Comparison of a coaxial Ge(Li) and a planar Ge detector in instrumental neutron activation analysis of geologic materials

Instrumental neutron activation analysis was made on three different rock samples and on mineral separates of plagioclase, pyroxene and magnetite. γ-spectra were recorded using both a coaxial and a planar Ge detector. Counting errors were compared for those elements that could be determined with both detectors. In nearly all cases, analyses using the planar detector yielded smaller errors. The use of this detector in instrumental analysis is of particular advantage, where only contents of rare earth elements are to be determined.     

Routine multielement instrumental neutron activation analysis of silicate rocks using short-lived radionuclides

By means of thermal neutron activation and countings on the small planar and large coaxial Ge(Li) detector, 13 elements are determined in various silicate rocks, using short-lived radionuclides with half-lives from 2 min to 15 h. A method of routine analysis with simple dead-time and pile-up correction is described and tested with the standard rocks AGV-1 and G-2.     

Trace multielement analysis in boron materials by epithermal neutron activation analysis

A method, based on epithermal neutron activation analysis using a boron filter is described for the determination of ～60 trace elements in boron and its compounds. The method has an accuracy of ～20%, a precision of ～15% RSD and limits of detection for most elements are either at the sub-ppm or low ppm levels. The method requires no sample preparation and is economical in effort.     

Multielement photon activation analysis of coal samples using a Compton suppressed Ge(Li) detector

Multielement photon activation analysis has been carried out using a Compton suppressed Ge(Li) detector. The irradiated samples were N.B.S. standard reference coals and ashes. An increase in sensitivity by as much as a factor of three is attainable for some elements and this is especially valuable when analysing coals with low trace metal concentrations like N.B.S. reference material 1635.     

Relative efficiency calibration of Ge(Li) detector in low energy region

The relative gamma-ray intensities in the energy region between 122 and 411 keV in the decay of¹⁵²Eu were measured by using a Ge(Li) detector. Its efficiency calibration was carried out with the radioactive sources of²⁴¹Am,⁵⁷Co,²⁰³Hg,¹³⁷Cs,¹³³Ba,⁷⁵Se,¹⁶⁹Yb and¹⁹²Ir.     

Application of an Apple IIe microprocessor for data acquisition and analysis in instrumental neutron activation analysis with a low energy photon detector

The determination of thirteen elements, eleven rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Ho, Tm, Tb and Lu), thorium and uranium were performed by instrumental neutron activation analysis for four geological reference materials (G-2, AGV-1, GSP-1 and SY-2) as well as our laboratory rare-earth standard. The analyses were performed using a low energy photon detector coupled to an Apple IIe microprocessor employed as a multichannel analyzer not only to collect the data but also for data analysis. Finally, based on this work we have proposed a simple, rapid routine method for the determination of eleven rare-earth elements, thorium and uranium in geological materials employing IVIC's RV-1 nuclear reactor.     

The determination of tellurium in geological materials using radiochemical neutron activation analysis with a low energy photon detector

A method is described for the trace level determination of Te in geological materials with a detection limit of 5–10 ppb. Destructive thermal neutron activation analysis is used with relatively simple radiochemistry employing efficient precipitation and ion exchange techniques. A germanium Low Energy Photon Detector (LEPD) is used for radioassaying which allows the relatively aboundant X-rays from^123mTe to be measured. This radioactive isotope emits Te Kα and Kβ X-rays at 27–31 keV which are readily resolved by the LEPD and therefore allows interference effects from fission product Te to be minimised giving reliable trace level data of high accuracy. The validity of the method is demonstrated by reporting analytical data for Te in a range of USGS Standard Rocks.     

Determination of rare earths in silicate rocks by epithermal neutron activation and a simple group separation

The determination of nine rare earth elements in rock samples by epithermal neutron activation, followed by a simple group-separation procedure and Ge(Li) γ-ray spectrometry, is described. This method is found to be advantageous for the determination of Nd, Gd, Ho, Er and Lu by means of the short-lived nuclides¹⁴⁹Nd,¹⁵⁹Gd,¹⁶⁶Ho,¹⁷¹Er and^176m Lu. Precision for La, Sm and Eu is similar to that of thermal neutron activation, that for Dy is worse. Samples of the standard rocks, basalt BCR-1 and granite G-2, were analyzed by this procedure and the results obtained are compared with previously reported data.     

Determination of chlorine in silicate rocks by neutron activation analysis

A simple radiochemical neutron activation analysis scheme has been developed for the determination of chlorine in silicate rocks. The method involves a 15-min thermal neutron irradiation of rock powder followed by a quick separation of ³⁸Cl as AgCl, and Ge(Li) spectrometry. Chemical yield, normally ranging between 95% and 100%, is monitored gravimetrically through the recovery of AgCl. The procedure has been tested on several geochemical standards to assess its accuracy and precision. The values obtained for standard rocks agree with the literature values. At the 100-ppm level, the analytical precision for chlorine is within ±5% (2σ).     

A program for complete quantitative neutron activation analysis using Ge(Li) detector gamma spectrometry and a small computer

It is shown that the large sophisticated programs designed for big computers can be efficiently used on medium scale machines for complete quantitative neutron activation analysis with Ge(Li) detectors.     

Multi-element determination in silicate rocks by instrumental neutron activation analysis

Instrumental neutron activation analysis technique was applied for the determination of 20 elements in 54 silicate rock samples which belong to three sedimentary geological formations located in the western desert of Iraq. The samples along with USGS standards were irradiated in an IRT-5000 reactor at a neutron flux of 3.7·10¹³ n·cm^–2·s^–1 The following minor and trace element constituents have been determined: Na, K, Ca, Fe, Sc, Cr, Co, Zr, Ce, La, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Th and U.     

