Phase diagram for the Tl2Te-Bi2Te3 system

The phase equilibria in the Tl₂Te-Bi₂Te₃ system were studied by means of cooling curve determination, differential thermal analysis and X-ray diffraction methods; the results obtained with the former two methods were compared. The phase diagram established for the system differed considerably from three others published previously.

---

Zusammenfassung Mittels Differentialthermoanalyse, der Bestimmung der Abkühlungskurven und röntgendiffraktionsaufnahmen wurde das Phasengleichgewicht des Systemes Tl₂Te-Bi₂Te₃ untersucht. Die Ergebnisse ersterer beider Methoden wurden miteinander verglichen. Das für das System entwickelte Phasendiagramm weicht erheblich von drei vorangehend veröffentlichten Phasendiagrammen ab.

---

, l₂T-³ ₂₃. . .

---

---

The present work was financed by the Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wrocaw, from grant CPBP 01.12.     

Specificity of states of Cu2+ ions in ZSM zeolites due to the cooperative Jahn-Teller effect

Crystalline silicate of ZSM zeolite structure was synthesized via hydrothermal crystallization at large contents of copper. ESR spectra of Cu²⁺ ions stabilized in this system are determined by the specific ordering due to the cooperative Jahn-Teller effect of Cu²⁺ ions with the d_x ²–y² ground state.

---

423° ZSM . Cu(II), , - Cu²⁺ cdx²–y²— .

     

General equation for dissociative heterolytic reaction rates and corrections to the Br?nsted relationship

A general equation is proposed for the rates of halide and H⁺ ion transfer. A relay-type participation of H₂O in the transfer of H⁺ in aqueous solutions is substantiated.

---

: - H⁺. H₂O H⁺ .

     

Kinetics of reduction of iron ore—coal pellets

Kinetic data on the reduction of iron ore-coal pellets are compared with similar data for lump ore. It is shown that, when ore and coal are mixed intimately, the reduction reactions are accelerated considerably. Ore-coal pellets offer some additional advantages, as discussed in the text.It is shown that the kinetics of ore-coal reduction can be studied by using a pseudo kinetic parameter,f (fraction of reaction), defined as the instantaneous weight loss divided by the maximum possible weight loss. Plots off versust have been analysed to establish the kinetic equations and evaluate the kinetic parameters.

---

Zusammenfassung Die kinetischen Daten der Reduktion von Eisenerz-Kohle-Pellets wurde mit ähnlichen Daten von Stückerz verglichen. Es wurde gezeigt, daß die Reduktionsreaktionen im Falle einer intensiven Vermischung von Erz und Kohle erheblich beschleunigt werden. Erz-Kohle-Pellets besitzen einige zusätzliche Vorteile, auf die im Text näher eingegangen wird. Es wurde gezeigt, daß die Kinetik der Erz-Kohle-Reduktion mit Hilfe eines pseudokinetischen Parametersf (Reaktionsbruch) untersucht werden kann, der als Quotient aus aktuellem Gewichtsverlust und maximal möglichem Gewichtsverlust definiert wird. Zur Bestimmung der kinetischen Gleichungen und der Berechnung der kinetischen Parameter wurde einf–t Diagramm ausgewertet.

---

- . , , . . , - , g ( ), . f t .

     

3He induced nuclear reactions on237Np targets

The cross sections for the³He induced nuclear reactions on²³⁷Np leading to the formation of^236sNp,²³⁸Np,²³⁶Pu,²³⁷Pu,²³⁸Pu,²³⁷Am and²³⁹Am were studied by the irradiation of thin and thick targets of²³⁷Np. The cross sections were determined in the energy range of 20–26 MeV using the stacked-foil technique with thin targets. The cross sections were used for the calculation of the thick-target yields for the production of²³⁶Pu,²³⁷Pu and²³⁸Pu from²³⁷Np irradiated with³He²⁺ ions in the energy range of 20–26 MeV.     

Measurement of237Np in the marine environment of coastal nuclear sites in India

Nepturium-237 levels in sea water and sediments from Indian coastal waters receiving radwaste discharges have been investigated. The method used for the estimation is neutron activation and using this method,²³⁷Np activity as low as 10^–7 Bq/l in sea water could be measured. Neptunium-237 levels found are compared with the values reported for other areas.     

