Neutron activation analysis and Ge(Li) spectroscopy was used to determine 32 elements in seven U.S.G.S. standard rocks of
a wide range of composition. Short half-life nuclides (10 sec-10 min) were used to measure Sc, Hf, Dy, Mg, Al, Ca, Ti, V (and
Na) in an automated rabbit Ge(Li) detector system. The elements K, Cu, Zn, Ga, Sr, Ba, La, Eu, Sm (and Mn) were determined
by dissolution of the irradiated sample followed by removal of24Na on hydrated antimony pentoxide (HAP). Long-lived nuclides were used to measure Sc, Cr, Fe, Co, Zr, Rb, Sb, Cs, Ba, Ce,
Eu, Yb, Tb, Lu, Hf, Ta and Th after decay of24Na. The method involves little radiochemistry and the separation is selective for24Na under the experimental conditions used. Elemental concentrations determined agree well with previously published data.
Authors:Y. Tsujimi, M. Kobayashi, H. Furuta, and T. Yagi
The ultra-slow modes with a relaxation time much longer than 1 ns are discovered by a time-resolved spectroscopy in uniaxial ferroelectric (NH2CH2COOH)3H2SO4 (TGS) and in glass-former HOCH2(CHOH)4CH2OH (D-sorbitol). A mode discovered in TGS is a thermal relaxational mode and is proved to be the physical origin of the central peak found by Brillouin scattering. Two modes are discovered in D-sorbitol. One is a thermal relaxational mode. The other is a mode characterized by the Kohlraush-Williams-Watts function with a relaxation time
R. A remarkable result is that
R indicates a critical behavior not at the liquid-glass transition temperature Tg =–7°C but at the ergodic to nonergodic transition temperature Tc=33°C.
Authors:A. Porto, W. Magalhães, C. Carvalho, and J. Machado
Positron Lifetime Spectroscopy (LS) measurements were performed in a series of binary molecular solid solutions of the general formula M1–xGxL3, where L(ligand)=acetylacetone, dipivaloylmethane, or N-benzoyl-N-phenylhydroxylamine, M=Al(III), Ga(III) or In(III), as matrix, and G=Cr(III), Mn(III), Fe(III), Co(III), Ru(III), Rh(III) and Ir(III), as guest molecules, and the corresponding mechanical mixtures. For the solid solutions, the o-Ps yield values (I3) decrease very rapidly with the increase of the guest mole fraction, showing a high efficient Ps inhibition process, while for the corresponding mechanical mixtures, these values decrease linearly with the increase of the guest molecule concentration, indicating the presence of two distinct phases. These results confirm our previous proposal that the LS technique is able to characterize solid solutions formed by one matrix, in whichI3 values are high, and one guest, in which theI3 values are very low.
Authors:G. Troyer, E. Nordquist, D. Legare, K. Hillesand, S. Kessler, J. Nelson, R. Richard, S. Goodwin, and E. Killian
The cleanup of high-level defense nuclear waste at the Hanford Site presents many challenges. These include removing and disposing
of components from buried active waste tanks to allow new equipment insertion or hazards mitigation. This paper discusses
a unique automated system that provides for retrieval, high-pressure washing, inventory measurement, and containment for disposal.
Key to the inventory measurement is a three-detector high-purity germanium high-performance gamma-spectroscopy system capable
of recovering data at up to 90-percent saturation (200,000 counts/s). Data recovery is based on a unique embedded electronic
pulser and special software to report the inventory. Each detector has different shielding specified through simulation using
the Monte Carlo computer code for N-particle transport modeling. This shielding provides performance over a dynamic range
of eight orders of magnitude. This paper covers system description, calibration issues, and operation.
Authors:Em. Cincu, I. Manea, V. Manu, D. Barbos, O. Sima, I. Gustavsson, P. Vermaercke, N. Vajda, Zs. Molnar, and H. Polkowska-Motrenko
Samples of high alloy Stainless Steel SS 1 were analyzed by instrumental neutron activation analysis (INAA) at 5 research
institutes in 4 European countries within the frame of an Inter-Laboratory Comparison (ILC) exercise aiming at checking if
the results were independent of the standardization methods, and if INAA was accurate enough to contribute to certification.
