Fast Neutron Activation Method Research Articles

Improved System for Inspecting Minefields and Residual Explosives

A next generation system, as an upgrade of a robotic mobile system for anti-personnel landmine clearance, was considered. In contrast to the first generation system where the fast neutron activation method and the associated alpha particle imaging (API) was supposed to be used for finding the residual explosives and/or landmines, in the next generation system fast neutrons (FN) was considered to be used only for the confirmation of the explosive in the suspected object previously found by the ground penetrating radar (GPR), metal detector (MD) and infrared imaging (IR). Such system is expected to have the acceptable price and the optimal demining vehicle speed of 10 cm/s. In contrast to the previous system only one neutron generator (NG) is needed. In order to study the possibility of FN to confirm the presence of TNT explosive in the real environment the tests were made with the soil of different moisture contents. Comparative study was done by using the 7.62 cm × 7.62 cm BGO, 7.62 cm × 7.62 cm LaBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> : Ce and 7.62 cm × 7.62 cm NaI(Tl) gamma-ray detectors. Although nitrogen was easily detected in larger amount of TNT explosive, its signal was weak in detection of Anti-Personal (AP) mine like DLM2.4. The presences of soil additionally diminish the possibility of nitrogen detection even in the Anti-Tank mines (AT).

Verification of nuclear effect of acoustic cavitation using fast neutron activation method

Verification of nuclear effect of acoustic cavitation using fast neutron activation method

Inspecting Minefields and Residual Explosives by Fast Neutron Activation Method

As an upgrade of a robotic mobile system for anti-personnel landmine clearance, a fast neutron probe has been considered for the detection of mines and explosive residues. Laboratory tests were made by using the 14 MeV $6\times 10^{7}$ neutrons/sec beams with the associated alpha particle detection and with a ${\rm LaBr}_{3}$ gamma-ray detector. Simulant of the anti-personnel mine was used as a target. Several measurements were made with the target buried into the soil at different depths. For each depth minimal time measurement was estimated for false negative 0.4% and false positive equal to 10%. Tests showed that it is possible to detect buried landmines as well as residual explosives; however, in order to reach the optimal speed of 10 cm/s of the demining vehicle it is necessarily to use several sealed tube neutron generators and few dozen of ${\rm LaBr}_{3}$ gamma-ray detectors.

Measurements of fast neutron capture cross sections on 63Cu and 186W

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.

Radiochemical fast neutron activation analysis of high-purity metals for phosphorus

A fast neutron activation method for the determination of phosphorus in high-purity materials was developed. It is based on the {sup 31}P(n,p){sup 31}Si reaction and the radiochemical separation of the indicator radionuclide {sup 31}Si by distillation as silicon tetrafluoride followed by counting the {beta} activity with a liquid scintillation system. Fast neutrons were produced by bombarding a thick beryllium target with deuterons, using an irradiation system with a rotating sample holder. The dependence of the sensitivity and of the extent of primary interference reactions included on silicon, sulfur, chlorine, and potassium on the deuteron energy was investigated in the energy interval 23-53 MeV. For a deuteron energy of 53 MeV, a beam intensity of 10 {mu}A, and an irradiation time of 2.5 h, a limit of detection of 3 ng/g is achievable. The method was applied to the determination of phosphorus in different metals, and the results obtained were compared with those found by other methods.

In-vivo and in-vitro measurements of lead and cadmium

Tibia lead is measured in vivo using X-ray fluorescence. A(109)Cd source is used to excite Pb K X-rays, and this signals is normalized to that from Rayleigh scattering to remove geometrical variations. The lower limit of detection is 10 μg/g for a mean absorbed dose, to the exposed section of the leg, of 100 μGy. Tibia lead correlated positively with age in normal volunteers (r=0.615,p=0.004) and with duration of exposure in occupationally exposed subjects (r=0.847,p=0.0001). When the X-ray fluorescence technique was applied to autopsy specimens previously analyzed by atomic absorption spectrometry there was excellent agreement between measurement techniques.Cadmium is measured in vivo by neutron activation analysis. The detection limit in liver is 6.5 μg/g for a local skin dose equivalent of 0.5 mSv and in kidney is 6.4 mg for a dose equivalent of 0.9 mSv to the skin. Detailed analysis of the γ-ray spectrum will produce only slight improvements in detection limit. Uncertainties in organ position during measurement, even after ultrasonic localization, are likely to produce uncertainties of 20-25% in cadmium measurement. Autopsy samples were measured, using a fast neutron activation method, from people previously measured in vivo. The results are broadly consistent, but show differences greater than those accounted for by counting statistics.

