含硼矿物及环氧树脂复合材料的中子屏蔽性能

以我国特有的含硼原矿经选矿和高炉分离后分别得到的含硼铁精矿粉和富硼渣为研究对象,用蒙特卡罗方法研究了二者及其环氧树脂复合材料的中子屏蔽性能,讨论了影响材料屏蔽性能的因素,确定了含硼矿物/环氧树脂复合材料合适的配比范围;得到了材料的快中子分出截面和热中子衰减系数,并与常用的混凝土屏蔽材料进行对比。结果表明：复合材料对14.1MeV快中子的屏蔽性能主要与屏蔽材料中低原子序数元素的含量有关,含硼矿物复合材料对热中子的屏蔽性能与硼元素的浓度有关,伴生γ射线光子的衰减主要与矿物材料中高原子序数元素的含量和材料的密度有关。含硼矿物复合材料中含硼矿物的最优体积比为0.4~0.6;最佳配比对14.1MeV快中子的屏蔽性能与混凝土的接近,对热中子的屏蔽性能强于混凝土的,有望作为辐射场周围混凝土屏蔽层的裂缝灌注及不规则孔洞的填补或直接制备复合屏蔽材料。     

基于蒙特卡罗方法的复合材料辐射屏蔽设计北大核心CSCD

在乏燃料后处理厂的工作环境中可能存在着低能中子-γ射线混合辐射,严重威胁工作人员的人身安全。本文针对上述混合辐射环境,利用蒙特卡罗程序Geant4模拟计算了一种钨/硼纤维增强含硼/铋聚合物复合材料中不同材料参数对低能中子和γ射线综合防护效果的影响。结果显示,此种钨/硼纤维复合材料对低能中子和γ射线均具有良好的屏蔽效果。文章证实了纤维垂直排布方式具有比平行排布方式更优的屏蔽效果,且垂直排布方式下透过粒子束的强度分布更加均匀。此外,在聚合物基体中掺杂一定质量分数的硼/铋可以进一步增强复合材料的辐射屏蔽效果。依据这些结果我们认为此种复合材料可以为后处理厂等辐射环境中的防护服及相关防护用具提供参考。     

硼酸盐晶须增强聚乙烯复合材料及其热中子屏蔽性能研究

以硼酸镁(Mg2B2O5)和硼酸铝(Al4B2O9)晶须作为中子吸收体与高密度聚乙烯(HDPE)复合,制备了硼酸盐晶须/HDPE复合材料。讨论了影响材料力学性能及屏蔽性能的因素,并与常用的碳化硼(B4C)屏蔽材料进行了对比。实验结果表明:3种复合材料对热中子的屏蔽效果为B4CMg2B2O5Al4B2O9,复合材料对热中子的屏蔽率均随吸收体含量和材料厚度的增加而增大,当硼酸镁晶须/HDPE复合材料的厚度为15.76mm时,材料对热中子的屏蔽率可达86.58%。晶须/HDPE复合材料的拉伸强度随晶须含量的增加而增大,当硼酸镁晶须的含量为9.1%时,复合材料的拉伸强度可达24.39 MPa,和碳化硼/HDPE复合材料相比,硼酸盐晶须更能增强HDPE基屏蔽材料的力学性能。     

新型耐高温中子屏蔽复合材料的设计制备及性能研究

采用表面改性处理技术,制备了由环氧树脂、B₄C（或BN）和聚丙烯酸铅组成的新型耐高温中子屏蔽复合材料,重点研究了材料制备工艺及主要性能指标,利用蒙特卡罗程序MCNP对材料中子屏蔽性能进行了模拟计算,并与文献报道的屏蔽材料铅硼聚乙烯进行了比较。结果显示,由环氧树脂、B₄C和聚丙烯酸铅组成的复合材料各项力学性能良好,具有良好的耐高温性能,210 ℃烘烤7 h外观无明显变化。MCNP模拟计算表明,对于从热中子至10 MeV的中子,4 cm厚新材料的中子剂量穿透率和中子注量穿透率均优于文献报道的同等厚度的铅硼聚乙烯材料。Am-Be中子源屏蔽试验的实测数据和模拟计算数据表明,两者随屏蔽材料厚度的变化趋势几乎完全一致,两者的差异随屏蔽材料厚度的增加逐渐减小,在10.5 cm处仅1.34%。     

高能射线及其屏蔽材料

综述了日常放射性工作中常遇到的几种电离射线,如X射线、γ射线、中子及其他带电粒子的产生机理及其特点,指出了防护这些射线的最有效和最实用的办法是选用适当的屏蔽材料,并详述了这些屏蔽材料的种类和相关的屏蔽原理,提出了屏蔽材料发展方向是研究添加稀土合金的复合材料,并努力提高这些稀土元素在复合材料中所发挥的作用来提高其屏蔽效果.     

