A new nondestructive iterative method for forensics characterization of uranium-bearing materials by HRGS

In addition to the isotopic composition of a radioactive material, the high-resolution gamma spectrometry (HRGS) allows one to quantify physical characteristics of the material, which are important for nuclear forensics. A quantitative assessment of these characteristics requires two input parameters: the sample density and the mass fraction of radioactive material in the matrix. A method is proposed to determine these parameters provided that the enrichment and the total mass of the material are known. The method is formulated as an iterative quasi-Newton Broyden algorithm for finding roots of two functions in two variables. The developed method is applied to certified reference materials based on the powder uranium octaoxide in the range of enrichments from 0.3% to 93%. It is shown that the matrix density and the uranium mass fraction found experimentally well agree with the declared data in certificates, and the deviations do not exceed 4% up to an enrichment value of 93%.