Cobalt nuclides

Fe, liver and kidney for cobalt nuclides, liver and prostate for Zn, skeletal muscle for Cs, and GI tract for Zr. The persistence of radionuclides in mammals varies with the chemical form, kinetics, species, and other variables. Thus, the time for 50% persistence of selected radionuclides in whole-animal studies ranges from 19 h to 14 days for 4 to 35 days for Cs 5 to 12h for the short-lived component of Co, 5 to 21 days for the long-lived component 25 to 593 days for Sr and 4 to 26 days for... 

C22-0041. Use atomic masses to compute the total binding energy and the binding energy per nucleon for elemental cobalt, which has just one stable nuclide. 

The procedure for separating Sb-119 from an alpha-irradiated tin target has been described elsewhere (10,11). The amounts of cobalt and antimony coexisting with the nuclides are estimated to have been about 400 ng/mCi and 300 ng/mCi, respectively, i.e., to have been much smaller than that required for monolayer coverage of 30 mg of the hematite sample. About 10 cm3 of an aqueous solution containing 1 - 2 mCi of divalent Co-57 or 0.1 - 1 mCi of pentavalent Sb-119 was adjusted to an appropriate pH value in a Teflon vessel with a 0.5 mm-thick Teflon window at the bottom, and about 30 mg of hematite powder was added to the solution. The suspension was shaken for 30 min at room temperature. After settling of the powder at the bottom of the vessel, the pH was remeasured. 

The present method is still in its early stage of application. Both ex situ and in situ type measurements are applicable to a variety of mineral/aqueous solution interfaces. For example, the mechanism of selective adsorption of cobaltous ions on manganese minerals can be studied by this method. In addition to the two Mossbauer source nuclides described in the present article, there are a number of other nuclides which can be studied. We have recently started a series of experiments using Gd-151 which is a source nuclide of Eu-151 Mossbauer spectroscopy. Development of theory on surface magnetism, especially one including relaxation is desirable. Such a theory would facilitate the interpretation of the experimental results. 

Once we have the appropriate nuclide, we must separate the radiation of interest from all other radiation present. A typical gamma spectrum is shown in Figure 3 for cobalt-57 in palladium. The radiations which can be identified include the 6-k.e.v. x-ray, the 14-k.e.v. y-ray of interest, and a sum peak and palladium x-ray peak, both lying at about 21 k.e.v. If one now sets the single-channel analyzer window correctly, one observes essentially only the 14-k.e.v. peak, but all of this is not recoil-free radiation it includes other radiation which falls into the window from various gamma quantum de-excitation processes. 

The nuclear industry makes available about 3000 nuclides, including both the stable and the radioactive nuclides. Approximately 50 radioactive nuclides, along with some stable nuclides that have been isotopically enriched, are essential in research, medical, and industrial applications. Many of these are now produced commercially, but several still are dependent on government facilities. Some, for economic reasons, come from other countries. Radiation processing for sterilization of disposable medical supplies is an important operation using cobalt-60 from Canada. Electron accelerators have replaced... 

The medical applications of nuclear technology range from in vitro and in vivo injections for diagnostic tests to cobalt radiation for cancer therapy. A new medical specialty was created, a family of compact cyclotrons was developed to provide short-lived nuclides, and a sizable industry evolved to produce technetium. Until the nuclear industry was created, technetium had been missing from the chart of chemical elements because the half-life of the most stable member was too short, 21,000 years. Technetium and several other nuclides of importance here are discussed elsewhere in the chapter in connection with their production (see Table 21.19).60,61... 

One of the important applications of MBssbauer spectroscopy is in the determination of bonding of the MBssbauer nuclide. Since the cobalt MBssbauer s ctrun can only be observed in the emission mode, the radioactive isotope must be inserted into the... 

The use of cobalt radiation treatments for cancerous tumors was described in Example 26-3. Several other nuclides are used as radioactive tracers in medicine. Radioisotopes of an element have the same chemical properties as stable isotopes of the same element, so they can be used to label the presence of an element in compounds. A radiation detector can be used to follow the path of the element throughout the body. Modern computer-based techniques allow construction of an image of the area of the body where the radioisotope is concentrated. Salt solutions containing "iNa can be injected into the bloodstream to follow the flow of blood and locate obstructions in the circulatory system. Thallium-201 tends to concentrate in healthy heart tissue, whereas technetium-99 concentrates in abnormal heart tissue. The two can be used together to survey damage from heart disease. 

Like many other radioactive nuclides used in medicine, cobalt-60 is made by bombarding atoms of another element (in this case iron) with neutrons. The iron contains a small percentage of iron-58, which forms cobalt-60 in the following steps ... 

One of the more controversial uses of radioactive nuclides is in food irradiation. Objective 32 Gamma ray beams, X rays, and electron beams have been directed at food for a variety of purposes. Radiation inhibits the sprouting of potatoes and onions, retards the growth of mold on strawberries, and kills bacteria in poultry and fisb. Cobalt-60 and cesium-137 have been used for these purposes. The controversy lies in whether the radiation causes changes in the food that could have adverse health consequences. 

Cobalt-60, which is the most common nuclide used in radiation therapy for cancer, undergoes beta emission. Write the nuclear equation for this reaction. 

