Do Thi Mai Dung

Dr. Thi-Mai-Dung Do is an Assistant Professor at the Extreme Energy Density Research Institute, Nagaoka University of Technology. She received her B.Eng. and M.Eng. degrees in Materials Science and Technology from Hanoi University of Technology and subsequently moved to Japan to complete her Dr. Eng. in Materials Science Program at Nagaoka University of Technology. Her doctoral research focused on producing oxide nano-rod arrays on alloy solid solutions.

Her early research investigated high-temperature material phenomena, including the oxidation mechanisms of zircaloy, the high-temperature behavior of cesium, and its chemical interactions with structural materials like stainless steel, alongside the synthesis of complex cesium-molybdenum and cesium-silicon systems.

Currently, at the Extreme Energy Density Research Institute, Dr. Mai Dung expands her expertise into functional materials for environmental and medical applications. Her research includes the characterization and development of geopolymers for nuclear waste immobilization, alongside producing target materials like b-MoO₃ for medical radioisotope generation. Looking forward, her interests extend to emerging medical isotope targets, especially ²²⁶Ra for ²²⁵Ac production.

Abstract Title: High-Temperature Chemical Behavior and Phase Interactions of Cesium Molybdate with Stainless Steel Under Severe Accident Conditions

The Fukushima Daiichi accident released significant radioactive cesium (¹³⁴Cs and ¹³⁷Cs) into the environment. While CsOH(g) dominates at near the core fuel temperature (> 2000 K), Cs₂MoO₄ becomes the primary gaseous species upon cooling in the primary circuit and condenses at 1550 – 1900 K. Once deposited onto upper structural components (e.g., steam separators, driers, piping) Cs₂MoO₄ undergoes complex high-temperature interactions with stainless steel. Under thermal and steam gradients, Cs₂MoO₄ can condense into polymolybdates like Cs₂Mo₂O₇ or react with steel constituents (Fe, Cr, trace Si) to form secondary phases like Cs₂CrO₄ and Cs₂Si₄O₉, altering Cs retention and re-evaporation kinetics.

This study systematically investigates the phase stability, vaporization kinetics, and reaction behavior of Cs₂MoO₄ on stainless steel under dry and humid atmospheres. Microstructural and phase analyses reveal complex Cs retention dynamics, highlighting the high solubility of surface Cs-bearing phases alongside the preferential migration and incorporation of Mo into the Fe-rich oxide scale. By distinguishing bulk-bound from surface-washable Cs species, these empirical insights refine boundary conditions for severe accident source-term models and Fukushima Daiichi decommissioning strategies.