屏蔽材料组分含量的优化设计

防辐射材料的屏蔽性能跟材料的组成成分含量是有关的,成分含量不同,屏蔽效果也不同。利用遗传算法,对衰减公式进行优化计算,得出各组分含量的最佳配比。用MCNP程序对几种组分配比的材料进行X射线屏蔽模拟,结果表明利用遗传算法计算出来的配比材料屏蔽效果最好。     

聚丙烯酸钐/环氧树脂辐射防护材料的制备工艺及性能

通过辐照接枝聚合的方法制备聚丙烯酸钐/环氧树脂辐射防护材料和聚丙烯酸钐/丙烯酸铅/环氧树脂辐射防护材料,研究不同剂量γ射线照射下样品的性能差异和不同金属浓度样品的性能差异,并比较钐元素和铅元素对光子的屏蔽能力。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、能量色散型X射线能谱(EDAX)等方法研究了材料的微观结构;对材料的力学性能进行了测试和分析;用多道γ谱仪和GammaVision软件测试并分析了材料的辐射防护性能。结果表明：复合材料较纯环氧树脂力学性能得到了改善;材料制备过程中γ射线的照射剂量控制在50kGy左右为宜;稀土元素钐防护低能射线的能力强于传统的屏蔽元素Pb。     

新型柔性中子屏蔽复合材料研制及性能研究

为满足形状复杂核设备外围防护以及辐射防护服对于柔性中子屏蔽材料的需求,研制了一种新型B4C/SEBS中子屏蔽复合材料,重点研究了不同B4C含量对SEBS基复合材料力学性能、热学性能及中子屏蔽性能的影响。实验结果表明:复合材料拉伸强度、扯断伸长率均随着B4C含量的增加而减小;增加B4C含量,复合材料撕裂强度呈现出先增大后减小的趋势,而复合材料邵氏硬度则不断增大;该材料热导率随着B4C含量的增加而不断升高;利用镅-铍中子源进行材料中子屏蔽测试,同厚度材料中子屏蔽性能随着B4C含量的增加而不断提高。综合考虑该新型柔性中子屏蔽材料良好的中子屏蔽性能、抗撕裂性能及柔韧性能等特性,其在形状复杂核设备外围防护及辐射防护服领域具有较大的应用前景。     

新型纤维增强环氧树脂基复合材料研制及其中子屏蔽性能研究

核技术应用产业的迅速发展,对中子辐射屏蔽材料的种类、服役环境、结构性能提出更多、更高要求。针对发展功能/结构一体化中子屏蔽材料需求,研制了一种新型玻璃纤维/B₄C/环氧树脂复合材料。力学测试与中子屏蔽实验发现,该复合材料中子屏蔽性能良好,5 cm厚样品屏蔽后中子透射率仅19.6%;材料具有较高强度与模量,性能优于铅硼聚乙烯。增大材料B₄C含量对提升材料中子屏蔽性能作用显著,但同时材料强度、模量有一定减小。综合考虑该材料的中子屏蔽性能、承受载荷以及耐高温特性,其在反应堆、加速器及中子源等核设施外围防护材料,尤其是乏燃料贮存格架材料用途上具有较大应用潜力。     

6MeV探伤加速器屏蔽体设计

正探伤用电子直线加速器主要产生电离辐射,其中对X射线的防护是重点。根据射线不同,屏蔽材料的选择有所区别。对于X射线,已知高能光子流与物质作用主要产生光电效应、康普顿散射和游离电子对等3种效应。光电效应产生概率与屏蔽材料原子序数4次方呈反比;康普顿散射     

M-C simulation of shielding effects of PE, LiH and graphite fibers under 1 MeV electrons and 20 MeV protons

Shield/rig effects of different materials under 1 MeV electron and 20 MeV proton beams were simulated with Geant4 code. It was found that shielding effects of polyethylene and graphite fibers are much better than aluminum. Energy depositions in the phantom shielded by the materials are calculated, with the least energy deposition by graphite fiber shielding. The results show that graphite fibers are good radiation shielding material in space programs. Key words Monte Carlo method, Radiation shield, Shielding materials     

