Degradation of Concrete Structures in Used Nuclear Fuel Dry Cask Storage Systems

The extended long-term storage of used nuclear fuel will require increased reliance on dry cask storage systems. Reinforced concrete serves as the primary structural, physical protection, and shielding material in many of these systems. In addition, all of the independent spent fuel storage installation (ISFSI) designs place the storage modules on reinforced concrete pads. In all of these applications, the concrete components perform important safety functions, and their ability to continue to perform these functions during the period of extended operation must be evaluated as a part of the license renewal process for ISFSIs. Concrete has been found to be subject to a number of aging-related degradation processes, and many of these processes have been observed in ISFSI components and other nuclear plant structures. As part of the U.S. Department of Energy’s Used Fuel Disposition Campaign Research and Development program, Argonne National Laboratory has prepared a report titled “Managing Aging Effects on Dry Cask Storage Systems for Extended Long-Term Storage and Transportation of Used Fuel, Rev. 1.” This report includes a proposed Concrete Structures Monitoring Program to manage the time-dependent degradation of concrete structures in ISFSIs. The recommended program is largely a condition-monitoring based on periodic visual inspections as well as sampling and testing of groundwater chemistry and, if applicable, monitoring the effectiveness of cathodic protection systems embedded in concrete structures.