Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB

Abstract

a b s t r a c tThe neutron irradiation-induced structural changes in nuclear grade graphites PCEA and PCIB were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and electron energy loss spectroscopy (EELS). The graphite samples were irradiated at the Advanced Test Reactor at the Idaho National Laboratory. Received doses ranged from 1.5 to 6.8 displacements per atom and irradiation temperatures varied between 350 C and 670 C.XRD and Raman measurements provided evidence for irradiation induced crystallite fragmentation, with crystallite sizes reduced by 39e55%. Analysis of TEM images was used to quantify fringe length, tortuosity, and relative misorientation of planes, and indicated that neutron irradiation induced basal plane fragmentation and curvature. EELS was used to quantify the proportion of sp 2 bonding and specimen density; a slight reduction in planar-sp 2 content (due to the buckling basal planes and the introduction of non-six-membered rings) agreed with the observations from TEM.

Ion-beam-assisted characterization of quinoline-insoluble particles in nuclear graphite

“…Furthermore, given the need of simulating and predicting nuclear graphite's behavior, typical microstructures and their responses to irradiation should be fully understood. There have been many studies on graphite microstructures that irradiated with neutrons [7][8][9][10], electrons [11][12][13] and ions [14][15][16]. Irradiation-induced effects on the atomic level, including decreasing of the sp 2 content, fragmentation and distortion of graphite basal planes, decreasing of a-lattice parameter, increase of c-lattice parameter, dislocation dipole and climb of dislocations in graphite lattice, were reported.…”