Prompt gamma neutron activation analysis

Prompt gamma neutron activation analysis is a process similar to INAA that was discussed in Section 3. While INAA uses the radioactivity emitted by the activation products for analysis, PGNAA uses the prompt gamma rays emitted during the neutron capture. 

PGNAA enjoys limited use because of the scarcity of suitable neutron beams. Typical applications are analysis of samples in geological and atmospheric sciences. The technique is useful for analysing for the following elements H, B, C, N, P, S, Cd, Pb, Sm, and Gd. 

PGNAA requires a neutron beam with a well collimated flux greater than 10 n cm s which illuminates a representative part of the sample (about 2 cm in diameter). 

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Z.B. Alfassi and C. Chung (eds), Prompt Gamma Neutron Activation Analysis, CRC Press, Boca Raton, FL (1995). 

Figure 2.13 Schematic diagram of the nuclear processes involved in neutron activation analysis. Prompt gamma neutron activation analysis (PGNAA) occurs within the reactor delayed gamma NAA (DGNAA) occurs at some remote site. (After Glascock, 1994 Fig. 1. John Wiley Sons Limited. Reproduced with permission.)...

The y particle is emitted virtually instantaneously on the capture of the neutron, and is known as a prompt y - it can be used analytically, in a technique known as prompt gamma neutron activation analysis (PGNAA), but only if such y s can be measured in the reactor during irradiation. Under the conditions normally used it would be lost within the nuclear reactor. In this reaction, no other prompt particle is emitted. The isotope of sodium formed (24Na) is radioactively unstable, decaying by beta emission to the element magnesium (the product nucleus in Figure 2.13), as follows ... 

Prompt gamma neutron activation analysis (PGNAA)... 

TNPGNAA thermal neutron prompt gamma neutron activation analysis TOF-MS time of flight mass spectrometry toxicokinetics study of the quantitative action of a poison in an organism over a period of time, especially the processes of absorption, distribution, biotrans formation and excretion... 

Many facilities use a prompt gamma neutron activation analysis (PGNAA) system to measure boron in blood samples although there are other methods. 

Figure 1. Histogram of detection limits for neutron activation analysis (NAA) and neutron-capture prompt gamma-ray activation analysis (PGAA). Data from Reference 15.

Neutron-capture prompt-gamma ray activation analysis (PGAA) is a recent addition to the nuclear analytical arsenal. In this technique the instantaneous gamma ray emission from a sample is measured as it is irradiated in a flux of reactor neutrons (33,3, 35). Because the sample must be several meters from either the core of the reactor or (less commonly) from the detector, the sensitivity of this technique is generally poorer than in conventional NAA. However, it is possible to measure small quantities of many elements which do not give radioactive neutron-capture products, notably 0.01 mg of H, 50 ng B, and 1 mg P in an electronics context. 

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... 

Glascock, M.D., Spalding, T. G., Biers, J. C., and Corman, M.F. (1984). Analysis of copper-based metallic artefacts by prompt gamma-ray neutron activation analysis. Archaeometry 26 96-103. 

The most utilized methods include X-ray fluorescence (XRF), atomic absorption spectroscopy (AAS), activation analysis (AA), optical emission spectroscopy (OES) and inductively coupled plasma (ICP), mass spectroscopy (MS). Less frequently used techniques include ion-selective electrode (ISE), proton induced X-ray emission (PIXE), and ion chromatography (IC). In different laboratories each of these methods may be practiced by using one of several optional approaches or techniques. For instance, activation analysis may involve conventional thermal neutron activation analyses, fast neutron activation analysis, photon activation analysis, prompt gamma activation analysis, or activation analysis with radio chemical separations. X-ray fluorescence options include both wave-length and/or energy dispersive techniques. Atomic absorption spectroscopy options include both conventional flame and flameless graphite tube techniques. 

Instrumental neutron activation analysis (thermal, INAA epithermal, EINAA, prompt gamma PGNAA) (INAA)... 

Some relevant terms for activation analysis are activation analysis, neutron activation analysis (NAA), instrumental neutron activation analysis (INAA), neutron activation analysis with radiochemical separation (RNAA), photon activation, neutron capture prompt gamma activation analysis (PGAA), charged particle activation, autoradiography, liquid scintillation counting, nuclear microprobe analysis, radiocarbon (and other element) dating, radioimmunoassay, nuclear track technique, other nuclear and radiochemical methods. Briefly, the salient features of some of the more popular techniques are as follows ... 

Two elemental analyzer systems have been developed, the "Continuous On-line Nuclear Assay of Coal", CONAC, (Science Application, Inc., Palo Alto, CA) and "The Elemental Analyzer" (MDH Industries, Inc., Monrovia, CA). Both of these units are based upon the measurement of prompt gamma rays that are emitted from a nucleus following the capture of a neutron. This technique is commonly known as prompt neutron activation analysis, PNAA. 

Neutron activation analysis (NAA) is the general term used to describe a nuclear-based technique in which a solid or liquid sample is irradiated with neutrons. Capture or absorption of a neutron excites the nuclide that returns (promptly or after a delay) to ground state by emission of an energetic photon (gamma ray) and/or other particles from the nucleus (Figure 1.20). 

The safe and verifiable disposition, either by incineration or chemical neutralization of chemical warfare (CW) agents requires correct a priori identification of each munition or container to be processed. A variety of NDE techniques have been used or tested for the examination and characterization of munitions.[l,2] In the U.S., three widely used techniques are X-ray radiography, acoustic resonance spectroscopy (ARS), and prompt gamma ray neutron activation analysis (PINS). The technical bases, instrumental implementations, and applications of the U.S. versions of these methods are briefly discussed. 

A conveiuent suite of NDE techniques is available for the characterization of muiution fill. Large numbers of similar stockpile munitions can be reliably and quickly classified using Acoustic Resonance Spectroscopy (ARS). Measurement times are about one minute per item. However, ARS measurements require a comparison template and are less usefiil for assay of old, rusted, and one of a kind munitions. For munitions of this type, x-ray radiography and assay by prompt gamma ray neutron activation analysis can reliably determine the munition fill, and ensure that the items are properly scheduled for destruction. 

Neutron activation analysis (NAA) can be accomplished by measurement of the prompt gamma rays during irradiation or by measurement of the delayed... 

With respect to the time of measurement, NAA falls into two categories (1) prompt gamma-ray neutron activation analysis (PGNAA), where measurements take place during irradiation, or (2) delayed gamma-ray neutron activation analysis (DGNAA), where the measurements follow radioactive decay. The latter operational mode is more common. 

PGNAA Prompt gamma-ray neutron activation analysis... 

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