 1999.

[6] Reactor Design Laboratory, Concept study of the steadystate tokamak reactor (SSTR), JAERI-memo 03-058,1991, (in Japanese).

[7] Detail of the ITER Outline Design Report (The ITER-TAC4 report), San Diego Joint Work Site, (1994).

[8] L.P. Holdren, Exploring the competitive potential ofmagnetic fusion energy: the interaction of economics withsafety and environmental characteristics, Fusion Technol.13 (1988) 7.

[9] Y. Uchiyama, Life cycle assessment of power generationsystems, Y94009, Socio-Economic Research Center, Cen-tral Research Institute of Electric Power Industry, 1994(in Japanese).

[10] Y. Kozaki, Analysis for realization of fusion reactors,The Institute for Future Technology, 1978, unpublished(in Japanese).

[11] Science and Technology Agency, Assessment for super-conductor technique of resources and energy, 1987 (inJapanese).

[12] K. Ohi, private communication.[13] Y. Shimazu, Fusion reactors SYSTEM ASSESSMENT

MANUAL, energy special study (fusion), speciallyfunded from Ministry of Education (Monbu-shou), 1986,unpublished (in Japanese).

[14] R. Bunde, The potential net energy gain from DT fusionpower plants, Nucl. Eng. Des./Fusion 3 (1985) 1.

[15] H. Hondo, Energy requirements and CO2 emissions in theproduction of goods and services: application of an input-output table to life cycle analysis, Y95013, Socio-Eco-nomic Research Center, Central Research Institute ofElectric Power Industry, 1996 (in Japanese).

[16] NBI Facility Division, Design study of a negative-ionbased NBI system for JT-60U, JAERI-M 94-072, 1994 (inJapanese).

[17] T. Yoshida, private communication.[18] Technical Basis For The ITER Interim Design Report

(The ITER-1DR report), San Diego Joint Work Site,1995.

[19] L. Sheffield et al., Cost assessment of a generic magneticfusion reactoe, Fusion Technol. 9 (1986) 199.

[20] R. Miller, private communication.[21] Agency of Natural Resources and Energy, Natural re-

sources and energy data book 199T, Denryoku shinpo-sya, 1997 (in Japanese).

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Energy analysis and carbon dioxide emission of Tokamak fusion power reactors

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