Characteristic changes of (U, Ce)O₂ pellet sintered by addition of MO₂ or M₃O₈ scrap powder and different sintering processes

MO₂ scrap powder was recovered by the mechanical crushing-milling or by the oxidation-reduction of a (U, Ce)O₂ pellet, and M₃O₈ powder by the oxidation of the pellet. The MO₂ or M₃O₈ scrap powder was reused up to 30 wt% by adding it to UO₂+5wt%CeO₂ with two different powder treatment routes. The morphology and the addition effects of each scrap powder on sinterability were investigated with the powder routes and the sintering processes. Densification behaviors of the scrap-added powders were studied in an oxidizing atmosphere. A step was observed in each shrinkage curve between 900 and 1060degC as a result of shrinkage measurement up to 1500degC in CO₂. Both the sintered density and the pore distribution could be controlled by the powder treatment method and the adding amount of scrap powder. Grain size of the pellet does not depend mainly on the powder process but on the sintering process. (author)