Fabrication and characterization of minor actinides bearing fuels obtained by conventional powder metallurgy process

Application of the UMACS process to highly dense U1−xAmxO2±δ MABB fuel fabrication for the DIAMINO irradiation

“…Only precise atmospheric conditions can prevent AmO or Am volatilization and promote efficient pellet sintering [12]. But even under these conditions, low-density samples (d < 92% TD) [3] are generally obtained with reactive sintering.…”

“…In the case of homogeneous recycling, MA are added up to 5 at.% of heavy metals in MOX fuels which constitute the entirety of the core [2]. For the heterogeneous mode, which is at present the main focus of research, MA are integrated in specific fuels known as Minor Actinide Bearing Blankets (MABB), because of their peripheral arrangement in the core [3]. In this mode, MA are added to UOX fuels in higher concentration (from 7 to 20 at.% of the heavy metals).…”

“…Indeed, in complement to the MARIOS experiment [3], DIAMINO's chief objective is to study, after performing the irradiation of U 1Àx Am x O 2±d discs, the influence of the composition and of the microstructure on helium release and fuel swelling. One particular goal is to verify that the open porosity network can reduce the fuel swelling due to He release through comparative study of highly porous and highly dense pellets.…”

“…For that experiment, four sets of samples corresponding to two compositions (x = 0.075, 0.15) and two microstructures (dense or tailored porosity) had to be produced complying with DIAMI-NO's strict specifications. But until now, even for the MARIOS experiment, the comparison between dense and porous samples was tricky due to the inability to obtain dense samples which do not present a significant degree of open porosity [3]. To overcome this limitation, a dedicated fabrication process was developed and patented [4]: UMACS (Uranium Minor Actinides Conventional Sintering).…”

“…This novel method for MABB fuel fabrication, based on conventional sintering, differs from that usually developed for MOX or MABB fabrications, as reactive sintering under a controlled atmosphere is traditionally employed to prepare such samples. The porous samples were fabricated following a process previously used for the MARIOS program [3][4][5][6][7] which offers a reliable way to prepare pellets exhibiting a high open-porosity ratio. As this process has been previously described, this paper first details the general description of the UMACS process and then briefly discusses the mechanism associated to the porous process (Part 2).…”