SEM analysis of the microstructure of the layers in triple‐coated isotropic (TRISO) particles

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Abstract
One of the new inherently safe designs in nuclear reactors is the pebble bed modular reactor (PBMR). In this high temperature reactor the fuel is in the form of small multilayered spheres called triple‐coated isotropic (TRISO) particles. These coated particles consist of a UO 2 kernel surrounded by four layers, which are all chemical vapour deposition (CVD) deposited. The layers are a buffer graphite layer next to the kernel followed by an inner pyrolytic carbon layer (IPyC), a SiC layer and finally an outer pyrolytic carbon layer (OPyC). This investigation focuses on the microstructure of the particles specifically in relation to their functions. Because the coated particles operate in a very harsh environment (e.g. high temperatures with repeated rapid cooling and heating‐up times, high flux neutron irradiation, containment of the radioactive fission products) the microstructure and composition of the layers are extremely important to preserve the integrity of the particles. In this investigation the microstructures of the different coated layers are investigated by high‐resolution SEM. Copyright © 2010 John Wiley & Sons, Ltd.

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