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| Home > Publications database > Fast Neutron Imaging with an aSi Detector for Nuclear Waste Assay |
| Abstract | FZJ-2014-06360 |
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2015
Abstract: Introduction: Radioactive waste has to undergo a process of quality checking in order to check its conformance with national regulations prior to its transport, intermediate storage and final disposal. Within the quality checking of radioactive waste packages non-destructive assays are required to characterize their radiotoxic and chemotoxic contents. In a cooperation framework Forschungszentrum Jülich GmbH, RWTH Aachen University and Siemens AG are studying the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA) using 14 MeV neutrons. Fast neutron imaging is a promising technique to assay large and dense items providing in complementarity to photon imaging additional information on the presence of structures in radioactive waste packages. However due to the low neutron emission of neutron generators the challenging task resides in the development of an imaging detector with a high efficiency, a low sensitivity to gamma radiation and a resolution sufficient for the purpose.Setup: The setup of the experiment is shown in Figure 1. The 14 MeV neutrons are produced by a D-T neutron generator. Neutron detection is achieved using a 40 x 40 cm² amorphous silicon (aSi) flat panel detector linked to a plastic scintillator. The detector thermal noise was reduced by employing an entrance windows made of aluminium. The optimal gain and integration time were obtained by measuring the response of the detector to the radiation of a 241Am source.Performance Tests: First test measurements were carried out with different materials made of Al, C, Fe, Pb, W, concrete and polyethylene (50 x 80 x 100 mm³). Each sample was irradiated with PE as a reference. Data analysis was performed with a homemade algorithm which allows determining a value related to the neutron absorption.Results: First neutron radiographies were successfully recorded despite the low detector efficiency and low neutron intensity. In addition the correlation between the absorption and measured signal attenuation was determined and is shown in figure 2. The measurements and results will be presented and discussed.
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