Experimental research on assembly section stiffness and bending stiffness for sodium-cooled fast reactor

China Fast Reactor (CFR) is under construction, and the section stiffness and bending stiffness of CFR assemblies remain unknown and need to be investigated to support the core restraint system design and reactivity safety assessment. In this study, assembly compression tests were performed with three types of test samples. With the compression load varying from 0 to 6 kN, the compressive deformations were measured and the section stiffness were obtained. In assembly bending tests, there were two types of assemblies considering different spike clearances, and the horizontal loads from 400 N to 1900 N were applicable to the upper-load-pad, lower-load-pad and mid-fissile-region level of the assemblies. Assembly deflections were measured and correlations for the load-deflection ratio were proposed. Comparison of theoretical and experimental bending stiffness were carried out, which indicated that the spike clearance has to be taken into consideration in the assembly deformation analysis codes.