Neutron activation analysis

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The neutron activation analysis (NAA) is a nuclear physical method for the quantitative analysis of the element or isotopic composition of even the smallest samples of all kinds that are irradiated with neutrons . The atomic nuclei to be determined ( analyte nuclei ) of the sample interact with the neutrons and, depending on the type of nuclear reaction, different products can arise. This process, which is carried out in a research reactor or with the help of another neutron source , is called neutron activation . The resulting activation products can be radioactive and then decay with their characteristic half-life . With activation as well as with decay, radiation with likewise characteristic energies is released, which is used for analysis.


Time course of the activity of an indicator nuclide formed in a sample irradiated with neutrons.

The neutron activation analysis usually takes place in four phases.


Thermal neutrons are most commonly used for activation. Most target cores have favorable capture cross-sections for neutrons in this energy range and therefore provide a well-measurable yield of activation products. But it can also be activated by means of epithermal or fast neutrons.


The duration of the decay phase can be used to control whether activation products with long or short half-lives are preferred. In many cases, spectral interferences can be excluded by a suitable choice of activation and decay times.

Measurement phase

A gamma spectrum of the irradiated sample is recorded using gamma spectrometry . The type of activation products present can be read from the position of the peak-shaped signals in the gamma spectrogram. The level of the signals is related to the amount. The initial amount of analyte can be deduced from an internal standard or a calibration series.

Analysis phase

The information obtained is then analyzed using a computer and converted into graphs using mathematical algorithms.


There are several variants of neutron activation analysis:

  • Prompt gamma activation analysis (PG-NAA or PGAA): Here, the energies of the so-called prompt gamma quanta released when the neutrons are absorbed into the atomic nucleus are determined and their relative intensities are measured. For this purpose, special measuring stations are required that allow simultaneous neutron irradiation and gamma ray measurement.
  • Instrumental Neutron Activation Analysis (INAA): The classic non-destructive neutron activation analysis, in which the activity of the radionuclides generated is measured. This method allows activation in one reactor and subsequent analysis in another location.
  • Radiochemical neutron activation analysis (RNAA): Here a chemical separation takes place before or after the irradiation. This excludes the activity of other elements from the measurement. The method is therefore very sensitive to isotopes of low concentration.
  • Delayed neutron activation analysis (. DnaA engl delayed ): Measurement of delayed neutrons that are released by a nuclear reaction of the still excited nuclei. The method is used particularly for the analysis of fissile material.

Importance and efficiency

The neutron activation analysis, which developed from 1951 after the Americans Taylor, Havens and Anderson began to use gamma radiation to analyze trace elements, allows the quantitative determination of elements in very different sample materials, some of which would require considerable effort to break down (rocks, alloys ), or whose destruction would be undesirable (archaeological artifacts and works of art). The latter has the advantage that the NAA can make do with the smallest sample quantities. For many elements (e.g. gold and arsenic ), tiny traces can be detected. The excellent performance of neutron activation analysis is also due to the fact that sample preparation (with the associated risk of contamination) is not absolutely necessary.

Paintings can also be examined using neutron autoradiography , a variant of neutron activation analysis. Recently, this method has been used successfully in the examination of several works by old masters, such as Rembrandt'sSusanna in the Bath ” and “Portrait of a Man in Military Costume”, Titian's “Girl with the Fruit Bowl” and Vermeer'sYoung Lady with a Pearl Necklace ”.

The high level of instrumental effort is a disadvantage. The highest performance is only achieved with high neutron flux densities. A research reactor must be available for this. Smaller neutron sources are much easier to handle. For this, they are limited in their performance parameters, but are nevertheless suitable for many examinations. Another disadvantage is that, depending on the irradiation and composition of the sample, residual activity can be retained for a long time.

On a sample of Napoléon's hair , taken the day after his death (May 5, 1821), it was shown in 1961 by means of neutron activation analysis that he was gradually poisoned with arsenic . By analyzing a 13 cm long strand in sections, it was possible to show, according to the natural growth of the hair, that he was given arsenic intermittently during a one-year phase and at what times this happened. However, there are also doubts about this theory.

