Using Natural Radionuclides to Trace Sources of Suspended Particles in the Lower Reaches of the Yellow River

Natural radionuclides are powerful tools for understanding the sources and fate of suspended particulate matter(SPM).Particulate matter with different particle sizes behaves differently with respect to adsorption and desorption.We analyzed the activi-ties and distribution characteristics of multiple natural radionuclides(238U,226Ra,40K,228Ra,7Be and 210Pbex)on size-fractionated SPM at the Lijin Hydrographic Station(Huanghe or Yellow River)every month over a one-year period.Results showed that medium silt(16–32µm)was the main component.As expected,the activity of each radionuclide decreased with an increase of particle size.We examined the sources of SPM with different particle sizes using activity ratios of 226Ra/238U,228Ra/226Ra,40K/238U and 7Be/210Pbex,and concluded that SPM with different particle sizes originated from different sources.Our results indicate that fine SPM(<32µm)was mainly from the erosion of soil along the lower reaches of the Yellow River,while coarse SPM(>32µm)was mainly derived from resuspension of riverbed sediment.During high runoff periods,the concentration of SPM increased significantly,and the pro-portion of fine particles originating upstream increased.Naturally occurring radioactive isotopes,especially on size-fractionated par-ticles,are therefore seen as useful tracers to understand the sources and behaviors of riverine particles transported from land to sea.

Utilizing Bayesian Modeling and MCMC for Accurate Characterization of Naturally Occurring Radionuclides Reference Background Levels in Mining Areas

Statistical biases may be introduced by imprecisely quantifying background radiation reference levels. It is, therefore, imperative to devise a simple, adaptable approach for precisely describing the reference background levels of naturally occurring radionuclides (NOR) in mining sites. As a substitute statistical method, we suggest using Bayesian modeling in this work to examine the spatial distribution of NOR. For naturally occurring gamma-induced radionuclides like 232Th, 40K, and 238U, statistical parameters are inferred using the Markov Chain Monte Carlo (MCMC) method. After obtaining an accurate subsample using bootstrapping, we exclude any possible outliers that fall outside of the Highest Density Interval (HDI). We use MCMC to build a Bayesian model with the resampled data and make predictions about the posterior distribution of radionuclides produced by gamma irradiation. This method offers a strong and dependable way to describe NOR reference background values, which is important for managing and evaluating radiation risks in mining contexts.

Radionuclide Colloid ^(32)P Used for the Treatment of Stage II Lung Cancer by Video Enhanced Minimal Access Muscle Sparing Thoracotomy

Objective: To study the feasibility of radionuclide colloid 32P used for the treatment of stage II lung cancer by video enhanced minimal access muscle sparing thoracotomy (VEMAST). Methods: Video assisted thoracoscopic surgery (VATS) was carried out under general anesthesia. A double lumen endobronchial tube was intubated into trachea. One lung ventilation of the healthy side was done during operation. An incision of 8–10 cm long was made along the 4th or 5th intercostals. The lobectomy could be performed under VATS. Radionuclide colloid 32P was injected locally into the area where surgical cleaning of lymph node around was considered to be unsatisfactory or desection of the tumor was not completed. Results: The operation with VEMAST was successful in 29 patients. A conventional lobectomy by thoracotomy had to be done due to unusual bleeding from the pulmonary artery involved during VEMAST in one case and the procedure was interrupted because the pulmonary artery cloud not be separated from the tumor in another patient. There was no dead case or the patient who had any severe complication or adverse response to the radiant. Conclusion: Radionuclide therapy was performed to the treatment of stage II lung cancer with VEMAST in case that surgical resection was considered not to be satisfactory. Minithoractomy assisted with VATS lobectomy and radionuclide colloid 32P therapy is a safe and e?ective technique for some selected stage II lung cancer.

