ISO DIS 11482

Description / Abstract: This standard gives suggested guidance (emphasizing statistical techniques) for the estimation of sampling error when sampling batches of bulk uranium or plutonium oxide powders. The intent of the guidelines is to verify that the samples obtained using the established mixing and sampling methods are representative of the oxide powder from which they were drawn. The principles can also be extended to the sampling of other bulk materials. This standard does not address the various types of mixing and sampling mechanisms or the numerous methods for destructively analyzing the drawn samples or the means of preserving the physical integrity of the sample

As described in this standard, the material to be sampled is free-flowing oxide powder. Oxide powder is referred to as bulk material because it is not identified in terms of discrete units but is accounted for in terms of the weight (or volume) of an aggregate mass of solids, together with the drawing and destructive analysis of samples of those solids. Bulk material is generally processed in batches, where a batch represents a specific quantity of material that is accounted as a unit, the quantity and composition of which are defined by a set of measurements. The assumption is made that the quantity of bulk oxide within a defined batch is previously determined, perhaps by weighing a mass of powder in a container(s) and then subtracting the recorded tare weight(s). In this standard, material composition is not determined holistically (as with nondestructive analysis) but is assessed by extracting small portions (samples) from a defined batch, measuring the analyte(s) of interest within the drawn samples, and using the analytical measurements for inferring a representative value for the analyte(s) within the entire batch. The determination of bulk mass and the reported analyses of the drawn samples constitute the set of measurements for the batch.

The extent to which a set of measurements characterizes a batch of bulk oxide depends upon 1) the degree to which the material in the samples has remained unaltered by external factors, such as, oxidation, moisture absorption, or contamination with impurities; 2) the accuracy of the measurement methods used for analyzing the samples; and 3) the extent to which the sampling method selects samples that are representative of the entire batch of bulk material. This standard addresses the third topic. It gives guidelines for (1) testing for adequate mixing, (2) quantifying the sampling error variance, (3) expressing the uncertainty in an average sample measurement, and (4) assessing mixing effectiveness through the mixing and sampling of composited reference samples