K 0-prompt gamma ray activation analysis for estimation of boron and cadmium in aqueous solutions

K ₀-PGAA (prompt gamma activation analysis) has been used to estimate boron and cadmium contents in industrial and environmental materials from some different local areas as well as, samples from different locations in Burullus and Qarun Lakes. A high efficiency Compton background suppression gamma-ray spectrometry by anti-coincidence counting with a NaI(Tl) shield around a central HPGe detector for in beam PGAA using a ²⁵²Cf neutron source has been calibrated and described in this paper. The facility is principally designed for measurement of the prompt gamma-ray spectra obtained due to thermal neutron capture using 1951.14 keV gamma line of ³⁵Cl as the internal mono-standard comparator. A calibration curves were developed in which a set of boron and cadmium standards were tested and the count rate to boron and cadmium mass curves were determined. This set of boron and cadmium measurements was compared with a method for determining composition using K ₀-PGAA. Conventional prompt neutrons capture Gamma-ray results were in a good agreement with the data obtained by K ₀-PGAA method. Detection limits and self-shielding study are presented.     

Development of the <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-based cyclic neutron activation analysis for short-lived radionuclides

The k ₀-based cyclic neutron activation analysis (k ₀-CNAA) technique has been studied to explore the applicability at the Portuguese research reactor (RPI). In particular, for the determination of elements which form short-lived radionuclides, particularly fluorine (²⁰F, 11.16 s half-life) and selenium (^77mSe, 17.36 s half-life) in polymer, biological and environmental samples. The detection limits obtained for F and Se were about 50 and 0.01 mg kg⁻¹, respectively, in the investigated materials. The timing parameters for the procedure were 10 to 20 s for irradiation, 5 s decay, 10 to 20 s counting, 5 s waiting and performed with eight cycles. The k ₀-IAEA program was modified to use millisecond time resolution for irradiation, decay and counting times as needed for interpreting k ₀-CNAA data in terms of concentration, accuracy and detection limit. The quality control of the procedure was performed by preparing a standard solution containing fluorine with different contents as well as using the certified reference materials containing selenium from which the bias between the results and the certified values were within 15% for most elements at the investigated content ranges. The analytical results for several other elements producing short-lived or detectable radionuclides, e.g., Al, Ca, Cl, Cu, Dy, I, Mg, Mn, Ti, and V were also obtained by the k ₀-CNAA procedure with accuracy within 12%.     

Determination of the prompt k<Subscript>0,H</Subscript> factors and partial γ-ray production cross sections for B,N, Si,P, S and Cl

Summary The prompt k_0,H factors for B, N, Si, P, S and Cl were determined relative to the 2223.25 keV gamma-line from the ¹H(n,γ) reaction. The measurements were performed at the SNU-KAERI Prompt Gamma Activation Analysis facility, of which the background was greatly reduced recently by upgrading the detection system to a Compton suppressed g-ray spectrometer with a BGO/NaI(Tl) guard detector and by improving the shield geometry. From the measured prompt k_0,H factors, the partial γ-ray production cross sections were determined using the latest cross section for H. The measured prompt k_0,H factors were tabulated and compared with the other reported data.     

Synthesis and characterization of the [Ru<Subscript>3</Subscript>O(CH<Subscript>3</Subscript>COO)<Subscript>6</Subscript>(py)<Subscript>2</Subscript>(BPE)Ru(bpy)<Subscript>2</Subscript>Cl](PF<Subscript>6</Subscript>)<Subscript>2</Subscript> dimer

The polymetallic [Ru₃O(CH₃COO)₆(py)₂(BPE)Ru(bpy)₂Cl](PF₆)₂ complex (bpy = 2,2′-bipyridine, BPE = trans-1,2-bis(4-pyridil)ethylene and py = pyridine) was assembled by the combination of an electroactive [Ru₃O] moiety with a [Ru(bpy)₂(BPE)Cl] photoactive centre, and its structure was determined using positive ion electrospray (ESI-MS) and tandem mass (ESI-MS/MS) spectrometry. The [Ru₃O(CH₃COO)₆(py)₂(BPE)Ru(bpy)₂Cl]²⁺ doubly charged ion of m/z 732 was mass-selected and subject to 15 eV collision-induced dissociation, leading to a specific dissociation pattern, diagnostic of the complex structure. The electronic spectra display broad bands at 409, 491 and 692 nm ascribed to the [Ru(bpy)₂(BPE)] charge-transfer bands and to the [Ru₃O] internal cluster transitions. The cyclic voltammetry shows five reversible waves at −1.07 V, 0.13 V, 1.17 V, 2.91 V and −1.29 V (vs SHE) assigned to the [Ru₃O]^{−1/0/+1/+2/+3} and to the bpy^0/−1 redox processes; also a wave is observed at 0.96 V, assigned to the Ru^+2/+3 pair. Despite the conjugated BPE bridge, the electrochemical and spectroelectrochemical results indicate only a weak coupling through the π-system, and preliminary photophysical essays showed the compound decomposes under visible light irradiation.     

