全体积R7T7玻璃固化体裂隙研究

在高放废物玻璃固化体工业生产过程中，玻璃熔融后浇注到标准容器中暂存。在熔融玻璃冷却的过程中由于玻璃体热量散失不均匀导致裂隙产生。另一方面，玻璃体在水环境中发生水相腐蚀，玻璃体同水相接触的表面积是影响玻璃体腐蚀的主要因素之一。产生裂隙的玻璃体表面积的变化对于计算玻璃腐蚀量，了解玻璃腐蚀程度具有重要意义。     

模拟高放玻璃体在高温湿气中的蚀变行为

模拟地下水穿透地质处置多重屏障情形下，地下水会以高温蒸气的形式与高放玻璃体发生反应，加速玻璃体的蚀变。采用纯水和特定的盐溶液作为浸泡剂以控制体系的相对湿度分别在100%和90%左右。模拟高放玻璃体样片用聚四氟乙烯线悬挂在浸泡剂上方并在低氧箱中平衡，分别在120 ℃和150 ℃的干燥箱内反应。通过测试浸泡液中各元素的浓度和分析玻璃体表面的腐蚀产物，以表征玻璃的蚀变速率。实验发现，温度对玻璃腐蚀的影响最为明显，湿度的影响较弱。玻璃体中大多数元素在150 ℃下的浸出速率高于120 ℃下的浸出速率2～3个数量级。90 d时，玻璃体在150 ℃下已观察到显著的腐蚀。900 d后，150 ℃下玻璃体已基本完全腐蚀；而在120 ℃下的玻璃腐蚀程度很小，900 d时腐蚀厚度仍小于50 μm。150 ℃时随着腐蚀的发生，玻璃表面的SiO2腐蚀层逐渐形成以钙的硅酸盐为主的二次矿相。     

模拟高放玻璃体在高温湿气中的蚀变行为

模拟地下水穿透地质处置多重屏障情形下，地下水会以高温蒸气的形式与高放玻璃体发生反应，加速玻璃体的蚀变。采用纯水和特定的盐溶液作为浸泡剂以控制体系的相对湿度分别在100%和90%左右。模拟高放玻璃体样片用聚四氟乙烯线悬挂在浸泡剂上方并在低氧箱中平衡，分别在120 ℃和150 ℃的干燥箱内反应。通过测试浸泡液中各元素的浓度和分析玻璃体表面的腐蚀产物，以表征玻璃的蚀变速率。实验发现，温度对玻璃腐蚀的影响最为明显，湿度的影响较弱。玻璃体中大多数元素在150 ℃下的浸出速率高于120 ℃下的浸出速率2～3个数量级。90 d时，玻璃体在150 ℃下已观察到显著的腐蚀。900 d后，150 ℃下玻璃体已基本完全腐蚀；而在120 ℃下的玻璃腐蚀程度很小，900 d时腐蚀厚度仍小于50 μm。150 ℃时随着腐蚀的发生，玻璃表面的SiO2腐蚀层逐渐形成以钙的硅酸盐为主的二次矿相。     

熔岩玻璃体核素90Sr和239Pu释放量的计算

基于全等、均匀体分布的玻璃小球模型,推导了熔岩玻璃体中核素溶解释放率的数学计算公式,参考利佛莫尔实验室测量的玻璃溶解速度估算花岗岩介质熔岩玻璃体在25℃条件下的溶解速度下限为5.04×10-7g/(m2.d),上限为1.42×10-4g/(m2.d)。计算了核素90Sr和239Pu的溶解释放率和释放份额,结果表明:熔岩玻璃体在高温阶段的核素释放率比环境温度时高出4～5个数量级,大部分核素释放量发生在这个阶段。核素90Sr的释放份额介于0.3%～65%之间,核素239Pu的释放份额介于0.5%～82%之间。温度、玻璃溶解速度和反应性比表面积是影响核素释放的关键因素。     

大气气溶胶中7Be的粒径分布

利用5级大流量串级撞击器采集大气气溶胶样品,高纯锗γ谱仪系统测量放射性,分析了大气气溶胶中放射性核素⁷Be的浓度及粒径分布规律。在样品采集期间,环境大气中⁷Be浓度平均值为7.29 mBq/m³,且在春季出现较大的浓度。研究发现,在粒径＞3.0 μm的气溶胶样品中,基本测量不到⁷Be;在粒径＞0.95 μm的气溶胶样品中,⁷Be仅占总量的10%左右;⁷Be主要分布在粒径＜0.95 μm的气溶胶粒子上。     