遥控机器人的耐辐射设计和测试

本文介绍了一种可在强辐射环境中进行辐射探测的遥控机器人的耐辐射设计和测试结果。在分析金属、有机材料、光学材料和电子器件等机器人组件的辐射损伤的基础上,利用小规模集成芯片构建控制电路以及核心电路局部屏蔽的设计思路,提高了机器人的耐辐射性能。在钴源辐射设施中开展的耐辐射性能测试结果表明:该遥控机器人至少能够在100 Gy/h的强辐射场中正常工作;粗略估计,机器人可承受的累积剂量预期可达3 000 Gy。     

Simulations of mass attenuation coefficients for shielding materials using the MCNP-X code

In this paper,mass attenuation coefficients of concrete,bricks and cement plaster,as shielding materials,are calculated at 59.5,356,662,1173,1274 and 1333 keV by using the MCNP-X (version 2.4.0) code.The numerical simulation results are compared with previous Monte Carlo studies,experimental results and XCOM data.The effects of barite on mass attenuation coefficients are investigated.The mass attenuation coefficients increase with the barite content.Thus,our results agree well with experimental studies on gamma ray shielding of barite.It is flexible for the MN method to change the barite rates in material by small increments,which is experimentally difficult.Also,modeled geometry can be used for future approaches such as new designs and new structures especially in investigating new barite-containing materials to build nuclear reactors or high-energy radiation therapy facilities.     

Results of an integration study of a diagnostics port plug in ITER

Diagnostics in ITER are mandatory to characterize the parameters of plasma and study its interactions with plasma-facing components. Diagnostics components in the vicinity of the plasma are supported by metallic structures called port plugs. At the tokamak mid-plane, these components are installed in port plugs through intermediate structures called drawers. Apart from hosting the diagnostics, the port plugs act as shielding against neutrons and gammas, in order to limit the nuclear loads in crucial components (such as diagnostics and superconducting coils) as well as the dose levels in the controlled zones of the tokamak. The radiation shielding function of the port plugs is ensured through an optimized mixture of heavy metallic materials and water, forming shielding blocks surrounding the diagnostics and called Diagnostic Shield Modules (DSMs). These DSMs constitute the rear part of the drawers (the front part being composed of the Diagnostic First Wall). This paper presents the main results of a study performed in Europe on the integration of a particular diagnostics port plug, the Equatorial Port Plug 1 (EPP1). The paper first provides the results of the EPP1 diagnostics integration analysis. In a second step it focuses on the design of the EPP1 DSMs and summarizes the major results of a thorough set of analyses aiming at studying the DSMs behaviour under different loads, suggesting recommendations to improve their current design.     

基于蒙特卡罗方法的环氧树脂基屏蔽腻子优化设计及应用研究

本文针对船用核反应堆辐射场特点、屏蔽防护需求和使用环境条件,开展了屏蔽腻子的优化设计及应用研究。选用耐腐蚀防霉变优异、粘结度强、无毒性的双酚A环氧树脂和脂环胺固化剂作为基体材料,添加粒径约100μm的铅、聚乙烯、碳化硼等屏蔽添加剂提高屏蔽腻子的辐射防护性能。采用蒙特卡罗方法对屏蔽腻子的主要成分配比进行了优化设计。计算结果表明,碳化硼含量为5%~15%、铅含量为80%时,中子的慢化与吸收达到平衡,较高的铅含量大幅增强了其对γ射线及次级γ射线的屏蔽防护能力,使屏蔽腻子对235 U诱发裂变源的综合辐射防护能力达到最佳水平。消泡剂、分散剂、流平剂、促进剂等加工助剂的添加对屏蔽腻子快速固化、气泡排除、混合均匀、成型致密光滑起到了重要促进作用。通过样品试制和试验测试,证明了优化设计的屏蔽腻子具有优异的屏蔽性能、耐辐照老化性能、固化成型质量、粘结强度、混合浇灌施工便捷性能等,能有效满足船用核反应堆等设施屏蔽缝隙处及不规则部位的辐射防护使用需求。     

中国先进研究堆水平孔道屏蔽设计优化研究

考虑辐射安全和经济性,对中国先进研究堆(CARR)的水平烫源孔道作了屏蔽设计优化研究.通过分步计算,克服了MCNP4C在计算粒子深穿透问题中的耗时、结果差的缺陷.再建立模型,将转门的屏蔽设计优化问题转化为屏蔽材料的组合优化问题.使用特征统计算法(CSA)结合ANISN程序,编写屏蔽设计优化程序.经过大量方案的筛选,很快找到了符合辐射安全、经济性和材料的机械特性的屏蔽设计优化方案optCH2;用MCNP4C程序计算了优化的方案,并与原方案做了比较.结果表明,optCH2方案的安全性能和经济性都比原方案提高很多.     

