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With the rapid development of nuclear power in China, the amount of spent fuel keeps increasing, which makes the demand for safe and suitable casks to store and transport spent fuel more prominent. Due to China’s national policy of “closed nuclear fuel cycle” and the uncertainties in the construction of reprocessing facilities, the configuration of spent fuel storage and transport cask has been directly related to the safety of nuclear power plants operation. Based on the demand of spent fuel storage and transport in China, this paper analyzes the requirement of different modes of storage and transportation and different loading contents for casks, such as 12ft / 14ft spent fuel loading, compatibility with short-term storage and transportation, and off-site transportation of dry storage canisters, etc. In order to ensure safety and control cost, this paper also analyzed the applicable standards, transport restrictions and optimization design objective for the optimal design of spent fuel storage and transport cask, and puts forward the optimal configuration and design method of the storage and transport cask based on the analysis of key concerns, which could provide reference for the configuration and design of spent fuel storage cask.

The Ar atmospheric pressure plasma was found to be an excellent laboratorial source for green aurora emission. However, the characteristic and production mechanism of the green aurora emission of the Ar atmospheric pressure plasma are still not clear. In this work, an Ar plasma in a long glass tube which emits intense green aurora light is investigated. With the long glass tube, it can be concluded that the green aurora emission in the Ar plasma is not owing to the mixture of Ar plasma plume with the surrounding air. It is also found that the green aurora emission often appeared beyond the active electrode when the active electrode is placed at the downstream of the gas flow. The green emission disappears when the traces amount of O2 or N2 (about 0.05%–0.07%) is added to Ar. This is because the O2 molecules deactivate the upper state O(1S), which results in the decrease of the green emission. On the other hand, when N2 is added, Ar metastable atoms are quenched by N2, which results in the decrease of O atoms and eventually leads to the decrease of the green emission intensity. The intensity of the green aurora emission increases when the driving voltage frequency increases from 1 to 10 kHz. More importantly, it is found that the green aurora emission is not affected when a grounded stainless steel needle is in contact with the plasma plume. Thus, the green emission is not driven electrically. All these findings are helpful for the understanding of the physics and its applications of atmospheric pressure plasma jet in space physics, laser physics and other application areas.

Constructing tubular graphitic carbon nitride homojunctions is an attractive endeavor to accelerate the dissociation of its Frenkel excitons and charge transfer dynamics, but the realization of this strategy remains a major challenge. Herein, carbon nitride homojunction with open tubular interior, porosity and interconnected feature has been developed via one-step pyrolyzing urea and l -cysteine. The experimental results and DFT calculations indicate that such unique tubular S-scheme homojunctions not only apparently boost in-plane exciton dissolution and suppress the inversive charge recombination via built-in electric field, but also decrease Gibbs free energy of intermediate hydrogen absorption. Thus, the tubular carbon nitride homojunctions display an excellent hydrogen production (4548.4 μmol/g/h), which is 35-fold improvement than that of pristine carbon nitride, outperforming the most reported donor-acceptor-based carbon nitride homojunctions and tubular carbon nitride. This work provides useful guidance to rational fabrication of S-scheme carbon nitride homojunction with positive exciton splitting and interfacial charge transfer for energy and environmental applications.

A plasma scalpel is one of the few applications of plasma medicine widely used in the clinic, but its ignition mechanism is poorly understood. This paper investigates the ignition phase of a plasma scalpel by obtaining the electrical waveforms, vaporization dynamics, plasma production and the plasma spectrum. Additionally, equivalent circuit and physical models are proposed based on the results. Two kinds of vapor layers are formed in plasma production. One is produced by Joule heating, which occurrs at the initial stage and the other is maintained by plasma heating at the stable discharge stage. When the plasma is generated, the vapor layer will become much thinner, leading to a significant increase in the electric field. The waveforms indicate the discharge has two kinds of patterns: asymmetric and symmetric patterns. The plasma intensity in the asymmetric is much stronger than the symmetric pattern. The fitted OH spectrum reveals that the gas temperature of the plasma can reach 2600 K, which can sustain the thin vapor layer. According to the broadening of the Hα line, the electron density is estimated to be about 7.1 × 1015 cm−3. Furthermore, when the stable vapor layer is formed, the impedance of the gap increases from 70 Ω to 2000 Ω when the plasma is established. The electron density is estimated again according to the plasma impedance to be about 1015–1016 cm−3.

Owing to its distinctive photon energy range, vacuum ultraviolet (VUV) emission plays a key role in diverse photo-induced natural and technological processes. Atmospheric-pressure plasma produced VUV is central to resolve long-held issues in dynamics of natural (e.g., lightning) and laboratory (e.g., streamer) plasmas. Challenging the seemingly unavoidable vacuum systems used to prevent VUV emission quenching by ambient gases, here we report the first observation of vacuum-free generation of stable sub-110 nm VUV emission from atmospheric-pressure plasmas jetted into open air and atmospheric air plasma. Emission from atomic helium at 58.4 nm is observed from a nonequilibrium atmospheric pressure plasma jet (N-APPJ), jetted directly into ambient air. In a similar experiment, we also report VUV emission from excited nitrogen species in an atmospheric pressure discharge in ambient air. The photon emissions detected expand the window of photo-induced processes beyond ~10 eV commonly achievable by existing non-excimer VUV plasma sources, and enables direct photo-excitation and ionization of molecular species such as CO2 and many others. The thus-enabled direct photoionization of O2, O, and N species further justifies the role of direct photoionization in the dynamics of natural and laboratory atmospheric-pressure plasmas and informs the development of the relevant plasma photoionization models, which currently largely sidestep the sub-110 nm domain. These findings can make contribution to the complement of photoionization model of lightning, streamer, and other plasmas, open new avenues to quantify the yet elusive role of photoionization in the plasma dynamics.

