Study on the Multi-Physics Field Coupling Behavior of Four-Petal Fuel Rods Contact Under Normal and Ria Conditions

Abstract

This study is based on ABAQUS-STAR CCM+ different coupling modes, to investigate the 3×3 assemblies flow heat transfer and irradiation mechanics coupling behaviors under power-up, irradiation contact, and reactivity insertion accident (RIA) conditions. The results indicate that the different twist petal structures, flow areas, and cosine heat release mode along the axial direction led to complex flow and heat transfer behaviors along the radial direction. Different from the power-up stage, the heat transfer coefficient (HTC) in the irradiation stage decreases slightly, and irradiation swelling increases the tendency of the fuel to expand outward, leading to a significant stress-strain increase in the contact regions. The peak stress reaches 383.143 MPa, and the deformation of the contact regions under mutual extrusion is also different. During the RIA stage, the plastic strain in the contact regions reaches 0.006, which cannot return to the level before the accident even after the power decreases.

Keywords: Small-scale nuclear reactor, Different coupling modes, Multi-rod contact, Normal and RIA conditions, Contact extrusion