Ti—Mo合金氘化物热解吸过程研究

采用非零初压热解吸法研究了不同钼含量的钛钼合金TiMo_x(x=0.03、0.13、0.25、0.50、1.00,Mo与Ti原子数之比)氘化物的热解吸动力学,测试了氘解吸量与解吸时间的关系,应用反应速率分析方法得到了其热解吸速率常数k_d和热解吸表观活化能E_d;并与氕化物的热解吸动力学行为进行了比较。结果显示,x=0.03时,合金氕化物E_d小于氘合金化物E_d,与钛放氢动力学同位素效应一致;x=0.13、0.25时,氕化物E_d大于氘化物E_d;x=0.50、1.00时,氕化物与氘化物的E_d差别不大。通过初始解吸时合金中氕、氘含量的比较,结合室温下合金吸氕、氘量及物相结构,对合金放氢动力学同位素效应的本质进行了探讨。     

Ti-V合金吸氢性能研究

介绍了Ti0.75V0.24和Ti0.51V0.49两种合金及其氢化物的结构确定方法。研究了它们的吸氢性能,测得了吸氢的P-C-T曲线。该曲线分成两个主要区段：当H原子数与Ti—V原子数之和的比值小于1．0时,为氢气的固溶区,并近似遵从Sievert(希乌尔)定律;当该比值大于1．0后,有的曲线出现吸氢坪台区。分别计算了在固溶区和坪台区吸氢的热力学参数。     

Ti-Mo合金氢化物放氢动力学同位素效应研究

在高真空金属系统中,采用非零初压热解析方法研究了钛钼合金TiMox（x=0.03, 0.13, 0.25, 0.50, 1.00, 原子比）氘化物的热解析动力学,测试了氘解析量c随时间t的变化关系,应用反应速率分析方法得到了热解析速率常数kd和热解析表观活化能Ed ,合金氘化物Ed依次为46.6, 22.4, 13.7, 17.1, 10.4kJ.mol-1。比较氕化物的热解析动力学行为,Mo含量小于0.03时,合金氕化物Ed小于氘合金化物Ed,与钛放氢动力学同位素效应保持一致。Mo含量在0.13 ~ 0.25时,氕化物Ed大于氘化物Ed,Mo含量大于0.50时,氕,氘化物Ed 差别不大。通过初始解析时合金中氕,氘含量的比较,结合室温下合金吸氕,氘量,对合金放氢动力学同位素效应的本质进行了探讨。     

Ti-Mo合金吸氢动力学的同位素效应

为寻找一种价格低廉、分离性能优良的氢同位素分离材料来替代金属Pd,对Ti-Mo合金的氢同位素效应进行研究。采用磁悬浮熔炼方法制备5种不同组成的TiMox（x=0.03、0.13、0.25、0.50、1.00,Mo/Ti原子比）固溶体合金,用定容变压法测试了250～650℃范围内的吸氘动力学性能。结合前期吸氕动力学的研究结果可知,在250～650℃范围内,合金的平衡吸氕量略大于合金的平衡吸氘量。Mo含量小于1.00,在低温（250～450℃）下,合金的吸氘表观活化能均为负值。高温（450～650℃）下,合金的吸氘表观活化能大于吸氕表观活化能,与钛吸氢同位素动力学效应保持一致。     

Ti-Mo合金的吸放氢动力学

采用磁悬浮熔炼法制备了5种不同组成的TiMo_x（x=0.03, 0.12, 0.25, 0.50, 1.00,原子比）固溶体合金,用定容变压法测试了其在不同温度范围内的吸放氢动力学性能。研究结果表明,合金的吸放氢动力学可以按一级反应来描述,决速步骤为氢原子在合金晶格中的扩散。相同温度下,不同组成样品的吸氢容量随Mo含量的增加而降低。合金的吸氢活性随Mo含量增加先增强后减弱,氢化物的稳定性随Mo含量的增加而降低。     

Ti-Mo互扩散界面吸氢同位素效应的离子束分析研究

为探究Ti-Mo互扩散对金属吸氢的影响,本文采用离子束分析方法对Ti-Mo薄膜的膜-基互扩散界面的吸氢同位素（H和D）效应进行了研究。通过氩离子刻蚀减薄的方法有效降低了表面碳、氧杂质对样品吸氢的影响。吸氢结果表明,对于表面洁净的样品,氢化后固相中氢或氘的浓度均沿着深度随钼原子含量的增加而减小。在单一气体吸氢实验中,氢原子浓度减小的趋势较氘原子缓慢;而在氢氘混合气体吸氢实验中,当容器中的氢氘压强比p(H2)∶p(D2)≥05∶1时,固体中氘氢浓度之比随钼浓度的增加而降低,但当p(H2)∶p(D2)<05∶1时,氘氢浓度之比随钼浓度的增加而升高。因此,由于Ti Mo界面的互扩散,吸氢出现了显著的氢同位素效应,钼的存在不利于体系对氢同位素气体的吸收。     

