Fabrication Technology for MOX Fuel Containing AmO₂by an In-cell Remote Process

Abstract

An in-cell remote fabrication technique was developed for MOX fuel pellets containing 3 and 5% americium (Am-MOX fuel pellet). The fuel pellet was fabricated by means of conventional powder metallurgy. A series of fuel pellet fabrication apparatuses were systematically installed in the alpha-gamma cell (hot cell) to protect workers from a strong -ray exposure from 241 Am, and were remotely controlled from a panel in the operation room outside the hot cells as much as possible. From a preliminary UO 2 pellet fabrication run, ball milling of powder for 4 h, pressing at 4 t/cm 2 and sintering at 1,700 C for 2 h were determined as a good fabrication, but the ball milling time was too short for the UO 2 and Am-PuO 2 powders of different morphologies to be uniformly mixed. Then, the 5% Am-MOX fuel pellet of density more than 93% T.D. which is proper to the irradiation in FBR was successfully fabricated by extending the ball milling time for more than 10 h. It was, furthermore, found that the complete cleanup of the powder feeder was necessary in the transition of fabrication runs to prevent the formation of uranium and plutonium spots in the pellets.

Actinide Oxidation State and O/M Ratio in Hypostoichiometric Uranium–Plutonium–Americium U0.750Pu0.246Am0.004O2–x Mixed Oxides

“…Similarly to the present study, a lower homogeneity of cation distribution than that of samples from reference might explain why Vigier et al have managed to determine low O/M ratios from XAS experiments without observing a fast reoxidation at room temperature. Finally, the fabrication of Am-bearing uranium–plutonium mixed oxides studied by Osaka et al , is thoroughly described in refs , . These samples were elaborated by a conventional powder metallurgy route and also evidenced significant heterogeneity of cation distribution likely to affect their O/M ratio.…”

Chemical bonding in actinyl(v/vi) dipyriamethyrin complexes for the actinide series from americium to californium: a computational investigation

“…This is attributed to the nearly common preference for the trivalent oxidation state (OS) (An 3+ /Ln 3+ ) along with their similar ionic radii in aqueous solutions (as a result of lanthanide/actinide contraction). 4–6 The small charge density difference between actinides and lanthanides proves to be insufficient amidst similar oxidation states and ionic radii and thereby limits the ability of chelating ligands for An/Ln separation. However, actinides are able to reach high OSs including +V and +VI while lanthanides cannot exist in high OSs.…”

Extracting the Americyl Hydration from an Americium Cationic Mixture in Solution: A Combined X-ray Absorption Spectroscopy and Molecular Dynamics Study

“…Americium is formed as a byproduct of the irradiation of uranium by neutrons as well as of Pu decay . It is of great interest, since it is one of the main species responsible for the high radiotoxicity of minor actinoids in nuclear fuel waste. − To engineer such a waste recycling process, to understand the biological hazard of americium, or to study its geochemical speciation, detailed knowledge of its complex solution chemistry is necessary. Unlike lanthanoids, the aqueous chemistry of actinoids is very rich, since each element has a distinct behavior with different stable oxidation states and species .…”

“…The stabilization of americyl species requires the presence of highly oxidizing media . The ability to examine this higher oxidation state solution chemistry would yield relevant information on how these forms could be incorporated in new separation processes of minor actinoids in nuclear fuel recycling. − …”