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Ji P.,China North Nuclear Fuel Co. | Du Y.,China North Nuclear Fuel Co. | Chi C.,China North Nuclear Fuel Co. | Wang H.,China North Nuclear Fuel Co.
IOP Conference Series: Materials Science and Engineering | Year: 2017

In order to understanding the appearance of the abnormal welding line during the CANDU fuel element end plug welding process, the analysis on the microstructure and the alloying elements distribution of three different batches of Zircaloy-4 rods, named as A753, B592 and C744, was carried out in the present study. The microstructure and localized composition of the alloys were studied by optical microscopy, X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM) and energy disperse spectroscopy (EDS). The results showed that there was no obvious difference among the three specimens. However, it was found that there appeared etch pits in the middle area of A753 batch samples. And the grain size of welding qualified C744 batch sample was greater than the un-qualified samples of A753 and B592. According to HRTEM and EDS results, the second phase particles in the Zircaloy-4 were Zr(Fe, Cr)2 phase with the Hexagonal Close-Packed (HCP) structure. The matrix belonged to α-Zr phase with the Hexagonal Close-Packed (HCP) structure. The second phase particles distributed inside the grains and at the grain boundaries of the three batches of the alloys. The size of the second phase particles in qualified sample C744 was around 200nm with the elements of Zr, Fe and Cr. However the size of the second phase particles in the un-qualified samples B592 and A753 was about 100nm, in which the elements of Fe and Cr could not be detected or only trace amount of Fe could be detected for part of the second phase particles. Therefore it may be concluded that the grain size, the second phase size and composition are the main factors to affect the welding quality of the alloy. © Published under licence by IOP Publishing Ltd.

Zhang X.,China North Nuclear Fuel Co. | Yang Z.,China North Nuclear Fuel Co. | Meng Y.,China North Nuclear Fuel Co. | Kang S.,China North Nuclear Fuel Co. | He J.,China North Nuclear Fuel Co.
IOP Conference Series: Materials Science and Engineering | Year: 2017

U-Mo alloys have been considered as the potential new advanced nuclear fuel, due to its favourable irradiation stability associated with the presence of the metastable γ-phase in the microstructure. Thus its γ-phase stability and performance are of great importance. In this work, three kinds of U-Mo alloys with the content of 6, 8 and 10wt.% Mo were prepared by non consumable arc melting technology, the homogenization annealing and heat treatment of isothermal decomposition. Through metallographic microscope, scanning electron microscope (SEM), X-ray diffraction, Brinell hardness tester, the microstructure and mechanical properties of U-Mo alloys were investigated. The results indicate that the stability of γ-phase in the U-Mo alloy is directly related to the content of Mo. With the increase of Mo, the stability of γ-phase is enhanced and the decomposition of γ-phase is delayed during the isothermal decomposition at 565°C. In addition, the mechanical properties of this alloy are closely associated with its phase rather than directly related to the content of Mo. © Published under licence by IOP Publishing Ltd.

Qi J.-B.,Shanghai University | Qi J.-B.,China North Nuclear Fuel Co. | Ru L.-L.,China North Nuclear Fuel Co. | Wu G.-X.,Shanghai University | And 3 more authors.
Rare Metals | Year: 2015

The stability, bonding, work of adhesion and electronic structure of the U/W interface with and without Ti were investigated by first principles to explore the mechanical properties of W particles enhanced U–Ti alloy matrix composite as a construction material. The calculated results indicate that the preferable orientation of the U/W interfacial structure is (001)U/(110)W crystallographic plane, Ti atoms originating from U slab are prone to diffuse into W slab through the interface, and additional Ti in U matrix is the stronger adhesion to W, with an ideal work of adhesion of 6.93 J·m−2 for U–Ti/W interface, relative to the value of 6.72 J·m−2 for clean U/W interface. The stronger adhesion performance is due to the increase in valence electron hybridization for U–Ti/W compared with U/W interface, as evidenced by the characteristic of the local density of states for the interfacial atoms. © 2015 The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg

Liu R.-Z.,Tsinghua University | Liu M.-L.,Tsinghua University | Shao Y.-L.,Tsinghua University | Liu B.,Tsinghua University | Song F.-F.,China North Nuclear Fuel Co.
Yuanzineng Kexue Jishu/Atomic Energy Science and Technology | Year: 2016

