EVALUATION OF HYDROGEN CONTENT IN METALLIC SAMPLES BY NEUTRON COMPUTED-TOMOGRAPHY

Neutron radiography is currently a well-known technique, which is empl oyed for non-destructive testing in a number of industrial and environ mental applications [1, 2]. Originally developed for reactor fuel exam inations, it is now effective in detecting small amounts of corrosion and infiltrations of hydrogen or light materials within thick metallic structures due to the particular behaviour of total neutron cross sec tions [3]. Nevertheless, improvements related to the development of to mographic systems, which allow far better imaging performances, have b een achieved only in the last few years, as a consequence, primarily, of the production of large, charge coupled device (CCD) arrays [4]. No wadays, neutron computed tomography is the technique most suited for t he study of the distribution of hydrogen within metallic matrices. In this field, a series of experimental tests were carried out employing a set of nickel samples containing a H2O-D2O solution in known percent ages. It was possible, therefore, to obtain a calibration curve for th e total neutron cross section vs. gray level in the reconstructed imag e.