Development and applications of <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript> based NAA and prompt gamma-ray NAA methods at BARC

A summary of k ₀-based R&D work on neutron activation analysis (NAA), internal mono standard NAA (IM-NAA) and prompt gamma-ray NAA (PGNAA) is presented. The k ₀-based NAA was standardized by characterizing irradiation sites of research reactors, validated using reference materials and applied to samples of different origin. Recently IM-NAA method was developed, validated for small and large size samples and applied for the analysis of large size as well as non-standard geometry samples. Studies on PGNAA included characterization of neutron beam, determinations of detection efficiency and prompt k ₀-factors, and analytical applications.     

Correction of k<Subscript>0</Subscript>-factors for non-1/v elements based on neutron spectrum measurements

Neutron spectra were measured by the time of flight method using a rotating disk chopper system in the JRR-3M prompt gamma ray analysis system. Effective g-factors for non-1/v elements such as Cd, Sm and Gd were calculated from the measured neutron spectra and the neutron cross section data, and they was used for correcting the k ₀-factors. The resulting k ₀-factors for the cold and thermal neutron beams agreed within 10%. Furthermore, the prompt gamma ray emission probabilities of Cd, Sm and Gd were derived from the corrected k ₀-factors using other relevant physical constants.     

Investigation of fast neutron shielding characteristics depending on boron percentages of MgB<Subscript>2</Subscript>, NaBH<Subscript>4</Subscript> and KBH<Subscript>4</Subscript>

The macroscopic cross-section Σ and average neutron fluence in matter Φ are usable factors to comment neutron shielding property of samples. In this paper, we have used MgB₂, NaBH₄ and KBH₄ samples including different percentages of boron. Neutron macroscopic cross-section measurements of them have been done by using a source of mono-energetic neutrons (E _eff = 4.5 MeV ²⁴¹Am–Be). Average neutron fluence values and double differential fast neutron flux distributions of each samples calculated by using FLUKA Monte Carlo code. Also half value layers (HVLs) of samples are compared to paraffin which is one of the most neutron moderators. As a result, growing boron concentration can raise neutron shielding property of materials.     

Effect of phenyl group on the structure and formation of transitional alumina from Al (OPh)<Subscript>3</Subscript>

The structure of freshly prepared Al(OPh)₃, its decomposition product, the hydrolyzed products and their structural evolution were investigated employing ²⁷Al MAS NMR spectroscopy, PXRD, TGA/DTA/DSC/FTIR techniques. In the ²⁷Al MAS NMR spectrum of the aluminium phenoxide, three signals with the chemical shift at 3.78, 21 and 45 ppm were observed. The chemical shift at 3.78 and 45 ppm revealed the presence of four and sixfold coordinated aluminum. The signal at 21 ppm corresponded to fivefold coordinated aluminium. When the aluminium phenoxide was directly decomposed in air at 600 °C, it resulted in amorphous product as evidenced from the PXRD pattern. The observed signals with chemical shifts at 10.1, 42, 73.6 ppm in the ²⁷Al MAS NMR spectrum indicated the presence of 6, 5 and 4 coordination for the aluminium atoms suggesting disordered transitional γ-alumina to be the product. The hydrolysis studies of Al(OPh)₃ with excess of water at 70 °C yielded bohemite (γ-AlOOH). The alumina obtained after dehydration at 600 °C was X-ray amorphous. The dehydrated product at 600 °C showed the presence of four and six coordinated aluminium atoms in the ²⁷Al MAS NMR spectrum confirming it to be ordered γ-Al₂O₃. Crystalline γ-Al₂O₃ was obtained on further heating at 800 °C.     

