乏燃料贮存格架跌落事故冲击分析和试验验证

乏燃料贮存格架是核电厂贮存乏燃料的重要设备，在满载条件下和地震/跌落事故中，都应保持稳定和安全状态．本文基于LS-DYNA对乏燃料贮存格架进行了跌落事故冲击分析，考虑了最重重物从可能最高处意外跌落的情况．分析时考虑了碰撞、几何大变形、材料非线性等非线性因素．分析发现，浅跌落情况下贮存格架变形较大，但为局部变形，冲击载荷不影响贮存格架的安全功能．深跌落情况下，组件跌落在支座上方时支座承受的载荷最大，并在许用载荷范围内．为确保核电厂安全性和可靠性，基于分析得到的现象，设计和开展了乏燃料贮存格架浅跌落和深跌落试验．试验采用了等比例贮存腔和真实燃料组件的管座．同时对试验件进行了跌落分析，并与试验结果进行了对比，验证了分析技术的保守性和准确性．掌握的分析技术可应用于所有压水堆核电站乏燃料贮存格架的跌落事故分析．

Drop Accidents Impact Analysis of Spent Fuel Racks and Experimental Validation

Spent fuel racks are important facilities to store the spent fuel in nuclear power plant (NPP). They should be stable and safe for all conditions of rack fill and seismic loading or drop accidents. In this paper, the nonlinear analysis is performed for the heaviest impact drop accident from the maximum possible height by LS-DYNA, in which the nonlinearities from the impact contact, the geometric large deformation, and the material nonlinearity are considered. It indicates that the deformation of rack is large but localized in the shallow drop event. The impact load doesn’t affect the safety function of rack. The rack support force reaches its maximum when the dropped fuel hits the corner of the rack base-plate, but is still within the allowable load range in the deep drop event. In addition, based on the phenomenon obtained from the analysis, the shallow drop and the deep drop validation experiments with the full size storage chamber and the real fuel assembly’s lower header are designed and performed, in order to ensure the security and reliability of nuclear power. The drop accidents impact analysis of experimental situation is carried out. And the comparison between the analysis and experiments verified the conservatism and accuracy of the analysis. The technology can be applied to drop accident analysis of spent fuel storage rack for all PWR nuclear power plants.