多孔材料用于废水中放射性核素吸附的研究进展

针对传统吸附剂对放射性元素的去除,存在吸附时间较长以及吸附效果不理想等不足之处;新型多孔吸附材料如共价有机框架(COF)、金属有机框架(MOF)和共轭微孔聚合物(CMP)等,由于优异的物理化学特性,高比表面积、高孔隙率、快速的电荷载流子迁移率和可调的功能性,对于放射性核素的分离有着更高的分离效率。本文针对多种新型多孔吸附材料COF、MOF和超高交联聚合物(HCP)等对放射性元素的去除,通过总结新型多孔吸附材料用于放射性核素吸附分离的最新研究进展;着重讨论了新型多孔吸附材料的设计制备、放射性元素去除性能以及放射性元素去除机理;最后基于上述分析,提出目前新型多孔吸附材料用于放射性核素吸附分离存在的问题,如难以处理粉末状的新型多孔吸附材料,以及在极端化学条件下容易出现结构不稳定的问题,并对未来的相关研究方向进行了展望,例如将研究从纯粹的基础研究扩展到更实用的方面和大力开发有效的合成方法,以获得高产率且无副产物的产品。

基于序贯贝叶斯方法的核素快速检测方法研究

适当的放射性核素快速检测方法对于具有流量大和计数率水平低特征的海关放射性安检等场景是必要的。相较于传统不确定性分析方法,贝叶斯方法和序贯概率比检验可充分利用测量物理量的全部信息而所需的样本量较少,基于此提出了一种新型序贯贝叶斯核素快速检测方法,分别在低辐射本底环境和自然辐射本底环境,使用一套LaBr3(Ce)探测系统和一组标准点源对该方法的可行性、检测性能和普适性开展了实验研究,并探究了方法的关键参数中第一类错误概率α、第二类错误概率β和时间间隔下限τmin对检测性能的影响。在本底计数率分别为59.3 s^(-1)和165.9 s^(-1)的两类本底环境中,α和β分别不超过0.1和0.01的条件下,实验结果显示:在无源情况下,该方法对本底辐射的平均检出时间分别为24.08 s和10.54 s,平均检出样本量分别为1427和1742,且发生误报后均可快速自适应消除并做出有效判决;在有源情况下,实验测量检测灵敏度下限分别约为8.2%和6.1%,对应的平均检出时间分别为8.59 s和6.61 s,实验测量漏报率均为0,平均检出时间只与全谱净计数率有关,平均检出样本量只与放射源信号的计数率信噪比有关,检测灵敏度下限可理论计算且与实验结果相吻合;参数τ_(min)的减小会增大检测灵敏度下限和减小检出时间,参数α和β可决定实验测量误报率和漏报率。研究表明本方法非常适用于低水平放射性核素的快速检测。

^(125)I的俄歇电子和氚的β射线细胞S值及DNA损伤模拟研究

氚的辐射生物效应一直是研究热点,特别是在福岛核电站排放核废水后成为公众关注的焦点。氚极易进入人体并参与机体代谢活动,衰变放出的β射线对人体具有极大的危害,而靶向放射治疗则利用摄入的俄歇电子发射体能够进入癌细胞,并放出俄歇电子造成DNA严重损伤这一特性,达到有效杀死癌细胞的目的。为探究β射线在微纳米尺度的辐射生物效应,本研究利用清华大学研发的纳剂量学程序NASIC模拟计算了^(125)I和氚在不同尺度细胞内的细胞S值以及造成的DNA双链断裂(DSB)产额,深入探讨了其DNA损伤机制。结果表明,由于研究方法和粒子截面的不同,细胞S值的计算结果存在偏差,尤其对于S(N←Cy),相对偏差可达26.35%。此外,相较于^(125)I或氚均匀分布在细胞核内,与DNA结合时造成的DSB产额显著增加:^(125)I结合到DNA时的DSB产额是均匀分布时的2倍;而氚结合到DNA中使得DSB产额从1.31×10^(-11)Gy^(-1)·Da^(-1)增加至1.46×10^(-11)Gy^(-1)·Da^(-1)。本研究深入探究了微纳米尺度下放射性核素的损伤作用效应,为精确医疗和环境放射性污染风险评估提供重要的理论基础。

基于卷积神经网络的放射性核素识别算法

为实现对低计数、多种类的复杂放射性核素的准确识别,引入卷积神经网络(convolutional neural network,CNN)搭建针对低计数、多种类放射性核素识别模型。利用蒙特卡罗仿真创建由^(241)Am、^(133)Ba、^(57)Co、^(60)Co、^(137)Cs、^(152)Eu以及40K组成的单源、两源以及三源共63种不同种类放射性核素能谱数据库。利用仿真训练集和仿真验证集样本完成CNN训练及超参数优化,利用测试集样本验证模型性能。结果表明,该模型对低计数、多种类放射性核素具有良好的识别性能。

