Ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) and radiometric techniques for the determination of actinides in aqueous leachate solutions from uranium oxide

The choice of the analytical method for the determination of actinide isotopes in leachate solutions has to be made considering several parameters: detection limit for each isotope, sample preparation procedure in terms of duration and complexity, counting time and interferences. A leachate solution obtained by keeping a pellet of UO2 doped with 238Pu in contact with distilled water was investigated for the content of U and Pu isotopes by radiometric methods (alpha-, gamma-spectrometry and liquid scintillation counting). The results of the radiometric methods were compared with those obtained from the analysis performed by inductively coupled plasma mass spectrometry on-line to a system for chromatographic separation (IC-ICP-MS). The comparison confirmed that IC-ICP-MS is a powerful method for the detection of long-lived radionuclides. The radiometric methods have a detection limit two orders of magnitude lower than IC-ICP-MS in the case of short-lived radioisotopes mostly due to the low background in the detector. On the other hand, the sample preparation and the analysis duration are more time-consuming compared to IC-ICP-MS; moreover, not all isotopes can be determined by using only one radiometric technique.     

Metal-phthalocyanine array on the moiré pattern of a graphene sheet

Iron-phthalocyanine (FePc) molecules have been adsorbed on a graphene sheet prepared on the Ir(111) surface. The FePc molecules are flat-lying on graphene, as determined by near-edge X-ray absorption fine-structure, constituting a sub-nanometer thick molecular array at the single-layer coverage. The flat FePc single-layer presents a weak interaction of the organic macrocycle with the graphene surface and Ir subsurface substrate. Further FePc deposition on top of the first flat single-layer determines a three-dimensional island growth with varying molecular orientation.     

Detection of trace radioisotopes in soil,sediment and vegetation by glow discharge mass spectrometry

The possibility for the determination of some radioisotopes of cesium, strontium, plutonium, uranium and thorium by glow discharge mass spectrometry (GDMS) in soils, sediments and vegetations is investigated. The preparation of samples is described as a combination of the use of a conductive host matrix and a secondary cathode in order to decrease the dilution effect of the blending material for the trace level determination and to gain a stable discharge. Effects of interferences arising from the nature of the conductive host matrix and of the secondary cathode on the sensitivity of the method are discussed. The determination of (137)Cs and (90)Sr has been attempted and the results obtained were in agreement with those from other analytical techniques. Accuracy, internal and external precisions have been also evaluated. GDMS is shown to be a helpful technique for the determination of radioisotopes in environmental samples. Radioisotopes can be determined according to the matrix of the sample (e.g. grass), also in presence of isobaric interferences. However, limitations still exist on the application of GDMS.     

Diagnosing laser-driven,shock-heated foam target with Al absorption spectroscopy on OMEGA EP

Results on diagnoses of laser-driven, shock-heated foam plasma with time-resolved Al 1s-2p absorption spectroscopy are reported. Experiments were carried out to produce a platform for the study of relativistic electron transport. In cone-guided Fast Ignition (FI), relativistic electrons generated by a high-intensity, short-pulse igniter beam must be transported through a cone tip to an imploded core. Transport of the energetic electrons could be significantly affected by the temperature-dependent resistivity of background plasmas. The experiment was conducted using four UV beams of the OMEGA EP laser at the Laboratory For Laser Energetics. One UV beam (1.2 kJ, 3.5 ns square) was used to launch a shock wave into a foam package target, consisting of 200 mg/cm³ CH foam with aluminum dopant and a solid plastic container surrounding the foam layer. The other three UV beams with the total energy of 3.2 kJ in 2.5 ns pulse duration were tightly focused onto a Sm dot target to produce a point X-ray source in the energy range of 1.4–1.6 keV. The quasi-continuous X ray signal was transmitted through the shock-heated Al-doped, foam layer and recorded with an X-ray streak camera. The measured 1s-2p Al absorption features were analyzed using an atomic physics code FLYCHK. Electron temperature of 40 eV inferred from the spectral analysis is consistent with 2-D DRACO Radiation-hydrodynamic simulations.