Analysis of ancient iron objects with 14 MeV neutron activation analysis

Ancient iron objects excavated from five different sites around Nagpur city in Maharashtra State /India/ were cut into small pieces and samples were prepared. Each sample was irradiated with 14 MeV neutrons for 8 min. From the recorded gamma ray spectrum for each sample, the presence of trace elements Cu, Si, Al, Mg and Mn were detected and their mutual ratios of activities were determined. The results show that all the iron objects obtained from five different sites are of the same origin.     

Nondestructive 14 MeV neutron activation analysis of magnesium in spheroidal cast iron

The problem of determination of low magnesium concentration (0.02–0.13%) in the presence of a matrix of high activity (nearly 100% of iron) was solved. The²⁴Mg(n, p)²⁴Na(T=15.02 h) reaction was chosen. Since the neutron flux density decreasing with the distance from the target centre (r) slower than 1/r², a facility for simultaneous and long irradiation (1 hour) of six samples was performed. Time of decay t_d=24h. The determination limit corresponding to the 33% relative standard deviation amounted to 0.02% Mg (200 ppm).     

In vitro activation of bone with 14 MeV neutrons

Samples of compact bone, bone marrow and spongiosa of cow femur have been irradiated in vitro with 14 MeV neutrons. The Ca/P ratio for compact bone was found to be 2.16±0.24. The suitability of using 14 MeV neutrons and the³¹P(n, α)²⁸Al reaction for studying the bone mineral composition in vitro is discussed.     

Bulk material analysis using 14 MeV neutrons

There is considerable interest in bulk material analysis using energetic neutrons e.g. on-line coal analysis and down-hole logging. Recent work has indicated that an in-situ analysis of all the major elements of coal, using prompt capture and inelastic neutron scattering reactions, may be an operational possibility. The application of these techniques to oil well logging would allow the determination of lithology, porosity and oil and water saturation. Gamma-ray spectra arising from 14 MeV neutron bombardment of well characterised coal and fluid saturated rocks are presented. The gamma-ray intensities from both capture and scattering reactions are determined. Neutron transport modelling is used to evaluate the effect of variations in material content and the presence of trace neutron poisons. Predictions of carbon and oxygen scattering response are compared with the experimentally determined ratios.     

Use of 14 MeV neutrons in analysis of explosive class materials

Samples of explosive class materials were analyzed by 14 MeV neutron activation technique to estimate concentrations of oxygen, nitrogen, aluminium and chlorine. For aluminized explosives, test of stability against temperature was carried out by heating samples at 75 °C and loss of nitrogen was studied by measuring the ratio of aluminium to nitrogen in the sample. Loss of oxygen and nitrogen in a triple base propellant heated at 71.6 °C, was also estimated by measuring residual oxygen and nitrogen in the heated samples. This technique is convenient to adopt in the laboratory and useful to decide quickly the suitability of explosive class materials for practical applications.     

Precision in 14 MeV neutron activation analysis

The errors of analysis due to the different parameters involved in 14 MeV neutron activation analysis method are studied. Formulae to calculate these erros have been developed when possible. Otherwise they have been evaluated for special experimental situations. Special cases where some parameters become critical, as far as precision is concerned, have been mentioned.     

Sulfur determination in coal by 14 MeV neutron activation analysis

A procedure involving the irradiation of coal samples with 14 MeV neutrons and subsequent gamma-ray spectrometry of the irradiated sample for the estimation of solfur in coal, has been outlined. The samples were irradiated with 14MeV neutrons from a Cockroft-Walton type generator for one minute and then subjected to gamma-ray spectrometry for another minute using an automated transfer cyclic system. Ten such cycles were repeated for accumulating events under the 2130 keV gamma ray photopeak belonging to³⁴P (T=12.4 s) produced by the³⁴S(n, p)³⁴P reaction for assessing the lower level of detection, LLD, of Sulfur. Interferences due to the presence of other elements in coal were also determined. Sulfur can be determined at LLD of 0.25% in coal provided a 5 g sample of the coal is irradiated with a neutron flux of 5·10⁹ n·cm⁻²·sec⁻¹ assayed with a gamma ray spectrometer having a large hollow core Ge(Li) detector and an anti-Compton shield.     

Analysis of fertilizer phosphates using reactor neutrons and 14 MeV neutrons

Instrumental neutron activation analysis (INAA) in the absolute version was applied to 32 fertilizer phosphates of natural and industrial origin including three standard reference materials (NBS-SRM 120b, BCR-SRM No 32 and No 33). With reactor neutrons 48 elements were determined and with 14 MeV neutrons 3 additional elements were found. The results were used to assess the environmental toxicity of the fertilizers and to characterize their different origins.     

