Cesium Transport Research Articles

Zur diffusionskinetik nach dem fallenmodell bei dritter randbedingung

The diffusion of activated fission-products in graphite and corresponding measurements of cesium transport are considered. Solutions of the diffusion equation with constant absorption- and reemission-coefficient were evaluated. As boundary condition the flux through the surface of the specimen was assumed to be proportional to the difference concentration on the surface minus a fixed given concentration, which condition corresponds to an evaporation. In particular the Fouriersums for cylinder, sphere and rectangular parallelepiped are determined and discussed especially with respect to neglect of reemission for small times and on asymptotic behaviour for large times. As initial condition there is assumed uniform distribution and thin layer concentration for one dimensional space dependence.

Distribution of cesium in the organism and its effect on the nucleotide metabolism enzymes.

After the intraperitoneal administration of 0.5 mEq 134 CsCI . kg -1 to mice, the maximum cesium level in the kidney's, heart, lungs and liver was found in the first hour (T 1/2 13 h), in the muscles after 8 h (T 1/2 180 h), in the brain after 24 h (T 1/2 140 h) and in the blood after 24 h. Maximum cesium levels were found in the muscles. Rats excreted about 17% of the administered dose in 24 h and 38% in 144 h. Most of the cesium (about 90%) is excreted in the urine. In rats, equalization of the plasma and RBC cesium levels takes longer than 6h. Cesium transport is not entirely dependent on the ATPase system, as shown by the results given by the crude mitochondrial fraction with a reduced potassium content. Among the various univalent ions studied, the effect of cesium on creatine kinase, 5'-nucleotidase, phosphodiesterase and deaminase activity was the smallest.

Evaluation of a combined sorption model for describing cesium transport in a soil.

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Erosional Transport and Deposition of Plutonium and Cesium in Two Small Midwestern Watersheds

AbstractThe soils and sediments of two small watersheds and their retaining ponds were sampled in a study of the erosional transport of plutonium and cesium in midwestern ecosystems. In a watershed which had been used exclusively for row crops no relationship was observed between plutonium content of the sediments and location in the pond or clay content. In a pasture watershed sorting of the eroded material had occurred prior to entry into the pond and also within the pond. Clay content in the pasture pond sediments was significantly higher than in the soils of the surrounding watershed and increased with increasing distance from the inlet. Plutonium concentration in the sediments was strongly correlated with clay content, reflecting the higher plutonium content of finer soil particles. Cesium behaved similarly to plutonium in the soils and sediments of both watersheds. Where sorting occurs, as in the pasture watershed, deposits of fine sediments will contain higher plutonium and cesium concentrations than in the original surface soil.

Cesium Release and Transport in Biso-Coated Fuel Particles

Theoretical and experimental aspects of cesium release from Biso-coated high-temperature gas-cooled reactor fuel particles are reviewed. Three types of transport are considered: diffusion through the pyrolytic carbon (PyC) coatings under conditions of a constant source potential, transport due to a continuously depleting source, and diffusion from a depleting source following constant source potential transport. Analysis of all of the release data obtained in this laboratory yields the following relations for the diffusion coefficient DCs characteristic of cesium transport through PyC coatings:For coatings deposited from propylene or propane at ∼1250°C (1523 K):and for coatings deposited from methane at ∼2000°C (2273 K):where T is the absolute temperature.

Transport of caesium through a nuclear graphite. part I. Microgravimetric studies and electron probe microanalysis

Adsorption of caesium (≈40 mg/g maximum) on a gilsonite graphite at 473 K and subsequent desorption in the range 973–1373 K have been followed in a vacuum microbalance and caesium concentration profiles in the graphites have been measured by electron probe microanalysis at stages in the adsorption-desorption programme. An analysis is developed which enables apparent diffusion coefficients, D, to be determined from desorption rates. Electron probe microanalysis provides evidence for two-phase or multi-phase diffusion of caesium in the graphites during adsorption and desorption and there is evidence that diffusion of caesium is sensitive to the thermal history of graphite. The variation of all reported values of D (m 2/s) with temperature is log D = −6.34 − 5450 T . The limitations of the method of analysis due to nonuniform caesium concentrations, finite surface exit resistance and multi-phase diffusion are also considered.

Metallic fission product migration in coated fuel particles

Experimental and theoretical methods are discussed which can be used to derive a complete set of diffusion data in coated particles and to perform coated particle release calculations. Numerous results on Cesium transport behaviour in kernels and coatings are communicated and compared with reference data. Methane derived coatings exhibit Cs-diffusion coefficients which are for temperatures up to 1400°C more than two orders of magnitude lower than those of propene derived coatings. There are some indications that a fluence of 2.5 · 10 21 cm −2( E > 0.1 MeV) increases Cs diffusion in propene coatings, while it leaves methane coatings unaffected. This could be caused by irradiation induced structural changes. Cs-migration in fuel kernels is complex and not completely understood. All diffusion data have to be checked under irradiation conditions.