A determination of the solubility of lithium oxide in liquid lithium by fast neutron activation

The solubility of lithium oxide in liquid lithium has been measured in the temperature range of 195 to 734°C. A direct sampling method was employed in which nickel sampling tubes fitted with 2 μm pore size filters were used to take samples of the oxide-saturated lithium. The samples, still contained in their sampling tubes, were analyzed for oxygen content by a fast neutron activation method. A value for the oxygen blank attributable to the sampling tubes was derived from a regression analysis of the individual solubility data points. The resulting solubility values are considerably lower than those reported by previous investigators and can be represented by the equations In S( mol% Li 2 O) = 6.054–6669/ T, log S ∗(wppm oxygen) = 6.992–2896/T . The results indicate that removal of oxygen from lithium to a level of about 7 wppm (the solubility at 200°C) by cold trapping or by filtration should be feasible.

Oxygen in coal ash: a simplified approach to the analysis of ash and mineral matter in coal

Oxygen was determined accurately in eight U.S. Bureau of Mines coal ash samples A, B, D, F, G, I, and J, NBS coal fly ash 1633 reference material, and two low-temperature ashes (LTA) from lllinois State Geological Survey. The method uses fast-neutron activation (FNA) analysis employing a dual counting and irradiation system which is essentially free from interferences. The stoichiometric balance based on analyses of the ashes performed by the USBM is calculated and summations given in oxide and element percent. Excellent agreement is found with the chemical data obtained by classical silicate analysis methods. Accurate oxygen determination for coal ash and LT-ash (or mineral matter) is important for calculation of data in the ultimate analysis of coal as such. Knowledge is required for recalculation of the data on a dry and dry-ash-free basis. The routinely used ‘oxygen by difference’ values are inadequate for accurate work. In order to determine the organic oxygen in coal one also has to correct for oxygen in mineral matter and oxygen in the water removed as moisture. The Parr formula and other methods of empirical estimation are inadequate and may be replaced in some cases by the oxygen determination. The complete data provide a quantitative basis for stoichiometric interpretation of coal analyses. It was found that the eight coal-ash samples analysed contained 45.5 ± 3% oxygen. Since these ashes represent a large variety of U.S. coals, this figure can be used as an estimate for recalculation and evaluation of the proximate and ultimate coal analyses. It is better, however, to use values actually determined in ash by the rapid fast-neutron activation method. This permits a better estimation of the sum of cations plus sulphates in the ash.

Material balance in coal. 1. Material balance and oxygen stoichiometry of six coals from Wyoming

Oxygen was determined in six coals from the Wyodak Bed, Campbell County, Wyoming. Data from the U.S. Bureau of Mines' coal analysis reports were used to calculate the material balance of these coals based on accurate oxygen determination by a fast-neutron activation method developed at the University of California, Irvine. A computer program recalculates the data based on moisture determined in our laboratory and tabulates the results, comparing the ‘oxygen by difference’ to oxygen determined on ‘as received’ basis. Oxygen in samples dried at 105 °C was also determined in order to estimate the possible effect of oxidation and loss of volatile components other than water during the drying process. Summations of all data were derived using the accurate oxygen values determined. This approach permits a better interpretation of stoichiometry of coal analysis. The completeness of an analysis can be thus evaluated rapidly. One may be able to indicate and pinpoint probable errors in the determination of sulphur and nitrogen in coal, also the presence of considerable CaCO 3. The gross effect of evolution of CH 4 and gases other than H 2O can be detected. One also is able to estimate the composition of the coal ash and the low-temperature ash as well as the mineral matter (Parr basis) in terms of their varying total oxygen and cation contents. This work shows that five of these six soft, water-rich, coals (20–31% H 2O, 105 °C) do balance well stoichiometrically. One coal does not balance based on USBM moisture data. This is apparently due to an error in the moisture determination because oxygen data on this ‘as received’ versus ‘dried, 105 °C’ coal match very closely. It is shown how adding the oxygen determination to routine coal analysis may permit the coal chemist to interpret the data better in terms of true material balance. Oxygen is the only major constituent not routinely determined during the ultimate coal analysis. Adding this element permits the chemist to ascertain the accuracy of the analysis, completes the analysis in the sense of stoichiometry, and makes the customary summations of coal analysis more meaningful.

