An Autoradiographical Method Using an Imaging Plate for the Analyses of Plutonium Contamination in a Plutonium Handling Facility

An autoradiographical method using an imaging plate (IP) was developed to analyze plutonium contamination in a plutonium handling facility. The IPs were exposed to ten specimens having a single plutonium particle. Photostimulated luminescence (PSL) images of the specimens were taken using a laser scanning machine. One relatively large spot induced by α-radioactivity from plutonium was observed in each PSL image. The plutonium-induced spots were discriminated by a threshold derived from background and the size of the spot. A good relationship between the PSL intensities of the spots and α- radioactivities measured using a radiation counter was obtained by least-square fitting, taking the fading effect into consideration. This method was applied to workplace monitoring in an actual uraniumplutonium mixed oxide (MOX) fuel fabrication facility. Plutonium contaminations were analyzed in ten other specimens having more than two plutonium spots. The α-radioactivities of plutonium contamination were derived from the PSL images and their relative errors were evaluated from exposure time.     

Actinium-228 in Natural Background Gamma Radiation Spectrum

The natural background γ-radiation was observed by 102.88 cc lithium drifted germanium detector. Twenty-five lines due to ²²⁸Ac were observed in the energy spectrum extending from 50 to 1.280 keV. Comparison with other workers led to identifying two unknown peaks and observing four new lines. A quantitative measurement of the peaks is given in terms of relative intensity of the observed γ-lines.     

核材料检测仪的研制

在原来只适于检测(射线的苯基塑料闪烁体上涂以ZnS薄层，使之对γ射线也有很高的灵敏度。根据光电转换原理，采用PC为主控，并用单片机作为数据预处理器，通过标准串口通讯，构成硬件冗余模式；另外，将传统的直通道设计成直角形，使之既能检测金属容器，又能识别强放射性物质；同时，在出口端加装了限速／位阻拦装置，从而解决了γ射线-金属双重识别，反辐射屏蔽和防高速闯关等难题，大大提高了检测系统的可靠性。PC的数据库操作和远程通信等功能使得本仪器能满足现代高端应用的要求。实测表明，本仪器灵敏度高，可靠性好。对应于3mg的U^235仪器报警响应时间小于0．6s，而拦截动作响应时间不大于2s。     

Muon and neutron-induced background in gamma-ray spectrometry

A low-background γ-ray spectrometer for environmental surveillance, emergency response, and environmental health research has been constructed. It consists of a 132% efficient HPGe detector, graded lead shielding, and muon-rejection shielding, as well as external steel and building shielding. Detailed operation of the γ spectrometer and all of its components is described. Cosmic-ray muon and cosmic-neutron-induced background was accurately measured, and is discussed. We have achieved an overall background reduction by a factor of 9436 relative to the ambient level. Our integrated background rate in the γ energy range of 50-2700 keV was measured as 2.3 counts per min, corresponding to 15 counts ks⁻¹ kg⁻¹ Ge. Future directions in low-background γ spectroscopy at our facility are described.     

The periodic system and the idea of a chemical element: From Mendeleev to superheavy elements

Like other scientific concepts, the idea of a chemical element has changed considerably over time, since it was first established in the Enlightenment era. In Dmitri Mendeleev's construction of the periodic system, he distinguished between simple substances and elements as defined by their atomic weights. The foundation of the periodic system on the latter concept led to several challenges. For example, the system seemed unable to accommodate the radioactive substances eventually recognised as isotopes. Around 1920, elements were consequently redefined in terms of their atomic numbers, a nuclear property that could be determined by X‐ray spectroscopy. Although this understanding of an element has stood the test of time, new questions turned up relating to the concept of an element following the syntheses of transuranic elements since the early 1940s. These syntheses of very heavy elements have additionally led chemists and physicists to reconsider the criteria for the discovery of a new element. Recently, elements have been officially recognised on the sole ground that a small number of very heavy atomic nuclei were identified. The paper discusses how the notion of an element was modified during different periods of time, the reasons for the modifications, and the values ascribed to them in the communities of chemists and physicists.     

从事放射性个人剂量监测分析与防护调查

为了能及时了解放射性工作人员的受照剂量,以便能够更好地保障放射工作人员的健康与安全,采用热释光测量法对包头地区从事放射性工作的工作人员进行了个人剂量监测,并对他们的剂量当量频数分布进行了统计与分析,对工作环境的防护进行了调查对比,就今后的工作提出建议。     

大体积低能β量热装置研制

为了实现大体积样品放射性活度的非破坏性测量．研制了大体积低能β量热装置。该装置采用工作于伺服控制方式的等温型量热计原理．测量腔体积约3200cm3,热功率测量范豳30-2000mW.装置的实验验证表明：当热功率为300mW时,测量结果的扩展不确定度好于0．4％,平均测量时间小于3．5h。本文描述了装置的测量原理、系统组成、校准方法、性能测试及测量不确定度分析等。     

Radioactivity Measurements on Glazed Ceramic Surfaces

A variety of commonly available household and industrial ceramic items and some specialty glass materials were assayed by alpha pulse counting and ion chamber voltage measurements for radioactivity concentrations. Identification of radionuclides in some of the items was performed by gamma spectroscopy. The samples included tableware, construction tiles and decorative tiles, figurines, and other products with a clay based composition. The concentrations of radioactivity ranged from near background to about four orders of magnitude higher. Almost every nuclide identification test demonstrated some radioactivity content from one or more of the naturally occurring radionuclide series of thorium or uranium. The glazes seemed to contribute most of the activity, although a sample of unglazed pottery greenware showed some activity. Samples of glazing paints and samples of deliberately doped glass from the World War II era were included in the test, as was a section of foam filled poster board. A glass disc with known ²³²Th radioactivity concentration was cast for use as a calibration source. The results from the two assay methods are compared, and a projection of sensitivity from larger electret ion chamber devices is presented.     

水中总α、总β放射性实验的影响因素及测量方法讨论北大核心CSCD

利用低本底α、β测量仪,通过一系列比较实验和数据获得影响水中总α、总β放射性活度的实验因素。按照现行国标中的标准曲线法进行实验并分析关系曲线的拟合结果;采用^(241)Am和^(40)K标准粉末源进行串道干扰实验;最后利用热释光测量仪分析影响样品源计数值的因素。结果表明:“质量厚度净计数率”关系曲线线性拟合结果良好,可应用在实验计算中;在测量放射性活度较高的水样时,α通道对β通道产生的串道干扰需进行修正;样品源制备完毕后,不宜立刻测量,应贮存在干燥低本底的环境中,贮存后应用红外灯干燥足够长的时间并完全冷却后进行测量。     

我国锆英砂矿的放射性分析

调查分析了我国3个典型矿区锆英砂堆放表面γ剂量、放射性比活度、铀系和钍系平衡状况以及放射性元素含量；测定了我国海南万宁矿区锆英砂的组成及放射性。结果表明：①我国矿区锆英砂的放射性比活度比澳大利亚的锆英砂高了一个数量级，澳大利亚的锆英砂基本上是符合工业使用要求；②我国山东荣城锆英砂的放射性比活度与澳大利亚锆英砂的放射性比活度接近，但是其中铍的含量很高，不适于用做化工原料；③锆本身不具有放射性，锆英砂的放射性主要是由于锆英砂中存在的独居石等含有少量的铀、钍和镭，使得锆英砂具有了放射性。