Hejzlar et al. [1] have identified the recompression supercritical CO2Brayton cycle (S-CO2) as a promising power conversion system for some Generation IV fission reactors (sodium fast reactor). This type of cycle has been also proposed for fusion reactors because, besides of the aspects of high efficiency, CO2exhibits certain advantages in terms of tritium recovery. Although it can be dissociated to CO under heavy neutron irradiation and tritium permeation into CO2could react with it, its separation is easier than for water [2]. On this basis, a domestic R&D program called TECNO FUS[3] was launched in Spain in 2009 to support technological developments related to a specific concept of dual-coolant (He/Pb–Li)∗Corresponding author. Tel.: +34 91 542 28 00; fax: +34 91 559 65 69.E-mail address: linares@upcomillas.es (J.I. Linares).breeding blanket for fusion reactors based on Model C configuration for fusion Power Plant Concept (PPCS) [4].The S-CO2 cycle has been already analyzed by Angelino [5]. It is a Brayton cycle with CO2as working fluid and with two recuperators, one at low temperatures (LTR) and another at high temperatures(HTR). Serrano et al. [6] developed a variant of S-CO2 cycle, designated as REC3 (three recuperators), with one more recuperator(BBR) and with an efficiency higher than 46%. Further investigations lead to a new improved one, designated as REC2, in which HTR is suppressed and thus BBR assumes its thermal load. So, this new design includes two recuperators, as in classical S-CO2, but with the same efficiency than in REC3 [7]. Fig. 1 shows the new recuperator BBR included in both REC2 and REC3 designs and integrated in the classical S-CO2 cycle. The REC2 design has been proposed as the power cycle for TECNO FUS fusion reactor.The main goal of this paper is to describe the methodology followed for the design of the different heat exchangers of the REC2