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Abstract: The paper studies the adsorption features of 239Pu in phyllitic slate and clay media through static experiment method. The two different geo-media were collected from a site for disposing very low level waste (VLLW) as experimental samples. Experimental results have shown that an adsorption equilibrium time of 239Pu in phyllitic slate and clay is approximately 10 days, and the adsorption coefficient (Kd) B Bvalues of phyllitic slate and clay are about 6000ml/g and 2700ml/g, respectively. The experimental result of particle size effect indicates when adsorption of plutonium in particle samples increases, the KBdB values of these two geo-media increase while the particles decrease in size. And the experimental impact on aqueous phase pH value reveals that Kd of 239Pu in creases at higher aqueous phase pH value, illustrating stronger adsorption capacity. Experimental data are also measured through the curve fitting, KBdB values are thus obtained theoretically. [Copyright &y& Elsevier]

Stable mineral colloids play a role in the mobilization of actinide contaminants in the environment. In this paper we present a method to isolate and identify colloids released from high surface area sorbents associated with a proposed clay mineral barrier in a nuclear waste repository. The mineral colloids, which have a strong tendency to remain dispersed in solution, were separated from Al 13 - or (Ce Al)-pillared clay sediment, adsorbed on glass together with hydrolyzed vanadium(IV) species and studied by a variety of techniques including grazing-incidence X-ray scattering (GIXS), small-angle X-ray scattering (SAXS), Fourier transform-infrared spectroscopy (FT-IR) and atomic force microscopy (AFM). We show that the clay platelets are dimensionally orientated in the continuous, transparent 100 nm thick film until the onset of vanadium oxides above 350 °C. Organic matter and the secondary mineral quartz limit the swelling capacity of the platelets, an indication that the stable colloids originate from a part of the native clay that could not be intercalated by aluminum cations. X-ray scattering from oriented clay films intercalated by aluminum- and mixed cerium/aluminum oxo-hydroxy cations are also investigated by the GIXS technique. Unlabelled Image • A continuous, vanadium hydroxide/clay-colloid thin film was self-assembled on glass. • Clay nanoplates dimensionally orient within the 100 nm thick film. • Platelet orientation is preserved until the onset of vanadium oxides above 350 °C. • The platelets are potentially useful for actinide/clay-colloid transport studies. [ABSTRACT FROM AUTHOR]

The Alxa region (Inner Mongolia, China) is one of the areas preselected for use as a geological repository of high-level radioactive waste in China. Radioactive waste produces radioactive rays during long-term storage, and the cumulative absorbed dose in 1000 years can significantly exceed the maximum of 0.7 MGy, thereby challenging the long-term adsorption stability of clay. This study employed 60Co gamma (γ)-rays to irradiate clay in air under a dose rate of 10 kGy/h. The changes in the internal structure and mechanisms of clay under different gamma radiation doses (1, 2, and 3 MGy) were investigated. Additionally, the adsorption properties of irradiated clay for U(Ⅵ) were tested under different conditions. The clay samples underwent minimal structural changes following high-dose irradiation, and the interlayer spacing was altered due to the fractured framework, dehydroxylation, and radiolysis of water. After irradiation, the Fe (Ⅱ) content in clay was significantly increased, unlike Fe (Ⅲ) content. The adsorption mechanisms of clay before and after the experiments were verified, revealing that the adsorption capacity of irradiated clay to U(Ⅵ) is reduced. [Display omitted] • Gamma irradiation caused H 2 O radiolysis and skeleton fracture in clay samples. • The Fe (Ⅱ) content in clay significantly increased after gamma irradiation. • The uranium adsorption capacity of clay decreased after gamma irradiation. • Uranium adsorbed on clay mainly in the form of UO 2 2+. [ABSTRACT FROM AUTHOR]