Charge pulse studies of transport phenomena in bilayer membranes. I. Steady-state measurements of actin- and valinomycin-mediated transport in glycerol monooleate bilayers.

A charge pulse technique has been applied to studies of transport phenomena in bilayer membranes. The membrane capacitance can be rapidly charged (in less than a microsecond). The charge then decays through the membrane's conductive mechanism-no current flows through the solution or external circuitry. The resulting voltage decay is thus a manifestation of membrane and boundary layer phenomena only. There are a number of advantages to this approach over conventional voltage or current-clamp techniques: the rise-time of the voltage perturbation is not limited by the time constant deriving from the membrane capacitance and solution resistance, thus permitting study of extremely rapid rate processes; the membrane is exposed to high voltage for relatively short times and thus can be subjected to higher voltages without breakdown; the steady-state current-voltage behavior of the membrane can be deduced from a single charge pulse experiment; the charge (and therefore the integral of the ion flux through the membrane) is monitored allowing detection of rate processes too rapid to follow directly. In this paper we present what is primarily a steady-state analysis of actin (non-, mon-, din-, trin-)-mediated transport of ammonium ion and valinomycin-mediated transport of cesium and potassium ions through glycerol monooleate bilayers. We introduce the concept of the "intercept discrepancy", a method for measuring charge lost through extremely rapid rate processes. Directly observable pre-steady-state phenomena are also discussed but will be the main subject of part II.

Cesium kinetics in a montane lake ecosystem.

This study was initiated to determine the kinetics of cesium transport in East Twin Lake, a 5-ha, natural semi-drainage lake which lies at an elevation of 2880 m in the north-central Colorado Rockies. One kilogram of 133Cs (as 133CsCl) was introduced into the water of East Twin Lake on 15 September 1970. Samples of water, seston, sediment, amphipods, zooplankton, trout and two species of vegetation were obtained over a 393-day period following the dosing event. Stable cesium was measured by neutron activation analysis. The loss of 133Cs from water occurred in two phases. The rapid phase accounted for the loss of 60% of the cesium from water and had a loss half time of 0.5 days while the slow phase had a loss half time of 130 days. The seston fraction of each water sample contained from 25 to 80% of the 133Cs present in each liter of unfiltered water. Bottom sediments were identified as the major site of deposition of the 133Cs dose. The sediment, at 393 days post-dosing, accounted for 82% of the 133Cs inventory in the lake whereas water and seston accounted for only 3 and 14%, respectively. Amphipods and zooplankton reached equilibrium with the water within about 3 weeks after the 133Cs administration and achieved concentration factors (wet weight) of about 700 and 150, respectively. During mid-winter, however, these organisms showed increased concentrations of 133Cs with concentration factors ranging up to 3700 and 350 for amphipods and zooplankton, respectively. Trout accumulated the 133Cs more slowly than the invertebrates and reached a maximum concentration factor of about 5600 some 260 days following the dosing event. Absolute quantities as small as 10−8 g of 133Cs were detectable. Concentrations of 133Cs and fallout 137Cs in trout muscle were significantly correlated which indicated that the kinetic behavior of the isotopes in this component of the lake was similar. Furthermore, the stable tracer obviates the radiation protection problems that would arise from contaminating a public water with a radiosotope of cesium.

Active transport of caesium by the isolated and short-circuited midgut of Hyalophora cecropia.

ABSTRACT The short-circuited midgut from the larvae of Hyalophora cecropia can actively transport potassium and rubidium from blood side to lumen. In this paper it is demonstrated that caesium also can be actively transported. Transport of potassium does not interfere with the metabolism of the midgut; nor does transport of caesium. Potassium and rubidium compete for the transport mechanism in a one-to-one ratio but competition between potassium and caesium is more complicated. At high caesium:potassium ratios the active transport taking place is transport of caesium; when the ratio is 2 there is more transport of potassium than of caseium; when the ratio is i there is no transport of caesium.

Distribution of Cs 134 in Andropogon Scoparius Michx. Clones in Two Native Habitats

Cesium—134 distribution in native Andropogon scoparius clones and in single tillers indicates that each clone consists of a group of tillers each acting as individual plants. Two zones of concentration occur: the upper 5 cm of the roots and the inflorescence, including the florets. Cesium transport from the foliage to the upper portion of the roots occurs with fall dormancy. With the initiation of spring growth the mineral is exported from the roots to the expanding leaf blades. Cesium activity within the plants growing on the Heiden—Hunt clay soil decreases more with time than in plants growing on Tabor fine sandy loam.

Transport of caesium in frog muscle.

