Tokamak Reactor System Analysis Code for the Conceptual Development of Demo Reactor

The development strategy of nuclear fusion energy in the Korea National Basic Plan for the Development of Fusion Energy consists of several major programs. These are shown in Fig. 1, and include KSTAR for the study of a long-pulse, advanced tokamak operation, ITER for a burning plasma experiment, the DEMO reactor for the demonstration of producing net electricity from a fusion reactor, and a commercial fusion reactor. Material testing and integral testing of the reactor components must be performed using IFMIF and CTR (Component Test Reactor). The demonstration fusion power plant DEMO reactor is regarded as the last step before the development of a commercial fusion reactor. The primary requirements for the DEMO reactor can be summarized as follows: First, it should demonstrate net electric power generation. Second, it should demonstrate tritium self sufficiency. Lastly, it should demonstrate the safety aspects of a power plant and should be licensable as a power plant. To develop the concepts of fusion reactors and identify the design parameters, dependence on performance objectives, design features and physical and technical constraints have to be considered. System analyses are necessary to find reactor parameters that can optimize figures of merit such as the major radius, ignition margin, divertor heat load, and neutron wall load. In a system analysis, effects of the plasma physics and technology constraints are expressed in simple mathematical model and are incorporated into a plant power balance equation and a plasma power balance equation. Thus, by solving the plant power balance equation and the plasma power balance equation, the reactor parameters that satisfy the plasma physics and technology constraints can be found simultaneously. A similar approach was used in the scoping studies for the ITER, the Conceptual Design Activity. The basis of the applied physics can be found in the ITER Physics Basis [1, 2]. To explore the range of concepts of a DEMO reactor and a fusion power plant, assumptions on the level of physical and technological development have to be made. There will be many reactor models depending on the assumptions, from the least ambitious plasma physics combined with the least ambitious technologies to the most ambitious in all areas. Therefore, it is stressed that the system analyses are intended to capture the range of likely outcomes and to identify the necessary R&D areas for the realization of the concept in terms of both physics and technology. In this study, as a part of a feasibility study for an early realization of a DEMO reactor, the performance of an ITER-like DEMO reactor was investigated; the plasma and machine size are identical to those of ITER Tokamak reactor system analysis code was developed at KAERI (Korea Atomic Energy Research Institute) and is used here for the conceptual development of a DEMO reactor. In the system analysis code, prospects of the development of plasma physics and the relevant technology are included in a simple mathematical model, i.e., the overall plant power balance equation and the plasma power balance equation. This system analysis code provides satisfactory results for developing the concept of a DEMO reactor and for identifying the necessary R&D areas, both in the physics and technology areas for the realization of the concept. With this system analysis code, the performance of a DEMO reactor with a limited extension of the plasma physics and technology adopted in the ITER design. The main requirements for the DEMO reactor were selected as: 1) demonstrate tritium self-sufficiency, 2) generate net electricity, and 3) achieve a steady-state operation. It was shown that to access an operational region for higher performance, the main restrictions are presented by the divertor heat load and the steady-state operation requirements.