A Feasibility Study for the Development of Alternative Methods to Treat a Spent TRISO Fuel

The main objectives of a TRISO treatment are to effectively breach and separate the carbon and SiC layers composing the TRISO particles. The reported technologies used to treat a spent TRISO fuel are almost identical, involving a final wet chemical process under which crushed TRISO fuel is processed to separate the coating layer fines from the kernel. Also, these processes are mainly powder processes with a secondary waste generation, and they require a corrosive solution as well as complex processing steps.

Hence, two innovative processing concepts are proposed in this investigation; namely, a thermal shock and a pyrochemical process to breach the coating layers of the TRISO particle with a minimal amount of secondary waste. The preliminary results showed that the chemical vapor deposition (CVD) SiC layers, as pseudo coating layers of the TRISO fuel, exhibited very robust thermal shock behaviors even at 1300°C of T, but a cyclic thermal shock caused a drastic degradation of their hardness. Also, it was confirmed that the CVD SiC as well as the glassy carbon rod can be breached by a chemical reaction in a molten salt with Mg and Li, respectively. Therefore, the proposed technologies are found to be very promising for treating a spent TRISO fuel without a considerable generation of secondary wastes.