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1.
Emissions from medical isotope production are the most important source of background for atmospheric radioxenon measurements, which are an essential part of nuclear explosion monitoring. This article presents a new approach for estimating the global annual radioxenon emission inventory caused by medical isotope production using the amount of Tc-99m applications in hospitals as the basis. Tc-99m is the most commonly used isotope in radiology and dominates the medical isotope production. This paper presents the first estimate of the global production of Tc-99m. Depending on the production and transport scenario, global xenon emissions of 11–45 PBq/year can be derived from the global isotope demand. The lower end of this estimate is in good agreement with other estimations which are making use of reported releases and realistic process simulations. This proves the validity of the complementary assessment method proposed in this paper. It may be of relevance for future emission scenarios and for estimating the contribution to the global source term from countries and operators that do not make sufficient radioxenon release information available. It depends on sound data on medical treatments with radio-pharmaceuticals and on technical information on the production process of the supplier. This might help in understanding the apparent underestimation of the global emission inventory that has been found by atmospheric transport modelling.  相似文献   

2.
Understanding radioxenon time series and being able to distinguish anthropogenic from nuclear explosion signals are fundamental issues for the technical verification of the Comprehensive Nuclear-Test-Ban Treaty. Every radioxenon event categorisation methodology must take into account the background at each monitoring site to uncover anomalies that may be related to nuclear explosions. Feedback induced by local meteorological patterns on the equipment and on the sampling procedures has been included in the analysis to improve a possible event categorisation scheme. The occurrence probability of radioxenon outliers has been estimated with a time series approach characterising and avoiding the influence of local meteorological patterns. A power spectrum estimator for radioxenon and meteorological time series was selected; the randomness of the radioxenon residual time series has been tested for white noise by Kolmogorov–Smirnov and Ljung–Box tests. This methodological approach was applied to radioxenon data collected at two monitoring sites located at St. John’s, Canada and Charlottesville, USA, equipped with two different noble gas systems. It shows different feedback with local meteorological patterns and randomness for the radioxenon data recorded at the selected sites of St. John’s and Charlottesville as well as a different occurrence probability of the outliers in the normalized radioxenon original and residual time series.  相似文献   

3.
Activity concentration data from ambient radioxenon measurements in ground level air, which were carried out in Europe in the framework of the International Noble Gas Experiment (INGE) in support of the development and build-up of a radioxenon monitoring network for the Comprehensive Nuclear-Test-Ban Treaty verification regime are presented and discussed. Six measurement stations provided data from 5 years of measurements performed between 2003 and 2008: Longyearbyen (Spitsbergen, Norway), Stockholm (Sweden), Dubna (Russian Federation), Schauinsland Mountain (Germany), Bruyères-le-Châtel and Marseille (both France). The noble gas systems used within the INGE are designed to continuously measure low concentrations of the four radioxenon isotopes which are most relevant for detection of nuclear explosions: 131mXe, 133mXe, 133Xe and 135Xe with a time resolution less than or equal to 24 h and a minimum detectable concentration of 133Xe less than 1 mBq/m3. This European cluster of six stations is particularly interesting because it is highly influenced by a high density of nuclear power reactors and some radiopharmaceutical production facilities. The activity concentrations at the European INGE stations are studied to characterise the influence of civilian releases, to be able to distinguish them from possible nuclear explosions. It was found that the mean activity concentration of the most frequently detected isotope, 133Xe, was 5–20 mBq/m3 within Central Europe where most nuclear installations are situated (Bruyères-le-Châtel and Schauinsland), 1.4–2.4 mBq/m3 just outside that region (Stockholm, Dubna and Marseille) and 0.2 mBq/m3 in the remote polar station of Spitsbergen. No seasonal trends could be observed from the data. Two interesting events have been examined and their source regions have been identified using atmospheric backtracking methods that deploy Lagrangian particle dispersion modelling and inversion techniques. The results are consistent with known releases of a radiopharmaceutical facility.  相似文献   

