Numerical simulations of nuclear fuel reprocessing plant subjected to the free drop impact of spent fuel cask and fuel assembly

Abstract

This paper aims to numerically evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA). Based on our recently conducted 1/3 scaled free drop test of SFC, the adopted numerical algorithms, constitutive models and parameters are verified and further applied to the refined numerical simulations of the prototype plant under accidental impact. Total nine free drop scenarios are considered, including the SFC drop onto the center of the removable slab, groove of the removable slab and center of the inverted U-shaped slab/autoclaved aerated concrete (AAC) composite protective structure as well as the FA drop onto the center of the bottom slab in spent fuel pool. The damage and vibrations of nuclear fuel reprocessing plant, as well as the energy absorption capacities of the trailer, AAC blocks layer, waterproof steel liner and water within the loading shaft are assessed. It indicates that, (i) the free drop impact of SFC results in perforation of the impacted region and extensive damage of the removable slab, while the free drop impact of FA only induces a shallow cratering of the bottom slab in spent fuel pool; (ii) the trailer absorbs about 90% of the impact energy and reduce the damage of the impact region effectively, but the overturn of which may result in the tip-over impact of SFC on the surrounding walls; (iii) when considering the effects of the waterproof steel liner and water within the loading shaft, the impact energy of SFC reduces by at least 54%, and the bottom slab is effectively protected; (iv) the vibrations caused by the impact of FA are slighter than that caused by the impact of SFC, and the trailer reduces the peak accelerations of nuclear fuel reprocessing plant by 26.3%–68.91%.