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 3.1: Separated effect studies: a necessary experimental approach to understand the fuel behavior under in-pile irradiation

Claire Onofri1a, C. Sabathier1, H. Palancher1, M. Legros2
  • 1: CEA, DEN, DEC, Centre de Cadarache, F–13108 Saint Paul Lez Durance Cedex, France
  • 2: CEMES/CNRS, F–31055 Toulouse Cedex 4.
  • a: E-mail: claire.onofri@cea.fr

Abstract

Uranium dioxide (UO2) pellets are worldwide used as a nuclear fuel for power plants. During in-pile irradiation, extended defects (dislocations) are produced in the fuel (mainly because of the energy loss of fission products), as well as rare gases, like Krypton or Xenon. After more than 60 years old of studies on the behavior of UO2, it remains a lack in the formation and release of fission gases knowledge. Release of these fission gases is an important nuclear safety issue, since the integrity of the first barrier of containment has to be warranted. A previous study [1] has shown that the presence of the extended defects induce a preferential growth of fission gas bubble on these defects. Hence, the study of extended defects created under irradiation is a significant step to better understand the behavior of fission gas bubbles.

The evolution of extended defects under irradiation is the result of the simultaneous influence of several parameters: temperature, burn-up, radiation damages… However the understanding of the contribution of each parameter on the evolution of these defects remains yet limited in in-pile conditions. Using a separated effects approach, the current study attempts to clarify the effect of two parameters: temperature and radiation damage on the extended defects evolution. One promising way to understand the behavior under irradiation of the UO2 nuclear fuel is to use ion implantations and further analyze the microstructure. So, this experimental study is based on energetic ion implantations on polycrystalline UO2 at high temperature (600°C), and at the liquid nitrogen temperature, followed by thermal annealing. In-situ observations at the nanometer scale using Transmission Electron Microscopy enable a description of extended defects evolution with the combined effect of temperature and irradiation, without any temperature contribution, and with only the temperature effect.

Complementary techniques, which provide characterizations at the macroscopic scale, are also coupled with TEM observations, and show a good correlation as highlighted in our previous study [2].

  1. A. Michel, Ph. D thesis, CEA Cadarache, Rapport CEA-R–6295, 2012.
  2. C. Onofri, C. Sabathier, H. Palancher, G. Carlot, S. Miro, Y. Serruys, L. Desgranges, M. Legros, submitted for publication in NIMB.