Peridynamics and finite element simulations of TRISO Fuel under extreme operating conditions
Author(s)
Battistini, Angelo
Type
Thesis
Abstract
Tristructural isotropic coated particle fuels (TRISO CPF) are developed for use in high-temperature gas-cooled reactors (HTGR), producing gas for nuclear cogeneration in industrial settings and hydrogen production. The key safety objective of TRISO CPF is to prevent fission product release throughout their lifetime, under both operational and accident conditions. TRISO particles consist of four layers on spherical fuel kernels made of fissile (or fertile) material: a low-density pyrolytic carbon buffer, an inner dense pyrolytic carbon (IPyC), a silicon carbide (SiC) layer, and an outer pyrolytic carbon (OPyC) layer. The combination of materials with different thermo-mechanical properties can generate stresses within the layers, leading to cracks that could compromise fission product containment.
A non-local bond-based peridynamics model implemented in the Abaqus finite element code, now named Peridynamics Crack Onset and Retardation Engine (Peri-CORE), has been comprehensively verified and validated (V&V) prior to its use for TRISO particle transients. The V&V campaign tested new subroutines to calculate stresses and strains, benchmarking Peri-CORE against finite element models. It confirmed Peri-CORE’s precision in stress prediction and identified a mesh-related load overprediction (up to 40%), quantified through mesh sensitivity analyses. It also found the root cause of localised stress concentrations leading to preferential crack initiation in TRISO.
Peri-CORE modelling of TRISO was preceded by a finite element study of its manufacturing process, which revealed significant residual stresses (up to 100 MPa compressive in the SiC layer) and a gap between the kernel and buffer, both helping alleviate thermal expansion mismatch in reactor operations. Peri-CORE was then used to simulate TRISO under extreme temperature variations, confirming that, once residual stresses are accounted for, TRISO failure above 1800 °C is unlikely to be caused by thermo-mechanical effects.
A non-local bond-based peridynamics model implemented in the Abaqus finite element code, now named Peridynamics Crack Onset and Retardation Engine (Peri-CORE), has been comprehensively verified and validated (V&V) prior to its use for TRISO particle transients. The V&V campaign tested new subroutines to calculate stresses and strains, benchmarking Peri-CORE against finite element models. It confirmed Peri-CORE’s precision in stress prediction and identified a mesh-related load overprediction (up to 40%), quantified through mesh sensitivity analyses. It also found the root cause of localised stress concentrations leading to preferential crack initiation in TRISO.
Peri-CORE modelling of TRISO was preceded by a finite element study of its manufacturing process, which revealed significant residual stresses (up to 100 MPa compressive in the SiC layer) and a gap between the kernel and buffer, both helping alleviate thermal expansion mismatch in reactor operations. Peri-CORE was then used to simulate TRISO under extreme temperature variations, confirming that, once residual stresses are accounted for, TRISO failure above 1800 °C is unlikely to be caused by thermo-mechanical effects.
Date Issued
2024-08-14
Date Awarded
2025-03-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Wenman, Mark
Haynes, Thomas
Sponsor
Department for Business, Energy, and Industrial Strategy
UKRI
Grant Number
UKRI - EP/S023844/1
Publisher Department
Department of Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)