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[en] As an important part of nuclear power plant construction, nuclear island installation mainly involves main equipment installation, pipeline installation, associated procedure examination and other important tasks. However, due to the nuclear island installation management changing from single project to multi-projects, the problems such as professional management of nuclear island installation and the lack of technical staff become more and more prominent and become one of the key restricts to the work of nuclear island installation. Based on analysis of the single project, single-base nuclear island installation management and practice, combined with the current situation that multi-project and multi-base construction of nuclear power are carrying out at the same time, this paper proposes a new management model of nuclear island installation. (author)
[en] Highlights: • Study of HCs and Freon as TPCT working fluids for renewable energy applications. • Experimental performances of TPCTs were studied with eight working fluids. • R245fa/R152a, R600a, and R1234ze were recommended as substitutes for R134a. • Suitability of typical HTC correlations were analysed for the TPCT working fluids. • A simplified Rohsenow correlation was developed to further improve accuracy. - Abstract: Two-phase closed thermosyphons (TPCTs) are simple, efficient, and low cost heat exchangers. They have been explored for use in the renewable energy resource utilization marker and low grade thermal energy heat recovery systems. Freon R134a has been extensively used in refrigeration systems and researched as a working fluid of TPCTs; however; it has high global warming potential and operating pressure. In this paper, an experimental investigation of the performance of TPCTs charged with eight working fluids: R134a, R601, R245fa, R600a, R1234ze, R152a, R245fa/R152a, and R601/R245fa have been carried out. The experimental results showed that R245fa/R152a offered the best performance in maximum heat transfer rate. R134a outperformed the other pure working fluids, while R600a and R1234ze had close performances to that of R134a. R245fa showed marginal improvement at higher operating temperatures. The predictions of six evaporation heat transfer coefficients (HTCs) correlations, including Imura, Shiraishi, Labuntsov, Kutateladze, Cooper, and Rohsenow were compared with the experimental results. In the five constant coefficients and powers correlations, the Shiraishi and Cooper correlations had superior accuracy. The coefficients and powers of the Rohsenow correlations fitted based on the experimental data, while they had the best accuracy. Nusselt and Hashimoto-Kaminaga correlations were chosen to predict the condensation HTCs. Both of them tend to over-predict the condensation HTCs in low heat fluxes while under-predicting in high heat fluxes. The experimental results had greater agreement with Hashimoto and Kaminaga correlations.
[en] Study on the critical paths for the schedule control of nuclear power projects has been performed for reactor M310, based on the experiences from Daya Bay project and Ling Ao project. The study shows that the critical paths for the nuclear power project are from NI civil work, NI erection, commissioning of single systems directly serving the CFT to the joint-test. For NI civil work, the critical path is the main civil work of the reactor building, pre-stressing, handover of rooms for important areas, and key CW-erection interfaces; there are four critical paths for NI erection; For startup, two stages can be identified: commissioning of 16 single systems directly serving the CFT and joint-test. (authors)
[en] Large-scaled cranes are needed to hoist assemblies in civil works and installation of nuclear plants. Different cranes are required in CPR1000, EPR and AP1000 to match different site layout. Before construction, the type of cranes, the working area, as well as the transmitting path should be chosen according to the layout characters to make civil works and installation can be carried out smoothly. This article will give precept on type-choosing and layout of large-scaled cranes by analyzing the hoisting requirements in CPR1000, EPR and AP1000. (authors)
[en] We reported on the study of the thermal mechanical reliability of Cu-filled through silicon via (TSV) under 450 °C thermal loading. It was found that the voids could be generated at twin boundaries in TSV-Cu after thermal process. To study the mechanism of void formation at twin boundaries, the voided regions were characterized by focused ion beam—scanning electron microscope (FIB-SEM), the crystallographic orientation of Cu grains and the microstructure of twin boundaries was analyzed by means of electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). Stress induced voids were considered to be generated at twin boundaries because of the stress concentration induced by three possible factors: crystallographic orientation differences of Cu grains near the twin boundary, interface decohesion of twin boundary and morphology of twin boundary.
