Gamma radioactivity

Figure 24.34 shows the position of two workers near a radioactive gamma source. The worker at Position A is standing 2.5 m from the source and receives an exposure of 0.98 mrem/s m. The worker at Position B receives an exposure of 0.50 mrem/s m. What is the distance of the worker at Position B from the source ... 

Gamma radiation is one of the three types of natural source of radioactivity. Gamma rays are electromagnetic radiation, like X-rays, and the other two types of natural radioactivity are alpha and beta radiation, which are in the form of particles. Gamma rays are the most energetic... 

Grasso, A., and Senni, M.-I., 1979. A toxin purified from the venom of the black widow spider affects the uptake and release of radioactive gamma-amino butyrate and N-epinephrine from rat brain synap-tosomes, Eur.J.Biochem. 102 337-344. 

If an intensifier, such as the 85 mm presented here, is now replacing the screen, a relative gain of the order of x50 is obtained which results in a conversion factor of 1 to 7.5 (1 incident X photon --> 7.5 electrons). This conversion efficiency not only resolves the quantum sink problem but also increases the light level significantly to compensate for the low gamma fluxes obtained from radioactive sources. 

To find the radioactive and nuclide sources Dosimeters, radiometers, gamma-signaling devices, spectrometers... 

In situ measurement of the concentration of radioactive tracers in the different phases requires that the phases are separated and arranged according to density difference over the measurement cross section in a horizontal pipe. In general, the measurements are performed with two spectral gamma radiation detectors placed on top and bottom of the pipe respectively. 

Natural titanium is reported to become very radioactive after bombardment with deuterons. The emitted radiations are mostly positrons and hard gamma rays. The metal is dimorphic. The hexagonal alpha form changes to the cubic beta form very slowly at about 88O0C. The metal combines with oxygen at red heat, and with chlorine at 550oC. 

The most important types of radioactive particles are alpha particles, beta particles, gamma rays, and X-rays. An alpha particle, which is symbolized as a, is equivalent to a helium nucleus, fHe. Thus, emission of an alpha particle results in a new isotope whose atomic number and atomic mass number are, respectively, 2 and 4 less than that for the unstable parent isotope. 

Neutron Activation Analysis Few samples of interest are naturally radioactive. For many elements, however, radioactivity may be induced by irradiating the sample with neutrons in a process called neutron activation analysis (NAA). The radioactive element formed by neutron activation decays to a stable isotope by emitting gamma rays and, if necessary, other nuclear particles. The rate of gamma-ray emission is proportional to the analyte s initial concentration in the sample. For example, when a sample containing nonradioactive 13AI is placed in a nuclear reactor and irradiated with neutrons, the following nuclear reaction results. 

The radioactive isotope of 13AI has a characteristic decay process that includes the release of a beta particle and a gamma ray. 

With the exception of diamond coloring and the turning of topa2 blue, the source of the irradiation is immaterial. Gamma rays are the preferred source because of uniformity of coloration and the absence of heating and induced radioactivity. The most commonly seen gemstones enhanced by irradiation are summari2ed in Table 4. 

Radiometric ore sorting has been used successfully for some uranium ores because uranium minerals emit gamma rays which may be detected by a scintillation counter (2). In this appHcation, the distribution of uranium is such that a large fraction of the ore containing less than some specified cut-off grade can be discarded with tittle loss of uranium values. Radioactivity can also be induced in certain minerals, eg, boron and beryllium ores, by bombarding with neutrons or gamma rays. 

Radioactivity occurs naturally in earth minerals containing uranium and thorium. It also results from two principal processes arising from bombardment of atomic nuclei by particles such as neutrons, ie, activation and fission. Activation involves the absorption of a neutron by a stable nucleus to form an unstable nucleus. An example is the neutron reaction of a neutron and cobalt-59 to yield cobalt-60 [10198 0-0] Co, a 5.26-yr half-life gamma-ray emitter. Another is the absorption of a neutron by uranium-238 [24678-82-8] to produce plutonium-239 [15117 8-5], Pu, as occurs in the fuel of a nuclear... 

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