Study On Mechanics Of Low-temperature Sintering Of UO₂ Pellets

Entering into the 21^st century, the high speed development of the economy in our country has made the energy crisis increasingly obvious. General energy, such as coal, hydro-energy and so on, can't meet the need of social economy development. Hence, the clean and effective nuclear energy has become the promising part in future energy field. With more importance attaching to the environment protection international and energy cost increasing because of the energy crisis, the study on low temperature sinter of UO₂ becomes the hotspot of nuclear energy country again after 40 years dreariness. To utility the low temperature sintering industry, some discoveries must be found in the mechanism of low temperature sintering. Otherwise, the study of technology will be faced with bottleneck. But there is a few findings in the study of low temperature sintering, which cries for more efforts putting into the mechanical study of low temperature, to find a method for technology promoting and enrich the known activation sintering theory.This paper has established and calculated the point defect model of UO_2+x, according to defective chemistry and already obtained experimental data. And the inherent relation between defect concentration, partial pressure of oxygen and abundant oxygen of UO₂+x has been found and based on this working out Brouwer figure of various defect. Making use of PDM calculating result, the diffusion coefficient expression of uranium ion and UO₂ low temperature sintering dynamical equation is obtained. And the feasibility, necessary condition, affecting factors and densification process of low temperature sintering of UO₂ have been discussed. PDM is utilized to forecast the non-crystal phenomena in the sintering process and study the effect of non-crystal on the process of sintering. Micro-oxidation low temperature experiment of UO₂ has been carried out. The experimental data has been used to validate PDM and low temperature sintering mechanics. The advantage and disadvantage of PDM have been discussed also.For the first time, the PDM is used to study the low temperature sintering mechanics of UO₂, and the research results indicate:1. In the practical sintering condition, the main point defects of UO₂ are O_i^- and h^Ë™, while when the Po₂ is small, the main defects are O_i^-and V_O^¨. The Brouwer...