4.
During on-site inspections to verify the comprehensive nuclear-test-ban treaty (CTBT), soil gas samples may be taken and analysed for their content of the xenon isotopes 131mXe, 133Xe, 133mXe and 135Xe in order to identify a suspected underground nuclear test. These samples might contain natural radioxenon which is present as a trace gas in the ground. This work analyses the different production mechanisms of natural lithospheric radioxenon to assess theoretically the background concentration under different sampling conditions. The results imply that the equilibrium concentrations of the examined xenon isotopes can be measured in certain rock types using actual CTBTO on-site inspection equipment. Radioxenon production is dominated by spontaneous fission of 238U, resulting in a reactor-like xenon isotopic signature rather than an explosion-like signature.  相似文献   

5.
Atmospheric measurement of radioactive xenon isotopes (radioxenon) plays a key role in remote monitoring of nuclear explosions, since it has a high capability to capture radioactive debris for a wide range of explosion scenarios. It is therefore a powerful tool in providing evidence for nuclear testing, and is one of the key components of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The reliability of this method is largely based on a well-developed measurement technology. In the 1990s, with the prospect of the build-up of a monitoring network for the CTBT, new development of radioxenon equipment started. This article summarizes the physical and technical principles upon which the radioxenon technology is based and the advances the technology has undergone during the last 10 years. In contrast to previously used equipment, which was manually operated, the new generation of radioxenon monitoring equipment is designed for automated and continuous operation in remote field locations. Also the analytical capabilities of the equipment were strongly enhanced. Minimum detectable concentrations of the recently developed systems are well below 1 mBq/m3 for the key nuclide 133Xe for sampling periods between 8 and 24 h. All the systems described here are also able to separately measure with low detection limits the radioxenon isotopes 131mXe, 133mXe and 135Xe, which are also relevant for the detection of nuclear tests. The equipment has been extensively tested during recent years by operation in a laboratory environment and in field locations, by performing comparison measurements with laboratory type equipment and by parallel operation. These tests demonstrate that the equipment has reached a sufficiently high technical standard for deployment in the global CTBT verification regime.  相似文献   

6.
Monitoring of radioactive noble gases, in particular xenon isotopes, is a crucial element of the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The capability of the noble gas network, which is currently under construction, to detect signals from a nuclear explosion critically depends on the background created by other sources. Therefore, the global distribution of these isotopes based on emissions and transport patterns needs to be understood. A significant xenon background exists in the reactor regions of North America, Europe and Asia. An emission inventory of the four relevant xenon isotopes has recently been created, which specifies source terms for each power plant. As the major emitters of xenon isotopes worldwide, a few medical radioisotope production facilities have been recently identified, in particular the facilities in Chalk River (Canada), Fleurus (Belgium), Pelindaba (South Africa) and Petten (Netherlands). Emissions from these sites are expected to exceed those of the other sources by orders of magnitude. In this study, emphasis is put on 133Xe, which is the most prevalent xenon isotope. First, based on the emissions known, the resulting 133Xe concentration levels at all noble gas stations of the final CTBT verification network were calculated and found to be consistent with observations. Second, it turned out that emissions from the radioisotope facilities can explain a number of observed peaks, meaning that atmospheric transport modelling is an important tool for the categorization of measurements. Third, it became evident that Nuclear Power Plant emissions are more difficult to treat in the models, since their temporal variation is high and not generally reported. Fourth, there are indications that the assumed annual emissions may be underestimated by factors of two to ten, while the general emission patterns seem to be well understood. Finally, it became evident that 133Xe sources mainly influence the sensitivity of the monitoring system in the mid-latitudes, where the network coverage is particularly good.  相似文献   

