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

Poster 6.1: Phase-field model to simulate pore morphology, migration and consequences in MOX fuels

Michael J. Welland
  • Fuel and Fuel Channel Safety Branch, Canadian Nuclear Laboratory, Chalk River, Ontario, Canada

Abstract

A phase-field model is developed to simulate pore morphology, migration, and consequences in MOX fuels. The model describes pore evolution driven by vaporization of matrix material at the hot side of the pore and condensation on the cold side, propagating the pore up the temperature gradient. Non-congruent vaporisation of the multi-component matrix constituents redistributes U and Pu, resulting in enrichment of Pu towards the fuel centreline in MOX fuels. The local O/M has a strong effect on pore migration due to large variations in UO3 partial pressure. The gas inside the pore is not in mechanical equilibrium with the surrounding matrix, and the pore is observed to assume a lenticular shape with the minor axis oriented approximately parallel to the temperature gradient.

The model couples multi-component, multi-phase diffusion, structural mechanics, and interfacial energy. The simulation is used to examine classical theories for pore migration velocity as a function of temperature and temperature gradient, which provides information on the extent of the columnar grain zone and central void.