Irradiation performance of experimental fuel particles coated with silicon-alloyed pyrocarbon: A review

• Published in: Journal of nuclear materials 1983, Vol.113 (1), p.81-100
• Main Author: Bullock, R.E.
• Format: Article
• Language: English
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/0022-3115(83)90170-8

A review has been conducted on the use of silicon-alloyed pyrocarbon (Si-PyC) as an improved coating material for the two types of fuel particles used in the cores of high-temperature gas-cooled reactors. Based on recent data from extensive irradiation testing and postirradiation annealing of such experimental fuel particles, it is concluded that Si-PyC coatings offer considerable promise as replacements for the standard pure pyrocarbon (PyC) coatings used on thorium-based fertile fuels that have BISO coating designs. The primary advantage here is improved retention of fission products from bred U-233, with diffusion coefficients being as much as 100 times smaller for Si-PyC than for PyC. However, there is no significant improvement in mechanical performance of Si-PyC coatings over standard PyC coatings under irradiation. As a result, there is no incentive for using these coatings on TRISO particle designs of the type used on uranium-based fissile fuels, because here a silicon carbide barrier layer provides superior fission-product retention.