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Chun, Hoje,Kang, Joonhee,Han, Byungchan American Chemical Society 2018 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.122 No.22
<P>Safe control and removal of radioactive iodine gases (I-129 and I-131) leaking from the accidents in chemical factories or nuclear industries are of importance because of their critical damage to the biosphere. We study the adsorptive removal of the off-gaseous iodine using transition metals of group 10 and group 11 under humid conditions. First-principles calculations enable to capture key adsorption natures of iodine and water molecules on the adsorbent surfaces. The underlying mechanism is analyzed by thermodynamic free energies, electronic structures, and surface work function changes. Our results unveil why silver metal shows notably outstanding efficiency for the iodine removal. We propose an innovative and insightful map to guide sorting out the best metal adsorbents and impregnants for dramatic improvement of the adsorptive removal of the radioactive iodine gas. Our study is useful for preventing critical risks from chemical and nuclear accidents.</P> [FIG OMISSION]</BR>
Minjoon Hong,Hoje Chun,Byungchan Han 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1
The success of machine learning approach to identify key correlation in large database is critically controlled by the reliability and accuracy of the data. Here, we demonstrate that rigorous material properties of radioactive nuclear fuels can be obtained by integrated approach of first principles calculations and the machine learning approach. The reliable database is established by density functional theory and molecular dynamics simulations, which is the input of the machine learning to analyze any correlation among the database. The outcomes are applied to evaluate thermodynamic, kinetic and electrochemical properties, which plays a key role for safe management of spent nuclear fuels.
Jung, Hyunwook,Kang, Joonhee,Chun, Hoje,Han, Byungchan Elsevier 2018 Journal of hazardous materials Vol.341 No.-
<P><B>Abstract</B></P> <P>Using first principles calculations we unveil fundamental mechanism of hydrolysis reactions of two hazardous chemicals PCl<SUB>3</SUB> and POCl<SUB>3</SUB> with explicit molecular water clusters nearby. It is found that the water molecules play a key role as a catalyst significantly lowing activation barrier of the hydrolysis via transferring its protons to reaction intermediates. Interestingly, torsional angle of the molecular complex at transition state is identified as a vital descriptor on the reaction rate. Analysis of charge distribution over the complex further reinforces the finding with atomic level correlation between the torsional angle and variation of the orbital hybridization state of phosphorus (P) in the complex. Electronic charge separation (or polarization) enhances thermodynamic stability of the activated complex and reduces the activation energy through hydrogen bonding network with water molecules nearby. Calculated potential energy surfaces (PES) for the hydrolysis of PCl<SUB>3</SUB> and POCl<SUB>3</SUB> depict their two contrastingly different profiles of double- and triple-depth wells, respectively. It is ascribed to the unique double-bonding O=P in the POCl<SUB>3</SUB>. Our results on the activation free energy show well agreements with previous experimental data within 7kcalmol<SUP>−1</SUP> deviation.</P>