A radioactive tracer dilution method to determine the mass of molten salt

A new technique for molten salt mass determination, termed radioactive tracer dilution, that uses ²²Na as a tracer was validated at bench scale. It has been a challenging problem to determine the mass of molten salt in irregularly shaped containers, where a highly radioactive, high-temperature molten salt was used to process nuclear spent/used fuel during electrochemical recycling (pyro-processing) or for coolant/fuel salt from molten salt reactors. A radioactive source with known activity is dissolved into the salt. After a complete mixture, a small amount of the salt is sampled and measured in terms of its mass and radioactivity. By finding the ratio of the mass to radioactivity, the unknown salt mass in the original container can be precisely determined.

     

Determination of the ion-adsorption on the AgBr systems by the radioactive tracer technique

Summary The influence of the concentration of ionic and nonionic organic molecules and inorganic ions on the adsorbability of Eu³⁺ ions on the AgBr precipitates is described. It was found that the concentration of the inorganic as well as the concentration of organic molecules in the systems has a great influence on the adsorption of Eu³⁺ ions. Electromicrographs show that the dispersity of AgBr precipitates strongly depends on the concentration of the nonionic organic molecules present in the systems. At higher concentration of these molecules the particles of AgBr become very small and the adsorption of Eu³⁺ ions increases. Adsorption equilibrium between Eu³⁺ ions and organic and inorganic ions has been determined. Eu³⁺ ions can be desorbed from the precipitates if the concentration of organic and inorganic ions are high enough.

---

Zusammenfassung Es wird der Einfluß von ionogenen und nichtionogenen organischen Molekülen und anorganischen Ionen auf die Adsorbierbarkeit von Eu³⁺-Ionen an AgBr-Niederschlägen untersucht.EM-Aufnahmen zeigen, daß die Größenverteilung der AgBr-Partikel von der Konzentration der nichtionogenen organischen Moleküle in der wäßrigen Lösung stark abhängt. Bei großer Konzentration sind die AgBr-Partikel sehr klein, und die Adsorption ist sehr hoch. Das Adsorptionsgleichgewicht zwischen anorganischen und organischen Ionen wurde bestimmt.Die Ergebnisse weisen auf volle Desorption von Eu³⁺-Ionen aus den Niederschlägen bei einer ausreichend großen Konzentration der anorganischen und organischen Ionen hin.

---

---

With 4 figures     

Determination of ion adsorption by radioactive tracer technique

Summary The slight linear decrease of the “per mole of AgI adsorbed amount” (ˉC) of the coagulating ion with the increasing pI at a constant concentration of the coagulating ion was proved and explained by the linear decrease of the specific surface. The adsorbed amount of the coagulating ions at a constant concentration and at a given pI decreases with the increasing concentration in which the AgI precipitate was formed. Ions of different valencies are adsorbed in equivalent amounts which are independent of their concentrations which were higher than their coagulation values. The correctness of the desorption-adsorption formula logc″/c′=(z′−z″ a+ logx/(−x) respectivelyS=c″ (1−x)/c′x= 10(z′−z″)a was confirmed (x the fraction of the adsorbed amount of the ion of valencyz″ and concentrationc″, 1−x the fraction of the adsorbed amount of the ion of valencyz′ and concentration c′,S the selectivity coefficient of ion exchangers). Therefore the coagulated AgI can be considered as an ideal ion exchanger. The constanta in the above formula is equal to the slope of the line “log coagulation value-valency” of theSchulze-Hardy rule.

---

Zusammenfassung Die leicht lineare Abnahme des pro Mol AgJ adsorbierten Betrages (ˉC) der koagulierenden Ionen mit steigendem p^J bei konstanter Konzentration des koagulierenden Ions wurde gezeigt und durch die lineare Abnahme der spez. Oberfl?che erkl?rt. Der adsorbierte Betrag an koagulierenden Ionen bei konstanter Konzentration und gegebenem p^J sinkt mit steigender Konzentration, mit der die AgJ-F?llung erzeugt wird. Ionen verschiedener Wertigkeiten werden in ?quivalenten Betr?gen unabh?ngig von ihren Konzentrationen adsorbiert und sind h?her als ihre Koagulationswerte. Die Richtigkeit der Desorption-Adsorptions-Formel logc″/c′=(z′−z″ a+logx/(−x) bzw.S=c″ (1−x)/c′x= 10(z′−z″)a wurde sichergestellt (x= Bruchteil des adsorbierten Betrages des Ions der Valenzz″ und dessen Konzentrationc″, 1 −x=Bruchteil des adsorbierten Betrages des Ions der Valenzz′ und der Konzentration c′,S=Selektivit?tskoeffizient des Ionenaustauschers). Deshalb kann das koagulierte AgJ als ein idealer Ionenaustauscher betrachtet werden. Die Konstantea in der obigen Formel ist gleich der Neigung der Kurve “log Koagulationswert/Valenz” in derSchulze-Hardy-Regel (2).

