Book Description

APPR-type dispersion fuel element specimens containing temperature to respective burnups of approximately 50, 20, and 20% of uranium with no evidence of gross dimensional changes or loss of structural integrity. Blistering and/or core cracking has occurred when sections of 17.9 wt.% UO/sub 2/ specimens irradiated to burnups over 40% of uranium were subjected to post-irradiation annealing at 600 deg F for 24 hours. Post-irradiation core hardness measurements indicate that significant differences in irradiation damage exist between the various specimen types. These data indicate that the effects of the fabrication variables investigated in this program are as follows: The severity of irradiation damage in dispersion type fuel elements is inversely proportional to the UO/sub 2/ particle size of the fabricated plate. The particle size of the UO/ sub 2/ powder used in preparation of the initial core compact and the method of preparation of the UO/sub 2/ powders largely determine the final UO/sub 2/ particle size of roll-bonded, dispersion fuel plates. The particle size of the stainless steel powder used in the initial core mixture and the degree of cold reduction during final sizing of the fuel plate are apparently of relatively minor importance, at least for the systems investigated in this program. The severity of irradiation damage is directly proportional to the fuel concentration. Where an increased fuel loading is accompanied by an increase in the loading of the B/sub 4/C burnable poison to facilitate reactor control, the possibility of serious irradiation effects is increased to an even greater degree. (auth).