Transient Numerical Simulation Analysis Of Nuclear Power System Coupled With DFR And S-CO₂ Brayton Cycle

Supercritical carbon dioxide（S-CO₂）power cycle has higher cycle efficiency than steam Rankine cycle and helium Brayton cycle at medium turbine inlet temperature（723-923 K）.At the same time,it has the advantages of compact cycle structure and small floor area,therefore it can be used as an alternative for the energy conversion system of the Gen-IV reactors.At present,this cycle has been studied as a direct cooling and indirect cooling energy conversion system,the cycle thermal efficiency is the highest when coupled with the lead-cooled fast reactor.Dual fluid reactor（DFR）is a conceptual design of molten salt lead-based reactor.It uses Pu Cl₃-UCl₃ as fuel and lead as coolant,which has high power density,high fuel utilization,high efficiency,compact structure and inherent safety under accident conditions.Therefore,the work of this paper is to select DFR reactor as heat source and S-CO₂ Brayton cycle as indirect energy conversion system,and establish a transient coupling analysis model in Open Modelica software environment based on Modelica language,then the calculation and analysis are carried out to grasp the dynamic response characteristics of the core and S-CO₂ Brayton cycle of the DFR system when the operating conditions are introduced.The research of this subject is of great theoretical guiding significance for the future research of DFR control strategy and accident analysis.The S-CO₂ fluid property database is based on the fluid thermodynamics and transport property database REFPROP published by the National Institute of standard and Technology.In the transient analysis model,the core module mainly includes one-dimensional point reactor physical model and one-dimensional core fuel and coolant thermal hydraulic model,S-CO₂ Brayton cycle energy conversion model.The latter mainly includes Pb-CO₂heat exchanger model,turbine model,compressor model,recuperator model and precooler model.This article first carried out steady-state and transient analysis on a separate system model.For example,in the reactor module,the number of nodes,solver settings,PPU parameters and fuel type are evaluated;in the S-CO₂ Brayton cycle module,the model is first verified in steady state and transient state.Based on the verified model,the highest pressure and highest temperature of the cycle were evaluated to determine the selection of some key parameters.Finally,the coupling calculation of reactor and S-CO₂ Brayton cycle is carried out and then analyze from the perspective of safety.This work also proves Open Modelica software can be an important tool for further research on the concept of nuclear reactor with S-CO₂ Brayton cycle.