Radionuclide is a shortened form of radioactive nuclide , practically synonymous with radioisotope or radioactive isotope . A particular chemical element may consist of a number of nuclides, some of which may be radionuclides, characterized by the name of the chemical element followed by a number denoting the atomic mass of the nuclide in question, e.g. cobalt-60 and uranium-235. IMO Class 7, 2.20... 

Even during normal operation, the primary coolant contains a certain amount of radioactivity, partly due to nuclides formed by the irradiation in the core of elements dispersed in the coolant (oxygen, hydrogen, cobalt, iron, etc.) and partly due to the presence of defective (fissured) claddings in the core which let a part of the gap inventory escape into the coolant. The concentration of radioactive products in the water depends on the entity of fissures (in general, it is assumed that 1-2 per cent of the elements have fissures) and on the effectiveness of the primary water purification system. 

The requirement of high specific activity restricts the choice of nuclide principally to tritium, iodine 125 and cobalt 57. A high specific activity is required because the nuclide must serve as a tracer to a trace amount of analyte. Carbon 14 and other nuclides commonly used as tracers are generally not satisfactory for RIA applications. 

Iron-57 is the most important Mossbauer nuclide even though it has a natural abundance of only 2.2%. The half-life of its 14.41 keV excited state is 98.1ns and the half-life of its precursor source, cobalt-57, is 270 days. As a result, the resolution of iron-57 Mossbauer spectroscopy, 6.5 X 10 —the ratio of the linewidth to the 7-ray energy—is excellent. Because the typical iron-57 hyperfme parameters are of the order of a few millimeters per second and range up to many times the natural linewidth of 0.194mm s they are easily measured with excellent resolution. 

The absorption reaction can also result in a nuclide that is radioactive that will eventually decay itself, releasing more radiation. A common example of this at nuclear power reactors is neutron absorption by cobalt-59, a stable element, to create cobalt-60, which decays by beta decay and also releases two relatively high-energy gamma rays. Figure 25.12 graphically demonstrates this process. 

As a very important topic in contamination buildup, the question is still open to what extent the data on corrosion product solubilities in the primary coolant are of importance for the behavior of trace amounts of cobalt. It seems to be still questionable whether cobalt ferrites as a well-defined compound with properties similar to the nickel ferrites can exist under PWR primary coolant conditions, whether cobalt atoms can be incorporated into a nickel ferrite lattice or whether traces of cobalt may be deposited onto the surfaces of the reactor core by adsorption on other, already deposited oxides. Such adsorption processes may occur even on the Zircaloy oxide films in the absence of any net deposition of corrosion products. Experimental investigations of the interaction of dissolved cobalt with heated Zircaloy surfaces (Lister et al., 1983) indicated that at low crud levels in the coolant cobalt deposition on surfaces is dominated by processes involving dissolved species, with adsorption/desorption processes being the responsible mechanisms. The extent of cobalt deposition is controlled by the type of oxide present on the Zircaloy surface thin black films of zirconium oxide will pick up less cobalt from the solution than thick white oxide films, even when the differences in the available surface areas of both types of oxides are taken into account. The deposition process seems to be little affected by the heat flux in the exposed metal. According to Thornton (1992), such adsorption-desorption exchange processes provide a pathway for radioactive species to be transported around the circuit even when the net movement of corrosion products is minimized this means that under such circumstances the processes of activity transport and of corrosion product transport may be decoupled. They may provide a pathway for target nuclides such as Co to be adsorbed onto fuel rod surfaces even in a core which is virtually free of deposited corrosion product particles. 

Some in-service decontamination techniques have also been proposed to reduce the amount of deposited radionuclides. According to the results of loop experiments reported by Amey et al. (1989), the amount of cobalt which is deposited in a PWR primary circtiit can be reduced by treatment with elevated boric acid concentrations at temperatures around 120 °C. This procedure results in a comparatively high concentration of dissolved cobalt in the coolant (values on the order of 500 ppt were measured) which can be removed by the purification system. This effect is probably due to dissolution or leaching of the outer iron-rich corrosion product layer, which usually contains comparatively high amounts of cobalt. Based on these results, an on-line chemical treatment for cobalt management was proposed for application to established plants as well as in the pre-operational phase during which the parent nuclide Co can be removed before activation to Co occurred. 

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. 

Mossbauer spectroscopy of these systems is rather challenging. For high-Tc superconductors, the greatest challenge is typically the lack of Mossbauer active nuclides in those compounds (not counting the lately discovered oxypnictides). Thus, iron or cobalt doping is required for a Mossbauer study. The comparison of emission and transmission results can be very beneficial. 

In medicine, radioactive nuclides, such as the artificial radioactive nuclide cobalt-60, are used to destroy certain types of cancer cells. Many radioactive nuciides are aiso used as radioactive tracers, which are radioactive atoms that are inccrpcrated into substances so that movement of the substances can be foiiowed by radiation detectors. Detection of radiation from radioactive tracers can be used to diagnose cancer and other diseases. 

A FIGURE 19.19 Radiotherapy for Cancer This treatment involves exposing a malignant tumor to gamma rays generated by nuclides such as cobalt-60. The beam is moved in a circular pattern around the tumor to maximize exposure of the tumor to radiation while minimizing the exposure of healthy tissues. 

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