Enrico Fermi’s Discovery of Neutron-Induced Artificial Radioactivity: Neutrons and Neutron Sources

We reconstruct and analyze the path leading from James Chadwick’s discovery of the neutron in February 1932 through Frédéric Joliot and Irène Curie’s discovery of artificial radioactivity in January 1934 to Enrico Fermi’s discovery of neutron-induced artificial radioactivity in March 1934. We show, in particular, that Fermi’s innovative construction and use of radon-beryllium neutron sources permitted him to make his discovery.     

The Window of Opportunity: Logic and Chance in Becquerel's Discovery of Radioactivity

The discovery of radioactivity by Henri Becquerel is frequently called serendipitous, because on March 1, 1896, he developed "unexposed" photographic plates, which he had kept near a uranium salt, and found dark images on them. I show that Becquerel's discovery was a process in which, even in its early stage in 1896, chance entered in a number of episodes, and that his discovery resulted from a complex interaction of logic and chance.     

Radioactivity distribution at MAFF

A detailed account on the distribution of radioactive nuclei in the vacuum system of the planned Munich Accelerator for Fission Fragments (MAFF) located at the FRM-II research reactor is presented. Tools used for the simulation of spacial and temporal distribution of radionuclides are explained. The latter allows for a detailed activity budget as well as estimates for the mass-separated ion yields at MAFF. Additionally, a concept to reduce the activity release from the MAFF slit system due to surface sputtering is presented. It is shown, that the use of low-density carbon foam, as a surface coating, reduces sputtering by orders of magnitude.     

Radioactivity in Cervidae antlers

The experience gained in this study indicated that Cervidae antlers afford a convenient means for measuring levels of ambient radioactivity over large areas. By the use of antlers, it was possible to compare Sr⁹⁰ levels resulting from bomb testing “fallout” year by year from 1943 through 1958 in a number of areas in the United States, Canada, and Alaska. The most surprising finding was the very high levels for Alaska in 1958. From calculations based on total beta counts in antlers, it was possible to show that the radiation dose delivered to bone from short-lived fission products is insignificant as compared to the dose delivered by Sr⁹⁰/Y⁹⁰.     

质子衰变研究

介绍了质子衰变的基本原理,综述了质子衰变实验研究的现状． The principle of proton radioactivity is introduced. The present status of experimental studies on proton radioactivity is reviewed.      

重核的结团放射性

对重核的结团放射性(¹⁴C—³⁴Si)的实验数据进行了系统的分析和研究.提出了一个描述结团放射性寿命的新公式.理论计算结果与实验寿命在5倍以内符合.指出结团放射性的衰变能和结团内α粒子数有一个新的线性关系,标志着重核表面有α凝聚.     

Theoretical Studies of Proton Radioactivity

In the paper, we will discuss the most recent theoretical approaches developed by our group,to understand the mechanisms of decay by one proton emission, and the structure and shape of exotic nuclei at the limits of stability.     

便携式食品放射性检测仪的研制及测试

设计了一种便携式食品放射性检测仪,主要包括测量结构、核信号处理单元和能谱分析程序。核信号处理单元主要包括抗混叠低通滤波器、程控增益放大器、高速A/D采样、数字低通滤波、梯形成形、脉冲幅度甄别和能谱获取等。能谱分析程序主要包括能谱光滑、能谱寻峰、能量刻度、本底扣除以及活度计算等。最后,以测量¹³¹I核素为例,研究了仪器对不同体积样品的探测效率、刻度系数和最低可探测活度,并根据刻度系数对300 mL食品样品的放射性测量结果进行校正。结果表明,仪器对常见食品中¹³¹I的放射性活度检测结果误差小于10%,满足食品放射性测量需求。     

Radioactivity in technological NPP waste

Concentrations of radionuclides in liquid and solid technological waste of the South-Ukrainian Nuclear Power Plant were studied. It is shown that correlated variation in radionuclide content of all samples is observed. Simple relations are derived for evaluating concentrations of radionuclides from the data on the ⁶⁰Co and ¹³⁷Cs activities. Original Russian Text ? M.D. Bondar’kov, A.M. Maksimenko, I.N. Vishnevskii, V.A. Zheltonozhskii, M.V. Zheltonozhskaya, L.V. Sadovnikov, S.V. Il’ichev, V.V. Boyarishchev, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 279–282.     

