Effects of phosphorous-doping and high temperature annealing on CVD grown 3C-SiC
2012 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 251, no SI, 191-202 p.Article in journal (Refereed) Published
The integrity and property behavior of the SiC layer of the Tr-isotropic (TRISO) coated particle (CP) for high temperature reactors (HTR) are very important as the SiC layer is the main barrier for gaseous and metallic fission product release. This study describes the work done on un-irradiated SiC samples prepared with varying phosphorus levels to simulate the presence of phosphorus due to transmutation. Si-30 transmutes to phosphorous (P-31) and other transmutation products during irradiation, which may affect the integrity of the SiC layer. The P-doping levels of the SiC samples used in this study cover the range from 1.1 x 10(15) to 1.2 x 10(19) atom/cm(3) and are therefore relevant to the PBMR operating conditions. Annealing from 1000 degrees C to 2100 degrees C was performed to study the possible changes in nanostructures and various properties due to temperature. Characterization results by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM). transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM), are reported in this article. As grain boundary diffusion is identified as a possible mechanism by which Ag-110m, one of the fission activation products, might be released through intact SiC layer, grain size measurements is also included in this study. Temperature is evidently one of the factors/parameters amongst others known to influence the grain size of SiC and therefore it is important to investigate the effect of high temperature annealing on the SiC grain size. The ASTM E112 method as well as electron back scatter diffraction (EBSD) was used to determine the grain size of various commercial SiC samples and the SiC layer in experimental PBMR Coated Particles (CPs) after annealing at temperatures ranging from 1600 degrees C to 2100 degrees C. The HRTEM micrograph of the decomposition of SiC at 2100 degrees C are shown and discussed. Nanotubes were not identified during the TEM and HRTEM analysis although graphitic structures were identified. The preliminary conclusion reached is that the P-content at these experimental levels (1.1 x 10(15) to 1.2 x 10(19) atom/cm(3)) does not have a significant influence on the nanostructure of SiC at high temperatures without irradiation.
Place, publisher, year, edition, pages
Elsevier , 2012. Vol. 251, no SI, 191-202 p.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-85199DOI: 10.1016/j.nucengdes.2011.09.066ISI: 000309496600024OAI: oai:DiVA.org:liu-85199DiVA: diva2:566644
Funding Agencies|PBMRs Fuel Optimization Technology Programme||2012-11-092012-11-092014-10-08