Tristructural-isotropic (TRISO) coated fuel particles in high temperature gas-cooled reactor (HTGR) were fabricated using fluidized bed chemical vapor deposition (FB-CVD) method. It is found that the pressure of the CVD system named reaction pressure is a key parameter which can influence the properties of the coated fuel particle by experimental study. In this work, the variation of the reaction pressure in the coating process and its influence on the microstructure and density of the coating layers were investigated. To control the reaction pressure, the concept of whole production line pressure assessment was proposed. Pressure analysis and balance were obtained by monitoring some pressure points in the production line. Based on the system pressure assessment, the pressure optimization was obtained which could keep the pressure balance of the whole production line and keep the stability of production process. It can be indicated that the pressure analysis is an effective method to assess the production line, which can be used to production line troubleshooting, hierarchical interlocking design and system optimization in the future. © 2016, Editorial Board of Atomic Energy Science and Technology. All right reserved.

Liu M.-L.,Tsinghua University | Liu B.,Tsinghua University | Shao Y.-L.,Tsinghua University | Niu X.-P.,China North Nuclear Fuel Co.
Hedongli Gongcheng/Nuclear Power Engineering | Year: 2012

The SiC coating layer of HTGR fuel particles is the most critical layer in hindering the release of fission products. In this paper, SiC layer was prepared in a spout fluidized bed by chemical vapor deposition on an industrial scale. High temperature oxidation experiments were carried out at different temperatures at 1400°C. The microstructure and composition were studied using different characterization methods, including EDS and SEM analysis. High-resolution SEM results showed that the oxidation started from the surface and gradually formed a punctate distribution of the oxide. The small crystal structure (~μm) of the SiC surface was very clear at the beginning and this crystal structure was oxidized at high temperatures, and disappeared gradually to form oxides of Si on the SiC surface. There was a stacking fault stress due to the different thermal expansion coefficient and elastic modulus of SiC and Si oxides, leading to the gradual formation of cracks around the punctates, and then with the increasing temperature, the crack further increased the oxidation rate of SiC, finally the formed Si oxides layer fell off from the particles. It can be seen clearly that the layer was peeling when the temperature was increased to 1400°C. But the oxidation layer was very thin (~1 μm), so the remain SiC coated layer has the same function of hindering fission products in the TRISO particles. EDS results can also validate these conclusions.

Liu Y.-H.,China North Nuclear Fuel Co. | Feng H.-N.,China North Nuclear Fuel Co. | Zhao Y.-H.,China North Nuclear Fuel Co. | Liu X.-Y.,China North Nuclear Fuel Co. | And 2 more authors.
Journal of Chinese Mass Spectrometry Society | Year: 2015

Positive thermal ionization mass spectrometry (PTIMS) method was used to determine boron isotope in ZrB2 for Na2BO2 + with m/z 88(23Na2 10BO2 +) and m/z 89 (23Na2 11BO2 +) as analytical ion. Imported high purity tantalum belt was used as sample filament. The isotope interference, coating technology, pretreatment of the ZrB2 sample were researched. There is no interference of strontium and yttrium in the background by mass peak scanning and analysis, while the effect of oxygen isotope was deducted by formula. The graphite was attached to the sample filament with diluent graphite slurry instead of graphite turbid liquid as emission reagent. The method of which used Cs2BO2 + as analytical ion was reproduced by samples coating with graphite slurry, and using diluent graphite slurry instead of graphite turbid liquid. Enhanced effect of graphite on Na2BO2 + emission was proved by comparison with the direct coating method. Although the effect was inapparent about the enhanced effect of graphite on Cs2BO2 + emission, the reduction of ion beam was inhibited effectively in analysis after adding graphite. The phenomenon shows that graphite coating method is propitious to gain stabler ion beam and improve the precision of analytical results. The value of boron isotope standard substance was reproduced, and the analytical value was consistent with the standard value. When sample quantity was 8.0 μg, acid dissolution sample application and direct fusion sample application were compared. The results show that the direct fusion sample application is not easy to introduce interference ions, and the precision is less than 0.020%. This method can shorten the time of sample pretreatment and improve the detection efficiency. ©, 2015, Editorial Board of Journal of Chinese Mass Spectrometry Society. All right reserved.