Synthesis of nonequilibrium Ir<Subscript>x</Subscript>Re<Subscript>1-x</Subscript> solid solutions. Crystal structure of [Ir(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl]<Subscript>2</Subscript>[ReCl<Subscript>6</Subscript>]Cl<Subscript>2</Subscript>

Synthesis of five binary complex salts with an [Ir(NH₃)₅Cl]²⁺ complex cation is described. The counterions are [ReCl₆]^2–, [IrCl₆]^2–, [ReBr₆]^2–, and Cl^–. A polycrystal X-ray diffraction study has been performed for [Ir(NH₃)₅Cl]₂[ReCl₆]Cl₂, and its crystal structure has been determined. A series of Ir _x Re_1–x phases (0.5 x > 1) were obtained by reductive thermolysis. For the Ir-Re system, the history of the V/Z(x) dependence has been refined.Original Russian Text Copyright © 2004 by S. A. Gromilov, S. V. Korenev, I. V. Korolkov, K. V. Yusenko, and I. A. BaidinaTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 508–515, May–June 2004.     

Separation and purification of <Superscript>249</Superscript>Cf and <Superscript>245</Superscript>Cm

There is a need to provide radioactivity standards of the higher actinides in support of both decommissioning and remediation activities as well as routine environmental analysis. In the case ²⁴⁹Cf, this will provide a useful calibration nuclide for both α-and γ-spectrometry as well as improving knowledge of the decay scheme for this nuclide. There is anecdotal evidence to suggest that the chemical yield of americium and curium may differ in radiochemical analysis. Thus, a chemical yield tracer of ²⁴⁵Cm may help to resolve this issue and will be suitable for both, suitable for use as a chemical yield tracer for both α-particle spectrometry and mass spectrometry. An aged source of ²⁴⁹Cf was used as the source material for the separation of these two nuclides by cation-exchange, using 2-hydroxy-2-methyl-propanoic acid at controlled pH as an eluant, ²⁴⁹Cf being eluted before the ²⁴⁵Cm daughter. The purity of both nuclides was measured by γ-ray spectrometry.     

A neutron induced prompt gamma-ray spectroscopy system using a 252Cf neutron source for quantitative analysis of aqueous samples

A neutron induced prompt γ -ray spectrometry (NIPS) facility has been developed at the Nuclear Chemistry Research Division, of the Korea Atomic Energy Research Institute (KAERI) with the aim of analyzing the major components of various elements in aqueous samples. The facility is equipped with a ²⁵²Cf neutron source and a γ-γ coincidence setup with two n-type coaxial HPGe detectors based on NIM spectrometric modules in association with data acquisition and spectral analysis systems. The development of the system, its set-up and the calibration of detection efficiency up to 8 MeV using a set of radionuclides and the (n,γ) reactions of chlorine are described in the paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chromium(III) complexes with lutidinic acid: kinetic studies in HClO<Subscript>4</Subscript> and NaOH solutions

Chromium(III)-lutidinato complexes of general formula [Cr(lutH) _n (H₂O)_6−2n ]³⁻ⁿ (where lutH⁻ is N,O-bonded lutidinic acid anion) were obtained and characterized in solution. Acid-catalysed aquation of [Cr(lutH)₃]⁰ leads to only one ligand dissociation, whereas base hydrolysis produces chromates(III) as a result of subsequent ligand liberation steps. The kinetics of the first ligand dissociation were studied spectrophotometrically, within the 0.1–1.0 M HClO₄ and 0.4–1.0 M NaOH range. In acidic media, two reaction stages, the chelate-ring opening and the ligand dissociation, were characterized. The dependencies of pseudo-first-order rate constants on [H⁺] are as follows: k _obs1 = k ₁ + k ₋₁/K ₁[H⁺] and k _obs2 = k ₂ K ₂[H⁺]/(1 + K ₂[H⁺]), where k ₁ and k ₂ are the rate constants for the chelate-ring opening and the ligand dissociation, respectively, k ₋₁ is the rate constant for the chelate-ring closure, and K ₁ and K ₂ are the protonation constants of the pyridine nitrogen atom and coordinated 2-carboxylate group in the one-end bonded intermediate, respectively. In alkaline media, the rate constant for the first ligand dissociation depends on [OH⁻]: k _obs1 = k _OH(1) + k _O[OH⁻], where k _OH(1) and k _O are rate constants of the first ligand liberation from the hydroxo- and oxo-forms of the intermediate, respectively, and K ₂ is an equilibrium constant between these two protolytic forms. Kinetic parameters were determined and a mechanism for the first ligand dissociation is proposed. The kinetics of the ligand liberation from [Cr(lut)(OH)₄]³⁻ were also studied and the values of the pseudo-first-order rate constants are [OH⁻] independent.     