降低环境中放射性核素研究进展

放射性核素中的^(238)U、^(232)Th、^(226)Ra和^(40)K具有很强的毒性,能够通过食物链、食物网和其他途径传播,对人类健康构成长期辐射危害。这些物质即使经过粉碎、高温、烧结等方式处理后仍表现出较高的放射性。现阶段迫切需要寻找切实可行的方法来解决放射性问题。本综述通过物理法、化学法及生物法对降低环境中放射性核素进行了详细的阐述,并就其原理和主要优劣势作简要介绍和评述,展望未来降低放射性的发展趋势,以期为降低放射性方面相关工作提供有价值参考。

梅州地区混凝土放射性核素限量分析

选取梅州地区20组混凝土样品测试放射性核素限量水平,结果显示内照射指数(I_(Ra))范围是:0.13~0.70,外照射指数(I_(r))范围是:0.21~1.13,其中内照射指数(I_(Ra))符合≤1.0,但外照射指数(I_(r))有2组>1.0。混凝土放射性核素限量水平超出使用范围,可以通过改变生产配方或更换原料来源得到控制,本试验采用放射性核素限量相对较低的砂和石替代30%或50%放射性核素限量较高的砂和石,按照同配合比重新配置后的混凝土,放射性核素限量均符合内照射指数(I_(Ra))≤1.0和外照射指数(I_(r))≤1.0的要求。

Baculovirus vector-mediated transfer of NIS gene into colon tumor cells for radionuclide therapy

AIM:To investigate the feasibility of radionuclide therapy of colon tumor cells by baculovirus vector-mediated transfer of the sodium/iodide symporter(NIS) gene.METHODS:A recombinant baculovirus plasmid carrying the NIS gene was constructed,and the viruses(BacNIS) were prepared using the Bac-to-Bac system.The infection efficiency in the colon cancer cell line SW1116 of a green fluorescent protein(GFP) expressing baculovirus(Bac-GFP) at different multiplicities of infection(MOI) with various concentrations of sodium butyrate was determined by flow cytometry.An in vitro cytotoxicity assay was also conducted after infection of SW1116 cells with Bac-NIS.Iodine uptake of Bac-NIS infected SW1116 cells and inhibition of this uptake by sodium perchlorate was examined,and the effect of Bac-NISmediated 131 I in killing tumor cells was evaluated by cell colony formation tests.RESULTS:Infection and transgene expression in SW1116with Bac-GFP were significantly enhanced by sodium butyrate,as up to 72% of SW1116 cells were infected with the virus at MOI of 400 and sodium butyrate at 0.5 mmol/L.No obvious cytotoxicity was observed under these conditions.Infection of SW1116 with Bac-NIS allowed uptake of 131 I in these tumor cells,which could be inhibited by sodium perchlorate.The viability of SW1116 cells infected with Bac-NIS was significantly lower than with Bac-GFP,suggesting that NIS gene-mediated 131 I uptake could specifically kill tumor cells.CONCLUSION:Baculovirus vector-mediated NIS gene therapy is a potential approach for treatment of colon cancer.

A novel approach for radionuclide diffusion in the enclosed environment of a marine nuclear reactor during a severe accident

A severe accident in a marine nuclear reactor leads to radionuclide leakage,which causes hidden dangers to workers and has adverse effects of environmental pollution.It is necessary to propose a novel approach to radionuclide diffusion in a confined environment after a severe accident in a marine nuclear reactor.Therefore,this study proposes a new method for the severe accident analysis program MELCOR coupled with computational fluid dynamics scSTREAM to study radioactive diffusion in severe accidents.The radionuclide release fraction and temperature calculated by MELCOR were combined with the scSTREAM calculations to study the radionuclide diffusion behavior and the phenomenon of radionuclide diffusion in different space environments of the reactor under the conditions of varying wind velocities of the ventilation system and diffusion speed.The results show that the wind velocity of the ventilation system is very small or zero,and the turbulent diffusion of radionuclides is not obvious and diffuses slowly in the form of condensation sedimentation and gravity settlement.When the wind speed of the ventilation system increases,the flow of radionuclides meets the wall and forms eddy currents,affecting the time variation of radionuclides diffusing into chamber 2.The wind velocity of the ventilation system and the diffusion speed has opposite effects on the time variation trend of radionuclide diffusion into the four chambers.

