Zr-2/Cr扩散反应层物相分析

研究Zr-2/Cr扩散反应层物相，可为判断Zr-2和Cr是否相容提供依据。用热压法（50MPa)获得在1073K时Zr-2/Cr扩散反应层。分别用透射电镜（TEM）和场发射扫描电镜配备的薄窗能谱仪（EDS）对反应层进行结构的成分分析。结果表明，Zr-2/Cr扩散反应生成六方结构（C14型的）Zr(Fe,Cr)2Laves相。     

Zr-4合金α-Zr固溶体中Fe,Cr含量的研究

将电化学分离Zr-4合金中Zr(Fe,Cr)2第二相粒子的技术和原子吸收光谱分析技术相结合,建立了一种分析Zr-4合金α-zr固溶体中Fe和Cr含量的新方法,并用这种新方法分析了不同热处理状态下Zr-4合金α-zr固溶体中的Fe和Cr含量。分析结果表明,随着淬火温度的增加, α-zr固溶体中的Fe,Cr含量和Fe/Cr比值均增加,而Zr(Fe,Cr,)2第二相粒子中的Fe/Cr比值则相应降低,并且在淬火状态,α-zr固溶体中Fe,Cr的含量均大于其最大饱和固溶度。结合以前在高温水、蒸汽中的腐蚀试验结果发现,α-zr固溶体中的Fe,Cr含量对Zr-4合金的耐水侧腐蚀性能起着重要作用,并且,过饱和固溶在α-zr中的Fe,Cr含量存在一临界值,当Fe和Cr含量大于临界值时,Zr-4合金就具备抗疖状腐蚀的能力。     

Zr-4合金α-Zr固溶体中的Fe、Cr含量分析

将电化学分离Zr-4合金中Zr(Fe,Cr)2第二相粒子的技术和原子吸收光谱分析技术相结合，建立了一种分析Zr-4合金α-Zr固溶体中Fe,Cr含量的新方法，并用这种新方法分析了不同热处理状态下Zr-4合金α-Zr固溶体中的Fe,Cr含量。分析结果表明，随着淬火温度的增加。α-Zr固溶体中的Fe,Cr含量和Fe/Cr比值均增加，而Zr(Fe,Cr)2第二相粒子中的Fe/Cr比值则相应降低。结合以前的工作，可得结论：过饱和固溶在α-Zr固溶体中的Fe,Cr含量对Zr-4合金的耐水侧腐蚀性能有重要影响。     

U-Mo合金与Al扩散反应特征研究

采用扩散偶方法研究了U-Mo合金与Al扩散反应特征.扩散偶以热压方式实现持续贴合.实验在真空热压炉中完成,热压温度550-570℃,时间5～21 h.结果表明:U-Mo/Al扩散层界面形貌和成分与扩散层厚度有关;在扩散层界面处U、Mo和Al的含量突变;U-Mo侧扩散层产物主要为(U,Mo)Al3,Al侧产物为(U,Mo)Al4和UMo2Al20.U-Mo/Al扩散反应是Al越过U-Mo/Al原始界面向U-Mo侧扩散并发生固体反应和扩散层向Al层生长的过程.     

Be/00Cr17Ni14Mo2不锈钢扩散焊界面区成分的计算机模拟

为了优化扩散焊的工艺参数，应用有限元计算法建立的数学模型，对1050℃/65Mpa热等静压条件下不同时刻的Be/00Cr17Ni14Mo2不锈钢扩散焊的浓度场进行了计算机模拟，探讨了扩散宽度与扩散时间的关系。结果表明，模拟的浓度曲线与实验测定结果基本吻合，扩散宽度与扩散时间成抛物线关系。     

U-10Mo/Al-2Si扩散层性质研究

采用热压扩散偶方法研究了U-10Mo/Al-2Si的扩散层性质.实验在真空热压炉中完成,温度550～570℃.时间5～21 h.结果表明:扩散层随时间的延长和温度的提高而增厚;U-Mo侧生成了抑制U-Mo/Al的扩散反应,Si含量高达47.4%(原子分数)的富Si层.从U-Mo侧到Al-2Si侧,U和Mo的含量递减而A...     