Estimation of <Superscript>235</Superscript>U concentration in some depleted uranium samples by high resolution gamma-ray spectrometry using 185 keV and 1001 keV gamma-energies of <Superscript>235</Superscript>U and <Superscript>234m</Superscript>Pa

The migration of ²³⁷Np in an undisturbed Chinese loess column was investigated by direct γ-ray method. The column was taken from a field test site and installed in a laboratory simulation hall. Radionuclide ²³⁷Np in the form of neptunium nitrate, mixed with quartz, was introduced into the column and covered with loess. Artificial rainfall was applied to the column for about 3 years and, the counting rates of ²³⁷Np in the column from 56 to 616 days at different vertical positions were detected with a γ-ray detection system. Based on the counting rates of ²³⁷Np in the simulation column at different vertical positions and the distance from the source layer, the relationship of the mass center of ²³⁷Np in the column at different experimental periods to the experimental time was established, C _m = 0.36 log(t)-2.75. Here C _m is the mass center of ²³⁷Np in the column, cm, and t is the experimental time in days. Based on this relationship, the mass center of ²³⁷Np for the 1,073-day experiment was predicted and compared to that obtained with the final destructive method. The good agreement between the prediction and the experimental values indicates that the direct γ-ray method could be used to predict the migration of strongly adsorbed radionuclides such as ²³⁷Np in environmental media with the help of laboratory simulation columns.     

Preparation of source and sealed absorber holder for237Np and238U Mössbauer measurements

Preparation of source and sample holder is described for the Mössbauer studies of²³⁷Np and²³⁸U. For the Mössbauer measurement of²³⁷Np, a source assembly with small sources of²⁴¹Am metal was developed taking account of the transport regulations for radioactive substances. The source assembly of²⁴¹Am showed a sufficient activity enough to measure the Mössbauer spectra of²³⁷Np. In order to handle²³⁷Np compounds safely, trebly sealed holders were designed which could encapsulate²³⁷Np samples without the seepage of liquid helium. A source for²³⁸U Mössbauer measurement was also developed from a highly pure²⁴²PuO₂.     

Determination of trace heavy metals associated with suspended particulate matter in pond water by microscale anodic stripping voltammetry

Summary Less than 1 milligram of suspended particulate matter in a 50-ml water sample was separated by centrifugation, decomposed with 22l of 21010 perchloric-nitric-hydrofluoric acid mixture, and analyzed for copper, lead, cadmium and zinc by microscale differential pulse anodic stripping voltammetry with a hanging mercury drop electrode in 300l of 0.06M perchloric acid. The procedure was simple and rapid, because a single Teflon microvessel was used throughout the whole procedure.

---

Bestimmung von Schwermetallspuren in suspendierten Teilchen in Teichwasser durch Anodic Stripping Voltammetry im Mikromaßstab

Zusammenfassung Weniger als 1 mg suspendierter Teilchenmaterie wurde durch Zentrifugieren abgetrennt, mit 22l eines Gemisches HClO₄HNO₃HF (21010) zersetzt und darin Cu, Pb, Cd und Zn durchDifferential-Pulse-Anodic-Stripping-Voltammetrymit hängender Hg-Tropfelektrode in 300 l 0.06M Perchlorsäure bestimmt. Das Verfahren ist einfach und schnell, es bedarf dazu nur eines Mikrokölbchens aus Teflon.

     

Anomalously high237Np in intertidal sediments from the Ribble Estuary in the Irish Sea

Depth profiles and inventories of²³⁷Np in sediment cores from the Ribble Estuary in the Irish Sea have been studied along with those of Pu isotopes,²⁴¹Am and¹³⁷Cs, to allow a more detailed look of anomalously high²³⁷Np content observed in this estuary previously. The comprehensive data obtained showed that the depth profiles of both²³⁷Np contents and²³⁷Np/^239,240Pu activity ratios were clearly different from those of^239,240Pu,²⁴¹Am, and¹³⁷Cs and their activity ratios. As much as 80–90% of²³⁷Np inventories (0.32–1.06 kBq/m²), found in three cores, were estimated to be derived from a source other than Sellafield, on the basis of comparison of the²³⁷Np/^239,240Pu inventory ratio (0.65–1.74%) found in the Ribble Estuary cores with those (0.10–0.16%) in the Ravenglass Estuary cores.     

