Sections of Particular Importance in Reactor Physics

Cross Sections of Particular Importance in Reactor Physics 

The scattering cross section for carbon (C ) shows a similar behavior, again characterized by the relatively widely spaced resonances typical of a low-mass nucleus. Above about 20 MeV the peaks are no longer visible, since 

The closer-spaced resonance structure of the compound nuclei formed at the high-mass end of the periodic table leads to a pronounced difference in the form of the cross-section curve. The characteristic features of the absorption cross section of a heavy nucleus are illustrated in Fig. 1.13, which shows the (n, y) absorption cross section of The most prominent 

The total cross section of which is of fundamental importance for virtually all reactors, is illustrated in Fig. 1.16. The intermediate energy region is characterized by the presence of a large number of resonances, with an average spacing of about 17 eV. An interesting feature is the clearly de- 

Absorption and scattering cross sections for the elements of importance in reactor physics are summarized in Table A.4. For reasons to be discussed later, the values given are for a neutron energy of 0.0253 eV, corresponding to a neutron velocity of 2200 ms Attention may be drawn to some of the particularly low absorption cross sections, such as that of zirconium, which is consequently valuable as a structural material in reactors. The reason for zirconium, and also lead, having such a low cross section is that the main isotope in both cases has a nucleus with a magic number of neutrons or protons, or both (see Section 1.4). 

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