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- Author or Editor: N. Kim x
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Abstract
Radiochemical separation methods have been applied for the neutron activation analysis of impurities in four high-purity refractory metals, Ta, Nb, W and Mo. Impurities in the metals of Ta, Nb and W can be separated into groups using anion exchange resin with HF and/or a mixture of HF acid and HCl, but those in Mo is done using both anion and cation exchange resins. The coprecipitation of U with Th in HF media is also investigated.
Abstract
The relative ans single comparator methods have been applied to determine 7 rare-earth elements and U, Th in Korean Monazites by 14.5 MeV neutron activation analysis. The (n, 2n) nuclear reactions are used for all elements except La, for which (n, p) reaction is used. Al is used as a flux monitor for the relative method and as a singlle comparator for the single comparator method. The analytical results obtained by the two methods agree well within 3% deviation except for Sm and Gd. These results are also compared with the result obtained by a single comparator method using reactor neutron.
Abstract
The novel N4S2 azacrown ion exchange resin was prepared. The ion exchange capacity of N4S2 ion exchanger was 0.34 meq/g dry resin. A study on the separation of lithium isotopes was carried out with N4S2 azacrown ion exchange resin. The lighter isotope,6Li is concentrated in the resin phase, while the heavier isotope,7Li is enriched in the solution phase. With column chromatography [0.1 cm (I.D.)×32 cm (height)] using 2.0M NH4Cl as an eluent, separation factor, a=1.034 was obtained.
Abstract
The novel NDOE (1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane) ion exchange resin was prepared. The ion exchange capacity of NDOE azacrown ion exchanger was 0.2 meq/g dry resin. A study on the separation of lithium isotopes was carried out with NDOE novel azacrown ion exchange resin. The lighter isotope,6Li concentrated in the solution phase, while the heavier isotope,7Li is enriched in the resin phase. By column chromatography (0.1 cm I.D.×32 cm height) using 2.0M NH4Cl as an eluent, a separation factor,a=1.0201 was obtained.
Abstract
A radiochemical neutro activation analysis procedure has been developed for the determination of sodium and potassium at parts per billion levels in high purity tungsten/titanium alloy material. The procedure involves the use of an anion exchange separation for purifying sodium and potassium activities from the alloy’s matrix activities,46Sc and187W. In addition, the use of two sequential sample loadings on the resin column prior to elution of the matrix activities has been investigated. Irradiation of 200 mg of the alloy results in a sample of nearly 1 Ci which must be handled in a remote manipulation cell. After acid dissolution of the sample, the sample solution in 1M HF was loaded onto the column. Elution of the sodium and potassium was accomplished using 40 ml of 1M HF. Similar loading and elution of the second sample was followed by the elution of matrix activities with a solution of 1M HF+6M HCl. Extensive tracer experimentation was employed to establish the possibility of retaining the matrix activities on the column while a second sample solution was processed, thus greatly increasing the throughput in terms of the number of samples analyzed per day. The detection limits of Na and K using the method developed are 4.0 ppb and 200 ppb, respectively.
Abstract
A study on the separation of lithium isotope was carried out with a 1,16-dioxa-4,7,10,13- tetraazacyclooctadecane-4,7,10,13-tetramerrifield peptide resin [N4O2·4M]. The resin having N4O2 as an anchor group has a capacity of 3.8 meq/g. Upon column chromatography [0.15 cm (I.D)×29 cm (height)] using 0.01 M NH4Cl as an eluent, the single separation factor, α=1.038 was obtained by the Glueckauf theory from the elution curve and isotope ratios.
Abstract
Instrumental neutron activation analysis has been applied to semiconductor grade silicon to study the concentration levels of impurity elements, the contamination during the single crystal growing process, and the vertical and radial distributions of impurities, along with the decontamination effect in the analysis. Twenty elements of Au, Br, As, W, Cr, Co, Na, Eu, La, Se, Zn, U, Th, Hf, Fe, Sb, Ag, Ce, Tb and Ta have been analyzed in p- and n-type wafers, single crystals and a polycrystal by a single comparator method using two comparators of gold and cobalt. Considerable surface contamination has been found and could be removed by etching the surface with nitric and hydrofluoric acid before and after irradiation. The impurity concentration has been found to be generally increased in the process of single crystal growth. The vertical and radial distributions of impurities have revealed that some impurity elements were more concentrated in the top region of a single crystal rod than in the middle region, and that Br, Cr, La, Eu and Sb were enriched in the central region and As, U and Fe in the outer region.
Abstract
A quantitative analysis of an ancient Buddha statue was performed by external beam Proton Induced X-ray Emission for the purpose of identifying its originality. It is shown how the PIXE method can be applied for archeological study. The elemental composition of the statue is compared with that of several samples with definite ages. The experiment was performed by extracting 2.4 MeV proton beam through a 2 mm diameter collimator and 7.6 
m kapton foil to the He atmosphere. X-rays were measured by a Si(Li) detector. The analysed elements were Fe, Cu, Ag, Au and Hg for gold coating and Fe, Ni, Cu, Zn, As, Ag, Sn, Au, Pb and Bi for bronze body.
Abstract
This report describes the environmental sample treatment techniques for14C measurement with liquid scintillation counter. The groundwater sample of about 80 liters was collected from well and inorganic carbon was removed by acidification and recirculated gas stripping with the extraction efficiency of more than 98%. The biological samples were freeze-dried and combusted to carbon dioxide in high pressure combustion unit with a combustion efficiency of nearly 99%. The14CO2 in the stack effluents was collected by an air bubbler with a collection efficiency of more than 99% for a sampling time of two weeks. Sampling of14C in reduced form also has been done by passing the gases through a tube furnace with Pt/Al and Pd/Al catalyst. Active and passive sampling methods for atmospheric14C measurements were compared in detail, and it could be concluded that the uncertainty associated with passive sampling method was quite acceptable for environmental monitoring. The CO2 trapped in NaOH was precipitated as BaCO3, and subsequently reconverted to CO2 for environmental samples and transferred to Carbo-Sorb ETM for liquid scintillation counting. In case higher precision is the deciding factor, benzene synthesis would be employed with home-made benzene synthesizer.
Abstract
Neutron capture cross sections on 63Cu and 186W were measured by fast neutron activation method at neutron energies from 1 to 2 MeV. Monoenergetic fast neutrons were produced by 3H(p,n)3He reaction. Neutron energy spread by target thickness, which was assumed to be the main factor of neutron energy spread, was estimated to be 1.5% at neutron energy of 2.077 MeV. Neutron capture cross sections on 63Cu and 186W were calculated by reference comparison method on those of 197Au(n,γ). Not only statistical errors of gamma-counts from samples but also systematic errors in the counting efficiency for HP Ge detector and the uncertainty of areal density of samples were considered in calculating neutron capture cross section. Estimated neutron capture cross sections on 63Cu and 186W were also compared with ENDF-6 data.
