Experimental investigation of uranium dicarbide densification and the influence of free carbon diffusion

Abstract

for providing funding for this research. Thanks for the opportunity to use an outstanding fuels development facility and equipment during the course of this investigation.Gratitude is extended to Dr. R. Bruce Matthews for interactive discussions, support, and patience during the performance of this work.The author would like to thank Professor Mohamed El-Genk for his encouragement and helpful discussion, which added greatly to the accomplishment of this work.Thanks to Ed Storms for many valuable insights, tutoring, and discussions.A special thanks goes to Gene Moore for his tireless effort in helping prepare, run, and measure samples throughout this investigation. Without his help, little would have been accomplished. Thanks to all the technicians in the Nuclear Fuels group who contributed much to this work.The author is grateful to Nora Rink for her efforts in helping to prepare this manuscript. List of Figures (continued) 5.3.2 UC2 densification on tungsten, niobium, and tantalum with time at 2373 K 5.3.3 UC 2 densification on tungsten, niobium, and tantalum at 2273 K 33 5.3.4 UC 2 densification on tungsten with time at 2273 K 33 5.3.5 UCj densification on niobium with time at 2273 K 5.3.6 UC 2 densification on tantalum with time at 2273 K , 5.3.7 UC^ densification on tungsten with time at 2373 K 5.3.8 UCj densification on niobium with time at 2373 K 5.3.9 UC 2 densification on tantalum with time at 2373 K 5.3.10 UC 2 densification on tungsten with square root of time, 5.3.11 UC2 densification on niobium with square root of time 5.3.12 UC 2 densification on tantalum with square root of time 5.4.1 Height of densified region vs temperature. Second order polynomial fit to each data set is shown 5.4.2 Effect of temperature on densification rate 42 5.5.1 Example schematic of a sliced UC 2 pellet showing slice thickness and weight per cent carbon in each slice 45 5.5.2 Weight per cent carbon from slices cut along axis of batch 5 pellets sintered at 2373 K for various times 47 5.5.3 Weight per cent carbon from slices cut along axis of a batch 6 UC 2 pellet sintered at 2373 K for 6 h 47 5.5.4 Weight per cent carbon slices cut along axis of batch 7 UC 2 pellets sintered at 2373 K for 3,6, and 12 h 48 5.6.1 Mo-U phase diagram 50 5.6.2 Re-U phase diagram 50 List of Figures (continued) 5.7.1 Tungsten carbide forming in a plate of tungsten metal. UC2 pellet was located on top of tungsten carbide during sintering. Hardness indentations made with Vickers hardness tester 52 5.7.2 Tungsten carbide forming in tungsten metal after (a) 4 h and (b) 8 h 53 5.7.3 Tungsten carbide forming in tungsten metal after (a) 12 h and (b) 16 h... 53 5.7.4 Penetration depth of W 2 C formed while sintering UC 2 on tungsten 5.9.1 Schematic of high density regions of stacked UC 2 pellets on niobium after 6 hours at 2373 K 5.11.1 Sintered duplex composition UC X pellets. C/U for one end 1.95 and for the other, 1.50 5.11.2 Photo of a partially sintered duplex composition pellet cut lengthwise and polished. Composition of high density end, C/U = 1.5, ...