7.
随着新观测技术和理论的进一步发展,同位素地球化学方法在地震监测预测研究中发挥了越来越重要的作用。通过同位素地球化学方法确定地下流体来源,研究地下流体循环特征,分析地震前兆异常的成因,评估地质构造活动的程度,开展地震预测研究。同位素示踪技术还可以结合深源流体监测和地球物理方法,揭示地震孕育、流体与震源之间的关系。此外,同位素地球化学还可以构建断裂带流体地球化学背景特征,用于地震监测点映震效能的评估,提高地震监测预测的准确性,为地震新监测点的布设和震情跟踪提供技术支撑。通过对现今同位素在地震监测预测中所使用的方法、技术及国内外应用情况的总结分析,力图全面认识同位素地球化学在地震监测预测应用中的现状及发展趋势。  相似文献   

8.
介绍了中国新疆维吾尔自治区地震局和乌兹别克斯坦共和国科学院地震研究所近 1 0年来地震科技合作在地下水碳同位素方面的基本研究成果。结合天山主要地震活动区 2 0 0余个水点的碳同位素观测资料 (其中乌鲁木齐地下水中碳同位素资料是第一次公布 ) ,分析了水中碳同位素的区域分布规律、来源及影响因素 ,探讨了碳同位素地震前兆异常的某些特征。  相似文献   

9.
We explained spectra of distant tsunamis observed in enclosed basins by applying the synthesis method based on joint analysis of tsunami and background spectra from a number of stations. This method is the generalization of the method proposed by Rabinovich (J. Geopys. Res. 102, 12663-12676, 1997) to separate source and topography effects in recorded tsunami waves. The source function is extracted by inversion of the tsunami/background spectra averaged from many observational sites. The method is applied to the 2009 Papua tsunami observed at the Owase tide station in southwest Japan, a region with complicated topography and numerous bays and inlets. The synthesized spectrum explains the observed spectral amplitudes for each frequency component. It is shown that averaging of tsunami and background from various tide gauge stations in semi-enclosed basins is an efficient approach to extract the source function.  相似文献   

10.
In order to add earthquake monitoring methods and develop new method research, the ELF Network for Earthquake Monitoring selected 30 stations in the Capital Circle and the Sichuan-Yunnan region. Finding electromagnetic field background variation is the basis of distinguishing the seismic electromagnetic anomalies. This paper introduces the data acquisition and selection of the Shexian, Anqiu, Lijiang and Dali stations which have recorded for longer time with better data and are located on the similar latitude. Then we use the natural source electromagnetic field''s auto-power spectrum to express the intensity of the electromagnetic field. By using power spectral data of many frequencies in the observation frequency band, after the data pre-processing and sliding average noising, the background variation of extremely low frequency stations and the range ability were acquired. Taking the Baoshan M5.1 earthquake on October 30, 2015 and Dali M5.0 earthquake on May 18, 2016 as examples, the authors analyzed the earthquake electromagnetic anomaly characteristic of ELF stations around the earthquakes.  相似文献   

11.
The paper describes the principles and techniques used to detect signals propagating in the atmosphere in the infrasonic frequency range. Such signals can be generated by different sources: ground and atmospheric explosions, as well as objects moving in the atmosphere at supersonic speed (aircraft, rockets, bolides, fragments of spent stages of launch vehicles). Portable infrasound monitoring stations are described, each of which includes three spaced infrasonic microphones. Each such station makes it possible to determine three basic parameters of the detected infrasound signal, which are subsequently used to solve the direction- finding problem: the time of arrival of an infrasonic wave, the azimuth to the source in the horizontal plane, and the wave approach angle from the source of infrasonic waves to the Earth’s surface in the vertical plane. An acoustic detector used to extract useful signals against a noise background is described. The detector is based on an algorithm similar to the STA/LTA detection algorithm known in seismology. Examples of the operation of an acoustic detector with data obtained during real measurements are given. Passive infrasound direction-finding technology is described. It is based on mathematical modeling of the of infrasonic wave propagation in the atmosphere, which are generated by objects moving along possible trajectories; comparison of theoretical signals with real ones recorded by monitoring stations; and determination of the realized trajectories. The paper gives examples of experimental verification of the effectiveness of passive infrasound direction-finding technology for determining the impact points of the first and second stages of launch vehicles. It is shown that infrasound direction-finding systems makes it possible to reduce the estimated search area for launch vehicle fragments that fall to the Earth, significantly decrease the time and costs for their search and utilization, and mitigate the negative environmental impact of the rocket and space industry.  相似文献   

