To investigate the effects of the environmental conditions on the dissolution of irradiated nuclear fuels, the Spent Fuel Autoclave Leaching Experiments (SF-ALE) project is being carried out at SCK CEN, in collaboration with Forschungszentrum Jülich and the Belgian Agency for Radioactive Waste and Fissile Materials NIRAS/ONDRAF. A state-of-the-art spent fuel leaching setup was developed to examine the release of various radionuclides and fission gases from well-characterized UOX and MOX spent fuel segments, under different environmental conditions [1]. The first phase of the project included 733 contact days (approximately two years), and was completed in September 2020 by the complete renewal of the leaching solution. This also marked the start of the second phase of the project, in which continued leaching experiments will expand the total duration to 1279 contact days (approximately 3.5 years) on the same spent fuel segments. In the meantime, leaching data of the first phase have been acquired and processed. In the present contribution we will discuss and interpret the leaching results obtained during the first phase, and describe the transition to phase two of the project and its prospected outcomes
