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Abstract  

Plutonium isotopes were measured by alpha-spectrometry and ICP-MS in sediment samples from two European lakes: Blelham Tarn in U.K. and Stechlin lake in Germany. The ICP-MS measurements were made after alpha-spectrometry counting of the planchets. The planchets were prepared by traditional electrodeposition method after radiochemical extraction, separation and purification of the Pu fraction. A short radiochemical separation using plutonium selective resin, between the two spectrometry measures, is presented. The results show that these two complementary methods are in good agreement, the plutonium activity concentrations are the same. Alpha-spectrometry allows the 238Pu determination and ICP-MS individual measurement of 239Pu and 240Pu. 238Pu/239+240Pu and 240Pu/239Pu ratios are calculated to determine the plutonium contamination source. With the results of these two techniques, it could be demonstrate that the plutonium is of global fallout origin.

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Abstract  

Light metal alloys, as aluminium- and titanium based alloys, are of great interest to aerospace industry but thermodynamic information, mainly heat capacity, is often missing. Then we measured on heating the heat content of seven industrial titanium alloys from room temperature to 600°C with the help of a high-temperature Calvet calorimeter (drop method). Their heat capacities were deduced by derivation of the enthalpy with respect to temperature. The departures from Kopp-Neuman law were calculated.

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Abstract  

A radiochemical separation is presented for americium, plutonium and neptunium from sediment samples by using an unique anionic exchange process. An oxidation-reduction step was introduced in the classical procedure of the radiochemical determination of transuranic elements in order to control the valence of the separated elements.

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Abstract  

Nickel-63 is a low energy beta-emitter needing a radiochemical separation before β-counting. Several papers described the separation and the detection of 63Ni in environmental samples. The method used in our work was first developed by Skwarzec and Holm. The main steps of this separation are the selective precipitation of nickel with dimethylglyoxime (DMG) and the use of the non-sorption of nickel on anion resin in hydrochloric acid solutions. In this paper, a new step is added to eliminate high quantities of calcium and magnesium phosphate disturbing the iron hydroxide precipitation step. The procedure has been applied to soft water samples: sediments, plants and fishes. The chemical yields are 60, 70 and 20%, respectively. The detection limit of 63Ni by liquid scintillation spectrometer is 10 mBq.

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Abstract  

We report in this paper the results of our thermal and thermodynamic investigation on lithium cyclohexaphosphate, Li6P6O18·5H2O between 298 and 1007 K. The different transitions with respect to temperature (successive dehydrations, solid-solid transition and melting) were studied with the help of differential thermal analysis and thermogravimetry. The different phases were characterized by X-ray diffraction and by infrared absorption. Finally, the enthalpy of these phasesvs. temperature was measured by isothermal drop calorimetry. Their heat capacities as well as the enthalpies of dehydration, of solid-solid transition and of melting were deduced. We pointed out that the lithium cyclohexaphosphate loses a molecule of water at 333 K (54.3 kJ·mol−1), three molecules of water at 413 K (151 kJ·mol−1) and the last one at 488 K (50.6 kJ·mol−1). The anhydrous lithium cyclohexaphosphate, Li6P6O18, give the polyphosphate, LiPO3, at 708 K (second order transition) and melt at 933 K (24.6 kJ·mol−1).

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Résumé  

On applique l'activation neutronique aux mesures d'abondance isotopique du rhénium dans les matériaux lunaires. On y parvient en comparant les activités induites par (n, γ) de186Re et188Re au moyen des raies γ de respectivement 137 et 155 keV. Afin d'éviter les interférences, (spécialement celles de199Au et99mTc) on a besoin d'un procédé conduisant à une grande pureté radiochimique. De plus, on détermine les teneurs en rhénium et tungstène. On a remarqué une anomalie isotopique du rhénium dans les échantillons d'Apollo-14, montrant un enrichissement remarquable en187Re (de 1,4 à 1,8% dans les sols et jusqu'à 29% dans les brèches). On montre enfin que cet enrichissement est partiellement dû à l'irradiation neutronique sur la surface lunaire par la réaction186W(n,γ)187W
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\mathop {\beta ^ - }\limits_ \to$$ \end{document}
187Re. Cependant, l'anomalie observée, causée principalement par les neutrons intermédiaires, n'est pas produite uniquement par les neutrons lunaires. L'activation d'un réacteur y contribue aussi par la réaction:186W(n,γ)187W
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\mathop {\beta ^ - }\limits_ \to$$ \end{document}
187Re(n,γ)188Re, qui peut être corrigée par l'analyse d'étalons de tungstène irradiés simultanément. On estime que la contribution lunaire à l'enrichissement du187Re est de 20 à 60% de l'excès total observé.
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Abstract  

