International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

Diffusion of Fission Products through Silicon Carbide

E. Friedland, N.G. Van der Berg, J.B. Malherbe, and T. Hlatshwayo

Physics Department, University of Pretoria, South Africa

Corresponding Author: erich.friedland@up.ac.za

Fuel elements of modern high-temperature nuclear reactors are encapsulated by CVD-layers of pyrolitic carbon and silicon carbide to reduce fission product release. The aim of this study is to obtain information on volume and grain boundary diffusion as well as on the influence of radiation damage. For this purpose relevant isotopes were implanted with a fluence of 2 x 10¹⁶ cm ^-2 in poly and single crystalline SiC samples at temperatures ranging from room temperature to 900K. Diffusion coefficients were obtained from the broadening of the implantation profiles after isochronal and isothermal annealing studies up to 1900K, using RBS analysis in conjuncture with α-particle channeling spectrometry. Structural information on the implanted samples was obtained by scanning and transmission electron microscopy. As the surface region of the room temperature implants was completely disordered, the initial profile broadening could be used to study diffusion in amorphous silicon carbide. Comparison of profile broadening in annealed single and poly crystalline samples yielded information on the relative importance of volume and grain boundary diffusion. Information on the influence of radiation damage was extracted by comparing results from samples implanted at room and elevated temperatures.

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