Determination of237Np in spent fuel by use of inherent239Np as a chemical yield monitor

A method for analyzing the content of²³⁷Np in spent fuel has been developed using inherent²³⁹Np as a chemical yield monitor. After ion-exchange separations for the dissolved fuel solution, the²³⁷Np content in the neptunium fraction was determined from the activity of²³⁷Np or of²³³Pa, which is in radioactive equilibrium with²³⁷Np. The chemical yield in the separations was determined both from the content of²⁴³Am which is in radioactive equilibrium with²³⁹Np before the separations and from the²³⁹Np content in the neptunium fraction after the separations by alpha- and gamma-ray spectrometry.     

<Superscript>237</Superscript>Np in peat and lichen in Finland

Activity concentrations of ²³⁷Np in peat and lichen samples in Finland were determined and contributions from nuclear weapons testing in 1950–1960s and the Chernobyl accident were estimated. ²³⁷Np was determined with ICP-MS using ²³⁵Np as a tracer. Activity concentrations of ²³⁷Np in peat samples varied between 1.98 ± 0.05 and 14.1 ± 0.3 mBq/m². The contribution from the Chernobyl accident to the total ²³⁷Np deposition in peat was 0.1–13%, the Chernobyl-derived fraction of total ²³⁷Np in peat being much lower than the previously determined corresponding Chernobyl-derived fractions of ^239+240Pu, ²⁴¹Pu, ²⁴¹Am and ²⁴⁴Cm.     

Determination of technetium-99 and neptunium-237 in environmental samples by inductively coupled plasma mass spectrometry

New analytical techniques using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were applied to the determination of technetium-99 (Tc-99) and neptunium-237 (Np-237) in environmental samples. The determination of Tc-99 consists of a cyclohexanone solvent extraction method to eliminate the interference isobar (Ru-99). An anion exchange with acetic acid media and a TTA-xylene solvent extraction were used for the determination of Np-237. Technetium-95m and Np-239 were used as chemical recovery tracers in these methods. The concentrations of Tc-99 and Np-237 in the typical surface soil samples in Japan ranged form 8.1×10² to 1.8×10^–1 Bq/kg-dry, from 3.3×10^–3 to 8.0×10^–3 Bq/kg-dry, respectively.     

Neptunium determination by inductively coupled plasma mass spectrometry (ICP-MS)

The determination of neptunium-237 (²³⁷Np) traditionally has been performed by alpha spectrometry or neutron activation analysis. These methods are labor intensive and require several days for completion. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a possible alternative for²³⁷Np determinations. This paper describes the analytical method developed for samples that have significant levels of uranium present. The lower reporting limits achievable by ICP-MS are competitive with the counting methods, but the real advantage for this laboratory lies in the lower cost and faster turnaround time provided by ICP-MS.     

Migration mechanisms of 237Np and 241Am through loess media

Migration experiments with ²³⁷Np(V) and ²⁴¹Am(III) have been performed using a column system, packed with loess, taken from Shanxi, China. The adsorption mechanism of ²³⁷Np and ²⁴¹Am on the loess was examined by a chemical extraction method. Most of ²³⁷Np was adsorbed on the influent edge of the column, and the adsorbtion was mainly controlled by surface complexation. However, the migration of ²³⁷Np in loess media could be roughly evaluated by the distribution coefficient. In the case of ²⁴¹Am, particulate, the ²⁴¹Am species was formed in the influent solution and moved in the column. The ²⁴¹Am adsorbed on loess was controlled by irreversible reactions. The migration behavior of particulate ²⁴¹Am in loess media could be expressed by the filtration theory.     