青铜文物的腐蚀研究--高放废物处置系统的人为类似物研究实例

研究了在湖北、江西、广西、陕西和北京收集到的青铜文物样品的化学成分、结构特征和样品所在地区的环境条件.研究结果表明青铜文物随着时间不断腐蚀,其腐蚀层至少由两层组成,即氧化物和碳酸盐层组成,个别样品出现主要由物理作用产生的疏松亚层,有些样品还有SnO2亚层.腐蚀层厚度因样品所处的环境条件不同而变化,干旱和潮湿地区样品腐蚀层厚度分别为50～260μm和300～800μm.就青铜抗自然腐蚀而论,其腐蚀产物如孔雀石、锡石等都是稳定的矿物,可保护内部的金属在地下埋藏环境中不被继续腐蚀,青铜是适用于作高放废物地质处置系统中废物罐的材料.     

高压钠灯玻璃焊料耐腐蚀性能研究

本文叙述了普通高压钠灯用玻璃焊料,在800℃温度下钠汞蒸气中的抗钠腐蚀性能。给出了Al_2O_3-CaO-BaO-MgO—Y_2O_3系在120h后钠腐蚀渗透层厚度为25～35μm;1000h后为80～90μm。按照d=At~(1/2)公式推算该玻璃焊料经10000h后钠腐蚀渗透层的厚度也仅约为300μm左右。     

高压钠灯玻璃焊料耐腐蚀性能研究

本文叙述了普通高压钠灯用玻璃焊料,在800℃温度下钠汞蒸气中的抗钠腐蚀性能。给出了Al_2O_3-CaO-BaO-MgO-Y_2O_3系在120h后钠腐蚀渗透层厚度为25～35μm;1000h后为80～90μm。按照d=At~(1/2)公式推算该玻璃焊料经10000h后钠腐蚀渗透层的厚度也仅约为 300μm左右。     

气溶胶样品氢含量的质子弹性散射分析

利用单个标准样品比较法质子弹性散射分析（PESA）对一组采集在核孔膜上的气溶胶样品的氢含量进行定量分析。在质子束能量为2.5MeV、散射角为40°时，PESA测量10μm厚核孔膜上气溶胶中H含量的探测限为0.36μg/cm²。几个样品H含量的测量结果在3.2~37.5μg/cm²之间，显著高于探测限。质子能量在1.0~2.5MeV范围内，3.5μmMylar膜的束流归一化H峰面积随入射质子能量的变化在±3%以内。所以，不同厚度的气溶胶样品可采用同一个标准样品来进行PESA测量。     

反向气相色谱技术对模拟高放玻璃的比表面积研究

准确测定高放玻璃的比表面积对评估高放玻璃的腐蚀速度和核素的释放速率极为重要。本研究首次将反向气相色谱技术用于模拟高放玻璃腐蚀过程的比表面积研究。研究结果表明,玻璃比表面积随时间的变化曲线分为线性快速增加阶段、中间过渡阶段、缓慢增加平台阶段,玻璃腐蚀后最终的比表面积取决于玻璃与地下水的相对量的比例,浸泡的地下水相对量增加,则最终腐蚀后的玻璃的比表面积相应增加,玻璃/地下水体表比(S/V)为1500、3000、6000m-1时对应的最终比表面积分别是未浸泡玻璃比表面积的100、50、10倍,玻璃腐蚀后表面呈非均匀形貌。首次用壬烷在玻璃腐蚀表面的非可逆吸附量定量评估了其表面的非均匀性,150和90℃下玻璃浸泡后微观非均匀形貌的比例达到20%～40%。     

A 25-year laboratory experiment on French SON68 nuclear glass leached in a granitic environment - First investigations

