Artificial radioelements

The artificial radioelements are listed in Table 14.2. Their number is now 25 and will probably continue to increase in the future. At present, the ratio of radioelements to the total number of known elements is about 30%. 

GltickaufE, Fay JWJ (1936) Direct production of organic compounds containing artificial radioelements. J Chem Soc 1936 390... 

Radiochemistry is defined as the chemical study of radioactive elements, both natural and artificial, and their use in the study of chemical processes (Random House Dictionary, 1984). Operationally, radiochemistry is defined by the activities of radiochemists, that is, (a) nuclear analytical methods, (b) the application of radionuclides in areas outside of chemistry, such as medicine, (c) the physics and chemistry of the radioelements, (d) the physics and chemistry of high-activity-level matter, and (e) radiotracer studies. We have dealt with several of these topics in Chapters 4, 13, 15, and 16. In this chapter, we will discuss the basic principles behind radiochemical techniques and some details of their application. 

Some artificial elements (group c) have probably been produced in the course of the genesis of the elements and were present on the earth at the time of its formation. The age of the earth is estimated to be about 4.5 10 y. During this time elements of shorter half-life disappeared by nuclear transformations. After waiting for about 10 y, most of the artificial elements would have decayed again, and after a much longer time (about 10 y) the radioelements U and Th would also not exist any more on the earth in measurable amounts, with the consequence that the Periodic Table of the elements would end with element 83 (Bi = bismuth). 

The French Atomic Energy Commission (CEA), Valduc Centre, has developed an aerial system of gamma cartography named HELINBUC. This equipment enables, in a few hours, the establishment of a map of radioactivity over areas several dozen to several hundreds of hectares in size, by identifying radioelements present, with a sensitivity between the level of natural radioactivity and that of artificial radioactivity resulting from a large-scale accident. 

Aerial gamma mapping allows us to bring into the evidence, apart from artificial gamma emitters (fission and activation products), the three natural radioelement families, K, U, and Th. 

Klement 43 in the seventh subgroup of the periodic system, technetium, is the lowest atomic number radioelement. Stable, non-radioactive isotopes do not exist according to Mattauch s rule. Technetium isotopes can be produced artificially by nuclear processes. Long-lived isotopes are Tc (2.6 10 a), Tc (4.2 10 a) and Tc (2.1 10- a). The spectroscopic discovery of technetium in several fixed stars provided the first proof of stellar synthesis of heavy nuclides. Traces of Tc occur in the earth s crust where they arise mainly from spontaneous fission of... 

Man has artificially produced radioelements (technetium, promethium, transuranium elements) and also many radioactive isotopes of the naturally occurring elements. Thus, the natural radioactivity on the earth is to some extent increased by man-made radioactive materials. Many analytical research works focus on the determination of manmade radionuclides, their migration, pathways, and accumulation in the environment. The aim of this analytical research work is either to know about fate, pathway, and metabolism of materials or to obtain information about possible environmental protection problems. 

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