An intercomparison exercise on the determination of neptunium-237 in an environmental material

An intercomparison exercise has been carried out on the measurement of²³⁷Np in a sample of sea-born sediment taken from the estuary of the River Esk in Cumbria, United Kingdom. The sediment had been contaminated by radioactive liquid discharges from the nuclear fuels reprocessing plant at Sellafield. The measure of agreement between the submitted values was such that one would accept with confidence²³⁷Np analyses reported by the participating laboratories. The exercise was arranged by the Analysts' Informal Working Group (AIWG). The AIWG is a small group of chemists from several Government laboratories in the United Kingdom having an interest in radionuclides in the environment. From time-to-time the Group arranges intercomparison exercises; these exercises are in addition to the members' normal quality assurance schemes, and in addition to intercomparison exercises arranged by other organizations. So far as the authors are aware, there has been no report of such an exercise involving²³⁷Np, and there appear to be no natural matrix reference materials available for environmental²³⁷Np.     

Synthesis ofα-nitromethylpyridine and derivatives

-Nitromethylpyridine and -nitromethyl-ß-ethylpyridine are obtained by treating the corresponding nitrophthalones with 10% aqueous alkali. Treatment of the compounds with bromine gives the hydrobromides of the dibromo derivatives, which on treatment with aqueous sodium bicarbonate solution give the corresponding bases. Addition products of -nitromethylpyridine at the double bond of chalcone and 2-benzylidenindan-1,3-dione were obtained.     

Holdup measurements on an SRNL Mossbauer spectroscopy instrument

Gamma-ray holdup measurements of a Mossbauer spectroscopy instrument are described and modeled. In the qualitative acquisitions obtained in a low background area of Savannah River National Laboratory, only Am-241 and Np-237 activity were observed. The Am-241 was known to be the instrumental activation source, while the Np-237 is clearly observed as a source of contamination internal to the instrument. The two sources of activity are modeled separately in two acquisition configurations using two separate modeling tools. The results agree well, demonstrating a content of (1980 ± 150) μCi Am-241 and (110 ± 50) μCi of Np-237.     

A simple and economic method for accurate determination of the energy peak efficiency of 208 keV γ-ray of 237U based on 241Pu/237U secular equilibrium

A new method is developed for the determination of energy peak efficiency of 208 keV γ-ray of ²³⁷U based on ²⁴¹Pu/²³⁷U secular equilibrium. Plutonium solution was purified to remove Am with Dowex 1 × 2 anion exchange chromatography and the concentration of ²⁴¹Pu in the purified solution was determined using ²⁴²Pu isotope-dilution mass spectrometry on an inductively-coupled plasma mass spectrometry. The solution can be used as calibration source for the determination of energy peak efficiency of 208 keV γ-ray of ²³⁷U after 48 days. The method was validated for a planar HPGe detector at the 12 mm above the detector surface. The results showed that this is a simple and economic method for determining the energy peak efficiency of gamma detectors for 208 keV γ-ray of ²³⁷U.     

Reliable determination of 237Np in environmental solid samples using 242Pu as a potential tracer

This paper reports an analytical method for rapid determination of neptunium (²³⁷Np) in environmental solid samples exploiting automated sequential injection (SI)-based anion exchange separation. Pivotal issues on analytical method performance were investigated including sorption behavior of ²³⁷Np onto various AG 1-type anion exchangers; suitability of ²⁴²Pu as a tracer for ²³⁷Np determination in environmental solid samples; and long-term chemical stability of tetravalent Np. Experimental results revealed that the degree of resin cross-linking has a significant influence on the separation efficiency in terms of chemical yields of ²³⁷Np and removal of interfering nuclides. Although ca. 30% of sorbed Np onto AG 1-×4 was stripped out during HCl rinsing step for the removal of Th, chemical yield ratios of ²³⁷Np to ²⁴²Pu were proven steady with an average value of 0.67 ± 0.04 (n = 15) under selected experimental conditions. Disulfite-8 M HNO₃ was selected as a redox pair for valence adjustment to Np(IV) and the tetravalent Np in the sample solution was demonstrated to be stabilized for up to 5 days under 3 °C. The analytical results for reference materials showed a good agreement with the expected values, thereby demonstrating the usefulness of ²⁴²Pu as a non-isotopic tracer for ²³⁷Np chemical yield monitoring. The on-column separation procedure fosters rapid analysis as required in emergency situations since each individual sample can be handled within 2.5 h, and leads to a significant decrease in labor intensity compared to conventional batch-wise protocols.