Method for quantifying the uncertainty associated at the gamma ray spectrum raw data extraction by deconvolution software

Gamma ray spectrometry is a passive non destructive assay most commonly used to identify and quantify the radionuclides present in complex huge objects such as nuclear waste packages. The treatment of spectra from the measurement of nuclear waste is done in two steps: the first step is to extract the raw data from the spectra (energies and the net photoelectric absorption peaks area) and the second step is to determine the detection efficiency of the measuring scene. Commercial software use different methods to extract the raw data spectrum but none are optimal in the treatment of spectra containing actinides. Spectra should be handled individually and requires settings and an important feedback part from the operator, which prevents the automatic process of spectrum and increases the risk of human error. In this context the Nuclear Measurement and Valuation Laboratory (LMNE) in the Atomic Energy Commission Valduc (CEA Valduc) has developed a new methodology for quantifying the uncertainty associated with the extraction of the raw data over spectrum. This methodology was applied with raw data and commercial software that need configuration by the operator (GENIE2000, Interwinner...). This robust and fully automated methodology of uncertainties calculation is performed on the entire process of the software. The methodology ensures for all peaks processed by the deconvolution software an extraction of energy peaks closed to 2 channels and an extraction of net areas with an uncertainty less than 5 percents. The methodology was tested experimentally with actinides spectrum.