MOLYBDENUM HOMOGENISATION IN γ-U(Mo) ALLOY ATOMISED PARTICLES

摘要

Uranium-molybdenum alloys are currently studied for use as a high-density fuel in nuclear research reactors [1]. In these alloys, the addition of Mo (typically 7 to 10 wt%). in solid solution, is necessary to stabilise the cubic high temperature γ-phase of uranium at room temperature. These alloys can be used in the form of particles dispersed in an Al-matrix, cladded by Al-alloy sheets. Such particles are mostly produced by centrifugal atomisation. This process is based on the ultra-fast solidification of liquid U+Mo droplets. The obtained particles have a spherical shape with a diameter typically ranging from 20 to 120 μm. Their microstructure corresponds to small grains (equiaxed or columnar) and/or dendrites, as illustrated by Fig. 1. A Mo depletion close to grain boundaries was evidenced by several authors, using different characterisation methods (see for example [3]). This depletion is likely to influence the microstructural evolutions of U(Mo) particles under irradiation. Heat treatments at high temperature can be performed to promote the homogenisation of the Mo content within the grains. Their conditions are still under optimisation.