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Employing the DFT+U framework we investigate the thermodynamic stability of U 3 O 8 (100) surface. The most stable structure is predicted to gradually turn from the under-stoichiometric 0 6 - to the over-stoichiometric 5 6 -slab as the oxygen chemical potential increases, showing a continuous surface oxidation process. Oxygen atoms are found to always firstly adsorb on the lower oxidized U ions. Due to the polarity compensation, significant modification of surface charge presents on considered terminations, which is transferred via both U-5 f and O-2 p states, implying the nature of U 3 O 8 as an intermediate state between the Mott–Hubbard and charge-transfer materials. It is also shown that the displacement of the outmost U 6 O 10 layer and the surface energy are strongly related to the redistribution of surface charge. The static effect between charged layers is the major factor which influences the layer displacement. The increase in surface energy is shown to be roughly linearly dependent on the amount of the surface charge transfer. [Display omitted] • The surface chemistry of U 3 O 8 (100) is dramatically influenced by polarity compensation. • U 3 O 8 (100) surface is predicted to transform from under- to over-stoichiometric as μ O increases. • U(2) is much more favorable in adsorbing oxygen atoms than U(1). • The charge transfer is accomplished via U-5 f and O-2 p states together. [ABSTRACT FROM AUTHOR]

The rate of activation of the isotope 16 O to 16 N in a typical HPLWR one pass concept was calculated using MCNP code. A mathematical model was used to track the inventory of the radioisotope 16 N in a unit mass of coolant traversing the system. The water leaving the moderator channels has the highest activity in the circuit, but due to interaction with fresh coolant at the lower plenum, the activity is downscaled. The calculated core exit activity is higher than values reported in literature for commercial boiling water reactors. [ABSTRACT FROM AUTHOR]

Highlights: [•] The double differential cross sections of neutron, proton, deuteron, triton, helium and alpha-particle emission are given. [•] All cross sections, angular distributions, and energy spectra are obtained. [•] All results are given in the energy range of Ep ⩽150MeV. [Copyright &y& Elsevier]

Zeolitic imidazolate frameworks (ZIFs) are considered promising materials to adsorb volatile iodine due to their large surface areas and high thermal/chemical stability. By using density functional theory (DFT), the volatile iodine I 2 and CH 3 I adsorption onto five different ZIFs (SALEM-2, ZIF-8, ZIF-Cl, ZIF-90 and ZIF-65) were investigated systematically, including interaction mechanisms and the inhibiting effects of potential contaminants. The long-range interactions were found to play an important role in the volatile iodine adsorption. Interestingly, it's found that secondary bonds are all formed after volatile iodine adsorption onto ZIFs. Moreover, except ZIF-65, there is a remarkable charge transfer from considered ZIFs to I 2 compared with CH 3 I. The results of adsorption energies of potential contaminants highlighted that C 6 H 6 has the strongest inhibiting effect towards volatile iodine adsorption onto ZIFs, whereas CO, NO and CH 4 have the negligible inhibiting effects. The conclusions could be useful for future design and selection of better adsorbents for capturing radioiodine, but its experimental verification is still an essential work. [Display omitted] • The binding strength of I 2 with ZIFs involved in present study is stronger than that of CH 3 I. • Except ZIF-65, there is strong host-guest charge transfer from considered ZIFs to I 2. • Secondary bonds with weak covalent interactions are all formed after I 2 /CH 3 I adsorption onto five considered ZIFs. • Benzene has the strongest inhibiting effect on I 2 and CH 3 I adsorption onto five considered ZIFs. [ABSTRACT FROM AUTHOR]

Abstract: 129I concentration in the seawater samples near a nuclear power plant was determined in the Xi''an Accelerator Mass Spectrometer (AMS) Center. Isotope dilution method was used via addition of excessive amount of stable iodine (127I) in the sample before separation, and iodine in the seawater was separated by solvent extraction, and the back extracted iodine in iodide form was precipitated as AgI, which was used as AMS target for 129I measurement. 125I tracer was added to monitor the recovery of iodine in the whole separation process. 129I/127I ratios in the prepared target were determined by AMS. The concentration of 127I in seawater samples was determined by inductively coupled plasma mass spectrometry. The results show that the 129I/127I atomic ratios in the seawater range from 8.29×10−11 to 9.45×10−10, approximately one order of magnitude higher than that in seaweed collected in the pre-nuclear era, but fall in the environmental level of global fallout. [Copyright &y& Elsevier]

Comprehension the extent and rate of U(VI) adsorption on some mineral surfaces are significant to predict their migration and transformation properties in the environmental systems. Herein, iron oxides particles supported reduced graphene oxide composites (MRGO) were successfully synthesized by in-situ chemical precipitation approach. The MRGO composites which illustrated high saturation magnetization could be likely separated using an external magnet. The experimental data illustrated that U(VI) ions could be interacted with MRGO composites through different interaction mechanisms depending on different environmental conditions. The adsorption kinetic results can be well simulated using the pseudo-second-order pattern. The pH-dependent adsorption behavior illustrated an favorable pH value of 7.5 for removal of U(VI) ions using MRGO composites. Furthermore, the adsorption regeneration of MRGO composites in simulated wastewater disposal systems was tested. Based on above mentioned, it was clear that MRGO composites could be potentially used as adsorbent for removal of actual U(VI)-bearing wastewaters. [ABSTRACT FROM AUTHOR]

Abstract: The newly established 3MV Accelerator Mass Spectrometry (AMS) facility in Xi’an, with an instrument background of 2×10−14 for 129 I/127I ratio, provides efficient analytical capability to carry out 129 I environmental tracing studies. Chemical separation methods of iodine from different types of samples have been established at the Xi’an AMS Center, including solvent extraction and combustion followed by extraction or coprecipitation depending on sample types. A carrier free method for iodine separation and AMS measurement of ultra low level 129 I in samples with low total iodine concentration has been established, which can be used for analysis of geological samples for 129 I dating. Some environmental samples collected in China have been analyzed using the developed methods. The analytical results show 129 I/127I ratios of (0.9–1.1)×10−10 for seawater collected adjacent to a nuclear power plant, and (3.02–5.43)×10−10 for soil samples collected in a less than 10km area surrounding the NPP. These values are not significantly different from those measured in remote areas, reflecting a safe nuclear environment in terms of 129 I level. [Copyright &y& Elsevier]