12.
B. Abou Zakhem  R. Hafez 《水文研究》2010,24(18):2641-2654
The chemical and isotopic composition of monthly composite rain samples collected at 13 meteoric stations in Syria during two hydrological cycles from 1991 to 1993 have been measured. The chemical analysis of the samples revealed at a number of stations pollution due to industry and sand storms. The temporal and spatial variation of the isotopic composition has been found to be comparable with one of the neighbouring countries such as Jordan and others. The average weighted oxygen‐18 and deuterium values are − 7·5 and − 39·11‰, respectively, and the deuterium excess is 21‰ . The individual isotope values can be divided into two groups. One group is represented by winter precipitation and fits closely the Mediterranean Meteorological Water Line (MMWL). Thus, for winter precipitation, condensation of Mediterranean water vapour appears to be the dominating isotope fractionation process. The other group represents spring precipitation and is spread along an evaporation line below the MMWL, thus indicating the influence of sub‐cloud evaporation. The d‐excess has been found to be lower in the north of Syria (19·9‰ at Tartous, 18·1‰ at Jarablous) than in the south of the country (23·4‰ at Sweida, 24·1‰ at Izra) where Mediterranean air mass dominates. The d‐excess of precipitation in neighbouring countries is also close to the average value of the eastern Mediterranean basin of 22‰ , e.g. for Jordan the value is 23‰ , which signifies that Mediterranean water vapour is, for all these countries, the dominant source of precipitation. The tritium content of precipitation was found to increase with distance from the coast (5·3 TU at coastal station Tartous, 8·8 TU at continental station Palmyra). Low tritium content and high d‐excess at coastal stations clearly indicate a Mediterranean air moisture source. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

13.
左开挺 《华南地震》1991,11(4):45-54
通过对广州地磁台环境干扰源的监测，计算与分析得到：（1）不同时期产生的二个干扰源对地磁台1号墩磁场总强度测值的迭加影响为－25nT，与多台资料对比结果一致。（2）地磁台1号和5 ，1号与干扰源场区外Ⅰ号比测墩测得的磁场总强度、水平强度及垂直强度之差随时间的变化不明显，故认为广州地磁台环境干扰源目前尚属稳定。  相似文献   

14.
Optimum strong-motion array geometry for source inversion is quantitatively determined for each of three types of earthquake faults: strike—slip, dip-slip and offshore subduction thrust. The estimation is done by using the source inversion method1,2 previously developed and based on Wolberg's prediction analysis.3 Only the far-field S waves are taken into account in source inversion; we test only the ability to estimate seismic moments of subfault elements. A comparison of the optimum array geometries obtained in this study with the ones proposed on the basis of an empirical judgment at the 1978 International Workshop on Strong-Motion Earthquake Instrument Arrays4 shows that the Workshop geometries are not the best ones as far as source studies are concerned. The most preferable array involves two different kinds of stations regardless of the target fault type: stations close to the fault and aligned parallel to its strike, and stations surrounding the fault area with good azimuthal coverage. The former stations resolve the later stage of the rupturing process while the latter stations resolve the earlier stage.  相似文献   

