Phase relations in the quaternary Fe-Pu-U-Zr system

The phase diagram in the quaternary Fe-Pu-U-Zr system was established at 923 K in the uranium-rich region to understand better the compatibility between the metal fuel and stainless steel cladding in a fast reactor. The experimental phase relation data obtained in this study was applied to the thermodynamic methodology for construction of the phase diagram. The calculated phase diagram was consistent and well within the experimental data. The applicability of the thermodynamic model to other temperatures was confirmed by comparing the present results of differential thermal analysis with the calculated phase diagrams. These consistencies mean that both the thermodynamic model and the assessed parameters in the binary and ternary subsystems developed so far are reasonable. The calculated phase diagram established in this study was also in good agreement with the analysis of the diffusion zone in tests on Pu-U-Zr/Fe couples. This suggests that the diffusion zone formed at the fuel-cladding interface in the reactor system can be assessed using the phase diagram in the quaternary Fe-Pu-U-Zr system.     

Phase relations and crystal chemistry in the ternary PrO1.5-UO2-O2 system

Phase relations and defect structures were studied in a PrO_1.5-UO₂-O₂ ternary system in the temperature range from 1200 to 1500°C. Phases and compositions of the products heated in either air, helium or vacuum were examined by $\text{X-}\text{ray}$ diffraction and chemical analysis, respectively. The regions of existence of solid solution having fluorite type structure, of rhombohedral phase and of A-type rare earth sesquioxide phase were determined. It was found that these phase relations could be classified by the mean valency of uranium and the type of oxygen defects. The change of cubic lattice parameter of the solid solution, $\text{Pr}{}_{\mathrm{y}}\text{U}{}_{\mathrm{1?y}}\text{O}{}_{\mathrm{2+x}}$, in single phase region ($\text{0 ≤ y ≤ 0.7}$) was expressed as linear equations of $\text{x}$ and $\text{y}$: $\text{a = 5.4704?0.127x ?0.007y, for x ≥ 0}$ and $\text{a = 5.4704?0.397x?0.007y, for x < 0}$. The change of lattice parameters was discussed in some detail.     

Phase relations and thermodynamic properties of the uranium-nitrogen system

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.     

The ternary system: silicon-uranium-vanadium

Phase equilibria in the system Si-U-V were established at 1100 °C by optical microscopy, EMPA and X-ray diffraction. Two ternary compounds were observed, U₂V₃Si₄ and (U_1−xV_x)₅Si₃, for which the crystal structures were elucidated by X-ray powder data refinement and found to be isotypic with the monoclinic U₂Mo₃Si₄-type (space group P2₁/c; a = 0.6821(3), b = 0.6820(4), c = 0.6735(3) nm, β = 109.77(1)°) and the tetragonal W₅Si₃-type (space group I4/mcm, a = 1.06825(2), c = 0.52764(2) nm), respectively. (U_1−xV_x)₅Si₃ appears at 1100 °C without any significant homogeneity region at x ∼ 0.2 resulting in a formula U₄VSi₃ which corresponds to a fully ordered atom arrangement. DTA experiments clearly show decomposition of this phase above 1206 °C revealing a two-phase region U₃Si₂ + V₃Si. At 1100 °C U₄VSi₃ is in equilibrium with V₃Si, V₅Si₃, U₃Si₂ and U(V). At 800 °C U₄VSi₃ forms one vertex of the tie-triangle to U₃Si and V₃Si. Due to the rather high thermodynamic stability of V₃Si and the corresponding tie-lines V₃Si + liquid at 1100 °C and V₃Si + U(V) below 925 °C, no compatibility exists between U₃Si or U₃Si₂ and vanadium metal.     

Some equilibria in the uranium-plutonium-nitrogen ternary system. An assessment

Some assessments of possible equilibria for the ternary system uranium-plutonium-nitrogen have been made and from these equilibria the pressures of the gas phase species. Pu, U and N₂ for the system have been calculated. The nature of the vaporization behaviour of alloys of the system is also predicted.     

Phase diagram of the Nb-T system

The phase diagram of the niobium-tritium system was determined for the first time. Using X-ray diffraction and DTA techniques a shift of the monotectoid horizontal and of the boundary between the α' + β and α' phases to higher temperatures is observed for increasing hydrogen isotope mass. The monotectoid temperature is $\text{(103.9 + 1.0)°C}$ for T in Nb in comparison to $\text{(87.5 ± 1.0)°C}$ for H. In addition, a small decrease of the terminal solubility of the α phase at temperatures below the monotectoid horizontal was found with increasing isotope mass.     

