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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. Source

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 Source

Guo Y.-C.,Chongqing University | Zhou S.,Chongqing University | Gao C.,Chongqing University | Wang J.,China North Nuclear Fuel Co. | Zhang J.,China North Nuclear Fuel Co.
Hedongli Gongcheng/Nuclear Power Engineering | Year: 2013

In view of the characteristics of deuterium pellet rows, a dynamic pellet row measurement model is established, and the automatic detection system for deuterium pellet row is designed. Setting up measurement platform and using HMI for controlling the 18 rows of pellets loading, compaction, relaxation, transportation and other actions, and 2-D dynamic measure the length through laser triangulation between the ring end plane of moving pellet row and the datum plane by non-contract way. The system achieved pellet row length dynamic detection. It obtains the resolution over 10 μm, the accuracy over 100 μm, and the speed 18 rows/sec; moreover, it also has such function as data display in real time, system state detection, security alarm, and emergency shutdown. The actual operation results show that the system poses security, rapid, stable and reliable characteristics, and well meets the needs of pellet control and detection in industrial automation. Source

Qi J.,Shanghai University | Qi J.,China North Nuclear Fuel Co. | Guo H.,China North Nuclear Fuel Co. | Zhang J.,Shanghai University | And 2 more authors.
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2013

We use the first principles plane wave pseudopotential method calculated the mechanical property with respect to the quenching and aging process of uranium-1.3 wt.% titanium alloy, including the elastic modulus, bulk modulus, Young's shear modulus and the ideal tensile strength, meanwhile deeply research on the mechanical property mechanism changes through t-he electronic structure. The results show that t-he elastic modulus and ideal tensile strength of quenching state are 198GP and 21.2GP, respectively, and slightly improving through aging treatment. The variation of energy and electronic structure of uranium-titanium solid solution in process of quenching indicate the phase transition from γ phase (cubic structure) to α′ phase (orthorhombic structure) lead to improve to the mechanical property. In process of aging, at the beginning the metastable supersaturated solid solution appears Guinier-Preston (G.P) zones, which are aggregate of solute atoms in the uranium matrix, further improving the tensile strength. Then U2Ti (hexagonal structure) precipitates present in over-aged process as a result of decomposition of metastable α′phase and reduce the tensile strength. The result shows that the G.P/matrix and precipitate/matrix interfaces have ideal work of adhesion are 15.2eV and 12.5eV, respectively. Our results demonstrate theoretically quenching and aging heat treatment strengthening effect of uranium-titanium alloy. Copyright © 2013 by ASME. Source

Zou H.,Beijing Institute of Technology | Huang G.-Y.,Beijing Institute of Technology | Feng S.-S.,Beijing Institute of Technology | Guo H.,China North Nuclear Fuel Co. | And 2 more authors.
Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology | Year: 2013

Uranium-titanium alloy fragments are characterized by high density and impressive penetration capability. Based on the fire gun driving platform, five kinds of typical fragments with titanium content of 0.5%~1.0% were tested with the fragments penetrating into target of A3 steel plate to study penetration features of uranium-titanium alloy fragments. The terminal ballistic characteristics of uranium-titanium alloy fragments penetrating steel target were obtained. And mass, velocity and kinetic energy changes of different recipes after fragments penetration were studied in the experiments. The experiments show that bright light is produced as main penetrator hitting target. Damage form of steel plates mainly is plugging and combines with ductility penetration. Furthermore, fragment of titanium content of 5% has the minimum loss of kinetic energy. Fragment of titanium content of 0.75% can cause most serious shear damage. Source

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