Radioactivity, basic principles

The abundance of a trace element is often too small to be accurately quantihed using conventional analytical methods such as ion chromatography or mass spectrometry. It is possible, however, to precisely determine very low concentrations of a constituent by measuring its radioactive decay properties. In order to understand how U-Th series radionuclides can provide such low-level tracer information, a brief review of the basic principles of radioactive decay and the application of these radionuclides as geochronological tools is useful. " The U-Th decay series together consist of 36 radionuclides that are isotopes (same atomic number, Z, different atomic mass, M) of 10 distinct elements (Figure 1). Some of these are very short-lived (tj j 1 -nd are thus not directly useful as marine tracers. It is the other radioisotopes with half-lives greater than 1 day that are most useful and are the focus of this chapter. 

Powsncr, E.R. (1994) Basic principles of radioactivity and its measurement. In Tietz Textbook of Clinical Chemistry (C.A. Burtis, and E.R. Ashwood, eds.), pp. 256-282. Saunders, Pennsylvania, Philadelphia. 

The principle of supercritical wet oxidation can be applied to several areas, including municipal waste treatment, chemical waste treatment, polymeric waste treatment, and the treatment of mildly radioactive waste. Since the basic principle of wet oxidation involves the rapid oxidation of organic material, any substance which is mildly oxidative can be subjected to this process. With such high temperature operation, the remaining fraction of inorganic material can be simply precipitated as a salt and then easily collected from the bottom of the oxidation vessel. 

Radioactive waste management is a quite mature field of application of basic geoscientific disciplines. As we will discuss in forthcoming sections, the long-term performance and henceforth the safety of radioactive waste disposal systems, deeply relies on the basic principles that control the release, mobility, and transport of the chemical elements in the geosphere. In the context of radioactive waste disposal, the waste matrix constitutes the innermost of the barriers that may control the release and ulterior transport of radionuclides through the ground-water systems. 

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. 

All absolute dating methods that have proven dependable are based on radioactive decay. Virtually all of the methods depend on the methodical decrease in the amount of the radioactive nuclide and the growth of the corresponding daughter product. The one exception is in the area of radiation-induced damage in solids, which is the basis of thermoluminescence or ESR dating. This latter scheme will be dealt with later in the chapter. Here the basic principles of canonical radioactive geochronometry as applied to marine deposits is reviewed. 

To reliably perform qualitative and quantitative analyses on body fluids and tissue, the clinical laboratorian must understand the basic principles and procedures that affect the analytical process and operation of the clinical laboratory. These include the knowledge of (1) the concept of solute and solvent, (2) units of measurement, (3) chemicals and reference materials, (4) basic techniques, such as volumetric sampling and dispensing, centrifugation, measurement of radioactivity, gravimetry, thermometry, buffer solution, and processing of solutions, and (5) safety. ... 

With the development of radioimmunoassays (RIAs) in the 1960s that used radioactive isotopes as labels (see Chapter 9), the measurement of radioactivity became a common and important practice in clinical laboratories. However, concerns about, and problems with, the safe handhng and disposal of radioactive reagents and waste have led to the development of immunoassays that use nonisotopic labels (see Chapter 9). The rapid acceptance and extensive use of nonisotopic immunoassays by the clinical laboratory have resulted in a decreased use of RIA and ultimately a decreased requirement for them to measure radioactivity. Because of this deemphasis on the necessity to measure radioactivity, only a brief discussion of the topic is presented here. Readers requiring more detail on this topic are referred to the chapter entitled Basic Principles of Radioactivity and Its Measurement that is included in a prior edition of this textbook, ... 

Powsner ER, Widman JC. Basic Principles of Radioactivity and Its Measurement. In Burtis CA, Ashwood ER, eds. Tietz textbook of clinical chemistry, ed. Philadelphia W B Saunders, 1999 113-132. 

The aim of this chapter is to illustrate the similarities and differences between the behavior of metallic radionuclides and other metals in soil systems. We summarize some basic principles to show the hazards associated with radionuclides, give a brief inventory of the metals that may exist in soil systems, and give a concise description of the behavior of some of the more common and most widely studied radioactive metals. 

A comprehensive description of the nature of radioactivity and its interaction with matter is beyond the scope of this chapter, and such information can easily be found elsewhere (Shleien et al., 1998 CPEP, 2003 Tykva, 2004). Here we give only a brief sketch of the basic principles. Radioactivity is a natural phenomenon, discovered in 1896 by Henri Becquerel. The nuclei of some atoms are unstable and decay spontaneously, emitting ionizing radiation to attain a more energetically favorable state. Radioisotopes are characterized by the nature of the... 

Gray, Harry B., John D. Simon, and William C. Trogler. Braving the Elements. Sausalito, Calif. University Science Books, 1995. This book is an introduction to the basic principles of chemistry, with elementary explanations of radioactive decay, chemical bonding, oxidation-reduction reactions, and acid-base chemistry. Practical applications of specific chemical compounds and classes of compounds are presented. 

Microbalances used to be very tridqr instruments and only very skilled workers could hope to obtain reproducible results. The basic principle of most types is the torsion of a fiber (steel or quartz), its deflection being read with special optics. Cefola (C5) described a fish-pole balance which has been used in the isolation of plutonium. (A great number of ultramicro techniques now generally known originate from research on radioactive chemicals.) The development of these balances and the use of new principles (electric balances) bring the possibility of accurate weighing to the level of the laboratory technician. 

In 1903, with the scientist Frederick Soddy, Rutherford concluded that radiation was caused by atoms of radioactive material breaking apart. The tiny bits that broke off were the a and (3 rays. This was a revolutionary idea, since it had been a basic principle of physics and chemistry that atoms were the smallest possible particles of matter and therefore indivisible. Rutherford went on to demonstrate that a-particles were, in fact, a form of the helium atom. He did this by placing a delicate glass bulb containing radon gas, which emitted a-particles, in an evacuated tube. The particles would penetrate the glass of the bulb but not escape the tube, and could then be analyzed. 

Three basic principles are recommended for keeping radiation exposure to a minimum shielding, control, and distance. If a radiochemical laboratory is designed properly and the work performed in such a manner that the g eral background contamination is suffici tly low to do valid low level tracer experiments, then the health aspects of radiation control are satisfied. We indicate the main principles for work with radioactive substances, but in each notion, special rules may apply. 

Radiation safety of handling radioactive fissile substances is ensured by observing the basic principles specified in radiation safety standards, which cover standardization, substantiation, and optimization. 

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