14MeV中子吸收剂量测量

本文叙述了用双探测器技术测定(n,r)混合场中子和光子剂量分量的方法。在窄束~(60)Coγ辐射场中对电离室进行了γ刻度并给出结果。计算了组织等效电离室的k_T值。用铅减弱法测定了碳电离室、铝电离室和GM-2计数管的k_U值。在T(d,n)~He中子场中实验测定了各项修正因子,最后给出了自由空气中生物组织的中子和光子比释动能分量的测量结果以及总不确定度。     

大型单板源Co-60辐照装置的排源方法和实践

本文详细论述了中金辐照成都有限公司BFT-IV辐照装置第二次加源所用排源方案的设计方法和过程。通过理论公式计算该辐照装置源架16个模件的活度占总活度的最优化比例,将新采购的放射源按此比例分为16个小组,装入源架对应模件中,模件内部源棒由人工以均匀方式布置。利用MCNP_4C软件建立辐照装置数学模型,计算剂量分布,用第一次加源后的剂量场分布测试结果验证MCNP模型的有效性。分别计算因人工排列不同形成的多个排源方案的剂量分布,选取最优的排源方案装源。装源后进行剂量分布测试,对于0.1g·cm–3的产品,射线利用率16.7%,辐照箱吸收剂量最大不均度为1.36,优于第一次加源后的剂量分布测试结果,证明排源方法及方案合理有效。     

Progress of neutron induced prompt gamma analysis technique in 1988～2003

This paper describes new development of the neutron induced prompt gamma-ray analysis (NIPGA) technology in 1988～2003. The pulse fast-thermal neutron activation analysis method, which utilized the inelastic re action and capture reaction jointly, was employed to measure the elemental contents more efficiently. Lifetime of the neutron generator was more than 10000h and the performance of detector and MCA reached a high level. At the same time, Monte Carlo library least-square method was used to solve the nonlinearity problem in the NIPGA.     

A Novel Concept of Gamma-Ray Compensation for Neutron Ionization Chamber

A novel method of γ-ray compensation in a neutron ionization chamber (CIC) is developed as an ex-core nuclear instrumentation in a pressurized water reactor. To minimize the dependence of the compensation efficiency on γ-ray dose and dose rate, the improved CIC has the signal electrode with small holes to induce leakage or fringing electric fields. Change in compensation characteristics could be controlled by adjusting the field strength. It has been shown that the compensation margin for adjustment can be extended to 5-8%.     

页岩气储层矿物组分测井分析方法

页岩气藏一般发育在暗色泥页岩、高碳泥页岩及其间所夹砂质、粉砂质岩类地层中,页岩气储层识别与划分以及矿物组分计算,是页岩气储层测井评价中的关键内容.目前国内外页岩气储层测井评价中,一般采用常规测井、元素俘获能谱测井(ECS)、自然伽马能谱测井(NGS)和岩性密度测井等资料来计算页岩的矿物组分.它们不仅为页岩气储层矿物组分问题的解决提供了有效手段,而且对我国页岩气的勘探开发具有一定的借鉴作用.     

麦垛山井田煤岩层变化规律的测井资料研究

麦垛山井田是宁东煤田大型井田之一.利用测井资料对测井曲线的研究发现,同一井田的煤、岩形态和组合特征有一定的规律性,反映到测井曲线上就表现出一定的地球物理特征,包括曲线的幅值、形态、组合特征和某些特殊的物性标志,这些特征及其变化规律在井田内的钻孔中大体一致,因此,确定了宁东煤田麦垛山井田的编号煤层及标志层.通过研究该井田标志层的长源距伽马-伽马、自然伽马和电阻率曲线的形态特征,掌握了主要可采煤层变化规律,从而在宁东煤田中生代含煤地层开展无岩心钻进奠定了基础,这就大大提高了钻探效率,缩短了勘探时间,提高了经济效益,加快了煤炭地质勘探工作进程.     

