24P103-P
Trade-off analysis on the fusion reactor design using FUSAC
統合計算コードFUSACを用いた核融合設計におけるトレードオフ分析
Kazuya Mitsueda, Yuichi Ogawa, and Yuya Miyoshi
満枝和也, 小川雄一，三善悠矢
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5-1-5
The nuclear fusion reactors including the element of many fields such as hydrodynamics andelectromagnetism are very complicated systems, and there are many phenomena that are not yet elucidated.
We are using a system design code FUSAC for fusion reactor design, in which various physical andengineering parameters are employed. We visualize those results with MATLAB so as to investigate a
trade-off between various design parameters.

1. Introduction
The nuclear fusion reactors including theelement of many fields such as hydrodynamics
and electromagnetism are very complicatedsystems, and there are many phenomena that are
not yet elucidated. If we overlook the perspectiveof the nuclear fusion reactor, a system designcode is very important. In this paper, we use asystem design code FUSAC[1], and a trade-off
between various parameters is analyzed, so as toget the prospect of the nuclear fusion reactor
design that stood on the future technicaldevelopment. In addition the visualization ofcalculated results is quite important, as well.
Here we introduced MATLAB so as to visualize[2] the relationship between various parameters.
2. Parameter Region
FUSAC employs a zero-dimensional plasma
model base on ITER Physics Guidelines[3], andGeneromak Model for economic analysis. Here wehave carried out parameter survey for steady-state
tokamak by changing several parameters[4]. Theemployed parameters and their parameter regions
are listed in Table 1.

Here, the minor radius is changed from 1.2 m to 3.0 m,
with a step size of 0.2 m, and the aspect ratio is changed
from 2.5 to 4.9 with a step size of 0.3. While, the major
radius is limited the parameter region between 5.5 m and
10 m. Step sizes of other parameters are listed in Table
1, as well. By using these parameter regions and theirstep sizes, we take database of 300,000 design

points.
3. Result and discussion
The results obtained by system design code are
showed Figs.1~4.
Figure 1(a) shows the relation between theconfinement improvement factor HH and the net
electric power Pe, in which layer indicatesnormalized beta value. From this figure, high β isnecessary to attain a large net electric power.
While, if the normalized beta value is limited to below (e.g., βN < 2), the net electric power larger than
1 GWe might be difficult.

Table ⅠParameter region

Parametera(m)Aκδ
Te(=Ti)(keV)qΨ
Btmax(T)ηe(%)
ηNBI(%)

Region1.2~3
2.5~4.9
1.5~2.1
0.2~0.5
10~193.0~6.0
13~1930~4030~50

Step size
Δa=0.2
ΔA=0.25
Δκ =0.1Δδ=0.15
ΔTe=3ΔqΨ=1
ΔBtmax=1.5
Δηe=10ΔηNBI=10Fig.1(a) HH factor & PE(layer: normalized beta value)Here we pay attention to the relation between HHfactor and the net electric power, and find acorrelative expression of the HH factor and PE.

PE  HH 0.86(1)

Next, we considered the role of the magnetic
field in Fig. 1(a). In Fig. 1(b), the each point isrepresented by the maximum magnetic field Bmax,in which the range of the Bmas is 13 ~ 19 T.
When the magnetic field is restricted to be Bmax =13T, the design point is limited at the relatively
narrow region.

Finally, we considered the current drive power.
Figure 3 shows the relation between the current
drive power and the net electric power, in whichlayer indicates a normalized beta value, as well. If
the normalized beta value is low (e.g., . βN = 2), thenet electric power might be limited to be less than
300 MW, even if the current drive power isincreased up to more than 100 MW. At themoderate current drive power (e.g., PCD=100 MW),the net electric power might increases as the betavalue is increased.

Fig.3 PE & PCD (layer: normalized beta value)
Fig.1(b) HH factor & PE(layer: Max Magnetic field)

Figure 2 shows the relation between theconfinement improvement factor HH and thebootstrap fraction fbs, in which a layer indicatesnormalized beta value. We can see that the bootstrap
current fraction is not so sensitive to the HH factor,
and seems to be monotonically increased as thenormalized beta value is increased.

Fig.2 HH factor & BC rate(layer: normalized beta value)

We have developed the visualization techniquewith MATLAB so as to study the trade-off analysis
between various design parameters in fusion reactor
design. At present, we have found that thenormalized beta value is playing an important role
for an attractive fusion reactor design.
References[1] R. Hiwatari, T. Yoshida, Y. Asaoka and K. Okano:
The development of the nuclear fusion reactor
simple design cord for economy and environmentalload evaluation of the nuclear fusion reactor.
[2] Zoran Dragojlovic, A. Rene Raffray and Farrokh
Najmabadi: Progress of ARIES Systems CodeDevelopment. ARIES-“TNS”Project Meeting June
14 and 15, 2007.
[3] N.A. Uckan and ITER Physics Group: ITERPHYSICS DESIGN GUIDELINES:1989 ITER
DOCUMENTATION SERIES, No.10..
[4] Plasma Performance Required for a Tokamak
R.Hiwatari, Y.Asaoka, K.Okano, T.Yoshida andK.Tomabechi :Reactor to Generate Net ElectricPower.US-Japan Workshop on Fusion Power Plantand Related Advanced Technology withparticipation of EU