[en] Strong electronic stopping of high energy and high degree of ionization ions can lead to Coulomb explosion in which electron stripping causes repulsive interaction among positively charged atoms along ion tracks. Using molecular dynamics simulations and introducing an ionization pulse which lasts for different time periods, Coulomb explosion and structural evolution up to a time scale of 30 ps were modeled in SiC. The time periods of ionization pulses play an important role to determine radius of melting/amorphous regions after structural relaxation. For a long ionization, the amorphous/melting region can expand and become larger than the originally ionized region, while the opposite is observed for short ionization. (authors)

[en] Oxide dispersed strengthened (ODS) steel is an important candidate for Gen-IV reactors. Oxide embedded in Fe can help to trap irradiation defects and enhances the strength of steel. It was observed in this study that the size of oxide has a profound impact on the depinning mechanism. For smaller sizes, the oxide acts as a void; thus, letting the dislocation bypass without any shear. On the other hand, oxides larger than 2 nm generate new dislocation segments around themselves. The depinning is similar to that of Orowan mechanism and the strengthening effect is likely to be greater for larger oxides. It was found that higher shear deformation rates produce more fine-tuned stress-strain curve. Both molecular dynamics (MD) simulations and BKS (Bacon-Knocks-Scattergood) model display similar characteristics whereby establishing an inverse relation between the depinning stress and the obstacle distance. It was found that (110)_oxide II (111)_Fe (oriented oxide) also had similar characteristics as that of (100)_oxide II (111)_Fe but resulted in an increased depinning stress thereby providing greater resistance to dislocation bypass. Our simulation results concluded that critical depinning stress depends significantly on the size and orientation of the oxide

[en] Strong electronic stopping of high energy ions can lead to Coulomb explosion in which electron stripping causes repulsive interaction among positively charged atoms along ion tracks, if the ionization time is long enough. Using molecular dynamics simulations and introducing an ionization pulse which lasts for different time periods, Coulomb explosion and sputtering from the free surface were modeled in Si. The main issues include analyzing the number of sputtered atoms variation with ionization time, comparing the surface sputtering phenomenon caused by Coulomb explosion with different intensity and finding the Coulomb explosion strength which is not enough to cause sputtering. The results show that: At the beginning of the Coulomb explosion, sputtering phenomenon is obvious and the number of sputtering atoms on the surface keep growing, but latter the number of sputtering atoms fluctuated because of the attractiveness of atoms inside; Different ionization time different sputtering phenomenon, the longer the ionization time, the more violent the explosion, the more sputtering atoms; If the ionization time last only 6 fs, there will not be sputtering atoms by Coulomb explosion. (authors)

[en] Based on the design principle of neutron multi-sphere spectrometer in this paper, the detector with multi-counter inserted into sphere moderator was machined. The measurement equipment with multi-path of the counter was connected. The dose estimation mode by unfolding of a few channels was adopted under the double-sphere measurement. The neutron field of terrestrial cosmic ray was measured for the double sphere. The annual dose is about 78 γSv/a at Harbin area. Compared with the results of the multi-sphere spectrometer, the relative deviations of neutron fluence rate and neutron ambient dose equivalent rate for double-sphere are less than 3% and 12%, respectively. (authors)

[en] By means of molecular dynamics, diffusion behaviors of oxygen dumbbell interstitial defect in UO₂ were simulated under the influences of tensile strain direction and tensile strength with different substrate temperatures. The diffusion of oxygen dumbbell interstitial defect is three-dimensional, and the ability of diffusion is relation to substrate temperature and tensile strength. Using simulation results, the diffusion coefficient of oxygen dumbbell interstitial defect was conformed. From the simulation, oxygen dumbbell interstitial defect is always arranged in <111> direction during diffusion process, higher temperature and larger tensile strain, more obvious the diffusion becomes, especially with increasing tensile strength along <111> axial, the direction of diffusion is mainly along <100> axial under strain or not. The results provide the basis for the study to radiation damage effects in UO₂. (authors)

