The Dutch maritime sector aims to develop a maritime nuclear reactor within 10 years to support its decarbonization efforts. Naval vessels are a key area of interest, but their significant power fluctuations challenge conventional nuclear reactors, which are designed for stable operation. This study assesses the technical feasibility of nuclear propulsion for naval vessels by investigating a Very High Temperature Reactor combined with a supercritical carbon dioxide recompression cycle using a dynamic modeling approach. Simulation results show that shaft speed remains stable, the reactor operates within a safe temperature region, and turbomachinery stays within design limits. However, temperature and pressure variations in the heat exchangers raise material integrity concerns, potentially requiring a redesign of the cycle configuration. Nevertheless, the results strongly suggest that a nuclear power plant can achieve gas turbine level power ramps. Therefore, further research should not be limited by the assumption that nuclear power is only suitable for baseload operation.

ARC-100 plant control during load following has been investigated using coupled SAS4A/SASSYS-1 and PDC codes. ARC-100 is a 286 MW_th/100 MW_e sodium-cooled fast reactor featuring sCO₂ cycle for energy conversion. A linear reduction in grid demand from 100% to 0% at 5%/min rate was simulated and the required plant control action was calculated to match that grid demand. The paper presents the results of the ARC-100 plant load following with inventory control on the sCO₂ cycle and several reactor control options.

The UK Industrial Fusion Solutions Ltd is paving pathway for a commercial magnetically confined fusion power plant, namely Spherical Tokamak for Energy Production (STEP), with the ambition of building a STEP Prototypic Powerplant (SPP) by 2040. The fusion power cycle design poses the following key challenges: 1) high power cycle conversion efficiency to overcome large plant parasitic loads, 2) integration of different heat sources at multiple temperature levels from the tokamak in-vessel components, including low temperature heat sources, 3) high power cycle operational flexibility, and 4) high reliability and plant life for intermittent pulse mode of operation of SPP during the initial phases. Closed-loop CO2 power cycle show promises in realising high efficiency (>550 °C), efficient integration of low-grade heat by capitalizing the enthalpy gap due to real gas effect of CO2, and high power density CO2 turbine & compact heat exchangers signifying the potential of realising operational flexibility. This paper compares the thermodynamic performance of three novel CO2 cycle configurations, namely 1) transcritical CO2 cycle variant; 2) supercritical CO2 cycle variant; and 3) transcritical CO2 blend based power cycle variant (using SO2 as the dopant), to efficiently integrate four different heat sources at different temperature levels from the fusion machine, demonstrating the feasibility of using such a power cycle design for SPP.

This research addresses the challenges of clean energy production for industrial applications and highlights the role of nuclear power in achieving economic, safety and environmental sustainability goals. A thermodynamic analysis of a high-temperature nuclear reactor integrating Brayton cycle and reboiler was carried out. System performance was evaluated by varying turbine inlet temperature and compressor pressure ratio. The results show that higher reboiler inlet temperature significantly improves the power cycle efficiency up to the optimal threshold of 740°C, beyond which the efficiency improvements diminish. However, increasing turbine efficiency can significantly increase thermal efficiency, raising it from around 25% to 45%. The effect of compressor efficiency is less pronounced, with thermal efficiency increasing from 21% to 25%. The net power output increases with the turbine inlet temperature and compressor pressure ratio, with the peak temperature of 725°C and pressure ratio of 4.0, with the maximum power output of approximately 3.35MW. These insights are critical to optimize the design and operation of nuclear-driven thermal power systems to maximize efficiency and net power output.

Next generation solar tower plants aims at increasing the maximum achievable temperature thanks to the adoption of advanced heat transfer medium and sCO₂ cycles. In this context, the Horizon Europe Powder2Power project aims at demonstrating at MW-scale the adoption of fluidized particles as heat transfer medium in CSP plants. This work focuses on the numerical model for the sizing and simulation of the sCO₂-particle multistage heat exchanger to be used for the overall plant analysis. The developed model adopts reliable heat transfer correlations available in the literature to size the heat exchanger based on the target thermal duty and pressure losses. A sensitivity analysis is presented to study the effect of the main design parameters on the component size and efficiency. The model is then used in a case study for the complete techno-economic optimization of fluidized particle based CSP plants. Results show that the temperature differences at the cold- and hot-end of the heat exchanger greatly influences the minimum number of stages and that an increase in the number of stages leads to a reduction in the total heat transfer surface. The economic optimization highlights that the fluidized bed heat exchanger represents a marginal share of the plant overall cost and thus that there is no convenience to adopt a component with a little number of stages and penalize the efficiency and that the stage number in real plants would be likely more constrained by other technical aspects related to components manufacturing.

While all commercial concentrating solar power (CSP) plants with central receivers are equipped with the steam Rankine power cycle, supercritical CO₂ (sCO₂) cycles are seen as a promising advancement. They offer higher efficiencies and more compact turbomachinery at high temperatures compared to the steam Rankine cycle, however, sCO₂ cycles face challenges related to high pressures and temperatures, which increase material demands and the mass and cost of heat exchangers. As the need for flexible electricity generation grows, the thermal inertia of the power block, linked to its metal mass, becomes increasingly important. This study examines and compares the component sizes, material usage, and economic and flexibility impacts of sCO₂, CO₂ mixtures, and steam Rankine cycles for commercial-scale CSP applications. All cycles are designed with the same thermal energy input, keeping the solar field and thermal storage constant. Heat exchanger designs, including primary heaters, recuperators, and air-cooled units, follow the ASME Code and are modeled using Aspen Exchanger Design & Rating. Since no commercial sCO₂ turbines exist at this scale, turbine design parameters are estimated using a developed simplified approach. Results are compared with existing studies to assess component-level and system-level implications in terms of cost, performance, and flexibility.