I received my Ph.D. in 1995 at the University of Wisconsin-Madison, in the USA in the area of nuclear safety especially experimental investigation on the steam explosion on a large scale. After the degree, I moved to JAERI, currently, JAEA in Japan as a JAERI research fellow and had worked on the steam explosion phenomena in various contact modes in the ALPHA facility for three years. After JAERI I moved to the KTH Royal Institute of Technology in Sweden working on the mechanistic steam explosion in a single drop with synchronized simultaneous visualization techniques using X-ray and photography. After the Fukushima accident, I moved back to Korea and worked at the Division of Advanced Nuclear Engineering (DANE) in POSTECH focusing on severe accident research specifically studying in-vessel retention and corium pool convection and ex-vessel coolability, steam explosion, MCCI, mitigation measures as well as developing various analytical tools and methodology for risk-significant severe accidents assessment. In parallel, I worked on boiling and condensation in various micro/nano-structured surfaces with chemical characteristics of hydrophobicity and hydrophilicity, supercritical CO2 power cycles and heat exchanger design, and thermally enhanced accident tolerant fuel cladding, etc. Now I work at the Nuclear Research Institute of Future Technology and Policy under the Department of Nuclear Engineering in Seoul National University, continuing research and education on nuclear safety and fundamental multiphase heat transfer and fluid flow. Especially, I am currently focusing on developing a computational platform for severe accident analysis for nuclear power plants.