Fission Gas Release from High Burn-Up Carbide Fuel Kernels. Dragon Project Report

The stable fission gas release from fuel kernels in intact coated particles has been measured by cracking open the coatings after irradiation and counting the Kr⁸⁵ released. Results from UC₂ showed a marked increase in Kr⁸⁵ release from the kernel to 40%) between 4.3 and 6,6% burn-up, release levels being relatively insensitive to irradiation temperature in the range 925 to 1 275°C. A wide variety of other carbide kernels below 3% burn-up gave release levels of less than 2% over a wide temperature range. Results from sintered (ThU)C₂ showed an increase in release with burn-up, however, temperature and burn-up effects cannot be separated because of the large range of irradiation temperature. The pressure exerted on the UC₂ particle coatings has been measured by a radiographic technique as 11-23 atmospheres at an irradiation temperature of 1000°C. (author)