3类珈玛射线暴的谱硬率研究

珈玛射线暴是目前人类发现的宇宙中能量最高的天文现象,通常认为它可以分为2类.Mukherjee(1998)和Horvath(1999)运用不同的方法,分别独立地得到了可能存在第3类暴的结论,提出珈玛射线暴可以分为3类.根据珈玛射线暴的这一新的分类,人们希望了解第3类暴的性质及与其它类的区别.本文计算了这3类暴的谱硬率,给出了它们的谱硬率分布图和相关系数,并对其进行讨论.新的第3类暴产生的物理机制可能不同于另外的2类暴.     

γ射线辐照对PA6/PTFE合金吸水与力学性能的影响

为了探讨辐照对尼龙6(PA6)基共混材料吸水性能和力学性能的影响,制备了PA6和聚四氟乙烯(PTFE)共混合金并在室温下进行不同剂量的60Coγ射线辐照.通过吸水率测试、准静态拉伸和弯曲实验以及缺口冲击测试,研究了辐照对PA6/PTFE共混体系吸水性能以及吸收水和辐照剂量对共混合金动静态力学性能的影响.结果表明,辐照过程引发交联反应,共混合金的拉伸强度、拉伸模量和弯曲模量均随辐照剂量的增大而增大,而缺口冲击强度和吸水率则随之减小.吸收水对共混合金缺口冲击强度的影响与合金组分有关.PTFE含量较低时,吸收水抑制PTFE对合金冲击强度的减弱作用;当PTFE的质量分数大于7%时,吸收水反而加剧PTFE对材料冲击强度的减弱效应.此外,PA6/PTFE合金的吸水率随PTFE含量的增加而降低,而弯曲模量则先增后减.     

Effects of Gamma Ray Radiation on the Performance of Microelectromechanical Resonators

While much radiation test data are available for metal-oxide-semiconductor (MOS) devices, research into the effects of radiation on microelectromechanical systems (MEMS) is in its relative infancy. Piezoelectrically transduced MEMS resonators have broad applications in signal processing, environmental monitoring, and navigation. Aluminum nitride (AlN), in particular, is an attractive piezoelectric because of its favorable fabrication characteristics and ease of integration into the complementary MOS (CMOS) manufacturing process. The utility of these devices in space and nuclear systems necessitates research into their performance in radiation environments. Resiliency and an established relationship between radiation dose and device behavior provide a critical tool for engineers in their design process. Multiple AlN-based MEMS resonator designs are created and exposed the devices to 1 Mrad(Si) gamma irradiation from a Cobalt-60 source while measuring scattering (S-) parameters in situ. The experimental data are matched to a theoretical model to describe the change in frequency as a function of radiation-induced displacement damage. It is demonstrated that the AlN-based resonators are resilient against radiation-induced charge-trapping effects. Furthermore, a new method is presented of permanent frequency trimming MEMS resonators up to 30% of their bandwidth without modifying quality factor or motional resistance.     

Development of novel rare earth doped fluoride and oxide scintillators for two-dimensional imaging

Two topics were focused.The first one was about the gamma-ray scintillator,Pr3+:Lu3Al5O12(LuAG) .The second one was about neutron scintillator,Ce3+:6LiCaAlF6 and Eu2+:6LiCaAlF6(6LiCAF) .Those scintillators have been developed very recently for modern imaging appli-cations in the medical and homeland security fields.In both cases,the rare earth ions are playing the crucial role as emission centers.Pr3+ in LuAG provided fast 5d→4f transition providing noticeably shorter decay time than that of Ce3+.Among several candidate hosts,LuAG showed the best performance.Bulk crystal growth,basic scintillation properties,two-dimensional gamma-ray imaging and positron emission mammography(PEM) application were demonstrated.Due to the international situation,the homeland security was compromized by illicit traffic of explosives,drugs,nuclear materials,etc.and the ways to its improvement became an important R&D topic.For this purpose the Ce and Eu doped LiCAF ap-peared competitive candidates.Especially,when substitution of 3He neutron detectors was considered,the discrimination ability of gamma-ray from alpha-ray was important.Bulk crystal growth,basic scintillation properties and two-dimensional neutron imaging were demonstrated.