Feasibility of herpes simplex virus type 1 mutants labeled with radionuclides for tumor treatment

For over one hundred years, viruses have been recognized as capable of killing tumor cells. At present, people are still researching and constructing more suitable oncolytic viruses for treating different malignant tumors. Although extensive studies have demonstrated that herpes simplex virus type 1 (HSV-1) is the most potential oncolytic virus, therapies based on herpes simplex virus type 1 vectors still arouse bio-safety and risk management issues. Researchers have therefore introduced the new idea of treating cancer with HSV-1 mutants labeled with radionuclides, combining radionuclide and oncolytic virus therapies. This overview briefly summarizes the status and mechanisms by which oncolytic viruses kill tumor cells, discusses the application of HSV-1 and HSV-1 derived vectors for tumor therapy, and demonstrates the feasibility and prospect of HSV-1 mutants labeled with radionuclides for treating tumors.

Neoadjuvant peptide receptor radionuclide therapy for an inoperable neuroendocrine pancreatic tumor

Pancreatic endocrine tumors are rare but are among the most common neuroendocrine neoplasms of the abdomen.At diagnosis many of them are already advanced and diff icult to treat.We report on an initially inoperable malignant pancreatic endocrine tumor in a 33-year-old woman,who received neoadjuvant peptide receptor radionuclide therapy(PRRT)as firstline treatment.This resulted in a signif icant downstaging of the tumor and allowed its subsequent complete surgical removal.Follow-up for eighteen months revealed a complete remission.This is the first report on neoadjuvant PRRT in a neuroendocrine neoplasm with subsequent successful complete resection.

A novel approach for feature extraction from a gamma‑ray energy spectrum based on image descriptor transferring for radionuclide identification

This study proposes a novel feature extraction approach for radionuclide identification to increase the precision of identification of the gamma-ray energy spectrum set.For easier utilization of the information contained in the spectra,the vectors of the gamma-ray energy spectra from Euclidean space,which are fingerprints of the different types of radionuclides,were mapped to matrices in the Banach space.Subsequently,to make the spectra in matrix form easier to apply to image-based deep learning frameworks,the matrices of the gamma-ray energy spectra were mapped to images in the RGB color space.A deep convolutional neural network(DCNN)model was constructed and trained on the ImageNet dataset.The mapped gamma-ray energy spectrum images were applied as inputs to the DCNN model,and the corresponding outputs of the convolution layers and fully connected layers were transferred as descriptors of the images to construct a new classification model for radionuclide identification.The transferred image descriptors consist of global and local features,where the activation vectors of fully connected layers are global features,and activations from convolution layers are local features.A series of comparative experiments between the transferred image descriptors,peak information,features extracted by the histogram of the oriented gradients(HOG),and scale-invariant feature transform(SIFT)using both synthetic and measured data were applied to 11 classical classifiers.The results demonstrate that although the gamma-ray energy spectrum images are completely unfamiliar to the DCNN model and have not been used in the pre-training process,the transferred image descriptors achieved good classification results.The global features have strong semantic information,which achieves an average accuracy of 92.76%and 94.86%on the synthetic dataset and measured dataset,respectively.The results of the statistical comparison of features demonstrate that the proposed approach outperforms the peak-searching-based method,HOG,and SIFT on the synthetic and measured datasets.

Dating sediments on several lakes inferred from radionuclide profiles

In this paper, several sediment cores from three lakes (Gucheng Lake, Dianchi Lake and Dabusopao Lake) in the different regions of China were dated radiometrically by 210 Pb, 137 Cs and in Dianchi also by 241 Am. The study shows that the profiles of 137 Cs in lake sediment of China generally have 2—4 distinct chronological markers, i.e. the onset of fallout in 1954 and peak fallout in 1963, 1974 and 1986. As many places of the northern hemisphere, the peak fallout in 1963 was the result of the atmospheric atomic weapons test. But in some areas of China, there may be have one or two other peaks of 137 Cs fallout, one can derive from Chernobyl fallout in 1986 and the other is caused by the nuclear testing fallout in early 1970s. So in these areas, the profiles of 137 Cs can have 2 or 3 peaks as the time markers. 241 Am, which is another fallout product from nuclear weapons testing, also provides a useful dating marker in Dianchi. These time markers are of considerable value to confirm 210 Pb dates in the three lakes. Despite there are some questions remain concerning the interpretation of these radionuclide records in lake sediments, coupling with 210 Pb and 137 Cs (and/or 241 Am) is suggested to be a valuable limnological tool for establishing sediment chronologies for the lake sediments in China.

