天然本底辐射的潜在危险

介绍了天然本底辐射的组成和世界高本底辐射区分布,并以理论和实例说明射线对人体的影响,最后介绍天然辐射剂量测定、调查方法。     

Effects of background radiation on image reconstruction error in computerized tomography

Flaw Detection Research Institute, Kirov Tomsk Polytechnical Institute. Translated from Atomnaya Énergiya, Vol. 70, No. 3, pp. 178–180, March, 1991.     

PIN半导体剂量率探测器的研究

利用大面积PIN硅光电二极管作为探测器,对北京正负电子对撞机BEPCI在同步辐射运行、束流注入、束流切断等情况下对撞区的辐射水平进行测量,并分析辐射本底的强度、来源及特点;研究PIN半导体探测器在BEPCI对撞区的工作状况,为第三代北京谱仪BESⅢ的剂量率在线检测奠定基础。     

三门核电站地区环境辐射本底航空测量调查

2012年9月8日至10月7日,在三门核电站周围地区实施了环境辐射本底航空测量调查,完成航空测量面积7 192.7 km2,采集了99 577组航空测量数据,给出了三门核电站周围地区环境辐射本底水平、天然放射性核素40K、238U、232Th活度浓度的分布。结果表明:三门核电站周围地区环境辐射水平显现为"西北地区高、西南与东北地区偏高、中部地区中低水平"的特点。未发现有可分辨的人工放射性核素分布,亦未发现失控的放射源,发现了2个航测辐射热点,均为地质环境中天然放射性核素偏高引起。     

Tangential force and heating rate of a neutral relativistic particle mediated by equilibrium background radiation

A relativistic theory of fluctuation-electromagnetic interaction of a small neutral polarizable particle moving with respect to the equilibrium background radiation is developed. It is assumed that the particle radius is smaller then the characteristic wave length of the background radiation. General relativistic relations for the particle heating rate and tangential force are obtained and compared with the nonrelativistic and relativistic expressions of other authors.     

Natural convection/radiation heat transfer simulations of enclosed array of vertical rods

Abstract

Experiments performed by Arya and Keyhani (1990) measured the temperature of 12 vertical heated rods within a constant temperature, internally finned cylindrical enclosure. Measurements were performed with air and helium in the enclosure for ranges of rod heat generation rate and gas pressure. In the current work, steady three-dimensional computational fluid dynamics simulations of conduction, natural convection and radiation heat transfer within the experiment were conducted to benchmark the simulation techniques. In the computational model, different thermal conductivities were applied to a spacer plate between a plate that held the heaters, and one of the enclosure endplates. This was done to model a range of contact resistance between the plates. This was necessary because the experimental endplate conditions were not completely documented. The calculations accurately reproduced the local and average temperatures when a high contact resistance was modelled. These results emphasise that conditions far from data measurement locations can affect experimental results. Those conditions must be well documented if they are to be used to benchmark computational methods.     

Electronic background rejection in a new ultra-low background alpha-particle counter

Low background alpha-particle (α) counting is required in the semiconductor industry, where α’s produce single event errors. Industry road maps call for measuring α emissivities at 0.0005 α/cm²/h, while current commercial counter backgrounds are 0.005 α/cm²/h, a factor of 10 too high. This paper shows that by designing an ionization chamber so that ionization tracks collected from the sample have long risetimes while those collected from the anode have short risetimes, signal risetime analysis can distinguish α emanation location within the counter. Coupled with a guard electrode to reject tracks emitted from the counter sidewalls, the method can achieve backgrounds approaching 0.0001 α/cm²/h, a factor of 20 lower.     

Bayesian PIXE background subtraction

The subtraction of the X-ray background in a PIXE spectrum has been the subject of many investigations and different techniques have been developed. These techniques vary from filtering to fitting polynomial functions. The promising Bayesian Statistics technique has been used in this study to eliminate the background from the spectrum in a rigorous and self-consistent manner. We compare the results of the Bayesian background subtraction method to that obtained by stripping and the “rolling ball”; method.     

Containments — Design principles and background

The containment is an important safety system which as an ultimate barrier prevents the release of fission products in case of a severe accident. The principal layout which is based on the Design Basis Accident (DBA) philosophy is described. An attempt has been made to summarize the results of many experimental activities performed during the last 15 years which back-up the analytical simulation models serving for design purposes. The permanent comparison of analytical computation with experimental evidence allowed a continuous evolution of the predictive capabilities and the quantification of existing design margins. The paper shows the broad engineering basis which justifies the believe in the reliability of the containment system under Design Basis Accident conditions. Considerable margins exist before a containment may fail even if an accident may go beyond the design basis.     

The background calculation of the filter-fluorescer method

For the measurement of X-ray energy spectrum with filter-fluorescer method,the high energy tail at the rearward of response function is the main source of background.There are,traditionally,two techniques for measuring the background contributions:the same element Z for the fluorescer and filter,or the same element Z?1 for them.Using the formula of fluorescence intensity,and the elemental combinations of cobalt and iron,the backgrounds which the two techniques provide and the real one for measuring black-body radiation at equilibrium temperature of 7×106 K,were calculated.The results show that the Co-Co combination for the filter-fluorescer spectrometer can achieve better effect.A semi-quantitative analysis for the calculation results is discussed.