Dong G.,Beijing University of Technology | Zhang M.,Beijing University of Technology | Zhao X.,China North Nuclear Fuel Co. | Yan H.,Beijing University of Technology | And 2 more authors.
Applied Surface Science | Year: 2010

N-doped CuCrO2 thin films were prepared by using radio frequency magnetron sputtering technique. The XRD and XPS measurements were used to confirm the existence of the N acceptors in CuCrO2 thin films. Hall measurements show the p-type conduction for all films. The electrical conductivity increases rapidly with the increase in N doping concentration, and the maximum of the electrical conductivity of 17 S cm-1 is achieved for the film deposited with 30 vol.% N2O, which is about three orders of magnitude higher than that of the undoped CuCrO2 thin film. Upon increasing the doping concentrations the band gaps of N-doped CuCrO2 thin films increase due to the Burstein-Moss shift. © 2010 Elsevier B.V. All rights reserved.

Chen L.-Z.,China North Nuclear Fuel Co. | Ren Y.-G.,China North Nuclear Fuel Co. | Li A.-J.,China North Nuclear Fuel Co. | Du J.-J.,China North Nuclear Fuel Co. | Guo H.,China North Nuclear Fuel Co.
Yuanzineng Kexue Jishu/Atomic Energy Science and Technology | Year: 2015

For the preparation of ThO2 pellet meeting to heavy water reactor (HWR) fuel element technical requirements, ThO2 powder made by oxalic acid precipitation process was used as raw material. The ThO2 pellet was prepared through the granulat-ing, pressing and sintering process. The effects of granulating, pressing and sintering process on the grain size and density were analyzed. The results indicate that the specific surface area of powder, press force and sintering temperature are the main effect factors of pellet density. The driving forces of ThO2 pellet sintering and grain growth increase with specific surface area of ThO2 powder, and the ThO2 pellet with larger grain size can be acquired by using the higher specific surface area of ThO2 powder. The ThO2 pellet which can meet the HWR fuel element technical requirements of density and grain size can be prepared under the vacuum or argon atmosphere and high sintering temperature. © 2015, Atomic Energy Press. All right reserved.

Yang Y.,China North Nuclear Fuel Co. | Guo H.,China North Nuclear Fuel Co. | Wang Z.-B.,China North Nuclear Fuel Co. | He J.-M.,China North Nuclear Fuel Co. | Guo F.-L.,China North Nuclear Fuel Co.
Yuanzineng Kexue Jishu/Atomic Energy Science and Technology | Year: 2015

Boiling and sulfuric acid anodizing process were conducted on the surface of T6061A1 alloy cladding samples which had experienced the same manufacturing cycle about fuel tube and been heated for 1 h at the temperature of (450±25) ℃ for foaming annealing test. The thickness and surface morphology of preformed membranes were detected, as well as the autoclave corrosion tests were done. The result shows that boiled preformed membrane thickness is about 500 nm, and the resistance performance of autoclave corrosion is far better than that of the anodic oxidation preformed membrane. With the increase of the thickness for anodic oxidation preformed membrane, the membrane thickness increment and weight per unit area increase after each autoclave corrosion cycle. © 2015, Atomic Energy Press. All right reserved.

Ru L.-L.,China North Nuclear Fuel Co. | He Y.-B.,China North Nuclear Fuel Co. | Guo H.,China North Nuclear Fuel Co. | Liu W.-T.,China North Nuclear Fuel Co. | Cai Z.-F.,China North Nuclear Fuel Co.
Yuanzineng Kexue Jishu/Atomic Energy Science and Technology | Year: 2015

The thorium dioxide foils are used as simulation fuel pellets for the new reactor, the thickness is only 0.5-1 mm, and the diameter is 17-31 mm, with the difficulty of compaction and the severe deformation of sintering. The thorium dioxide foils were prepared by three main processes of powder granulation, compaction and sintering. The powders prepared by different methods were used for compaction foils, which surfaces quality were compared for determining optimal granulation method, and the foils prepared by compaction were used to research the sintering process including foil loading method and temperature control. The results show that adding the appropriate amount of PVA binder to thorium dioxide power before granulation and compaction can overcome the problem of stripping cracking owing to low intensity of the foil, and excellent surface quality of green foils can be acquired, meanwhile using the loading way of "foils clamped by pellets" and extending the low-temperature holding time, the foils with suitable size and flat surface can be obtained. © 2015, Atomic Energy Press. All right reserved.

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