Irradiation performance and first examinations of Americium bearing blanket fuel from the MARINE irradiation experiment

Americium (Am) is a strong contributor to the long-term radiotoxicity of high-level waste from nuclear fuels. Transmutation of long-lived nuclides like ²⁴¹Am by irradiation in nuclear reactors is therefore an option for the reduction of radiotoxicity and heat production of waste volumes to be stored in a repository. The MARINE irradiation experiment is the latest in a series of European experiments on americium transmutation (e.g. EFTTRA-T4, EFTTRA-T4bis, HELIOS, MARIOS, SPHERE) performed in the High Flux Reactor (HFR) in Petten (The Netherlands). The development and irradiation of MARINE was carried out in the framework of the collaborative research project PELGRIMM of the EURATOM 7th Framework Programme (FP7). Dismantling was completed and post-irradiation examinations (PIE) were started within the Dutch national research programme PIONEER. Destructive PIE is foreseen within the Euratom H2020 funded project PATRICIA. The main objective of the MARINE experiment is to study the in-pile behaviour of uranium oxide fuel containing 13% of americium and to compare the behaviour of sphere-pac versus pellet fuel, in particular the role of microstructure and temperature on fission gas and helium release dynamics on fuel swelling. The MARINE experiment was irradiated for 359 Full Power Days in the HFR in 2016 and 2017. This paper discusses results from irradiation, i.e. power and temperature history and transmutation rates as well as preliminary results from post irradiation examinations, assessing a.o. clad strains and helium and fission gas release and first ceramographic observations, putting a preliminary upper bound on fuel swelling.