Stefan Meyer: Pioneer of Radioactivity

Stefan Meyer was one of the pioneers in radioactivity research and director of the Vienna Radium Institute, the first institution in the world devoted exclusively to radioactivity. I give here a biographical sketch of Meyer and of some of his colleagues and an overview of the research activities at the Radium Institute.     

铅以上核结团放射性再研究(英文)

在密度依赖的结团模型下重新研究了铅以上原子核的结团放射性。根据由核电荷半径以及中子皮厚度的实验数据所提炼的子核和结团密度分布,通过双折叠模型得到了关键的结团-核芯作用势。然后结合库仑波函数边界条件求解了结团-子核相对运动的薛定谔方程,以得到衰变宽度。和我们以往没有考虑子核和结团密度具体分布的计算结果相比,现在得到的结团放射性衰变宽度明显增大。另外,随着结团中心越来越高的密度压低,衰变宽度的计算值会减小。We revisit the cluster emission from trans-lead nuclei within the density dependent cluster model. According to the refined density distribution of daughter and cluster via the available experimental data on nuclear charge radii and neutron skin thickness, the crucial cluster-core potential is constructed by the double-folding model. Then the Schrödinger equation of the cluster-core relative motion is solved along the outgoing Coulomb wave function boundary condition to obtain the decay width. The present decay width of cluster radioactivity is clearly augmented as compared to our previous results without the specific concern of the density distribution of daughter and cluster. Moreover, the computed decay width reduces along with the increasingly depressed density in the cluster center.     

质子放射性寿命的新规律

对球形核和变形核质子放射性的半衰期进行了系统的分析和研究,提出了新的计算质子放射性寿命的解析公式。 通过对公式计算寿命和实验测量值的系统比较,发现两者之间符合得非常好,说明新公式十分准确并具有良好的预言能力。 Systematic calculations on proton radioactivity half lives of both spherical and deformed nuclei are carried out. A new formula with only four parameters is proposed for proton radioactivity half lives. The half lives calculated by using the new formula are in good agreement with the experimental ones. The new formula is simple but accurate, which is very useful for further experiments.     

Proton Radioactivity Within a Hybrid Method

The proton radioactivity half-lives are investigated theoretically within a hybrid method.The potential barriers preventing the emission of protons are determined in the quasimolecular shape path within a generalized liquid drop model (GLDM). The penetrability is calculated with the Wentzel-Kramers-Brillouin (WKB) approximation. The spectroscopic factor has been taken into account in halflife calculation, which is obtained by employing the relativistic mean field (RMF) theory combined with the Bardeen-Cooper-Schrieffer (BCS) method. The half-lives within the present hybrid method reproduced the experimental data very well. Some predictions for proton radioactivity are made for future experiments.     