Phase diagram of the zirconium-rhenium system

The phase diagram of the zirconium-rhenium system was constructed by x-ray and microscopic methods and by measurements of melting points, hardness and microhardness of the phases. The region of solid solutions of rhenium in α-zirconium at 800 ° C is ～0.5 weight %, and at the temperature of the eutectoid transition it increases to 2–3 weight %. At 1600 ° C, 14.68 weight % of rhenium dissolves in β-zirconium and at the eutectoid transition point at 550–600 ° C, 8 weight % of rhenium. The β-phase is stabilized in alloys containing more than 4 weight % of rhenium. An eutectic is formed at 1600 ° C and 25 weight % of rhenium. The presence of a metastable ω-phase in melts rich in zirconium was established. The solubility of zirconium in rhenium at 2500 ° C is less than 2 weight %. Three chemical compounds are formed in the system by peritectic reactions:

1. 1)
   At 2500 ° C, Zr₅Re₂₄ of the α-Mn type with a body-centered cubic lattice (a = 9.6–9.7 kX) and a microhardness of 1000 kg/ mm²;     
   
   

Computational study of atomic mobility for the bcc phase of the U-Pu-Zr ternary system

Experimental diffusion data in literature has been evaluated to assess the atomic mobility for the bcc phase in the U-Pu-Zr system by means of the DICTRA-type (Diffusion Controlled TRAnsformation) phenomenological treatment. The developed mobility database has been validated by comprehensive comparisons made between the experimental and calculated diffusion coefficients, as well as other interesting details resulting from interdiffusion, e.g. the concentration profile and the diffusion path of diffusion couples.     

Phase study in the Na-Sr-U-O system: Characterization of new phase

In continuation with the earlier work for phase studies of Rb-Sr-U-O and Cs-Sr-U-O systems, the subsolidus phase relations in Na-Sr-U-O quaternary system were determined at 850 °C in air atmosphere. A novel quaternary phase Na₈Sr₂U₆O₂₄ in the Na-Sr-U-O system was synthesized by heating the respective oxides at 850 °C in air. XRD data of Na₈Sr₂U₆O₂₄ was indexed on a cubic system with lattice parameter a = 0.8326 nm and was found isostructural with K₈Sr₂U₆O₂₄ and Rb₈Sr₂U₆O₂₄. A pseudo-ternary phase diagram of Na₂O-SrO-UO₃ was drawn using the new quaternary compound and various phase fields were established by X-ray powder diffraction analysis. The structure of Na₈Sr₂U₆O₂₄ was derived from the powder data and structural parameters were refined by the Rietveld profile method.     

Phase equilibria and crystal structures in the ternary systems: Actinoid metal-transition metal-boron III. Ternary transition metal diborides with plutonium

Ternary borides PuTB₄ and Pu₂TB₆ have been synthesized from the elements and their crystal structures have been characterized from X-ray powder diffraction data. Compounds PuTB₄ with T = Mo, W, Tc, Re crystallize in the orthorhombic YCrB₄-type, whereas PuRuB₄ and PuOsB₄ reveal a transposition behavior between the related structure types of YCrB₄ and ThMoB₄. Compounds Pu₂TB₆ with T = Tc, Re, Ru, and Os are isostructural with the structure type of Y₂ReB₆. The crystal chemistry of these phases is discussed with respect to the corresponding rare earth compounds.     

SSRF定时系统的温漂补偿系统设计

上海同步辐射装置(SSRF)的定时信号通过光纤由事件发生器EVG发送到事件接收器EVR,为各个分系统和设备提供精确时序信号,但光纤因SSRF复杂的局部环境而产生温度变化,从而引起EVR的输出信号与高频信号的相位漂移.因此需设计-套温漂补偿系统来补偿这种因光纤的温度变化而产生的相位漂移,本文详细阐述了温漂补偿系统的硬件架构及相位测量算法,最后给出了温漂补偿系统的测试结果.     

Phase diagram of the ZrO2–FeO system

The results on the ZrO₂–FeO system studies in a neutral atmosphere are presented. The refined eutectic point has been found to correspond to a ZrO₂ concentration of 10.3 ± 0.6 mol% at 1332 ± 5 °C. The ultimate solubility of iron oxide in zirconia has been determined in a broad temperature range, taking into account the ZrO₂ polymorphism. A phase diagram of the pseudobinary system in question has been constructed.     

Phase control system for SSRF linac

The design of phase control system in Shanghai Synchrotron Radiation Facility (SSRF) linac is presented in this paper. And digital phase detecting algorithm, the key for phase control system, is fully described. The testing results for phase control system in 100MeV linac are discussed in detail.     

Phase diagram investigations of K-Sr-U-O system

In continuation of our previous work on phase diagram investigations of alkali metal-alkaline earth metal-uranium oxides, the sub-solidus phase relations in K-Sr-U-O quaternary system were determined at 850 °C in air. A pseudo-ternary phase diagram of UO₃-SrO-K₂O was drawn using reported ternary compounds in K₂O-UO₃ and SrO-UO₃ systems, a single quaternary compound, K₈Sr₂U₆O₂₄ and various phase mixtures. These compounds and mixtures were synthesized by solid route, by heating K₂CO₃, SrCO₃ and UO₃ in different molar proportions at 850 °C. The phase fields of K₂O-SrO-UO₃ pseudo-ternary phase diagram were established by X-ray powder diffraction analysis. Gibbs energies of formation of binary and ternary uranates were estimated. The Gibbs energies of formations of A₈Sr₂U₆O₂₄ (A = Na/K/Rb/Cs) type compounds for different alkali metals were compared to find a reason for the stability of the compound for sodium, potassium and rubidium and its instability for cesium.