The mean element concentration values yielded by INAA were also compared with mean values obtained by atomic emission spectroscopy
techniques at other laboratories that took part in the International Proficiency Testing organized by KIMAB Institute of Sweden,
producer of the SS 1. The performances of the nuclear and atomic techniques were compared in terms of the z-score values calculated for 11 element concentrations evaluated by the two analytical ways. Finally, consideration is given
to the ways in which highest accuracy and precision can be ensured for certifying stainless steels as CRMs.
Oxo-centered trinuclear mixed-valence iron fumarate [Fe3O(O2CCH=CHCO2)3(H2O)3]·nH2O and iron malonate [Fe3O(O2CCH2CO2)3(H2O)3] have been prepared and studied by variable temperature Mössbauer spectroscopy. Iron fumarate complex showed a temperature dependent valence delocalization process. At 6 K two quadrupole split doublets corresponding to high-spin Fe(III) and high-spin Fe(II) state with an area ratio of 2:1 were observed and at 298 K there was only an averaged singlet peak. On the other hand malonate complex showed a localized valence state of high-spin Fe(III) and Fe(II) from low temperature to room temperature only with a slight variation in area ratio and spectral line broadening for Fe(II).
Ion association has been studied by positron lifetime spectroscopy in aqueous solutions containing the Ni2+ and SO
ions at 294 K with the double aim of assessing the reliability of the method for quantitative determination of complex formation constants and of probing the validity of various expressions to calculate single-ion activity coefficients at high ionic strength. The existence of two complexes, identified as NiSO4 and Ni2SO
, is shown by the data analysis. Considering the formation constant of the former, KI=(196±10)M–1, determined in previous works leads to discarding several of the expressions commonly used for activity corrections. Two possible values are retained for KI, (193±20)M–1 and (179±20)M–1, while KII related to Ni2SO
is better defined, as (2.57±0.14)M–1.
An activity predictor software was previously developed to foresee activities, exposure rates and gamma spectra of activated
samples for Radiation Science and Engineering Center (RSEC), Penn State Breazeale Reactor (PSBR), Neutron Activation Analysis
(NAA) measurements. With Activity Predictor it has been demonstrated that the predicted spectra were less than satisfactory.
In order to obtain better predicted spectra, a new detailed model for the RSEC NAA spectroscopy system with High Purity Germanium
(HPGe) detector is developed using Geant-4. The model was validated with a National Bureau of Standards certified 60Co source and tree activated high purity samples at PSBR. The predicted spectra agreed well with measured spectra. Error in
net photo peak area values were 8.6–33.6%. Along with the previously developed activity predictor software, this new model
in Geant-4 provided realistic spectra prediction for NAA experiments at RSEC PSBR.
Confinement of the glass-forming regions in the nanometer range influences the α-relaxation which is associated with the glass transition. These effects were investigated for semicrystalline poly(ethylene terephthalate) by dielectric spectroscopy and differential scanning calorimetry. The results are discussed within the concept of cooperative length, i.e. the characteristic length of the cooperative process of glass transition. Both experiments showed a dependence of the glass transition on the mean thickness of the amorphous layers. For the dielectric relaxation, the loss maximum was found to shift to higher temperatures with decreasing thickness of the amorphous layers, but no differences were observed in the curve shape for the differently crystallized samples. For the calorimetric measurements, in contrast, there was no correlation for the glass transition temperature, whereas the curve shape did correlate with the layer thickness of the mobile amorphous fraction. From the structure parameters, a characteristic length of approximately (2.5±1) nm was estimated for the unconfined glass relaxation (transition).
Authors:Madan Lal, R. Choudhury, D. Joseph, H. Bajpai, and C. Tyer
Analysis by Energy Dispersive X-ray Fluorescence spectroscopy of monazite ores from Kerala /Chavara and Manavalakurichi/, Orissa /Chattrapur/ and Tamil Nadu /Tirunelveli/ has been carried out for the determination of their elemental composition using109Cd /annular/ and241Am /disc/ radioisotope sources. The elements Y, Zr, Mo, Pb, Th and U were analyzed using a109Cd source, and the elements La, Ce, Pr, Nd, Sm, Gd and Dy were analyzed using the241Am source in side source geometry. Quntitative results on these 13 elements present in these ores were obtained by the EDXRF technique. It was seen that despite the diverse geological settings, there is remarkable similarity in the elemental composition of these ores, although some trace elements do show certain variations from sample to sample. These results are presented and discussed in this paper.