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Joint projects

Materials under irradiation

JRP 05-04

Partners

Contact

Dr. Ph. Garcia

CEA Cadarache-DEN/DEC - Bât. 151 - 13108 St-Paul-lez-Durance Cedex France

A separate effects study of the behaviour of helium in uranium dioxide

Status

Terminated

- Planned from October 2006 till March 2008

Goals

This joint research project is the second phase of the research carried out in JRP 01-35. It aims to tackle the subject of the behaviour of helium in uranium dioxide.

Although considerable progress has been made during the first phase of the project, important questions, relative to the behaviour of He in UO₂, remain unanswered. The following scientific objectives have been identified:

to determine the relationship between the level of damage in the material, the He concentration (in the 0.2 at% and 2x10^-5 at% range) and the He diffusion coefficient;
to demonstrate that we are justified in inferring volume diffusion coefficients from experiments run on poly-crystalline samples that were analysed using kinetic diffusion models;
to estimate the temperature and He concentrations at which helium bubble nucleation substantially affects the apparent diffusion of helium, hence helium release;
to determine whether grain boundary diffusion of helium proceeds at a different rate to volume diffusion. If so, we will attempt to estimate the acceleration factor in the 700°C to 1100°C temperature range;
to ascertain helium diffusion mechanisms in UO₂;
to quantify the solubility limit of He in UO₂ as a function of pressure and temperature and to determine whether irradiation damage is likely to modify this limit;
to determine the extent to which the available atomistic modelling tools can provide help in interpreting our experimental data or whether they are capable of accurately estimating some of the measured physical values.

Expected results

The results of this joint research project will provide the necessary input data for the development of fuel behaviour models (diffusion coefficients, irradiation effects,…). Moreover, the actual models developed for the purpose of interpreting experimental results can be adapted to interpreting in-reactor data. Furthermore, the outcome of this project can limit the volume of resource consuming experiments that need to be carried out when highly active materials are involved.