Design and Verification of Discontinuous Medium Buffer for Nuclear Spent Fuel Transport Casks

The nuclear spent fuel transport cask is a specialized equipment for safe transportation of radioactive materials, and the buffers on both sides of the transport cask are mainly used to protect the transport cask from vibration and impact caused by accident conditions during transportation. They are key components that determine whether the entire assembly can meet safety performance requirements. After being impacted, they absorb impact energy to ensure the integrity of the spent fuel transport cask structure. The buffer is mainly composed of buffering material and outer wrapping material, and the buffering effect mainly depends on the internal buffering material. The widely used wood cushioning materials are limited by factors such as grain structure, moisture content, and a single energy consumption mechanism, making it difficult to further improve cushioning performance. To address these issues, this paper proposes a design method for a non-continuous medium buffer for nuclear spent fuel transport casks. Firstly, a coupling model was established based on the continuous-discontinuous coupling calculation method, the internal structure of the buffer was optimized, and drop simulation calculations on the buffer filled with different buffer materials, thin-walled spherical shells with different wall thicknesses, and thin-walled spherical shells with different particle sizes were conducted. The middle position of the model was used as the measurement point, and the peak drop acceleration was used as the evaluation index to explore the influence of different characteristic parameters of the buffer material to investigate the buffering performance of the buffer, and obtain the parameter scheme with the best buffering effect. Secondly, a drop test platform was established to conduct drop impact tests on scaled models filled with different cushioning material schemes. The transient impact responses collected from different schemes were compared to verify the accuracy of the coupled simulation. The results show that the overall trend of change is consistent with the simulation. Finally, a 9-meter drop test was conducted on the thin-walled spherical shell medium scheme with a wall thickness of 0.3 mm and a particle size of 32 mm, which had the best buffering performance, according to relevant design standards. The acceleration of the prototype under this condition is calculated to be 56.1g, the shear stress at the containment boundary is 215 MPa, and the axial stress is 867 MPa, all of which meet the requirements of relevant standards. This study provides new ideas for the design of spent fuel transport cask buffers and has broad application prospects for improving the buffering performance of spent fuel transport cask buffers during drops.