14 MeV neutron activation analysis of gold jewellery

Samples of nominal 18 carat and 21 carat gold jewelleries from the local market were non-destructively bulk analyzed using neutron activation analysis. Neutrons of 14 MeV energy were used with a fast pneumatic sample transfer system. The actual gold contents, as well as the composition of the base metals in these samples were determined. The fast neutron activation was found to be an efficient, quick and accurate method of characterizing the precious metal objects routinely in bulk, with a large sample throughput. The results demonstrate the commercial availability of the technique for non-destructive bulk analysis of precious metal objects.     

Determination of potassium in beet by 14 MeV neutron activation analysis

The applicability of 14 MeV neutron activation analysis for the determination of K in beet has been investigated by measuring the 2.167 MeV gamma-line from the decay of³⁸gK produced in the³⁹K(n, 2n) reaction. Beet samples were treated in different solutions of KCl and HgCl₂ to study the diffusion of K⁺ ions into the beet cells. The contribution of the gamma-line to the measured peak area from³⁸Cl produced in the³⁷Cl(n, γ) reaction was found to be 1%. Results obtained by fast neutron activation analysis and by flame spectrometry have been compared, and good agreements were found.     

Determination of silicon in aluminium by 14 MeV neutron activation analysis

A method has been developed for determining silicon in aluminium by fast neutron activation. It is based on the separation of two gamma lines by a Ge(Li) detector: the 1.73 MeV line from the product of²⁷Al(n, α)²⁴Na and the 1.78 MeV line from the²⁸Si(n, p)²⁸Al reaction. In the case of aluminium-silicon alloys 100 μg silicon can be determined, with an error of 10% in an aluminium sample of 1 g. This work was supported in part by the International Atomic Energy Agency.     

14 MeV neutron activation analysis using short-lived products

Cyclic activation using pneumatic shuttling system and switch off and on the neutron source and detector are described in order to eliminate some uncertainties by the provision of more accurate timing, the measurement of the effective activating neutron flux and the correction for the detection system dead time.     

Geometry errors in 14 MeV neutron activation analysis

The effects of inaccurate sample sizes and sample positioning on 14 MeV neutron activation analysis results are estimated for 30, 20 and 10 mm diameter targets. It appears that axial positioning is the most critical parameter and that using a larger tritium target will yield an overall improvement of the reproducibility. Aspirant of the N.F.W.O.     

Silicon determination in mine flue-dust by 14 MeV neutron activation analysis

The Si-contents of flue-dust and sedimented dust from Czechoslovak mines were determined by instrumental activation analysis with 14 MeV neutrons using a flux of 10⁷ cm⁻²·s⁻¹. The amounts determined range from 3 to 30 mg.     

Non-carbon-based compact shadow shielding for 14 MeV neutrons

We are developing a scanning spectroscopy system to measure prompt gammas-rays induced by inelastic neutron scattering and thermal neutron capture to non-invasively analyze soil in situ. Using a radiation source, a 14 MeV (d,t) neutron generator (NG), in a close proximity to the detection system without any precautions will flood and saturate the detectors with direct radiation. Therefore, we devized and partially optimized a shadow shielding sited between the source and the detection system; we discuss our experimental results and basic Monte Carlo calculations.     

Multielement analysis of a Milanese air-dust sample by 14 MeV neutron activation

The 14 MeV neutron activation technique is illustrated for multi-element analysis of a Milanese air dust sample. The neutron generator and electronic system, the efficiency and flux calibration, the -ray background, the sample preparation and the peak analysis used are described. After careful corrections of all possible interferences and error calculations, the results of 23 elemental concentrations are compared with those of other analytical techniques in the scope of an interlaboratory test.     

Thickness measurement of silicon films using 14 MeV neutrons

14 MeV neutron activation analysis technique is used to estimate thickness of silicon films deposited on glass plates. The elemental barium present in the glass plate was used as an internal monitor. Measured values of film thickness are in agreement within ±5% with the results obtained by weight method.     

Calculated screening effect in 14 MeV neutron activation analysis

The screening effect produced by a sample upon a standard located behind it is calculated. Curves for the secreening effect as a function of the sample material and of the sample depth are given.     

Optimum sample shape for 14 MeV neutron activation analysis

Based on the criteria of the maximum induced activity, the problem of the optimum sample shape was analyzed for a given volume of sample. Its shape was assumed to be cylindrical and the optimum values for the height-to-diameter ratio (presented in the included tables) were calculated under various circumstances. Coaxial and perpendicular sample—target irradiation geometries were considered.