Assessing performance of Nucleco Passive/Active System (PANWAS) through a long-term verification campaign

Nucleco SpA is responsible for the management of radioactive waste produced in Italy by industrial research, medical processes and decommissioning of nuclear installations. Nucleco SpA has an integrated gamma/neutron facility for the radiological characterization of the radioactive waste. This comprises high resolution gamma spectrometry systems using several possible measurements approaches (open geometry, segmented scanning, tomographic scanning) and a combined Passive/Active Neutron Waste Assay System (PANWAS). PANWAS system is used for quantification of Special Nuclear Materials in standard drums and cemented overpacks, thanks to its 3He detectors, a deuterium-tritium (D-T) neutron generator, a 252Cf neutron source and complex electronics. Starting from end of 2019, along with the scheduled and extraordinary maintenance, and in consideration of the standard operations to be performed for decommissioning activities, PANWAS system is undergoing to a performance study measuring a Plutonium standard source repetitively, to prevent subtle malfunctions (although not triggering daily quality assurance checks). In addition, thanks to the presence of a weather station installed in the measurement room, the same measurements have been used for studying the system performances as a function of the environmental conditions, namely temperature, humidity, pressure. In this study an interesting correlation was found between the temperature and the system response and the impact that the replacement of a neutron generator can have in quantifying the result.