5 Pu在模拟地下水中的扩散行为研究

以甘肃北山BS03井地下水为水相，研究Pu在Ca-膨润土中的吸附行为。研究结果表明：Ca-膨润土对Pu具有较强的吸附能力，吸附行为可用Freundlich吸附等温式描述；Pu在Ca-膨润土中的吸附为不可逆吸附；吸附平衡后，Pu在水相和固相中的价态主要为四价；随着溶液pH值和离子强度的升高，Pu的吸附能力增强；地下水中无机离子（包括阳离子、无机阴离子）浓度增大有利于Ca-膨润土对Pu的吸附；地下水中DOC的浓度增大不利于Pu的吸附。     

弥散型燃料中Zr与Gd_2O_3的相容性研究

采用包覆热轧法制备了Zr/Gd_2O_3扩散偶,分别在673K和1 073K温度下对Zr/Gd_2O_3扩散偶进行了不同时间的扩散热处理。采用金相显微镜(OM)初步观察Zr/Gd_2O_3界面特征,用场发射扫描电镜(SEM)进一步观察Zr/Gd_2O_3界面形貌,用能谱仪(EDS)分析Zr/Gd_2O_3界面附近元素分布情况,并从热力学角度分析了Zr与Gd_2O_3的相容性。结果表明:2种温度下Zr与Gd_2O_3的相容性很好。     

锆—2合金在500—800℃空气中氧化过程的研究

研究了Zr-2合金在500—800℃空气中氧化的规律,利用光学显微镜、透射电镜和扫描电镜对氧化膜形貌、组织和晶体结构进行观察,并对氧化膜内表面应力和应力梯度进行了估算。随着氧化膜增厚,氧化膜内表面应力最初增加而后下降,出现极大值;极大应力值和与其相对应的氧化膜厚度都随氧化温度升高而增加,应力梯度随氧化膜增厚呈单调下降。黑色氧化膜内存在三种晶体结构;单斜、四方、立方,最初晶粒细小,模糊不清,随着氧化时间增长,发生回复再结晶后,晶粒衬度才逐渐变得清晰。白色氧化膜为单一的单斜结构。     

Thermal Diffusion of Hydrogen in Zircaloy-2 Containing Hydrogen beyond Terminal Solid Solubility

The thermal diffusion of hydrogen is one of causes of uneven hydride precipitation in zircaloy fuel cladding tubes that are used in water reactors. In the diffusion model of hydrogen in zircaloy, the effects of the hydride on the diffusibility of hydrogen has been regarded as negligibly small in comparison with that of hydrogen dissolved in the matrix. Contrary to the indications given by this model, phenomena are often encountered that cannot be explained unless hydride platelets have considerable ostensible diffusibility in zircaloy.

In order to determine quantitatively the diffusion characteristics of hydrogen in zircaloy, a thermal diffusion experiment was performed with zircaloy-2 fuel cladding tubes containing hydrogen beyond the terminal solid solubility. In this experiment, a temperature difference of 20°–30°C was applied between the inside and outside surfaces of the specimen in a thermal simulator.

To explain the experimental results, a modified diffusion model is presented, in which the effects of stress are introduced into Markowitz's model with the diffusion of hydrogen in the hydride taken into account. The diffusion equation derived from this model can be written in a form that ostensibly represents direct diffusion of hydride in zircaloy. The apparent diffusion characteristics of the hydride at around 300°C are D_p = 2.3×10⁵exp(?32,000/RT), (where R: gas constant, T: temperature) and the apparent heat of transport Q _p *=?60,000 cal/mol. The modified diffusion model well explains the experimental results in such respects as reaches a steady state after several hours.     

U-Mo合金与Zr-4合金的扩散层性质研究

本文对U-Mo合金与Zr-4合金的扩散层性质进行了研究。三明治结构的U-Mo/Zr-4扩散偶在760~800℃下包覆热轧后,保温10~66 h。采用扫描电子显微镜(SEM)分析了扩散层的形貌和厚度,采用波谱仪(WDS)分析了各元素在扩散区内的分布情况,采用X射线衍射仪(XRD)测定了扩散层的相组成。分析结果表明,即使在800℃的高温下,U-Mo/Zr-4的扩散程度依然微弱,表现出良好的相容性;U-Mo/Zr的扩散层中间出现裂纹,裂纹两侧的扩散层相组成明显不同,靠近U-Mo侧为富Mo相,其主要是以化合物ZrMo_2为基的固溶体;靠近Zr-4侧的为富Zr相,其主要是以化合物UZr_2为基的固溶体;裂纹认为是由U和Zr不等量的原子交换所造成的。     

Effects of UO2/Zircaloy-4 Mole Ratios on Reaction of UO2 Fuel with Molten Zircaloy-4

