Impact Simulation on a Nuclear Waste Container

By Joonhong Lim

Abstract

Nuclear power generation produces large amount of high-level nuclear waste that must be stored safely for many years. One proposed solution is to insert the waste material in specially-designed containers that will be stored in tunnels for very long periods. Like many other proposed solutions, this approach presents difficult challenges. First, the nuclear waste continues to produce heat, and this is expected to raise the containers' temperature for the first 100 years. Because of the high radioactivity, it is expected that the emplacement tunnels will be closed, and access to humans will be either prohibited or severely restricted. The combined effects of time and temperature could cause the deterioration of the emplacement tunnels, resulting in rock blocks falling on such containers.

Obviously, the consequences of such impacts could be disastrous. Studying the behavior of such containers experimentally is possible, but it requires one to address many combinations of parameters. Naturally, such an experimental study would be very lengthy and expensive. Alternatively, one could perform "numerical experiments" of a broad range of relevant conditions to assess the behavior and performance of such containers, and derive recommendations for their design, production and use.

This research focused on assessing a particular type of nuclear waste storage container under the combined effects of temperature and localized impacts at various locations. Both the complicated external container barriers, as well as its internal parts, were investigated for such conditions. Parametric numerical simulations were performed to define the overall performance, and to identify possible failure conditions. The parameters addressed in the study included the following: Structural and material parameters for the proposed container, rock size, rock type, rock shape, drop height, impact conditions (e.g., flat impact, point impact, line impact, etc.). As a result of these simulations, it was possible to identify likely undesired conditions that must be addressed to insure the safety of the container.