Prof. RNDr. Pavel P. Povinec, DrSc., Professor at the Faculty of Mathematics, Physics and Informatics of the Comenius University in Bratislava, retired Head of the Radiometrics Laboratory of the IAEA-MEL in Monaco, former Head of the Department of Nuclear Physics and Vice-Dean of the Faculty of Mathematics and Physics. He is recognized expert with over 50 years of experience in low-level radioanalytical and nuclear science (rare nuclear decays), in environmental (radionuclides as tracers, radiocarbon dating), and space physics (radionuclides in lunar samples and meteorites). At IAEA-MEL he was responsible for the development of radiometric (including underground laboratory) and mass spectrometry methods (ICP-MS, AMS) for marine radioactivity studies. He led several international projects on assessment of dumping of radioactive wastes, on impacts of nuclear weapon test sites, on worldwide marine radioactivity studies (WOMARS), on submarine groundwater discharge studies (SGD), on the development of global marine radioactivity databases (GLOMARD/MARIS), etc. After his return to the Comenius University, he established at the Faculty of Mathematics, Physics, and Informatics a Centre for Nuclear and Accelerator Technologies (CENTA) focusing on the development of IBA and AMS methods and their wide applications in nuclear, material, environmental, and biomedical sciences. In recent years he has been focusing on assessment of environmental impacts of the Fukushima accident. In 2017 he got Hevesy Medal Award for his contribution to nuclear sciences. He published more than 20 books and book chapters and more than 700 scientific papers with more than 12,000 citations (Google Scholar), organized more than 20 international conferences, and delivered more than 50 invited talks.Prof. Dr. Katsumi Hirose, Professor at the Laboratory for Environmental Research at Mount Fuji, Tokyo, former visiting Professor at the Sophia University in Tokyo, retired Head of the Geochemical Research Department of the Meteorological Research Institute in Tsukuba. He is internationally recognized expert with 45 years of experience in investigations of natural (cosmogenic, primordial, radiogenic) and anthropogenic radionuclides as tracers for better understanding of interactions between various objects in the systems as well as between different compartments/ecosystems, important for protection of the environment against radioactive contamination. His research carrier started from studies of metal complexation with organic ligands in solution at Nagoya University, conferred PhD degree from Nagoya University. Dr. Hirose worked at environmental radioactivity field including geochemistry, marine chemistry and atmospheric chemistry in Meteorological Research Institute. In the Marine Chemistry and Biogeochemistry field, Dr. Hirose developed chemical speciation of trace metals in seawater including plutonium and natural actinides based on physical chemistry. He was given Marine Chemistry Award "Ishibashi Award in 2006. In the field of environmental radioactivity, Dr. Hirose developed studies on marine and atmospheric behaviors of anthropogenic radionuclides especially plutonium as tracers, participating international projects and expeditions. He was given Geochemistry Award "Miyake Award in 2009. He made a large contribution to elucidate environmental effects and assessment for the Fukushima Daiichi Nuclear Power Plant accident in 2011. In the 45-years research carrier, he published over 220 scientific papers with more than 6000 citations (Google Scholar) and 16 books (including book chapters, reviews and others).