1992～2005年秦山核电基地外围环境放射性监测

自1992年,浙江省辐射环境监测站对秦山核电基地外围环境辐射水平进行了连续的监督性监测。1992～2005年,秦山核电基地外围环境电离辐射水平和各种介质放射性水平的监测结果如下：在正常运行下,秦山核电基地外围环境7辐射剂量率平均为96nGy／h;大气气溶胶总α、总β比活度分别为0．11、0．45mBq/m^3;环境大气中^3H浓度为71．6mBq/m^3,^14CO2浓度为0．30Bq／g（碳）;沉降物总β比活度为0．81Bq／m^2d;陆地环境淡水（饮用水、湖塘水、井水）中总α、总β、^90Sr、^137Cs浓度分别为65、151、4．4、0．3mBq／L,^3H为1．0Bq／L,雨水^3H浓度为2．8Bq／L;正常排放下基地附近海域海水样品^90Sr、^137Cs平均浓度分别为5．4、0．7mBq／L,^3H为1．0Bq／L;土壤、湖塘泥、潮间带土、海底泥^137Cs平均比活度分别为3．3、1．9、2．4、1．1Bq/kg（干重）;食用植物样品中,大米^90Sr、^137Cs、^3H平均比活度分别为0．06、0．14、0．4Bq／kg,青菜为0．27、0．04、3．1Bq／kg（鲜重）,萝卜为0．10、0．03、2．5Bq／kg（鲜重）;指示植物样品中,茶叶^90Sr、^137Cs、^3H平均比活度分别为3．4、0．49Bq／kg（干重）和4．6Bq／kg（鲜重）,松针分别为9．8、0．10、7．7Bq／kg（鲜重）;肉类动物样品中,猪肉^90Sr、^137Cs平均比活度分别为0．06、0．08Bq／kg（鲜重）,羊肉为0．11、0．03Bq／kg（鲜重）,牛奶为0．03、0．02Bq／k（鲜重）,奶粉^137Cs平均比活度为0．18Bq／kg（干重）,鲻鱼^90Sr、^137Cs平均比活度分别为0．13、0．05Bq／kg（鲜重）。     

机械合金化Fe100—xCux体系的XAFS研究

本利用XAFS方法研究机械合金化方法制备的Fe100-xCux(x=0,10,20,40,60,70,80,100,x为原子百分比）合金中Fe、Cu原子的局域环境结构随组成的变化。对于Fe100-xCux二元混合物,当x≥40时,Fe原子的近邻配位结构从bcc转变为fcc,但Cu原子的近邻结构保持其fcc不变;与之相反,当x≤20时,Fe原子的近邻配位保持bcc结构而Cu原子的近邻配位结构从fcc转变为bcc结构。XAFS结果还表明fcc结构的Fe100-xCux中Fe的无序因子σ（0．009A）比bcc结构的Fe100-xCux中的σ（0．081A）大得多;并且在同一机械合金化Fe100-xCux（x≥40）样品中Fe原子的σ（0．099A）比Cu原子的σ（0．089A）大。这表明机械合金化的Fe100-xCux样品中Fe和Cu原子可以有相同的局域结构环境但不是均匀的过饱和固溶体,而是fcc或bcc合金相同时存在Fe富集区和Cu富集区。     

U-Mo合金γ相稳定性研究

研究了U-Mo、U-Mo-X（X＝Ti、V、Si）合金及U-Mo/Al、U-Mo-X/Al扩散偶界面层的γ相稳定性,探讨了合金元素和退火工艺对γ相稳定性的影响。结果表明：Mo含量越高,U-Mo合金的γ相稳定性就越高;U-6.5Mo-0.5Si合金的γ相稳定性较高,是因为U Si混合焓较低,但加入Si易导致形成USi_x脆性相;而U-6.5Mo-0.5Ti和U-6.5Mo-0.5V合金的γ相稳定性较差,是因为Mo在Ti、V体系内具有较低的混合焓,易形成固溶体或金属间化合物,导致γ相贫Mo;随着退火温度从500℃升高至600℃,γ相发生共析分解,扩散层的γ相数量减少,α相增多,α相成为Al的快速扩散通道,促使形成UAl₄、UMo₂Al₂₀和U₆Mo₄Al₄₃等富Al相。     

钛膜中氢同位素的深度分布

为评估氢同位素效应对其在贮氢金属中深度分布的影响,对H/D-Ti、D/T-Ti、D-Ti及T-Ti样品用7.4MeV的4He离子束进行30°方向弹性反冲(ERD)分析.由H/D-Ti样品ERD能谱获得其1.7μm深度的D分布,结合D-Ti样品ERD能谱的～3 μm深度的H、D分布进行了模拟分析.结果表明,H、D含量均随深度增加,其分布曲线基本一致,说明在Ti中H、D的分布互不干涉,样品制备过程中其同位素效应不明显.用同样的方法对DT-Ti样品中的D、T分布进行了模拟分析.结果表明,在1.7 μm深度内D、T的分布基本均匀,但由于D、T的能谱过于靠近,其解谱误差较大.用3.0 MeV的质子对HD-Ti和D-Ti进行的质子背散射(PBS)分析表明,两样品中的D分布趋势一致,证明了Ti中H、D的分布互不干涉,样品制备过程其同位素效应不明显的结论.     

