Determining time of the complete relaxation of contact interaction between the fuel clad and the elastic spacer grid cell in WWER fuel assembly

Authors: Gusev M.P., Danilov V.L., Yakovlev V.Yu. Published: 06.10.2015
Published in issue: #5(104)/2015  

DOI: 10.18698/0236-3941-2015-5-62-71

Category: Power Engineering | Chapter: Nuclear Power Plants, Fuel Cycle, Radiation Safety  
Keywords: fuel assembly, contact force relaxation, fuel rod, spacer grid

Fuel rods and spacer grids are the main elements of the power reactor fuel assembly. The fuel rods are fixed inside the spacer grid cells with negative allowance. Negative allowance produces contact forces between the fuel rod and the spacer grid cell. Contact forces are reduced to zero during the fuel assembly’s operating because there are high temperature and intense neutron fields in the power reactor core. Reducing contact forces is the relaxation of contact interaction. The relaxation of contact interaction only due to temperature effects is considered. The relaxation causes slippage between the fuel rod and the spacer grid cell. Slippage time determination and and finding solution to the problem of relaxation are urgent because slippage of the fuel rods causes the intensive process of fuel clad fretting wear, as well as the reduction of fuel assembly stiffness.


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