A Linear-Elastic Peridynamic Model for the Fracture of Coated Particle Fuel under Thermal Loads during Idealised Early Life Operation

Thomas Haynes

A. Battistin, Mark R. Wenman

Imperial College London


Coated particle fuels (CPF) such as tristructural-isotropic (TRISO) are targeted for use in high temperature gas-cooled reactors (HTR) which offer the potential for increased thermodynamic efficiency and heat supply for chemical process applications such as hydrogen production.

A linear-elastic peridynamic model for a single particle of TRISO fuel has been built using a bond-based technique implemented in the finite element code ‘Abaqus’. The model is able to consider the elastic and thermal strains in each layer of the particle and to simulate potential fracture both within and between layers.

During an idealised raise to normal operating power for a kernel to 0.3 W and a bulk fuel temperature of 1305 K, cracks initiate in the buffer near to the kernel-buffer interface and propagate towards the buffer-iPyC coating interface, but do not penetrate the iPyC and containment of the fission products is maintained. In extreme accident conditions, at around 600% power during a power ramp at 100% power per second, cracks were predicted to form on the kernel side of the kernel-buffer interface, opposite existing cracks in the buffer. These were predicted to then propagate slowly. The SiC coating was predicted to subsequently fail at a power of 940%, with cracks formed rapidly at the iPyC-SiC interface and propagating in both directions. These would overcome the containment to fission gas release offered by the SiC ‘pressure vessel’. The extremely high power at which failure was predicted indicates the potential safety benefits of the proposed HTR design.

Event Timeslots (1)

Thursday – 16th September 2021
Thomas Haynes