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Nuclear fusion technology is one of the main valuable candidates for providing a trustable base load in low-carbon future energy scenarios, thanks to its power density, low emissions and flexibility, together with innovative power conversion systems that could improve its performance, as the supercritical CO2 Brayton cycle. Since the nuclear plant will be required to provide variable loads, due to the fluctuating nature of renewable energies, a powerful modelling tool will be necessary to simulate different power outputs. The present paper presents a dynamic model of a supercritical CO2 power cycle developed with Modelica, aimed at the design of control systems to adjust the power production according to the load required. Thanks to the activity of three PI controllers, the system is able to follow a variable load profile while preserving the turbomachinery inlet temperature, to avoid any possible damage of the devices. The work has shown the adequacy and potential interest of the use of Modelica in this kind of analyses., Peer Reviewed, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Postprint (published version)

A modified recuperative supercritical CO2 cycle for DEMO fusion reactor is analysed. A layout with just one recuperator is used, because of the relatively low temperature of the breeding blanket coolants. The proposed cycle is able to integrate several thermal sources with different temperature ranges and includes two kinds of thermal energy storage to overcome the pulse operation: a two-tank molten salt storage and a concrete storage. The design point is obtained using the Engineering Equation Solver (EES) environment, which allows to use pure substance models for CO2, helium and water. Once the design point is calculated, the sizing of pipes, heat exchangers, turbomachines and energy storage systems has been performed in order to obtain a preliminary estimation of the layout and its complexity. So, the power conversion system has been split into four equal parts in order to use commercial pipe diameters. Even though Printed Circuit Heat Exchangers (PCHE) have been used, extremely large sizes have been obtained, especially for the HTR recuperator. These sizes contrast with the small values obtained for the turbomachines, whose preliminary design has been carried out, using the AXIAL™ meanline design software. In addition, the two largest heat exchangers are divided into serial and parallel configurations when assessing the allocation of the components of the power conversion system to reduce the footprint. An average electric efficiency (including pulse and dwell period) of 28.25% has been reached. The required mass of molten salt per each power conversion subsystem is 2568¿t, while the mass of concrete is 833¿t. Regarding the footprint, 85¿×¿170 m2 are required for each power conversion subsystem, including the storage systems., Postprint (published version)

The EUROfusion research program is currently exploring alternative solutions for a future fusion power plant with DEMO (DEMOnstration Power Plant) prototype. One of the most important issues arising from a dual coolant lithium lead blanket-based reactor is the correct integration of the four thermal sources in order to achieve the highest electricity production. This study analyses the technical feasibility of supercritical CO2 Brayton power cycles. Starting with a classical re-compressed cycle, which is taken as the baseline case, two alternative proposals are investigated. On the one hand, a modified re-compressed layout with only one recuperator is studied, and is found to achieve the same electric efficiency as that of the baseline case (34.6%). On the other hand, an optimised recuperated layout is proposed, which achieves a 33.6% electric efficiency. A parametric study is conducted in order to optimise the heat exchanger size. When the re-compressed layout is optimised, a loss of efficiency (5%) is experienced. In the case of the recuperated layout optimisation the efficiency loss is reduced to 3%, achieving a reduction in heat exchanger size of 2/3., Postprint (published version)

In the framework of the research program undertaken by the EUROFusion consortium (within H2020), the feasibility has been analysed of using a supercritical carbon dioxide Brayton cycle as the power conversion system in a future fusion nuclear reactor with breeding blankets of the type Dual Coolant Lithium-Lead. The integration in the layout of the thermal sources has been optimized and thermal energy storage has been featured in order to decouple the reactor operation from the power generation. Dynamic modelling of the selected design has been performed with the thermal-hydraulic system code RELAP5-3D. Presently the model only includes the CO2 cycle, and the circuits of fluids exchanging heat directly with the cycle, along with all the needed heat exchangers. The code allows the simulation of control systems. Control strategies aimed to stabilize some plant parameters have been implemented., Postprint (author's final draft)

The purpose of this website is to provide information about fusion and fusion research, particularly the research activities related to EUROfusion. Neither EUROfusion, the EUROfusion Research Units, the European Commission, nor anyone acting on their behalf, is responsible for any damage resulting from the use of information contained on this website. Unless otherwise explicitly stated, all information, text and electronic images contained on this website are the intellectual property of EUROfusion. You may reproduce and publish EUROfusion’s material for non-commercial, scientific, news and educational purposes provided that you acknowledge EUROfusion as the source. In crediting EUROfusion you may optionally provide a link to our website: www.euro-fusion.org. The material must not be used to state or imply the endorsement by EUROfusion(or by any EUROfusion employee) of a commercial product, process or service, or used in any other manner which might mislead., This paper presents an exploratory analysis of the suitability of supercritical CO2 Brayton power cycles as alternative energy conversion systems for a future fusion reactor based on a DCLL (dual coolant lithium-lead) blanket, as prescribed by EUROfusion. The main issue dealt is the optimization of the integration of the different thermal sources with the power cycle in order to achieve the highest electricity production. The analysis includes the assessment of the pumping consumption in the heating and cooling loops, taking into account additional considerations as control issues and integration of thermal energy storage systems. An exergy analysis has been performed in order to understand the behavior of each layout.Up to ten scenarios have been analyzed assessing different locations for thermal sources heat exchangers. Neglecting the worst four scenarios, it is observed less than 2% of variation among the other six ones. One of the best six scenarios clearly stands out over the others due to the location of the thermal sources in a unique island, being this scenario compatible with the control criteria. In this proposal 34.6% of electric efficiency (before the self-consumptions of the reactor but including pumping consumptions and generator efficiency) is achieved., Preprint

Postprint (published version)