Since the discovery in 1932, neutrons became a basis of many methods used not
only in research, but also in industry and engineering. Among others, the
exceptional role in the modern nuclear engineering is played by the neutron
activation spectroscopy, based on the interaction of neutron flux with atomic
nuclei. In this article we shortly describe application of this method in
medicine and detection of hazardous substances.Comment: Presented at Symposium on applied nuclear physics and innovative
  technologies, Cracow, 03-06 June 201

Silarski, M.

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M. Silarski

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Acta Physica Polonica B Proceedings Supplement

Applications of Neutron Activation Spectroscopy

Since the discovery in 1932, neutrons became a basis of many methods used not only in research, but also in industry and engineering. Among others, the exceptional role in the modern nuclear engineering is played by the neutron activation spectroscopy, based on the interaction of neutron flux with atomic nuclei. In this article, we shortly describe application of this method in medicine and detection of hazardous substances

Silarski, Michał

Jagiellonian Univeristy Repository

Vol. 6 (2013) Acta Physica Polonica B Proceedings Supplement No 4APPLICATIONS OF NEUTRON ACTIVATIONSPECTROSCOPY∗M. Silarskifor the SABAT Collaboration†The Marian Smoluchowski Institute of Physics, Jagiellonian UniversityReymonta 4, 30-059 Kraków, Poland(Received August 6, 2013)Since the discovery in 1932, neutrons became a basis of many methodsused not only in research, but also in industry and engineering. Amongothers, the exceptional role in the modern nuclear engineering is played bythe neutron activation spectroscopy, based on the interaction of neutronflux with atomic nuclei. In this article, we shortly describe application ofthis method in medicine and detection of hazardous substances.DOI:10.5506/APhysPolBSupp.6.1061PACS numbers: 82.80.Jp, 89.20.Dd1. IntroductionNeutrons have many properties that make them ideal for certain types ofapplications, especially concerning imaging and elemental traces detectiontechniques. As neutral particles, neutrons can deeply penetrate even verydense matter. On the other hand, they interact strongly with nuclei, what isa great advantage over e.g. X-rays which interact almost only with electronsin the matter, and thus are “blind” to the type of element.One of the most important technique being used widely in research andengineering for a long time, is the neutron radiography. As the name im-plies, a neutron beam penetrates the object to be studied. This beam isattenuated by the sample material depending on the neutron interactioncross sections. The beam is then detected by a two-dimensional imagingdevice that provides an image representing the macroscopic structure of the∗ Presented at the Symposium on Applied Nuclear Physics and Innovative Technolo-gies, Kraków, Poland, June 3–6, 2013.† The SABAT Collaboration: P. Moskal, M. Silarski, M. Smolis, S. Tadeja.(1061)1062 M. Silarskistudied sample [1, 2]. An example of radiographs taken with different meth-ods is presented in Fig. 1, where one can clearly see the differences betweenX-rays and neutrons. Analogously as for X-rays, a series of n-ray radio-graphs provides a three-dimensional image of the object inner structure,i.e. its tomographic picture. The sensitivity to light elements, especially tohydrogen, makes the n-ray radiography a very valuable alternative to theX-rays. It is used, for example, in studying the flow of oil in automobiletransmissions, monitoring complex piping systems and fluid flow, to deter-mine the pyrotechnic product quality and in many other applications [1].Fig. 1. Comparative radiographs of a cigarette case: (a) photograph, (b) neutronradiography, (c) X-rays radiography. The figure is adapted from [1].Passing through matter neutrons interact with nuclei in several processesincluding the elastic and inelastic scattering, neutron capture, fission or par-ticle emission from the nucleus. The inelastic scattering and neutron captureconstitute the base of the Neutron Activation Analysis techniques (NAA),which are widely used for the quantitative elemental concentrations determi-nation. These two types of neutron interaction result in the nuclei excitationturning them into radioactive nuclides, which decay emitting gamma rays.Their energies are characteristic for each