Precision and accuracy of rare earth determinations in rock samples using instrumental neutron activation analysis and A Ge(Li) detector

Some of the rare earth elements have been determined in U.S.G.S. Standard Rocks W1 and G2 using instrumental neutron activation analysis with a Ge(Li) detector. The experimental conditions were chosen to investigate the precision and accuracy to be expected when using the method for routine purposes. The results are compared with data obtained after chemical group separation of the rare earths and with data reported by other workers; the agreement is, in general, good. La, Ce, Nd, Sm, Eu, Tb, Yb, Lu and Se were determined with the instrumental method and, after group separation, data were obtained for Gd, Dy, Ho and Tm in addition. It is concluded that the accuracy of the data obtained with the non-destructive method is, in general, as good as the precision for each element.     

Determination of palladium by chemical neutron activation analysis using low energy photon spectrometry

A chemical neutron activation analysis method to determine trace amounts of palladium present in the uranium ores has been developed. Palladium was concentrated on an anionic exchanger to purify from large amounts of uranium, iron and copper that were present in the ore. The resin in which Pd was adsorbed was neutron irradiated and the activation product¹⁰⁹Pd was assayed through its daughter^109mAg by low energy photon spectrometry to estimate palladium. Both the 88 keV gamma-line and the 22 keV X-ray line (arising out of the internal transition of^109mAg) were used to arrive at the concentration values by a standard comparison technique. A thin window Si(Li) detector and an HPGe detector were used for the radioactive assay. Detection limits and the advantage of using the X-ray line of Ag over that of the gamma-line were discussed. An absolute detection limit of 0.12·10⁻⁹ g could be arrived at by the use of the 22.10 keV X-ray line in an interference-free condition.     

Interference from uranium in neutron activation analysis or rare-earths in silicate rocks

A direct nondestructive method of analysis for²⁴¹Am utilizing photon counting and self-absorption correction factors is presented. The method gives favorable agreement for samples analyzed by radiochemical separation procedures and alpha particle spectrometry. The comparison was made over a range of approximately five orders of magnitude of²⁴¹Am concentrations. The method is reliable and relatively simple. Sensitivity for a ∼5-g sample and a counting intervals of 60 000 s is ∼0.2 pCi/g with an uncertainty of ±22%, which decreases to ±11% for increased counting intervals of 150 000 s and an increased sample size of ∼20 g.     

Some practical procedures in computerized thermal neutron activation analysis with Ge(Li) gamma-ray spectrometry

The practical use of a correction procedure for random coincidence losses, the determination of the detection limit and the standardization of measuring conditions are described. Special correction methods for the interference of the Cu analysis by²⁴Na, the burn-up of the radioactive nuclide formed and the interference of the Pt determination by Au are also given.     

A well-tested procedure for instrumental neutron activation analysis of silicate rocks and minerals

Procedures for instrumental neutron activation analysis (INAA) have been developed and used on more than a thousand small samples of terrestrial and lunar silicate rocks and minerals for determination of Co, Cr, Fe, Hf, Na, Ni, Sc, Ta, Th, and the rare earths La, Ce, Sm, Eu, Tb, Yb, and Lu. Precision has been determined by repeated analysis of Knippa basalt and DTS-1 to be better than ±5 percent for all elements except Ni, Yb, Lu, and Hf. Mean values and estimates of accuracy are given for Knippa basalt and USGS standards AGV-1, G-2, GSP-1, and W-1. Important features of the method are its precision and ease of data reduction.     

Gamma-ray photopeak interferences found in the instrumental neutron activation analysis of silicate rocks

Data are tabulated to identify all major and minor gamma-ray interferences which may effect the area determinations of analytical photopeaks for all principle isotopes (of half life greater than about one day) encountered during the routine instrumental neutron activation analysis of silicate rocks. These photopeaks cover the energy range 60–1700 keV and are based on data abstracted from ERDTMANN and SOYKA.⁸ Interferences are listed down to relative intensities of 0.001% and include principle sum peaks. Photopeaks which are considered to be most reliable for routine quantitative analysis are identified.     

Analysis for the rare-earth elements by neutron activation and Ge(Li) spectrometry

A procedure for analysis of 12 of the rare-earths, tested on more than a hundred samples of rocks and minerals, is described. Carrier is added for each element to be determined. Samples are fused with Na₂O₂. The rare-earths are separated as a group, then precipitated and mounted as oxalates for Ge(Li) spectrometry. Following radioassay, chemical yields for the individual rare-earths are obtained by irradiation and counting of the carrier. About two months are needed to obtain complete data for a set of four samples, but many samples are analyzed concurrently. The precision and accuracy exceed ±5 per cent for 10 of the elements in 0.1 to 0.5 g samples of common rocks.     

Rare earth element determination in silicate rocks using neutron activation analysis and mass spectrometry

A pre-irradiation group separation procedure for the quantification of 11 to 13 rare earth elements (REE) in geological materials by neutron activation analysis, with yield determination by mass spectrometry isotope dilution analysis of Sm and Nd, is described. Utilization of the shorterlived isotopes of the REE allow sufficient data for most geochemical studies to be obtained within one day of irradiation, although where necessary additional information may be obtained following a decay period of three to four weeks. Analysis of selected USGS rock standards shows the method to be both accurate and precise.