Chromium nuclides

Consider three isotopes of chromium 24Cr, ilCr, and 24Cr. Chromium-52, the most abundant, is stable. One of the other nuclides undergoes beta emission, and the remaining nuclide undergoes electron capture. Identify the isotope that makes each of these changes, and explain your choices. 

In stars with very heavy average masses, helium burning may last for only a few million years before it is replaced by carbon fusion. In time this leads to the production of elements such as calcium, titanium, chromium, iron, and nickel fusion partly by helium capture, partly by the direct fusion of heavy nuclides. For example, two Si can combine to form Ni that can decay to Co which then decays to stable Fe. These last steps of production may occur rather rapidly in a few thousand years. When the nuclear fuel for fusion is exhausted, the star collapses and a supernova results. 

In EC decay, the chemical effects of the X-ray intensity ratio KJK was first observed by Tamaki et al. for various chromium compounds labeled with Cr. A Si(Li) detector was used to measure the X-rays emitted from the nuclide. When the measured data of K, /K, are plotted against the formal oxidation number of diromium, it is seen that the ratio generally increases with the chromium valence number. This is shown in Fig. 2. A notable exception is, however, metallic chromium, where the formal oxidation number does not reflect the electronic state surroimding the chromium atom at all. 

Co and in particular in the upper zones of the oxide layers in the steam generator tubes of US PWRs, seem to decrease with increasing operating time the same is apparently true for the element-specific activities of Co and Mn, but not for that of Co (each related to the mass of the respective parent nuclide). The predominant fraction of the deposited radionuclides, in particular of °Co, is incorporated into the lower section of the oxide layer, i. e. into the chromium-rich spinel directly covering the base material. 

Each of the following nuclides is used in medicine. Indicate the number of protons and neutrons in each nuclide (a) phosphorus-32 (b) chromium-51 (c) cobalt-60 (d) technetium-99 (e) iodine-131 (f) thallium-201. 

A sample of chromium contains 8.9 x 10 g of the radioactive nuclide chromium-51, which has a half-life of 28 days. What mass of chromium-51 will remain in the sample after 168 days ... 

Stainless steel is composed of iron (Fe), chromium (Cr), and nickel (Ni). What reactions would produce the following radioactive isotopes if stainless steel is irradiated in the reactor You may refer to a chart of the nuclides, and the short version of notation is acceptable (e g. Al-27(n,a)Na-24). 

As for nickel alloys, type 625 and type 800 alloys have been considered for the steam cooled FBR concept by B W, GE, and WH [16]. Table 2.1 [9] shows an example composition of a nickel alloy and neutron absorption cross sections of each nuclide. From the viewpoint of neutron economy, materials with low thermal neutron absorption cross sections are more desirable for the cladding. It can be easily seen from Table 2.1 [9] that nickel has the dominant contribution to the neutron absorptions of the alloy. Chromium and iron also have relatively large contributions. Although boron has an especially large thermal neutron absorption cross section, since its content is very small, its influence is expected to be negligible on the neutron economy. 

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