1. The entry of caesium into sartorius muscle cells is strongly suppressed by the presence of 10(-5)M strophanthidin in Ringer solution.2. The amount by which caesium entry is reduced in the presence of strophanthidin is dependent on the intracellular sodium concentration and is greater the higher the intracellular sodium concentration.3. The magnitude of caesium influx in the absence of strophanthidin is highly dependent on the intracellular sodium concentration.4. Caesium uptake by muscles in which sodium has been largely replaced by lithium is reduced to very low values.5. Caesium can promote the extrusion of sodium from muscles with high intracellular sodium concentrations. The effects of 25 mM caesium and 5 mM potassium on sodium extrusion are roughly the same.6. External potassium inhibits the entry of caesium ions into muscle cells presumably by competing for transport sites.7. The drug strophanthidin has no effect on (134)Cs efflux provided that muscles have been loaded with tracer ions for a long period of time. Caesium efflux from the intracellular compartment appears to occur by a process not mediated by metabolism.8. The action of strophanthidin on (134)Cs efflux from muscles exposed to tracer for short times suggests that caesium ions are transported inwardly by an active process after first accumulating in a superficial reservoir.

Erratum: Strophanthidin-Sensitive Transport of Cesium and Sodium in Muscle Cells

In the paper "Strophanthidin-sensitive transport of cesium and sodium in muscle cells," by R. A. Sjodin and L. A. Beauge [ Science 156, 1248 (2 June 1967)] line 10 of the legend to Fig. 2 should show that 25 m M of cesium, rather than 25 m M of potassium, was present in the Ringer fluid.

Strophanthidin-Sensitive Transport of Cesium and Sodium in Muscle Cells

Strophanthidin-Sensitive Transport of Cesium and Sodium in Muscle Cells

Strophanthidin-sensitive transport of cesium and sodium in muscle cells.

Uptake of cesium-134 ions into muscle cells is reduced to very low values by the presence of 10(-5)M strophanthidin in the Ringer solution. Cesium ions can induce extrusion of sodium from muscle cells in which the intracellular sodium content is elevated. The cesium-induced extra efflux of sodium-22 is inhibited by the external presence of 10(-5)M strophanthidin. The coupling between inward movement of cesium and outward movement of sodium appears to be chemical in nature. The evidence suggests that cesium ions are transported into muscle cells by a system of sites or carriers that requires a source of metabolic energy for ion turnover to occur.

Coupled Molecular Flow and Surface Diffusion. Application to Cesium Transport

The mechanisms of cesium transport through a cylindrical tungsten tube are now understood to consist of surface diffusion, molecular flow and ionic flow under the influence of electric fields which exist in the tube. In this paper an exact transport equation is developed for the idealized case of pure molecular flow coupled with surface diffusion. This takes the intractable form of a nonlinear integrodifferential equation of second degree. This is analytically reduced to a nonlinear form of Fredholm's integral equation suitable for solution by numerical iteration. The Langmuir adsorption and diffusion data for cesium on tungsten are introduced and the approximate domain of convergence for the integral equation is found by the use of an appropriate existence theorem. Sample solutions are shown including one which satisfies required boundary conditions at the orifices.

Deposition of Fallout Cesium 137 on Forage and Transfer to Milk

ESIUM 137 is one of the most important contaminants from fallout nuclear debris because of its long physical half-life and affinity for biological systems. Body burdens of this radionuclide in man result principally from the food-chain sequence: air and precipitation to plants, plants to milk and meat, with dairy and beef cattle as the principal vectors between plants and man's diet. This apparently simple relation describes the food-chain pattern for cesium 137 quite adequately since uptake of cesium 137 by plants from soil is negligible (1) and dairy products and beef contribute most of the cesium 137 in the average U.S. diet (2). Mathematical models describing the transport of radioactive fa,llout to milk, emphasizing strontium 90, have been presented (3-7). In these models, certain common assumptions were made regarding forage contamination and feeding practices, but actual data were unavailable. The relation between radionuclide levels of forage and milk has been reported by several workers for strontium 90 (8-12) and cesium 137 (13,14). The general relation between fallout, feeding practices, and milk levels has been discussed (15-18). A common deficiency of these models and discussions has been the absence of concomitant data for all three: fallout, feed, and milk. As pointed out in a recent panel discussion of approaches to studying radiological hazards in the environment, the large-scale monitoring network method and t,he investigation of specific ecosystems are complementary in understanding the behavior of fission products in the biosphere (19). Observations on the transport of cesium 137 in a controlled dairy ecosystem at Colorado State University were initiated in 1962, and data have been collected for the va.rious steps in the food chain. The ecotsystem consisted of one herd of 112 cows and an irrigated farm in a geographic region that would be classified as a dry area (20). From the study of this ecosystem, we believe that estimates of ceisium 137 body burdens of the general population can be significantly improved.

Analysis of the Ionization of Cesium in Tungsten Capillaries

The transport of cesium through a tungsten capillary occurs through two phases, an adsorbed layer and a vapor. In this analysis these two phases are connected by the experimentally observed relationship, rather than by any linearized approximation to it. The choice of allowed solutions is then made by a precise boundary matching to solutions computed for the surface onto which the capillary opens. This analysis leads naturally to the possible existence of three different states of the system over a range of capillary sizes, temperatures, and flow-rate conditions. These three states have been correlated with the front-surface emitting, pore emitting, and nonemitting states which have been observed to coexist for a porous ionizer. It is predicted that the coexistence of three different states will disappear when the capillaries become extremely fine.