To investigate the Bouchard murder in Canada, nuclear scientists first used the neutron activation analysis method in forensics, comparing a single hair in the hand of the girl Gaetane Bouchard, who was killed in 1958, with that of her murderer, the fishing tackle dealer John Jakob Vollman. The pioneer in the field of this NAA application was the Canadian chemist Robert E. Jervis (* 1927 in Toronto), who carried out numerous hair comparisons with his student Auseklis K. Perkons from 1958 at the University of Toronto. At around the same time, Vincent P. Guinn, head of the Activation Analysis Program at General Atomics in the USA, carried out forensic trace investigations into paint, glass, car rubber, powder, plastic materials, grease and wood using neutron activation analysis. In the Pamela Mason murder case (1964), Jervis was also invited as an expert for the NAA analyzes carried out by chemists Michael Hoffman and Maynard Pro.

In archeology , the NAA is mainly used to determine the origin of raw materials, in particular to compare ceramic products with local clay deposits.

Neutron activation analysis with pulsed 14 MeV neutrons to characterize radioactive waste

The product control of radioactive waste poses a particular challenge. Radioactive waste products are usually incinerated, pressed and then conditioned in 200l steel drums in cemented form. The common method of product control includes a purely radiological measurement of radionuclides using so-called gamma scanners. Non-radioactive substances and elements cannot be recorded in this way. In order to record non-radioactive and chemotoxic elements and to be able to compare them with the storage conditions of the corresponding repository, a drill core extraction with subsequent wet chemical analysis is carried out. In addition to radioactive secondary waste, this also means radiation exposure for operating and analysis personnel. Furthermore, the drilling core extraction is not representative, especially for highly heterogeneous, material compositions. Against this background, a research program was launched at the research center in Jülich in 2007 to develop a non-destructive, representative analysis method for radioactive and non-radioactive substances and elements. This method is based on the neutron activation analysis with pulsed 14 MeV neutrons. In contrast to the classic neutron activation analysis with thermal neutrons (E = 25 meV neutrons), which are mostly extracted from a reactor, the use of fast neutrons (E = 14 MeV neutrons) opens up new possibilities in the material characterization of small and large-volume samples. The penetration depth of fast neutrons in matter is significantly higher than thermal neutrons due to the lower probability of interaction. The material characterization is of particular interest for product control of radioactive waste. Nevertheless, this method can be used as PGAA, INAA or as DNAA for large-volume samples (bulk goods, industrial products, etc.).

First successes in the qualitative and quantitative characterization of homogeneous 25l and 50l concrete samples could be achieved by means of a pulsed 14 MeV neutron source (neutron generator) in combination with the PGAA.

For the qualitative and quantitative characterization of large-volume homogeneous concrete samples (200l concrete samples) for the material characterization of radioactive waste in 200l drums, pulsed 14 MeV neutrons can also be used successfully in combination with the PGAA. This method also makes it possible to identify and quantify locally concentrated elements (cadmium sheet) in homogeneous, large-volume concrete samples.

In connection with the characterization of radioactive waste by means of neutron activation analysis, further progress could be achieved. This makes it possible to qualitatively and quantitatively characterize heterogeneous radioactive waste from a mixture of concrete and polyethylene by means of pulsed 14 MeV and the combination of PGAA and DNAA. The pulsed neutron emission by means of a neutron generator also enables a time-resolved recording of prompt and delayed gamma spectra, from which, for example, the death rate (so-called die-away time) of thermal neutrons can be derived. This method also allows the identification and quantification of locally concentrated elements such as a cadmium sheet for heterogeneous mixed samples made of concrete and polyethylene.


  • Georg Schwedt : Analytical chemistry. Thieme Verlag, Stuttgart 1995, ISBN 3-527-31206-4 , pp. 280-286.
  • K. Cammann (Ed.): Instrumental Analytical Chemistry. Spektrum Akademischer Verlag, Heidelberg / Berlin 2001, ISBN 3-8274-0057-0 , pp. 4-91 to 4-101.
  • C.-O. Fischer, C. Laurenze-Landsberg W. Leuther, K. Slusallek: Neutron autoradiography. In-depth analysis of the image, physical basics, technical implementation. In: J. Kelch (Ed.): Pictures in focus: The man with the gold helmet. Berlin 1986, DNB 870087533 , pp. 38-47.
  • Jürgen Thorwald : The hour of the detectives. Becomes and worlds of criminology. Droemer Knaur, Zurich / Munich 1966, DNB 576679402 , pp. 483-537.