[en] A high-performance transparent electromagnetic interference (EMI) shielding material based on a graphene/metallic mesh/transparent dielectric (GMTD) hybrid structure is designed and characterized. It consists of stacked graphene and metallic mesh layers, with neighboring layers separated by a quartz-glass substrsate. The GMTD hybrid structure combines the microwave-reflecting characteristics of the metallic mesh and the microwave-absorbing characteristics of graphene to achieve simultaneously high visible transmittance, strong microwave shielding effectiveness (SE), and low microwave reflection. Experiments show that a double-graphene and double-metallic mesh GMTD hybrid structure with a mesh periodicity of 160 µ m provides microwave SE exceeding 47.79 dB in the K u-band, and an SE exceeding 32.12 dB in the K a-band, with a maximum value of 37.78 dB at 26.5 GHz. SE by absorption exceeds 30.78 dB in the K a-band, with a maximum value of 34.55 dB at 26.5 GHz, while maintaining a normalized visible transmittance of ∼85% at 700 nm. This remarkable performance favors the application of the proposed structure as a transparent microwave shield and absorber, and offers a new strategy for transparent EMI shielding. (paper)
[en] Nb-silicide-based alloys were directionally solidified in yttria moulds. As a result of thermal dissociation of yttria, the alloys were slightly contaminated with oxygen, which caused a competitive oxidation between yttrium and hafnium. The addition of 0.15 at.% yttrium reduced the oxygen increment by 42%, because the buoyant inclusions concentrated around the top surface. The yttrium addition caused a significant purification of the interaction between the yttria mould and the Nb-silicide-based alloys during the directional solidification.
[en] Three ZK60 resulting sheets with same grain size but various texture states were successfully fabricated by a combination process of hot rolling, cold rolling and annealing treatment. Subsequently, standard Erichsen tests were performed on these resulting sheets which possessed orthotropic basal texture exhibiting an egg-shaped asymmetric distribution of basal poles from the normal direction. Combining with the analysis of strain hardening ability obtained from uniaxial tension test, it could be concluded that the magnesium alloy sheets with orthotropic basal texture presented anisotropy in strain hardening ability, and their stretch formability was dependent on the strong texture in one direction of magnesium alloy sheets. That was to say, texture weakened only in single direction could not improve the stretch formability. This conclusion was supported more by the direction of crack propagation which was parallel to the weak texture direction of magnesium alloy sheet.
[en] The least-square method is commonly employed to verify the spatial straightness in actual three-dimensional measurement process, but the uncertainty of the verification result is usually not given by the coordinate measuring machines. According to the basic principle of spatial straightness least-square verification and the uncertainty propagation formula given by ISO/TS 14253-2, a calculation method for the uncertainty of spatial straightness least-square verification is proposed in this paper. By this method, the coefficients of the line equation are regarded as a statistical vector, so that the line equation, the result of the spatial straightness verification and the uncertainty of the result can be obtained after the expected value and covariance matrix of the vector are determined. The method not only assures the integrity of the verification result, but also accords with the requirement of the new generation of GPS standards, which can improve the veracity of verification
[en] As an ideal modifier, the cage-type polyhedral oligomeric silsesquioxane (POSS)-silanol creates a strong bonding with the solder without agglomeration. It has been shown that the addition of POSS-silanol improves both the mechanical performance and the solder's resistance to electromigration. This study further examined the effect of the addition of POSS-silanol on whisker growth in a Sn3.0Ag0.5Cu (SAC305) solder. The whisker growth was studied for pure SAC305 and SAC305 modified with POSS-silanol under isothermal aging and thermal cycling conditions. The results indicate that the added POSS-silanol not only reinforces the solder joint, but also inhibits whisker formation under both thermal aging and thermal cycling conditions. POSS-silanol can therefore be considered a promising modifier material which enhances the reliability of solders. During the thermal aging process, the added POSS-silanol was found to inhibit the interdiffusion of Sn and Cu atoms at the interface region, thereby preventing the formation of Cu6Sn5 but promoting the conversion of Cu6Sn5 into Cu3Sn. During the thermal cycling process, the added POSS-silanol significantly inhibited whisker formation and the deformation of the interface by stiffening the solder matrix and decreasing the driving force for whisker formation. - Highlights: • A novel reinforcement particle, POSS, is introduced in solders. • POSS reduces the possibility of whisker formation in both aging and thermal cycling. • We explain the whisker mitigation mechanisms in both aging and thermal cycling.