Year
1995
Abstract
A californium shuffler originally designed to assay hollow cylindrical pieces of UA1 has been modified to assay solid cylinders. Calibration standards were characterized via chemical analysis of the molten UA1 taken during casting of the standards. The melt samples yielded much more reliable characterization data than drill samples taken from standards after the standards had solidified. By normalizing one wellcharacterized calibration curve to several standards at different enrichments, a relatively small number of standards were required to develop an enrichmentdependent calibration. The precision of this shuffler is 0.65%, and the typical random and systematic uncertainties are 0.53% and 0.73%, respectively, for a six minute assay of an ingot containing approximately 700 grams of 235U. This paper will discuss 1) the discrepancies encountered when UA1 standards were characterized via melt samples versus drill samples, 2) a calibration methodology employing a small number of standards, and 3) a comparison of results from a previously unused shuffler with an existing shuffler. A small number of UA1 standards have been characterized using samples from the homogeneous molten state and have yielded enrichment-dependent and enrichment-independent calibration curves on two different shufflers.