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Tagawa Hiroaki 《Journal of Nuclear Materials》1974,51(1):78-89
The present state of knowledge of the phase relations and thermodynamic properties of the uranium-nitrogen system is given. Emphasis is placed on the nonstoichiometric and thermodynamic properties of uranium sesquinitride. The present paper consists of two parts. The first part is on the phase relations; an equilibrium phase diagram is proposed, and the relationship between structure and lattice parameter for the α-U2N3-UN2 system is shown. The second part deals with thermodynamic properties of UN and α-U2N3; the data on decomposition pressures, specific heats, and heats and free energies of formation are summarized and evaluated. 相似文献
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The fuel of civil nuclear plants, UO2, melts at 3120 K. During an hypothetical severe accident, urania, submitted to high temperatures and various oxygen potentials, presents a wide non-stoichiometry range: the melting temperature of UO2±x, related to oxygen potential, decreases in all cases. In this scenario, urania could react with other materials, firstly zircaloy, and the melting temperature of (U, Zr)O2±x still decreases. That is why the critical assessment of the O-U binary system including the non-stoichiometry range of urania, is a major step to a correct thermodynamic modelling of multicomponent systems for nuclear safety. The very numerous experimental information has been compiled and analysed. The associate model was used for the liquid phase, and a sublattice model for UO2±x; U4O9−y, U3O8 and UO3 were treated as stoichiometric. Phase diagram and thermodynamic properties have been calculated from the optimised Gibbs energy parameters. The calculated consistency with the experimental ones is quite satisfactory. 相似文献
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Won S. Park Tae Y. Song Byoung O. Lee Chang K. Park 《Nuclear Engineering and Design》2003,219(3):395-223
In order to transmute the long-lived radioactive nuclides such as transuranics (TRU), Tc-99, and I-129 in LWR spent fuel, a preliminary conceptual design study has been performed for an accelerator driven subcritical reactor system, called HYPER (HYbrid Power Extraction Reactor). The core has a hybrid neutron energy spectrum which includes fast and thermal neutrons for the transmutation of TRU and fission products, respectively. TRU are loaded into the HYPER core in a TRU–Zr metal form because a metal type fuel has very good compatibility with the pyro-chemical process which retains the self-protection of transuranics at all times. On the other hand, Tc-99 and I-129 are loaded as pure technetium metal and sodium iodide, respectively. Pb–Bi is chosen as a primary coolant because Pb–Bi can provide a good spallation target and produce a very hard neutron energy spectrum. As results, the HYPER system does not need any independent spallation target system. 9Cr–2WVTa is used as a window material because this advanced ferritic/martensitic steel is known to have a good performance in the highly corrosive and radiative environment. The support ratios of the HYPER system are about 4–5 for TRU, Tc-99, and I-129. Therefore, a radiologically clean nuclear power, i.e. zero net production of TRU, Tc-99 and I-129 can be achieved by combining 4–5 LWRs with one HYPER system. In addition, the HYPER system, having good proliferation resistance and high nuclear waste transmutation capability, is believed to provide a breakthrough to the spent fuel problems the nuclear industry is facing with. 相似文献
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利用纳米金刚石对多种分子具有较强吸附能力及团聚时特殊的空间构型,依次将异硫氰酸荧光素(FITC)、10-羟基喜树碱(HCPT)及转铁蛋白(TF),负载于纳米金刚石(NDs)上,形成复合物,使NDs成为具有多种功能的药物载体。使用透射电镜、红外光谱仪、紫外分光光度仪等对NDs及其复合物进行表征及分析,用荧光显微镜及细胞存活率检测方法观察,并检测了复合物的细胞效应。结果表明,HCPT在NDs上3天的吸附量为42.5%;存活率结果显示,复合物组的细胞存活率明显低于单独HCPT组,TF-HCPT-ND复合物组的存活率最低;荧光显微镜下,观察荧光标记的复合物孵育Hela细胞3h后,TF-HCPT-ND组的荧光强度明显高于HCPT-ND组,这与TF-HCPT-ND组的细胞存活率最低的结果相符。本文为构建纳米金刚石的多功能药物靶向输运系统提供了基础。 相似文献
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In order to clarify the Zr-rich corner of the Zr-N-O ternary system, a series of nitridation and controlled low-pressure oxidation heatings were made on zirconium metal plates. The experiments were made in separated reaction sequences, which were (1) oxidation of pre-nitrided zirconium, and (2) simultaneous nitridation and oxidation of zirconium. Low-partial pressures of oxygen were obtained by using a redox couple of either Mo/MoO2 or Cu2O/CuO. The samples were characterized by X-ray diffraction, optical microscopy, and electron probe micro analysis. Experimental results were coupled with a preliminary thermodynamic analysis with a sublattice formalism to draw a provisional ternary isotherm at 1373 K. 相似文献
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Linear stability analysis in the frequency domain is performed to reveal the basic mechanism of coupled nuclear-thermal instabilities in a boiling channel. It is found that the Ledinegg instability will not occur due to the coupling of the void-reactivity feedback and the hydrodynamic feedback. Besides the phase-change number Np and Jacob number Ja, the Froude number Fr and the fuel-time-constant τM are found to be the parameters determining the density-wave instability. It is also found that the Froude number effect on the density-wave stability becomes stronger when the void-reactivity feedback is involved, and that the lower the Fr number the less stable the system. The result reveals that there exists a region in which the void-reactivity feedback loop is unstable, and this has a strong effect on the stability of the system. A non-dimensional fuel-time-constant number is proposed, with which the stability boundary is better presented in the range of Froude numbers of interest. 相似文献