We have investigated a 25.75-year old leaching experiment to improve our understanding of the mechanisms controlling glass dissolution in geological disposal conditions. A SON68 glass block was leached in slowly renewed synthetic groundwater (at 90 °C, 100 bar) in contact with some pieces of granite and Ni-Cr-Mo alloy as environmental storage materials. One hundred and sixty-three samplings were carried out over the entire duration of the experiment and were used to calculate the mean thickness of the altered glass (28 (±9) μm) and the glass dissolution rate. After few months, the rate remained very constant at 6 × 10⁻³ g m⁻² d⁻¹ which is about 20 times higher than the residual rate measured in a batch reactor at the same temperature.At the end of the experiment, mainly SEM analyses were performed on the entire glass block. Surprisingly, the glass alteration layer has neither a homogeneous thickness, nor a homogeneous morphology. The location of the sampling valve (at half height of the glass block) seems to divide the glass block into two parts. In the upper half (above the sampling valve), the general morphology of the alteration layer consists in a relatively simple and uniform gel and some secondary phases which are rare-earth phosphates. The mean measured thickness of this alteration layer is 6.7 (±0.3) μm. However, in the lower half of the glass block, the gel is globally larger and frequently contains rounded shapes which are rare-earth phosphates. This section is edged by secondary phases bearing Mg, Na, Zn and Ni. The mean measured thickness is 81.3 (±1.1) μm in the lower half. In this experiment, the flow rate which leads to the hydrodynamic transport of the soluble species must be a key factor for the local glass alteration process. We have also shown that this unexpected behavior is likely due to heterogeneities of the chemistry of the solution. This conclusion is supported by the behavior of Mg. This element, supplied by the inlet solution, precipitates with Si and forms clay minerals and therefore weakens the passivating properties of the gel. Mg-rich clay minerals are only observed in the lower half of the glass block. Further investigations are necessary to better understand the coupling between the hydrodynamics and chemistry in this experiment. However, based on this study, we can conclude that glass in disposal should be very sensitive to the water renewal near the glass surface.     

离子辐照导致硼硅酸盐玻璃浸出性能的变化北大核心CSCD

在高放射性废物深地质处置过程中,放射性核素衰变引起的强辐射场会导致玻璃固化体浸出性能的变化。本工作利用15 MeV Si离子辐照模拟深地质处置强辐射场,采用MCC-1静态浸泡法在pH=9.0的KOH溶液中对硼硅酸盐玻璃分别浸泡1、3、7、14、28 d,结合电感耦合等离子体发射光谱仪、拉曼光谱仪以及扫描电镜研究了辐照前后玻璃样品的浸出行为。结果表明:随着浸出时间推移,玻璃表面会不断地腐蚀脱落;辐照后玻璃样品的浸出率明显高于未辐照玻璃样品的,蚀变层结构与元素组成无明显差异,但厚度明显增大;形成的蚀变层中Na元素和B元素基本耗尽;蚀变层中SiO_(2)网络体结构溶解,生成大量的Si—OH键及硼硅酸盐结构,并出现四配位B单元向三配位B单元的转变。     

Study of gel development during SON68 glass alteration using atomic force microscopy. Comparison with two simplified glasses

Literature mentions several physicochemical studies concerning the characterisation of the alteration films that are formed during the dissolution of the nuclear glasses. Up to now, however, no study had been undertaken on the evolution of the alteration film thickness by in situ technique. This study proposes to carry out atomic force microscopy (AFM) in liquid and dry conditions in order to measure the shrinkage or swelling of the alteration film. This work is performed on the glass SON68 and on two glasses with simplified compositions. The results obtained reveal a shrinkage of the alteration film for the simplified glasses and, in situ (underwater), a slight swelling for the SON68 glass caused by the formation of crystalline phase (phyllosilicates) on the surface. In all three cases, when alteration progresses, it increases the density of the gel and the volume occupied by the alteration products tends to be equal to the volume initially occupied by the glass (called isovolumetric alteration). Finally, the drying leads to an important shrinkage. These results could be used to evaluate the potential impact of the internal cracks of an industrial glass block.     

Morphological evolution of alteration layers formed during nuclear glass alteration: new evidence of a gel as a diffusive barrier

This paper presents X-ray reflectometry and nitrogen adsorption results on alteration films formed at the surface of the French high level radioactive waste reference glass: SON68 glass (R7T7-type). For the first time, in situ (underwater) X-ray reflectometry has been used to investigate the alteration of this nuclear glass. A morphological evolution of alteration films is proposed and related to different steps of alteration kinetics. Initially a de-alkalinized glass layer is obtained, followed by the formation of a gel having an open porosity. Subsequently the gel densifies as the glass alteration rate decreases and finally the pore size increases upon formation of a dense and thin zone within the film. The latter dense zone within the gel could constitute a diffusive barrier. This hypothesis is also discussed for simplified glass gels.     

