24P102-P
Study of DEMO Using the Structural Design of ITER
ITERの構造設計を用いた原型炉の検討
Koji Hosokawa, Akira Furuya, Yuichi Ogawa and Kunihiko Okano,
細川康二, 古谷 晃，小川雄一, 岡野邦彦
The Graduate School of Frontier Science, the University of Tokyo
5-1-5, Kashiwanoha, Kashiwa 277-8568, Japan
東大新領域 〒277-8568 柏市柏の葉5-1-5Considering a breeding blanket installed in the ITER size TF coils to demonstrate the electric generation,
the electric power for DEMO using the structural design of ITER is investigated. Assuming that thebreeding blanket thickness is 1.2m, and so the minor radius is 1.4m. We have investigated self-consistentparameters for ITER size DEMO using a conceptual design code. It is shown that our designed reactor canoperate Pel(Generator output) =135~180MW and Q=3.2~4.2, where βN=3.0~3.5, HH98(y,2)=1.1~1.2, andne/nGW=0.45~0.50.This result suggests that DEMO using of the structural design of ITER can generate
several hundred MW of Pel while the net output is small or in some cases, negative.

1. Introduction
ITER was designed under the international
cooperation [1] and is currently underconstruction. The next step of ITER is considereda demonstration plant (DEMO) that can supply
electric power actually. A DEMO conceptual
design has been done by several groups so far [2].
Many of DEMO designs are larger size than ITER
and have technical or engineering challenge. In
order to construct DEMO, many expenses andperiods are expected. Therefore, the design of
low-cost DEMO that can be constructed
immediately after experiments of ITER isimportant.
In this paper, we have investigated DEMO using
structural design of ITER. By using the TF coils
same as those of ITER, DEMO can be expected toconstruct early at lower cost. Assuming a breedingblanket, which must be thicker than the ITER shieldblanket, the net and generator outputs have been
estimated by using the design code.
2. Conceptual design code
Major Physics constraints concerned with reactor
designs are shown as follows:
1. Plasma pressure limit (βN)
2. Density limit nGW (Greenwald density limit)
3. Safety factor q
4. Energy confinement performance
In our design code, based on the above
constraints, we have investigated design parametersthat satisfy the following conditions:
1. Driven current profile by external input, andthe NBCD efficiency to achieve it by theneo-classical model [3]. The beam pressure isalso estimated.

2. The amount of bootstrap current and profile
3. Fusion output and α-particle pressure by fusion
reaction
4. Power balance in the plasma
These conditions have a nature that if any one
changes, change the whole, so iterative calculationis required. A diagram of our conceptual designcode is shown in Fig.1. By the design code it ispossible to obtain self-consistent parameters interms of plasma physics [4].
This paper discusses the electric power of fusion
reactor by the above design code. TF Coils with thesame size as ITER and tritium breeding blankets forelectric generation are assumed. Assuming that thebreeding blanket thickness is 1.2m, which is thicker
than ITER shield blankets+VV (0.6m), so the minor

Fig.1. Design code diagram [4]Table I. Design parameters

500(a)

βN=3.0βN=3.5βN=4.06.2/1.4
4.43
1.9/0.45
8.4
3.13/1.45
5.3
1
2.07
1.43060

radius a is reduced to a=1.4m from the design valueof ITER (a=2.0m). The design parameters fromthese assumptions are shown in Table I.
In order to keep q95 larger than 3, Ip=8.4MA with
κ95=1.9 and δ95=0.45 is required. The higher aspectratio A or elongation κ, however, results in thevertical stability more unstable. Since the instability
is critical at A=4.43 and κ95=1.9, stabilization coils
must be installed inside of the TF coils [2]. This isan engineering constraint of the present design.
By use of the fusion power Pfus and the externalcurrent drive power PCD as calculated by the designcode the thermal power Pth is written as
Pth=(0.8fm+0.2)Pfus+PCD, where the factor fm is theadditional energy generated by nuclear reactions in
the blanket, and was assumed that fm=1.4 [2]. The
generator output Pel is defined as Pel=ηTDPth, whereηTD is the thermodynamic efficiency.
The auxiliary power needed in the whole plant isgiven by the re-circulation power for H & CD (Prec)
and the power used for the plant operation POS. Prec
is written as Prec=PCD/ηCD, where ηCD is theelectrical efficiency of the CD system. The value ofPOS is estimated by the scaling law of theGeneromak Model [5]. The net electric output Pel,netis defined as Pel,net=Pel-Prec-POS.
3. Result
The result obtained by the design code is shown
Fig.2, where parameters of Table I are used. It isestimated that our designed reactor can generate
several hundred generator output at ne/nGW=0.3~1.0.
The high ne/nGW, however, reduces Pel,net rapidly,
because the higher H & CD power is required.
Therefore, increasing ne/nGW increases Pel, but isunfavorable from the viewpoint of obtaining Pel,net.
Our designed reactor can operate Pel =135~180MW
and Q=3.2~4.2, at βN=3.0~3.5, HH98(y,2)=1.1~1.2 andne/nGW=0.45~0.50, but Pel,net is close to zero. To
obtain the high Pel,net with the positive Pel, therefore,

P el (MW)

400
300
200
100
00.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

10.8 0.9

1n e/n GW
100(b)

0P el,net (MW)Parameter
R/a (m)Ακ95/δ95Ip (MA)q95/q0BT (T)NBI energy (MeV)
ZefffmηTD (%)ηCD (%)-100-200-300

βN=3.0βN=3.5βN=4.0-400-500-600
0.2 0.3

0.4 0.5 0.6 0.7

n e/n GW
Fig.2. Variation of electric power versus ne/nGW inTable.I parameter when βN varies between 3.0 to
4.0. (a) The generator output Pel is shown. (b)The net electric output Pel,net is shown.

achievement of the high βN which is larger than 4.0
is required. For example, Pel,net=56MW can beobtained at βN=4.0, HH98(y,2)=1.25 and ne/nGW=0.57.
4. Conclusion
Considering a breeding blanket installed in theITER size TF coils to demonstrate the electricgeneration, the electric power for DEMO using
structural design of ITER is investigated. Assumingthat the breeding blanket thickness is 1.2m, and so
the minor radius a is 1.4m. In order to design
DEMO, we investigated self-consistent parameters
using the conceptual design code. It has been shownthat our designed reactor can operate Pel=135~180MW and Q=3.2~4.2, at βN=3.0~3.5,HH98(y,2)=1.1~1.2 and ne/nGW=0.45~0.50. Capable ofoperation in low ne/nGW is appeal of our design.
And, it is revealed that slightly positive net output
Pel,net can be obtained in some cases, for example,
56MW with βN=4.0, HH98(y,2)=1.25 and ne/nGW=0.57.
References[1] Summary of the ITER Final Design Report, July
(2001).
[2] Text-Fusion Reactors, J. Plasma Fusion Res 87
Supplement (2011).
[3] K. Okano: J. Nuclear Science and Technology, 27-8
(1990) 689/699.
[4] K. Okano: J. Society for Simulation Technology 22(2003) 83/88.
[5] J.Sheffield, R.A.Dory, S.M.Cohn, J.G.Delene:Fusion Technology, 9 (1986).