Summary A new buckling equation in horizontal wells is derived on the basis of the general bending and twisting theory of rods. The boundary conditions of a long tubular string are divided into two categories: the sum of the virtual work of bending moment and shear force at the ends of tubular strings is equal to zero, and the sum of the virtual work of bending moment and shear force at the ends is not equal to zero. Buckling solutions under different boundary conditions are obtained by solving the new buckling model. For the boundary conditions of the first category, the buckling solutions are identical with previous results. For the boundary conditions of the second category, the buckling solutions are different from the results under the boundary conditions of the first category. The results indicate that buckling behaviors depend on both the axial force and the boundary conditions. Compared with previous results, buckling solutions of the new model provide a more comprehensive description of tubular-buckling behaviors.

The helix plasma was found in a sealed quartz tube with/without a helical coil on the outer surface of the quartz tube before. The reason for the helix structure of the plasma is unclear. In this paper, an additional high voltage pulsed DC power supply is applied to the external helical coil to control the helix plasma inside the tube. The parameters of the additional power supply including the amplitude, the phase difference, the pulse width and the repetition frequency are adjusted. It was found that, when the voltage of the additional power supply is adjusted to 1.8 kV, the helix plasma plume looks like the original helix plasma without helical coil. However, their propagation speeds for the two cases are significantly different. In addition, when the pulse width and the repetition frequency of the voltage on the helical coil are adjusted, several interesting behaviors of the plasma plume are observed. Finally, an equivalent circuit model for the plasma propulsion process with the additional helical coil is presented considering the long discharge circuit as numerous capacitances and resistances series-parallel connected and the propagation process of the long plasma plume as the process of charging the paralleled capacitances. It is believed all the results discovered in this paper are helpful for better understanding of the mechanism of the helix plasma.

A chiral plasma plume has recently been generated inside a dielectric tube without the use of an external magnetic field. In this paper, we seek to further study the key properties of such a chiral plume to improve our understanding of how this interesting structure is generated and controlled. The chiral plume is generated by externally mounting a stainless steel helical coil or a ring onto the dielectric tube. By changing the pitch of the helical coil, the pitch of the plasma plume can be controlled, with the shape of the plume following the shape of the helical coil. The addition of the helical coil significantly expands the range of parameters under which the chiral plasma plume appears. When the frequency of the applied voltage increases, additional stable discharge channels appear between the adjacent helices. The addition of two helical coils results in the formation of two chiral plasma plumes, which follow the shape of the helical coils. When a metal ring is placed on the outside of the tube, there is no chiral plasma plume between the high voltage electrode and the ring; however, a chiral plasma plume appears on the right side of the ring if the distance between the ring and the high voltage electrode is small. These findings suggest that the chiral plasma can be effectively modulated and guided using an externally mounted helical coil, which acts as the floating/actual ground to reduce the impedance of the discharge and as such contributes to the emergence of the chiral plasma plume behavior.

OH radicals and O atoms are believed to be two of the most important reactive species in various biomedical applications of atmospheric pressure plasma jets. In this study, the effect of the skin moisture on the density distribution of OH and O close to the surface of the ex vivo pig skin is investigated by using laser-induced fluorescence technology. The skin moistures used in this study are 20%, 40%, 60%, and 80%, respectively. The experiment results indicate that, at a gas flow rate of 0.5 L/min, when the skin moisture is increased, the OH density close to the skin surface increases, while the O density decreases. On the other hand, when the gas flow rate is increased to 1 L/min, the OH density close to the skin surface is less sensitive with the moisture of the skin surface. Besides, when the skin moisture is 80%, the OH density increases with the increase in the concentration of H2O in the working gas and it reaches its maximum 7.9 × 1013 cm−3 when the concentration of H2O in the working gas is about...

Abstract It is difficult to determine real helical configuration by the current energy method. This paper describes an analytical solution based on equilibrium method, which represents the real configuration of helically buckled tubular subjected to axial and torsion loading in horizontal wells. New results of axial changes, the maximum bending stress and contact force in tubular are derived from the solution. P. 517

There has been concern for the crash safety of one kind of minibus in China because of its short, flat front-end structure. The minibus did not have enough crushable space for a frontal impact, and it had, in fact, failed to pass the Chinese vehicle safety regulations in frontal impact tests. This paper presents a method to improve the crashworthiness and occupant safety of this minibus. The design method, consisting of component tests and finite element analysis, focused both on the crashworthiness of the vehicle structure and occupant safety. An optimised design was obtained. The improved structural design has been implemented for the minibus. The time and cost of the redesign has been lowered substantially with the help of component tests and finite element analyses. We have shown that these procedures were effective for improving the crash safety of this minibus for the Chinese market.