Analysis of supercritical CO₂ Brayton power cycles in nuclear and fusion energy

Abstract

The first part of this article focuses on proposal of the appropriate cooling cycle for the specific fusion reactor. Furthermore, cooling technology of fusion power plant, two supercritical CO₂ Brayton cycles and its positive and negative aspects are described. Additionally, comparison of cycles in terms of difficulty and possibilities of using more resources at once are depicted. This work also gives a principal preview of main technical parameters of supercritical CO₂ cooling system. The second part describes the optimization of suggested design in order to maximize power of a fusion power plant and new computational software for optimization of the cooling cycles therewith, which would be also useful in the field of nuclear power engineering. The results of this article is comparison of efficiencies, power and other physical parameters of two layouts.

Introduction

The possibility of using supercritical carbon dioxide(S-CO₂) as a cooling medium was first introduced by E.G. Feher in 1967, which is described in the literature, e.g. [1]. From that time many investigations were done in the field of supercritical CO₂ as a cooling medium in fission and fusion reactors as well. For instance Hejzlar et al. described supercritical CO₂ Re-compression Brayton cycle as a promising power conversion system for sodium fast reactor (Generation IV fission reactors) [2]. The goal is to increase operating temperature, which means to increase the efficiency of nuclear power reactors, that is nowadays lower than efficiency of fossil power plants [3]. The computational analysis also proves that varieties of the supercritical CO₂ power cycle brings many benefits compared to Rankine steam cycles and also Helium cycles [1], [4].

Against Rankine steam cycles supercritical CO₂ power cycles are more compact and they are simpler in some respect. Benefits compared to conventional Rankine steam cycle are also in finances. For turbine inlet temperature 550 °C and compressor outlet pressure 20 MPa is the cost of the power plant reduced by approximately 18% [1].

Against Helium cooling cycles supercritical CO₂ cycles work on lower temperatures with the same efficiency and work of compressors is lower by up to 33% [1].

It means that there is a possibility of using supercritical CO₂ as a power conversion cycle for fusion reactors.

Power conversion cycles heavily influence the efficiency of fusion power plants. The analysis of supercritical CO₂ Brayton cycle power conversion system is being intensively solved in previous research, e.g. [5], where was concluded that the Re-compression supercritical CO₂ Brayton cycle using Breeding Blanket, First Wall and Divertor as a heat source is an optimal version of Brayton cycle.

The work that leads to a design of a fusion power plant with supercritical CO₂ power conversion cycle stands on the grounds of the studies that were made by Angelino, Feher, Verhivker, Gokhstein [1] and by actual works of Linares [4].