Radioisotope sources

Isotope Primary Decay Mode Half-Life (Years) Useful Photon Energies Emitted % Theoretical Yield (Photons per 100 Decay Transformaticns) Typical Activity (mCi) 

Source Table from Jenkins, R. et al Quantitative X-Ray Spectrometry, Marcel Dekker, Inc., New York, 1981. Used with permission. 

X-radiation is a product of radioactive decay of certain isotopes. The term gamma ray is often used for an X-ray resulting from such a decay process. Alpha and beta decay and electron capture (EC) processes can result in the release of gamma rays. Table 8.4 lists some common radioisotopes used as XRF sources. 

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In the examination of works of art on paper, the variations in density are often too small to be revealed by conventional x-radiography. Instead, much benefit has been derived from beta-radiography, where the P-radiation is provided by an extended radioisotope source, typically a sheet of plastic in... 

For pipelines in service in chemical plants, it is not usually convenient to place a radiation source inside the pipe and position it to irradiate each welded joint. The radioisotope source container maybe placed on the outer surface of the pipe. The radiation beams then pass through two pipe wall thicknesses to expose films placed diametrically opposite the radiation source, also on the outside of the pipe wall. Other methods, such as magnetic particle inspection of welds in steel pipe, or ultrasonic inspection of welds in pipes of all materials, supplement x-rays in many critical appHcations. The ultrasonic tests can often detect the thin, laminar discontinuities parallel to the pipe surface or the incomplete fusion discontinuities along the weld... 

There are three options for remote repair of composite structures using electron curing a portable accelerator. X-rays generated from such an accelerator and radioisotopic sources, such as Co . 

The principal mechanism for analyte response is ionization due to collision with metastable helium atoms. Hetastable helium atoms are generated by multiple collisions with beta electrons from the radioisotopic source. Since the ionization potential of helium (19.8 ev) is higher than that of all other species except neon, then all species entering the ionization chamber will be ionized. 

Recently, miniaturized, x-ray tubes have largely replaced previously used radioisotope sources for most applications as these provide higher x-ray fluxes, shorter count times, and better precision. 

Figure 13.6—Schematic of a cooled Si Li detector. The high quantum yield of this detector allows the use of primary X-ray sources of low power (a few watts or a radioisotope source).

As illustrated in Fig, 5, a radioisotope source is placed on one side of a pipeline while a detector is placed on the opposite side. Transmitted... 

Radiation from radioisotope sources can be used to excite characteristic X-rays in samples upon which the beam of radiation is directed. Detection and analysis of these X-rays yield information about the composition of the sample. This opens the field of analytical applications of X-ray fluorescence analysis. The most frequent applications are in the ore processing and the metal coating industries. 

Radioisotopes as a source of radiation offer the advantage that they do not require electrical power so that they can be used readily in the field. Different sources are available as well, ranging from low to high energy. The small size of radioisotope sources allows inspection of parts or machinery which could not be examined by X-ray tubes. 

X-ray sources X-ray fluorescence analysis is a technique for elemental identification and quantification. X-ray fluorescence sources provide stable outputs for energy, direction and intensity. Unlike competing technologies, radioisotope sources do not require external power supplied. 

Common radioisotope sources of alpha particles are listed in Table 5.6. All but the first one listed are members of radioactive decay chains. Decay chains are classified into four groups according to their mass numbers. They are Th-series whose mass number is 4N (N is integer), U-series of 4N+2, Ac-series of 4N+3 and Np-series of 4N-fl. An Np-series does not exist naturally because the half-life of its longest-lived member is... 

Medical Uses of Radioisotopes Nonmedical Uses of Radioisotopes Sources of Radioisotopes Problems Associated with Radioactivity MiniLab 21.2 Radon—A problem in your home ... 

To induce X-ray fluorescence of elements in a sample, a source of photons or particles of sufficient energy is required. Generally these sources are produced by X-ray tubes of variable power or, for portable instruments, by radioisotopic sources. If the term of X-ray fluorescence is considered in the broadest sense of X-ray emission, other excitation processes employing particles (e , a) can be used. 

Table 2.4 Properties of selected nuclei observed by Mossbauer spectroscopy. The radioisotope source provides the y-radiation required for the Mossbauer effect.

Nucleus observed Natural abundance / % Ground spin state Excited spin state Radioisotope source ... 

Example 2.10 A radiation detector is used to count the particles emitted by a radioisotopic source. If it is known that the average counting rate is 20 counts/ min, what is the probability that the next trial will give 18 counts/min ... 

For many nuclei, more than one mode of decay is positive. Users of radioisotopic sources need information about particles emitted, energies, and probabilities of emission. Many books on atomic and nuclear physics contain such information, and the most comprehensive collection of data on this subject can be found in the Table of Isotopes by Lederer and Shirley." Figure 3.12 shows an example of a complex decay scheme taken from that book. 

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