Divergence in the Relativistic Mean Field Formalism: A Case Study of the Ground State Properties of the Decay Chain of 214,216,218U Isotopes

A new α-emitting has been observed experimentally for neutron deficient 214U which opens the window to theoretically investigate the ground state properties of 214,216,218U isotopes and to examine α-particle clustering around the shell closure. The decay half-lives are calculated within the preformed cluster-decay model (PCM). To obtain the α-daughter interaction potential, the RMF densities are folded with the newly developed R3Y and the well-known M3Y NN potentials for comparison. The alpha preformation probability (Pα) is calculated from the analytic formula of Deng and Zhang. The WKB approximation is employed for the calculation of the transmission probability. The individual binding energies (BE) for the participating nuclei are estimated from the relativistic mean-field (RMF) formalism and those from the finite range droplet model (FRDM) as well as WS3 mass tables. In addition to Z=84, the so-called abnormal enhancement region, i.e., 84≤Z≤90 and N<126, is normalised by an appropriately fitted neck-parameter ΔR. On the other hand, the discrepancy sets in due to the shell effect at (and around) the proton magic number Z=82 and 84, and thus a higher scaling factor ranging from 10−5–10−8 is required. Additionally, in contrast with the experimental binding energy data, large deviations of about 5–10 MeV are evident in the RMF formalism despite the use of different parameter sets. An accurate prediction of α-decay half-lives requires a Q-value that is in proximity with the experimental data. In addition, other microscopic frameworks besides RMF could be more reliable for the mass region under study. α-particle clustering is largely influenced by the shell effect.

Effect of Oxide Shell on Aluminium Nanoparticle Oxidation Using Molecular Dynamics Simulation

Molecular dynamics simulation using reactive force field (ReaxFF)potential was implemented to study the oxidation mechanism in aluminium particles with two different alumina shells. That is, without an oxide shell and with a 1 nm oxide shell. In particular, this research investigated the atomic diffusivity of the system on the oxide shell effect. The results showed that in the heating process, oxygen molecules were adsorbed on the surface of the shell and then diffused to the particle core as the heating temperature increased. The diffusivity of oxygen molecules in the aluminium core which causes the oxidation process to occur, shows that the particles without the oxide shell are faster than the particles with the oxide shell. Although after relaxation, there are similarities in having an oxide shell. However, the thickness is different. This shows that the coating on Al particles can inhibit the rate of oxidation. The thickness of the oxide shell also affects the rate of oxidation.

Study on Rotor’s Vibration Characteristics of Helium Circulator of HTR

The helium circulator is used in the 10MW High Temperature Gas-cooled Reactor (HTR-10). The circulator operates at helium condition in order to transport the core heat to the steam generator. Rotor is a key component of the helium circulator. The rotor vibrates during the operation of the helium circulator. The study of the vibration characteristics of the rotor can provide important design parameters for the helium circulator. The effect of the shell on the rotor in the helium circulator is ignored in the usual research and analysis. In this paper, the working process of the rotor considering the shell effect was studied by theoretical analysis, and the vibration characteristics of the rotor considering the shell effect with various types and parameters was studied by finite element method (FEM). More accurate ranges of the rotor parameters which ensure the helium circulator to operate normally were determined. The shell increases the degree of freedom (DOF) of the rotor, which makes the analysis of the motion process of the rotor more complicated. The results show that the different parameters of the shell on the rotor play an important role in the analysis results of the vibration characteristics. The analysis results considering the shell effect of the rotor are more accurate than the usual analysis results.