Artificial radioactivity production

Atoms with the same value of Zbut different values of A are isotopes (Table 11.1). Many isotopes are stable but others are naturally or artificially radioactive, i.e. their atomic nuclei disintegrate, emitting particles or radiation. This changes the nuclear structure of the atom and often results in the production of a different element. 

Artificial radioactive atoms are produced either as a by-product of fission of uranium or plutonium atoms in a nuclear reactor or by bombarding stable atoms with particles, such as neutrons or protons, directed at... 

Zirconium-95 is the most important of the artificial radioactive isotopes of zirconium. It is placed in pipelines to trace the flow of oil and other fluids as they flow through the pipes. It is also used as a catalyst in petroleum-cracking plants that produce petroleum products from crude oil. 

Symbol Ce atomic number 58 atomic weight 140.115 a rare-earth metal a lanthanide series inner-transition /-block element metaUic radius (alpha form) 1.8247A(CN=12) atomic volume 20.696 cm /mol electronic configuration [Xe]4fi5di6s2 common valence states -i-3 and +4 four stable isotopes Ce-140 and Ce-142 are the two major ones, their percent abundances 88.48% and 11.07%, respectively. Ce—138 (0.25%) and Ce—136(0.193%) are minor isotopes several artificial radioactive isotopes including Ce-144, a major fission product (ti 284.5 days), are known. 

If a product of one of these man-made reactions is unstable and spontaneously disintegrates further, it is said to be "artificially radioactive." In the preceding equation, for example, jjfCo is artificially radioactive, disintegrating as... 

The discovery of artificial radioactivity stimulated a vast amount of experimental work by both physicists and chemists. That this work has been productive is shown by the fact that several hundred artificial... 

One may rightfully raise the question as to why some products of nuclear reactions are radioactive while others are not. The answer concerns the stability of atomic nuclei. Essentially, any radioactive element, whether artificial or natural, can be considered abnormal. A nucleus that undergoes radioactive decay is in an unstable condition, and the process of decay always leads to stable isotopes. This tendency toward the achievement of stability is illustrated by the stepwise decay of naturally radioactive uranium to form a stable isotope of lead and the formation of stable carbon by the decay of artificial radioactive nitrogen. Although the conditions resulting in the instability of atomic nuclei are fairly well understood, further consideration of these factors is beyond the scope of this discussion. 

The fact that uranium is capable of undergoing a process known as fission was discovered as an indirect result of the use of neutrons as projectiles in the production of artificial radioactive isotopes. At the University of Rome, the Italian physicist Enrico Fermi bombarded many different elements with neutrons and thereby produced many new radioactive isotopes. The use of neutrons as projectiles has the distinct advantage that the collision of these uncharged particles with... 

Sometimes the nucleus can be changed by bombarding it with another type of particle. This is referred to as induced radioactivity. In 1934, Irene Curie, the daughter of Pierre and Marie Curie, and her husband, Frederic Joliot, announced the first synthesis of an artificial radioactive isotope. They bombarded a thin piece of aluminum foil with ot-particles produced by the decay of polonium and found that the aluminum target became radioactive. Chemical analysis showed that the product of this reaction was an isotope of phosphorus. 

These heavy elements, which are naturally radioactive, are less interesting in chemical kinetics than the light elements which are involved in the majority of chemical reactions. The use of light elements has been made possible through the production of artificial radioactivity and through the finding of practical means of concentrating isotopes to such an extent that their concentrations can be determined by means of density measurements. Extraordinary refinements in these measurements have been a necessary part of these developments. 

The nucleus is stable, so that this nuclear reaction does not lead to the production of artificial radioactivity. Many other eleuicnts, hotsever, undergo similar reactions with the production of unstable nuclei, which then undergo radioactive decomposition. 

By the third decade of the twentieth century, the emitted radioactivity from artificially synthesized tritium (3H) and carbon-14 (14C) was used to follow biochemical reactions. Glucose, amino acids, and other chemical compounds were synthesized with 3H or 14C incorporated either randomly or at some known position in the molecule. The radioactive products derived from radiolabeled glucose or amino acids added to cells, tissue slices, or a whole organism identified the metabolic fate of these molecules under defined... 

