Neutrons are particularly important in the imaging of nuclear-fuel rods which are strong у-sources (X-ray background) and are made from heavy metal elements i. e. uranium or lead with a high attenuation of X-rays. A resolution of 50 pm or better can be accomplished and this has been utilized to characterize nuclear materials, e. g. fuel rods [43] or cladding materials [42], see the section on hydrides above. Recent detector developments allowing for spatially and time-resolved neutron detection [59] are likely to open new avenues of characterization of nuclear materials and nuclear fuels in particular as they allow for isotope-sensitive imaging via neutron resonance absorption [60].