Principal Research Results

Development Scenario of Fusion Energy following the ITER Project

BackgroundA development scenario of fusion energy by the three stages (i.e. the experimental reactor, the demonstration reactor, andthe commercial reactor) is discussed in the world. In order to construct the feasible development scenario, it is necessary to evaluate
qualitatively which component of reactor technology should be developed to what extent. Furthermore, for the realization of fusionenergy, it is also important for the fusion energy to be recognized as one of the energy source as soon as possible. Form the viewpointof the future electric supplier, we proposed the conceptual design of a commercial reactor, which is named CREST, and this design isconsidered to be one of the Japanese development goals of fusion energy in the atomic energy commission of Japan. On the other
hand, the project of the experimental reactor, i.e., International Thermonuclear Experimental Reactor (ITER) is underway, and its experimental plant and R&D activities such as large superconductor technology are almost completed. Hence, in order to complete thedevelopment scenario of the fusion energy, it is the most important to investigate the demonstration reactor following ITER.

Objectives
A conceptual design of the demonstration reactor “Demo-CREST” followed by CREST is carried out, and a development scenario of the fusion energy is constructed. Accordingly, we make the suggestion for the Japanese development policy of fusion energy.

Principal Results
1. The development scenario of three stages, i.e., ITER (the experimental reactor), Demo-CREST (the demonstration reactor), andCREST (the commercial reactor), is constructed in order to realize the demonstration of a fusion power plant in 2030’s earlier thanusual for the first time in the world, and is was proposed in the fusion expert group of the atomic energy commission of Japan(Figure-1). This scenario is characterized by a single device, into which the demonstration reactor and the proto-type reactor arecombined.
2. In the Demo-CREST operation, the improvement of plant performance is steadily explored by the following two phase, (i) thedemonstration phase, and (ii) the development phase. In the demonstration phase, a net electric power of 50MW is achieved basedon the results from the ITER project. In the following development phase, a net electric power of 100MW is feasible by the advanced plasma and reactor technology (improvement of thermal efficiency more than 40%, and so on) applied to CREST.
Consequently, the demonstration of the key technology required for improving economic performance in Demo-CREST leads to theprospect of CREST (Table-1).
3. In the Demo-CREST design, the high efficiency of neutron usage by the large blanket modules enables to achieve the high tritium
breeding ratio. Accordingly, the replacement method of a large blanket module is proposed, and it enables to shorten the maintenance period and to replace modules according to the neutron wall load (Figure-2). Consequently, the supply of tritium and plantmaintainability is insured in Demo-CREST, which leads to the stable operation inevitable to the demonstration reactor.

Further Developments
On the basis of this development scenario, the objective parameter of each development stage will be precisely evaluated,
and the development guideline of fusion energy to the user-friendly power plant will be constructed.
Main Researchers:
Ryouji Hiwatari, Research Scientist, Advanced Reactor System Sector, Nuclear Technology Research Laboratory
Yoshiyuki Asaoka, Ph. D., Staff Member, R&D Planning GroupKunihiko Okano, Ph. D., Research Fellow, Advanced Reactor System Sector, Nuclear Technology Research Laboratory
Reference
Conceptual Study on Demonstration Reactor, Demo-CREST, for Development Strategy of Fusion Power Reactor (1) -Basic conceptJanuary 2004, Report No.T03008 (In Japanese).
R.Hiwatari, Y.Asaoka, K.Okano, T.Yoshida and K.Tomabechi, “Generation of net electric power with a tokamak reactor under foreseeable physical and engineering conditions”, Nuclear Fusion Vol.44, 106-116, 2004

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5. Nuclear - Concept of advanced reactors

Development scenario of Fusion Energy

Experimental
Reactor
ITER
Tokamak devices
JT-60U etc
Feasibility of burning
plasmaFrom 1980's to present

Feasibility of net
electric power
generation
From 2015 to 2035

Commercial Plant
CREST

Demonstration
ReactorDemo-CREST

Introduction into market
2050'sDemonstration offusion power plant2030'sHigh priority issue discussed inJapan, US, and Europe.

Fig.1 Outline of fusion energy development and the role of Demo-CREST
Table 1 Development of net electric power in Demo-CREST

Development of reactor technology
Demo-CREST
Major radius 7.3m
Max. magnetic field 16T

ITER

Development of plasma

Major radius 6.2m
Max. magnetic field 13T

Demonstration
phase
Thermalefficiency 30%

ITER
Referenceplasma(demonstration ofburning plasma)

0MWe

ITER
Advancedplasma(development of theplasma required for apower plant. )500MWeCREST
Advanced
plasmaDevelopment
phase
thermalefficiency 40%

CREST
Major 5.4m
Max. magnetic field 13T
Thermal efficiency 41%

900MWe1100MWe

1200MWe（COE：60mill/kWh）In ITER, demonstration of burning plasma and development of plasma required for a power plant
are carried out. In the demonstration phase of Demo-CREST, 500MWe of electric generation isdemonstrated by the ITER advanced plasma. In the development phase, theimprovement of plasma
and thermal efficiency by replacement of blanket enables to generate more than 1000MWe, and thatlead to the prospect of CREST.
Shield40m

Handling device
Blanket modules

Fixed rail

Moving rail Maintenance cask

Demo-CREST maintenance system

Demo-CREST cross section

Fig.2 Cross section of Demo-CREST and its maintenance system
The blanket system, which is divided into three modules, is replaced by a handling device. The
handling device moves on the fixed rail on the maintenance port and on the moving rail in the cask.
(blanket: the component for the thermal output and tritium breeding. In Demo-CREST, the division of the blanket system into
three modules leads to the efficient maintenance.)

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