Calculation of radiation fields in VVER shielding using approximations supporting local balance of materials mass and fission-source neutrons

The possibility of using approximations of geometry, which support the balance of materials mass on each spatial cell of a grid covering the computational region, to calculate radiation fields in VVER shielding by introducing additional mixtures of materials for cells where several initial materials are present is analyzed. The methods of combinatorial geometry, which are implemented in the MCU computer program for solving transfer equations by the Monte Carlo method, are used to specify the 3-D geometry of the shielding and a fuel-element and (or) fuel assembly fission source and the method of ray tracing is used to convert the combinatorial specification into a grid specification. A numerical experiment in which the VVER-1500 radiation shielding is calculated showed that the conservation of the materials mass/number of source neutrons in the grid cells during the conversion ensures rapid convergence of the results when the density of the spatial grid increases. Good agreement is attained between MCU Monte Carlo and KATRIN S_n calculations of VVER-1000 shielding. __________ Translated from Atomnaya énergiya, Vol. 104, No. 6, pp. 328–333, June, 2008.     

基于SuperMC的船用反应堆辐射屏蔽结构优化研究

船用反应堆辐射屏蔽结构的重量严重影响着船舶的机动性,如何在现有屏蔽空间内进行屏蔽设计以减少屏蔽体的重量,对船舶机动性能提高有着重要意义。本文基于中子输运设计与安全评价软件系统SuperMC中的智能核设计模块对固定屏蔽空间的屏蔽优化问题开展了研究,采用“萨瓦娜”号反应堆模型进行了屏蔽优化计算。结果表明,优化方案相比于原始设计方案屏蔽体重量大幅度减小,该方法为指导船用反应堆辐射屏蔽的材料选择与屏蔽体布局提供了新的技术手段。      

TOPAZ-Ⅱ空间核反应堆电源辐射屏蔽优化措施影响分析

空间核反应堆辐射屏蔽可减弱中子与γ光子通量对仪器设备的辐照,温度是影响辐射屏蔽性能的重要因素。利用Fluent软件对TOPAZ-Ⅱ空间核反应堆电源辐射屏蔽在真空环境下的换热行为进行了数值模拟,提出了优化措施,并揭示了优化措施对其温度场的影响和其温度分布特性。研究结果表明：冷却剂管道及其管槽表面喷涂低发射率的涂层具有均匀辐射屏蔽温度场和降低其温度峰值的效果,最优化参数为管道表面涂层的发射率为0.1～0.3、管槽表面涂层的发射率为0.1,且管道表面喷涂低发射率涂层效果要优于管槽;在冷却剂管道、管槽间添加单层表面发射率为0.04～0.07的真空遮热板也可使辐射屏蔽温度场与温度峰值处于最优状态。     

Effect of mix parameters and hydrogen loading on neutron radiation shielding characteristics of latex modified concrete mixes

With the tremendous surge in the usage of radioactive materials in industry, education and research, medicine and other fields, it becomes a concern to protect the working personnel and common people around, from hazardous radiation leakages that may seriously affect their health. Among the different types of radiation, gamma and neutron radiations require adequate shielding. There have been several attempts to develop newer concretes and evaluate their neutron radiation shielding characteristics. In the present study, an attempt has been made to study the effect of varying the mix parameters and hence the resulting total hydrogen content on the neutron radiation shielding characteristics of Latex Modified Concrete (LMC) mixes. The experiments are planned in such a way that the hydrogen content of the mixes is varied by controlling the mix parameters i.e., cement content, water/cement ratio and polymer/cement ratio of LMC mixes. The results are statistically analyzed. It is found that definite improvements could be achieved in neutron radiation shielding characteristics of LMC mixes as compared to ordinary concrete, with the increase in hydrogen concentration effected by changes in mix parameters.