Thermal neutron activation

The major advantage of the TNA technology is that it can produce a nitrogen map and many important explosives have a high nitrogen content. The neutrons 

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Thermal neutron activation analysis has been used for archeological samples, such as amber, coins, ceramics, and glass biological samples and forensic samples (see Forensic chemistry) as weU as human tissues, including bile, blood, bone, teeth, and urine laboratory animals geological samples, such as meteorites and ores and a variety of industrial products (166). 

MetaUic impurities in beryUium metal were formerly determined by d-c arc emission spectrography, foUowing dissolution of the sample in sulfuric acid and calcination to the oxide (16) and this technique is stUl used to determine less common trace elements in nuclear-grade beryUium. However, the common metallic impurities are more conveniently and accurately determined by d-c plasma emission spectrometry, foUowing dissolution of the sample in a hydrochloric—nitric—hydrofluoric acid mixture. Thermal neutron activation analysis has been used to complement d-c plasma and d-c arc emission spectrometry in the analysis of nuclear-grade beryUium. 

Picatinny Arsenal Thermal Neutron Activation Analysis Facility. N... 

H. Kramer, S. Semel J.E. Abel, Trace Elemental Survey Analysis of Trinitrotoluene , PATR 4767 (1975) (An evaluation of the applicability of spark source mass spectrometry and thermal neutron activation for the detn of origin-related trace elemental impurities in TNT) 10) C. Ribando J. Haber-man, Origin-Identification of Explosives Via Their Composite Impurity Profiles I. The... 

This can result in a radioactive product from the A(n, t)A reaction where A is the stable element, n is a thermal neutron, A is the radioactive product of one atomic mass unit greater than A, and y is the prompt gamma ray resulting from the reaction. A is usually a beta and/or gamma emitter of reasonably long half-life. Where access to a nuclear reactor has been convenient, thermal neutron activation analysis has proven to be an extremely valuable nondestructive analytical tool and in many cases, the only method for performing specific analyses at high sensitivities... 

For the thermal neutron activations, a lOmg Callfornium-252 (252Cf) source was utilized in a modi ll notomhlii mnc.fn tsd. from a Neutron... 

Thermal neutron activation was selected for the radioassay via the soTi(n,7)s 1 Ti reaction. Since the half-life of 51Ti was 5.8 min, nondestructive NAA by gamma-ray spectrometry was used in lieu of chem sepn of Ti... 

The pertinent neutron activation data for the determination of Ba and Sb in gunshot residues by (n,y) thermal neutron activation is given in Table 8... 

Rare earth elements, with relatively high thermal neutron activation cross-sections, have been tested or considered as tagging species for this purpose. At GA (Ref 8), preliminary expts were conducted with 0.38 cal ammo using dysprosium (Dy) and europium (Eu) deposited on the wall of the cartridge case and in the gunpowder, and Dy, hoKnium (Ho) and indium (In) in the primer. 

The properties of such materials are not measurably altered until subjected to doses in excess of a million rads. At these higher doses, the principal changes are due to chem decompn which, with very few exceptions, resnlt in a decrease in sensitivity to mechanical stimulus and also in a dimunition of expl output. The radiation doses normally encountered in neutron activation procedures range from a few rads for 14 MeV fast neutron activation to several thousand rads for thermal neutron activations in a nuclear reactor. Thus, such doses are well under the limit at which measurable changes can occur... 

The EC decay of (ty2 = 140 days), which is produced from by thermal neutron activation in a nuclear reactor, populates the two Mossbauer levels of Ta at excitation energies of 6.2 and 136.2 keV. 

The two Mossbauer levels of Pt, 99 keV and 130 keV, are populated by either EC of Au(fi/2 = 183 days) or isomeric transition of Pt(fi/2 = 4.1 days). Only a few authors, e.g., [323, 324] reported on the use of Pt, which is produced by thermal neutron activation of " Pt via " Pt(n, y) Pt. The source used in the early measurements by Harris et al. [322, 325] was carrier-free Au diffused into platinum metal. Walcher [326] irradiated natural platinum metal with deuterons to obtain the parent nuclide Au by (d, xn) reactions. After the decay of short-lived isotopes, especially Au(fi/2 = 6.18 days), Au was extracted with ethyl acetate, and the Au/Pt source prepared by induction melting. Buym and Grodzins [323] made use of (a, xn) reactions when bombarding natural iridium with... 

Nuclear bombardment reactions in which the product is radioactive constitute the basis of radioactivation analysis (p. 456). Although in principle any bombardment-decay sequence may be used the analyst is largely concerned with thermal neutron activation. Equation (10.13) relates the induced activity to the amount of the parent nucleide (analyte). However, practical difficulties arise because of flux inhomogeneities. It is common therefore to irradiate a standard with very similar characteristics alongside the sample, e.g. for a silicate rock sample a standard solution would be evaporated on to a similar amount of pure silica. On the assumption that identical specific activities for the analyte are then induced in the sample and standard, the amount w2 of analyte is readily calculated from... 

