Cobalt nuclear properties

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

The properties of hydrated titanium dioxide as an ion-exchange (qv) medium have been widely studied (51—55). Separations include those of alkaH and alkaline-earth metals, zinc, copper, cobalt, cesium, strontium, and barium. The use of hydrated titanium dioxide to separate uranium from seawater and also for the treatment of radioactive wastes from nuclear-reactor installations has been proposed (56). 

Nonferrous alloys account for only about 2 wt % of the total chromium used ia the United States. Nonetheless, some of these appHcations are unique and constitute a vital role for chromium. Eor example, ia high temperature materials, chromium ia amounts of 15—30 wt % confers corrosion and oxidation resistance on the nickel-base and cobalt-base superaHoys used ia jet engines the familiar electrical resistance heating elements are made of Ni-Cr alloy and a variety of Ee-Ni and Ni-based alloys used ia a diverse array of appHcations, especially for nuclear reactors, depend on chromium for oxidation and corrosion resistance. Evaporated, amorphous, thin-film resistors based on Ni-Cr with A1 additions have the advantageous property of a near-2ero temperature coefficient of resistance (58). 

There are several examples of well-characterized tri- and tetranu-clear hydroxo-bridged complexes of chromium(III) and cobalt(III). Penta- and hexanuclear aqua chromium(III) complexes have been prepared in solution, but their structure and properties are unknown. Oligomers of nuclearity higher than four have not been reported for cobalt(IIl), with the exception of some hetero-bridged heteronuclear species (193, 194). There appear to be no reports of rhodium(III) or iridium(III) complexes of nuclearity higher than two. 

As of file early 1990s the hislnrieal importance of coball ill alloys for reducing wear resistance was markedly diminished by the development of Norem alloys, which were derived from stainless steel, particularly the Armco Nitronic 60. admittedly one of the few stainless steels that has excellent wear resistance. This is an outgrowth of research conducted by EPRI (Electric Power Research Institute) in an effort to lower equipment costs. Initial uses of the new cobalt-frec alloys will he power plant valves and turbines. Also. In nuclear reactor applications, the Nnrem alloys will not become activated [Co does), reducing worker-protection and maintenance costs. Tests have confirmed that the new cobalt-free alloys retain their wear-resistant properties when produced as rods and powders, the most common forms used by welders. 

The paramagnetic properties of Co(II) have been utilized in some biochemical applications of nuclear magnetic resonance. Cobalt(II)-induced contact shifts were observed in lysozyme (26). A preferential binding of Co2+ to a single site presumably involving two carboxyl groups was deduced. This technique might become very informative in studies of metal ion-dependent enzyme systems. 

The most recent views on the Periodic Classification suggest an entirely different method of removing the anomaly, namely, that the atomic weight is not the correct property to use in arranging the elements rather should one be chosen which increases by a constant amount in passing from one element to the next. Physical theory indicates the positive nuclear charge of the atom to be one such property, whilst experimentally it is found that the X-ray spectra afford such a property, and eliminate the nickel-cobalt anomaly.1... 

Many fewer high-nuclearity cages are known for cobalt than for manganese or iron, and their magnetic properties have not been well studied. Unless otherwise stated, magnetic data have not been reported for the following complexes. 

Cobalt can act as an electron spin resonance, absorption spectral and nuclear resonance probe. It can also be used as a proton probe because its paramagnetism perturbs the proton resonances of neighbouring organic groups. The probe properties of cobalt are described by Foster et al. 

Duan, 1., Liu, 1., Cornelius, T. W. et al. 2009. Magnetic and optical properties of cobalt nanowires fabricated in polycarbonate ion-track templates. Nuclear Instruments and Methods in Physics Research B 267 2567-2570. 

Rare-earth intermetallic compounds with iron are analysed more easily by NMR than those with cobalt or manganese, because the Fe moment is less sensitive to the environment. Thus many NMR studies were reported despite the disadvantageous NMR properties of the favourite Mossbauer nucleus Fe (small natural abundance, small nuclear magnetic moment). was the favourite non-magnetic rare-earth NMR probe. 

Radium was also utilized in self-luminous paints for watch, clock and instrument dials and for emission in automatic control systems. Safer radioisotopes for technical properties, such as cobalt-60 and cesium-137, can nowadays be tailored in nuclear reactors and have entirely replaced radium. This has released us from the need for radium, which is a great advantage, as radium is so difficult to handle from an environmental point of view. It forms gaseous radon, affecting its surroundings. And the problem remains for a long time, as the most usual radidum isotope, Ra, has a half-life of 1600 years. Nowadays the use of radium has ceased. The annual amount manufactured is only round 100 g. 

The half-value dose is the dose at which a property has been reduced to one half of its original value. Electron accelerators of various designs or y-radiation sources based on radioactive cobalt 60 ( Co) are the radiation sources typically used for targeted electron irradiation. The changes in plastics caused by radiation are the same for all types of radiation. Irradiation does not turn plastics radioactive. The only exceptions are neutrons (that occur almost exclusively in the core of nuclear reactors). They can activate plastics. 

Many of the HEAs contain cobalt, which is not a desirable material for in-core nuclear reactor applications due to the neutron-induced transmutation to produce °Co that can make some plant maintenance activities more difficult (due to normal corrosion processes that cause atomic deposition of core materials throughout the primary coolant loop, particularly in the cooler regions). Some single-phase HEAs with attractive mechanical properties that do not contain cobalt have been manufactured [116]. Tensile properties for a single-phase fee high-entropy alloy are summarized in Fig. 16.6. 

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