DETERMINATION OF THE NUCLEAR UNCERTAINTY OF SAFEGUARDS MASS (WEIGHT) MEASUREMENTS

The determination of the uncertainty of mass (weight) measurements associated with the safeguards of nuclear materials is critical to the propagation of the overall uncertainty of the inventory measurements. The mass measurements for which these uncertainties need to be determined are associated with the reference materials used to calibrate safeguards measurements systems, the measurements of the bulk material contained in the inventory. Measurement control data obtained with mass standards indicates the performance characteristics of the mass measurement device, but does not necessarily provide valid information on the uncertainty of the mass measurements of nuclear materials made on those devices. The best approach to determine the uncertainty of safeguards mass measurements is to perform the measurement process in the same way as it is done for nuclear material using calibrated and traceable mass standards in place of the nuclear material. Protocols are described and examples are given for the determination of the uncertainty of the various types of safeguards mass measurements.