Dissolution of UO₂ crucibles by molten Zircaloy-4 (Zry) was investigated in the temperature range of 2,223-2,373 K and for specimens having UO₂/Zry mole ratios between 7 and 18.2. The uranium concentration in the Zry melt rapidly increased during initial reaction time and approached saturated values, depending on reaction temperature and UO₂/Zry mole ratio. Kinetics of uranium concentration increase in the melt was analyzed based on a natural convection mass transfer model that takes into account the change of contact surface area/melt volume ratio with reaction time. The saturated uranium concentration in the Zry melt was inversely proportional to the U0₂/Zry mole ratio. An empirical correlation of saturated uranium concentration in the Zry melt was obtained as a function of UO₂/Zry mole ratios and reaction temperature. This study of the empirical correlation was intended to estimate maximum UO₂ fuel dissolution by molten Zry cladding during severe fuel damage accidents for three different reactor type fuels.     

UO_2-Zr弥散燃料板氧化扩散机理研究

UO2-Zr弥散燃料板的氧化过程包括包壳与冷却剂的氧化反应和芯体中弥散的UO2燃料微球氧原子扩散过程。本文通过直接求解球坐标系下的氧化扩散方程,得到UO2燃料微球高温下向芯体中氧原子扩散强度的解析式,该式与实验数据符合良好,并结合锆水反应与UO2燃料微球高温氧原子扩散效应构建了UO2-Zr板的氧化扩散模型。新模型能预测不同的氧化结构、芯体中更高的氧原子浓度以及相对较低的氧化吸氧量,为UO2-Zr板严重事故早期行为的研究提供了理论基础。     

Determination of Cell Averaged Diffusion Constants Based on Transport/Diffusion Perturbation Theory

A unified definition for cell-averaged diffusion constants has been established on the basis of transport and/or diffusion perturbatlon theories. The diffusion constants are derived by equating each component of reactivities obtained by transport theory for a heterogeneous cell to a corresponding component of reactivities by diffusion theory for a homogenized cell. The derived diffusion constants are applied to infinite uniform lattices and heterogeneous lattices composed of different cells. In infinite lattices the present diffusion constants are compared to the conventional flux-weighted cross sections and Benoist's anisotropic diffusion coefficients. In heterogeneous lattices they are compared with Rowlands-Eaton cross sections and the extended Benoist's diffusion coefficient. The present formula is applied to a heterogeneous slab lattice. It reveals that the present method gives a more accurate result for k _eff compared to the case with the conventional diffusion coefficient defined by D= 1/3Σ_tr or the extended Benoist's diffusion coefficient together with the conventional flux-weighted cross sections.     

不同温度下Al-Si共晶合金与Zr-2合金的相容性研究

用粉末冶金工艺制备了Al-Si共晶合金与Zr-2合金扩散偶,研究了不同等温热处理温度和时间条件下扩散偶的相容性.采用扫描电镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)技术分析了扩散偶界面处的微观形貌和元素分布,讨论了扩散层形成机理.结果表明,环境温度及材料状态显著影响扩散偶之间的相容性.650℃时,液态Al-Si合金对Zr-2合金的浸润和扩散形成了较明显的以Zr3Al化合物为主的扩散层;560℃时,扩散元素之间仅产生固态扩散,形成的扩散层很薄;350℃时,扩散系数更小,几乎未发生扩散和形成扩散层,Al-Si共晶合金与Zr-2合金之间具有良好的相容性.     

Thermal Diffusion Factor for Diatomic Gas Mixture in Multicomponent System

Thermal diffusion factor for diatomic gas mixture was expressed in a practical form applicable to multi- component mixture. Thermal diffusion factor for diatomic gas mixtures was obtained directly from thermal diffusion coefficient in multicomponent mixture by using the relation between thermal diffusion coefficient and thermal diffusion factor, and was shown to be the same as that derived by Mason et al. through a “generalized Stefan-Maxwell equation”. The present expression gives a theoretical proof of the previously reported rough estimate of thermal diffusion factor for hydrogen binary mixtures. Comparing with the present expression for H2-HT binary gas mixture, we have found that the previously reported expression for thermal diffusion factor overestimates in a temperature range from 50 to 1,200 K, but the difference between the previous and the present expressions is small. The present expression is essential to the separative analyses of thermal diffusion column for diatomic gas mixture in multicomponent system, and is consistent with the rough estimate for binary mixture of diatomic gases.