Coupled reactor physics and thermal-hydraulics analysis of an SCW-SMR reactor concept – Part II: Improvement of the concept and sensitivity analyses

• Inlet orifice plates were introduced and optimised in the SCW-SMR fuel assemblies. • The system mass flow rate was increased to reduce the outlet temperature to 500 °C. • The maximum cladding temperature could be reduced from around 610 °C to 520–525 °C. • The thermal inequalities could be significantly reduced in the core. • Sensitivity analysis for the thermal properties of the SCW-SMR concept was performed. In the frame of the EU ECC-SMART project, the pre-conceptual design of a water-cooled small modular reactor operating at supercritical pressure (SCW-SMR) with seven heat-up stages is under development and assessment. The first part of the two-part paper presented the concept design, the models developed at BME in the Apros thermal-hydraulics system code and in the Serpent 2 Monte Carlo reactor physics code, the developed coupling methodology of these models, and the results of the first coupled calculations. This second part of the paper outlines the approaches adopted by the BME research team to improve the original design, primarily to reduce the high cladding temperatures. The effects of the increased mass flow rate and the introduction of inhomogeneous inlet orifices are thoroughly investigated and presented. Finally, a comprehensive sensitivity analysis has also been performed to demonstrate the robustness of the proposed design.