Development of a software package for improving accuracy and precision in non-destructive declaration of radioactive waste

Huge amounts of different waste streams arise during the decommissioning of nuclear installations. The characterization of these waste streams is frequently supported by non-destructive assay techniques. Depending on the objective, different techniques are applied like integral gamma-counting for free-release measurements or gamma-scanning for activity determination. In practice, all techniques have in common that the measurement result strongly depends on the activity and matrix distribution throughout the measuring object which are only specified/known in rare cases and are approximated by rather simple models. A statement concerning accuracy and corresponding uncertainties is therefore usually based only on counting statistics. In some applications the uncertainties are ''corrected'' by empirical factors which should take into account the lack-of-know ledge on the real matrix and/or activity distribution. To overcome this unsatisfactory situation, a software package was developed for the determination of activities and their uncertainties on a more reliable basis using all available information and considering different density and activity distributions being consistent with the measured data. (orig.)