[en] The anthropomorphic computational phantoms are applied to the evaluation of dose distributions from internal or external radiation. The Non-Uniform Rational B-spline (NURBS) or Polygon Meshes phantoms describe the human anatomical features realistically and realize the adjustment of the parameters for each part of human body easily. The organs and tissues are segmented from the sectioned color slice images by 3D-Doctor. Based on the anthropometric and the reference data of China Reference or Asia Reference, NURBS surfaces are constructed from Polygon Meshes through the Rhinoceros software. In terms of Voxelization, BINVOX software is used to read the interior of surfaces into a series of Voxels. A set of programs are coded in MATLAB to assign a single code for each organ and tissue, respectively, and integrate the voxel groups to a phantom with the voxel resolution of 0.22 cm × O.22 cm × O.22 cm and 0.2 cm × 0.2 cm × O.2 cm for female and male, respectively. All parts of the final phantom are matched to their reference organ masses within a tolerance of 5%, and provide data support for the simulated calculation. (authors)

[en] The development of nuclear technology is closely and inseparably related to the improvements of materials irradiation performance. The irradiation damage of nuclear materials is an important issue of characteristics and difficulties. Because of the excellent features, SiC becomes one of the candidate materials for the cladding material and structure material in fast neutron reactor and fusion reactor. As one of the polytypes, 4H-SiC has prospective important applications in a strong irradiation environment. In this work, molecular dynamics (MD) simulation was performed to study the irradiation-induced cascade damage in single-crystalline 4H-SiC to get the microscopic evolution during the irradiation, in the aim of getting access to the detail that we cannot get from experiments. The software LAMMPS was used to simulate the damage formation process and the recovery process. The results showed that the initial project direction, the temperature and PKA energy exerted significant effects on the number and morphology of defects. (authors)

[en] Various researches have indicated the relative advantages of ferritic/martensitic (FM) steels over austenitic and other steels currently in use in light water reactors, and have regarded them as the most promising structural materials in both present and future reactors. Fe-Cr are the model alloys of these steels. Continuous exposure to severe irradiation environment will no doubt affect the microstructure of these materials significantly, which can subsequently manifest as observable changes in the materials' physical properties. Various experimental and simulation literatures were reviewed in this paper with the aim of further understanding the irradiation effects of Fe-Cr alloys, which are the reference model systems for high chromium steels. Factors such as; solute type and concentration, irradiation dose, temperature, number of displacements per atom, dpa (fluence/dose), as well as type and energy of irradiating particle, among other things, affect the production and evolution of radiation damage in Fe-Cr alloys. Researchers' findings on the way some of these factors affect the alloy under irradiation condition are presented in the paper. While the addition of Chromium (Cr) was found to improve the performance of FM steels by strongly suppressing void swelling, minimizing the effect of increase in irradiation hardening with decrease in dose rate, and so on, the effect of its content on Fe-Cr alloys under irradiation condition is however not clearly understood by the experimental studies, perhaps due to factors such as the nonmonotonic variation of its content with properties like void swelling. Primary radiation damage production and evolution, as presented in various Molecular Dynamics (MD) simulation literatures reviewed, determine the macroscopic response of a material to irradiation, thus making it paramount to understand. Insight into the atomic processes leading to changes in mechanical properties of materials can be gained through multi-scale computer simulations. Rigorous efforts are therefore needed in this regard to help enhance our understanding of the effects of irradiation on materials and the way they can best be mitigated during design in order to help ensure safe and reliable operation of nuclear power plants. (author)

[en] Oxide-dispersed-strengthened (ODS) steel has excellent mechanical, thermodynamic and radiation resistant properties, which makes it an important candidate material for high-temperature reactors applications. Radiation stability of oxide is very important to study at the atomic level. In present case molecular dynamics (MD) simulation is used to study stabilities of Y₂O₃ particles in ODS steel as a function of particle sizes. The size dependence is obvious for particle sizes larger than 2.8 nm. Furthermore, the stabilities depend on charges of Y and O atoms. (paper)

[en] Using high temperature activated sodium flying ash and carboxymethyl chitosan as raw material to prepare carboxymethylchitosan wrapping fly-ash adsorbent (CWF), combined with iron-carbon micro-electrolysis treatment of simulated and actual printing and dyeing wastewater. The conditions for obtaining are from the literature: the best condition for CWF to treat simulated printing and dyeing wastewater pretreated with iron-carbon micro-electrolysis is that the mixing time is 10min, the resting time is 30 min, pH=6, and the adsorbent dosage is 0.75 g/L. The results showed that COD removal efficiency and decoloration rate were above 97 %, and turbidity removal rate was over 90 %. The optimum dyeing conditions were used to treat the dyeing wastewater. The decolorization rate was 97.30 %, the removal efficiency of COD was 92.44 %, and the turbidity removal rate was 90.37 %. (paper)