Use of Radioactive Tracers for Studies on Fluidized Cracking Catalytic Plants

In this paper are described the experiments carried out with radioactive tracers on Fluidized Cracking Catalytic (F.C.C.) plants. The tracers used are ⁴¹Ar and ⁷⁹Kr for gas and ¹⁴⁰La for the catalyst. Results obtained on different parts of the F.C.C. plant are given.     

Bestimmung von Diffusionskoeffizientcn an Autoradiogrammen mit Hilfe von Schwärzungsmomenten

Zur experimentellen Bestimmung des Diffusionskoeffizienten in Festkörpermaterialien werden sehr häufig autoradiographische Verfahren in der Radionuklid-Tracertechnik angewendet. Bedingt durch die autoradiographische Abbildung ist es im allgemeinen nicht möglich, den Diffusionskoeffizienten direkt aus dem Schwārzungsverlauf des Autoradiogramms abzulesen.

Aus diesem Grunde wurde ein mathematisches Verfahren entwickelt, das den Diffusionskoeffizienten in Abhängigkeit von Schwärzungsmomenten liefert, die nach einer bestimmten Vorschrift zu bilden sind. Die Lösung der autoradiographischen Abbildungsgleichung konnte dabei umgangen werden.

Das Verfahren wird an einem typischen Beispiel erläutert.     

Experimentelle und theoretische Behandlung von Flüssig-Flüssig-Extraktionsgleichgewichten

Am Beispiel einer Kationenaustauschextraktion mit n-Caprylsäure werden die thermodynamische Behandlung von Extraktionsgleichgewichten dargelegt und die Methoden zur Auswertung experimenteller Ergebnisse diskutiert. Es wird über die Einsatzmöglichkeiten der Extraktionsapparatur AKUFVE bei derartigen Untersuchungen berichtet.     

Vergleich von kinetischen Daten des N-Stoffwechsels im Ganzkörper von Läufern und Läuferinnen

Mil Hilfe der ¹⁵N-Tracertechnik wurde der N-Stoffwechsel von je 6 Läufern und Läuferinnen charakterisiert. Als Tracersubstanz wurde [¹⁵N]Glycin eingesetzt. Die tracerkinetischen Daten, die sich aus der Ausscheidung des lsotops im Urin ergeben, wurden unter Verwendung der Priming-Technik vermittelt. Die Parameter dcs Proteinstoffwechscls wurden auf der Grundlage eines 3-Pool-Stoffwechselmodells herechnet. Die experimentellen Ergebnisse werden diskutiert.

The N-metabolism of 6 male and 6 female runners are characterized with the help of the ¹⁵N tracer technique using [¹⁵N]glycine as a tracer substance. The tracer kinetic data coming from the excretion of the isotope in the urine were determined using the priming technique. The parameters of the protein metabolism were calculated on the basis of a 3-pool model. The experimental results are discussed.     

Investigation of Moisture Migration in the Concrete of a Special Test Construction under Simulated Load Conditions

Investigations of the behaviour of water in the concrete of special constructions under load conditions are essential for judging safety aspects especially when the concerto is enclosed between liners. The injection of tritiated water of 60 Ci into the fresh concrete of the dome range of a test construction, sampling and sample preparations are described. The test results obtained again demonstrate the unique possibilities of the tracer technique with radionuclides in the investigation of local and temporal distributions of substances under complicated actual conditions.     

Über die Organisation der Produktion von Isotopen,Kernstrahlungsquellen, Radioisotopengeräten für die technologische Kontrolle und Anlagen für die Strahlentechnik in der UdSSR sowie über die Organisation ihrer Einführung in die Volkswirtschaft

Es werden flogende Fragen zur Produktion von Isotopen, Kernstrahlungsquellen und Radioisotopengeräten in der UdSSR behandelt: das Sortiment in der Isotopenproduktion und der Isotopentechnik; die Planung und Spezialisierung der industriellen Fertigung von Isotopenerzeugnissen und isotopentechnischen Gerāten; volkswirtschaftliche Überlegungen dazu; Anwendung und Ausbildung für die Anwendung der Atomenergie.     

