钨玻璃与铅玻璃对X射线辐射屏蔽效果的数值计算分析

通过 WINXCOM理论计算X射线能量在20~100 keV下,钨和铅硅酸盐玻璃的质量衰减系数、有效原子序数和半值层。结果发现,随着 WO3和PbO 含量的增加质量衰减系数增加。钨玻璃在70 keV能量下,由于光电效应发生突变,质量衰减系数突然增强。随后,利用 MCNP 5计算5种能量下钨玻璃的积累因子,以便进一步修正模拟结果以达到真实情况。     

钨玻璃与铅玻璃对X射线辐射屏蔽效果的数值计算分析

通过WINXCOM理论计算X射线能量在20~100keV下,钨和铅硅酸盐玻璃的质量衰减系数、有效原子序数和半值层。结果发现,随着WO_3和PbO含量的增加质量衰减系数增加。钨玻璃在70 keV能量下,由于光电效应发生突变,质量衰减系数突然增强。随后,利用MCNP 5计算5种能量下钨玻璃的积累因子,以便进一步修正模拟结果以达到真实情况。     

含硼矿物及环氧树脂的光子质量衰减系数

以我国辽宁东部地区特有的含硼矿物、含硼废弃物和环氧树脂为对象,理论计算了原矿、含硼铁精矿粉、富硼渣、普通硼泥和环氧树脂等5种材料对1keV～100GeV能量范围的光子质量衰减系数,为放射性同位素源、反应堆和粒子加速器外围建筑材料的屏蔽设计提供依据。结果表明：含硼矿物的添加显著改变了基体环氧树脂对光子的质量衰减系数,矿物在1keV～0.1MeV以光电效应为主的能量范围内对光子的质量衰减系数变化较大,所含元素的K层特征吸收限使得矿物对光子的质量衰减系数突变增加;在0.1～10MeV以康普顿效应为主的能量范围内矿物对光子的质量衰减系数缓慢变化,其中环氧树脂的质量衰减系数较矿物的稍高;在以共轭电子对效应为主的10MeV～100GeV光子能量范围内矿物对光子的质量衰减系数先减少后增加,含硼铁精矿粉是该能量范围内最佳的光子吸收体。     

用109Cd γ射线衰减法测量管道原油密度和含水率的蒙特卡罗模拟

通过蒙特卡罗模拟计算了109Cd放射源发出的两种能量的γ射线穿透含水原油后的穿透率.依据对88keV γ射线,原油、水和甲烷的质量衰减系数大致相同的特点,测定了平均密度.依据对22.2keV γ射线,原油和水的质量衰减系数有较大差异而原油和甲烷的质量衰减系数大致相同的特点,测定了含水率.计算结果验证了此方法的可行性.     

MC法模拟重金属氧化物玻璃屏蔽性能

论文旨在验证采用MCNP软件获得的模拟实验结果真实性。利用MCNP粒子输运模拟软件计算不同重金属氧化物玻璃以及铅在不同能量γ射线下的质量衰减系数,平均自由程,使用XCOM程序预测计算γ射线能量在0.001~100 000 Me V的质量衰减系数以及平均自由程,通过将两种MC法模拟软件获得的计算结果与实验值对比,证明了采用MC法进行模拟计算的可靠性。研究结果表明,基于MC法的MCNP程序可用于计算重金属氧化物玻璃的屏蔽性能。     

MC模拟计算混凝土的γ射线衰减参数

利用MC模拟计算了不同混凝土的γ射线衰减参数,并与文献中XCOM计算的数值对比,结果符合性较好。基于此模型,结合复合材料的均匀填充模型,研究了50%含量不同粒径的WO₃对混凝土材料在663 keV能量下的衰减系数。结果表明,WO₃颗粒越均匀细小,衰减系数越大,粒径100 nm比1 mm的WO₃对复合材料的质量衰减系数提高了8.94%。     

MC模拟叠层复合材料对γ射线的屏蔽效果

运用MCNP5和WINXCOM程序模拟了不同叠加顺序金属Ta和La复合材料对不同能量γ射线屏蔽性能的影响,比较和分析了两种模拟程序下复合材料质量衰减系数差异的原因。结果表明:Ta+La型结构的复合材料屏蔽效果优于La+Ta型,两者屏蔽性能差距随复合材料厚度的增大而增大,随γ射线能量增加而减小。质量衰减系数模拟结果差异主要与模型中光电效应与康普顿效应的占比有关。     

MC法模拟与实验验证高气压电离室能量响应

使用MCNP5对两个高气压电离室进行MC模拟,并完成实验测量,分别得到两个电离室的两种能量响应结果。将模拟结果与实验结果对比发现,两种结果在低能量段差异较大,两个电离室都在48 keV处相对偏差最大;在高能量段差异较小,1号电离室在1 250 keV处相对偏差最大,2号电离室在662 keV处相对偏差最大;两种结果在164～1 250 keV能量段的能量响应整体范围相近。最后分析发现在低能量段差异较大的主要原因是电离室的制造误差和模拟计算能量沉积时产生的计算误差。     

不锈钢和钨材料对东方超环(EAST)装置硬X射线诊断系统的影响

计算了不锈钢、铅和钨材料对不同能量硬X射线的衰减规律,根据计算结果设计了东方超环(EAST)超导托卡马克硬X射线诊断系统探测器的屏蔽准直体;详细介绍了EAST上硬X射线诊断系统,利用22Na放射源对诊断系统进行了台面实验测试,通过放射源的γ射线能谱研究了不锈钢和钨材料对γ射线的衰减规律,拟合计算了衰减系数;同时将实验结...     

