放射性源强磁打捞器的研制

文章介绍了放射性源强磁打捞器的研制和试验，提出了给打捞主体配备探测器，根据目前测井所用放射性源，设计一种伽马射线顺即可满足要求；并根据井眼条件（有无套管）等方面因素，对打捞主体的机械结构进行了合理设计，该打捞器经七口井的试验，取得了满意的效果。     

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.     

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.     

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.     

核电厂环境放射性本底调查现场工作技术方法

针对某核电厂环境放射性本底调查项目,在明确调查目的和调查内容基础上,依据相关标准规范,结合调查范围内自然和社会环境状况,形成一套高效、实用的现场工作技术方法,并解决了样品采集、测量参数的设定等一系列关键问题,为后续同类项目的顺利实施积累了宝贵经验。     

Nuclear Structure and Galactic γ-Ray Activity

The observation of galactic γ lines following the decay of radioactive nuclei provides a direct link between nuclear physics experiments in earth-based laboratories and astrophysical observations with space-based observatories. Two examples are presented to illustrate this interplay: the measurement of the lifetime of ⁴⁴Ti to allow an improved determination of the ⁴⁴Ti mass of the supernova remnant Cassiopeia A from the observed γ ray activity and the measurements of excited states in ²⁴Si to determine the reaction rate of ²³Al(p, γ)²⁴Si which might be important for a reduced production of ²²Na in novae.     

建筑材料放射性对居室环境质量的影响(二)

(上接 2 0 0 4年第 6期 )2 .4　放射性强度水平的限量民用建筑工程可以分为两类 :一类是指住宅、老年公寓、托儿所、医院、学校等 ;一类是指商场、体育馆、书店、宾馆、办公楼、图书馆、展览馆、文化娱乐场所、公共交通等候室等。照射指数也可以分为外照射指数Ir和内照射指数IRa两种。其中外照射指数Ir是指建材中2 2 6 Ra、2 32 Th、4 0 K 3种天然放射性核素的相对比活度 ,代表了γ射线的强弱程度 ,表示体外照射影响 ;内照射指数IRa是指建材中放射性核素2 2 6 Ra的相对比活度 ,代表了Rn的数量多少 ,表示体内照射影响。GB 6 5 6 6— 2 …     

The natural radioactivity in the bricks used for the construction of the dwelling in Tehran areas of Iran

This paper presents the finding of a study undertaken to determine the natural radioactivity present in bricks in Tehran. A total of 45 samples of commonly used bricks were collected from various manufacturers and suppliers and analyzed using a shielded HPGe gamma ray spectrometer. The specific activities of (226) Ra, (232) Th, and (40) K were measured in all brick samples, and results ranged from minimum values of 26, 24, and 524 Bq kg(-1) to maximum values of 38, 36, and 820 Bq kg(-1) with mean values of 33, 30, and 700 Bq kg(-1) ,respectively. In general, these activities were comparable to the results of similar studies undertaken in another countries. These activities would suggest that the use of such bricks in construction of dwellings or work places in Tehran is unlikely to give rise to any significant radiation exposure to the occupants.     

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.