Particulate material consolidation is used for fabrication of conventional nuclear fuel pellets. In this instance, enriched UO2 powder blended with possible additives and lubricants is fed into a die cavity, uniaxial compacted to green condition using opposing motion punches, and subsequently sintered to near theoretical density. The rate of green pellet fabrication is very high with hundreds of pellets per minute compacted using multi-cavity die pressing. For predictable and desired in-reactor fissile performance, the quality of fabricated fuel pellets must be extremely high with effectively 0-defects desired. Therefore, thorough understanding of the powder compaction process is required to achieve high quality, 0-defect green UO2 pellets.

To facilitate process understanding, process development, and aide the processing into pellet of new fissile materials, finite element modeling has been applied to the closed die compaction of UO2 powders. Specifically, the Drucker-Prager Cap model for pressure dependent materials has been applied to model closed die compaction of UO2 powder and die ejection of the green pellet. [1] The model developed was calibrated using available data for a well studied ceramic particulate material such as Al2O3. [2] Using this model, the affect of materials properties on the resultant stress and density distribution of the green pellet were analyzed and results are presented. Additionally, in an attempt to better understand green pellet flaw generation, UO2 powder compaction and green pellet die ejection have been modeled with various anomalies (voids, foreign material, etc.) contained in the loose powder. Affects of these anomalies on green pellet flaws is also presented.

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