To study the effect of reprocessing on the microstructure and corrosion resistance of Zr-Sn-Nb alloy, the original plates of Zr-Sn-Nb alloy were hot-rolled, cold-rolled and recrystallized to obtain the reprocessed plates. The microstructure of both plates was observed with a scanning electron microscope (SEM), a transmission electron microscope (TEM) and electron backscattering diffraction (EBSD). The original plates and reprocessed plates were put into a static autoclave for 300 days in 360 °C/18.6 MPa water. The relationship between the microstructure and corrosion resistance of the Zr-Sn-Nb alloy was discussed. The coarse deformation grains with twins and fine recrystallized grains were obtained, and grain sizes became smaller. The Ostwald ripening of second phase particles (SPPs) happened, and the average size of SPPs increased. Some SPPs changed from an HCP structure to an FCC structure. Reprocessing made the transition advance, which is related to the accelerated evolution of cracks in the oxide film and the increase in metal-oxide film interface roughness. The deterioration of corrosion resistance is closely related to the change of grain size, SPP size and SPP structure.

Differential scanning calorimetry (DSC) was used to study non-isothermal kinetics of α→β transformation of Zr-0.5wt%Sn-0.15wt%Nb-0.5wt%Fe-0.25wt%V alloy. The DSC curves were measured from room temperature to 1030 °C at the heating rate of 15, 20, 30, 50°C /min respectively. The Flynn-Wall-Ozawa (FWO) method was used to get the activation energy (E) of α→β transformation at different conversion ratios. Then the values of activation energy obtained were modified by Ozawa iterative equation. The kinetic mechanism functions of α→β transformation were investigated by Criado-Ortega methods. The results show that the activation energy is related to conversion ratios. It means α→β transformation is not a simple one-step reaction but a complex multi-step reaction. The most probable kinetic mechanism functions are different in different temperature ranges, which are -ln(1-x) for ≤830 °C, [-ln(1-x)]1/2 for 834~848 °C, [-ln(1-x)]2/5for 850~856 °C and [-ln(1-x)]1/3 for 858~868 °C respectively.

The high-cycle fatigue (HCF) experiments of 6XN stainless steel and alloy 825 were conducted under bending and rotating loads at room temperature (RT) as well as at 550°C in air. The results indicate that the fatigue limited stress of 6XN at RT is higher than that of 825, which consistent with the order of their tensile strength. The oxidation rate of the specimen increased at 550°C, therefore the fatigue life of the specimen decreased, among them 6XN was more sensitive to high temperature with the larger decreasing tendency which make the fatigue limited stresses of the two alloys more closer at 550°C. While 825 is more sensitive to the stress cycles, both materials have good resistance to high cycle fatigue when comparing their experimental data with the calculated value from the empirical formula. The fracture morphology presents the areas of crack initiation, crack growth and fracture, and the fracture area has much dimples.

The paper briefly introduces the overall objective, technical index and RD plan of Supercritical Water-Cooled Reactor (SCWR), with detailed description on projects and subjects of RD (Phase I ) on Key Technologies for SCWR, and summarizes a lot of initiatives and original research achievements in the aspects of design RD, experimental research and material RD. The CSR1000 conceptual design was established with our own intellectual property.

One of the most important procedures for fabrication of Uranium Nitride fuel is the synthesis of uranium nitride powders with high purity and good sintering ability.The carbothermic synthesis process of uranium nitride powder by reaction of UO2 powder with Carbon and nitrogen has been studied,and the effect of mole ratio of carbon to uranium,atmosphere controlling,reaction temperature and time on the content of uranium nitride powder has been discussed in this paper.The results show that uranium nitride powder with higher purity can be fabricated by using suitable mole ratio of carbon to uranium(2.3-2.4) and reaction pro-cedures.

The factors with effects on the grain size in Gd2O3-UO2 pellets have been investigated by metalloscope and image analyzer. We have investigated the effects on the grain size in Gd2O3-UO2 pellets due to the sintering atmosphere, blending methods, pellets position in sintering furnace, and additive U3O8, ammonium oxalate and oxides (Al, Ti, V) in Gd2O3-UO2 pellets. The results have shown that grain growth and grain size distribution homogeneity of Gd2O3-UO2 pellets were enhanced by mixing methods using ball process, additive of oxides (Al,Ti,V) and sintering of low oxidizing atmospheres. The effect of adding U3O8 and ammonium oxalate on the grain growth of pellets is not obvious.