UO2 doping through Cr wet coating

SCK•CEN Mentor

Delville Rémi, rdelvill@sckcen.be, +32 (0)14 33 31 65

Expert group

Fuel Materials

Introduction

Additives are widely used to control the microstructure of materials via their effect on defect chemistry during sintering. As the primary nuclear fuel, the properties of UO2 are crucial for safe and efficient reactor operation. UO2 has been manipulated by fuel vendors through doping to enhance grain size to provide improved fission gas retention and plasticity.

Objective

One of favored route is doping with small amount of Cr. To explain grain growth enhancement, it is believed that Cr (or its oxide) facilitates the movement of grain boundaries during sintering. The initial distribution of Cr on particle surface in the compacted green pellets might therefore have an important role in the further evolution of grain boundaries during sintering at high temperature. It appears indeed that when producing a perfect solid solution in the initial powder by co-precipitation from a homogenous solution, the enhanced grain growth effect is lost. The typical industrial route employs a dry mixing of UO2 and Cr2O3 pellets. A more effective way of further promoting grain growth would be to uniformly coat UO2 powder particle with Cr2O3.  It would ensure an optimal distribution of the grain growth enhancer at the interface between particles for sintering. To do so, a wet coating technique consisting in the immersion of UO2 particle in Cr nitrate solution is being explored at SCK•CEN in collaboration with Fz Julich. In this thesis, it is proposed to systemically investigate the parameters influencing the coating effectiveness on grain growth through wet coating. The work covers the complete fuel preparation procedure from the making of UO2 powder, to its coating and to its transformation into sintered pellets and their characterization by various analytical techniques (OM, XRD, SEM).

The minimum diploma level of the candidate needs to be

Academic bachelor , Master of sciences , Master of sciences in engineering

The candidate needs to have a background in

Physics , Chemistry

Estimated duration

3-6 months