Kinetic Monte Carlo simulation of helium-bubble evolution in ODS steels

Akiyuki Takahashi, Shahram Sharafat, Koji Nagasawa, Nasr Ghoniem

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Citation (Scopus)


Oxide dispersion strengthened (ODS) ferritic/martensitic steels are being developed for high temperature applications for fission reactors and future fusion devices. ODS-Eurofer97 (Fe-9CrWVTa-0.3Y2O3) and ODS-MA957 (Fe-14CrTiMo-0.25Y2O3) have shown promising high temperature mechanical properties, such as tensile strength, toughness, fatigue, and creep rupture. Recent neutron irradiation experiments with simultaneous helium implantation indicate that helium transport is favorably impacted by the nanometer-sized oxide particles, small grain sizes, and high dislocation densities of ODS steels. Simulating helium transport in ODS steels requires a three-dimensional spatially resolved model, which takes into account discrete geometric and microstructural features of the steel. We have developed such a helium transport simulation model using an event kinetic Monte Carlo (EKMC) approach called Monte Carlo simulation of helium-bubble evolution and resolutions (McHEROS). First, a spatially resolved kinetic rate theory is used to establish helium-vacancy cluster and stable helium-bubble nuclei concentrations. The maximum helium-bubble density is then used as an initial condition for randomly distributed matrix bubbles for the EKMC simulation. Migration, coalescence, and trapping of helium bubbles by oxide particles are simulated. Matrix helium bubbles that come into contact with each other are assumed to undergo instantaneous coalescence, which leads to bubble growth. However, migrating bubbles that are intercepted by oxide particles are assumed trapped but can grow through coalescing with newly arriving bubbles. The oxide particles effectively reduce the growth rate of matrix bubbles. Helium-bubble size and spatial distributions of the EKMC simulation are compared with recent experimental measurements. As part of this study, the effectiveness of the ODS microstructure on reducing helium-bubble growth rates is presented by comparing EKMC simulations of steels with and without ODS particles. This first application of the McHEROS code has demonstrated the viability of the code as a tool in describing the behavior of helium-bubble transport in ODS alloys.

Original languageEnglish
Title of host publicationEffects of Radiation on Nuclear Materials and the Nuclear Fuel Cycle
Subtitle of host publication24th Volume
PublisherAmerican Society for Testing and Materials
Number of pages20
ISBN (Print)9780803134256
Publication statusPublished - 1 Jan 2010
Event24th Symposium on the Effects of Radiation on Materials - Denver, CO, United States
Duration: 24 Jun 200826 Jun 2008

Publication series

NameASTM Special Technical Publication
Volume1513 STP
ISSN (Print)0066-0558


Conference24th Symposium on the Effects of Radiation on Materials
Country/TerritoryUnited States
CityDenver, CO


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