Radioactive isotope producing

For many of the analytical techniques discussed below, it is necessary to have a source of X-rays. There are three ways in which X-rays can be produced in an X-ray tube, by using a radioactive source, or by the use of synchrotron radiation (see Section 12.6). Radioactive sources consist of a radioactive element or compound which spontaneously produces X-rays of fixed energy, depending on the decay process characteristic of the radioactive material (see Section 10.3). Nuclear processes such as electron capture can result in X-ray (or y ray) emission. Thus many radioactive isotopes produce electromagnetic radiation in the X-ray region of the spectrum, for example 3He, 241Am, and 57Co. These sources tend to produce pure X-ray spectra (without the continuous radiation), but are of low intensity. They can be used as a source in portable X-ray devices, but can be hazardous to handle because they cannot be switched off. In contrast, synchrotron radiation provides an... 

Natural radioactive isotopes produced by cosmic rays (14C, 32Si, 226Re) are used in determining the mixing and circulation of ocean water (Kharkar et al., 1963 Somayajulli et al., 1973 Broecker et al., 1967 Lai, 1966 Craig, 1969), while 3H and 14C have extensive applications in hydrogeology. 

A number of radioactive isotopes produced primarily by cosmic ray interactions in the upper atmosphere, especially (Clark and Fritz, 1997 Mazor, 1997), C1 (Andrews etal., 1994 Phillips, 2000), and (Moran et al., 1995 Fabryka-Martin, 2000), as well as dissolved " He (Torgersen and Clarke, 1985 Solomon, 2000), have been used, in conjunction with data for the stable isotopes and calculated flow rates, for determining the age of natural waters, including fluids in sedimentary basins (Bethke et al., 1999, 2000). The 5.73 ka half-life of " C at 5.73 ka is so short that it is useful only for dating basinal meteoric water younger than —40 ka. C1 (ti/2 = 0.301 Ma) is useful for dating water of up to —2 Ma in age. These isotopic systems are reviewed by Phillips and Castro (see Chapter 5.15). 

The study of electron transfer reactions began in earnest when radioactive isotopes, produced for nuclear research and the atom bomb program during World War II, became accessible. Glen Seaborg, in a 1940 review of artificial radioactivity, noted the first attempt to measure the self-exchange reaction between aqueous iron(III) and iron(II), equation (1.9).1"... 

The isotopes are arranged in each case where known in the order of frequency of occurrence the radioactive isotopes are indicated by an asterisk. Radioactive isotopes produced artificially are not included. 

The sol-gel process has been used to produce high purity YAS glass spheres. The radioactive isotope produced when the YAS glass spheres are irradiated is a P emitter with a half-life of 64.1 hours. The average penetration of P-particles (electrons) in human tissue is 2.5 mm (maximum pen-... 

One of the uses of neutronic reactors is to irradiate materials with neutrons and other particles and radiations. In this manner, radioactive isotopes may be produced for all chemical elements with the exception of helium. The physical transformation of elements as a result of irradiation in a neutronic reactor may be ac- complisbed through any one of a number of reactions which are fully described in the published literature. Radioactive isotopes produced by neutronic reactors are receiving large commercial interest, particularly such isotopes as H, P32, 35, and 1 As a result, there is a... 

Autoradiography is based on the fact that electrons emitted by the decay of a radioactive isotope produce images on sensitive photographic emulsions. The scientific value of an autoradiogram depends on various conditions ... 

Radon occurs only in trace amounts, its longest-lived isotope being Rn. It is produced by the a-decay of Ra, which is itself just one of the radioactive isotopes produced in the chain of decay processes by which is transformed into Pb. The Rn is itself a-active ... 

About 20 kg of scandium (as SC2O3) are now being used yearly in the U.S. to produce high-intensity lights, and the radioactive isotope 46Sc is used as a tracing agent in refinery crackers for crude oil, etc. 

Few of the naturally occurring elements have significant amounts of radioactive isotopes, but there are many artificially produced radioactive species. Mass spectrometry can measure both radioactive and nonradioactive isotope ratios, but there are health and safety issues for the radioactive ones. However, modem isotope instmments are becoming so sensitive that only very small amounts of sample are needed. Where radioactive isotopes are a serious issue, the radioactive hazards can be minimized by using special inlet systems and ion pumps in place of rotary pumps for maintaining a vacuum. For example, mass spectrometry is now used in the analysis of Pu/ Pu ratios. 

It is not necessary that there be two isotopes in both the sample and the spike. One isotope in the sample needs to be measured, but the spike can have one isotope of the same element that has been produced artificially. The latter is often a long-lived radioisotope. For example, and are radioactive and all occur naturally. The radioactive isotope does not occur naturally but is made artificially by irradiation of Th with neutrons. Since it is commercially available, this last isotope is often used as a spike for isotope-dilution analysis of natural uranium materials by comparison with the most abundant isotope ( U). 

