Cobalt isotopes

Further work on nickelocene and cobaltocene was done by Ross , who synthesized the respective compounds using Ni, Ni and " Co, which decay be E.C., jS and a fully converted isomeric transition, respectively, all producing radioactive cobalt isotopes. The results showed retentions, after sublimation, of 84%, 83% and 80%, respectively. The composition of the unsublimable residue was largely CoCp2, except for the highly converted "Co, where only 30% CoCpj could be detected. This was interpreted as showing that by internal conversion the molecules are totally destroyed, by the same sort of argument as was used by Riedel and Merz . 

CobaltCII) iodide, uses, 7 240t CobaltCII) ion, 7 229 CobaltCIII) ion, 7 229 Cobalt isotopes, residual radiation from, 17 553-554... 

Positive-ion and reflectron-mode MALDI spectra of the CoPc 40 could be obtained in ACCA matrix. The isotopic peak distribution of the protonated molecular ion peak was due to the carbon and cobalt isotopes, and the experimental isotopic peak distribution (shown as inset) in Fig. 23 corresponded to the theoretical calculations. For the other ball-type Pcs, MALDI-TOF-MS and their details can be found in the following references or in the Supplementary Materials sections [24,25,41,42,44,45,49],... 

Co is the only naturally occurring cobalt isotope. With its magnetic moment of 4-639 /in it is less sensitive than the proton by a factor of 3. The handicap of the large quadrupole moment of 0-38 barn... 

There is no critical mass in a fusion bomb, and the force of the explosion is limited only by the quantity of reactants present. Thermonuclear bombs are described as being cleaner than atomic bombs because the only radioactive isotopes they produce are tritium, which is a weak /S-particle emitter (ti = 12.5 yr), and the products of the fission starter. Their damaging effects on the environment can be aggravated, however, by incorporating in the construction some nonfissionable material such as cobalt. Upon bombardment by neutrons, cobalt-59 is converted to cobalt-60, which is a very strong 7-ray emitter with a half-life of 5.2 yr. The presence of radioactive cobalt isotopes in the debris or fallout from a thermonuclear explosion would be fatal to those who survived the initial blast. 

Radioactive cobalt-60 is used to study defects in vitamin B12 absorption because cobalt is the metallic atom at the center of the vitamin molecule. The nuclear synthesis of this cobalt isotope involves a three-step process. The overall reaction is iron-58 reacting with two neutrons to produce cobalt-60 along with the emission of another particle. What particle is emitted in this nuclear synthesis What is the binding energy in J per nucleon for the cobalt-60 nucleus (atomic masses Co = 59.9338 amu ... 

The source most commonly employed with Fe Mossbauer spectroscopy is elemental Co, which is incorporated into rhodium or copper metal. During the radioactive decay of the cobalt isotope into Fe, the needed gamma radiation is emitted. For measurements with tin ( Sn), sources of CaSnOs or BaSnOs enriched with Sn are used, which again release the proper radiation during their radioactive decay. The source is moved at constant positive and subsequently negative accelerations (i.e. linearly varying speed) to probe the resonant absorption. 

The nuclear reaction Co (n,y) Co is the most frequently used monitoring reaction for thermal neutrons over longer exposure periods. The only stable cobalt isotope Co reacts with thermal neutrons to Co as well as directly to Co since ° "Co decays almost completely (99.74%) to Co with a halflife of 10.2 min it can be ignored in the determination of neutron fluence data. Thus, in practice, °Co can be regarded as the only reaction product. Both y transitions of Co at 1.17 and 1.33 MeV show transition probabilities of 100% each. 

Only little information is available concerning the behavior of the actinides in the primary circuit purification system. If one assumes a plutonium purification factor identical to that of the cobalt isotopes, one could calculate the approximate level of the plutonium inventory of the ion exchanger beds. Such a calculation for... 

From the different topics discussed in the preceding sections it can be concluded that there are different possible ways of keeping the buildup of primary circuit contamination low or of reducing already existing contamination levels. Their common aim is to keep the production of radioactive cobalt isotopes low and/or to minimize the transport of the radionuclides produced from the reactor pressure vessel to other regions of the primary circuit and, in addition, to minimize their plate-out on the surfaces there. Because of the importance of low radiation levels for an undisturbed operation and maintenance of the plants, different measures have been attempted with quite varying success. 

Taking into account that development of a comprehensive model is not feasible given the current state of knowledge, a simple kinetic model Actranf has been elaborated by Harper et al. (1992). In this model, the primary circuit is divided into three main sections the coolant, the in-core surfaces and the out-of-core surfaces. Cobalt is introduced into the system by release from circuit materials, either as Co from any point in the circuit or as Co from activated materials in the neutron field. Both isotopes are removed from the coolant to the purification system by a first-order process, and are also removed from the circuit when they have been deposited on fuel assembUes that are withdrawn from the reactor in the course of refuelling. Co is converted to Co by neutron activation when it is deposited on fuel surfaces or when it is contained in the internals of the reactor pressure vessel. Thus, unlike the models described above, Actranf considers both possible Co sources the calculations showed that activation of Co which is temporarily deposited in the reactor core is only a small contributor when compared with the direct release of Co from in-core sources, in particular in plants equipped with Stellites inside the reactor pressure vessel. Distribution of cobalt isotopes around the surfaces of the primary circuit proceeds by exchange of dissolved species with the coolant deposition and re-release are assumed to be first-order processes. The first applications of the model to operating plants with and without Stellite materials in the primary circuit have yielded encouraging results. 

The concentrations of the corrosion product radionuclides in the reactor water depend on the same parameters as those that control the behavior of the total corrosion products and, in addition, on the intensity of neutron activation. As a consequence, the concentrations of radioisotopes may vary considerably from plant to plant and also within a plant. According to the observations reported by Anstine et al. (1984), the concentrations of Co and Co, the two most prevalent radioisotopes, do vary, but not as greatly as the iron concentrations. In the BWR plants examined in this context, the majority of Co and Co in the reactor water appeared in the dissolved state. On the average, the concentrations of dissolved Co increased for the first 3 to 5 fuel cycles and then leveled off to values on the order of 7 kBq/1, whereas the dissolved Co already reached its steady-state level in the same range of concentrations during the first fuel cycle. These differences in the time behavior of both cobalt isotopes probably are to be attributed to their different halflives. The concentrations of particulate Co and Co, on the other... 

The number of protons identifies an element. Some elements may have atoms that contain different numbers of neutrons. The different atoms of the same element are then called isotopes. Because of the different number of neutrons in one isotope of an element, it can be quite radioactive that is, the nucleus is progressively breaking apart and giving off radiation. The type and amount of radiation determines the degree of risk. The radiation from isotopes is used in controlled situations - for example, cobalt therapy, for treating cancer. Cobalt 60 therapy uses a cobalt isotope with 33 neutrons. Normal cobalt in vitamin B12 or soil fertihzer almost alw s contains only 32 neutrons. Your home smoke detector may contain a 37kBq source of americium 241. Some natural elements, e.g. chlorine, are a mixture of two long-lived isotopes of the element. 

Contamination of the primary circuit of water-cooled reactors is essentially governed by the behaviour of iron, chromium, nickel and cobalt isotopes in the coolant. Since cations can easily be built into the metallic surface, the decontamination can only be carried out by the removal of the upper layer of the items containing the above mentioned radioactive isotopes. 

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