Integration of independent techniques for improving limits of gamma-ray spectrometry in assaying complex objects

Dismantling and decommissioning activities in nuclear sites generate a large amount of radioactive waste, whose radiological inventory must be determined with acceptable accuracy through specific characterization procedures. To reduce the overall effort and time required, waste owners seek to build these procedures around Non-Destructive (ND) techniques. Nevertheless, these procedures must guarantee reliability levels in agreement with international standards and national Control Authorities, which can otherwise require further actions and constraints. Nucleco often must characterize items requiring specific characterization procedures. Recently, metallic boxes with variable volume and mass containing plutonium radioisotopes were characterized according to a new procedure that includes gamma-ray spectrometry, gamma-ray imaging and X-ray imaging. In this paper, this procedure is presented and applied to one of these boxes. This box was then treated and put into a 220 L drum, which was then characterized via conventional means, providing an a posteriori validation of the presented procedure. The results confirmed the developed procedure’s suitability to characterize complex items for determination of their radiological inventory.