Group radioactive nuclides

The first of these equations shows that the result of the nuclear reaction in which aluminum is bombarded with or-partides is the emission of a neutron and the production of a radioactive isotope of phosphorus. The second equation shows the radioactive disintegrations of the latter to yield a stable silicon atom and a positron. Continuation of this line of investigation by several research groups confirmed that radioactive nuclides are formed m many nuclear reactions. 

The third principal component of environmental radioactivity is that due to the activities of humans, the anthropogenic radionuclides. This group of nuclides includes the previously discussed cases of 3H and 14C along with the fission products and the transuranium elements. The primary sources of these nuclides are nuclear weapons tests and nuclear power plant accidents. These events and the gross nuclide releases associated with them are shown in Table 3.1. Except for 14C and... 

The nuclides of each modular group are spread along 11 festoons that terminate in a radioactive nuclide at each end. Nuclides on the high-ratio side decay by positron emission or electron capture those on the low-ratio side by /3-emission. All nuclides with A > 209 decay by cr-emission. The 81 naturally stable elements have, on average, 3 isotopes each. The predicted 100 elements on the cosmic scale, by the same reckoning, correspond to 300 isotopes. 

Alpha-particle production a common mode of decay for radioactive nuclides in which the mass number changes. (21.1) Amine an organic base derived from ammonia in which one or more of the hydrogen atoms are replaced by organic groups. (7.6 22.4)... 

Some radioactive nuclides are especially damaging because they tend to concentrate in particular parts of the body. For example, because both strontium and calcium are alkaline earth metals in group 2 on the periodic table, they combine with other elements in similar ways. Therefore, if radioactive strontium-90 is ingested, it concentrates in the bones in substances that would normally contain calcium. This can lead to bone cancer or leukemia. For similar reasons, radioactive cesium-137 can enter the cells of the body in place of its fellow alkali metal potassium, leading to tissue damage. Non-radioactive iodine and radioactive iodine-131 are both absorbed by thyroid glands. Because iodine-131 is one of the radioactive nuclides produced in nuclear power plants, the... 

The principal among radioactive materials are the following isotopes °Co, °Sr, °Y, ° Ru, Cs, Ce, Pm, 238,239,240py Ra, and so on. The groups of toxic radioactive elements are presented in Table 5.1. Approximately 95% of radioactive pollutants are concentrated in the upper soil layer. Individual radioactive nucUdes are present in the soil in different forms. Depending on the soil composition, 8%-30% of radioactive nuclides are present in exchange forms, 2%-10% of them are in water-soluble forms, and 60%-85% in tightly bounded forms (Table 5.2). 

Figure 5.4 The 264 non-radioactive nuclides, which occur as 11 groups of 24, are plotted in a field defined hy the axes x = Z and y = Z/N. The straight hemlines that separate the groups of 24 are those shown in plot (a). Reflection of this pattern in the symmetry line at Z = 51 generates diagram (h)...

The sources of ionizing radiation used for research or industrial irradiation purposes can be divided into two groups sources containing radionuclides, such as Co, Cs, or the Sr— pair, and machine sources of radiation, such as X-ray equipment or electron accelerators. Without going into details, this chapter will briefly mention those characteristics of some of the radioactive nuclides and accelerators, which are important from the point of view of using them for irradiation purposes. 

A wide range of radioactive nuclides ( Table 59.4) may be employed for RTGs as power sources. According to the fabrication method, they may be divided into four groups (Radioizotopnye istochniki elektricheskoy energii 1978, Mashinostroyenie Entsiklopediya) ... 

Nuclear wastes are the most readily available and cheapest raw materials for the production of radioactive nuclides in large amounts. The nuclides Po and Co of the second group are the most advanced ones both in their production method and in their properties. The production... 

The biological hazards associated with a homogeneous reactor are due chiefly to the radioactive rare earths, alkaline earths, and iodine [2]. The importance, as a biological hazard, of any one of these groups or nuclides within the group depends on assumptions made in describing exposure conditions however, contributes a major fraction of the radiation hazards for any set of conditions. While the accumulation of hazardous materials such as rare earths and alkaline earths will be controlled by the processing methods to be described, less is known about the chemistry of... 

Since the radioactive half-lives of the known transuranium elements and their resistance to spontaneous fission decrease with increase in atomic number, the outlook for the synthesis of further elements might appear increasingly bleak. However, theoretical calculations of nuclear stabilities, based on the concept of closed nucleon shells (p. 13) suggest the existence of an island of stability around Z= 114 and N= 184. Attention has therefore been directed towards the synthesis of element 114 (a congenor of Pb in Group 14 and adjacent superheavy elements, by bombardment of heavy nuclides with a wide range of heavy ions, but so far without success. 

If a nuclide of an element in Group IA (alkali metals) of the periodic table undergoes radioactive decay by emitting positrons, what is the chemical nature of the resulting element ... 

Effect of Concentration. To predict the amounts of radioactive or stable nuclides of an element that may be accumulated when increased quantities are present in the water, we must know if the concentration of the stable nuclide is under metabolic control. To test for a homeostatic mechanism for Zn and Mn in oysters and for Co and Cs in clams, groups of oysters and clams were exposed to increased concentrations of these elements in an attempt to saturate any regulatory mechanisms. 

About 2800 nuclides are known. About 340 of these are found in nature and may be subdivided into four groups (1) 258 are indisputably stable. (2) For 25 nuclides with atomic numbers Z < 80 radioactive decay has been reported, but not confirmed for 7 of these. Many exhibit extremely long half-lives (9 nuclides >10 y and 4 nuclides >10 y), and radioactivity has not been proved unambiguously. Some have later be reported to be stable, and the 15 nuclides with half-lives >10 y may be considered to be quasistable. (3) Main sources of natural radioactivity comprising 46 nuclides are and Th and their radioactive decay products. (4)... 

All nuclides with Z > 83 are unstable. Bismuth-209 is the heaviest stable nuclide. Therefore, the largest members of Groups 1A(1), 2A(2), 4A(14), 6A(16), 7A(17), and 8A(18) are radioactive, as are all the actinides (the 5/inner-transition elements) and the elements of the fourth rf-block transition series (Period 7). 

The nucleus would thus seem to consist of independrat substructures of neutrons and protons, with each type of nucleon paired off as far as possible. Further, the nucleons obviously grouped together in the magic numbers. From the decay of radioactive nuclei we know that the total decay energy (Q-value) of any particular nuclide has a definite value. Moreover, y-emission from any particular nucleus involves discrete, definite values. These facts resemble the quantized emission of electromagnetic radiation (X-ray, UV, visible light. 

As part of this experiment, a series of honey bee samples was collected from colonies located at the LANL study site near the radioactive lagoon, and analyzed for concentrations of radionuclides (gamma-emitting nuclides, uranium, and tritium). There were two groups of colonies used in the experiment. One group had been located at the study site for 4 months, the other group for several years. A detailed description of this experiment is described in Haarmann [22]. Table 8.1 shows an example of the data that were collected as part of this study. 

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