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ISO 18213-3:2009 presents statistical procedures that can be applied to tank calibration and volume measurement data for nuclear materials accountancy tanks. In particular, ISO 18213-3:2009 presents several diagnostic plots that can be used to evaluate and compare tank calibration data; a procedure for estimating the uncertainties of tank calibration measurements (i.e., determinations of height and volume); a model for estimating either a tank's calibration equation or its inverse (the measurement equation), together with related uncertainties, from a set of standardized tank calibration data (i.e., from a series of standardized height-volume determinations); and a method for computing uncertainty estimates for determinations of liquid volume.

It is intended that the methods in ISO 18213-3:2009 be used within the context of the other parts of ISO 18213. Specifically, the methods presented in ISO 18213-3:2009 are tailored to the general methodology described in ISO 18213-1 and to appropriate related algorithms in ISO 18213-2, ISO 18213-4, ISO 18213-5 or ISO 18213-6. Although the methodology in ISO 18213-3:2009 is intended for application specifically within the context of the other parts of ISO 18213, the methods are more widely applicable. In particular, the statistical model presented in Clause 5 for estimating the tank's measurement equation from a set of standardized calibration data can be applied, regardless of whether or not these data are acquired in accordance with the methods of ISO 18213. A similar statement holds for (propagation) methods of variance estimation: it is intended that the results in ISO 18213-3:2009 be applied to the specific models for which they were derived, but the methods themselves are more widely applicable.

An option is presented for a facility to develop equivalent plant- or tank-specific methods of statistical analysis as an alternative to ISO 18213-3:2009. However, if a facility adopts ISO 18213 and chooses not to develop equivalent alternative methods of statistical analysis, it is necessary to use the methods of ISO 18213-3:2009.