Neptunyl (Np) interaction with green rust,

TEM study of Green Rust Sodium Sulphate (GRNa,SO4) Interacted with Neptunyl Ions (NpO2 +)

“…Hence, further investigations are required to clearly determine the nature of the Np(IV)-phase formed, and thus to achieve a safer understanding of the Np-immobilization mechanisms. The present study continues the work of Skovbjerg et al [21] and Christiansen et al [22] and GR Na,SO4 reacted with NpO 2 + is investigated using a high-resolution field-emission transmission electron microscope. In this study we focus on the fate of Np.…”

“…Indeed, the formation of GR has for instance been observed during the corrosion of zerovalent-iron reactive media [e.g., [8][9][10]. Furthermore, several studies reported the ability of GR to reduce a variety of redox-sensitive species including Cr(VI), Tc(VII), Se(IV,VI), Hg(II), U(VI), and Np(V) [11][12][13][14][15][16][17][18][19][20][21][22]. Hence, owing to its strongly reducing properties, GR is a potential candidate for attenuating the migration of redox-sensitive radionuclides in the environment.…”

“…Recently, Skovbjerg et al [21] and Christiansen et al [22] investigated the interaction of NpO 2 + with green rust of sodium sulphate form (GR Na,SO4 ) (the two papers partially report the same experiments). They showed that Np(V) is immobilized via reduction and formation of less soluble Np(IV)-species.…”

“…Christiansen et al [22] suggested that it is hydrated NpO 2 . However, this conclusion was not based on experimental evidence but the authors drew it through discussion, notably by comparing their findings with those of O'Loughlin et al [15] -who studied the interaction between uranyl and GR -and those of Neck et al [25] -who studied the reduction of Np(V) in aqueous solutions.…”

Radionuclide behaviour in the near-field of a geological repository for spent nuclear fuel

“…Reduction is highly relevant for the redox sensitive radionuclides U, Np and Tc where poorly soluble tetravalent states establish and for Se where Se 0 or Fe-selenides/sulfides are formed [162,169,185]. In case of Pu tri-and tetravalent species may form depending on pH and total Pu concentration (see Fig.…”