A nitrogen gas cooling device for operation in neutron activation analysis

Gamma spectrum of a cement sample is not straightforward to analyze as a result of peak overlapping produced by Compton effect of gamma rays radiated from activated elements in the neutron activation process and also because of the change into the neutron energy spectrum in the target sample during activation. Artificial neural network (ANN) is an excellent solution for complex and nonlinear systems. Consequently, the use of ANN for quantitative analysis of major cement elements including Ca, Si, Al, and Fe would be very advantageous. Iranian inertial electrostatic confinement fusion device is a fast, monoenergetic and steady neutron generator. It was simulated as a high-energy neutron source for performing neutron activation analysis. In the present study, a library of 29 members of delayed gamma-ray spectra of knowing cement samples were generated via MCNPX version 2.7. Specific photo-peaks related to Ca, Si, Al and Fe obtained from these spectra were used as inputs for ANN (21 of them for training and 8 for testing). Then, using MLP architecture, an ANN model has been presented to model the system to predict the percentages of the elements in cement. The ANN model is optimized to have only a hidden layer with five neurons. The comparison between modeling data and results of proposed MLP network shows that there is a good consistency between them. The MAE of training set for Ca, Si and Fe outputs were 0.0351, 0.0656 and 0.0660, respectively, and the MAE of testing set for mentioned outputs were 0.0997, 0.3046 and 0.8699, respectively. Overall, it can be concluded that the defined dispensable errors show that this modeling is a good one as a prediction tool for the mentioned purpose.

The measurement of impurities, specifically; the combination of magnesium, silicon and aluminum, in polymers and in mixed additives is a common problem for industrial application of neutron activation analysis (NAA). Typically this problem can be addressed using XRF and ICP. However, in some cases, the available sample size, desired detection limit and the desired accuracy prohibit the use of XRF or ICP. Therefore under these requirements, as in the measurement of talc in milligram size polymer fibers, using NAA has become a niche for nuclear analytical applications. Other important advantages, apart from high precision and lower detection limit, are the non-destructive nature of the analysis and the minimal sample preparation necessary to carry out the measurement. Therefore, polymers such as polyethylene, polystyrene or poly-carbonate can be analyzed for these metals as organic solutions, beads, films, pellets or powders. This paper highlights some of the recent improvements made to the Dow NAA measurement facility to accomplish this task.

Yield calculation for delayed gamma-ray neutron activation analysis

An application of neutron activation analysis to small biological samples: simultaneous determination of thirty elements in rat brain regions

Used lubricating oil analysis programs are currently employed by both the military and industry in an attempt to minimize some of the costs associated with equipment failure. The periodic determination of water elements in the lubricant of an oil-wetted system can provide very useful information on the condition or health of the system and an early indication of impending failure. In the present study, the application of Neutron Activation Analysis (NAA) to used oil analysis was investigated. The method developed allowed for the determination of fifteen elements (Ag, Al, Cl, Cr, Cu, Fe, In, Mg, Mn, Mo, Na, Ni, Sn, Ti and Zn) associated with engine wear or deterioration. Results obtained for the analysis of used naval diesel oils exhibited good agreement with results obtained by Atomic Absorption Spectrophotometry (AAS) methods. A drawback of the NAA procedure is that the determination of Fe, a major wear element in most systems, involves an analysis time of approximately one week.

New generation non-stationary portable neutron generators for biophysical applications of Neutron Activation Analysis

The difficulties of analyzing plastics of high purity by chemical analysis methods have led to the application of neutron activation analysis. Because literature quotes pressure build-up in the irradiation containers as the reason for limited activation intensity the behavior of the six plastics PVI, PMMA, PVDF, PE, FEP and Silicone had to be investigated. The investigations showed, that pressure build-up was not the limiting factor. Furthermore hydrogen generation under irradiation seems to be the reason for explosions of ampoules by an oxyhydrogen reaction. The question of the ignition source could not be answered yet. To prevent oxyhydrogen reaction, the ampoules have to be filled with nitrogen. The experiments have shown, that if suitable sample masses and ampoule volumes are selected, even high neutron fluences can be applicated. After determining the permissible irradiation conditions, the impurity content of 30 elements in the six plastics were determined using destructive and nondestructive NAA.

For89Sr and90Sr determination in grass samples neutron activation analysis was employed as an advantageous method for yield measurements during the separation process. From the activity ratio found conclusions on the source of radioactivity are possible taking into consideration the dependence on reactor operating time.

The Application of Neutron Activation Analysis to Forensic Science

Total body nitrogen (TBN) was determined in 16 rat carcasses ranging in weight from 55 to 550 g, by non-destructive 14 MeV neutron activation analysis (NAA). The rat carcasses were subsequently analysed for TBN by Kjeldahl digestion, for total body water (TBW) by loss of weight after freeze-drying and for body fat by adiabatic bomb calorimetry after subtraction of protein energy. TBN results by the two methods were in good agreement, the precision by NAA (coefficient of variation = 1.5%) being superior to that by chemical analysis (coefficient of variation = 2.8%). Body fat calculated by difference from a combination of measured TBW and NAA data agreed closely with bomb calorimetry measurements. The use of indirect estimates of TBW to determine fat gave poor results. A group of four growing rats was analysed sequentially by NAA four times in 2 weeks. The maximum total radiation dose received by each animal was less than 50 rem (less than 500 mSv) and no significant differences in growth rate were observed compared with non-irradiated control groups. 14 MeV NAA in vivo can be conducted with sufficient precision to measure 0.14 g TBN changes in growing rats at 2 weeks post-weaning.

The preparation of internal reference material NSC-21 Compost Vitahum, including its stabilization, homogeneity testing, and evaluation of an interlaboratory comparison in which 19 laboratories took part using several analytical methods is described. From the results of the intercomparison, consensus values were derived for the contents of Cd, Cu, Ni, Pb, and Zn, whereas for As, Co, Cr, Fe, Hg and Mn, information values were derived. Bimodal distribution of the As and Cr results was obtained, presumably because of incomplete dissolution of the elements from the matrix if insufficiently aggressive decomposition procedures were employed. Some problems encountered were elucidated by application of neutron activation analysis (NAA) in its nondestructive and destructive (radiochemical) modes.

In this work, the most important limitations for qualitative and quantitative analysis using reactor neutrons for activation are reviewed. Each limitation is discussed using different examples of activated samples. Photopeak estimation, nuclear reactions interference and neutron flux measurements are taken into consideration. Solutions for high accuracy evaluation in neutron activation analysis applications are given.

Membrane optode for mercury(II) determination in aqueous samples

The application of neutron activation analysis to leach rate studies

Acta Pharmacologica et ToxicologicaVolume 59, Issue s7 p. 585-588 APPLICATION OF NEUTRON ACTIVATION ANALYSIS IN CLINICAL CHEMISTRY. R. Cornelis, R. Cornelis Laboratory for Analytical Chemistry, Rijksuniversiteit Gent, Proeftuinstraat 86, B-9000 Gent, Belgium. R. Cornelis is a senior research associate of the National Fund for Scientific Research.Search for more papers by this author R. Cornelis, R. Cornelis Laboratory for Analytical Chemistry, Rijksuniversiteit Gent, Proeftuinstraat 86, B-9000 Gent, Belgium. R. Cornelis is a senior research associate of the National Fund for Scientific Research.Search for more papers by this author First published: December 1986 https://doi.org/10.1111/j.1600-0773.1986.tb02831.x AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume59, Issues7December 1986Pages 585-588 RelatedInformation