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Description
In applications like nuclear reactors or particle accelerators, mechanical components near a source of radiation develop radiation damage. This typically means a change in tensile properties and fracture toughness, which depends on the radiation dose (commonly measured in ‘displacements per atom’, or DPA). In addition to such radiation hardening, radiation damage can also cause swelling, which in turn can lead to additional stresses. These effects need to be taken into account in the design of components, to make sure they do not fail.
In this work, the risk of failure for a power dump is assessed. The purpose of this power dump is to absorb gamma radiation with approximately 1 MW of power. The radiation is emitted from a target that is irradiated by an electron beam. The power dump’s primary constituent material can become very brittle after irradiation, so fast fracture was determined to be the most likely failure mechanism.
To ensure the structural integrity of this component in its radiation environment, FEM analysis in combination with Monte Carlo radiation transport codes was used. Our approach consisted of first modeling the irradiation parameters of the system using a radiation transport code (FLUKA). This includes accurate modeling of the radiation source term. From this the heat load and radiation damage production (DPA/s) were obtained. As a second step, these spatially dependent results were mapped to a detailed 3D FEM model (COMSOL). The FEM model has appropriate boundary conditions relating the DPA to swelling strain, and temperature to mechanical strain. This allowed assessment of stress-distributions over time. Some changes were made in the design to minimize stresses. By assessing and evaluating a conservative fast fracture criterium, it was then determined that the component is not likely to fail.
| Scientific Topic 6 | Radiation damage to materials |
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