Application of chlorine-36 technique in determining the age of modern groundwater in the Al-Zulfi province,Saudi Arabia

The present study aims to estimate the residence time of groundwater based on bomb-produced ³⁶Cl. ³⁶Cl/Cl ratios in the water samples are determined by inductively coupled plasma mass spectrometry and liquid scintillation counting. ³⁶Cl/Cl ratios in the groundwater were estimated to be 1.0–2.0?×?10^?12. Estimates of residence time were obtained by comparing the measured bomb-derived ³⁶Cl concentrations in groundwater with the background reference. Dating based on a ³⁶Cl bomb pulse may be more reliable and sensitive for groundwater recharged before 1975, back as far as the mid-1950s. The above ³⁶Cl background concentration was deduced by determining the background-corrected Dye-3 ice core data from the frozen Arctic data, according to the estimated total ³⁶Cl resources. The residence time of 7.81?×?10⁴ y is obtained from extrapolated groundwater flow velocity. ³⁶Cl concentration in groundwater does not reflect the input of bomb pulse ³⁶Cl, and it belongs to the era before 1950.     

Viscoelasticity and diffusion in miscible blends of saturated hydrocarbon polymers

Linear viscoelasticity and tracer diffusion were investigated as functions of temperature, component molecular weight and blend composition for entangled, single-phase blends of nearly monodisperse poly(ethylene-alt-propylene) (PEP) and head-to-head polypropylene (HHPP). Both components are non-polar and, despite evidence for slight differences of component glass temperatures in their blends, the viscoelastic data obey time-temperature superposition rather well. The properties of the blends were compared at constant T-T _g (blend) with predictions of the tube-model theories. The composition dependence of viscosity agrees best with the double-reptation prediction, as had been found earlier for molecular weight blends. The variation in plateau modulus with composition is consistent with reptation, but the changes are too small to provide a definitive test. The tracer diffusion coefficients, D ^* _PEP and D ^* _HHPP are nearly independent of composition, consistent with the reptation prediction and in sharp contrast with tracer diffusion for blends with specific associations. Results for the recoverable compliance depart from this pattern, varying differently and much less strongly with composition than the predictions of either single or double reptation. It thus seems that microstructural blends may behave in significantly more complex ways than molecular weight blends even for components with only weak dispersive interactions and rather modest differences in glass temperature and plateau modulus.Dedicated to Prof. John D. Ferry on the occasion of his 85th birthday.     

New Considerations on Analytical Solutions Employed in Tracer Flow Modeling

A methodology commonly used to obtain analytical and semi-analytical solutions to describe spike and finite-step tracer injection tests is discussed. In these cases, solutions to the diffusion–convection equation are derived from the solution of a different problem, namely the continuous injection of a tracer. Within this procedure, spike injection results from the time derivative of this solution, and finite-step injection from the superposition of two solutions shifted in time. In this paper we show that although this methodology is mathematically correct, attention should be paid to the properties of the solutions. Their boundary conditions may not represent physically acceptable situations, since these conditions are inherited from a different problem. The application of the methodology to a simple one-dimensional case of a tracer pulse diffusing in a homogeneous, semi-infinite reservoir shows serious problems regarding boundary conditions and mass conservation. These problems has not probably been found before since tracer breakthrough curves are not very sensitive to them. However, the problems clearly show up when the tracer distribution in space is analyzed. We conclude that the traditional methodology should not be employed. Equations should be solved imposing the specific boundary and initial conditions corresponding to the original system under consideration.     

Evidence of Multi-Process Matrix Diffusion in a Single Fracture from a Field Tracer Test

Compared to values inferred from laboratory tests on matrix cores, many field tracer tests in fractured rock have shown enhanced matrix diffusion coefficient values (obtained using a single-process matrix-diffusion model with a homogeneous matrix diffusion coefficient). To investigate this phenomenon, a conceptual model of multi-process matrix diffusion in a single-fracture system was developed. In this model, three matrix diffusion processes of different diffusion rates were assumed to coexist: (1) diffusion into stagnant water and infilling materials within fractures, (2) diffusion into a degraded matrix zone, and (3) further diffusion into an intact matrix zone. The validity of the conceptual model was then demonstrated by analyzing a unique tracer test conducted using a long-time constant-concentration injection. The tracer-test analysis was conducted using a numerical model capable of tracking the multiple matrix-diffusion processes. The analysis showed that in the degraded zone, a diffusion process with an enhanced diffusion rate controlled the steep rising limb and decay-like falling limb in the observed breakthrough curve, whereas in the intact matrix zone, a process involving a lower diffusion rate affected the long-term middle platform of slowly increasing tracer concentration. The different matrix-diffusion-coefficient values revealed from the field tracer test are consistent with the variability of matrix diffusion coefficient measured for rock cores with different degrees of fracture coating at the same site. By comparing to the matrix diffusion coefficient calibrated using single-process matrix diffusion, we demonstrated that this multi-process matrix diffusion may contribute to the enhanced matrix-diffusion-coefficient values for single-fracture systems at the field scale.