Austenitic steel is a candidate material for Supercritical Water-Cooled Reactor. This study is to investigate stress corrosion cracking behavior of HR3C under effect of supercritical water chemistry. A transition phenomenon of water parameters was monitored during a pseudo critical region by water quality experiments at 650 °C and 30 MPa.The stress-strain curves and fracture time of HR3C were obtained by slow strain rate tensile tests in supercritical water at 620 °C and 25 MPa. The concentration of dissolved oxygen was 200-1000 μg/kg and the strain rate was 7.5×10^<-7>/s. Recent results showed the failure mode was dominated by intergranular brittle fracture. The relations of oxygen concentration and fracture time were nonlinear. 200-500 μg/kg of oxygen accelerated the cracking but a longer fracture time was measured when oxygen concentration was increased to 1000 μg/kg. Chromium depletion occurred in the oxide layer at the tip of cracks. Grain size increased and chain precipitated phases was observed in the fractured specimens. These characteristics were considered to be contributive to the intergranular stress corrosion cracking.
Supercritical carbon dioxide (S-CO2) Brayton cycle has attracted substantial attention in recent years due to its higher efficiency, simpler cycle layout and lower cost. S-CO2 Brayton cycle is not only suitable for next generation nuclear reactors, but also considered in other conventional and renewable energy applications including fossil-fueled power plant, ship propulsion, and solar energy system and so on. In 2010, Nuclear Power Institute of China (NPIC) initially started to investigate the concept and some fundamental issues related to S-CO2 power conversion technology in China. This paper presents recent research and development progress obtained in China including thermodynamic analysis and evaluation, thermohydraulic investigation, code development, and integral test loop design. The research plan in the near future for S-CO2 power conversion technology in China is also presented.
A two-dimensional MoS2 catalyst uses edge sites for catalytic activity while its basal plane remains inert in heterogeneous catalysis. To significantly boost the intrinsic activity of MoS2, a metal insertion–deinsertion procedure was developed to prepare Pt–MoS2–x catalysts. Of which, Pt4+ partially substituted Mo4+ in the basal plane of 1T-MoS2–x and then Pt was deinserted from the basal plane after reduction and finally located at the neighborhood of its original position, where abundant edge sites were created and rich Pt–edge interfaces were formed in the "inert" basal plane of MoS2. This Pt–MoS2–x exhibited high activity in hydrodeoxygenation of p-cresol, presenting in 100% oxygen removal at a low temperature of 120 °C and almost no sulfur loss nor deactivation in recycling runs. A Pt–MoS2–x catalyst was also efficient in hydrodeoxygenation of diverse lignin model compounds and lignin-derived bio-oil. This methodology opens up an innovative strategy for the design of robust MoS2 catalysts featuring the activation of the basal plane and provides an energy-efficient alternative for the upgradation of raw bio-oil.
SuperCritical Water Reactor(SCWR) applies water beyond the thermodynamic critical point as the coolant, which aims to achieve high efficiency around 45% compared to 33% for existing commercial light water reactors. In order to raise the reactor operating temperature and reactor criticality, the existing SCWR core designs are quite different from those of boiling water reactors or pressurized water reactors, which further effect their safety performance and safety system design. A comprehensive review on existing developed SCWR reactor concepts of different countries, including pressure-vessel type and pressure-tube type SCWRs, as well as thermal, fast and mixed spectrum SCWRs, is carried out to deeply explain the core design features of SCWR. The development methods of safety analysis tool for SCWR are also summarized to shed a light on the key scientific difficulties and how these problems are solved up to now. All the special techniques applied to enable trans-critical simulations are still unphysical and lack of validation. Moreover, the safety characteristics of existing SCWR concepts are discussed. Based on these review work and discussions, the research status of SCWR concepts, safety analysis tool development and safety characteristics are clearly presented. Safety analysis tool validations and more comprehensive accident evaluations should be further carried out to better illustrate the safety performance of these SCWR concepts.
The oxidation and carbonization behavior of typical alloy materials in high-temperature CO2 environment is studied based on thermodynamic analysis technology, including the analysis of the oxidation and carbonization performance of the medium environment, as well as the corrosion behavior of alloy materials. Besides, the oxide film characteristics of T91 and 800H alloys, including phase composition and morphology structure, are studied at 500 ℃ and 650 ℃. The comparative analysis of thermodynamic analysis results and corrosion test results shows that the characteristics of the material oxide film obtained from thermodynamic analysis are basically consistent with the corrosion test results.
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