NuFuel & MMSNF 2015

First Workshop on Research into Nuclear Fuel in Europe
and Materials Modeling and Simulation for Nuclear Fuels Workshop
Karlsruhe, Germany, November 16th to 18th, 2015

Updated: Tue 08 Dec 2015, 14:27

Talk 6.2: Explicit fracture models of nuclear fuel pellets using peridynamics

M. Mella1 and Mark Wenman2 *^
  • 1: Nuclear Department, Defence Academy of the UK, HMS Sultan, Military Road, PO12 3BY.
  • 2: Department of Materials and Centre for Nuclear Engineering, Imperial College London, London. SW7 2AZ.
  • *: Presenting author.

Abstract

Three dimensional models of explicit cracking of nuclear fuel pellets for a variety of power ratings have been explored with peridynamics, a non-local, mesh free, fracture mechanics method. These models were implemented in the explicitly integrated molecular dynamics code LAMMPS, which was modified to include thermal strains in solid bodies. The models of fuel fracture, during initial power transients, are shown to correlate with the mean number of cracks observed on the inner and outer edges of the pellet, by experimental post irradiation examination of fuel, for power ratings of 10 and 15 W g-1 UO2. The models of the pellet show the ability to predict expected features such as the mid-height pellet crack, the correct number of radial cracks and branching of radial cracks as they reach the outer edge of the pellet. This work presents a modelling alternative to empirical fracture data found in many fuel performance codes, which requires just one parameter of fracture strain. Weibull distributions of crack numbers were fitted to both numerical and experimental data using maximum likelihood estimation so that statistical comparison could be made. The findings show P-values of less than 0.5% suggesting an excellent agreement between model and experimental distributions.