A radiochemical procedure to extract plutonium, americium and strontium from soils is presented. Strontium was separated from americium and plutonium fraction at the beginning of the method to increase the Sr recovery. The studied soils coming from an Alpine wetland site contain a big amount of iron which was eliminated by an oxalate precipitation before the column step. The hydroxide precipitation should be made by adding iron of known quantity to avoid interference. The procedure was validated by reference soils from IAEA. Plutonium-238, 239, 240, 241Am, 90Sr and 137Cs activities are given and some isotopic ratios are calculated in order to know the origin of the radionuclides.

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Abstract  

The possible application of cyclotron-produced fast neutrons to activation analysis for oxygen based on the16O(n, p)16N reaction has been investigated. Neutrons were produced by bombarding a thick beryllium target with 22 to 45 MeV deuterons. It was found that the sensitivity increases rapidly with the energy of the deuterons. Using 45 MeV deuterons and a 10 μA beam current a sensitivity of about 20 counts per 1 μg oxigen could be achieved, enabling the determination of less than 1 μg oxigen. In a direct comparison it was experimentally established that the sensitivity for cyclotron-produced neutrons assuming a deuteron beam of about 10 μA, is up to two orders of magnitude higher than that achievable for 14 MeV neutrons with a flux of about 1010 n/s. The interference of fluorine is at about the same level for both the cyclotron-produced and 14 MeV neutrons. Using cyclotron-produced fast neutrons in the investigated energy range, sodium and magnesium can also interfere, but only to a very much lower extent.

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Abstract  

When a river flow rate is known on one point, it is possible to determine the one of upstream tributaries. This can be done by measuring the concentrations of a dissolved element (for example Ca2+), provided that no chemical precipitations have occurred in mixture waters. In this later case, the determination of flow rate is however possible by isotopic geochemistry, by knowing isotopic ratios of an element, for ex. 234U/238U, in each river considered and the ratio of the concentrations in dissolved 238U in two of them. A study of the Var and its tributary the Vésubie is performed: in January 31st, 2001, the flow rate D3, downstream the confluence was 35 m3/s. The ratio of the 238U concentrations in the Vésubie river and in the Var upstream (238U1/238U2) was 5.5. The isotopic ratios 234U/238U measured in the Var, downstream the confluence were R3 = 1.51, upstream R2 = 1.75, and in the Vésubie R1 = 1.08. We have calculated the Vésubie flow rate as D1 = 3.2 m3/s.

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Abstract  

In a large number of alpine rocks and respective mineral separates the beryllium distribution was studied via “non-destructive” photon activation. The detection limit of the assembly was ∼20 ppb. The existence of Be-rich areas was revealed. A selection of individual rocks was analysed by instrumental as well as by radiochemical neutron activation analysis for main and trace elements as: Na, K, Sc, Cr, Mn, Fe, Co, Rb, Cs, La, Eu, Yb, Ta, W, Au, and U. The latter was determined by counting the235U-fission tracks. The data supply an insight into the complex processes leading to the formation of metamorphic rocks. The hardware and the computer evaluation of the γ-spectra is described in some detail. A further application is the determination of traces of53Mn (in the order of 10−12 g/g) produced by the interaction of cosmic rays with stony meteorites. From a comparison of the26Al- and53Mn-values it is concluded that the depth dependent production of these two radionuclides differs slightly.

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