---

---

Contribution number 95 from the Department of Physical Chemistry, Faculty of Sciences, University of Zagreb. Partially reported at the I. Yugoslav Congress for Pure and Applied Chemistry, Zagreb, June 1960.     

Application of a radioactive tracer method to copper migration in Semiconductor Lithography

Radioactive tracer technique was applied to examine the migration of Cu impurity from ArF and KrF photoresists onto silicon-based underlying substrates of Si(100), Si(110), Si(111), poly-Si, SiO₂ and Si₃N₄. The effects of the polymer constituent in the photoresists and the baking temperature were studied. Results showed that the migration ratio of Cu from ArF photoresist was always exceeded that from KrF photoresist, independently of the substrate types and baking temperatures. The benzene ring in the KrF photoresist confined the Cu migration, while the alicyclic constituent in the ArF photoresist could not. The migration process of Cu from the bulk region into the interface region was discussed. The residual solvent in the bulk region influenced the Cu migration. The electronegativity of Cu explained the accumulation of Cu on wafer surface. Simple diffusion model was tried to explain the migration ratios, but the model did not explain it well due to the change of the photoresist medium during baking. A correlation function was proposed to modify the diffusion coefficient for describing the experimental observation of migration ratios.     

Calibration of alkyl-substituted fluorocyclopropanes on gas chromatographic columns by radioactive tracer techniques

A new method utilizing a radio-gas chromatographic system, for the calibration of various gas chromatographic columns with less than 10⁻¹²M of tritium-labelled samples is described. The minimum detectable level of³H,³⁸Cl,¹⁸F,^80mBr,⁸²Br,³⁵S and¹⁴C labelled compounds employed for column calibration is discussed. In addition, the relative retention times of nine previously unpublished alkyl-substituted fluorocyclopropanes on five gas chromatographic columns are given.     

Investigation of cobalt sorption on polyethylene using an in situ radioactive tracer method

Experiments on sorption of cobalt onto polyethylene foil from buffered borate solutions are reported in this paper. Sorption isotherms and sorption kinetics of cobalt as a function of pH and the effect of borate species on cobalt sorption were investigated. The results show that the extent of cobalt sorption is lower in borate buffer than in Na ClO₄ solution. It is found that the adsorption isotherms obtained are dependent on the pH of the solution. Possible reasons of the influence of pH on the sorption isotherms are discussed.     

Study of the surface properties of titanium hydroxide using a radioactive tracer technique

The surface properties of titanium hydroxide precipitates, formed under different conditions were studied in the presence of carrier-free radioactive⁸⁹Sr. It was found that titanium with concentrations equivalent to 24 mg TiO₂/litre, was enough to remove by adsorption more than 95% of the carrier-free strontium activity from an alkaline solution (pH≈13) in less than 6 hrs, regardless of whether the precipitate was freshly prepared or aged for a few days. If the precipitate was formed in situ, at the above pH value, the percentage removal of the strontium activity from the solution was even greater, and this was attributed to an internal adsorption process. At a lower pH value (∼2.5), however, the adsorption of strontium activity by titanium hydroxide was very low (<5%), whether the precipitate was preformed or formed in situ. The increase in the adsorption ability of titanium hydroxide precipitate on going from low pH (2. 5) to higher values was attributed to the inversion of the charge of titanium hydroxide sols from cationic particles at pH 2. 5 to negatively-charged particles at pH>3. 5, these latter particles adsorbing any positive strontium ions in solution.     

Influence of the column radial heterogeneity on the determination of single-component isotherms by the elution by characteristic point method

The influence of the column radial heterogeneity on the determination of equilibrium isotherm data by the elution by characteristic point (ECP) method is studied using nondimensional numerical calculations and taking into account typical radial distributions of the mobile phase flow velocity and the column efficiency across a column. Overloaded elution peaks were calculated with the equilibrium-dispersive model as a function of four dimensionless parameters, the number of theoretical plates at the center of the column, the Langmuir equilibrium constant, the retention and the loading factors. The influence of the mass transfer resistances and the radial heterogeneity of the column on the ECP data was analyzed by comparing the true isotherm and the one estimated from the diffuse profile of overloaded peaks. The results provide information on the accuracy of the ECP method. The error made increases with increasing degree of radial heterogeneity. This error can be corrected by using the results of the nondimensional numerical calculations, allowing a further extension of the applicability of the ECP method.     

