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Determination of silicon in cast iron by 14 MeV neutron activation
High-resolution gamma-ray spectrometry with a56Mn internal standard
Abstract
Silicon in cast iron was analyzed by 14 MeV neutron activation—high-resolution γ-ray spectrometry. Silicon was detected as28Al, the product of the28Si(n, p)28Al reaction. Interference of56Mn was separated using a Ge(Li) detector and a biased amplifying system. The 1. 81 MeV gamma-radiation of56Mn, which is the product of the56Fe(n, p)56Mn reaction of the matrix of cast iron, was used as an internal standard and for correction of the self-absorption of the 1. 78 MeV gamma-radiation of28Al by the sample. The interferences of aluminum, phosphorus and manganese could be neglected according to the results calculated from their nuclear properties and contents in the cast iron of this experiment. The results of this method agreed well with the results of the usual chemical method, with errors less than 5% of the results, and the precision of the method was satisfactory with a C. V. of less than almost 6% for rapid analysis of silicon in cast iron. The analytical line through the origin with a slope of the mean value of the repetition experiments could be used as the analytical line with almost the same precision and accuracy of the results as for the analytical line calculated by the least squares method.
Abstract
Silicon as silicon dioxide in iron and steel-making slags and fluorspars was analyzed by 14 MeV neutron activation high-resolution γ-ray spectrometry. Silicon was detected by measuring the 1.78 MeV γ-ray of28Al, the product of the28Si(n, p) reaction, using a 30 cm3 coaxial Ge(Li) detector. A modified TPA method was used for the calculation.28Al is also produced from phosphorus by the31P(n,α) reaction, and from aluminium by the27Al(n,γ) reaction. The contribution from the former reaction could be corrected experimentally when the P2O5 content of the sample was known, while the latter reaction could be neglected in this neutron energy region. The experimental correction coefficient for phosphorus agreed well with the theoretical value calculated from the nuclear properties of silicon and phosphorus. Yields of28Al from SiO2, P2O5 and Al2O3 of the same weight percentages were calculated as 1, 0.426 (experimentally 0.44) and 0.0022, respectively. The results of this method agreed well with the results of the usual chemical methods. The limit of detection of SiO2 in iron and steel-making slags and fluorspars was calculated as 0.07%. The coefficient of variation of repeated experiments was compared with the statistical one.
Abstract
Loss of99Tc in seaweed during dry ashing has been investigated. Two kinds of brown seaweeds labeled with99Tc were ashed for 24 or 48 h at 400, 450 and 500 °C, showing no correlation between the loss of99Tc and species, temperature and time of ashing. The averaged recovery of99Tc was 91.0±4.0%, indicating that most of the99Tc in the seaweed was retained within the matrix of the ash which was obtained under general conditions of ashing.
Abstract
The diffusion coefficients of Sr in gelled silica gel layers have been measured at various porosities. They decreased with the second power of porosity. At constant porosity, the diffusion coefficients of Sr and Co were measured at various pHs. They were dependent on the distribution coefficients (K) of the species between silica gel and pore water as a function of 1/(1+K). Gelation of the porous layer enables a stable measurement of diffusion coefficients under various conditions and facilitates the analysis of the distribution of ions after the diffusion experiments.
Abstract
A model for treating the sorption of metal ions on hydrous metal oxides was established based on the assumptions that these materials are weakly acidic cation exchangers and have a discrete 
exchanger phase.
The experimental results of the sorption of metal ions on the hydrous niobium(V) and tin(IV) oxides are found to be consistent with the formulas derived from the model by considering that the charge balance and the mass action law hold in the exchanger phase and cations are sorbed by the distribution between this phase and the bulk aqueous phase.
Abstract
Tritium concentrations were analyzed for coastal seawater and lake water collected from various places in Japan. Low tritium concentrations were observed for coastal seawater of small islands and it was attributed to a short residence time of the ground-water in such a small island. Tritium concentrations in lake water showed a significant variation. And it was revealed that the size of the lake and its drainage area were the dominant factors controlling the tritium concentrations in lakes.
Summary
Extremely low activity levels of cosmic ray induced nuclides have been measured in freshly precipitated rainwater by quick chemical separation coupled with ultra low background gamma-spectrometry. The nuclides detected were 38S (T 1/2 = 2.83 h)-38Cl (37.2 m), 39Cl (55.6 m), 24Na (14.96 h), 28Mg (20.9 h), 7Be (53.3 d) and 22Na (2.602 y). The number of atoms in rain water were evaluated to be ranging from 400-1900 l-1 for 39Cl (n = 6, mean: 1200), 30-1500 l-1 for 24Na (n = 16, mean: 520), 80-600 l-1 for 28Mg (n = 13, mean: 260), 1 . 106-4 . 107 l-1 for 7Be (n = 16, mean: 7 . 106) and 2 . 103-1 . 105 l-1 for 22Na (n = 9, mean: 2 . 104). Measurements of activity levels and activity ratios of short-lived cosmic-ray induced short-lived nuclides will open new method to understand atmospheric processes occurred at the altitude of rain cloud.
Abstract
A magnetic-fields dependence of heat capacity of [Mn5(hmp)4(OH)2{N(CN)2}6]2MeCN·2THF (hmp=hydroxymethylpyridinate) is investigated by the thermal relaxation calorimetry technique. This compound is a three-dimensional system consisting of Mn4 single-molecule magnet (SMM) units and Mn2+ ions, which are linked by the dicyanamide ligands to form a coordination network structure. A sharp peak of C p being associated with the formation of three-dimensional long-range order is observed around 1.96 K. The thermodynamic discussion based on the magnetic entropy suggests that both SMMs and Mn2+ ions are involved in the formation of the anitiferromagnetic spin ordering. However, this long-range ordering is very sensitive to the external magnetic fields which work to change the magnitude of the Zeeman splitting of the SMM levels. The behavior under magnetic fields is similar to that of the two-dimensional Mn4-network system studied previously.
Abstract
Correction equations of the coincidence-summing effect for efficiencies of HpGe detector based on the decay scheme were developed by considering the summing up to triple coincidence. The correction equations which do not dependent on the kind of the Ge detector are very useful for efficiency calibrations of a Ge detector in the energy region from 60 to 400 keV by using75Se radionuclide even with very short source-to-detector distances.
Abstract
We have studied the improvement of energy spectra of a cadmium telluride (CdTe) semiconductor detector by means of a neural network algorithm. The neural network recognized pulse shapes and determined the corrective magnification factors of digitally shaped pulse heights. That is to say, the neural network recognized the difference in the pulse shapes due to the incomplete charge collection and made up for the ballistic deficit of each pulse. We obtained the energy spectra of several gamma ray sources. After the processing, the energy spectra became more ideal profile and the energy resolution (FWHM) changed for the better.
