Influence of helium on the evolution of irradiation-induced defects in tungsten: An object kinetic Monte Carlo simulation*

Abstract

Understanding the evolution of irradiation-induced defects is of critical importance for the performance estimation of nuclear materials under irradiation. Hereby, we systematically investigate the influence of He on the evolution of Frenkel pairs and collision cascades in tungsten (W) via using the object kinetic Monte Carlo (OKMC) method. Our findings suggest that the presence of He has significant effect on the evolution of irradiation-induced defects. On the one hand, the presence of He can facilitate the recombination of vacancies and self-interstitial atoms (SIAs) in W. This can be attributed to the formation of immobile He-SIA complexes, which increases the annihilation probability of vacancies and SIAs. On the other hand, due to the high stability and low mobility of He-vacancy complexes, the growth of large vacancy clusters in W is kinetically suppressed by He addition. Specially, in comparison with the injection of collision cascades and He in sequential way at 1223 K, the average sizes of surviving vacancy clusters in W via simultaneous way are smaller, which is in good agreement with previous experimental observations. These results advocate that the impurity with low concentration has significant effect on the evolution of irradiation-induced defects in materials, and contributes to our understanding of W performance under irradiation.

Collaborative motion of helium and self-interstitial atoms enhanced self-healing efficiency of irradiation-induced defects in tungsten

“…In addition, due to the attractive interaction of He with SIA, the large He n -SIA m clusters can be easily formed in irradiated W, especially at high temperature and/or high irradiation dose. This is also confirmed in previous simulations [62][63][64], in which the influence of He on the evolution of collision cascades was determined. As demonstrated in previous study [64], the formation of large and immobile He n -SIA m clusters suppresses the segregation of SIAs into sinks and thus increases the reaction probability of vacancy-interstitial recombination in W at high temperature.…”

“…This is also confirmed in previous simulations [62][63][64], in which the influence of He on the evolution of collision cascades was determined. As demonstrated in previous study [64], the formation of large and immobile He n -SIA m clusters suppresses the segregation of SIAs into sinks and thus increases the reaction probability of vacancy-interstitial recombination in W at high temperature. Thus, the large He n -SIA m clusters should be of critical importance for the evolution of irradiation-induced defects in W-He system.…”

Deuterium retention in heavy-ion and helium-ion sequentially irradiated tungsten

“…It should be noted that this experiment was performed at a temperature of 1223 K, which may be somewhat different from the room temperature experiment. Hou et al found that the addition of He inhibited the migration of vacancies and hence kinetically suppressed the formation of large vacancy clusters [61]. Qin et al observed that pre-irradiation with Kr ions inhibits the growth of large He bubbles and increases the density of He clusters [62].…”

A kinetic description of the impact of agent competence and psychological factors on investment decision-making

“…In this section, we apply the Monte Carlo method [25][26][27][28] to simulate the Boltzmann equation ( 26) and the equilibrium distribution (41). We set D(y, v) = 0, w = 3, u = 0.4, λ 1 = 0.6, σ = 0.2, λ 2 = 0.1, λ 3 = 0.4, λ 4 = 0.6, m 1 = 0.5 and m 2 = 0.5, the marginal densities of competence in the Boltzmann model ( 26) and the Fokker-Planck equation (41) with different values of ε and α 2 are displayed in Fig.…”