Randle and Hartman [12] used thermal neutron activation in analysis to investigate total bromine in humic compounds in soil. Bromine was extracted from the soil water with sodium hydroxide or sodium pyrophosphate, then the extract dried prior to analysis. 

Environment Assessment of the Thermal Neutron Activation Explosive Detection System for Concourse Use at U.S.Airports, US Nuclear Regulatory Commission, NUREG-1396,... 

Twitty BL, Boback MW. 1970. Rapid determination of thorium in urine by thermal neutron activation analysis. Anal Chim Acta 49 19-24. 

Lutetium occurs in nature in small amounts in yttrium-containing minerals. It is found in xenotime, precambrian granites, and North American shales. It also exists at 0.001% in monazite, from which the metal is produced commercially. Lutetium has very httle commercial apphcation. The metal emits beta particles after thermal neutron activation, and is used to catalyze organic reactions. 

Ldnnerdal, B., Stanislowski, A. G., Hurley, L. S. J. Inorg. Biochem. 12, 71 (1980) Woittierz, J. R. W. Elemental Analysis of Human Serum and Human Serum Protein Fractions by Thermal Neutron Activation, Netherlands Energy Research Foundation Report, ECN 147, January 1984... 

Thermal Neutron Activation Analysis Activation thermal neutrons 30 min in flux,... 

This study is concerned with the comparison of data from x-ray fluorescence (2), electron microprobe (2), and thermal neutron activation (3) techniques with the metallurgical structure of the sample. The maximum precision which can be expected from all of these techniques, with normal precautions, is 5%. In all cases, the analytical parameters used in the measurements reported here were chosen to maximize the sensitivity and precision for silver-based alloys. The parameters used in each technique are listed in Table II. 

Thermal Neutron Activation Analysis (NAA). The amount of sample adhering to the quartz sampling plate is variable. It is normally considered to be of the order of 100-200 /xg. Because of the size of the metallurgical samples available for this study, the average mass sampled was estimated to be in the range 1-5 /xg. 

Thermal neutron activation analysis was done on small samples from Sasanian silver objects to determine the concentrations of three major elements, Ag, Cu, and An, and 16 trace elements, Na, K, Sc, Cr, Mn, Fe, Ni, Co, Zn, As, Br, Sn,... 

T1he elemental composition of ancient silver objects is a potential source of information on the kind of ores used to produce silver, the location of these ores, the ancient metallurgy used to extract the silver, and the trade routes through which they passed. As part of a comprehensive study on Sasanian silver at the Metropolitan Museum of Art we used thermal neutron activation to analyze small samples from silver objects... 

In this report we describe our quantitative analyses for three major components and for 16 trace elements present from parts per billion (ppb) to parts per million (ppm) in Sasanian silver by thermal neutron activation analysis. The analytical data are discussed element by element. Some of the conclusions which can be drawn from the objects are discussed. Since the amount of comparative data available is too small for generalizations, many of our conclusions and assumptions are subject to change when more data and information become available. 

In order not to disfigure valuable ancient silver objects, only minute specimens can be removed for analysis. Sample size is thus a major restriction on the analytical method chosen. Thermal neutron activation analysis provides excellent opportunities for quantitative multi-element analysis of these small samples. The question as to how accurately these samples represent the entire specimen is considered in detail later. 

The cross sections for (n,y) reactions common in reactor thermal neutron activation generally decrease with increasing neutron energy with the exception of resonance-capture cross section peaks at specific energies. This reaction is, therefore, not important in most 14 MeV activation determinations. However, some thermalization of the 14 MeV flux may always be expected due to the presence of low Z elements in the construction materials of the pneumatic tubes, sample supports, sample vial, or the sample itself (particularly when the sample is present in aqueous solution). The elements Al, Mn, V, Sn, Dy, In, Gd, and Co, in particular, have high thermal neutron capture cross sections and thermal capture products have been observed in the 14 MeV neutron irradiation of these elements in spite of care taken to reduce the amount of low Z moderating materials in the region of the sample irradiation position 25>. 

It is obvious, therefore, that 14 MeV neutron activation analysis can not compete with thermal neutron activation analysis as a technique for trace element analysis. In simple matrices, however, the rapid and non-destructive nature of the technique recommends its use for routine analysis of large numbers of samples for elemental abundances at the one milligram level, or above. It is unfortunate that the element carbon can not be determined by this technique. The nuclear reaction 12C(n, 2n)1 C which would be of great analytical importance is endoergic to the extent of nearly 19 MeV. This reaction is obviously not energetically possible using the 14.7 MeV neutrons produced by the 2H(3H,w)4He reaction commonly employed in most neutron generators. 

Table 2. Thermal neutron activation determinations using gamma-gamma coincidence counting techniques...

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