Nature and role of natural alteration gels formed on the surface of ancient volcanic glasses (Natural analogs of waste containment glasses)

This paper provides an overview of the geochemical alteration of basaltic glass, considered for over 20 years as a suitable natural analogue for nuclear borosilicate glasses. The available data show that natural basaltic glasses may survive for million of years under subsurface conditions. Mineralogical studies show that an alteration layer called palagonite forms on the surface of the basaltic in response to the chemical attack by water. Under some environmental conditions, the alteration layer consists of an amorphous gel-like material, leading many authors to suspect hydration of the glass by water permeation and alkali interdiffusion. In other cases, the alteration layer is crystallized to some extent and contains clay minerals (smectite). Such layers are formed mainly on the younger natural glass samples (<1 My) by a process of coprecipitation of the elements dissolved from the glass. On samples older than 1 My, the alteration layers also contain zeolites. In the presence of these hydrated aluminosilicates, a hydrated residual glass is systematically observed, which thus forms as a consequence of interdiffusion processes. Leach tests conducted under controlled laboratory conditions at temperatures up to 200 °C on both natural glass samples and synthetic basaltic glass provide identical kinetic results and alteration mechanisms. When compared with the data for SON68 nuclear borosilicate glass, the initial dissolution rates show the same activation energy (about 72 kJ mol⁻¹) and consequently similar dissolution mechanisms. Moreover, when altered under static conditions at high reaction progress, both basaltic glass and nuclear glass have similar behavior characterized by a significant drop in the dissolution rate, up to three to five orders of magnitude lower than the initial dissolution rate. The time-dependence of the thickness of the altered layers measured on natural glass samples confirms this kinetic trend over time: the long-term dissolution rate is very low. This decrease may be related to diffusion mechanisms involving key chemical species and controlled by the mineralogy of the palagonite layer.     

多台阶光栅结构的溶胶凝胶法制备工艺

采用溶胶凝胶法制备一种具有光敏性的ZrO₂薄膜,通过紫外分光光度计对薄膜曝光前后的结构变化进行分析。结果表明,该薄膜具有良好的光敏性。采用紫外曝光结合图形转移工艺,制备了具有多台阶结构的复杂微细图形。测量结果表明,该结构为周期性三台阶结构,周期为210μm,每个台阶的高度约为325nm。     

地下水穿透情形下玻璃固化体的蚀变研究

玻璃固化体在高放废物处置库中的长期处置行为,是处置库安全评价的关键环节之一。本研究模拟极端情形下,地下水穿透包装容器与固化体接触后,固化体中元素的浸出和蚀变行为。结果表明,地下水与固化体接触后,各元素的浸出浓度迅速增大,在200 d后逐渐下降并趋于稳定;温度对固化体中不同元素浸出速率的影响不同,B和Si的浸出速率随温度的增加而增大,U和Re的浸出速率随温度的降低而增大;固化体蚀变程度随温度的升高而加重,但其蚀变层的形成会阻滞元素在其中的扩散,客观上降低了固化体蚀变速率;富Si处置环境有利于抑制固化体中元素的浸出。     

Borosilicate glass alteration driven by magnesium carbonates

The alteration of simplified synthetic glass, representative of the French reference nuclear glass R7T7, in presence of hydromagnesite has been experimentally investigated and modeled. Magnesium in solution is known to potentially enhance glass alteration; nuclear glass clayed host rocks contain magnesium and can dissolve to maintain the concentration of magnesium in solution. For modeling purposes, it was suitable to study a simple system. Hydromagnesite was therefore chosen as a simple model mineral in order to check the influence of an Mg-rich mineral on glass alteration. Since the models use thermodynamic and kinetic parameters measured in pure water and pH-buffered solutions, changing the solution composition or adding minerals is a key step towards the validation of the modeling assumptions before using the model for predictive purposes.Experiments revealed that glass alteration is enhanced in presence of hydromagnesite. Modeling was performed using the GRAAL model implemented within the CHESS/HYTEC reactive transport code. Modeling proved useful both for explaining the mechanisms involved and quantifying the impact on glass alteration: Mg coming from hydromagnesite dissolution reacts with Si provided by the glass in order to form magnesium silicates. This reaction decreases the pH down to neutral conditions where magnesium silicates are more soluble than at the natural alkali pH imposed by glass or hydromagnesite dissolution. The driving force of the magnesium silicate precipitation is eventually the interdiffusion of alkali within the altered amorphous glass layer as this mechanism consumes protons. The model’s ability to describe the concentrations of elements in solution and formed solids whatever the glass/hydromagnesite ratio strongly supports the basic modeling hypothesis.