Analysis on Dropping Accidents of Fresh Fuel Cask in HTGR

The fuel of HTGR is made of some spherical fuel elements with diameter of 60 mm. The cask of fresh fuel is used to temporarily store and transport such a kind of new spherical fuel elements, and it may drop during transport. The dropping process can be simulated by two ways. The first is the coupled Euler-Lagrange (CEL) method, in which the new fuel elements are taking as fluid and can be considered explicitly. The second is referred to as the equivalent mass method. In the method, the cask and the new fuel are not considered individually, and the mass of the new fuel elements is averagely allocated to the bottom head of the cask. The simulating result shows that the CEL method can describe the flow and inertial effects of the new fuel elements in the dropping process, and the lateral fluid dynamic pressure generated by fuel elements to the cask. The impact effect can be fully considered in the equivalent mass method. Results show that the impact force is stronger and the contact time is shorter than that of the CEL method. Finally, parameters of equivalent fluid in the CEL method are discussed. And the results show that the fluid model is reasonable. In one word, calculation results of the two methods can be combined in structural design, which will give a more reasonable design.