Nuclear charge reactors using

This was the first man-made radionuclide. From that time on many species of radionuclides were produced by bombardment of elements with charged particles using the various types of accelerators. In addition, practical use of fission energy allowed production of a great amount of artificial radionuclides, not only by neutron irradiation generated with nuclear reactors, but also by processing spent fuel. 

All the techniques discussed here involve the atomic nucleus. Three use neutrons, generated either in nuclear reactors or very high energy proton ajccelerators (spallation sources), as the probe beam. They are Neutron Diffraction, Neutron Reflectivity, NR, and Neutron Activation Analysis, NAA. The fourth. Nuclear Reaction Analysis, NRA, uses charged particles from an ion accelerator to produce nuclear reactions. The nature and energy of the resulting products identify the atoms present. Since NRA is performed in RBS apparatus, it could have been included in Chapter 9. We include it here instead because nuclear reactions are involved. 

Neutron depth profiling technique (NDP) [13]. NDP is a speeial method for depth profiling of few light elements, namely He, Li, B and N in any solid material. The method makes use of speeifie nuelear reaetions of these elements with thermal neutrons. The samples are plaeed in the neutron beam from nuclear reactor and the charged products of the neutron indueed reactions (protons or alpha particles) are registered using a standard multiehannel spectrometer. From the measured energy spectra the depth profiles of above mentioned elements can be deduced by a simple computational procedure. 

Irradiation with charged particles accelerated in a cyclotron, while eliminating the problem of long-lived silver isotopes caused by the different nuclear reactions involved, is not feasible for any large-scale study because of the cost involved. Unlike a nuclear reactor, where numerous different samples can be irradiated simultaneously, only a single sample can be irradiated using a cyclotron beam. 

There are several hundred radionuclides that have been used as radiotracers. A partial list of the properties of these nuclides and their production methods are shown in Table 4.1. The three common production mechanisms for the primary radionuclides are (n,y) or (n,p) or (n,a) reactions in a nuclear reactor (R), charged-particle-induced reactions usually involving the use of a cyclotron (C), and fission product nuclei (F), typically obtained by chemical separation from irradiated uranium. The neutron-rich nuclei are generally made using reactors or... 

Activation analysis is based on the production of radioactive nuclides by means of induced nuclear reactions on naturally occurring isotopes of the element to be determined in the sample. Although irradiations with charged particles and photons have been used in special cases, irradiation with reactor thermal neutrons or 14 MeV neutrons produced by Cockcroft-Walton type accelerators are most commonly used because of their availability and their high probability of nuclear reaction (cross section). The fundamental equation of activation analysis is given below ... 

As seen in Table 4.1, there are many techniques for the study of the chemical composition of the bulk and interfaces. Practically, all these methods can be used to study rocks and soils. A part of these methods, however, demands special instrumentation, for example, nuclear reactors or cyclotrons for studies with neutrons and charged particles. Techniques using electromagnetic or electron radiation can usually be carried out in most chemical, geological, and agricultural laboratories. 

Neutrons are the most frequently used projectiles for nuclear reactions. As they do not carry a positive charge, they do not experience Coulomb repulsion, and even low-energy (thermal and slow) neutrons can easily enter the nuclei. Neutrons with energies of the order of 1 to lOeV (resonance neutrons) exhibit relatively high absorption maxima. Furthemiore, neutrons are available in large quantities in nuclear reactors with fluxes of the order of about 10 ° to 10 ° cni s . ... 

One property of special importance is boron s ability to absorb neutrons. Neutrons are subatomic particles with no charge that occur in the nucleus of nearly all atoms. Boron atoms are able to absorb a large number of neutrons. This makes boron useful in the control rods of nuclear reactors. 

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