Effects of Xe ion irradiation of ZrN and the migration behaviour of implanted Eu

Abstract

Owing to its outstanding properties, zirconium nitride (ZrN) has been proposed as a possible candidate for inert matrix for transmutation of long-lived nuclear waste (plutonium and minor actinides) in fast nuclear reactors. In the nuclear reactor environment ZrN will be exposed to di erent irradiations at elevated temperatures. Under these conditions, it should retain its properties and be able to contain ssion products. The irradiation-tolerance of ZrN to slow and swift heavy ions has been investigated and no amorphization was observed. However, little is known about the migration of ssion products in ZrN with the exception of He. In this study, the radiation damage retained by swift and slow heavy ions, their annealing and the migration behaviour of implanted europium (Eu) were investigated. ZrN layers of about 20 m thick were deposited on silicon substrates using vacuum arc deposition. Some of the deposited ZrN samples were individually implanted with Eu and Xe ions of energy 360 keV all to a uence of 1.0 1016 cmð€€€2, while others were irradiated with 167 MeV Xe ions to a uence of 6.77 1014 cmð€€€2. Both implantations and irradiation were performed at room temperature. The implanted and irradiated samples were annealed at 800 and 900oC for 5h. The as-deposited samples were characterized by scanning electron microscopy (SEM), grazing incidence x-ray di raction (GIXRD) and Raman spectroscopy, while implanted and irradiated samples were characterized by Raman spectroscopy and Rutherford backscattering spectrometry (RBS). GIXRD results con rmed the nano-crystallinity of the deposited ZrN layer. Raman spectroscopy results of the as-deposited ZrN, exhibited all rst-order Raman scattering bands indicating a ZrN structure with defects. SHI irradiation produced less concentration of defects compared to the slow energy implantation of Eu and Xe ions. Cubic-Zr3N4 phases were observed in swift-heavy ion irradiated ZrN after annealing at 800 and 900oC, while it was not observed in the low energy implanted Xe and Eu samples after annealing at the same temperatures. No migration of implanted Eu was observed after annealing.