Crushing Strength of High-Temperature Gas-Cooled Reactor Fuel Particles

The whole-particle crushing strengths of high-temperature gas-cooled reactor fertile and fissile coated particles were measured and correlated with fabrication procedures. The crushing strength of Biso-coated fertile particles was increased by the following factors:

1. Increasing the outer coating thickness by 10 µm increased strengths by 0.3 lb (1.3 N) for annealed particles and by 0.5 lb (2.2 N) for unannealed particles.
2. An 1800°C postcoating anneal increased strengths by 1 lb (4.4 N) for particles with thick outer coatings and by 2 lb (8.9 N) for particles having thin coatings.
3. Increasing the inner coating density by 0.1 g/cm³ increased strength by 0.6 lb (2.7 N).

The crushing strength of Triso-coated fissile particles was proportional to the thickness of the SiC coatings, and strength decreased on annealing by ∼0.2 lb (0.9 N) when a porous plate was used to distribute the coating gas and by ∼1.5 lb (6.7 N) when a conical gas distributor was used. The strengths of fertile and fissile coated particles as well as uncoated kernels appear adequate to allow fuel fabrication without excessive particle damage.