Equations [5.3] and [5.4] can be applied in the case of relatively simple and sensitive radioactivity measurements. The use of long-lived artificial fission products in intervals without nuclear tests seemed particularly suitable in the past since they have a relatively constant vertical distribution in the troposphere (e.g. Ishii, 1960) which facilitates the determination of H. In this way Small (1960), by using total -activity measurements, calculated that the overall dry deposition velocity of aerosol particles over Norway is 0.50 km day-1. On the other hand, Stewart found (see Small, 1960) a much smaller value in England. According to artificial / -activity measurements of E. Meszarosand Simon (1967), carried out near... 

In forming artificial radioactive isotopes, problems of isolation are often encountered. For example, a product may decay quickly with the result that the initial product is contaminated with the daughter nuclide. 

In 1934 Frederic Joliot and Irene Curie discovered artificial radioactivity. This discovery was soon followed by the discovery of fission and the enormous amounts of energy released by this process. However, few in the then limited community of scientists working with radioactivity believed that it would be possible within a fairly near future to establish enough resources to develop the fission process for commercial production of energy or even think about the development of mass-destruction weapons. 

The stable 1 isotope constitutes 100% of naturally occurring iodine. However, a number of artificial, radioactive isotopes are formed as by-products of nuclear fission pathways (Figure 8.6). Of these, 1 is the most insidious in the biogeochemical cycle (via its transport in the atmosphere) due to its subsequent assimilation in the thyroid gland and relatively short half life of 8 days. 

Cesium 137 is an artificial radionuclide used in clinical, industrial, and research applications and one of the main radioactive products of fission reactions taking place in nuclear reactors. The possibility that the anomalous radioactivity derived from active nuclear plants can be rule out as the i Cs was not accompanied by the other radionuclides produced during fission. Towards the end of April 1998, an incident occurred at the Algeciras steel works in southern Spain with emissions of Cs coming from a radioactive source no longer in use. This source ended up in the foundry. The fact that the presence of Cs was interrupted for a week and then resumed is not unusual as the transport and soil deposition of air-dispersed pollutants is strictly linked to wind and precipitation. The levels of radioactivity were negligible and many times below every alarm threshold, but the bee matrix promptly revealed the presence, albeit minimal, of Cs... 

Pierre and Marie Curie with their daughter, Irene. Irene grew up to continue the study of radioactivity with her husband, Frederic JoUoL Together, Irene and Frederic won a Nobel Prize in 1935 for production of the first artificial radioactive isotope. 

Meat Products. Pharmaceutical Analysis Overview. Radiochemical Methods Overview Natural and Artificial Radioactivity Radionuclide Monitoring Radon Radiotracers Gamma-Ray Spectrometry. Water Analysis Freshwater Seawater-Organic Compounds Seawater-Inorganic Compounds. 

Element 85 was synthesized by D. Corson, C. Mackenzie, and E. Segre who worked at Berkley (USA). The Italian physicist Segre by that time had settled in the USA and was the only one in the group who had an experience in artificial synthesis of a new element (technetium). On July 16, 1940, these scientists submitted to the prestigious physical journal Physical Review a large paper entitled Artificial radioactive element 85 . They reported how they had bombarded a bismuth target with alpha particles accelerated in a cyclotron and obtained a radioactive product of the nuclear... 

Corson DR, MacKenzie KR, Segre E (1940b) Artificially radioactive element 85. Phys Rev 58 672 Coryell CD, Sugarman N (eds) (1951) Radiochemical studies the fission products, vol 1-3. McGraw-Hill, New York... 

Fermi E (1934b) Possible production of elements of atomic number higher than 92. Nature 133 898 Fermi E, Amaldi E, D Agostino O et al (1934) Artificial radioactivity produced by neutron bombardment. Proc Roy Soc A (Lond) 146 483 Fermi E, Rasetti F (1935) Ricerche sui neutroni lenti. Nuovo Cimento 12 201... 

The development of the cyclotron and, later, the fission reactor gave the means for a variety of artificial transmutations, but it often was difficult to identify the element and mass number of a radioactive product. In many cases, individual radionuclides could be characterized only by simple features, such as half-life or attenuation of radiations in absorbers, which did not allow discriminating the components of a complex mixture. Chemical evidence was required in order to make definite identification with a particular element. 

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