Increasing Safety and Reducing Environmental Damage Risk from Aging High-Level Radioactive Waste Tanks

Abstract

There exists a paramount need for improved understanding the behavior of high-level nuclear waste containers and the impact on structural integrity in terms of leak tightness and mechanical stability. The current program, which at the time of this writing is in its early stages, aims to develop and verify models of crack growth in high level waste tanks under accidental overloads such as ground settlement, earthquakes and airplane crashes based on extending current fracture mechanics methods. While studies in fracture have advanced, the mechanics have not included extensive crack growth. For problems at the INEEL, Savannah River Site and Hanford there are serious limitations to current theories regarding growth of surface cracks through the thickness and the extension of through-thickness cracks. We propose to further develop and extend slip line fracture mechanics (SLFM, a ductile fracture modeling methodology) and, if need be, other ductile fracture characterizing approaches with the goal of predicting growth of surface cracks to the point of penetration of the opposing surface. We also aim to quantify the stress and displacement fields surrounding a growing crack front (slanted and tunneled) using generalized plane stress and fully plastic, three-dimensional finite element analyses. Finally, we will quantify the fracture processes associated with the previously observed transition of stable ductile crack growth to unstable cleavage fracture to include estimates of event probability. These objectives will build the groundwork for a reliable predictive model of fracture in the HLW storage tanks that will also be applicable to standardized spent nuclear fuel storage canisters. This predictive capability will not only reduce the potential for severe environmental damage, but will also serve to justify life extension through retrieval of waste. This program was initiated in November of 2001.