Cerium nuclides

Radiocerium can also gain entry into food crops through irrigation or flooding of fields with waters containing these nuclides. However, only small amounts of radiocerium enter food crops by this route compared to the more soluble radioelements that have been studied. Cerium-144 originating from both the Hanford reactors and worldwide... 

Therefore, the preliminary investigation described herein examined several aspects of the behavior of the equilibrium distribution coefficients for the sorption of rubidium, cesium, strontium, barium, silver, cadmium, cerium, promethium, europium, and gadolinium from aqueous sodium chloride solutions. These solutions initially contained one and only one of the nuclides of interest. For the nuclides selected, values of Kp were then... 

Therefore, based on available literature, the following sorption results were expected (l) as a result of the smectite minerals, the sorption capacity of the red clay would be primarily due to ion exchange associated with the smectites and would be on the order of 0.8 to I.5 mi Hi equivalents per gram (2) also as a result of the smectite minerals, the distribution coefficients for nuclides such as cesium, strontium, barium, and cerium would be between 10 and 100 ml/gm for solution-phase concentrations on the order of 10"3 mg-atom/ml (3) as a result of the hydrous oxides, the distribution coefficients for nuclides such as strontium, barium, and some transition metals would be on the order of 10 ml/gm or greater for solution-phase concentrations on the order of 10 7 mg-atom/ml and less (U) also as a result of the hydrous oxides, the solution-phase pH would strongly influence the distribution coefficients for most nuclides except the alkali metals (5) as a result of both smectites and hydrous oxides being present, the sorption equilibrium data would probably reflect the influence of multiple sorption mechanisms. As discussed below, the experimental results were indeed similar to those which were expected. 

For the nuclides studied (rubidium, cesium, strontium, bariun silver, cadmium, cerium, promethium, europium, and gadolinium) the distribution coefficients generally vary from about 10 ml/gm at solution-phase concentrations on the order of 10 mg-atom/ml to 10 and greater at concentrations on the order of 10 and less. These results are encouraging with regard to the sediment being able to provide a barrier to migration of nuclides away from a waste form and also appear to be reasonably consistent with related data for similar oceanic sediments and related clay minerals found within the continental United States. 

In nuclear fission a heavy nuclide splits into two or more intermediate-sized fragments when struck in a particular way by a neutron. The fragments are called fission products. As the atom splits, it releases energy and two or three neutrons, each of which can cause another nuclear fission. The first instance of nuclear fission was reported in January 1939 by the German scientists Otto Hahn (1879-1968) and Fritz Strassmann (1902-1980). Detecting isotopes of barium, krypton, cerium, and lanthanum after bombarding uranium with neutrons led scientists to believe that the uranium nucleus had been split. 

Because of the high radiotoxicity of most of the actinide nuclides, only very limited studies of the biokinetics of plutonium and other important actinides are possible in human volunteers. As our information about the long-term retention of actinides is limited, there is interest in the possible use of stable lanthanide elements as surrogates for the actinides for long-term biokinetic studies in humans. The aim of such studies is to inject appropriate stable isotopes of lanthanides such as cerium, europium, and gadolinium into human volunteers and then to measure the excretion of the lanthanide in urine and faeces by mass spectrometry, charged-particle activation analysis or similar methods. Also, limited human studies can also be carried out using small doses of appropriate lanthanide radionuclides (Bailey 1989). 

Fig. ilC.l. Nuclidic table representation of rare earths and interfering molecular ions for a cerium matrix. 

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