关键词：核能反应；燃料电池；氢化物燃料
摘 要：The neutron radiography (NRAD) reactor is a 250 kW TRIGA (Training, Research, Isotopes, General Atomics) Mark IIa,b tank-type research reactor located in the basement, below the main hot cell, of the Hot Fuel Examination Facility (HFEF) at the Idaho National Laboratory (INL). It is equipped with two beam tubes with separate radiography stations for the performance of neutron radiography irradiation on small test components.c The NRAD reactor is currently under the direction of the Battelle Energy Alliance (BEA) and is operated and maintained by the INL and Hot Cell Services Division. It is primarily used for neutron radiography analysis of both irradiated and unirradiated fuels and materials. Typical applications for examining the internal features of fuel elements and assemblies include fuel pellet separations, fuel central-void formation, pellet cracking, evidence of fuel melting, and material integrity under normal and extreme conditions. Examination of the behavior of large test loops and assemblies can also be performed. Due to the intense gamma activity of most irradiated specimens, the HFEF uses an indirect radiography, where a beam of neutrons passes through a specimen, strikes a gamma-insensitive metal foil (typically indium or dysprosium, for epithermal or thermal neutron spectra, respectively), and activates the foil. The foil can then be placed against a sheet of x-ray photographic film. X-rays from the metal foil then render an image on the film, which is then developed. While this method takes longer than the conventional direct method, the results eliminate gamma interference and are more detailed. Neutron tomography capabilities are being developed, where radiographs are obtained from different rotational angles and digitized to reconstruct cross-sections of a specimen. Direct radiography, such as Polaroid or track-etch radiography, and in-tank irradiations and/or experiments with small in-core samples can also be performed in the NRAD reactor.