24P10524P105-P
Economic Analysis of Tokamak and Spherical Tokamak
Advanced Fuel Fusion Reactors
トカマク型及び球状トカマク型先進燃料核融合炉の経済性評価
Takuya Kondo, Kozo Yamazaki, Tetsutarou Oishi, Hideki Arimoto, Tatsuo Shoji
近藤拓也, 山﨑耕造, 大石鉄太郎, 有本英樹, 庄司多津男
Department of Energy Engineering and Science, Nagoya University,Furo-cho, Chikusa-ku, Nagoya 464-8603 ,Japan
名古屋大学 〒464-8603 名古屋市千種区不老町D-3He fusion reactor has very low neutron wall load and D-D fusion reactor has abundant fuel resources,
compared with D-T reactor. Not only engineering issues but also economic assessments are important inorder to achieve these advanced fuel fusion reactors as commercial plants. We calculated and compared
COEs of D-T, D-3He and catalyzed D-D fusion reactors. The assessment results show that D-3He and D-Dreactors require high beta confinement system and high plasma temperature, in order to obtain COE ofthese reactors as low as that of D-T reactor.

1. Introduction
D-T fusion reactor would be the first commercial
reactor, because D-T reaction has relatively highreaction rate at low plasma temperature. However,about 80 percents of the power of the D-T reactor isfrom 14.1MeV neutrons. These neutrons activate
the reactor wall, and the D-T reactor needs
replacement of wall and other components every
few years. In addition, the D-T reactor needs
radioactive substance (tritium) breeding and storage
system. Then, D-3He and D-D reactions areexpected as next-generation advanced fusion
reactions; because D-3He reaction generates noneutron and D-D reaction has abundant fuelresource. To achieve a commercial fusion reactor,,
it is important to check economics of these reactorsas well as technical issues to be resolved. In thisstudy, we estimate the costs of D-T and advanced
fuel fusion plants and compared with each other.

2. Analysis Procedures
We calculate cost of electricity (COE) of fusion
reactors using PEC (Physics-Engineering-Cost)
system code [1]. PEC code calculates plasma
parameters and engineering designs of fusion
reactors to satisfy target output electric power andignition margin.
3. Reactor model
We estimate three types of fuel cycle, D-T,
D-3He and catalyzed D-D, and two types ofconfinement system; Tokamak Reactor (TR) andSpherical Tokamak reactor (ST). Combining them,
we estimate five types of reactor system, TR D-T,
TR D-3He, TR cat D-D, ST D-T and ST D-3He. Thecat D-D reactor system recycles T and 3He
produced by D-D reaction, and extracts energy of
D-T and D-3He reaction.
Blanket model is Flibe/FS like FFHR [2] andD-3He is assumed no blanket system like ARIES-3

Table I. Reference cases of reactors
Confinement system
Fuel cycle
Net electric power Penet (GW)
Normalized beta βNa
Aspect ratio Aa
Maximum field Bmax (T)aCentral ion temperature Ti (0) (KeV)a

D-T
1.00
4
3.53
13
30

TRD-3He
1.00
8
3.53
1370

cat D-D
1.00
8
3.53
13
70

D-T
1.00
8
1.62
8.75
30

Plasma major radius Rp (m)Toroidal field Bt (T)Fusion power (GW)
Neutron power (GW)Power density (MW/m3)
Neutron wall load (MW/m2)

6.40
6.15
3.49
2.79
4.66
3.62

8.57
7.81
2.74
0.07
1.52
0.05

9.05
7.60
2.83
1.33
1.34
0.88

4.00
2.34
4.71
3.76
3.22
5.08

STD-3He
1.00
8
1.62
13706.63
3.30
2.67
0.06
0.40
0.03
aInput parameters

[3]. Features of ST are low aspect ratio and no innerblanket. The coil of ST D-T reactor is assumed
normal conducting for central post coil, but the coilof ST D-3He is assumed super-conducting.
We fixed the following input parameters; target
net electric power is 1000MW, plant availability is75%, operating period is 30 year and target ignition
margin is 1.01. Reference cases of reactors areshown Table.I.

Decon.&decom.
Fuel
Replacement

Operations
Capital cost

TR D-T
β N=4

TR D-3Heβ N =8TR cat D-D
β N=8ST D-T

4. Results
Dependence of COE on normalized beta value(βN) is shown in Fig.1. High βN improves plasma
confinement performance; as a result, required
plasma volume decreases. Therefore, the size of areactor becomes small and COE falls. D-3He andcat D-D have a lower output power density, andrequire larger plasma volume, compared with D-T
plasma volume.
D-3He and cat D-D reactors need high βN andhigh ion temperature (=70keV) in order to obtain
almost same COE of TR D-T (at βN=4~5). However,conventional Tokamak system seems to be difficult
to achieve high βN value (>5). Because ST can havehigh βN, ST is expected to be a confinement system
suitable for D-3He and cat D-D reactors.
Figure 2 shows COE breakdown of reference
cases. Since D-3He and cat D-D requires large
plasma major radius Rp, the cost concerning
construction becomes large and, the capital cost
becomes large. Because of neutron damage to thefirst walls, D-T reactor requires frequent
replacement of blanket within plant lifetime. Incontrast, D-3He reactor has very low neutron wallload, and no need to replace blanket. Thereby,D-3He reactor has almost no replacement cost. Cat
D-D has relatively low neutron wall load; therefore,
2018TR D-T
TR D-3He
TR catD-D
ST D-TST D-3He

TR D- 3 He

COE[cent/kWh]1614

TR cat D-D

12ST D-T

108TR D-T
ST D- 3 He

6468
βN10Fig.1 Dependence of COE on βN

12β N=8ST D- 3He
β N=8024681012COE[cent/kWh]
Fig.2 COE breakdown of reference cases

replacement cost is assumed as 1/3 of thereplacement costs of D-T. In addition, D-3He andcat D-D reactor can omit tritium breeding system.
However, 3He gas is very precious resource on theearth. In this study, we assumed that the scenario
taken out 3He from the moon's surface [4], and it
was calculated by 200$/g.
Assuming high ion temperature (=70keV) andhigh βN (>7), COE of advanced fuel fusion reactors
are expected to be similar to that of D-T reactor.
References[1] K.Yamazaki, and T. J. Dolan: Fus. Eng. Des. 81(2006) 1145.
[2] A.Sagara, O. Motojima, et al.: Fus. Eng. Des. 29(1995) 51.
[3] F.Najmabadi, R.W.Conn, et al, “The ARIES- Ⅲ
Tokamak Fusion Reactor Study – The final report,”
UCLA report UCLA – PPG-1384, (1992).
[4] L.J. Wittenberg, E.N. Cameron, et al.: Fusion Tech.
21 (1991) 2230.