Description and thermal simulation of the DIAMINO irradiation experiment of transmutation fuel in the OSIRIS reactor

French GENIV sodium-cooled fast reactor (SFR) system could include Americium (Am) recycling in the radial fertile blankets located in the outer core regions. An issue related to this option is the lack of knowledge regarding the in-pile behaviour of the Am-bearing blanket (AmBB). The DIAMINO separate-effect experiment was irradiated in the OSIRIS Material Test Reactor (MTR) with the goal of studying AmBB gaseous release and swelling as a function of temperature, AmBB microstructure and gas production rate. A brief description of the experiment is first provided, in terms of objectives and planning. The innovative design developed for the DIAMINO experiment is described in details. The DIAMINO irradiation time history is then summarized and the first results of non-destructive post-irradiation examinations are given. The LICOS fuel design code of the PLEIADES platform was used for the thermo-mechanical modelling of the DIAMINO experiment. The Pleiades platform, co-developed by CEA and its industrial partners EDF and FRAMATOME, gathers several fuel performance codes, each generally dedicated to the fuel element of a particular nuclear system. For its part, the LICOS code allows performing studies on innovative fuel elements or on the design of irradiation devices for instance. The thermo-mechanical modelling of the DIAMINO experiment device using the LICOS code is detailed in the paper together with the validation of the computations on the basis of some experimental temperature measurements performed on an in-pile mock-up of the experiment. The use of the simulation tool for the monitoring of the AmBB sample temperature under irradiation and for the post-irradiation calculations is explained and illustrated through some examples. (authors)