用双能X射线测量双组分物质的质量厚度

通过加吸收片的方法,获得样品在给定高压下的X射线等效能量,可用来测量该样品的质量厚度.本文讨论了测量双组分样品质量厚度的方法,发现在实验的双组分样品厚度范围内,用单组分样品的等效质量衰减系数代替双组分样品中该组分的质量衰减系数来计算双组分样品的质量厚度,具备可行性,测量结果的误差在5%以内.测量实物鱼体,求解出鱼体的软组织和骨组织的质量厚度,进一步证明在双组分样片厚度不大的情况下,这种测量方法的现实可行性.     

离子注入玻璃

离子注入和离子束分析技术在半导体和金属改性中已获得广泛应用,近年来又开始应用于绝缘体。在1981年第一届绝缘体辐照效应国际会议(REI-81)上,美国Sandia实验室Arnold和意大利Chinellato等发表离子注入玻璃效应的初步研究。Mazzoldi曾应用核反应分析对玻璃辐照效应进行了详细研究。 带电粒子辐照玻璃引起网状损伤并改变了表面化学成分。钠玻璃经离子注入后产生钠离子迁移,Na迁移有两种不同机构,在低质量离子辐照时以电子阻止本领为主,此时钠受到和     

Binary potassium-silicate glass irradiated with electrons

Binary potassium-silicate glass of composition 15 mol% K₂O + 85 mol% SiO₂ was irradiated with 2.5 MeV. The thickness of glass was chosen so as electrons stopped near the back surface. After the high-energy irradiation both, back and top surfaces, were depleted from potassium; the back surface was depleted more than the top one. The decay curves were recorded on pristine glass, and on top and back surfaces of the glass pre-irradiated with high-energy electrons. The incubation times of the top surface increased while the incubation time of the back one decreased in comparison with the pristine glass. Observation of the volume changes induced by the following impaction of 50 keV revealed the top surface is closer to the pristine glass than the back one.     

Nuclear waste glass interfaces after one year burial in STRIPA part 1: Glass/glass

Two simulated nuclear waste glasses were corroded in an in-situ experiment in the STRIPA mine up to one year at 90°C. Changes in compositional in-depth profiles for glass/glass interfaces were measured using SIMS. Both glasses showed a depletion of Na, Cs, and B, but for the more corrosion resistant glass, the lower depletion depth is ascribed to the formation of a thin (2.0 m) coherent and dense outer layer, enriched in Mg, Ca, Sr, Ba, Zn-Al, Fe, and Si, which impedes both the ion exchange and network attack of the bulk glass underneath.     

典型贵金属元素在玻璃固化体中的溶解度及其对玻璃性质的影响

本文主要针对高放废液中贵金属(PGMs)的含量、存在形态,玻璃固化体中PGMs的溶解度、存在形态、颗粒大小等化学行为进行归纳,同时针对玻璃固化过程中PGMs对玻璃性质(流变、粘度、热导、电阻)的影响进行总结。该文为研究典型贵金属元素在玻璃中的溶解度及其变化规律、典型贵金属元素在玻璃中的化学行为及沉淀机理以及典型贵金属元素对玻璃性质的影响研究提供调研基础,可为我国玻璃固化技术的研发提供前期的理论依据。     

Imaging dynamics of charge-auto-organisation in glass capillaries

Multiply charged ion beam transmission through insulating capillaries is today a very active field of research. Thanks to the work of several groups during the last five years, several features of this unexpected process have been evidenced. The open challenge is to understand and control the self-organized charging-up of the capillary walls, which leads finally to the ion transmission. Up to now, the specific charge distribution on the inner surface, as well as the dynamics of the build-up, are still to be understood. While capillaries usually studied are microscopic pore networks etched in different materials, our concern is in macroscopic single capillaries made of glass. With a length of several centimeters and a diameter of a few micrometers at the exit, these capillaries have nevertheless the same aspect ratio as the etched pores (length/diameter ≈ 100). One of the leading goals of this research on single capillaries is to produce multi-charged ion beams with diameters smaller than a micrometer (nano-beams). These glass capillaries offer the opportunity to be used as an ion funnel due to their amazing properties of guiding and focusing highly charged ion beams without altering neither their initial charge state nor the beam emittance (<10⁻³ π mm mrad). However, the understanding of the underlying process is not complete and relies on models assuming charge patches distributed along the capillary and which still need to be tested. We present the first observation imaging the dynamics of the charging-up process in single glass capillaries. During the build-up of the self-organized charge deposition on the capillary walls, the 230 keV Xe²³⁺ transmitted beam is deflected back and forth several times as the outgoing current increases. This is in agreement with the picture of charge patches created sequentially along the capillary and thus deflecting the beam until a stationary state is reached.     

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.     

High temperature silver ion implantation into glass

Soda-lime-silicate glass has been implanted with 55 keV Ag⁺ ions at five different temperatures: room temperature, 100, 225, 350 and 600°C. Rutherford backscattering spectroscopy was used to provide depth profiles for the implants. All samples show a low retention of silver and this varies with temperature. In the room temperature and 100°C implants the silver diffuses to, and is lost from the surface. This also occurs in the higher temperature implants, but in these cases there is a significant amount of inward diffusion by the silver. This diffusion extends to at least 500 nm: greatly in excess of the predicted range for a standard implant. Optical measurements on the samples show that those with the inward diffusion have formed an enhanced-index waveguide.