15.
对福建气枪源探测实验中所接入315个实时传输台站分1~10 Hz、0.1~1 Hz、10~60 s 3个频段进行台网噪声水平评估研究。统计240个小时的背景噪声记录,得到各台站的噪声水平MODE线,再利用本文提出的全球新高低噪声模型线与MODE线所占面积比来量化台网噪声水平,根据不同色标将台网噪声水平划分为十个等级进行评估,评选出优质台站。进一步研究背景噪声对气枪激发效果的影响,验证了台站接收能力与背景噪声密切相关,分析了不同台基（固定、加密、流动、海底）环境噪声水平的影响,得出环境噪声水平由低到高分别为固定台、加密台、流动台、海底台。通过台网噪声评估能有效提高气枪震源信号的检测能力,也为优质台站重点维护提供重要参考。  相似文献   

16.
Recently amended European (EU) water policies call for an adequate monitoring of the chemical status of sediments and suspended matter (SM) in rivers. In this study, we focus on long‐term time series of particle‐bound hexachlorobenzene (HCB) and selected polychlorinated biphenyls (PCB‐138 and PCB‐153) that were monitored biweekly to monthly at eight stations in the River Rhine catchment. Our aims are (1) to detect trends in the concentration series HCB, PCB‐138 and PCB‐153, (2) to estimate the uncertainty of loads caused by SM collection techniques and load calculation procedures and (3) to detect trends in the subsequently calculated annual load series. HCB concentration in the SM for the period 1995–2008 significantly (p < 0·01) decreased at six of the eight monitoring stations. Decreasing PCB‐138 and PCB‐153 concentrations are significant at six of the eight and seven of the eight monitoring stations, respectively. A two‐way analysis of variance (ANOVA) that tested the effect of two collection techniques and four load calculation procedures on annual loads indicates homogeneity of the methods at four of the five monitoring stations. At Weil, only the loads of HCB, PCB‐138 and PCB‐153 are significantly affected by the collection technique. The trend analysis of an extended series (1985–2007) of annual HCB loads at Koblenz showed a significant decrease from about 110 kg year?1 to about 15–23 kg year?1; however, in the shorter period (1995–2007) only at two of the eight monitoring stations decreasing trends of annual contaminant load could be detected. We conclude that any of the tested load calculation procedures can be applied, as loads do no differ systematically. Although a high uncertainty in load estimation exists (e.g. maximum percentage error of E = [18·1, 122·5]% for HCB), the monitoring programme at the Rhine is adequate for analysing the long‐term chemical status of SM. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

17.
地震监测中的电阻率层析技术   总被引：15，自引：1，他引：15       下载免费PDF全文
将电阻率层析技术应用于地震监测,由视电阻率值重建出介质的真电阻率图像,取得了较好效果.在宝坻台和昌黎台设立的两个试验点上于1998年4月14日ML5.0和ML4.4唐山两次地震前的6天左右层析图像出现了明显的异常变化:宝坻台的电阻率图像一改通常的在平稳背景上叠加小量随机变化的特点,出现了一种有序性特征的新图样;昌黎台也出现了反差加大、高低阻区集中分布的有序性特征.上述异常图样均在震后消失.层析图像在震前出现的熵值降低可能是这次地震活动的前兆.地层导电结构和孔隙度的变化,是引起电阻率异常的直接原因.研究表明,常规的单一极距的视电阻率测量之所以对真电阻率的变化不敏感且丧失空间分辨能力,是由于该物理量同时具有积分值和位函数这两个固有特征所决定的.在地震监测中,改造现行观测系统,引入层析成像,是发展技术的方向.  相似文献   

18.
Both radioxenon and radioiodine are possible indicators for a nuclear explosion. Therefore, they will be, together with other relevant radionuclides, globally monitored by the International Monitoring System in order to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty once the treaty has entered into force. This paper studies the temporal development of radioxenon and radioiodine activities with two different assumptions on fractionation during the release from an underground test. In the first case, only the noble gases are released, in the second case, radioiodine is released as well while the precursors remain underground. For the second case, the simulated curves of activity ratios are compared to prompt and delayed atmospheric radioactivity releases from underground nuclear tests at Nevada as a function of the time of atmospheric air sampling for concentration measurements of 135I, 133I and 131I. In addition, the effect of both fractionation cases on the isotopic activity ratios is shown in the four-isotope-plot (with 135Xe, 133mXe, 133Xe and 131mXe) that can be utilized for distinguishing nuclear explosion sources from civilian releases.  相似文献   