GPU-accelerated three-dimensional reconstruction method of the Compton camera and its application in radionuclide imaging

A novel and fast three-dimensional reconstruction method for a Compton camera and its performance in radionuclide imaging is proposed and analyzed in this study. The conical surface sampling back-projection method with scattering angle correction(CSS-BP-SC) can quickly perform the back-projection process of the Compton cone and can be used to precompute the list-mode maximum likelihood expectation maximization(LM-MLEM). A dedicated parallel architecture was designed for the graphics processing unit acceleration of the back-projection and iteration stage of the CSS-BP-SC-based LM-MLEM. The imaging results of the two-point source Monte Carlo(MC) simulation demonstrate that by analyzing the full width at half maximum along the three coordinate axes, the CSS-BP-SC-based LM-MLEM can obtain imaging results comparable to those of the traditional reconstruction algorithm, that is, the simple back-projection-based LM-MLEM. The imaging results of the mouse phantom MC simulation and experiment demonstrate that the reconstruction results obtained by the proposed method sufficiently coincide with the set radioactivity distribution, and the speed increased by more than 664 times compared to the traditional reconstruction algorithm in the mouse phantom experiment. The proposed method will further advance the imaging applications of Compton cameras.

Use of ^(137)Cs and ^(210)Pb_(ex) fallout radionuclides for spatial soil erosion and redistribution assessment on steeply sloping agricultural highlands

The steeply sloping agricultural highlands in Korea have severe soil erosion.Estimation of both soil erosion and sedimentation in these highlands is necessary to make plans for soil-conservation measures,but it is not feasible using existing soil-erosion models.This study measured the site-specific concentrations of ^(137)Cs and ^(210)Pb_(ex) on both a highland slope(33%slope)and a reference site(undisturbed flat area)to estimate soil erosion and redistribution.The use of the fallout radionuclide(FRN)method was evaluated to see if it is a suitable method for characterizing soil erosion.Results were compared with those obtained with the Universal Soil Loss Equation(USLE),which is an empirical model that estimates annual soil erosion.The average concentrations of ^(137)Cs and ^(210)Pb_(ex) at the reference site were 11.57±0.24 Bq kg^(-1) and 59.74±4.2 Bq kg^(-1),respectively.Concentrations of ^(137)Cs and ^(210)Pb_(ex) in the experimental slope were 16.4%and 10.8%,respectively,of those at the reference site.Radionuclide inventories were lower at the upper point of the slope than those at the basal point of the slope.Concentrations of ^(137)Cs and ^(210)Pb_(ex) were significantly correlated with available phosphorus,organic matter,CEC,and exchangeable cations.Estimation of soil redistribution rate using ^(137)Cs and ^(210)Pb_(ex) showed site-specific variations at different points along the slope,and respective ranges were^(-1)7.46~-207.51 and 1.55~-581.38 Mgha^(-1) yr^(-1),which indicated that more erosion was assessed by ^(210)Pb_(ex) than by ^(137)Cs.Redistribution analysis showed that soil erosion occurred along the entire slope,except for the bottom point of the slope where 1.55 Mgha^(-1) yr^(-1) of sediment accumulated.The USLE provided a single value of the average annual soil loss in the entire slope,which was either 166 or 398 Mgha^(-1) yr^(-1),depending on the soil erodibility factor(soil series factor and calculated factor from soil sample analysis)used in the model.We conclude that the FRN method using ^(137)Cs and ^(210)Pb_(ex) radionuclides can be used to assess soil erosion and redistribution in steeply sloping agricultural highlands.Verification of soil-erosion values using the FRN method and soil-erosion models has been controversial,but it merits further study at many locations with different soils,topography,and management practices.

