Fabrication And Research Of MA-bearing Nuclear Fuel Particles By A Co-sol-gel Process

With increasing demand of world energy and rising concern about global warming, nuclear power as a clean energy has been considered as the most promising option to counter the growing global energy crisis. In order to realize the sustainable development of nuclear power, the high-level radioactive waste resulting from nuclear energy production must be safely managed in the long-term. In the high-level radioactive waste, minor actinides are of special concern because of their high radioactivity and lasting radiotoxicity. Currently, partitioning and transmutation (P&T) technologies, in which MAs are transformed into short-lived, medium-lived or stable nuclides, were unveiled as a promising way to reduce the burden of nuclear radioactive waste on the environment.Accelerator driven subcritical reactor is a high performance MA transmutation system. A promising nuclear fuel for it is a kind of composite fuel in which MA-based compound was diluted in an inert matrix. At present, there are mainly two routes for the fabrication of MA-containing composite fuel, one is a combined sol-gel and infiltration process, and the other is an oxalic co-precipitation route. For the co-precipitation route, the main challenge is to produce large particles without producing dust, which is not a problem in the sol-gel method. For the fabrication of composite fuel, the dispersed actinide phase was required to be spherical particles with uniform size in order to have a homogenous distribution in the matrix. Nevertheless, the conventional dispersion device used in the sol-gel method needs to be further improved to have a better control on the sphericity, monodispersity and size of the particles. Furthermore, for the infiltration method, the homogeneous distribution of minor actinides in the microspheres needs further investigation.In this paper, a facile route that combines the co-sol-gel process with the microfluidic technology for the fabrication of monodisperse MA-bearing microspheres was presented. The main points can be summarized as follows:1. Ce and Eu were used as surrogates for Pu and minor actinides respectively. The Eu gelation system and the effect of Eu’s content on the co-sol-gel system were studied.2. Three samples of analog MA-bearing microspheres with different Eu contents were successfully prepared. The prepared microspheres all had a narrow-size distribution (CV<2%), excellent sphericity (dmax/dmin <1.07) and high density (>90%TD).3. A capillary-based microfluidic device was designed as a novel collosol dispersion device. This device can be used for fabrication of monodisperse microspheres with good sphericity and controllable size.4. The sintering scheme of gel microspheres was designed through thermal analysis and the study of the influences of different heating rates on microspheres’ rupture. The influence of different HMTA contents on the shape of gel microspheres was also investigated and analyzed.5. The microstructure observation, Eu distribution analysis and crystalline structure analysis were conducted systematically by SEM, EDX and XRD. The results showed that the prepared Ce/Eu oxide microspheres had a close-grained microstructure and a homogenous Eu distribution. All the microspheres showed one cubic lattice structure, corresponding to the diffraction peaks of CeO2.