Investigation of neutron sensitivity of un-doped and Dy-doped CaB<Subscript>4</Subscript>O<Subscript>7</Subscript> for thermoluminescence applications

In this study, thermoluminescence characteristics of un-doped and Dy-doped calcium tetraborate (CaB₄O₇) compounds are reported. The polycrystalline powder samples of un-doped and Dy-doped CaB₄O₇ were prepared by a solid-state reaction at high-temperature method. The identification and characteristics of the obtained compounds were determined by X-ray diffraction, Fourier transform infrared analysis, differential thermal analysis, thermogravimetric analysis, and scanning electron microscopy. The glow curves were obtained using a thermoluminescent reader. Neutron sensitivity, dose–response, and heating rate of CaB₄O₇ compounds were determined by using a bare ²⁵²Cf mixed neutron?+?gamma (n?+?γ) source, and dose response results are compared to those of Harshaw TLD-600 and TLD-700 neutron dosimeters (⁶LiF:Mg,Ti and ⁷LiF:Mg,Ti). The sensitivity of CaB₄O₇:Dy (0.5%) sample is approximately 4.35 and 3.36 times higher than that of TLD-600 and TLD-700, respectively.     

Is there something wrong in the barium determination by k<Subscript>0</Subscript>-INAA?

There was a confusion around the Q ₀- and k ₀-values for the reaction ¹³⁰Ba(n,γ)¹³¹Ba. The problem was clarified in this work by re-determination of the k ₀-values and critical evaluation of the Q ₀-values. The new ¹³¹Ba k ₀-values were found to be about 16% lower than the recommended ones compiled in 1989 and about 10% lower than those recommended in 2003. The Q ₀-value was verified to be 24.3. These new values were successfully applied in k ₀-INAA of Ba in various references samples. Possible error sources in Ba determination were investigated which might compensate the negative bias in Ba results from using the inaccurate k ₀-values, consequently masking the problem of these old k ₀-factors so far. In this context, a few cases were studied and presented.     

Thermochemical properties of MnNb<Subscript>2</Subscript>O<Subscript>6</Subscript>

Homogeneous manganocolumbite (MnNb₂O₆) was synthesized from Nb₂O₅ and MnO oxides. Powder sample was orthorhombic with unit cell parameters: α = 0.5766 nm, b = 1.4439 nm, c = 0.5085 nm and V = 0.4234 nm³. Heat capacity over the temperature range of 313–1253 K was measured in an inert atmosphere with combined thermogravimetry and calorimetry using NETZSCH STA 449C Jupiter thermoanalyzer. Melting point was 1767 ± 3 K, enthalpy of melting was 144 ± 4 kJ mol⁻¹. Experimental heat capacity of MnNb₂O₆ is fitted to polynomial C _pm = 221.46 + 3.03 · 10⁻³ T + −39.79 · 10⁵ T ⁻² + 40.59 · 10⁻⁶ T ².     

Investigation into the formation of heteronuclear clusters of formula [{Ru<Subscript>6</Subscript>C(CO)<Subscript>16</Subscript>Ag<Subscript>2</Subscript>X}<Subscript>2</Subscript>]<Superscript>2−</Superscript> (X = Cl,Br or I)

Reaction of [Ru₆C(CO)₁₆]²⁻ with an excess of AgX (X = Cl, Br or I) affords heteronuclear clusters of formula [{Ru₆C(CO)₁₆Ag₂X}₂]²⁻ in 80% yield, which for X = I and X = Br/Cl were crystallographically characterised. The formation of the cluster was followed in solution using electrospray ionisation mass spectrometry (ESI-MS), which revealed the presence of a wide range of clusters with the general formula [{Ru₆C(CO)₁₆} _x Ag _y X _z ]^{(2x−y+z)−} where x = 1 or 2, y = 1, 2, 3 or 4 and z = 0, 1 or 2. The high yield of the product despite the evident complicated solution speciation is attributed to selective crystallisation of the observed compound driving the equilibrium toward this product.     

Computational study on the reaction of CH<Subscript>3</Subscript>SCH<Subscript>2</Subscript>CH<Subscript>3</Subscript> with OH radical: mechanism and enthalpy of formation

