NaI闪烁探测器测量感生放射性及其蒙特卡罗模拟

描述了如何使用蒙特卡罗方法评估产生在加速器屏蔽混凝土中的感生放射性. 使用EGS4程序模拟了NaI闪烁探测器测量屏蔽混凝土块表面剂量率时, 对于半径和厚度的响应. 结果发现,在屏蔽混凝土块半径和厚度分别达到40cm和30cm时, 表面剂量率达到饱和. 研究了东京大学SF回旋加速器北墙位置8和位置9的表面剂量率, 并和使用NaI闪烁探测器的测量结果进行了对比, 发现模拟和实验结果符合很好. 并且, 获得了表面剂量和表面感生放射性之间的转换系数, 对于⁶⁰Co转换系数为0.90(Bq·g^－1)·(μSv·h^－1)^－1, 对于¹⁵²Eu转换系数为1.26(Bq·g^－1)·(μSv·h^－1)^－1. 这样, 就可以通过NaI闪烁探测器表面剂量的测量结果简单评估加速器设备屏蔽混凝土中的感生放射性.     

水流损失和热补偿共同作用对增强型地热系统(EGS)产能影响的研究

基于青海共和盆地-3705m地热田实测数据,结合流固耦合传热理论并运用Comsol软件,建立了离散型裂隙岩体流体传热模型。考虑水流损失和热补偿共同作用,模拟得到了开采过程中上、下岩层(盖层和垫层)为绝热不渗透、传热不渗透、渗透传热时,储层(上、下岩层和压裂层)温度场的变化特征,分析了产出流量、水流损失、产出温度、产热速率的变化规律。研究结果表明:采热过程中产出流量始终小于注入流量;产出流量增幅速率先增大后减小,最后趋于稳定,前3a产出流量增幅超过总增幅量的3/4;忽略水流损失,将高估产热速率,采热初期甚至达到考虑水流损失时产热速率的3倍以上;考虑水流损失,产热速率呈先快速上升再趋于稳定后逐渐下降的趋势,最优开采时间为3a^11a;研究上、下岩层对产出温度的影响,仅考虑传热,采热寿命延长5.43%,同时考虑渗流传热时,采热寿命延长2.71%;采热前9a,水流损失占主导作用,即流入上、下岩层水流损失对产热速率的影响高于热补偿效应,开采10a后,热补偿效应占主导作用;同时考虑水流损失和热补偿效应得到的产热速率变化规律与实际工程更为符合,建议选择低渗透能力的上、下岩层延长增强型地热系统(EGS)运行时间。     

热储周围岩石热补偿对增强型地热系统采热过程的影响

采用自行开发的增强型地热系统(EGS)地下热流动过程三维动态模拟软件,模拟不同地质条件下EGS的长期运行过程,分析热储周围岩体的热补偿对产热温度以及热储内岩石、流体温度演化的影响.该数值模型视热储为等效多孔介质,采用两个能量方程分别描述流体和岩石的温度场,深入探究岩石与循环流体之间的换热过程.研究发现,热储周围岩体的热补偿作用与热储内流场形态强烈相关,且并不总是提高EGS的生产温度.在深度方向上有较大的优势流动的热储中,热补偿作用在EGS运行早期甚至会降低采出流体的温度.随着EGS的运行,热储温度持续降低,热补偿将对热能开采的影响将逐渐转向正面,对生产流体温度的提高效果增强.     

Energetic distribution of the electrons from a 200 keV beam in polyurethane layers : EGS4 calculation and FTIR analysis

The aim of this study is to characterize the chemical transformation of a polymer resulting from irradiation by a 200 keV electron beam. Thermoplastic PU polyetherurethane material was used and irradiation was performed with applied electron fluences in the range of 10¹⁴–10¹⁷ electron cm⁻² at 77 K.

The chemical changes have been observed by FTIR analysis of irradiated layers. A NH bond evolution study has allowed us to follow polymer degradation versus depth and fluence. The results have been compared to a simulation of electronic energy loss and to the energy spectrum of the generated electrons in the polymer using EGS4 code.     

Experiment on Gamma Ray Generation by Laser Compton Scattering

A gamma ray generation facility was developed through laser Compton scattering on an electron beam storage ring, for the purpose of researching nuclear transmutation. Theoretical analysis on gamma ray yield and energy spectrum was performed, as well as EGS4 simulation code was employed to simulate the interaction of gamma ray and Ge detector. The acquired experimental results are in agreement with theory.     

增强型地热系统地下渗流场的模拟分析

采用自行开发的数值模型,模拟分析循环流体在双井增强型地热系统(EGS)地下热储中的渗流过程,系统分析不同水力渗透条件热储中流场形态的变化规律.结果表明,重力作用和流体动静压转换造成的"基础压差"与循环流体在地下裂隙岩体中的沿程阻力之间的相对大小是决定热储中流场分布形态的重要因素,而循环流量大小对热储内渗流场形态影响非常有限.基于此,我们提出水平井和多井环绕布局两种抑制流体短路的方案,为EGS的建设提供理论指导.     

Modelling and study of the Cherenkov effect

Studies at the Institute for Nuclear Research and Nuclear Energy particularly in regard to cosmic ray detection and construction of the Muonic Cherenkov telescope at the University of Blagoevgrad indicate a need for the development of a theoretical model based on observed phenomena and a refinement of this for detection system optimisation. This was introduced in the EGS4 code system. The first simulations consecrate on a number of different geometries of the water tank in total reflection. The model was compared with experimental data involving a ⁶⁰Co gamma source and the telescope.     

球形转子的精密恒速控制系统

讨论了静电支承球形转子的精密恒速控制系统，该系统主要基于旋转磁场加转和锁相控制。阐述了控制系统的组成，分析了鉴相器、PD控制、加转系统模型并加以线陛化，求出传递函数并分析特性，最后介绍了具体实验效果。     

A new configuration of the Moxon–Rae detector based on Si detector

A new Moxon–Rae detector configuration based on Si semiconductor detector was proposed in this paper. Three γ-ray sources, ¹³⁷Cs, ⁶⁰Co, and ²⁴Na, were employed to make actual measurements using the new Moxon–Rae detector. The measured pulse height spectra and detection efficiencies were compared with the EGS4 simulated values. The results revealed that the proposed new configuration is indeed a successful method and specially a useful technique for higher energy γ-ray measurement.     

低能宽幅电子束引出特性研究

研究了能量在100到300 keV区间的低能宽幅电子束从真空引出到空气中的特性。利用EGS5程序模拟了电子束穿过不同厚度钛箔后,在空气中距离钛箔5~10 cm距离处的能量损失、束流损失和束流分布均匀性等。模拟结果显示,对于低能电子,钛箔厚度应该在10 μm左右为宜,其透射率与能量直接相关,在距离钛箔5 cm的位置,电子束的分布不均匀度低于±2%,优于工业应用±10%的标准（特殊情况下要求为5%）,完全满足工业辐照要求。In order to investigate the characteristics of extracting low-energy electron beam from vacuum into air, EGS5 is used to simulate the energy loss, beam loss and spatial distribution uniformity at the irradiation position, which is 5~10 cm to titanium foil with different thickness. The simulation results show that the transmittance is directly related to the incent energy of low-energy electron. When the titanium foil thickness is 10 μm, the inhomogeneity about the energy beam spatial distribution is below 5% on the treatment plane 5 cm away from the titanium foil. And totally meet the industrial needs.