Isotopes from fission

The use of technetium-99m (half-life = 6.006 h) in diagnostic medicine , particularly for brain and heart imaging " , has became widespread since the availability of macroscopic quantities of the long-lived technetium-99 isotope from fission products (half-life =2.13 X 10 yr, weak j8"-emiter, = 0.292 MeV, = 85keV. Normal glassware... 

With the reaction oven temperature kept at 900°C and typically 100 ml/min CI2 saturated with SOCI2 plus 2 ml/min O2, the chromatographic behavior ofshort-Hved Mo isotopes from fission and of short-lived W isotopes produced at the PSI Philips cyclotron in the Gd( Ne,xn) reaction was studied and values of of —90 kJ/mol were measured for... 

The fission product which has an important effect on the short-term behavior of the reactor is Xe. The direct fractional yield of this isotope from fission is only some 0.3 %, and most of it is in fact derived from the radioactive chain shown below ... 

Potential fusion appHcations other than electricity production have received some study. For example, radiation and high temperature heat from a fusion reactor could be used to produce hydrogen by the electrolysis or radiolysis of water, which could be employed in the synthesis of portable chemical fuels for transportation or industrial use. The transmutation of radioactive actinide wastes from fission reactors may also be feasible. This idea would utilize the neutrons from a fusion reactor to convert hazardous isotopes into more benign and easier-to-handle species. The practicaUty of these concepts requires further analysis. 

Separation of krypton and xenon from spent fuel rods should afford a source of xenon, technical usage of which is continuously growing (84). As of this writing, however, reprocessing of spent fuel rods is a pohtical problem (see Nuclearreactors). Xenon from fission has a larger fraction of the heavier isotopes than xenon from the atmosphere and this may affect its usefulness in some appHcations. 

Delayed Proton and Neutron Decays. By means of a variety of nuclear reactions, as weh as the spontaneous fission of synthetic nucHdes, large numbers of isotopes of some elements have been produced. For example, whereas the only stable isotope of Cs (Z = 55) is Cs (JV = 78), ah of the Cs isotopes from Cs where 77 = 59 and = 0.57 s, to Cs where N = 93 and = 0.13 s, have been observed. At the low mass end of this series, the last proton is only loosely bound, and at the high mass end, the last neutron is only loosely bound. 

Cesium isotopes can be recovered from fission products by digestion in nitric acid, and after filtration of waste the radioactive cesium phosphotungstate is precipitated using phosphotungstic acid. This technique can be used to prepare radioactive cesium metal or compounds. Various processes for removal of Cs isotopes from radioactive waste have been developed including solvent extraction using macrocycHc polyethers (62) or crown ethers (63) and coprecipitation with sodium tetraphenylboron (64). 

Synthesis of ruthenocene from fission-product ruthenium isotopes was done by neutron irradiation ofU30g and FeCpj powder mixtures. It was shown that most of the ruthenocene found was actually produced by the decay of a precursor. Subsequent knowledge makes it apparent that the fission product recoils formed a rhodium dicyclopentadienide whose structure was preserved through the decay . The total yield of ruthenocene reached a value of 60% under some experimental conditions and was rarely less than 40%. 

Terrestrial isotope ratios are mainly unaffected by these processes and therefore provide valid information about standard abundances of individual nuclear species except in special cases where they have been modified by fractionation (e.g. D/H), differential escape from the atmosphere or radioactive decay, e.g. 40Ar is enhanced in the atmosphere relative to 36Ar by 40K decay and there is extra 136Xe thought to result from fission of 244Pu. 

ISOTOPES There are 24 isotopes of americium. All are radioactive with half-lives ranging from 72 microseconds to over 7,000 years. Five of americium s isotopes are fissionable with spontaneous alpha decay. 

The discovery of this element is credited to J.A. Marinsky and L.E. Glendenin who, in 1945, identified its long-lived isotope Pm-147 (ti/2 2.64 years) in the fission products of uranium. They named the element after Prometheus, who according to Greek mythology stole fire from heaven. The element was first isolated from fission product wastes by G.W. Parker and P.M. Lantz in 1948. It first was recovered from natural sources by O. Erametsa in 1965. An amount less than 0.5 g was recovered from 20 tons of rare earths. 

Promethium—147, the isotope used commercially, is isolated from fission product wastes. The radioactive materials must be handled safely in a glove box. The metal complexes either with ethlenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) and is isolated by elution from Dowex 50. 

There are no stable isotopes of technetium. The element is obtained from fission reactions rather than from natural sources. The most commonly encountered isotopes are Tc, a weak 292-keV emitter with a half-life of 2.1 x 10 yr, and Tc, a metastable form that decays to Tc with the emission of a 140-keV y photon with a half-life of ca 6 h. The coordination chemistry [1, 2] and electrochemistry [3] of technetium have been reviewed on several occasions. 

