The quantity of radioactive fission products, which can be released out of irradiated nuclear fuel in accidental conditions, is a key data for the design of safety components of a Nuclear power plant. This release was largely studied in the case of severe accidents but less is known for temperature below 1400°C. The aim of the Ph.D. Work will consist in using new in-situ characterization tools that are now available on MERARG furnace at the IRESNE institute in CEA-Cadarache in order to improve the characterization of volatiles PFs in this temperature range. The Ph.D. Student will have to design and run thermal treatment on irradiated nuclear fuel making use of in and ex-situ gamma spectrometry, in-situ optical sighting device and measurement of the PO2 of the furnace atmosphere. This work will be performed with the support of experimental team at IRESNE. The Ph.D. Student will also participate to the interpretation of the results in close collaboration with experimental and modeling teams at IRESNE. In order to test the proposed mechanism, the Ph.D. Student can also perform separate-effects experiments on simulating materials in collaboration with team at university. This work will be valued both in industrial context with technical notes and in academic context with paper in journals and attending scientific conferences.