Results from ORNL Characterization of Nominal 350 ?m LEUCO Kernels (LEU03) from the BWXT G73V-20-69303 Composite

Kercher, Andrew K. ; Hunn, John D.

Oak Ridge National Laboratory

关键词: Kernels;    Fuel Particles;    Shape;    Uranium Oxides;    Triso;   

DOI  :  10.2172/974612
RP-ID  :  ORNL/TM-2006/552
RP-ID  :  DE-AC05-00OR22725
RP-ID  :  974612

美国|英语

来源: UNT Digital Library

【 摘 要 】

Measurements were made using optical microscopy to determine the size and shape of the LEU03 kernels. Hg porosimetry was performed to measure density. The results are summarized in Table 1-1. Values in the table are for the composite and are calculated at 95% confidence from the measured values of a random riffled sample. The LEu03 kernel composite met all the specifications in Table 1-1. The BWXT results for measuring the same kernel properties are given in Table 1-2. BWXT characterization methods were significantly different from ORNL methods, which resulted in slight differences in the reported results. BWXT performed manual microscopy measurements for mean diameter (100 particles measured along 2 axes) and aspect ratio (100 particles measured); ORNL used automated image acquisition and analysis (3847 particles measured along 180 axes). Diameter measurements were in good agreement. The narrower confidence interval in the ORNL results for average mean diameter is due to the greater number of particles measured. The critical limits for mean diameter reported at ORNL and BWXT are similar, because ORNL measured a larger standard deviation (10.46 {micro}m vs. 8.70 {micro}m). Aspect ratio satisfied the specification with greater margin in the ORNL results mostly because of the larger sample size resulting in a lower uncertainty in the binomial distribution statistical calculation. ORNL measured 11 out of 3847 kernels exceeding the control limit (1.05); BWXT measured 1 out of 100 particles exceeding the control limit. BWXT used the aspect ratio of perpendicular diameters in a random image plane, where one diameter was a maximum or a minimum. ORNL used the aspect ratio of the absolute maximum and minimum diameters in a random image plane. The ORNL technique can be expected to yield higher measured aspect ratios. Hand tabling was performed at ORNL prior to characterization by repeatedly pouring a small fraction of the kernels in a pan and tilting the pan so that rounder kernels could roll down and drop through a slot in the pan, separating them from less round kernels, fragments and debris. A total of 0.37 g was removed in this manner from the 510 g composite. This can be expected to only produce a slight improvement in the ORNL aspect ratio acceptance value. The estimated change in the 95% confidence critical limit due to hand tabling, which was equivalent to removing 2-3 high aspect ratios kernels from the 3847 kernels in the measured sample, would be an increase from <0.48% to approximately <0.57% of the kernels in the composite predicted to have an aspect ratio greater than 1.05.