Abstract
The behaviors of xenon in molybdenum were studied using molecular statics and molecular dynamics simulations. The diffusion mechanism of xenon atoms was studied combining molecular dynamics, nudged elastic band, and temperature-accelerated dynamics methods. The vacancy-assisted diffusion mechanism was analyzed and the corresponding energy barriers were calculated. The clustering process of scattered xenon atoms was studied at an elevated temperature. Xenon bubbles were observed to form when the concentration of xenon atoms exceeded a threshold concentration value. Meanwhile, the interaction of xenon bubble and vacancies was investigated via the nudged elastic band method. The results showed that there exists a region around the xenon bubble where the migration energy of vacancy is significantly influenced. This work provides useful insights towards a better understanding of the behaviors of xenon in molybdenum.
Highlights
A comprehensive understanding of the irradiation behaviors of nuclear fuel is of great importance to the safety of nuclear reactors
The formation of gas bubbles affects the mechanical and thermal properties of the fuel and enhances fuel swelling which may lead to mechanical stresses on cladding materials
A ternary embedded-atom method (EAM) potential for uranium–molybdenum–xenon system developed by Smirnova et al using a force-matching technique and a dataset of ab initio atomic forces [21] was used
Summary
A comprehensive understanding of the irradiation behaviors of nuclear fuel is of great importance to the safety of nuclear reactors. As one of the typical irradiation behaviors, fuel swelling due to fission gas atoms has gained widespread attention [1,2]. Due to their extremely low solubility in nuclear fuel materials, fission gas atoms such as Xe and Kr tend to precipitate into bubbles. The formation of gas bubbles affects the mechanical and thermal properties of the fuel and enhances fuel swelling which may lead to mechanical stresses on cladding materials. Fission gas species may be vented to the fuel plenum, increasing the plenum pressure. Excess fuel plenum pressure and/or fuel swelling as a result of gas bubble growth may eventually lead to fuel element failure. A complete understanding of the fission gas bubble behaviors is necessary
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