Figure 1: Schematic diagram of the PGNAA experimental facility Neutron Radiography using isotopic neutron sources: Preliminary results S. Kolovi1,2, T.J. Mertzimekis2, I.E. Stamatelatos1, K. Bouchra3, Z. Dimitrakopoulou3 1 Institute of Nuclear and Radiological Sciences, Energy, Technology & Safety, NCSR "Demokritos” 2 Dept. of Physics, University of Athens 3 Dept. of Computed Tomography, General Hospital of Nikaia “Agios Panteleimon” INTRODUCTION Neutron Radiography (NR) is an imaging method based on the neutron attenuation properties of the imaged object. To produce an image a source of neutrons, a collimator to shape the emitted neutrons to a mono-directional beam, an object and a method of detecting neutrons are required. The present work is a preliminary study aiming to investigate the potential of Neutron Radiography using (a, n)-type isotopic neutron sources. As an application, NR images of a portable NaI scintillation detector and common computer components (CC) were acquired. The parameters that should be taken into account for the design of NR system based on (α, n) type sources are discussed. In addition, the NaI detector was examined with X-ray Computed Tomography (CT) to compare the two imaging techniques on their efficiency as diagnostic tools for such instruments. CONCLUSIONS x The results of the study suggest that neutron imaging can be performed using an isotopic (α, n) type neutron source and an IP (imaging plate) with Gd2O3 surface layer . x Requirement for a successful image is a well collimated and moderated neutron beam. x The thermal-neutron fluencies that can be achieved from isotopic source assemblies are low and can only be used for applications in which high resolution and short exposure times are not required. x Nevertheless, a significant advantage of this approach is the overall simplicity and cost effectiveness due to the long half-life of (α, n) type neutron sources. x Future work will be directed towards a trade-off study between source intensity, neutron collimation and moderation, as well as radiation shielding requirements, in order to achieve a given image resolution. REFERENCES  Neutron Imaging: A Non - Destructive Tool for Material Testing, IAEA - TECDOC - 1604, ISBN 978 - 92 - 0 - 110308 - 6  Practical Neutron Radiography , J. C. Domanus, ISBN 0 - 7923 - 1860 - 9  Bio-Imaging Analyzer BAS1500 IP Reader (Fujifilm) Operation Manual  N. Chankow et al., Applied Radiation and Isotopes, 68, 662 - 664, (2010) Computer Components NR NaI Detector NR - CT Sample Cadmium Moderator Δt (min) Figure Floppy drive / Graphics card + - 60 5 i + + 60 5 ii - + 38 NaI 6 i + - 60 - + + 60 6 ii - + 120 6 iii + - 210 7 ii + + 210 6 iv / 7 i EXPERIMENTAL SETUP & METHODOLOGY RESULTS Figure 6: NR with slow neutrons i) Δt = 38 min ii) Δt = 60 min iii) Δt = 120 min iv) Δt = 210 min The Cadmium reference sheet is marked in the picture. Figure 7: i) NR with thermal neutrons Δt = 210 min ii) NR with fast neutrons Δt = 210 min iii) CT ( X - Rays) The Cadmium reference sheet is marked in the picture. NaI Detector NR NR vs. CT in the case of NaI detector The initial aim of the irradiation of the portable NaI detector was to detect any defects or cracks in the crystal. The NR image with thermal neutrons (Fig. 7i) is of higher resolution in comparison to the one with fast neutrons (Fig. 7ii), whereas Fig. 7ii has a better image quality. No significant structural defects were detected with NR. The CT image (Fig. 7iii) offers the greatest resolution and image quality in the minimum exposure time. No defects were detected either. Dimensions of the NaI crystal (known) agree with the measurements taken from Fig. 7i and Fig. 7iii. iii Fast vs. Slow neutrons For the same exposure time, the NR image obtained with fast neutrons (no moderator) is of higher quality in comparison to the one obtained with slower neutrons (5 cm moderator) in the case of the computer compo- nents. CC consist mainly of metal parts. The effect of exposur