Web links

Individual evidence

  1. Jürgen Thorwald : The hour of the detectives. Becomes and worlds of criminology. Droemer Knaur, Zurich / Munich 1966, p. 498.
  2. neutron autoradiography at ColourLex
  3. ^ Matthias Alfeld, Claudia Laurenze-Landsberg, Andrea Denker, Koen Janssens, Petria Noble: Neutron activation autoradiography and scanning macro-XRF of Rembrandt van Rijn's Susanna and the Elders (Gemäldegalerie Berlin): a comparison of two methods for imaging of historical paintings with elemental contrast. In: Appl. Phys. A. Volume 119, No. 3, 2015, pp. 795-805, doi: 10.1007 / s00339-015-9081-8 .
  4. Karen Trentelman, Koen Janssens, Geert van der Snickt, Yvonne Szafran, Anne T. Woollett, Joris Dik: Rembrandt's An Old Man in Military Costume: the underlying image re-Examined. In: Applied Physics A. Volume 121, No. 3, November 2015, pp. 801-811, doi: 10.1007 / s00339-015-9426-3 .
  5. C.-O. Fischer, J. Kelch, C. Laurenze-Landsberg, W. Leuther, C. Schmidt, K. Slusallek: News on neutron activation autoradiography. Titian's "Girl with a Fruit Bowl" and the use of Naples yellow. In: Restauro. Volume 6, No. 105, 1999, pp. 426-431.
  6. ^ C. Laurenze-Landsberg: Neutron-Autoradiography of Two Paintings by Jan Vermeer in the Gemäldegalerie Berlin. In: W. Lefèvre: Inside the Camera Obscura - Optics and Art under the Spell of the Projected Image. (= Preprint. 333). Berlin 2007, DNB 985810726 , pp. 211-225.
  7. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
  8. Friedrich Scherer, Steffi Schöbel: The End of Napoleon - Was the Emperor Poisoned? ( Memento of April 5, 2003 in the Internet Archive ) March 6, 2002.
  9. Jürgen Thorwald : The hour of the detectives. Becomes and worlds of criminology. Droemer Knaur, Zurich / Munich 1966.
  10. Hans Mommsen et al: Neutron Activation Analysis of Pottery from Naucratis and Other Related Vessels. In: Udo Schlotzhauer, Alexandra Villing: Naukratis. Greek Diversity in Egypt. Studies on East Greek Pottery and Exchange in the Eastern Mediterranean. London 2006, ISBN 0-86159-162-6 , p. 69.
  11. Meral Akurgal et al. (Ed.): Pottery centers of the East Aegean. Archaeometric and archaeological investigations on Mycenaean, geometric and archaic ceramics from sites in western Asia Minor (= supplementary books to the annual books of the Austrian Archaeological Institute. Book 3). Vienna 2002, ISBN 3-900305-39-0 , pp. 11–24.
  12. Kettler, John Paul Hermann: Prompt gamma neutron activation analysis for the non-destructive characterization of radioactive waste . In: Forschungszentrum Jülich GmbH (Ed.): Energy & Environment . tape 82 . Research Center, Central Library, Jülich 2010, ISBN 978-3-89336-665-1 , p. 230 (Zugl .: Aachen, Techn. Hochsch., Diss., 2010).
  13. Havenith, Andreas Wilhelm: Material characterization of radioactive waste products by a multi-element analysis method based on the instrumental neutron activation analysis - MEDINA - . In: Forschungszentrum Jülich GmbH (Ed.): Energy & Environment . tape 248 . Forschungszentrum Jülich, Jülich 2015, ISBN 978-3-95806-033-3 , p. 311 (Zugl .: Aachen, Techn. Hochsch., Diss., 2014).
  14. Frank Mildenberger: Neutron activation analysis with pulsed 14 MeV neutrons to characterize heterogeneous radioactive waste . In: Forschungszentrum Jülich GmbH (Ed.): Energy & Environment . tape 395 . Forschungszentrum Jülich, Jülich 2017, ISBN 978-3-95806-271-9 , p. 128 (Dissertation, RWTH Aachen University, 2017).