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讨论了模糊控制在核子秤系统中的应用,表明它在非线性过程、弛豫时间长以及无法用数学方法精确描述的过程控制中具有很大优点,并给出了模糊变量、隶属度函数以及模糊控制规则。最后比较了模糊控制与PID控制的噪声扰动。 相似文献
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A thermodynamic model of the Np-Zr system is developed using the CALPHAD method, and a review of previous work performed on this system is presented here. In general, results obtained are in good agreement with those proposed from experimental observations. It is found that the nature of reactivity of Np with Zr, is different from that of U and Pu: an expected elevation of melting point of Np-Zr alloys was not seen and a miscibility gap existed between the high-temperature bcc phases of Np and Zr. Formation enthalpy of the bcc phase obtained from the model is compared with results from KKR-ASA-CPA calculations. Lattice stabilities of various phases in the system are compared to values obtained from first-principles LDA and GGA calculations. The δ-NpZr2 phase is modeled as a non-stoichiometric phase with a C32 structure, similar to what has been determined for the δ-phase in the U-Zr system. This phase is analogous to ω-phase in pure Zr, which is stabilized at high pressures. Two different possibilities for stability of the δ and ω phases have been proposed in the present work. Finally, calculated changes in enthalpy versus temperature are plotted for two alloys to guide future experimental work in resolving important issues in this system. 相似文献
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The uranium-silicon phase diagram is a key system to predict the possible interaction between the fuel kernel (U, Pu)C and the inert matrix SiC considered for the gas-cooled fast reactor systems. The experimental data from the literature on the uranium-silicon system are critically reviewed. Differential Thermal Analysis experiments are carried out to measure the temperatures of the phase transitions in the composition range 6-46% at Si. The experimental results are compared to the available data of the literature. The microstructure of the samples has been analysed using scanning electron microscopy. In view of the analyses, some solidification paths are proposed. Finally, the present experimental results and the available data of the literature have been used to perform a thermodynamic modelling of the uranium-silicon system using the CALPHAD method. 相似文献
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《Journal of Nuclear Materials》2006,348(1-2):40-44
The density of liquid alkali metals in the extended ranges of temperature and pressure has been calculated using a new equation of state (EoS). A wide comparison with experimental data was made. The results show that the equation of state reproduces the experimental PVT data of liquid alkali metals within experimental errors throughout the liquid phase. The thermodynamic properties such as isobaric expansion coefficient, isothermal compressibility, and internal pressure have been calculated for these liquids using this EoS and compared with the corresponding experimental results. The generally excellent agreement with experimental data indicates that this EoS can be used to calculate the thermodynamic properties of liquid alkali metals with a high degree of certainty. 相似文献
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S.R. Dharwadkar M.S. Chandrasekharaiah M.D. Karkhanavala 《Journal of Nuclear Materials》1978,71(2):268-276
A two-phase co-existence region has been established in the uranium-oxygen system in the composition range , employing micro-thertnogravimetric technique. The results obtained have been substantiated by high and ambient temperature X-ray diffraction and electrical conductivity measurements. 相似文献
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人发中微量元素与某些呼吸系统疾病关系的研究 总被引:1,自引:0,他引:1
用仪器中子活化法测定了正常人和慢性支气管炎,肺气肿,肺心病患者头发中Ca,Mg,Fe,Se,Cu,Zn等19种元素的含量。测得患者发中Ca,Mg含量低于正常人,Fe,As,Co等含量高于正常人;慢性支气管炎急发期患者发中Ca,Mg含量低于缓解期患者,Fe含量高于缓解期患者,均有显著性差异(P<0.05-0.01)。人发Ca与Mg呈高度正相关(P<0.001)。还测定了用于治疗慢性支气管炎的中药“咳 相似文献
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The reaction in the U---Cs---Mo---I---O system at 1073 K have been studied as a function of oxygen potential. The chemical constitution and the morphology of the phases formed were examined by electron-probe microanalyzer and X-ray diffractometer. The existence of a two-phase field UO2+x + Cs2UO4 was confirmed in the U---Cs---O system. The threshold oxygen potential was determined for the decomposition of CsI by UO2+x to form Cs2U4O12 and gaseous iodine. The effect of molybdenum on the UO2+x−CsI reaction was also investigated. Predominance of Cs2MoO4 over Cs2UO4 was verified in a certain range of oxygen potentials. Some assessments and interpertations of the experimental results were made with the aid of thermodynamic calculations. 相似文献
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The physical basis is presented of the model on which calculations of solid solution thermodynamic functions are based, and the relevant physical characteristics of γ-uranium-niobium solid solutions. The excess entropy and enthalpy of mixing at 1100 K are calculated for these alloys. Results are presented of an experimental study of the thermodynamic properties of U-Nb solid solutions in the temperature range from 1048 to 1173 K, by measuring EMF in a molten-salt electrolyte. For entropy of mixing the experimental data are closely consistent with the calculated curve, but there is no such agreement for the enthalpy of mixing. The reasons for this are considered. The possibility of the formation of an intermediate phase in the U-Nb system is briefly discussed. 相似文献