Constructing a fission bomb is a formidable task. The difficulty is in separating enough uranium-235 from the more abundanr uranium-238. Scientists took more than 2 years to extract enough of the 235 isotope from uranium ore to make the bomb detonated at Hiroshima, Japan, in 1945. To this day, uranium isotope separation remains a difficulr process. 

Apart from fission and radiogenic components, it appears that the principal underlying relationship between terrestrial Xe and solar Xe is a strong (about 3.5%/amu) mass-dependent isotopic fractionation. This is shown in Figure 7.6. To a good approximation, atmospheric Xe is related to SUCOR Xe, a solar Xe composition calculated to be surface-correlated Xe in a lunar mare soil. However, it is also clear that slight deviation from a linear trend indicates that atmospheric Xe and solar Xe cannot be related solely by fractionation. 

However, light xenon isotopes from 129 to 124 were also over-abundant [61,67,68] in such meteorites and enriched [66] in the tiny host phase although they are not formed in fission. Whether there are at least two anomalous xenon components of different origin, remained controversial for years [69]. Eventually, the fission origin of the anomalous xenon was ruled out [70] because in a host phase containing the excess xenon no enrichment was detected for the adjacent barium isotopes 130 to 138, which are abundant fission products. 

Element uptake from soil and transfer into the edible parts of plants have been addressed in several other studies. Soil-to-plant transfer factors in fruit and vegetables grown in various agricultural conditions have been determined for, for example, Pt [100], T1 [101], and various other metal contaminants [102], In a study on stable isotopes of fission product elements (Ce, Cs, Sr), an in vitro enzy-molysis method has been applied to investigate the solubilization of the analytes from fodder in a simulated ruminant digestion [103], The effect of inhibitors of fission product solubility was also considered and essential elements were determined simultaneously to evaluate potential nutrition problems for the animals from the use of such inhibitors. Selective leaching of individual classes of metal complexes with different ligands and sequential enzymolysis have been recently applied to estimate the potential bioavailability to humans of Cd and Pb in cocoa powder and related products [104]. 

Tc was the first element to be synthesized artificially, hence its name. It was first detected in 1937 by Perrier and Segre in the products of deuteron bombardment of Mo. All the isotopes of Tc are radioactive but Tc, with a half-hfe of 2.1 x 10 y, is a sufficiently long-lived /3-emitter that it can be handled in standard laboratory equipment with appropriate precautions. It is recovered from fission reactors by solvent extraction and ion-exchange methods. It makes up ca. 6% of fission products from U and so is available in kilogram amounts for macroscopic chemical study. Hot acid solutions... 

Nuclear fission is a process in which the nucleus of an atom splits, usually into two pieces. This reaction was discovered when a target of uranium was bombarded by neutrons. Eission fragments were shown to fly apart with a large release of energy. The fission reaction was the basis of the atomic bomb, which was developed by the United States during World War II. After the war, controlled energy release from fission was applied to the development of nuclear reactors. Reactors are utilized for production of electricity at nuclear power plants, for propulsion of ships and submarines, and for the creation of radioactive isotopes used in medicine and industry. 

A number of stable and radioactive xenon isotopes exist and are shown in Table 1 along with their natural abundance and cumulative fission yield. The most studied xenon isotopes from the environmental radioactivity perspective are those that both are produced significantly in processes that can release these into the environment and have relatively long half-lives. 

Radioxenon production in reactors is thought to arise from two pathways, first via xenon emitted from cracks in fuel rods, and secondly from fission of uranium on the exterior of fuel rods or in cooling water. Radioxenon released from medical isotope production comes... 

The presence of uranium in a sample exposed to a flux of thermal neutrons can cause errors if the nuclide or nuclides determined are fission products or are isotopic with them. Hudgens and Dabagian (39) determined zirconium in zirconium-hafnium mixtures by separating the Nb , daughter of Zr formed by n,y reaction, after the addition of carrier. Contributions from fission product niobium (Nb ) can be allowed foi by irradiating a further sample, isolating fission product Ba ° and from the fission yield curve making allowance for radioactive niobium derived from any uranium impurity. 

Nuclear power plants use nuclear fission to generate power. The first nuclear fission reaction discovered involved uranium-235. As you can see in Figure 25-16, when a uranium-235 nucleus is struck by a neutron, it undergoes fission. Barium-141 and krypton-92 are just two of the many possible products of this fission reaction. In fact, scientists have identified more than 200 different product isotopes from the fission of a uranium-235 nucleus. 

In order to develop the atomic bomb, it was necessary to separate the more easily fissionable isotope from Because the natural abundance of is only 0.7%, its isolation... 

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