真空融解法による金属マンガン，アルミニウム中の酸素定量

The determination of oxygen in metallic manganese and high-purity aluminium has been made by the vacuum fusion method with a carbon chip-tin-nickel foil bath, the method being effective for the determination of oxygen in metals which involve violent evaporation and are difficult to react with carbon.In manganese, samples polished chemically and wrapped with a nickel foil (Mn:Ni foil=1∼2:2) was dropped in the crucible at 900°C and then the temperature was raised to 1550°C at the rate of 100°C/min and gases were extracted for 2 min. The oxygen extraction rate by this method was higher than those by the cupper bath and nickel-tin bath methods. The recovery of oxygen by this method was 97∼100 (%) in the known amount of manganese oxide and the deviation coefficient was within 6.6 (%) for electrolytic manganese.In aluminium, comparison of various bath methods indicated that the above-mentioned method and the iron-tin, copper and nickel-tin bath methods gave inaccurate results with incomplete extraction. By the addition of silicon to the carbon chip-tin-nickel foil bath, the oxygen extraction was increased and the results of determination were in good agreement with those by the fast neutron activation method. Samples electropolished and wrapped with a nickel foil was plunged in the crucible at 1400°C after the addition of 0.1 g of slicon and then the temperature was raised to 1800°C at the rate of 100°C/min and gases were extracted for 3 min.

The Reaction of Europium Oxide with Carbon Disulfide and Thermal Decomposition Processes of the Products

The synthesis of europium sulfide by the reaction of europium oxide with carbon disulfide was investigated, and oR these products the decomposition processeses on heating under some atmesphere were studied.The oxygen content was determined by fast neutron activation method, and the valence stqte of europium ion was estimated by the measurement of paramagnetic susceptibility at room temperature.By heating europium oxide in carbon disulfide vapor, Eu3S4 containing small excess sulfur was formed at 500. v600 C and EuS was formed at 900NIOOOeC. But, the contamination of small amount of carbon was observed in this case. The oxygen contepts in these Eu3S4 and EuS were O.9Nl.1 and O.2. vO.3, respectively.Europium monosulfide was also obtained by thermal decomposition or reduction of Eu3S4 in the stream of nitrogen or hydrogen. The oxygen content in the resultant europium monosulfide was also O.2, wO.3.Europium sulfide was very sensitive to oxidation. Therefore, under the atmosphere of oxygen europium monosulfide was oxidized to Eu202S and Eu, S4 at temperature above 200UC. By further oxidation, small amount of sulfur was removed at 650, v670 C, and the mixture of Eu202SO4and Eu2(SOs)s was formed at 750N8000C.

Determination of oxygen in aluminum electrolytic baths by a fast-neutron activation method

Oxygen in various materials can be determined by rapid, non-destructive fast-neutron activation analysis with a small neutron generator. The applicability of the method for determination of alumina in aluminum electrolytic baths, which is a very important factor in efficient aluminum metal production, has been studied. One of the major problems associated with this method is the interference of fluorine from cryolite. This difficulty has been eliminated by using a functional relation of the 16N/ 18F activity ratio and the oxygen/fluorine ratio in the sample. The alumina content in baths can be determined with a precision of 10–15% to 15–20% for 10–5% alumina concentrations.

速中性子放射化分析法の鉄鋼生産現場における酸素含有量制御への適用について

速中性子放射化分析法の鉄鋼生産現場における酸素含有量制御への適用について

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Application of a fast neutron activation method to the determination of oxygen in iron and steel

The determination of oxygen (0.001–0.2%) in iron and steel by the fast neutron activation method was investigated. The relative standard deviations of the method at oxygen levels of 0.1, 0.01, and 0.001%, were 3, 5, and 30%, respectively. The analytical results of the method were in good agreement with those of the conventional method in the range stated.

Determination of oxygen in titanium metal by a fast neutron activation method

The oxygen content of titanium metal was determined by bombarding samples with 14 MeV neutrons from a Cockcroft-Walton machine and measuring the 7.35 second nitrogen-16 gamma activity produced by the reaction 16O(n, p)16N. In this paper, optimum condition for the measurement of gamma rays of 16N, a correction for the absorption of gamma-rays by samples are discussed. The analytical results by this method are in good agreement with those by the vacuum fusion method. The sensitivity for oxygen is about 1000 counts/mg of oxygen and the standard deviation of the method at the level of oxygen concentration 0.1% is 4%.This method may be used to study the accuracy and the precision of the conventional method because the method is non-destructive.