4πγ电离室活度计量标准

为解决高活度γ放射性核素源(如TBq级的源)生产、应用中放射源活度的准确校准,放射性计量测试部在2002年度完成了4πγ电离室活度计量标准装置的研制。 该装置使用4πγ电离室作为探测器,电离电流使用静电计测量。为解决放射源测量过程中的     

γ辐射核素放射性活度测量标准装置

该装置仅适用于γ射线发射体的活度检测，采用的是一种放射性活度相对测量方法。它由充以２．０ＭＰａ氩气的４πγ高气压电离室、小电流测量系统和镭参考源组成。电离室置于１０ｃｍ厚的全封闭屏蔽铅室中的典型本底电流为０．０６６±０．００３ｐＡ。用１７种放射性标准溶液刻度该装置，给出在此参考标准装置上，参考源对于每一种标准源的当量活度，可用于日后检测同种核素样品的活度。对电离室饱和损失、几何效率响应和能响特性予以讨论并给出刻度的总不确定度。     

高气压井型电离室γ核素活度测量装置

本文介绍γ射线活度精密测量用高气压井型电离室及电测系统。整个电离室由不锈钢制成,上下底部为椭圆球面形,并用同轴绝缘子代替两个绝缘子,简化了结构。考虑到对低能γ射线的响应,在设计上采取了特殊措施。测定了电离空的性能,与国外同类仪器相比,有较高的效率,能区宽,本底低,漏气率较小。     

4πγ电离室的直接测量方法

一、引言4πγ电离室的测量对象通常是溶液状的体源,为了减小源的几何效应和源的自吸收以及源瓶壁吸收对电离电流测量结果的影响,历来采用规格化的测量方法,即按规定的重量(或体积)将源溶液置于规定的容器(一般为玻璃安瓿瓶或青霉素瓶)中进行测量。每测量一只源,均需有这样一次制源过程,既费时又费力。因此发展一种可以对盛于不同直     

4πγ电离室活度测量标准装置

文章叙述了所建立的4πγ电离室活度测量标准装置的结构和性能。说明了用~(125)I作为探针,对源瓶子进行筛选的必要性。电离室共刻度了26个核素,刻度的总不确定度(3σ)在1.2%-4.6%。导出了一条完整的4πγ电离室效率曲线,可用来预言未作过刻度的核素的刻度值。     

用于放射性核素活度测量的高效γ射线探测系统

井型 NaI(T1)闪烁探测器用作γ核素活度绝对测量,具有探测效率高、位置依赖性小等优点。除了能精确测定简单衰变纲图的γ核素活度外,还可确定复杂衰变纲图γ核素的活度,以及进行混合核素的分析,总不确定度可达0.1%。这种探测器对于点源、体源、厚源、溶液源等均可测量。避免了4πβ-γ符合法测量时制备专用薄膜源的困难,大大缩短了测量周期。     

4πβ+4πγ活度测量装置研制

基于一种放射性活度测量新方法—4πβ+4πγ计数法的原理，研制并建立起一套4πβ+4πγ活度测量装置。该装置对⁶⁰Co的总探测效率达到99.2%。     

小体积密封γ源活度测量装置研制

为测量5 ×103 ～1 ×10HBq范围内的密封放射性γ源活度,研制了一套小体积密封γ源活度测量装置.描述了装置测量原理及装置的构成,并对装置进行了性能测试,实际测量了放射性γ源并评定了其不确定度.     

模拟土壤中γ放射性核素活度浓度测量比对

本文介绍了本实验室采用效率曲线法和ISOCS模拟法刻度γ谱仪,并对模拟土壤进行了γ放射性核素活度浓度的测量比对工作,获得的结果与参考结果的相对偏差相比均小于20%,验证了2种方法均能满足测量要求,同时能够达到比对目的。     

中子诱发TNT中轻核素反应的混合γ能谱模拟

用MCNP模拟了Am-Be中子源诱发土壤环境中爆炸物各组成核素形成的瞬发γ射线在Nal(T1)和BGO探测器中的能谱,得到H、C、N、O核素特征峰计数随爆炸物质量的变化关系,研究了土壤湿度对γ能谱的影响.通过对中子诱发爆炸物的瞬发γ能谱分析,发现N、C核素特征γ射线全能峰计数之比能较好识别含水环境下的爆炸物.     

工程试验混合堆γ屏蔽的蒙特卡罗法研究

本文给出了用蒙特卡罗和环坐标法研究工程试验混合堆γ屏蔽的结果。结果表明:γ屏蔽对于聚变-裂变混合堆的设计是个非常重要的问题。发现在各种γ射线源中,非弹性散射γ射线源是重要的。混合堆的这个特点与裂变堆是不同的。     

Comparison of depletion algorithms for large systems of nuclides

In this work five algorithms for solving the system of decay and transmutation equations with constant reaction rates encountered in burnup calculations were compared. These are Chebyshev rational approximation method (CRAM), which is a new matrix exponential method, the matrix exponential power series with instant decay and a secular equilibrium approximations for short-lived nuclides, which is used in ORIGEN, and three different variants of transmutation trajectory analysis (TTA), which is also known as the linear chains method. The common feature of these methods is their ability to deal with thousands of nuclides and reactions. Consequently, there is no need to simplify the system of equations and all nuclides can be accounted for explicitly.The methods were compared in single depletion steps using decay and cross-section data taken from the default ORIGEN libraries. Very accurate reference solutions were obtained from a high precision TTA algorithm. The results from CRAM and TTA were found to be very accurate. While ORIGEN was not as accurate, it should still be sufficient for most purposes. All TTA variants are much slower than the other two, which are so fast that their running time should be negligible in most, if not all, applications. The combination of speed and accuracy makes CRAM the clear winner of the comparison.     

Prediction of the delayed neutron yields for actinide nuclides

Prediction of delayed neutron yields for actinides which are important in the nuclear energy field is given. The prediction is based on a correlation related to a suggested cluster structure of the nucleus.     

Beta and X-ray spectrometer for monitoring of beta-radiating nuclides

The design and characteristics of the spectrometer for beta-particles and conversion electrons in the energy range from 15 to 3000 keV and X-ray radiation from 2 to 60 keV are presented. Radiation is detected by a 4.5-mm-thick SiLi detector with a sensitive area of 500 mm/sup 2/. The energy resolution for conversion electrons with the energy of 624 keV is 2.0 keV and, for X-rays with the energy of 5.9 keV, is 280 eV.     

Time-integrated radiotoxicity index for study of transmutation of long-lived nuclides

Radiotoxicity of actinides is investigated based on the Annual Limit on Intake (ALI). A new radiotoxicity index, which takes the radiotoxicity of a parent and its all daughters into account, is defined. Three time-integrated radiotoxicity indices are also introduced for three time intervals of 0 to ∞ (ultimate), 0 to 1 × 10⁴ years (short-term) and 1 × 10⁴ to 1 × 10⁸ years (long-term). For 29 actinides, these indices are calculated theoretically and numerically. The ultimate indices of the actinides are almost the same. The long-term indices, however, show a wide range of values. Neptunium-237 and Am-241 have the largest long-term indices. On the contrary, Pu-240, Pu-242 and Pu-244, Cm-244 and Cm-246 have very small values which are 11/50 to 1/100 of those of Np-237 and Am-241 If these indices are used in the study of transmutation, one can examine and compare easily radiotoxicity and its time dependence for any material.