Typical Conditions Of China Experimental Fast Reactor Grid Plate Header Fluid Dynamics Analysis

The core of China Experimental Fast Reactor (CEFR) consists of fuel assemblies, control rod assemblies, steel assemblies, boron assemblies and spent fuel assemblies. Considering the great difference of these assemblies in heat generation, optimal coolant flowrate distribution is designed for not only assuring the assemblies temperature not exceed limitation value but also obtaining higher core outlet coolant temperature to get higher heat efficiency. The component which offers flow distribution is the grid plate under core.Primary coolant pipe double-ended rupture event is one of the most serious loss of coolant DBA. Because flow in primary coolant loop of main heat transfer systerm changes drastically during the event, and even local flow reverse occurs quickly, studying all grid plate outlets coolant flow situation, which affects core assemblies coolant flow distribution and core safety, then becomes very important.This paper studies fluid dynamics situation of grid plate under full power condition and one primary pipe rupture event by means of modern computational fluid dynamics technology— CFX program, that is,creating model, defining domain, creating mesh, defining boundery condition, and so on. The "momentum source" method of CFX is used to model the main resistance between inlet and each outlet flowing, which solves the problem that many flowing interact each other during transient development.The results show that: mass flow distribution in 37 sleeves corresponding to 37 small grid plates meets with the design value, pressure drop is little and velocity vector field is regular in grid plate under rated power condition; during primary coolant pipe rupture accident, core flow redistribution has little change in all core assemblies, pressure dropgradient is obvious in grid plate, pressure near the two unruptured pipes is higher than that near the ruptured pipe, with the time passes by, inner mean pressure and inner pressure gradient reduce gradually, inner velocity vector field is comprehensive and has great change.The total mass flow of reactor core is similar to the result of the system code calculation, so this analysis can be used to support the CEFR safety assessment.