HIAF高能辐照终端感生放射性

本工作是基于蒙特卡罗模拟软件FLUKA对高能强流重离子加速器（HIAF）高能辐照终端感生放射性进行初步研究。该终端可运行质子最高能量为9.3 GeV,最大流强是1.45×1012 pps（particle per second）。研究内容包括:（1）预测高能辐照终端内活化物质的放射性活度特性;（2）预测不同冷却时间高能辐照终端内残余剂量率分布。研究结果表明,HIAF正常运行时高能辐照终端内的感生放射性主要受束流垃圾桶活化产生的放射性核素影响。当加速器连续运行100天冷却4小时,垃圾桶表面残余剂量率为2.375 mSv·h-1。终端内空气中13N和15O动态饱和比浓度大于其对应的导出空气浓度。冷却水中13N和15O的活度大于对应的ALI_min。该研究是HIAF辐射防护基础研究以及加速器环境影响评价的一项重要内容。The Monte Carlo code FLUKA was used to predict the induced radioactivity of high-energy irradiation terminal of HIAF. The maximum energy of proton is 9.3 GeV, and the maximum current is 1.45×1012 pps (particle per second). In this study we were to predict:(1) the activity properties of activated substances in the experimental terminal; (2) the residual dose rate distribution in the experimental terminal at different cooling time. The results indicate that the induced radioactivity in the high energy irradiation terminal of the HIAF is mainly affected by the radionuclide induced in the beam dump. The residual dose rate on the surface of the beam dump is 2.375 mSv·h-1, after 100 d irradiation and 4 h cooling. The dynamic saturation ratio of 13N and 15O induced in the air inside the terminal is higher than its corresponding derived air concentration. The activity of 13 N and15O induced in cooling water is higher than its ALI_min. This study is a part of radiation protection basic research and environmental impact assessment for HIAF.     

稀土尾矿砂放射性活度的测量与计算分析

准确测量并计算稀土尾矿砂的放射性活度浓度及其变化规律对制定相应的豁免标准和日后的处理处置具有重要的意义。根据选取的特征 射线,分析对比平衡与非平衡状态下铀系、钍系、锕系三个天然衰变系的总活度浓度,结合衰变链的一般动力学方程,计算总放射性活度与每个核素的放射性活度,并研究钍系各核素在平衡被不同程度破坏的情况下随时间的变化规律。结果显示,按照非平衡情况下计算得出的总α 和总β 放射性活度浓度比平衡情况下的更接近实际测量结果,此外,钍系核素在平衡被破坏后的放射性活度随时间变化情况与母体和228Ra 的初始放射性活度浓度有关,若228Ra 小于232Th,则总放射性活度在60 a再次平衡后达到最大值,为10 倍的母体活度;若228Ra 大于232Th,则总放射性活度在3.82 a 出现最大值,为4.57 倍母体活度与5.25 倍第一子体228Ra 的初始活度浓度之和。因此,可知稀土尾矿砂放射性活度已经遭到破坏,其总活度浓度应该采用非平衡情况下的几个特征核素的活度浓度共同计算得到,并且需计算分析其随时间变化出现的最大值,以此来确定是否超过相关法规标准。It is of great significance to measure and calculate rare earth tailing radioactivity for the development of appropriate standards and exemption disposal. The total activity concentration of the three natural decay series (uranium series, thorium series, actinium series) was analyzed under the equilibrium and disequilibrium state according to the selected characteristic  γ-rays. At the same time, we calculated the total activity concentration and the radioactivity for each radionuclide based on the general kinetic equations of decay chain and studied the trend of each radionuclide of thorium-series under different degrees of disequilibrium with time. The results demonstrated that the total radioactivity of and calculated in disequilibrium state was more closed to the actual measurement results compared to that in equilibrium state. In addition, the activity changes with time of thorium series in disequilibrium state are related to the initial activity concentration of the mother nuclide and 228Ra. If the activity concentration of 228Ra is less than that of 232Th, the total activity peak will be 10 times to maternal activity and appear after 60 a when the thorium series become balance again. If the activity concentration of 228Ra is greater than that of 232Th, the maximum total activity will appear in 3.82 a, and will be the sum of 4.57 times of the initial activity concentration of the mother nuclide and 5.25 times of the initial activity concentration of the first daughter 228Ra. Therefore, the rare earth tailings have been in disequilibrium state, and its total activity concentration should be determined based on the activity concentration of several  feature radionuclides. In addition, the maximum value of the activity concentration is profitable to judge whether the activity concentration is fit with relevant regulations and standards.     

HI-13串列加速器辐射防护联锁系统改造

新建HI-13串列加速器辐射防护联锁系统采用PLC自动化控制,增加与优化了原系统的联锁控制逻辑,在充分保证人员辐射安全的同时,使系统状态显示更直观,操作更方便.