Intragranular Xe bubble population evolution in UO2: A first passage Monte Carlo simulation approach

Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

“…In our work, the phase-field model coupling a one-dimensional random walk model, first developed to simulate the void lattice formation [18], was extended to study the gas bubble evolution with a large difference and strong anisotropy of defects' diffusivity. We used the first-passage Monte Carlo method to describe the one-dimensional migration of interstitials [18,56,57], and the phase-field model is used to describe the evolution of defects and microstructure.…”

Mechanistic materials modeling for nuclear fuel performance

“…Efforts to develop new mechanistic fission gas release models based on multiscale simulations have focused on understanding the behavior of fission gas atoms and point defects in bulk UO 2 [49,[51][52][53][54][55] as well as how their properties are influenced by fuel chemistry [49,53,78,82] and irradiation conditions [73], segregation to grain boundaries [72,93,94], simulation of percolation networks at grain boundaries [95], nucleation and growth of inter-and intra-granular bubbles [85,[96][97][98][99][100][101][102][103] and bubble resolution [100,[104][105][106]. Attempts to use lower length scale simulations of fission gas properties in fuel performance simulations have so far relied on hierarchical approaches where certain parameters in the engineering scale models, such as the fission gas diffusion rate, are informed by lower length scale simulations [73,107].…”

Effective fission gas diffusivity study using First Passage Monte Carlo

“…[1,2] does not provide a complete picture of step 1), since fission gas diffusion is also affected by the formation of small fission gas bubbles in the grain interior, acting as sinks for the diffusing fission gas atoms. Under irradiation these bubbles do not grow beyond the nanometer range in size due to resolution by fission fragments [3][4][5]. Moreover, these intragranular bubbles are usually assumed to be stationary for in-pile conditions (under irradiation) and thus act as sinks rather than contribute to mass transport, though bubble growth and migration are both possible for out-of-pile conditions (no irradiation) as well as for transients [6][7][8][9].…”

“…However, due to the time and length scale limitations of DFT and molecular dyanmics simulations, they are not well suitable to address this problem as stand-alone applications. To solve this problem, Schwen et al have developed hybrid molecular dynamics and Monte Carlo techniques as well as a first passage Monte Carlo simulation methodology to study the properties of intragranular fission gas bubbles [4,5]. The focus of the work in Ref.…”

“…As the study shows, this introduces negligible error in the calculations. The second study by Schwen et al [4] introduces a first passage based Monte Carlo algorithm to investigate the population evolution of Xe fission gas bubbles in UO 2 fuels. Growth laws were obtained for homogeneous and heterogeneous re-solution models for a wide range of gas and bubble diffusivities.…”