Neutron-induced autoradiography based on relief and dyed image formation in polymers

Neutron-induced autoradiography utilizing formation of a dyed and/or relief image in polymers was developed. The method is based on the detection of neutron-induced charged particles, via (n,p), (n,α), (n,f) reactions and those neutron capture processes leading to internal conversion and/or β-decay. Irradiated polymers are treated in water containing an organic dye or in pure water for a few minutes to obtain a dyed and/or relief image, respectively. The fluence of charged particles required to produce a dyed image is between 1011 to 1012 cm-2 which is one order of magnitude less than that for a relief image. Various procedures based on utilization of optical and electron microscopy for contrast enhancement were developed. The techniques were applied to image boron, uranium and gadolinium in solids. Samples were irradiated in the core of a nuclear reactor. The required thermal neutron fluence was between 1014 to 1016 cm-2. (author)