Fast neutron activation

The fast neutron activation (FNA) technology was an outgrowth of attempts to get more information than nitrogen content from neutron interrogation approaches. In FNA, high-energy neutrons, rather than thermahzed neutrons, are used to scan the contents of a container. Gammas from neutrons inelasticaUy scattered on 

The inelastic scattered gammas from nitrogen are very weak and hard to detect in the detector pulse continuum. With low-energy resolution gamma detectors 

FNA systems only produce a 2D view with no depth profile. The systems usually have large a pixel size and subsequently a poor image. The pixel size is related to the size of the coUimated incident neutron beam and the spread of the neutron beam while traversing the thickness of the container. 

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The methods of choice for beryUium oxide in beryUium metal are inert gas fusion and fast neutron activation. In the inert gas fusion technique, the sample is fused with nickel metal in a graphite cmcible under a stream of helium or argon. BeryUium oxide is reduced, and the evolved carbon monoxide is measured by infrared absorption spectrometry. BeryUium nitride decomposes under the same fusion conditions and may be determined by measurement of the evolved nitrogen. Oxygen may also be determined by activation with 14 MeV neutrons (20). The only significant interferents in the neutron activation technique are fluorine and boron, which are seldom encountered in beryUium metal samples. 

Comparison of Various FNAA Techniques for Assay of Synthetic Octol Samples Precision of Single-Axis Rotation FNAA for Assay of Octol Plant Samples Fast Neutron Activation Analysis for Nitrogen in Explosives by... 

Triple-Axis Rotator for Fast Neutron Activation of Explosives. N... 

Fast Neutron Activation System for Inspection of Airline Baggage for the... 

Special Self-shielded Irradiation Cells for Fast Neutron Activation of... 

A modem technique for nitrogen detn is known as fast neutron activation analysis. Materials such as RDX are exposed to a high density fast neutron flux which converts the 14N content of the sample into unstable 13N. The N is detd by measuring the 13 N produced by the 14N (n, 2n) 13N reaction. This technique is extremely sensitive, but requires specialized instrumentation (Refs 44, 51 61)... 

Wilkniss, Fast Neutron Activation Analysis For Nitrogen in Explosives and Propellants , RadiochimActa 7 (4), 196—8 (1967) CA 68, 4570 (1968) 45) Anon, Fropeilant,... 

Fast Neutron Activation Analysis for Nitrogen in Explosives by Triple-Axis Rotation... 

For fast neutron activations, the samples were irradiated with a Kaman nuclear neutron generator (Model A711) under conditions similar to those described In this article under the section... 

Thermal neutron capture Fast neutron activation ... 

Fig 13 Fast Neutron Activation System for Inspection of rline Baggage for the Presence of Hidden Explosives (from Ref 10)... 

In 1972, the Lawrence Livermore Laboratory (LLL), also under Contract to the FAA, published a report (Ref 15) describing a more detailed statistical and exptl assessment of this same fast neutron activation method for inspecting bag-gaga for the presence of expls. The LLL approach was directed towards a more quantitative evaluation of the nitrogen content background likely to be encountered in ordinary passenger luggage... 

At PicArsn (Ref 19), the fast neutron activation approach for detection of expls in suitcases was extended to the activation of both nitrogen and oxygen using two 7-ray detector stations in sequence. After 14 MeV neutron irradiation, the baggage is first monitored for 6.1 MeV 7-rays from the l60(n,p),6N reaction (7.5 sec half-life), followed by measurement of the 10 min 13N. Because expls are also rich in oxygen and have characteristic ratios of N/O, it was felt that this approach would increase the probability of detection with a corresponding decrease in the false alarm rate... 

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... 

With regard to the hazard concern from physical and mechanical handling, the expl nature of the materials can pose a special problem. For example, during pneumatic transfer of samples in fast neutron activation, the polyethylene vials containing the expl approach speeds of 15m/sec and come to rest against a metal stop at both irradiation and count stations. However at PicArsn (Ref 13), in over 1000 irradiations and pneumatic transfers with up to 2.3g of shock-resistant secondary expls such as TNT, HMX,... 

A Preliminary Evaluation of Fast Neutron Activation to Detect Contraband Explosives at Airline Terminals , Lawrence Livermore Laboratory, UCRL Rept No 51284 (1972) 16) G. Borra... 

Several radiochemical studies have been reported, such as the analysis of phosphorus and chlorine by fast neutron activation and synthesis by radiochemical methods. ... 

Fast Neutron Activation Analysis Programming language Formula Translation Fourier Transform... 

Hult, M. and Fessler, A. (1998). Sr/Ca mass ratio determination in bones using fast neutron activation analysis. Applied Radiation and Isotopes 49 1319-1323. 

Fast Neutron Activation Facility at Pica-tinny Arsenal. A new fast neutron activation facility installed at PicArsn consists of ... 

The most common sources are based on the 3H(d, n) reaction. Deuterons are accelerated to 150 keV with currents 2.5 mA and strike a tritium target. They produce 2 x 1011 of 14-MeV neutrons/s under these conditions. The neutrons produced are widely used in fast neutron activation analysis for the determination of light elements. The tritium targets are typically metals such as Ti, which have been loaded with titanium tritide. The accelerators are usually small Cockcroft-Walton machines or small sealed-tube devices where the ion source and accelerator structure are combined to produce a less expensive device with neutron yields 108/s. 

FAST NEUTRON ACTIVATION ANALYSIS—John W. McKIveen SOLAR HEATING AND COOLING OF BUILDINGS—Richard S. Greeley ENVIRONMENTAL HEALTH CHEMISTRY—James D. McKinney ASBESTOS PARTICLE ATLAS—Walter C. McCrone CONTAMINANTS AND SEDIMENTS—Vol. 1 2—Robert A. Baker METHANE GENERATION RECOVERY FROM LANDFILLS—EMCON Associates... 

Mesuere et al. [99] and Gerringa et al. [100] have reviewed methods for the determination of copper in soils. Residual copper(II) complexes have been determined in soil by electron spin resonance spectroscopy. Fast neutron activation analysis has been studied [101] as a screening technique for copper and (zinc) in waste soils. Experiments were conducted in a sealed tube neutron generator and a germanium y-ray detector. 

Fast neutron activation analysis has been studied as a screening technique for zinc (and copper) in waste soils [247]. Experiments were conducted in a sealed tube neutron generator and a germanium X-ray detector. 

Vogt, J. R., and W. D. Ehmann An Automated Procedure for the Determination of Oxygen Using Fast Neutron Activation Analysis Oxygen in Stony Meteorites. Radiochim. Acta 4, 24 (1965). 

Volborth, A. Precise and Accurate Oxygen Determination by Fast Neutron Activation. Fortschr. Mineral. 43, 10 (1966). 

Broadhead, K. G., D. E. Shanks, and H. H. Heady Fast-Neutron Activation Analysis in Molten Salt Electrometallurgical Research. Modern Trends in Activation Analysis-Proceedings of the 1965 International Conference in College Station, Texas, April, 1965. A and M College of Texas, College Station, Texas, pp. 39—43 (1965). 

Wood, D. E., P. L. Jessen, and R. E. Wood Industrial Application of Fast Neutron Activation Analysis for Protein Content of Food Products. Paper presented at the 52nd Annual Meeting of the American Association of Cereal Chemists, Los Angeles, California, April, 1967. 

Gorski, L., W. Kusch, and J. Wojtkowska Fast Neutron Activation Analysis for Determination of Copper Content of Lower Silesian Copper Deposits. Talanta 11, 1135 (1964). 

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