TY - JOUR

T1 - Study on impact of Cr and Mo on diffusion of H in 2.25Cr1Mo steel using first-principle calculations

AU - Wang, W.

AU - Li, C.

AU - Shang, Shun Li

AU - Cao, Jianzhu

AU - Liu, Zi Kui

AU - Fang, Chao

N1 - Funding Information:
This work is supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. ZX06901 ). First-principles calculations were partially performed on the ACI clusters at the Pennsylvania State University , partially on the resources of NERSC supported by the Office of Science of the U.S. DOE under Contract No. DE-AC02-05CH11231, and partially on the resources of XSEDE supported by National Science Foundation with Grant ACI- 1053575 .
Funding Information:
This work is supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. ZX06901). First-principles calculations were partially performed on the ACI clusters at the Pennsylvania State University, partially on the resources of NERSC supported by the Office of Science of the U.S. DOE under Contract No. DE-AC02-05CH11231, and partially on the resources of XSEDE supported by National Science Foundation with Grant ACI- 1053575.
Publisher Copyright:
© 2019 Elsevier B.V.

PY - 2019/11

Y1 - 2019/11

N2 - Chrome-molybdenum steel (2.25Cr1Mo steel) is one of the main materials of a steam generator (SG) in high-temperature reactor-pebblebed modules (HTR-PM). It is essential to analyze the source term of tritium in this material, because the behavior of tritium in a SG is important for performing source term analysis in normal and accident conditions. In this article, the diffusion behavior of H atom in 2.25Cr1Mo steel was calculated to estimate the diffusivity of tritium using first-principles density functional theory. To develop and simplify the model of hydrogen diffusion in 2.25Cr1Mo steel, the impact of Cr and Mo on the diffusion of hydrogen in bcc-Fe were first calculated, all the possible diffusion paths were considered, and the minimum energy path was obtained. The diffusion activation energy and pre-exponential factor of the diffusion coefficient were obtained from Vienna Ab initio Simulation Package combined with the climbing image-nudged elastic band method. The results indicate that the minimum energy path for the impurity H atom is from one tetrahedral interstitial site to an adjacent tetrahedral interstitial site. The function of the diffusion coefficient of H in 2.25Cr1Mo steel with temperature T can be expressed as D=1.486×10−7× [Formula presented] (m2/s). The diffusion coefficient of our calculation and some of the previous experiments have an excellent quantitative agreement, which indicates the reliability of our crystalline model and the practicability of the present theoretical approach. More importantly, the computational results in this work can be treated as a good screening method to collect reasonable experimental data, which will provide a good reference for tritium source term evaluation in the SG of the HTR-PM.

AB - Chrome-molybdenum steel (2.25Cr1Mo steel) is one of the main materials of a steam generator (SG) in high-temperature reactor-pebblebed modules (HTR-PM). It is essential to analyze the source term of tritium in this material, because the behavior of tritium in a SG is important for performing source term analysis in normal and accident conditions. In this article, the diffusion behavior of H atom in 2.25Cr1Mo steel was calculated to estimate the diffusivity of tritium using first-principles density functional theory. To develop and simplify the model of hydrogen diffusion in 2.25Cr1Mo steel, the impact of Cr and Mo on the diffusion of hydrogen in bcc-Fe were first calculated, all the possible diffusion paths were considered, and the minimum energy path was obtained. The diffusion activation energy and pre-exponential factor of the diffusion coefficient were obtained from Vienna Ab initio Simulation Package combined with the climbing image-nudged elastic band method. The results indicate that the minimum energy path for the impurity H atom is from one tetrahedral interstitial site to an adjacent tetrahedral interstitial site. The function of the diffusion coefficient of H in 2.25Cr1Mo steel with temperature T can be expressed as D=1.486×10−7× [Formula presented] (m2/s). The diffusion coefficient of our calculation and some of the previous experiments have an excellent quantitative agreement, which indicates the reliability of our crystalline model and the practicability of the present theoretical approach. More importantly, the computational results in this work can be treated as a good screening method to collect reasonable experimental data, which will provide a good reference for tritium source term evaluation in the SG of the HTR-PM.

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U2 - 10.1016/j.jnucmat.2019.07.036

DO - 10.1016/j.jnucmat.2019.07.036

M3 - Article

AN - SCOPUS:85073643248

VL - 525

SP - 152

EP - 160

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

SN - 0022-3115

ER -