Yuanzineng kexue jishu (Jan 2023)
Numerical Simulation of Cross Flow Characteristic for Annular Fuel Mixed Core
Abstract
Annular fuel is a new type of pressurized water reactor fuel with inner and outer dual coolant channels. Selecting the actual reactor and annular fuel pilot assembly to form a mixed core to carry out irradiation test is one of the important links in the research and development of annular fuel. Through the operation test in the actual reactor, the structural design and thermal safety performance of the fuel assembly can be fully verified, laying the foundation for the subsequent construction of the annular fuel reactor and engineering applications. The annular fuel mixing core has open flow channels, and the cross flow characteristics have an important impact on the thermal safety of the original core. Therefore, a 3×3 annular fuel mixed core was established based on computational fluid dynamics method. Taking the local resistance characteristics of the two assemblies, the cross velocity field of the mixed core, the flow deviation between inlet and outlet of each assembly in the mixed core, and the flow deviation of each grid section as the evaluation indicators, the cross-flow characteristics of the annular fuel mixed core were analyzed in detail. The results show that the smaller equivalent diameter of the annular fuel outer channel has a retarding effect on the cross flow of the mixed core, so that the deflection effect of the original core mixing vane on the coolant is greatly weakened at the interface of the mixed core assemblies. It effectively eliminates the cross flow caused by the mixing vane. Meanwhile, under the mixed core condition, the coolant flow rate of the original core fuel is only in the 5th, 7th, and 9th grid sections, which is smaller than that of the annular fuel, and the rest of the grid sections are larger than the annular fuel. The maximum relative deviation of the flow rate of each spacer grid section in the axial direction is 12%, the average relative deviation of the flow rate in each spacer grid section is about 9%, and the relative deviation of the flow rate between inlet and outlet of each assembly is less than 1.8%. The coolant flow distribution of the mixed core rod bundle is uniform and there is no significant cross flow.