element, so that the measurementof these gamma rays intensities gives information on the elemental contentof the irradiated object. Methods based on NAA have a big applicationpotential since they provide an analysis of a large number of elements simul-taneously and non-destructively. Moreover, they have a very low detectionlimits for many elements. Devices based on NAA are used widely in industry(e.g. crude oil and coal deposits identification, water monitoring), medicineand homeland security. The latter two applications will be discussed in moredetails in next sections of this contribution.Applications of Neutron Activation Spectroscopy 10632. Medicine: breast cancer diagnosticsThe presently used breast cancer diagnostic methods are based mainly onX-rays imaging (mammography), and have reached almost 98% sensitivityin detecting tumors [3]. However, mammography do not provide sufficientlyaccurate information which would allow to determine whether the tumor isbenign or malicious. Moreover, for confirmation of the diagnosis, one needsinvasive biopsy. The other disadvantage is that the radiologists working onthe interpretation of the mammography images need a long and expensivetraining before they are able to set a good diagnosis.Several studies have demonstrated that breast cancer is associated withchanges in the concentration of some elements (e.g. calcium, potassium oriron) in the malignant tissue at very early stages1. These changes oftenoccur much earlier than morphologic changes such as tumors and calcifica-tions. Thus, detection of these changes gives a chance to diagnose of breastcancer much earlier before the tumor grows large enough to be detectedby existing imaging techniques [4]. The NAA based techniques are idealto quantify the concentration of elements of interest in the tissue providingat, the same time, location of region affected by the disorder and diagno-sis [4]. Similar method, based on oxygen concentration measurement, isdeveloped by CALSEC [3]. It makes use of the fact that cancerous tumorschemically differ from healthy tissue by the oxygen content. Therefore, anyoxygen concentration difference between a tumor and the adjacent healthytissue indicates that it is malicious. This method is intended to support theconventional methods providing kind of “needleless biopsy”.Neutron based techniques for cancer diagnosis are at present at an ad-vanced stage of development and will be soon a very useful alternative orsupplement of mammography.3. Homeland security: detection of hazardous substancesIn the face of increasing danger of terrorist attacks and still growingtrade of illicit drugs, a development of new hazardous substances detectiontechnologies became of a great importance. At present, the detection ofconcealed contraband is based mainly on the X-rays, vapor detection andsniffer dogs. X-ray scanners suffer from the main disadvantage of having asmall cross section interaction with low electron density elements from whichorganic materials, including most explosives and illicit drugs, are composed.Thus, they are detected mainly through shape recognition, which could bevery difficult since the hazardous material can be molded or packed into any1 Changes of trace element concentrations in human tissue may be a precursor tomalignancy in several other organs such as brain or prostate [4].1064 M. Silarskiform [5]. In fact, up to now the false alarm rates in the airport luggageinspections amount almost to 100%. Also the vapor detection and snifferdog methods suffer from a high rate of false alarms, especially in the case ofpeople professionally working with explosives or drugs. These methods canbe used only for security purposes at airports, in the Civil Service etc. In themilitary application the only devices used, for example, for area demining aremetal detectors. In the ground full of metal remains this process becamevery expensive and time consuming. Moreover, the novel landmines arebeing made without any metal parts, thus they cannot be detected withthose devices.Neutron-based techniques were considered to be used in the hazardoussubstances detection for more than forty years, but the first functioningdevices were designed and produced at the beginning of 21st century byMaglich [6]. They utilize the fact, that most of the commonly used explo-sives, drugs or war gases are organic materials. Therefore, they are composedmostly of oxygen, carbon, hydrogen and nitrogen (see Table I). Thus, theseTABLE