The nucleation of hydrides in a Zr-2.5 wt% Nb alloy

The precipitation of hydride plates in a Zr-2.5 wt% Nb alloy is shown to be sensitive to the prior heat treatment of the alloy. For heat treatments that lead to a faceted α/β two phase microstructure, the α-β interface is characterized by an epitaxial dislocation array and steps with associated strain fields. For this structure, the nucleation of hydrides is controlled by the defect structure of the interface. On annealing the α-β structures below the monotectoid temperature, the retained β phase is unstable, decomposing first to $\text{β}{}_{\mathrm{r}}$ and ω and ultimately to α and $\text{β}{}_{\mathrm{Nb}}$. At the intermediate stage, i.e. with a β_r/ω two phase structure, hydride precipitation takes the form of stacks of small hydride plates confined to channels in the β lattice between the ω particles. For both microstructural conditions, the preferred site for hydride nucleation appears to be that which can most effectively accommodate the strains associated with hydride precipitation. Similarities in the precipitation behaviour in α-β Zr alloys and Ti alloys are discussed.     

Identification and quantification of hydride phases in Zircaloy-4 cladding using synchrotron X-ray diffraction

Zirconium hydrides precipitate in fuel cladding alloys as a result of hydrogen uptake from the high-temperature corrosion environment of light water reactors. Synchrotron X-ray diffraction was performed at room temperature on stress-relieved Zircaloy-4 cladding with two distributions of hydrides - (1) uniformly distributed hydrides across the entire cladding wall and (2) hydride rim next to the outer surface. The δ-hydride phase was found to be the predominant hydride phase to precipitate for hydrogen contents up to 1250 weight parts per million (wt ppm). At a higher content, about 3000 wt ppm, although δ-hydride is still the majority phase, a significant amount of γ-hydride is also observed. At even higher hydrogen contents, in excess of approximately 6000 wt ppm, such as can occur in a highly dense hydride layer, peaks associated with the ε-hydride phase are also observed in the diffraction pattern. The volume fraction of hydrides was estimated as a function of hydrogen content using the integrated intensities of select diffraction peaks corresponding to the α-Zr matrix and the hydride phases. These estimated values agree well with calculated values from the independently measured concentrations. The results of this study indicate that hydride precipitation in Zircaloy-4 is a complex process of evolving hydride phases with increasing local hydrogen content.     

Effect of radial hydrides on the axial and hoop mechanical properties of Zircaloy-4 cladding

The effect of radial hydrides on the mechanical properties of stress-relief annealed Zircaloy-4 cladding was studied. Specimens were firstly hydrided to different target hydrogen levels between 100 and 600 wt ppm and then thermally cycled in an autoclave under a constant hoop stress to form radial hydrides by a hydride reorientation process. The effect of radial hydrides on the axial properties of the cladding was insignificant. On the other hand, the cladding ductility measurements decreased as its radial hydride content increased when the specimen was tested in plane strain tension. A reference hydrogen concentration for radial hydrides in the cladding was defined for assessing the fuel cladding integrity based on a criterion of the tensile strength 600 MPa. The reference hydrogen concentration increased with the specimen (bulk) hydrogen concentration to a maximum of ∼90 wt ppm at the bulk concentration ∼300 wt ppm H and then decreased towards higher concentrations.     

Corrosion resistance of Mo–Fe–Ti alloy for overpack in simulating underground environment

In order to examine the application of Mo–Fe–Ti alloy for overpak, the corrosion resistance of heat-treated its alloys was investigated by electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM). The sample subjected to solution heat treatment (ST) had a single β phase and samples subjected to aging heat treatment at 600–700 °C had α phase precipitation in β phase. EIS results showed that the corrosion resistance of the aging heat-treated samples was lower than that of the ST sample, but much higher than that of pure Ti in 10% NaCl solution of pH 0.5 at 97 °C which simulating the crevice solution. Laser micrographs of the aging heat-treated samples indicated that α phase was caused selective dissolution in test solution. The TEM combined with EDAX (energy dispersive X-ray) analyses showed that β phase matrix composed of 2.7 wt.% Mo and 4.8 wt.% Fe, and α phase composed of 0.7 wt.% Mo and 0.1 wt.% Fe in sample aged at 600 °C. Thus, Mo-poor α phase was selectively dissolved in a test solution. In EIS, the ST sample of only β phase showed the highest resistance, and aging heat-treated samples containing α phase (0.7 wt.% Mo) showed higher values than pure Ti in the corrosion test. As Fe was involved in β phase with Mo which increased remarkably the corrosion resistance, the addition of Fe did not decrease the corrosion resistance of aging heat-treated Mo–Fe–Ti alloy in simulating underground environment.