Co-separation of hafnium with zirconium oxychloride using175,181Hf as radioactive tracer

Co-separation of hafnium with zirconium oxychloride has been studied from 0 to 60°C with the help of^175,181Hf. It was found that zirconium oxychloride undergoes two transitions, one at about 33°C and another at about 59.5°C. From the value of the partition factor it was clear that a separation method based on fractional crystallisation of the oxychloride will not be a successful line of approach. The transition points were verified by DTA study. It was found from the DTA curve that hafnium oxychloride undergoes transition near 90°C. The solubility of zirconium oxychloride and the break in the partition factor also corroborate the above findings.     

Investigation of ion adsorption on silver sulfide,iodide and bromide precipitates by the radioactive tracer technique

The radioactive tracer method was used to investigate the adsorption of iodide and europium ions from aqueous solution on dried isoelectric precipitates of silver sulfide, silver iodide and silver bromide. The relationship between the amount of iodide ions adsorbed on Ag₂S and the iodide ion and HNO₃ concentrations in the solution was determined. It was shown that the iodide ions adsorbed on Ag₂S could be desorbed with sulfide ions. Using Ag₂S, AgI and AgBr precipitates, a relationship between the europium ion adsorption and Eu(NO₃)₃, H₂S, NaI, NaBr and NaCl concentration in solution was established. The adsorption of europium ions was also assessed in respect to the presence of lanthanum and barium ions. For adsorption measurement iodide and europium ions were labeled with their radioactive isotopes and the amounts adsorbed were determined from the measured radioactivities of the precipitates after reaching the equilibrium between the solid phase and the solution.     

Use of65Zn as a radioactive tracer in the bioaccumulation study of zinc byPoecilia reticulata

The bioaccumulation of zinc byPoecilia reticulata from water as well as the elimination of the metal previously absorbed were determined by using⁶⁵Zn as radioactive tracer. The exposure time varied from 18 days to 30 days. The results obtained show that the absorption and elimination of zinc byPoecilia reticulata is slow, 30 days being necessary for the elimination of 70% of the previously absorbed zinc. The same experiment was also carried out by feeding fish with⁶⁵Zn contaminated food. The results obtained show that in 30 days only 40% of the zinc previously absorbed is eliminated by the fish.     

Effect of heterogeneity on the quantitative determination of trace elements in concrete

Laser-induced breakdown spectroscopy has been used for quantitative measurement of trace elements, e.g. sulfur and chlorine, in concrete. Chloride and sulfate ions have a large effect on the durability of concrete structures, and quantitative measurement is important for condition assessment and quality assurance. Concrete is a highly heterogeneous material in composition and grain-size distribution, i.e. the spatial distribution of elements. Calibration plots were determined by use of laboratory-made reference samples consisting of pressings of cement powder, hydrated cement, cement mortar, and concrete, in which the heterogeneity of the material is increasing because of the aggregates. Coarse aggregate and cement paste are distinguishable by the intensity of the Ca spectral lines. More advanced evaluation is necessary to account for the effect of the fine aggregate. The three series of reference samples enable systematic study of the effects of heterogeneity on spectral intensity, signal fluctuation, uncertainty, and limits of detection. Spatially resolved measurements and many spectra enable statistical evaluation of the data. The heterogeneity has an effect on measurement of the sulfur and chlorine content, because both occur mainly in the cement matrix. Critical chloride concentrations are approximately 0.04% (m/m). The chlorine spectral line at 837.6 nm is evaluated. The natural sulfur content of concrete is approximately 0.1% (m/m). The spectral line at 921.3 nm is evaluated. One future application may be simultaneous determination of the amount of damaging trace elements and the cement content of the concrete.     

Separation and determination of radioactive caesium in milk

A method is given for the separation and determination of radiocaesium in fluid milk. Caesium is separated from organic material and interfering ions by passage of the milk sample through a cation-exchanger in the lithium form. It is eluted from this column with 6M hydrochloric acid. Two methods are given for the recovery of radiocaesium from the eluate. It may be precipitated with silico-tungstic acid and then converted into caesium perchlorate for counting or weighing. Alternatively, the eluate is passed through a small column of ammonium phosphomolybdate, which quantitatively sorbs the radiocaesium, the activity of which is determined by putting the column in a well-type scintillation counter and measuring the activity. Approximately 90% of the radiocaesium is recovered.     

Radiochemical determination of cadmium isotopes in radioactive debris

(109)Cd and (113m)Cd were produced in a high altitude nuclear explosion during 1962. Analysis of filters from aircraft and balloon samplers enables the products of this single detonation to be traced. A radiochemical procedure is presented which allows determination of the cadmium radionuclides in the course of a sequential analysis for fission products and activation products from nuclear weapons tests. The sensitivity, recovery and decontamination from other radionuclides are adequate.