Session: 04-07: SMRs, Advanced Reactors and Fusion

Paper Number: 133703

133703 - Optimization of Inventory Control Strategies for Part Load Operation in a Sco2 Recuperated Brayton Cycle for a 5 Mwth Heat Pipe Micro Modular Reactor 

Abstract: 

Supercritical CO₂ (sCO₂) recuperated Brayton cycles have demonstrated versatility and efficiency, making them an attractive choice for various energy applications. The compact design and efficient power generation of sCO₂ systems align well with the requirements of Heat Pipe Cooled Micro Modular Reactors (MMRs). Due to the remote area application, efficiently meeting grid power demands is crucial for such systems. The investigation of control strategies has prompted the consideration of the inventory tank, which has emerged as a promising option. When the power demand decreases, mass is removed from the cycle and stored in the tank. This decreases the work of the turbine while increasing the work of the compressor, allowing the required power to be matched. Conversely, when power demand increases, the opposite occurs and mass is injected into the cycle.

This study deals with the implementation of an inventory control strategy for part-load operation in a 5 MW_th Recuperated sCO2 Brayton Cycle, modelled using the thermal-hydraulic system code ATHLET.  A preliminary investigation emphasizes the crucial role of the inventory tank design for efficient control. The most effective design is identified by investigating the impact of tank volume and pressure on cycle performance and key parameters.

However, when relying solely on the inventory tank for control, matching lower power demands is challenging. The removal of mass from the cycle leads to low pressures at the compressor inlet. Without countermeasures, subcritical conditions are reached when the power decreases below 53% of the nominal capacity of the studied system.

To overcome the limitations of using the inventory tank as the sole control strategy, combined control approaches are explored, preventing excessively low pressures and enhancing overall flexibility. Two different methods are being considered for these purposes. The first method involves increasing the inlet temperature of the compressor by adjusting the mass flow rate of air at the ultimate heat sink. This results in a higher compressor inlet pressure. The second method involves implementing a recirculation line with a valve that opens when the pressure at the compressor inlet falls below the desired minimum value. Recirculating mass in front of the compressor helps to increase the pressure. The study further investigates the combined performance of the inventory tank and these additional control strategies under load-following conditions, simulating an aggressive power rate change of 7.5%/min. It is shown that the combined control strategies are able to reach a lower power level, ensuring a wider cycle operation range.

Presenting Author: Matthias Peiretti University of Stuttgart

Presenting Author Biography: Matthias Peiretti graduated in Nuclear and Energy Engineering from Polytechnic University of Turin. He joined the Institute of Nuclear Technology and Energy Systems at the University of Stuttgart in September 2022. As a Research Assistant and Doctoral Candidate, he focuses on modelling a sCO2 Cycle for Heat Pipe Cooled Micro Modular Reactors using the ATHLET thermal-hydraulic system code.

Authors:

Matthias Peiretti University of Stuttgart
Markus Hofer University of Stuttgart
Michael Buck University of Stuttgart
Ruggero Meucci University of Stuttgart
Jörg Starflinger University of Stuttgart