Highly accurate accounting methods for sensitive nuclear material (SNM) are necessary to safeguard against material diversion to unauthorized purposes. These accounting methods depend in part on measurement of the activity of SNM in radwaste containers. The activity measured for a particular container depends on the mass of SNM and on the spatial distribution of the material within the container. Interpretation of measured activity in terms of contained mass is ambiguous unless the spatial distribution is known. A statistical measure has been developed that enables one to evaluate the confidence to be had in assuming homogeneous spatial distribution of the SNM. For situations where the SNM distribution is not limited to the single homogeneous case, a technique is described by which the measured activity can be interpreted in terms of a probability distribution of the contained mass of nuclear material