19.
XIE Tao  LU Jun  YAN Wei 《地震地质》2019,41(6):1464-1480
Parts of the consecutive apparent resistivity monitoring stations of China have recorded clear diurnal variations. The relative amplitudes of diurnal variations at these stations range from 1.3‰ to 5.8‰. The daily accuracies of apparent resistivity observation are better than 1‰, because the background electromagnetic noise is rather low at these stations. Therefore, the diurnal variations of apparent resistivity recorded at these stations are real phenomena. The diurnal variation shapes can be divided into two opposite types according to their characteristics. One type is that the apparent resistivity data decreases during the daytime but increases during the nighttime(Type 1). The other type is the apparent resistivity data increases during the daytime but decreases during the nighttime(Type 2). There is a correspondence between the diurnal and annual variation patterns of apparent resistivity. For the monitoring direction with diurnal variation of Type 1, the apparent resistivity decreases in summer and increases in winter. However, for the monitoring direction with diurnal variation of Type 2, the apparent resistivity increases in summer and decreases in winter. We take an analysis on the mechanism of apparent resistivity diurnal variation, combining the influence factors of water-bearing medium's resistivity, the electric structure of stations, and the apparent resistivity sensitivity coefficient(SC)theory. Intuitively, diurnal variation of apparent resistivity is caused by diurnal variation of medium resistivity in the measured area. The diurnal variation of medium resistivity will inevitably be caused by the factors with diurnal variation. Among the possible factors, there is diural variation in earth tide and temperature. Our analysis displays that apparent resistivity diurnal variation is not caused by the usually-believed earth tide, but by the ground temperature difference between daytime and nighttime. The earth tide strain is too small to cause remarkable effects on the apparent resistivity data. On the other hand, the daily tide strain has two peak-valley variations, and its phase and amplitude has a period of approximate 28 days. However, the apparent resistivity data do not show these corresponding features to earth tide. Furthermore, the detection range of current apparent resistivity stations is within a depth of several hundred meters. Within this depth range, the medium deformation caused by solid tide can be regarded as uniform change. Therefore, all monitoring directions and all stations will have the same pattern of diurnal variation. In general, the temperature increases in the daytime but decreases in the nighttime. For most water-bearing rock and soil medium, its resistivity decreases as temperature increases and increases as temperature decreases. Diurnal temperature difference affects about 0.4m of soil depth. Therefore, resistivity of this surface thin soil layer decreases in the daytime while increases in the nighttime. Under layered medium model, SC of each layer represents its contribution to the apparent resistivity. For the stations with positive SC of surface layer, apparent resistivity decreases in the daytime but increases in the nighttime. While for the stations with negative SC of surface layer, apparent resistivity diurnal variations display the opposite shape.  相似文献   

20.
The continuous real‐time analysis, at 30‐s intervals, of precipitation at an Australian tropical location revealed extreme and rapidly changing δ18O and δD values related to variations in moisture source areas, transport paths and precipitation histories. The range of δ18O (?19.6‰ to +2.6‰) and δD (?140‰ to +13‰) values from 5948 measurements of nine rain events over 15 days during an 8‐month period at a single location was comparable with the range measured in 1532 monthly samples from all seven Australian Global Network of Isotopes in Precipitation stations from 1962 to 2002. Extreme variations in δ18O (?8.7‰ to ?19.6‰) and δD (?54‰ to ?140‰) were recorded within a single 4‐h period. Real‐time stable isotope monitoring of precipitation at a high temporal resolution enables new and powerful tracer applications in climatology, hydrology, ecophysiology and palaeoclimatology. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

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