IMolecular content of few chosen hazardous substances.Substance Stoichiometric formula Ratio C:H:N:OTrinitrotoluene (TNT) C7H5N3O6 1.2 : 0.8 : 0.5 : 1Hexogen (RDX) C3H6N6O6 0.5 : 1 : 1 : 1Nitroglycerine C3H5N3O9 0.33 : 0.56 : 0.33 : 1Cocaine C17H21NO4 4.25 : 5.25 : 0.25 : 1Heroine C21H23NO5 4.2 : 4.6 : 0.2 : 1Amphetamine C9H21NO4 4.25 : 5.25 : 0.25 : 1substances can be unambiguously identified by the determination of the ra-tio between number of C, H, N and O atoms in a molecule, which can bedone non-invasively applying Neutron Activation Analysis techniques. Theschematic illustration of one of the possible practical realizations of a deviceutilizing this method is shown in Fig. 2. The suspected item can be irradi-ated with a flux of neutrons produced using compact generators based e.g.on deuteron–tritium fusion, where deuterons are accelerated to the energyof 0.1 MeV and hit a solid target containing tritium. As a result of thefusion, an alpha particle is created together with the neutron, which is emit-ted nearly isotropically with a well defined energy equal to about 14.1 MeV.Such energy is sufficient to excite nuclei of carbon 12C (4.43 MeV), oxygen16O (6.13 MeV) and nitrogen 14N (2.31 MeV and 5.11 MeV) [8]. γ quantafrom the de-exciting nuclei are then detected by a germanium detector pro-viding a very good energy resolution. Counting the number of gamma quantacorresponding to a given nuclei provides information about the stoichiome-Applications of Neutron Activation Spectroscopy 1065try of the examined item. Since the hydrogen nuclei cannot be excited byneutron inelastic scattering, the amount of hydrogen atoms in the samplecannot be examined using this method. Yet, hazardous substances can bediscriminated from non-hazardous by the atomic ratio of carbon, oxygenand nitrogen only. There are two major difficulties which have to be solvedin this type of detectors. One is an isotropic generation of neutrons whichinduces unfortunately a large background from irradiation of material sur-rounding the interrogated object. This noise can be significantly reducedby the requirement of the coincident detection of the alpha particle, whichallows for the neutron tagging by registration of the direction of alpha par-ticle [8]. Moreover, germanium detectors are quite expensive and need acooling system which significantly limit the mobility of the scanner. Thus,there has been done a lot of studies to replace germanium with detectorsystems based on scintillators.Fig. 2. Illustration of a system for hazardous substances detection based on neu-trons. The figure is adapted from [7].4. SummaryOver the last decade, technologies using fast neutrons have found usein a variety of contexts in the research, industry and engineering. Espe-cially, the Neutron Activation Analysis based techniques were found to bevery promising. They may find applications e.g. in remote and non-invasivedetection of explosives or drugs, as well as in medical diagnostics of cancertissues. Thus, they could open a new frontiers in homeland security andbiomedical sciences.1066 M. SilarskiThis work was supported by the Polish Ministry of Science and HigherEducation through grant No. K/DSC/000681 for the support of young re-searchers and Ph.D. students of the Department of Physics, Astronomy andApplied Computer Science of the Jagiellonian University.REFERENCES[1] McClellan Nuclear Research Center, Neutron Radiography,http://mnrcdev2.ucdavis.edu/radiography.html[2] N. Chankow, Neutron Radiography, Nondestructive Testing Methods andNew Applications, in: Nondestructive Testing Methods and NewApplications, M. Omar (Ed.), InTech, 2012,http://www.intechopen.com/books/nondestructive-testing-methods-and-new-applications/neutron-radiography[3] B.C. Maglich, Emergence of “Femtomedicine” — New Frontier of BiomedSciences,http://www.calseco.com/_docs/_released-docs/femtomedicine.pdf[4] A.J. Kapadia et al., IEEE Trans. Nucl. Sci. 55, 501 (2008).[5] A. Buffler, Rad. Phys. Chem. 71, 853 (2004).[6] B.C. Maglich, AIP Conf. Proc. 796, 431 (2005).[7] B.C. Maglich, Birth of Atometry –– Particle Physics Applied To SavingHuman Lives, presentation at conference LEAP 2005, Bonn–Jülich,Germany, http://www.fz-juelich.de/leap05/talks[8] P. Moskal, Ann. UMCS, Physica 66, 71 (2011).

Applications of neutron activation spectroscopy

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Applications of neutron activation spectroscopy

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