The reaction mechanism of CH₃SCH₂CH₃ with OH radical is studied at the CCSD(T)/6-311+G(3df,p)//MP2/6-31+G(2d,p) level of theory. Three hydrogen abstraction channels, one substitution process and five addition–elimination channels are identified in the title reaction. The result shows hydrogen abstraction is dominant. Substitution process and addition–elimination reactions may be negligible because of the high barrier heights. Enthalpies of formation [ \Updelta_f H_{(298.15\textK)}^o \Updelta_{f} H_{(298.15{\text{K}})}^{o} ] of the reactants and products are evaluated at the CBS-QB3, G3 and G3MP2 levels of theory, respectively. It is found that the calculated enthalpies of formation by the aforementioned three methods are in consistent with the available experimental data. Rate constants and branching ratios are estimated by means of the conventional transition state theory with the Wigner tunneling correction over the temperature range of 200–900 K. The calculation shows that the formations of P1 (CH₂SCH₂CH₃ + H₂O) and P2 (CH₃SCHCH₃ + H₂O) are major products during 200–900 K. The three-parameter expressions for the total rate constant is fitted to be k_\texttotal = 1.45 ×10 ^{- 21} T^3.24 exp( - 1384.54/T) k_{\text{total}} = 1.45 \times 10^{ - 21} T^{3.24} \exp ( - 1384.54/T) cm³ molecule⁻¹ s⁻¹ from 200 to 900 K.     

Boron in coral skeletons determined by prompt γ-ray analysis

A systematic and non-destructive technique is proposed for the determination of boron in coral samples by neutron-induced prompt γ-ray analysis (PGA) using a thermal neutron guide beam of the JRR-3M reactor. About 50–150 mg samples in sealed FEP film were irradiated and measured for 5000 s in the PGA system at a neutron flux of 2.4 × 10⁷ n cm⁻² s⁻¹. In order to determine B content in coral skeletons, the Doppler-broadened γ-ray peak of 478 keV (¹⁰B) was used together with the correction of interference from the Na-peak of 472 keV. The analytical precision was ~3% for the JCp-1 coral standard. The data (n = 56) obtained by the present method showed a range of B content from 40.7 to 76.9 ppm which is similar to reported values. Boron in corals showed the highest levels in Rukan-sho (Okinawa) with an average B content of 62.5 ppm, whereas corals collected from Mizugama (Okinawa), Cebu (the Philippines) and Khang Khao (Thailand) exhibited B contents of 56.5, 53.0 and 45.7 ppm, respectively. The uptake of boron by living corals may be influenced by seawater pH related to higher seawater B(OH)₄⁻. In this paper we discuss factors controlling the B levels in corals.     

Structure and lithium mobility of Li<Subscript>4</Subscript>Pt<Subscript>3</Subscript>Si

The lithium-rich silicide Li₄Pt₃Si was synthesised from the elements by high-temperature synthesis in a sealed niobium ampoule. Its structure was refined on the basis of single-crystal X-ray diffraction data: R32, a = 693.7(2), c = 1627.1(4) pm, wR2 = 0.0762, 525 F² values and 21 variables. The striking structural motifs of the Li₄Pt₃Si structure are silicon atoms with a slightly distorted trigonal prismatic platinum coordination with short Si–Pt distances (238–246 pm). Always two trigonal prisms are condensed via a common Pt₃ triangle, and these double units built up a three-dimensional network by condensation via common corners. The channels left by this prismatic network are filled by two crystallographically independent lithium sites in a 3:1 ratio. The single crystal X-ray data were fully confirmed by neutron powder diffraction and ⁷Li magic-angle spinning (MAS)–nuclear magnetic resonance (NMR) results. The two distinct lithium sites are well differentiated by their ⁷Li isotropic chemical shift and nuclear electric quadrupolar interaction parameters. MAS-NMR spectra reveal signal coalescence effects above 300 K, indicating chemical exchange between the lithium sites on the millisecond timescale. The spectra can be simulated with a simple two-site exchange model. From the resulting temperature-dependent correlation times, an activation energy of 50 kJ/mol is extracted.     

Preparation and measurement of the half-life of <Superscript>101</Superscript>Tc

¹⁰¹Tc is a very important nuclide as fuel burn up monitor, and its half-life value has been measured many times, however, they were so different from each other. In this work, ¹⁰¹Tc liquid samples were prepared by irradiating analytical pure (NH₄)₆Mo₇O₂₄·4H₂O solution in Miniature Neutron Source Reactor (MNSR) of China. A rapid procedure which takes only 5 min was developed to separate ¹⁰¹Tc samples. The final samples were analyzed by γ-ray spectrum using high purity Germanium (HPGe) multi-channel analysis system. The results showed that there were no peaks of other nuclides except ¹⁰¹Tc. The half-life of ¹⁰¹Tc was accurately measured with HPGe γ-detector following 306.8 keV γ-ray for about 140 min, and three methods R-value method, iterative method and translation method were adopted to process the data. Finally, a more precise and accurate value 14.02 ± 0.01 min was given and compared with former measured data.