Matjaž Koželj, MSc, started his career in 1980 in the Physics Department of Ljubljana University. He later worked for the Iskra Microelectronics factory and then, in 1989, moved to the Josef Stefan Institute (JSI) where he is still employed.  He works in the JSI Nuclear Training Centre, which was established to support training activities for Krško NPP. His involvement is as a lecturer on nuclear physics and reactor physics, laboratory exercises and radiation protection in nuclear facilities, among others. 

Mr Koželj is heavily involved in the preparation, implementation and examination of the radiation protection training courses authorised by the JSI for exposed workers and for radiation protection officers (RPO) in different organisations. He has also lectured on numerous courses organised by the IAEA and EC (through ITER and JSI). He is an Authorised Expert in Radiation Protection (RPE) and is a member of the emergency dose assessment team in the Slovenian Nuclear Safety Administration. He is currently a member of the executive board of the Radiation Protection Association of Slovenia and of the Nuclear Society of Slovenia. With effect from 1 January 2019, he is elected to the Board of the EUTERP.