Yaolin Zhao

First-principles study of atomic hydrogen adsorption and initial hydrogenation of Zr(0001) surface

The atomic hydrogen adsorption on Zr(0001) surface is systematically investigated by using density functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics is studied in detail for a wide range from 0.11 to 2.0 monolayer. At low coverage of 0<Θ≤1.0, the most stable adsorption site is identified as the on-surface hcp site followed by the fcc site, and the adsorption energy gradually increases with the coverage, thus, indicating the higher stability of on-surface adsorption and the tendency to form H clusters. The origin of this stability is carefully analyzed by the projected density of states and the charge distribution showing the Zr-H chemical bonding with a mixed ionic/covalent feature during the surface hydrogenation. In addition, the minimum energy paths as well as the activation barriers of the on-surface diffusion and the penetration from on-surface sites to subsurface sites are also calculated. At ...

Fabrication of oxidized multiwalled carbon nanotubes for the immobilization of U(VI) from aqueous solutions

Herein, the surface properties of oxidized multiwalled carbon nanotubes (MWCNs) were characterized by adopting XRD, SEM and FTIR. The sorption behaviors of U(VI) from wastewater by oxidized MWCNs were investigated by adopting batch technique. The experimental results demonstrated that sorption behaviors of U(VI) on oxidized MWCNs were dependent on ionic strength at low pH, and independent of ionic strength at high pH. The ion exchange and outer-sphere surface complexation were main mechanism for sorption of U(VI) on oxidized MWCNs at low pH, whereas inner-sphere surface complexation and coinstantaneous co-precipitation were primary mechanism at high pH.

Evaluation of permutite for removal of radiocobalt from nuclear wastewater

A synthetic zeolite, commercially available as permutite was tested for removing radiocobalt from aqueous solutions by sorption. The sorption process was studied as a function of contact time, pH, ionic strength and solid content by batch technique. The results revealed that the process is dependent on the pH and ionic strength under ambient conditions. The kinetic sorption was fitted well by a pseudo-second-order rate equation. The thermodynamic parameters (ΔH0, ΔS0, ΔG0) suggested that sorption behavior of Co(II) is a spontaneous and endothermic process. The study shows that permutite has excellent potential for disposal of wastewaters containing radiocobalt.

Simulation of (16)O (n, p) (16)N reaction rate and nitrogen-16 inventory in a high performance light water reactor with one pass core.

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.

Utilization of chitosan–clinoptilolite composite for the removal of radiocobalt from aqueous solution: kinetics and thermodynamics

Chitosan–clinoptilolite composite was prepared and tested for removing radiocobalt from aqueous solution. The composite was characterized with Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy coupled with energy dispersive X-ray analysis. The sorption of Co(II) on chitosan–clinoptilolite composite was pH-dependent and ionic strength-independent. The kinetic sorption was fitted well by a pseudo-second-order rate equation. The thermodynamic parameters (ΔH0, ΔS0, ΔG0) revealed that the sorption of Co(II) on chitosan–clinoptilolite composite was spontaneous and endothermic. The study showed that chitosan–clinoptilolite composite had excellent potential for the treatment of wastewater containing radiocobalt.

Transport of 125I in compacted GMZ bentonite containing Fe-oxides, Fe-minerals or Cu2O

A systematic investigation of the transport of 125I in compacted GMZ bentonite containing Fe-Oxides, Fe-minerals or Cu2O additive was carried out by through-diffusion method. The obtained results indicate that all of the additives have positive effects on retarding the 125I diffusion in compacted GMZ bentonite. Especially for the Cu2O additive, the corresponding effective diffusion coefficient is greatly reduced. It is mainly attributed to the particular interactions between the metal ions introduced by additives and iodide ions.

Primary Simulation: The Yield of 14C Produced in PWR During Normal Operation

The mechanisms of the radionuclide 14C production and releasing from pressurized water reactor (PWR) nuclear power plant (NPP) are simply described in the paper. The yield calculation model for 14C produced in PWR is offered in this work. The averaged neutron flux in reactor core under normal operation condition is simulated with MCNP5 according to the simplified Daya Bay NPP reactor core structure and other parameters, the yields and activities of 14C in different parts of the reactor core including fuel, fuel cladding, nitrogen impurities in fuel and coolant are calculated and compared with Origen2. The simulation results showed that the yields of 14C produced in different parts change linearly with operation time. The rations of 14C introduced by nuclear reactions in coolant, fuel cladding, nitrogen impurities in fuel and fuel element core are 64%, 16%, 12%and 8%, respectively. The dominant part of 14C is induced by neutron reactions with coolant. The primary study results may offer some reference values for 14C releasing in environment control from NPP.Copyright

Measurement of 129I Level Around a Nuclear Power Plant by Accelerator Mass Spectrometer

129 I is a long-lived (15.7M year) radioisotope of iodine. It can be used as a tracer for monitoring nuclear proliferation and the 129 I/127 I ratio can be used to evaluate the radiation contamination level. Nowadays a great number of nuclear power plants will be built in China, but the data of 129 I concentration in environmental samples around nuclear power plants are limited. Accelerator Mass Spectrometer (AMS) whose detection limit is about 10−14 , is one of the best instruments for analyzing environmental samples. The methods of making 129 I target samples for AMS measurement from different type samples were studied, and the processing system for water and soil samples were established. Six surface seawater samples were collected at different distance away from a nuclear power plant in China. These samples were measured by Xi’an AMS. The ratios of 129 I/127 I in the seawater samples are between 0.829 × 10−10 and 9.451 × 10−10 , and the average value is about 3.518 × 10−10 . The ratios of 129 I/127 I in these samples are compared with other measurement results under different circumstances in other parts of the world. The results show that this nuclear power plant has not released superfluous 129 I into environment after several years’ operation. Since the AMS and sample processing system are established, we will do much work on nuclear technology application with 129 I tracer.© 2010 ASME