Non-destructive studies of fuel pellets by neutron resonance absorption radiography and thermal neutron radiography

• Published in: Journal of nuclear materials 2013-09, Vol.440 (1-3), p.633-646
• Main Authors: Tremsin, A.S., Vogel, S.C., Mocko, M., Bourke, M.A.M., Yuan, V., Nelson, R.O., Brown, D.W., Feller, W.B.
• Format: Article
• Language: English
• Subjects: Applied sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Experimental methods and instrumentation for elementary-particle and nuclear physics; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Neutron sources; Nuclear fuels; Nuclear physics; Particle sources and targets; Physics; Preparation and processing of nuclear fuels
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2013.06.007

Many isotopes in nuclear materials exhibit strong peaks in neutron absorption cross sections in the epithermal energy range (1–1000eV). These peaks (often referred to as resonances) occur at energies specific to particular isotopes, providing a means of isotope identification and concentration measurements. The high penetration of epithermal neutrons through most materials is very useful for studies where samples consist of heavy-Z elements opaque to X-rays and sometimes to thermal neutrons as well. The characterization of nuclear fuel elements in their cladding can benefit from the development of high resolution neutron resonance absorption imaging (NRAI), enabled by recently developed spatially-resolved neutron time-of-flight detectors. In this technique the neutron transmission of the sample is measured as a function of spatial location and of neutron energy. In the region of the spectra that borders the resonance energy for a particular isotope, the reduction in transmission can be used to acquire an image revealing the 2-dimensional distribution of that isotope within the sample. Provided that the energy of each transmitted neutron is measured by the neutron detector used and the irradiated sample possesses neutron absorption resonances, then isotope-specific location maps can be acquired simultaneously for several isotopes. This can be done even in the case where samples are opaque or have very similar transmission for thermal neutrons and X-rays or where only low concentrations of particular isotopes are present (