Thermal neutron computed tomography at the Argonauta Reactor

Abstract

Since 1985 the Argonauta Reactor at the Instituto de Engenharia Nuclear -IEN/CNEN has been used as a source of thermal neutrons to acquire transmission-generated radiographic images. From that time until the end of the last century, some Universities and Research Institutions have as well used the irradiation facilities of this reactor for that purpose and for technical and scientific training of personnel. Quite recently, a joint work program with the Laboratório de Instrumentação Nuclear -LIN/COPPE-UFRJ has been initiated addressing the research in the field of radiographic images using thermal neutrons, with special emphasis on Computer Aided Tomography. Within this frame, different tomographic systems -each one with their intrinsic featureshave been developed aiming at their use in the industry field which requires the inspection of objects exhibiting different sizes and compositions. This work focuses the developed tomographs presenting their constraints and performances such as Spatial Resolution, Modulation Transfer Function and Density Resolution. The acquired images of some objects and test-bodies are as well presented for the sake of qualitative evaluation. They show a fair agreement with the performance of the tomographic system as expected from the measured quantitative parameters.

Neutron diffraction measurements of weld residual stresses in three-pass slot weld (Alloy 600/82) and assessment of the measurement uncertainty

“…The nominal gauge volume in the diffractometer is considered to be cuboid (can also be parallelepiped) with its centroid defined at the intersection of the incident and diffracted neutron beams. However, the effective gauge volume is instrument dependent (Suzuki et al, 2013;Silvani et al, 2005), so the measurement is conducted using a sampling gauge volume that is part of the instrumental gauge volume. Texture and neutron beam absorption can have a significant effect on the geometric location and centroid of the sampling gauge volume within the sample (Hutchings et al, 2005;Price et al, 2008).…”

Parallel Beam Neutron Computed Tomography Reconstruction With Various Filters

“…The larger the number of projections is used the better the quality of the image is obtained. X-ray Computed Tomography (XCT) has reached a mature technology and Neutron Computed Tomography (NCT) has become a complement of XCT (10)(11)(12)(13) . Briefly tomographic reconstruction process can be illustrated in the following block diagram (Figure 1) (14) .…”