Description: Fracture tendency of pellets after final heat treatment or vacuum outgassing during production has been reviewed. A statistical analysis of fracture tendency has revealed a cyclical trend. The period of the cycle on average is about every 50 pellets. Phosphorus is considered detrimental to the impact behavior of iridium. Tests show that phosphorus is easily picked up by PuO/sub 2/ through a variety of pathways and is difficult to remove by heating techniques such as are possible in the PuFF Facility. High-temperature impact ductility of CVS welds may be related to grain structure in the weld centerline. Heating at 1500/sup 0/C causes finely structured thorium-bearing patches on grain surfaces in welds to agglomerate into particles. Heating at 2000/sup 0/C appears to heal grain boundary cavities and pores. High-temperature creep has been identified as another mechanism for producing grain boundary cavities that cause weld-quench cracking. 17 figures, 11 tables.
Date: December 1, 1982
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