NONDESTRUCTIVE DETERMINATION OF VERY-LOW HYDROGEN CONTENT IN METALS WITH THE USE OF NEUTRON TECHNIQUES

In this work we present two methods, based on neutronic techniques, for the non-destructive determination of low hydrogen content (less than or equal to 20 wt ppm) in metals. The first method is based on neutron transmission measurements over the thermal and subthermal energy ranges, and exploits the very large cross-section of hydrogen at low neutron energies. The second method is based on scattering measurements, using epithermal neutrons in combination with time-of-flight techniques and exploiting the large difference in energy-transfer in the neutron-metal and neutron-II interaction processes. We will discuss the conceptual aspects of both methods, the models developed to describe those processes, the experiments performed, and the results obtained for samples of steel and Zircaloy-IV.