Radionuclide Contents and Physicochemical Water Quality Indicators in Stream, Well and Borehole Water Sources in High Radiation Area of Abeokuta, Southwestern Nigeria

Water samples from streams, hand-dug wells and boreholes in high background radiation areas in Abeokuta, Nigeria have been collected in order to determine the activity concentrations of 40K, 226Ra and 232Th in the samples as well as their physicochemical characteristics. These parameters were evaluated in order to deter-mine the quality of these water sources to the local population, who use these water resources for drinking and domestic activities. Measurements of radioactivity in the water samples were carried out using γ-ray spectroscopy, while standard chemistry methods were used for the physicochemical determinations of these quality parameters. A total of fourteen representative water samples from streams (7), boreholes (4), and hand dug wells (3) were collected for study. The determined activity concentrations of the radionuclides in these samples were used to calculate the effective dose to the population from due to ingestion of and drink-ing the locally available water. The total annual ingestion effective doses were found to vary between 115.00 &#177;1.15μSv and 1362.30 &#177;438.02 μSv. The physicochemical parameters where found to be lower than the prescribed standard safe limits in the water sources except for the nitrate and phosphate levels which were particularly high in the water samples from boreholes and hand-dug wells. The radiation effective ingestion dose due to ingestion of water from dug wells and streams was found to be higher than the dose due to inges-tion of water from borehole sources in the studied areas. The results obtained in this study, have been taken as a baselines for physicochemical parameters and activity concentrations of natural radionuclides in water samples within Odeda and Obafemi-owode parts of Abeokuta, Nigeria.

Atmospheric Dispersion and Deposition of Radionuclides (¹³⁷Cs and ¹³¹I) Released from the Fukushima Dai-ichi Nuclear Power Plant

The Lagrangian Particle Dispersion Model (LPDM) in the 594 km× 594 km model domain with the horizontal grid scale of 3 km×3 km centered at a power plant and the Eulerian Transport Model (ETM) modified from the Asian Dust Aerosol Model 2 (ADAM2) in the domain of 70° LAT × 140° LON with the horizontal grid scale of 27 km×27 km have been developed. These models have been implemented to simulate the concentration and deposition of radionuclides (137Cs and 131I) released from the accident of the Fukushima Dai-ichi nuclear power plant. It is found that both models are able to simulate quite reasonably the observed concentrations of 137Cs and 131I near the power plant. However, the LPDM model is more useful for the estimation of concentration near the power plant site in details whereas the ETM model is good for the long-range transport processes of the radionuclide plume. The estimated maximum mean surface concentration, column integrated mean concentration and the total deposition (wet+dry) by LPDM for the period from 12 March to 30 April 2011 are, respectively found to be 2.975 × 102 Bq m-3, 3.7 × 107 Bq m-2, and 1.78 × 1014 Bq m-2 for 137Cs and 1.96 × 104 Bq m-3, 2.24 × 109 Bq m-2 and 5.96 × 1014 Bq m-2 for 131I. The radionuclide plumes released from the accident power plant are found to spread wide regions not only the whole model domain of downwind regions but the upwind regions of Russia, Mongolia, Korea, eastern China, Philippines and Vietnam within the analysis period.

Estimation of Annual Effective Dose Due to Ingestion of Natural Radionuclides in Cattle in Tin Mining Area of Jos Plateau, Nigeria

Contamination of land could occur during the extraction and handling of materials containing high levels of naturally occurring radionuclide materials. These radionuclides find their ways into the food chain. The activity concentrations of natural radionuclides 40K, 226Ra, and 232Th in heart, liver, kidney, lungs, spleen and beef of cattle slaughtered and consumed in a tin mining area of Jos Plateau, Nigeria were determined by gamma ray spectroscopy method. The activity concentration of 40K is the highest in all the samples. The annual effective dose to man through the ingestion of the radionuclides in the organs was estimated. The mean annual effective doses calculated are 35.35 ± 13.84, 57.89 ± 38.27 and 46.93 ± 10.28 μSv?y?1 for heart, liver and kidney, respectively. Those of lungs, spleen and meat are 28.44 ± 15.70, 48.34 ± 28.85 and 41.24 ± 3.56 μSv?y?1, respectively. These are of the order of two magnitudes higher than those obtained for food in Abeokuta, Nigeria.