Modeling Research on PWR Fuel Assembly Lateral Non-linear Characteristics

In PWR fuel assembly design, the fuel rod is usually clamped by grids to maintain its position laterally and axially. Fuel rod may slide relative to grid when fuel assembly bows, which brings non-linear characteristics to fuel assembly laterally. This paper includes the analysis of typical fuel assembly grid to fuel rod clipping system. Based on the analysis and the test, the characteristic curve of bending of the clamping system is considered as the combination of several sliding elements and spring elements, mechanical simulation of the clamping system is consequently established. Finally, the comparison of calculation results and test results are presented, thus the mechanical simulation is qualified. The model of clamping system is adopted by fuel assembly lateral model, which exhibit a good accordance to fuel assembly lateral pluck test results.