Each of the elements has a number of isotopes (2,4), all radioactive and some of which can be obtained in isotopicaHy pure form. More than 200 in number and mosdy synthetic in origin, they are produced by neutron or charged-particle induced transmutations (2,4). The known radioactive isotopes are distributed among the 15 elements approximately as follows actinium and thorium, 25 each protactinium, 20 uranium, neptunium, plutonium, americium, curium, californium, einsteinium, and fermium, 15 each herkelium, mendelevium, nobehum, and lawrencium, 10 each. There is frequently a need for values to be assigned for the atomic weights of the actinide elements. Any precise experimental work would require a value for the isotope or isotopic mixture being used, but where there is a purely formal demand for atomic weights, mass numbers that are chosen on the basis of half-life and availabiUty have customarily been used. A Hst of these is provided in Table 1. 

Any radioactive nucUde or isotope of an element can be used as a radioactive tracer, eg, chromium-51 [14392-02-0] cobalt-60 [10198-40-0] tin-110 [15700-33-1] and mercury-203 [13982-78-0],hut the preponderance ofuse has been for carbon-14 [14762-75-5],hydj ogen-3 [10028-17-8] (tritium), sulfur-35 [15117-53-0], phosphoms-32, and iodine-125 [14158-31 -7]. More recendy phosphoms-33 has become available and is used to replace sulfur-35 and phosphoms-32 in many appUcations. By far the greater number of radioactive tracers produced are based on carbon-14 and hydrogen-3 because carbon and hydrogen exist in a large majority of the known natural and synthetic chemical compounds. 

Types of Dia.gnostic Isotopes. Isotopes used in nuclear medicine may be characterized by the source used to produce the radioactive isotope, by whether the isotopes are produced at a central location and shipped or at the clinic, or by the type of emission and thus the equipment used to detect them. The first of these, the sources, are summarized in Table 2. Some isotopes may be produced by more than one method. 

The selective uptake of iodide ion by the thyroid gland is the basis of radioiodine treatment in hyperthyroidism, mainly with although various other radioactive isotopes ate also used (40,41). With a half-life of eight days, the decay of this isotope produces high energy P-particles which cause selective destmction within a 2 mm sphere of their origin. The y-rays also emitted are not absorbed by the thyroid tissue and are employed for external scanning. 

Clathrates provide a means of storing noble gases and of handling the various radioactive isotopes of Kr and Xe which are produced in nuclear reactors. 

In 1934 Fermi decided to bombard uranium with neutrons in an attempt to produce transuranic elements, that is, elements beyond uranium, which is number 92 in the periodic table. He thought for a while that he had succeeded, since unstable atoms were produced that did not seem to correspond to any known radioactive isotope. I le was wrong in this conjecture, but the research itself would eventually turn out to be of momentous importance both for physics and for world history, and worthy of the 1938 Nobel Pri2e in Physics. 

Smoke detector. Most smoke detectors use a tiny amount of a radioactive isotope to produce a current flow that drops off sharply in the presence of smoke particles, emitting an alarm in the process. 

The radioactive isotope tritium, 3H, is produced in nature in much the same way as 1fC. Its half-life is 12.3 years. Estimate the 3H ratio of the tritium of water in the area to the tritium in a bottle of vine claimed to be 25 years old. 

For the purposes of analytical chemistry, four kinds of monochromatic beams need to be considered. (The quotation marks are to remind the reader that the beams under discussion are not always truly monochromatic.) Three kinds of beams—those produced by Bragg reflection (4.9), filtered beams (4.6), beams in which characteristic lines predominate over a background that can be neglected— will be discussed later ( 6.2). The fourth kind of beam contains monochromatic x-rays that are a by-product of our atomic age and that promise to grow in importance they are given off by radioactive isotopes. These x-rays must not be confused with 7-rays (11.1), which also originate from radioactive atoms but which differ from x-rays because the transformation that leads to radiation involves the nucleus. 

The discoveries of Becquerel, Curie, and Rutherford and Rutherford s later development of the nuclear model of the atom (Section B) showed that radioactivity is produced by nuclear decay, the partial breakup of a nucleus. The change in the composition of a nucleus is called a nuclear reaction. Recall from Section B that nuclei are composed of protons and neutrons that are collectively called nucleons a specific nucleus with a given atomic number and mass number is called a nuclide. Thus, H, 2H, and lhO are three different nuclides the first two being isotopes of the same element. Nuclei that change their structure spontaneously and emit radiation are called radioactive. Often the result is a different nuclide. 

Casas M, Garcias F, Serra L, et al. 1992. Analysis for metal elements and radioactive isotopes in fly ash produced in lignite combustion at a thermal power plant. J Environ Sci Health Part A 27(2) 419-432. 

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